U.S. patent application number 15/214728 was filed with the patent office on 2016-11-10 for porous pavement for water quality and quantity management.
The applicant listed for this patent is Unit Process Technologies, LLC. Invention is credited to John J. Sansalone.
Application Number | 20160326699 15/214728 |
Document ID | / |
Family ID | 35798982 |
Filed Date | 2016-11-10 |
United States Patent
Application |
20160326699 |
Kind Code |
A1 |
Sansalone; John J. |
November 10, 2016 |
Porous Pavement for Water Quality and Quantity Management
Abstract
A sorptive-filtration system for removing at least one of
negatively or positively charged ions, complexes or particulates
from an aqueous stream. The system includes a) flow formed
substantially from at least one of rainfall-runoff or
snowmelt-runoff; b) a filter containment communicating with the
runoff stream such that at least part of the stream passes through
the filter containment; and c) a granular filter media disposed
within the filter containment, the filter media having an
amphoteric material applied thereto, wherein the amphoteric
material comprises a metal selected from at least one of Fe, Al,
Mn, or Si.
Inventors: |
Sansalone; John J.;
(Gainesville, FL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Unit Process Technologies, LLC |
Gainesville |
FL |
US |
|
|
Family ID: |
35798982 |
Appl. No.: |
15/214728 |
Filed: |
July 20, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14318119 |
Jun 27, 2014 |
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15214728 |
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13957984 |
Aug 2, 2013 |
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14318119 |
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13667907 |
Nov 2, 2012 |
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13957984 |
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13426227 |
Mar 21, 2012 |
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13667907 |
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12430712 |
Apr 27, 2009 |
8162562 |
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13426227 |
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11843485 |
Aug 22, 2007 |
7524422 |
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12430712 |
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11218677 |
Sep 2, 2005 |
7341661 |
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11843485 |
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10842328 |
May 10, 2004 |
7575393 |
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11218677 |
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09916171 |
Jul 26, 2001 |
6767160 |
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10842328 |
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09714366 |
Nov 16, 2000 |
6468942 |
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09916171 |
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PCT/US04/28342 |
Sep 1, 2004 |
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11218677 |
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10842328 |
May 10, 2004 |
7575393 |
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12430712 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01J 20/28028 20130101;
B01D 2239/0618 20130101; B01J 20/3042 20130101; B01D 39/163
20130101; C02F 1/004 20130101; B01D 2239/0613 20130101; B01J
20/3028 20130101; B01D 39/2093 20130101; B01J 20/12 20130101; B01D
39/2017 20130101; B01J 20/28004 20130101; E01C 2201/20 20130101;
B01D 2239/1241 20130101; B01J 20/3236 20130101; B01D 2239/1208
20130101; B01J 2220/58 20130101; B01J 20/3085 20130101; B01J
20/28057 20130101; B01D 2239/065 20130101; C02F 1/288 20130101;
B01D 39/18 20130101; B01J 20/28033 20130101; B01J 20/3289 20130101;
E01C 7/142 20130101; B01J 20/08 20130101; B01J 20/0222 20130101;
B01J 20/321 20130101; B01J 20/3078 20130101; B01D 15/00 20130101;
B01J 20/28011 20130101; B01D 39/2072 20130101; E01C 9/00 20130101;
B01J 20/3204 20130101; C02F 1/281 20130101; B01D 2239/0681
20130101; E03F 5/0404 20130101; B01J 2220/4806 20130101; B01D
2239/1291 20130101; B01D 2239/0478 20130101; B01J 20/06 20130101;
B01J 20/103 20130101; C02F 2103/001 20130101; B01D 39/06 20130101;
B01D 2239/0407 20130101; B01D 2239/1258 20130101; B01J 2220/42
20130101; B01J 20/10 20130101; B01J 20/3214 20130101; B01J 20/0229
20130101; E03F 1/00 20130101; B01D 39/12 20130101; B01D 39/2027
20130101; B01D 2239/0485 20130101; B01J 20/2803 20130101 |
International
Class: |
E01C 7/14 20060101
E01C007/14; C02F 1/28 20060101 C02F001/28; B01D 15/00 20060101
B01D015/00; B01D 39/06 20060101 B01D039/06; B01D 39/12 20060101
B01D039/12; E01C 9/00 20060101 E01C009/00; B01J 20/10 20060101
B01J020/10; B01J 20/08 20060101 B01J020/08; B01J 20/02 20060101
B01J020/02; B01J 20/12 20060101 B01J020/12; B01J 20/28 20060101
B01J020/28; B01J 20/32 20060101 B01J020/32; C02F 1/00 20060101
C02F001/00; B01D 39/20 20060101 B01D039/20 |
Claims
1. A sorptive-filtration system for removing at least one of
negatively or positively charged ions, complexes or particulates
from an aqueous stream, comprising: a. flow formed substantially
from at least one of rainfall-runoff or snowmelt-runoff; b. a
filter containment communicating with said flow such that at least
part of said flow passes through said filter containment; and c. a
granular filter media disposed within said filter containment, said
filter media comprising an amphoteric material applied thereto,
wherein said amphoteric material comprises a metal selected from at
least one of Al, Mn, or Si.
2. The filtration system of claim 1, wherein said amphoteric
material is at least one oxide of a metal selected from at least
one of Al, Mn, or Si.
3. The filtration system of claim 1, wherein said filter media is a
granular media having a porosity of between about 0.2 and about
0.7.
4. The filtration system of claim 1, wherein said amphoteric
material comprises both an oxide of Si and at least one oxide of a
metal selected from at least one of Al, Mn, or Fe.
5. The filtration system of claim 4, wherein said filter media
comprises a first media having a Si oxide applied thereto and a
second media having at least one oxide of at least one of Al, Mn,
or Fe.
6. The filtration system of claim 1, wherein said filter
containment is formed by a porous textile or geotextile
material.
7. The filtration system of claim 1, wherein said filter
containment is formed by a porous mesh material.
8. The filtration system of claim 7 wherein said porous mesh
material is a wire mesh.
9. The filtration system of claim 1, wherein said filter system
includes a rigid media housing and said filter containment is a
flexible material generally shaped to fit within said media
housing.
10. The filtration system of claim 3, wherein said filter media is
a granular media having a hydraulic conductivity of between about
1.0 and about 0.0001 cm/sec.
11. The filtration system of claim 1, wherein said media has a
specific gravity of between about 0.2 and about 1.0.
12. The filtration system of claim 1, wherein said media has a
specific gravity of between about 0.2 and about 1.0.
13. The filtration system of claim 1, wherein said media comprises
a granular substrate having an average diameter ranging from 0.1 mm
to 100 mm.
14. The filtration system of claim 1, wherein said granular media
is produced by a process comprising the steps of: a. providing said
granular media; b. applying an amphoteric solution to said media;
c. drying said media to leave an amphoteric coating thereon.
15. The filtration system of claim 14, wherein said step of
applying said amphoteric solution is accomplished by at least one
of: i) immersing said media in said amphoteric solution; ii)
spraying said amphoteric solution onto said media; or iii) adding
an amphoteric solution to a precursor of said media.
16. The filtration system of claim 1, wherein said media is a
granular media produced by a process comprising the steps of: a.
providing said granular media; b. providing a wet cement mix
comprising in part an amphoteric solution; c. coating said media
with said wet cement mix; and d. hydrating or drying said wet
cement mix on said substrate.
17. The filtration system of claim 16, wherein said media has a
specific gravity of between about 0.2 and about 1.0
18. The filtration system of claim 16, wherein said media has a
specific gravity of between about 1.0 and about 2.4.
19. The filtration system of claim 1, wherein said granular media
is produced by a process comprising the steps of: a. providing said
granular media substrate; b. coating said media with a wet cement
mix; c. drying said wet cement mix on said substrate; and d.
applying an amphoteric solution to said cement coated
substrate.
20. The filtration system of claim 1, wherein said granular media
is produced by a process comprising the steps of: a. providing a
wet cement mix comprising in part an amphoteric solution; b. drying
said wet cement mix; and c. reducing said dried cement mix into
granular form ranging from about 0.01 mm to about 500 mm in average
diameter.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 14/318,119, filed on Jun. 27, 2014, which is a continuation of
U.S. application Ser. No. 13/957,984, filed on Aug. 2, 2013, which
is a continuation of U.S. application Ser. No. 13/667,907, filed on
Nov. 2, 2012, which is a continuation of U.S. application Ser. No.
13/426,227, filed on Mar. 21, 2012, which application is a
continuation of U.S. application Ser. No. 12/430,712 filed on Apr.
27, 2009, which application is a continuation of U.S. application
Ser. No. 11/843,485, filed on Aug. 22, 2007, which application is a
continuation of U.S. application Ser. No. 11/218,677, filed on Sep.
2, 2005, which application is a continuation-in-part of Ser. No.
10/842,328, filed May 10, 2004, which is a divisional application
of Ser. No. 09/916,171, filed on Jul. 26, 2001, which is a
divisional application of Ser. No. 09/714,366, filed on Nov. 16,
2000. U.S. application Ser. No. 11/218,677 is also a
continuation-in-part of serial number PCT/USO4/28342 filed Sep. 1,
2004. U.S. application Ser. No. 12/430,712, filed on Apr. 27, 2009
is also a continuation-in-part of Ser. No. 10/842,328, filed May
10, 2004. This application incorporates by reference all above
applications in their entirety.
BACKGROUND OF INVENTION
[0002] 1. Technical Field
[0003] The present invention relates to the removal of cationic,
anionic, complexed or particulate contaminants from liquids and
gases. In particular, certain embodiments relate to particle
clarification and sorptive-filtration by media which removes
chemical constituents and particulates in a liquid or gas passed
through the media.
[0004] 2. Background Art
[0005] An area of increasing concern in the environmental sciences
and engineering, particularly process control is the treatment or
control of species that represent an environmental, ecological,
human or process concern. Common examples include metal species and
phases such as for metal elements Cd, Cu, Zn, Ni, Pb, As, Ag, V,
and Cr, as well as non-metal species and phases such as for
constituents phosphorus and nitrogen species which become water
borne and are carried by urban and rural rainfall-runoff and
snow-snowmelt (herein identified as "runoff") to drainage systems
(herein identified as "drainage") receiving waters, water supplies,
and to natural and anthropogenic terrestrial interfaces such as
soils, the subsurface or earthen deposits. As used herein, ions or
complexes being "water borne" means being transported in water in
any manner, whether the ionic or complexed form is in solution, as
a precipitate material, or is transported by water through a
particulate bond or physical-chemical or biological attachment to a
particle, in the form of a surface complex or a colloidal bond, or
carried by the advective or diffusive transfer of water. Common
manners in which such species and phases become water borne is
through leaching, dissolution or particulate-bound entrainment by
runoff from surfaces of the built or constructed environment, for
example paved surfaces, or from human activities such as industry,
manufacturing and agriculture. These species and phases are
typically deposited on urban surfaces such as constructed surface,
open surfaces, soil surfaces, and paved surfaces though vehicle
exhaust, fluid leakage, vehicular wear, pavement degradation,
particulate deposition, litter, illicit discharges, downspout
discharges and pavement maintenance. These species and phases are
typically deposited on earthen or soil surfaces through
agricultural processes such as fertilization, pesticide
application, insecticide application, and soil amending and
land-disturbing practices such as earthwork, grading, cut/fill
excavation and surficial as well as deep soil modifications.
Subsequent hydrologic precipitation results in the mass transfer of
these species or phases either in ionic, complexed or
particulate-bound forms and transports these species and phases in
surface or subsurface flows by advective, diffusive, gravitational,
chemical or electromagnetic gradients.
[0006] The particulate and colloidal matter (herein identified as
"particulates) itself can be deleterious, representing an
environmental, ecological, human or process concern that requires
control. In this application, "particulate-bound" means any bond,
precipitate or complex associated with particulate material that
ranges in size from colloidal (<1 .mu.m) to suspended
(1.about.25 .mu.m) to settleable (.about.2-.about.75 .mu.m) to
sediment (.about.75 to 4750 .mu.m) larger gross solids or debris
(>75 .mu.m) or floatable material. While the size limits of each
class of particulate matter are approximate because of properties
such as specific gravity and geometry, taken in total these classes
represent the entire size gradation found in surface runoff,
drainage or subsurface flow. The ionic fractions can be quite
variable. For example, metals such as Zn in certain source area
urban watershed locations under conditions of acid rain can be
greater than 80% dissolved (f.sub.d=0.8); while in other watershed
or in lower locations of the same watershed, the f.sub.d for Zn can
be as low as 0.2. The remaining percentage is largely
particulate-bound but may be a complexed aqueous species. However,
in the simplest two-phase model if the dissolved fraction is 0.8
then the particulate fraction for Zn is 0.2. This 0.2 will then
distribute across the particulate size gradation as a function
particle indices such as surface charge, surface area, mass and
number gradation, composition of particle and contact time.
[0007] It is desirable to intercept the runoff or drainage and
remove these species, phases or particulates prior to allowing the
water to continue to drainage areas, water supply areas, through
the subsurface or in a down-gradient transport to a sea or ocean.
One method of separating the water borne species whether in
dissolved ionic, complexed, precipitate or particulate-bound forms
is to pass the water through a media or medium that functions to
provide a range of mechanisms from surface complexation, ion
exchange, adsorption, absorption or precipitation (herein
collectively; identified as "sorption") and also provides a range
of mechanisms such as interception, sedimentation, impaction,
straining, adhesion or physical-chemical-biological sorption of
particulate matter (herein collectively identified as
"filtration"). Such a media or medium is identified as providing
sorptive-filtration.
[0008] One of the most common media for removing particulate bound
metals from water is sand and sometimes perlite. However, sand has
very little capacity for removal of dissolved or complexed species
and therefore, is generally not considered effective in removing
these species. A common media used for drinking water is granular
activated carbon (GAC) and has long used as a media for removing
dissolved organic species and also been used for species such as
metals. However, for many cationic species GAC has relatively
little sorptive capacity and rapid breakthrough occurs and thus,
sorbed metals must frequently be removed or the GAC "recharged."
Also, GAC has low compressive strength and cannot support vertical,
lateral or shear loads. Any application which places such loads on
the GAC material may cause crushing, significant deformation and a
greatly reduce sorptive-filtration capacity and impair physical
characteristics of the GAC and the sorptive-filtration system.
Similarly earthen materials such as natural perlite or modified
perlite have been used for filtration and/or sorption. However
perlite itself also has lower strength and loading characteristics
and lower sorptive capacity for many metals and non-metals such as
phosphorus.
[0009] A much more recently developed sorbent media is iron oxide
coated sand (IOCS). IOCS is formed by coating silica sand with a
thin layer of iron oxide and it has been shown to be an effective
sorbent media for cationic species such as metals or anionic
species such as phosphorus, in part dependent on the pH and point
of zero charge (pzc) of the surface coating. Iron oxides and
hydroxides possess little or no permanent surface charge, but will
take on a positive or negative surface charge in the presence of
protons or hydroxyl ions. In other words, depending on the pH of
the solution in which the iron oxide is place, the iron oxide may
take on a net positive or negative charge. A substance which
exhibits a net positive or negative charge depending on the pH
level may be referred to as an "amphoteric" substance.
[0010] Iron oxide typically has a smaller net charge (either
positive or negative) in a pH range of approximately 7 to 8. When
the pH rises above approximately 8, the iron oxide becomes more
negatively charged. Thus, positively charged cations will engage in
a sorption reaction with the iron oxide surface or
suspended/colloidal particulates with or without bound metal or
non-metal species and borne by water passing over the negatively
charged iron oxide will tend to bond to the iron oxide and be
filtered from the water. Conversely, if the pH falls below
approximately 7, the iron oxide becomes positively charged and is
less likely to bond with cationic species, but will bond with
anionic species or complexes. The pH at which the net surface
charge of a particle is zero is denominated the point of zero
charge or "pzc".
[0011] One major disadvantage of IOCS, coated on an unprepared
substrate surface is that the oxide coating is not sufficiently
durable. For example, the comparatively smooth surface of sand
particles tends to result in the oxide coating flaking off.
Attempts to avoid this flaking have led to time consuming sand
preparation efforts such as cleaning the sand of organics or weak
surface coatings and applying a scratch surface to the sand before
applying the oxide coating. However, even with these preparation
efforts, IOCS still exhibits flaking and thus a reduction in oxide
coating durability. The smooth surface of the sand is also
disadvantageous from the standpoint of providing a comparatively
low specific surface area (SSA) for bonding. The specific surface
area of a material is generally defined as the surface area per
unit mass with the typical unit being m.sup.2/gm. As used herein,
specific surface area means the total area on the surface of the
material in addition to any available porous internal surface area
(such as for the GAC discussed above). The greater the surface area
of the substrate, the greater the surface area of oxide coating
that will be exposed to water borne metals. Thus, it is desirable
to provide a substrate with a relatively large SSA not withstanding
other design constraints. For example the SSA of rounded silica
sand is approximately 0.05 to 0.1 m.sup.2/gm.
[0012] Another problem found with IOCS is the tendency of the oxide
coating to crystallize. When the coating crystallizes, the crystals
set up a morphology which does not result in the highest surface
area of the coating. The surface area of the coating is much more
optimal if the oxide molecules are randomly distributed in a
non-lattice or "amorphous" fashion. For example, the SSA of IOCS
may approach 85 m.sup.2/gm if a method of sufficiently inhibiting
crystallization could be provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a diagram of an upflow filter.
[0014] FIG. 2 is a chart of surface charge versus pH for certain
amphoteric compounds.
[0015] FIG. 3 is a chart of aggregate distribution.
[0016] FIG. 4 is a cross-section of a roadway.
[0017] FIG. 5A is a filter system having multiple layers of
different amphoteric media positioned therein.
[0018] FIG. 5B is a filter system formed of a fixed matrix media
having two different layers of amphoteric material.
[0019] FIG. 5C is a filter system having a containment of media in
a filter housing.
[0020] FIGS. 6A and 6B are different views of an alternative filter
system having a containment of media in a filter housing.
[0021] FIGS. 7A and 7B are filter systems having media containments
positioned on down spout drains or similar types of drains.
[0022] FIGS. 8A-8C are filters illustrating different manners of
containing a granular media.
DETAILED DESCRIPTION OF THE INVENTION
[0023] The filtering media or medium of the present invention
generally comprises a sorptive-filtration media or medium. The term
"filter media" or "media" means any substrate used for filtration
whether in the form of granular particles, a fixed porous matrix,
or any other form which may accomplish the objects described in
this application. The media maybe sorptive in that it may include a
substrate with an amphoteric substance or compound applied to,
coated upon, or bonded to the substrate to produce a high specific
surface area media capable of sorbing (i.e. the physico-chemical
capture of) dissolved, ionic, complexed or particulate-bound
contaminants or particles. The media may also have a filtration
characteristic which relies on the physical (or physical-chemical)
capture of contaminants which are larger than the specific openings
in the pore spaces in the media or medium.
[0024] In one embodiment, the liquid (or gas) to be treated will be
passed through a granular or a fixed medium incorporated as part of
a unit operation and process (UOP) or as a separate UOP that forms
part of a treatment or modification system for liquids (or gases).
In particular, certain embodiments relate to removal of metal
species and phosphorus species either in aqueous ionic forms, as
aqueous complexes, as particulate-bound or colloidal-bound species;
and as precipitates.
[0025] In another general embodiment, the invention includes a
granular substrate with an amphoteric substance applied thereto in
the presence of a crystal inhibiting agent (for select substances
or combination of amphoteric substances the explicit or additional
use of a crystal inhibiting agent is not required). The granular
substrate could be sand or any other granular substrate such as
crushed limestone, crushed concrete, or other granular substrates
such as polymeric beads (or other shapes), natural substances, or
modified substances such as perlite. In another general embodiment,
the present invention includes all substrates having a specific
surface area of 0.1 m.sup.2/gm or greater and having an amphoteric
substance applied to the substrate. In these latter embodiments
with a substrate having an SSA of greater than 0.1 m.sup.2/gm, the
substrate could include a wide variety of materials such as precast
cementitious porous pavement (CPP) discussed herein (one form of
which having an SSA of 5-10 m.sup.2/gm), wood chips, recycled
concrete chips, recycled concrete pavement rubble, fired clay or
silt material, cemented clays or silts, perlite, zeolites, natural
aggregates, synthetic aggregates, polymeric compounds, granular
activated carbon (one form of which having an SSA of 600-1300
m.sup.2/gm) etc. The amphoteric substance of the present invention
is intended to include any substance or compound having amphoteric
properties or which exhibit amphoteric properties when in an
aqueous environment. Certain embodiments of the amphoteric
substance include compounds such as oxides of iron, manganese,
aluminum, or silicon. Certain non-limiting examples of amphoteric
substances, e.g. for iron, include the more common mineral forms
identified in table 1, or the various mineral forms of manganese,
aluminum, silicon or combinations thereof of these four.
Non-limiting examples of manganese forms may include Pyrolusite,
Ramsdellite, Nsutite, Hollandite, Cryptomelane, Coronadite,
Romanechite, Todorokite, Birnessite, Vernadite, Rancieite,
Buserite, Lithiophorite, Manganite, Hausmannite. Aluminum is
typically listed as classes of aluminum oxides, hydroxides and
orthohydroxides (although there are many polymorphs for aluminum).
Some common mineral forms are gibbsite, bayerite, boehmite, and
diaspore. Some forms of silicon are silica, quartz, cristobalite,
tridymite, and opal.
[0026] In some embodiments, an amphoteric solution is formed by
dissolving a salt of iron, manganese, aluminum, or silicon (or any
combination of these) in a solute. The substrate is then exposed to
this solution by immersing, spraying, or other application. The
liquid is volatized in a drying process to leave behind a metal
oxide bonded to the substrate. Typically any remaining component of
the metal salt (e.g., nitrate, sulfate, or chloride) is readily
washed off the substrate leaving predominantly the metal oxide.
Although in many embodiments the amphoteric substance will be at
least one oxide of either Al, Mn, Fe, or Si, the amphoteric
substance may include other combinations of forms of Al, Mn, Fe, or
Si which exhibit similar amphoteric properties when applied to the
substrate, regardless of the manner of application.
[0027] In regards to iron oxide compounds, there are at least 13
iron oxide minerals, of which there are 8 major iron oxides. These
iron oxides differ in composition, the valence state of Fe and in
crystalline structure. However, all iron oxides contain Fe and O or
OH. Table 1 summarizes the major iron oxides with selected
characteristics.
TABLE-US-00001 TABLE 1 Selected properties and attributes of major
iron oxide minerals Mineral Structural Density SSA Name Formula
system (g/cm.sup.3) (m.sup.2/g) Color Hematite
.alpha.-Fe.sub.2O.sub.3 Trigonal 5.26 20-30 blood red Maghemite
.gamma.-Fe.sub.2O.sub.3 Cubic or tetragonal 4.87 80-130 Chocolate
Magnetite Fe.sub.3O.sub.4 Cubic 5.18 ~4 black Goethite
.alpha.-FeOOH Orthorhombic 4.26 20-40 mustard Lepidocrocite
.gamma.-FeOOH Orthorhombic 4.09 70-80 Orange- brown
Ferrihydrite.sup.1 5Fe.sub.2O.sub.3.cndot.9H.sub.2O.sup.2 Trigonal
3.96 180-300 deep brown Feroxyhyte .delta.'-FeOOH Hexagonal 4.20
190-210 Brown Akaganeite .beta.-FeOOH Tetragonal 3.56 ~30 dark
mustard .sup.1ferrihydrite & feroxyhyte have the only amorphous
or poorly-crystalline structures low SSA from
Fe(NO.sub.3).sub.39H.sub.2O hydrolysis, high SSA from Fe.sup.3+
precipitation with KOH .sup.2other formulas include:
Fe.sub.5HO.sub.8.cndot.4H.sub.2O and Fe.sub.6(O.sub.4H.sub.3).sub.3
point of zero charge (pzc) for all minerals shown is between pH 7-8
.alpha.: hexagonal close packed (more stable than .gamma.) .beta.:
goethite polymorph in presence of high Cl.sup.-levels .gamma.:
cubic close packed .delta.': poorly-ordered ferromagnetic form of
FeOOH
[0028] From Table 1 it can be seen that the more amorphous
ferrihydrite or feroxyhyte are the forms of iron oxide with the
highest SSA. If these forms are coated onto silica sand, their
higher SSA, as compared to say the more crystalline hematite, will
create a more preferable sorbent media. For this reason, a one
embodiment of the amphoteric compound focuses on the use of these
forms, specifically ferrihydrite. Those skilled in the art will
understand that ferrihydrite is not produced in isolation, but is
typically formed in a solution having various other iron oxide
compounds. The ferrihydrite may transform into other, more
crystalline iron oxide compounds (such as hematite or goethite)
depending on factors such as temperature, pH, and whether the iron
source is ferric or ferrous ions. To inhibit such transformation to
the more crystalline compounds, inhibiting agents such as silica
(SiO.sub.2), silica fume or silica gel, inorganic compounds such as
phosphates, polymeric compounds whether naturally occurring (e.g.
natural organic matter in soil) or synthetic (e.g. polyethylene),
sodium hydroxide, oils, grease, or any other substance which
inhibits crystallization, may be introduced in certain embodiments
of the process for synthesizing ferrihydrite or applying the iron
oxide coating. In certain embodiments where sand is the substrate,
a highly acidic compound, such as ferric nitrate or ferric chloride
(used to form the amphoteric compound as described below) may
dissolve silica off the sand substrate, thereby producing an
inhibiting agent. Because so many substances may act as inhibiting
agents, it is possible that certain impurities in the materials
selected (such as grease or oil in a sand substrate) can be
engineered to act as a sufficient inhibiting agent without the
addition of further inhibiting agents. While typically advantageous
to use an inhibiting compound with iron oxides, it may not be
necessary when the amphoteric compound is an oxide of manganese,
aluminum, or silicon. However, the use of an inhibiting agent with
the latter compounds is within the scope of the present
invention.
[0029] Two known methods for producing ferrihydrite follow. The
first method involves preheating 2000 mL of DI water to 75.degree.
C. in an oven and then withdrawing the water and adding 20 g of
unhydrolyzed crystals of Fe(NO.sub.3).sub.3.9H.sub.2O. The solution
is stirred rapidly and reheated at 75.degree. C. for 10 to 12
minutes. The formation of iron hydroxy polymers will change the
solution from a dull gold color to dark reddish brown. The solution
is then dialyzed for three days to produce approximately 5 g of
ferrihydrite. This procedure produces a ferrihydrite of lower SSA,
in the range of 180 to 200 m.sup.2/g.
[0030] A second method involves dissolution of 40 g of
Fe(NO.sub.3).sub.3.9H.sub.2O in 500 mL of DI water and addition of
approximately 330 mL of 1M KOH until the pH is 7 to 8 while
stirring the solution. This procedure produces a ferrihydrite of
higher SSA, in the range of 200 to 300 m.sup.2/g. The solution is
then centrifuged and dialyzed to produce approximately 10 g of
ferrihydrite. While both of these procedures work well for a small
mass of ferrihydrite (i.e. 10 g) in a laboratory environment, they
are not easily adapted to be economically feasible at production or
field scale levels that require tons of such a coating. Rather, the
above methods would require design and construction of a
plant-sized process to produce multiple tons of ferrihydrite.
[0031] Another embodiment of the present invention includes
another, more economical method for producing sufficient quantities
of ferrihydrite. In this method, the source of ferric ions is
either Fe(NO.sub.3).sub.3.9H.sub.2O, (ferric nitrate (FN)) or
FeCl.sub.3, (ferric chloride (FC)). Both FN and FC are available as
reagent-grade salts or available commercially in larger quantities
as bulk solutions. FC has the additional advantage of being more
economical and being a by-product of pickling waste. When FN or FC
are dissolved in potable water to produce an approximately 1M to
approximately 3M solution, the resulting iron oxides in the
solution will typically be approximately 50% ferrihydrite and 50%
other iron oxides.
[0032] One substrate to which a coating of amphoteric compound may
be adhered is sand. Sand typically has a comparatively low SSA of
about 0.05 to about 0.10 m.sup.2/gm. Moreover, this low SSA is
indicative of a relatively smooth surface to which iron oxide
coatings will have difficulty adhering. As discussed above, without
some agent to inhibit crystallization of the iron oxide coating,
the SSA may remain in the range of 1 to 5 m.sup.2/gm. Two examples
of producing a sand substrate filtration media with a markedly
improved SSA (about 5-20 m.sup.2/gm) by subjecting conventional
sand to a multi-step process are as follows.
[0033] In the first example, the sand was first cleaned and tumbled
in acidic solution (of a pH<2), rinsed with DI water, and then
cleaned and tumbled in a very dilute basic solution before a final
rinse is made. Second, to promote bonding, an initial scratch coat
applied by immersing the sand in an approximately 1M FN solution.
The sand was then heat at about 100 degrees C. until this coating
was dry and then the sand was disaggregated and rinsed in DI water
to remove any loose coating. After this rinsing, the sand was
reheated until dry and then cooled. Third, the sand was immersed in
another solution of 1.6 M FN. In this solution, 1,000 ppm SiO.sub.2
was added (in the range of 1% of the aqueous volume) to help
inhibit the transformation of ferrihydrite to hematite or possibly
to goethite. Fourth, the sand was again dried with drying times
minimized in order not to promote the transformation to hematite
due to dehydration. However, drying of the sand at high
temperatures could also lead to thermal transformation of
ferrihydrite to hematite. It was determined that drying could take
place at an acceptably fast rate at 100.degree. C. if an inhibitor
such as SiO.sub.2 was used to prevent crystalline bonds from
forming. Once drying was complete, the sand was allowed to cool and
the coated media was disaggregated. As a final step, the media was
pH conditioned to a neutral pH by passing DI water at a pH of 8 to
9 (raised with NaOH or a similar base) through the media until the
pH of the effluent was between 7.5 and 8, above the point of zero
charge for iron oxides. This also removed any loose iron coating.
It is noted that the above mentioned scratch coating is necessary
because the granular substrate was sand which has a relatively
smooth surface. However, other granular substrates such as crushed
limestone have a sufficiently rough surface that a scratch coat is
not required.
[0034] The second example is provided by a larger-scale field
production. The above method is scaled up by using a larger
gasoline-powered concrete mixer and a gas-fired heater. A 3.0 M
ferric chloride (FC) solution containing 1000 ppm silica solution
was prepared in sufficient volume such that the sand could be
completely immersed. Thereafter, heat was applied via the gas-fired
heater to evaporate the liquid and attach the iron to the sand
surface. Typically greater efforts must be made to insure dryness
of the FC treated sand as opposed to the FN treated sand since FC
is significantly more hydroscopic than FN. This method proved
feasible to produce the required 9 tons of OCS necessary for a
related experiment.
[0035] For each batch, approximately 90 pounds of filter sand was
placed in the concrete mixer with an excess of ferric chloride
solution. The amount of ferric chloride solution put into the
mixture was enough to just cover the filter sand. The mixture was
stirred vigorously and heat applied by the a gas-fired heater. The
gas-fired heater was directed into the mouth of the concrete mixer.
The slurry was continuously stirred by the concrete mixture until
the sand was completely dry. Typical drying time for each batch was
3 hours.
[0036] Once dry, the sand was poured from the concrete mixer into a
backhoe bucket and placed in a tandem dump truck for cooling. In
preparation for pH neutralization, complete drying of the sand was
essential to ensure the iron coating would not be removed by the
sodium hydroxide in the pH neutralization process. If the sand is
not completely dry, the iron coating washes off easily when put
into the NaOH solution.
[0037] Since the sand was placed in a tandem dump truck for
cooling, it decided to neutralize the entire truckload at once to
reduced handling of the OCS. The dump truck full of OCS was parked
facing down a slope and a solution (of approximately 10 lbs. of
NaOH per 55 gallons of potable water) was poured into the truck bed
on top of the OCS. The idea was to create a bathtub effect to
neutralize the sand. The truck bed did leak but the level of the
solution was kept above the depth of the sand with continual
addition of NaOH solution. Leakage of the truck bed proved
beneficial due to the continual addition of new solution to replace
loss. The new solution was more capable of neutralizing the OCS
while the used solution was removed from the system. The pH was
checked with a pH probe at several depths in the truck bed to
ensure complete neutralization. Approximately 10 tons of OCS was
produced, the largest known quantity of such material. In the above
process, the inhibiting agents were formed by the impurities found
in the mixer, the gas-fired heater, NaOH and the construction
process in the field to such a degree that it was not necessary to
add additional silica as an inhibiting agent.
[0038] Another embodiment deals with substrates having a specific
gravity of less than 1.0. There are a large number of likely
substrates having an specific gravity of less than 1.0. One family
of such substrates is wood, with pine having by way of example a
specific gravity of about 0.35. Another family of such substrates
is polymeric compounds. Polymeric compounds may include light
weight materials such as foam packing pellets (e.g., polystyrene),
which would form a granular media having a specific gravity of
approximately 0.2. Polymeric compounds could also include heavier
polymers having a specific gravity of up to 0.97. Polymeric
compounds could also include polymer-type materials which have
similar weight, flexibility, and long molecular chains. Of the
polymer family, it has been found that polyethylene (PE) or
polypropylene (PP) have many characteristics making them suitable
substrates for the present invention. PE and PP have a specific
gravity of about 0.9. It is believed PE, PP, and other similar
polymeric compounds are particularly useful when in the form of
polymeric floating media filter beads. Normally, polymer beads will
have a specific gravity ranging between approximately 0.50 and
0.95. One simple example of a "filter" or "clarifier" using
floating polyethylene beads can be seen in FIG. 1. In the
embodiment of FIG. 1, the filter is a cylindrical geometry upflow
filter, but the filter could utilize many geometries and flow
directions depending on constraints such as media type, coating,
specific gravity and design intentions. Filters using floating
polyethylene beads are usually upflow filters such as seen in FIG.
1, but can be downflow filters and have a variety of geometric
shapes. In FIG. 1, the upflow filter 10 is filled with floating
polymeric beads 12. An influent flow 13 flows into filter 10,
through beads 12 (where it has pollution constituents adsorbed and
filtered), and exits as effluent 14. While not explicitly shown in
FIG. 1, the upflow filter 10 could utilize any number of methods
well known in the art for backwashing the beads. Upflow filters
have the advantages of being easily backwashed to prevent clogging
and are less likely to hydraulically "short-circuited" (i.e. water
cutting an uninterrupted fluid path through the beads and not
having to flow around the individual beads). It has been found that
allowing a layer of sediment to form at the base of the filter
media may actually enhance filtration as long as the layer does not
become so thick that the layer significantly inhibits design flows.
The filter media would be backwashed at the point design flows were
significantly inhibited. It is also very practical to direct water
through an upflow or downflow filter when the water is being
drained from a elevated grade (such as a highway overpass or an
elevated interstate). A media bed formed of a granular material
such as sand, polymer beads, or other granular materials will have
a given porosity. In one embodiment, this porosity will be between
about 0.1 and about 0.6 while in another embodiment the porosity
will be between about 0.2 and about 0.5. However, the present
invention includes larger porosity ranges and any sub-range between
about 0.1 and about 0.6.
[0039] The present invention encompasses virtually any filtration
system where a contaminant containing aqueous stream is passed
through media having some type of amphoteric coating applied
thereto. In one embodiment, the contaminant containing aqueous
stream is formed substantially of urban runoff. The sources of
"urban runoff" as used herein means an aqueous stream from diffuse
sources such as rainfall runoff or snow melt and point source
overflows such as sewer overflows, wherein the stream in directed
through an open drainage system (as opposed to a closed drainage
system such as a sanitary sewer). In one embodiment, the
contaminants are phosphorus and/or metal ions, complexes or
particulates and the media is coated with an oxide of aluminum,
iron, manganese, or silicon. The contaminants could be negatively
or positively charged ions or complexes or particles. In another
embodiment, the media is coated through a process where a crystal
inhibiting compound is added. Preferably, the crystal inhibiting
compound raise the SSA of the coated substrate to at least 5 or 10
m.sup.2/g and more preferably to at least 20 m.sup.2/g.
[0040] As used herein, "coating" or "coated onto" means a film
formed on the substrate. The film need not cover the entire
substrate, but where it does cover the substrate, the coating is
"cohesive" and "adhesive". This is distinguished from a series of
discrete particles spread on a surface, but not being cohesive.
Normally, a coating will cover a significant part of the substrate.
If the substrate has internal surface area, the amphoteric
substance will form a film on the internal surface area of the
media substrate. This film also need not cover the entire internal
surface area of the substrate, but where it does cover the
internals surface area, the film is cohesive and adhesive.
[0041] One preferred method of applying the amphoteric compound to
the polyethylene is similar to that used to apply iron oxide to
sand and is as follows. A 0.5 to 5 molar solution of FN or FC
(preferably about 1.6M) is prepared by dissolving the FC or FN in
water. The polyethylene beads are placed in the solution and
continuously stirred. The polyethylene should remain in the
solution a sufficient time for the entire surface area of the
polyethylene to become coated with iron oxide. An hour should be
sufficient period of time under most circumstances. The water is
then evaporated from the solution containing the polyethylene at a
temperature of approximately 90.degree. C.-95.degree. C. The drying
may take place at lower temperatures, but will unnecessarily slow
the drying process. Drying at higher temperatures is possible, but
may be undesirable from the standpoint of the polyethylene becoming
excessively plastic at temperatures above 95.degree. C. and
crystallization of the iron oxide becoming more prevalent at higher
temperatures.
[0042] One favorable characteristic of employing polyethylene as a
substrate is that polyethylene has an inherent tendency to inhibit
the crystallization of the iron oxide. This is believed to occur by
way of polyethylene molecules detaching from the substrate surface
and becoming lodged in the iron oxide molecules depositing on the
substrate surface. As alluded to above, this disruption of a
uniform iron oxide lattice tends to create a favorable, amorphous
(thus high specific surface area) coating of iron oxide. In
addition to taking advantage of the natural crystallization
inhibiting character of polyethylene, when using an iron oxide as
the amphoteric compound, it may also be desirable to further add an
inhibitor such as the 1000 ppm SiO.sub.2 solution discussed above.
The amount of SiO.sub.2 solution may vary, but an amount equal to
1% or less of the aqueous volume is normally considered sufficient.
If manganese oxide is the amphoteric compound, it usually may not
be necessary to add an inhibiting agent to achieve an acceptable
SSA. Significantly, it has been found that polymeric beads having a
specific gravity of about 0.9 maintain a specific gravity of less
than 1 (and therefore float) even after being coated. The coating
generally raises the bead's specific gravity to about 0.95.
[0043] While the above procedure described applying an amphoteric
compound to polyethylene beads, it will be understood that the
procedure could be carried out numerous other polymeric materials.
For example, an amphoteric compound could be applied to simple
packing material, cheap polymeric woven and non-woven material,
geosynthetics, polystyrenes and expanded foams as well. The foams
have to be dried at a lower temperature so they do not melt, so for
the case of expanded foams or heat sensitive polymerics, manganese
coatings are preferable to iron coatings (which require higher
temperatures to dry).
[0044] As mentioned above, another family of amphoteric substances
are formed from manganese, aluminum or silicon. There are a whole
series of manganese oxide minerals that can be produced that have
useful characteristics as media coatings for the treatment of storm
water and other waste streams containing dissolved ionic species,
complexed species and particulate-bound species such as heavy
metals. However, two manganese oxides groups comprise embodiments
for use with the present invention because their combination of
negative surface charge (measured as units of charge per surface
area) at nearly all environmental pH values and because of their
high specific surface area. This results in a coated media surface
with a high surface density of negatively charged sites for
adsorption of heavy metals. These two manganese oxides are
birnessite (whose structure is not completely understood, but is
believed to be in part a layered (MnO.sub.6) structure and
cryptomelane, (.alpha.-MnO.sub.2) which is a tunnel structure. Both
are different manganese oxide minerals having different structures.
Although not as critical as with iron oxides, some inhibition of
crystallization may be helpful to produce poorly crystalline
structures and higher surface area.
[0045] The point of zero charge (pzc) of manganese oxides and their
surface charge density may in some cases provide advantages of
manganese oxide coatings over iron oxide coatings in the adsorption
of heavy metals. Iron oxide coatings only have a negative charge on
their surface when the pH of the solution surrounding the media is
greater than the pzc of the coating. For pure iron oxides
crystalline minerals, this ranges from 7 to 8 depending on the
mineral form of iron oxide (i.e. goethite, hematite, etc.) and is a
comparatively narrow range. For silica-inhibited ferrihydrite this
pzc can be between pH values of 5.5 to 7.5. For manganese oxides
the pzc values are much lower. The pzc occurs at a pH of less than
5 Reported values of the pure mineral forms are in the range of 2
to 3. FIG. 2 illustrates the pzc for the manganese oxides
Birnessite and Cryptomelane and the iron oxide Goethite. Thus, for
manganese oxide coated media there is a strong negative charge at
typical environmental pH levels of 6 to 8. This also means that pH
conditioning such as rinsing with DI water is usually not necessary
for manganese oxide coated substrates.
[0046] Those skilled in the art will recognize there are numerous
methods of producing manganese oxides, aluminum oxides or silicon
oxides for use in the present invention. The following two methods
disclose example methods of the present invention for producing
both birnessite and crypotmelane.
Birnessite Coating Method (BCM).
[0047] The disclosed birnessite coating method uses a wet oxidation
procedure to precipitate the colloid of birnessite on the media
surface. In other words, a solution containing manganese was
oxidized to create a MnO.sub.x form. Two moles of concentrated
hydrochloric acid (37.5%) were added dropwise and continuously to a
boiling solution of 0.5-M potassium permanganate in 1 liter of
water, to which 0.5 liters of media was added, immersed and
vigorously stirred. The media actually used included plastic beads,
sand, GAC, concrete blocks and concrete rubble. However, any other
suitable media (wood, etc.) could also be used. After boiling for
10 minutes further, the media was washed with water and dried at
room temperature overnight. Under lab conditions, a reasonably pure
form of birnessite can be produced (>80% pure). This produced a
coating having a surface area of 70-90 m.sup.2/g (i.e. surface area
of coat as applied to the substrate) with a pzc at a pH near 3. At
environmental pH values the surface charge density is very negative
(-10 to -20 micromoles/m.sup.2). This coating has an approximate
mean of about 1200 micromoles of negative charge per gram of
coating.
Cryptomelane Coating Method (CCM).
[0048] The Cryptomelane coating method uses a wet oxidation
procedure to precipitate the colloid of cryptomelane on the media
surface. A solution of 0.35 moles KMnO.sub.4 in 800 ml of water is
heated to 60.degree. C. and dropwise continuously added into a
solution 0.5 moles of MnSO.sub.4 in one liter of 2M acetic acid.
This solution was heated with 500 ml filtration media (such as acid
washed polyethylene beads or any of the media types named above) to
80.degree. C. while vigorously stirring. After stirring for 15
minutes, the media was removed, filtered, washed with water and
allowed to dry at room temperature overnight. Under lab conditions
a reasonably pure form of cryptomelane can be produced (>80%
pure). This will produce a coating having a surface area of 200 to
270 m.sup.2/g (i.e. the surface area of the coating itself rather
than applied to the substrate as above) with a pzc at a pH near 3
to 4. At environmental pH values the surface charge density is
negative (-2 to -5 micromoles/m.sup.2). This coating has an
approximate mean of about 823 micromoles of negative charge per
gram of coating.
[0049] It will be understood that one factor is the combination of
specific surface area and surface charge. The difference between
1200 and 823 may be important when these coatings are applied
consistently as with a chemical process operation. It should be
noted that at the upper end of environmental pH values,
ferrihydrite (iron oxide) has a surface area of between 200 and 300
m.sup.2/g and a surface charge density of -0.1 to 1.0
micromoles/m.sup.2. Silicate (a form of silica) contamination
(addition of silica solution or natural silica in clay minerals),
tends to prevent ferrihydrite from transforming to other iron
oxides and thus tends to keep the pzc at a pH of around 5.5 to 7.5,
as is typical for ferrihydrite. This coating has an approximate
mean of about 113 micromoles of negative charge per gram of
coating. However, the cost of an iron oxide coating is
approximately 1/10 to 1/5 of a manganese coating. This cost does
not include the cost of pH conditioning of the influent for iron
oxides which can be significant for engineered systems.
[0050] Those skilled in the art will recognize that there is a
variety of synthetic manganese oxide minerals as there is with iron
oxide minerals. However, manganese oxides have not been as well
studied as iron oxides. Technically, the term "birnessite" is used
to refer to a group of manganese oxides for which the exact
structures are still to a certain extent unknown. What is known is
that these birnessite minerals are layered structures. Examples of
birnessite minerals having a valence >+4 are vernadite,
ranciete, buserite, and lithiophorite. Examples of birnessite
minerals with a valence <+4 are magnetite and hausmannite. The
other manganese oxides are tunnel structures. One of the more
common is cryptomelane which forms a group of manganese oxides
along with hollandite and coronadite (all having
.A-inverted.-MnO.sub.2 structures with a large foreign cation (K,
Ba or Pb respectively) as part of the structure). Other minerals
include ramsdellite (.E-backward.-MnO.sub.2), Nsutite
(.DELTA.-MnO.sub.2), romanechite (MnO.sub.6) and todorokite. All of
these minerals have negative surface charges and have SSA's that
fall in the range of 50 to 280 m.sup.2/g. Birnessite and
cryptomelane are easy to produce and provide a good combination of
negative surface charge and SSA for adsorption of cationic species
(mainly heavy metals) when the pH is above the pzc (see FIG. 2).
Naturally, it will be understood that altering the pH to above the
pzc will facilitate removal of cationic species while altering the
pH to below the pzc will allow the removal of anionic species such
as nitrite (NOD, nitrate (NO.sub.3.sup.-), or (PO.sub.4.sup.-).
[0051] It will be recognized the choice between iron oxide and
manganese oxide present a typical design choice which will be
governed by the particular engineering problem being addressed.
Additionally, different concentrations of the metal oxides have
been used in the solutions in which the substrate is immersed. The
concentrations may range from 0.1 M to 3.0 M (or higher) solutions
of the metal oxide. Nor is the invention limited to immersing the
substrate in a metal oxide solution. Rather, the oxide solution
could be an aerosol which is spayed onto the substrate. This
technique works well in a reactor that fluidizes the media using a
gas such as air. The oxide coating is injected as a fine spray onto
the fluidized media. Once the media is coated, the temperature in
the reactor would be raised to evaporate off the water and leave
the oxide coating on the media. The media will continue to be
fluidized throughout this process. The reactor can be as simple as
an upflow column or a conical upflow reactor. A significant
advantage of this technique is the savings created by the efficient
use of the coating material.
[0052] Still further amphoteric compounds within the scope of the
present invention are oxides of silicon, particularly as SiO.sub.2
or "silica." Silica has a point of zero charge (pzc) at a pH
ranging between about 2 to 4 depending upon the mineralogy and
morphology of the silica. Thus, silica carries a strong negative
charge at neutral pH. Specific surface areas of silica range
between 10 and 300 m.sup.2/g and can be substantially greater
depending on the particle size and morphology of the silica,
reaching 1000 m.sup.2/g or higher. When silica is applied as a
surface coating, the surface morphology is far less dense than for
silica sand, whose surface has been significantly abraded. This is
why a silica coating may have a very high specific surface area
while silica sand has a very low specific surface area. A silica
coating may be formed on various substrates in manners similar to
those mentioned above in regards to oxides of aluminum, iron, and
manganese. For example, the substrate could be immersed in an about
0.1 M to about 5.0 M solution of sodium silicate and then the
substrate heated to dryness in order to form the silica coating.
Naturally, many compounds other than sodium silicate could be
employed, non-limiting examples being calcium silicate or pure
silica. Additionally, higher specific surface areas may be achieved
by techniques such as applying the silica solution to the media as
an aerosol spray at elevated temperatures (e.g. 100.degree. C. or
higher).
[0053] Although not as common as iron oxides or manganese oxides,
aluminum oxides may also be a viable oxide coating, especially on
materials such as CPP. The chemistry of aluminum oxide indicates
that it should be a viable material and the cost of this material
is relatively low. Therefore, aluminum oxides (such as forms of
Al.sub.2O.sub.3) or aluminum salts such as aluminum nitrate used to
make amphoteric coatings or admixtures are intended to come within
the scope of the present invention. Methods of preparation from
aluminum salts are similar to iron discussed above.
[0054] The advantage of various alternative embodiments of the
present invention will become apparent as those skilled in the art
begin to practice the invention. For example, using cementitious
porous pavement (CPP, discussed below) as the filter media or
coating substrate allows a unique manner of avoiding the cost of pH
conditioning of the influent. As is well known, cement is largely
composed of alkalinity-producing substances and therefore is
capable of pH elevation. One method is to coat only the bottom 80%
of a CPP pavement block with iron, manganese, silicon or aluminum
oxide or combination thereof. Then, as pavement runoff percolates
down through the upper exposed cementitious material near the
pavement surface, the pH of the percolating runoff will be elevated
above the pzc of the oxide coating on the lower half of the CPP
block and thus, the lower 80% of the CPP block form an efficient
passive fixed sorption matrix.
[0055] Those skilled in the art will recognize many design issues
which apply to the choice of substrates or filter media. As
discussed above, the media may be many materials such as sand,
polymeric media, clay, pumice, perlite or a fixed porous matrix
such as cementitious porous pavement (CPP). Typically, the prior
art is only concerned with making cementitious structures (e.g.
pavement) as impervious to water as possible. However, one aspect
of the present invention is creating a cementitious material which
is quite porous either as a pavement material or as a media
substrate. A wide range of size and gradation of material may be
used as media and CPP blocks may be used in their block form or
broken up to serve as a rubble or discrete media substrates. Issues
such as contact time, contact surface area, filtration ability,
porosity, stress-strain characteristics, pore characteristics,
durability and hydraulic conductivity required will determine the
choice of media substrate or rubble size. Any of the above
described amphoteric coating preparation techniques may be applied
to CPP material either as the material is being produced (described
below) or after the material has been produced without a coating
(in large or small blocks or as sections). If the CPP material is
not produced with the amphoteric compound as an admixture (defined
below), the block of material will be immersed in the amphoteric
coating solution of choice and the solution is circulated through
and around the CPP block. Because of contact time issues, one
preferred method requires the intact CPP blocks to remain in the
circulating Fe, Mn, Al or Si salt or oxide solution or combinations
thereof for approximately 60 minutes before removing and elevated
temperature and/or forced convective drying. Drying may also take
place at room temperature for several days under still air
conditions or for 24 hours when air is being blown by both sides of
the block. Alternatively, the porous block could be sprayed with an
oxide coating, allowed to dry at ambient or elevated temperature,
and then be used. As used herein, a media having an amphoteric
substance "applied" thereto includes coating (e.g., by spaying,
soaking, or immersing) the media; having the amphoteric compound
added while producing the media (e.g., as an admixture); or any
other method of combining the amphoteric substance with the media.
An "admixture" for the cementitious material (either CPP pavement
or CPP as media) for the particular embodiments described herein
may be defined as an amphoteric substance (for example a metal salt
or metal oxide) other than the primary components (e.g., water,
aggregate, cement) of cement-based materials such as concrete,
where the amphoteric substance is added to the mix design before or
during the mixing process of the primary components to produce
desired modification to the properties and behavior of the CPP
pavement or media. The admixture is distinguished from applying a
layer, film or coating of an amphoteric substance in that
application of such a layer, film or coating onto CPP pavement or
media is carried out after some degree of hydration (curing) has
occurred.
[0056] The CPP should be sufficiently porous to allow migration of
water through the pore space, but retain sufficient strength to
withstand vehicle wheel loads typically encountered by pavement
systems that carry vehicular, animal or human traffic; for example
road-side shoulders, roadways, parking areas, driveways or
sidewalks. One measure of the ability of CPP to allow the migration
of water is saturated hydraulic conductivity (K.sub.sat) measured
in cm/sec. In one embodiment, the hydraulic conductivity of the CPP
could range between about 1.0 and about 0.0001 cm/sec or in another
embodiment between about 0.1 and 0.001 cm/sec or about 0.1 and 0.01
cm/sec. A still further embodiment has a hydraulic conductivity of
about 0.01 cm/sec. While there may be situations where a very high
hydraulic conductivity is desirable, this must be balance against
concerns with sufficient structural strength and sufficient surface
area contact time between the pavement and the fluid flowing
through it to insure mass transfer and/or filtration by the
pavement. The factors affecting the porosity of the CPP are the
water to cement ratio, cement to aggregate ratio, whether and how
much pressure is applied during curing, aggregate gradation,
aggregate moisture content, and to a lesser degree, the amount of
fine aggregate in the mix.
[0057] It will be understood that CCP having a hydraulic
conductivity as described above will also have a certain total
porosity. Total porosity (or simply "porosity") may be defined as
the ratio of pore volume in a material to the total volume of the
material. In one embodiment, the CCP described above will have a
porosity of between approximately 0.1 and 0.6, while another
embodiment has a porosity of between approximately 0.2 and
approximately 0.4. Other embodiments may include any porosity
sub-range between approximately 0.1 and approximately 0.7.
[0058] While there are many mixtures which would form the CPP of
the present invention, three preferred mixtures are disclosed below
in Table 1. The water cement ratio for each mix design is varied,
ranging from 0.14 to 0.32. However, these water cement ratios were
used in conjunction with steam curing as described below. Those
skilled in the art will recognize that if steam curing is not used,
the chosen water cement ratio would be higher, up to a water cement
ratio of 1. Nevertheless, to maintain a hydraulic conductivity of
between 1.0 and 0.0001 cm/sec., it is suggested that the water
cement ratio be maintained below 1, although a water-cement ratio
of greater than 1 is not excluded from the present invention. When
CPP is used as a cast-in-place material (i.e. not steam cured and
cured at ambient temperature and pressure) a water cement ratio of
about 0.3 to about 0.4 with wetted aggregate would be one possible
range.
[0059] Typically, the ratio of fine to course aggregates will be
approximately 1 to 1. While this ratio could vary, an excessive
amount of fines may tend to reduce porosity by filling passages in
the cement structure and reducing the fine aggregate will result in
larger pore openings. As an illustrative sample, the grain size
distribution of the pea gravel and sand used in Batch 2 is
presented in FIG. 3.
TABLE-US-00002 TABLE 2 Mix Designs for Porous Pavement Block
Component Batch 1 Batch 2 Batch 3 Cement 109 kg 109 kg 109 kg (Type
II) (240 lbs) (240 lbs) (240 lbs) Water 15-20 kg 20-25 kg 30-35 kg
Coarse 472 kg 381 kg 431 kg Sand (1040 lbs) (840 lbs) (950 lbs) # 9
Gravel 336 kg -- -- (740 lbs) Pea -- 381 kg 331 kg (840 lbs) (730
lbs) -- Indicates material not used in batch
[0060] The pavement resulting from the disclosed mixes was formed
in various sizes of precast blocks, for example 24 inches.times.16
inches.times.4 inches thick. Naturally, this should by no means be
considered an optimal size, but rather dimensioning of the blocks
will depend on the application. In this example the blocks were
subject to a conventional pressurized, steam curing process. The
process incorporates a press using hydraulic compression to press
the concrete mix into the block form. The hydraulic press was
capable of exerting up to 35 kN (4 tons) of force on the wet
cementitious mix in the form and the full 4 tons was applied in
this experiment. Typically this pressure was applied for 1 to 4
minutes. Then the precast CPP blocks were steam cured (in a kiln
with over 90% humidity) for four days to a week to promote adequate
cement hydration and then the blocks were allowed to air dry for
two days before transport. Longer steam curing up to 28 days will
produce a higher strength material. Of course, there is a
substantial amount of flexibility in the application of these
various components in making CPP. For example, although the
experiment above used 4 tons of force (or about 3000-lb/ft.sup.2)
applied for approximately 1-minute, both the force and duration of
the loading can vary based on the application. Those skilled in the
art will recognize many applications that may require less force or
applications requiring more or less duration of the loading.
Precast units and blocks can also be made on-site in molds at
ambient pressure and temperature however material properties can be
more variable than in a machine-controlled process.
[0061] From each porous pavement mix design, a block was sampled at
random to determine the strength and infiltration capacity. From
each block five cores are drilled using a 8 cm (3 in.) outside
diameter diamond tipped coring bit. This yielded cores
approximately 7 cm (2.75 in.) in diameter. The infiltration
capacity of the porous pavement blocks was evaluated by the falling
head permeability test for soils. Each core was wrapped with an
impermeable membrane to determine hydraulic conductivity of the
block. Flow was introduced from the bottom of the sample to ensure
complete saturation. Two trials were taken for each core resulting
in ten hydraulic conductivity values for each porous pavement mix
design. As shown in Table 3, Batch 2 has the greatest hydraulic
conductivity. Blocks tested later as full blocks had a full block
K.sub.sat of approximately 0.01 cm/s.
[0062] Since the CPP on the roadway shoulder may be subject to
occasional traffic loads (or many wheel loads in the case of
parking areas), block strength is an essential consideration in the
design. The unconfined compression strength of the blocks was
evaluated. Two of the five cores from each mix design were tested
to determine the unconfined compression strength. Since the length
to diameter ratio of the cores was less than 1.8, the strength was
reduced by applying the appropriate correction factor as designated
in ASTM C-39. The resulting compression strengths of the three
batches are seen in table 3.
TABLE-US-00003 TABLE 3 Measured Characteristic of the CPP Blocks
Average Hydraulic Average Unconfined Mix Conductivity Compressive
Design Unit Weight (cm/sec) Strength Batch 1 14.8 kN/m.sup.3 0.0091
37,500 kPa (93.9 pcf) (5440 psi) Batch 2 14.1 kN/m.sup.3 0.0098
27,700 kPa (89.6 pcf) (4020 psi) Batch 3 14.6 kN/m.sup.3 0.0090
33,600 (93.0 pcf) (4880 psi)
[0063] It is noted that these are only a few examples of measured
characteristics of CPP blocks. In other blocks, it is envisioned
using CPP where the hydraulic conductivity values are designed
either higher or lower than the above values by adjusting the water
to cement ratio or adjusting the fine to course aggregate
ratio.
[0064] Previously described was a process of creating CPP blocks
and then coating the blocks with an amphoteric compound by soaking
the blocks in a solution containing the amphoteric compound or
spraying on an amphoteric solution. However, the amphoteric
compound could also be incorporated in the CPP as part of the
process of mixing the cement/aggregate slurry; as an admixture. An
example of this method follows.
[0065] In a shallow container of large surface area compared to
depth (in the lab environment, shallow glass trays in the range of
12.times.16 inches were used), there is placed a solution of 0.1 to
5.0 molar solution of a metal salt or oxide or combinations of
metal salts or oxides. The solution can be made by either method
described above. To this solution, add a total of 1-kg of cement,
and aggregate at the water/cement ratio and cement/aggregate ratio
of choice to produce concrete of the strength and porosity desired.
Those skilled in the art will understand that whatever volume of
amphoteric solution is added should count toward the total water
cement ratio. For example, using 1 kg of cement and a water cement
ratio of 0.5, the adding of 0.25 kg of amphoteric solution will
require an additional 0.25 kg of water to be added. The mixture is
then dried (i.e. the cement is hydrated and the concrete mixture
hardens) approximately 12 hours. It should be noted that at least
part of the water in water-cement slurry is actually the solution
of metal salt or oxide or combination thereof. In effect, the
entire cementitious material is coated inside and out side with an
amphoteric coating. The same method could be carried out for an
iron oxide or silica coating but with the one difference; the CPP
or cementitious media must be dried at an elevated temperature of
90 to 100.degree. C. for at least 24 hours. As with all media
discussed above, if an iron oxide or silica coating is not fully
dry before rinsing, some of the coating will be washed off. While
this is also a concern for manganese or aluminum oxide coatings it
is less of a concern since these oxides usually bond far better to
substrates such as CPP (and prepared polymer beads) than iron
oxides. When the amphoteric compound is included in the concrete
mix in a sufficient amount as an admixture, the occurrence of the
amphoteric compound on the surface of the concrete media is
sufficiently dense and uniform over a substantial part of the media
surface such that the amphoteric compound acts as and should be
considered a "coating" as that term is used elsewhere in this
application.
[0066] With cementitious material as a porous matrix (i.e. as a
substrate), final pH conditioning of the iron oxide coating is
usually not required because the alkaline nature of the cement
raises the pH to acceptable levels. In fact, the acidic nature of
the iron oxide solution (and to a lesser extent the manganese or
aluminum solution) actually creates more internal porosity of the
CPP by consuming a portion of the cement matrix through a
neutralization reaction. However, this increased internal porosity
may also result in a reduction in the cement matrix's strength.
This is problem which is less prevalent when manganese, aluminum or
silicon is the base metal salt, or combinations thereof, for the
amphoteric substance or compound.
[0067] One useful application of a CPP coated with an amphoteric
compound is as a paved area, parking area or roadway shoulder
filtering section. For example, FIG. 4 illustrates a cross-section
of a typical roadway. The roadway will have driving lanes 5 with
shoulders 4. In the embodiment of FIG. 4, the shoulders are formed
of a CPP having an amphoteric compound coating as described above.
Typically, the CPP shoulder will have a thickness ranging from 4 to
16 inches. Rainfall-runoff or snowmelt depicted by arrows 6 will
flow off of the driving lanes 5 and onto the CPP shoulders 4. The
runoff will infiltrate and percolate into the CPP material and
dissolved ionic species, complexed species or particulate-bound
species will be sorbed or filtered by the amphoteric compound on
the CPP material. The intercepted runoff that has been treated will
then flow out of the side and bottom of the CPP shoulders 4.
[0068] Another application of cementitious material or concrete
produced with an amphoteric solution is use as a crushed aggregate
filter media. In other words, the object is not to have water flow
through the individual pores of a concrete block, but to have it
flow around broken up concrete rubble. To create a concrete media
or cement media that is fully impregnated with manganese, the
water-cement ratio would be higher to ensure sufficient cohesive
and adhesive bonding within each piece of media. In this situation,
the water cement ratios are close to that of standard concrete
mixes and a preferred range would be 0.30 to 0.90. This water
cement ratio includes the aqueous solution gained from the
admixture. This will be referred to as the "aqueous solution cement
ratio" to imply that both water and the admixture solution are
considered in computing the ratio. The concrete would be mixed as
above and once it hardens (from example, after 12 hours), it is
broken up as rubble into media sizes of choice. In certain
embodiments, these sizes can range from 0.1 to 10 mm, but sometimes
larger, up to 100 mm or more and other embodiments could include
any sub-range between 0.01 and 500 mm. If the amphoteric admixture
did not provide sufficient amphoteric substance on the accessible
surfaces of the rubble, the rubble could then be coated with a
layer of amphoteric compound such as described above in regards to
polyethylene beads. It will be understood that a bed of granular
porous pavement will have an enhanced porosity as opposed to
largely impermeable media pieces (e.g., polymer beads). Granular
porous pavement media will have pores between discrete pieces of
media in addition to the pores within the pieces of media
themselves. In one embodiment, this combined porosity of the media
is about 0.1 to about 0.6 for media with little internal porosity
and in another embodiment is about 0.2 to about 0.8 for media with
internal porosity.
[0069] In other embodiments, polymeric compounds or organic-based
materials that include light weight materials with a specific
gravity of less than about 1.0 and in other embodiments, less than
about 0.9 can be applied with a thin cement paste that contains an
amphoteric substance (e.g., manganese, iron, aluminum or silica
based). There are at least two methods by which the amphoteric
substance may be applied. First is a two stage process: 1) a thin
cement paste which hydrates and hardens (preferably in hours) is
applied to the media; and 2) then the media is coated with a
solution containing an amphoteric substance of manganese, iron,
aluminum or silica. In a single step process, the cement mix
contains an amphoteric compound solution as an admixture (prior to
the cements application to the substrate) in order to produce the
amphoteric substance on or in the substrate. In either case, the
resulting polymeric or organic substrate and coating has a net
specific gravity less than 1.0 and floats under quiescent
conditions. Both the cement coating and solution can be applied in
serial processes with hydration used as an intermediate step
between the two applications.
[0070] Another method of coating the CPP (or other substrates)
includes recoating the media. One example of recoating the media
was accomplished by placing the media in a column in which it will
be fluidized with a recirculating flow of manganese solution. Thus,
1-kg of media was placed in a vertical column (the column was
approximately 2 liters in volume) with a 6-liter recirculating
solution of 10.sup.-3M NaHCO.sub.3 and 0.035-moles/liter Mn.sup.2+
(stoichiometric amount) and re-circulating this solution with a
pump capable of handling aggressive solutions and with a sufficient
capacity to fluidize the bed. The Mn.sup.2+ is oxidized by adding
250-mL of a 0.185 M solution of NaOCl at a flow rate of 5 mL/minute
for 1 hour to ensure complete oxidation of the manganese. The
manganese oxide in this solution is then re-circulated for an
additional 2 hours with 250-mL of 0.185 M NaOCl added in one step
at the beginning of the 2 hours. After 2 hours, the solution was
drained and then replaced with water (in the lab, it was de-ionized
(DI) water) and re-circulated for 15 minutes and then the column
was drained of the water solution. The media was then rinsed with
water (DI in lab) to a pH of 7 and then allowed to dry overnight
before use. The rising of a manganese oxide coated media with DI
water was mainly to remove impurities in order to obtain laboratory
quality samples. In practical field applications, the final rinsing
of manganese oxide coated media could be dispensed with.
[0071] Naturally, re-coating of the media is not limited to
manganese oxide upon manganese oxide. Another re-coating method
would include a first coating with iron oxide followed by a second
coating of manganese oxide. If the iron oxide coated material
produces a sufficiently high SSA substrate for the intended
application, this latter method may be more desirable since iron
oxide is normally less costly than manganese oxide. Thus, a
comparatively inexpensive substrate such as sand with a low SSA may
be coated with iron oxide to produce a comparatively high SSA
substrate (i.e. a substrate with a SSA much greater than 0.1
m.sup.2/g). In other words, the iron oxide coated sand becomes the
substrate for the final filter media which is coated with manganese
oxide. Additionally, the increased SSA achieved by re-coating may
be applied to any of the above disclosed substrates (CCP, wood,
polymers, etc.) or with other oxides of metals such as aluminum,
silica or other surface active materials of high surface area and
amphoteric nature. A combination of coatings can allow the same
media or CPP system to incorporate sites for adsorption of cations
and anions.
[0072] The scope of the present invention also includes coating
formed of combinations of silica with different amphoteric
compounds. For example, a substrate could be immersed in a solution
containing silica (e.g. about 0.1M to about 5.0M) and aluminum
oxide (or iron oxide or manganese oxide, again at example
molarities of about 0.1M to about 5.0M) and then heated to dryness.
The ratio of silica to aluminum (or iron or manganese) oxide in the
solution could vary depending on the ultimate use of the coated
substrate, but in one embodiment the ratio could be 1 to 1.
However, the solution ratio could vary depending on the desired
ratio of total positive charge versus total negative charge at a
given target pH. Alternatively, the aforementioned solution could
be an admixture to a cementitious porous pavement (CPP) formulation
as mentioned earlier in this specification.
[0073] A combination coating could also be formed by a serial
process. In other words, first submersing the substrate in a silica
solution (and heating to dryness) and then submersing the silica
coated substrate in an aluminum (or iron or manganese) oxide
solution before heating to dryness. It will be understood that
coatings are not normally completely continuous over the entire
surface of the substrate. Imperfections will result in breaks in
the upper coating (aluminum oxide coating in the above example)
allowing the lower coating to be exposed to the environment and
bond with ions or complexes of the appropriate charge. Naturally,
the serial embodiment of the invention is not limited to a silica
coating followed by another coating, but could be formed in the
reverse order. Nor are the combinations limited to including
silica, but could be combinations of iron, aluminum, or manganese
oxides with no silica present. Likewise, anywhere in this
description where oxides of iron, aluminum, manganese, or silicon
are described, it will be understood the invention could
alternatively include non-oxide states of these metals and could
include any method of applying one or more of these metals to a
media substrate.
[0074] Rather than coating the same substrate particles with a
combination of amphoteric compounds, a similar effect may be
obtained by mixing substrate particles having different compounds
coated thereon. For example, a first quantity of media could be
coated with aluminum oxide and a second quantity of media coated
with silica. To form the final amphoteric compound coated filter
media, the two types of sand would be thoroughly mixed. An
alternative embodiment could comprise different types of filter
media in alternating layers. For example, FIG. 5A represents a
filter column 15 having alternating layers 10 of aluminum oxide
coated sand and layers 20 of silica coated sand and a contaminated
water stream 9 flowing therethrough. Naturally, the same type
filter could be implemented using other coated media such as
crushed CPP or polymer beads as disclosed above. Rather than a
filter column with a discrete particle filter media, the same
concept could be carried out in a CPP block having a contaminated
water stream 9 flowing therethrough. The CPP block 30 is formed by
first submersing the lower half 30a of block 30 in an aluminum salt
or oxide solution (and allowing to dry) to form coated layer 32.
Then the upper half 30b is submersed in a silica solution to form
coated layer 34. When a contaminated waste stream 9 passes through
the porous pavement material, the stream first encounters the
aluminum oxide coated layer and then encounters the silica coated
layer.
[0075] Naturally, there are many different ways to achieve the
effect of two different coatings. For example, the block 30 in FIG.
5B could be formed using an admixture of silica solution in the
cement mix, thus causing the entire block to initial have a silica
coating. Then, the lower half 30a could be immersed in an aluminum
oxide or salt solution, causing lower half 30a to have an aluminum
oxide coating. These and all other methods of obtaining a combined
coating of two different amphoteric coatings are included in the
scope of the present invention. It will also be understood that by
using amphoteric compounds with different pzc's at a given pH, it
will be possible to have substrate layers having different net
charges. For example, at a neutral pH, silica will have a net
negative charge for removing positively charged metal contaminants
while aluminum oxide will have a net positive charge for capturing
negatively charge contaminants.
[0076] Other embodiments of the present invention include not only
coating a CCP block through its entire depth, but also coating only
a fraction of the overall depth of the block. For example, the
upper area 30b in FIG. 5 could be coated with one of the above
mentioned amphoteric compounds, when the lower area 30a is left
uncoated. The coated depth could be as little as half an inch, but
more typically will be one half or more of the total depth of the
CCP block.
[0077] Additionally, substrates could be formed from any porous
structure having a fixed matrix. An example of such a porous fixed
matrix would be solidified lava (lava rock or pumice). A fixed
matrix having a porosity of between 0.05 and 0.6 would be one
embodiment of the present invention.
[0078] The present invention may be put to enumerable uses. For
example, while the above disclosure discusses a cementitious porous
pavement material, the porous pavement material could also be
bituminous or asphaltic. Porous asphalt can be made by reducing the
asphaltic binder and, in effect, producing a lower binder-aggregate
ratio. Typically, the amphoteric compounds described above may also
be added to the bituminous porous pavements during the mixing
stage, creating the same type of waterborne metals filter. However,
with all porous materials, an amphoteric material can always be
added as a surface coating and much of the porous surface can be
coated by application of a spray on the porous surface. If
practical to immerse the asphalt material in an amphoteric
solution, the amphoteric solution may be applied in this manner. As
used herein, "immersed" does not necessarily mean the entire volume
being completely submerged in a solution, but also includes dipping
only a part of the media volume in a solution.
[0079] Large areas of porous pavements may also be used as storm
water storage basins. Parking lots and similar large paved areas
are often the source of significant volumes of rainfall-runoff or
snowmelt. The porous pavement of the present invention provides a
means of substantially reducing the volume of runoff or snowment
from such large pavement areas. These areas may be defined as a
ratio of their length to width. In certain embodiments of the
present invention, a storage basin may be any pavement area having
a length to width ratio (i.e. length/width) of less than 20. A
typical parking area formed of porous pavement could have a porous
pavement with a hydraulic conductivity of between 0.0001 cm/sec and
1.0 cm/sec and more preferably of around at least 0.001 cm/sec.
Because it is not necessary to transfer the water so quickly in
parking areas, it may be preferred to have higher strength and
lower hydraulic conductivity. Porous pavement having a hydraulic
conductivity of 0.0001 cm/sec. and 1.0 cm/sec will normally have a
28-day unconfined compressive strength in one embodiment of between
approximately 2000 and 6000 psi and in another embodiment between
approximately 3000 psi and 5000 psi. The porosity of the pavement
in one embodiment will be between approximately 0.1 and 0.6 and in
another embodiment between approximately 0.15 and 0.5, and in a
third embodiment between approximately 0.2 and 0.35. In one
embodiment, such a layer of porous pavement could be at least four
to eight inches in depth and in another embodiment, at least twelve
to fifteen inches in depth. This depth provides both the necessary
strength to support vehicular traffic and also provides a
sufficient volume of pore space to store the water from a water
quality rainfall-runoff event With a porosity of 0.15 to 0.35, a 6
inch slab of porous pavement could retain as much as 1 to 2 inches
of rainfall in that slab. Rather than placing further strain on
storm sewers, the rain collected in the porous pavement will be
left to evaporate during dryer days. This method of storing runoff
from parking lots has the further benefit of tending to immobilize
parking lot pollutants entrained by the rain water. Rather than
leaving the premises of the parking lot, such pollutants will be
retained in the porous pavement. As the water evaporates from the
porous pavement over time, the pollutants will tend to be retained
in the pavement. Many volatile pollutants may be volatized into the
air during evaporation through the CPP material, a process which is
preferable to the pollutants becoming dissolved as mobile solutes
in water. Additionally, the porous pavement may be treated with an
amphoteric compound in order to improve the capture of waterborne
ionic constituents which are held in the porous pavement while the
retained water evaporates. It can readily be seen how a parking lot
constructed of porous pavement will form a storm water storage
basin capable of supporting vehicular traffic.
[0080] Another embodiment of the present invention includes a
roadway gravel shoulder capable of capturing waterborne ionic
constituents entrained in roadway rain runoff. Roadways often have
gravel shoulders at least four inches in depth, more typically six
to eight inches in depth and for larger roadways, often over eight
inches in depth. Commonly, the gravel for roadways is graded to
have an average diameter of between three-fourths of an inch to one
inch. To carry out one embodiment of the invention, the gravel may
be coated with an amphoteric compound such as one of the iron,
manganese, aluminum, or silica oxides disclosed above. In one
embodiment, this would be done prior to placing the gravel as a
roadway shoulder. Any of the coating processes discuss above would
be suitable, but the previously described field method for
producing large quantities of iron oxide coated sand would be one
preferred method. The gravel could also be subject to the multiple
layer coating also described above. Once the coating process for
the gravel was complete, the gravel would be placed along the
roadside in the normal manner for creating a shoulder. This manner
of capturing waterborne ionic constituents is advantageous because
it can passively filter and treat pavement sheet flow directly at
the edge of the pavement before the flow becomes concentrated.
[0081] A still further embodiment of the present invention
encompasses coating a flexible, planar, porous substrate with an
amphoteric compound. One example of a flexible planar, porous
substrate would be geosynthetic fabrics which are well known in the
art. Geosynthetic fabrics are generally polymeric materials which
are designed to be placed in or against soil. Often geosynthetic
fabrics are used to retain soil in place while allowing water to
pass through the fabric. Geosynthetic fabrics may be woven or
nonwoven. Woven geosynthetic fabrics are fabrics with filaments in
warp (machine direction) and weft (cross-machine) direction.
Nonwoven fabrics have essentially a random fabric or textile
structure. For example, common felt is a nonwoven textile.
Nonwovens are further characterized according to how fibers are
interlocked or bonded, which is achieved by mechanical, chemical,
thermal or solvent means. Some of the polymeric materials used to
construct geosynthetic fabrics include: polyethylenes--PE, HDPE,
LDPE, XLPE, FLPE, CPE, CSPE; polypropylene--PP, polysulfone--PSF;
polyurethane--PUR; polycarbonate--PC; polyvinyl chloride--PVC,
polystyrene--PS; thermoplastic elastomer--TPE; nylon--PA;
polyester--PET; nytrile; butyl; acetal--ACL; and polyamide--PA.
Most typically, geosynthetics are formed from PE, PP, PVC, PET, PA
or PS. The application of an amphoteric substance to the
geosynthetics could be carried out by a process similar to that
described above for coating polyethylene beads. However, rather
than stirring the beads, the sheets of fabric are dipped in
solution, pulled them out of the amphoteric solution, and then
dried them. The sheet could be left in the solution while dried,
but this method wastes a substantial amount of amphoteric solution.
With fabric or sheet material, the one technique would be to spray
on the solution and dry or to dip in the solution and dry.
[0082] Geosynthetic materials coated with amphoteric substances can
serve as more effective filters (higher surface area and surface
roughness) which can adsorb cations (e.g. heavy metals) or anions
(e.g. phosphates) depending on the pH of the aqueous stream,
seepage, ground water, or the like. The filters of the present
invention can be in-situ or ex-situ. An example of an in-situ
filter would be where one has shallow contaminated groundwater or
one is directing a flow of storm water into a trench. One can place
a sheet of amphoteric substance coated (with or without a
cementitious coating for the substance) geosynthetic fabric in a
trench, backfill around it and let the flow passively move through
the trench and therefore move through the more permeable
geosynthetic to provide in-situ treatment. Alternatively, a
cementitious coating could be applied to the geosynthetic fabric
with the amphoteric substance either being applied to the cement
after drying or as an admixture to the cement during its mixing.
Ex-situ filters would be all of those cases where one does
treatment in some form of a device or reactor, like the upflow
column seen in FIG. 1.
[0083] Another example of a flexible planar, porous substrate would
be membrane materials. Membrane materials typically have much
smaller pore sizes than other filters, commercially available on
the order of 0.1 to 50 microns and can be up to 3000 or more
microns. Often membrane materials are formed from a type of
cellulose such as cellulose acetate, cellulose esters, cellulose
nitrate, or nitrocellulose. The amphoteric coating may be applied
as described above for oxide coated geosynthetics. The membrane
substrates may be considered "membrane filters" in the sense that
they capture constituents only on their surface. This is
distinguished from the other substrates described herein which act
as "depth filters." Depth filters capture constituents through some
depth (even if relatively shallow) in the substrate.
[0084] The flexible planar, porous substrate could also include any
number of convention filter materials or devices which have a
larger area dimension than depth dimension. For example,
conventional air conditioning or furnace cartridge filters could be
formed by having an amphoteric compound applied to the filter media
within the cartridge. The filter media will typically be a fiberous
polymeric or glass material woven or meshed together at different
densities depending on the intended use of the filter.
[0085] A further embodiment of the present invention includes a
drainage pipe capable of capturing waterborne ionic constituents.
Most storm water runoff is carried through conventional concrete
pipes for at least part of the journey to its final collection
point. Thus there is the opportunity to bring the runoff into
contact with a pipe surface coated with an amphoteric compound and
remove ionic constituents from the water. Typically, drainage lines
are sized to accommodate a standard runoff rate which is less than
the total capacity of the drainage pipes. In other words, drainage
lines are not designed to have the average runoff completely fill
the volume of the drainage pipe. This means that less than the
entire inner circumference of the pipe is designed to come into
contact with the runoff water. Therefore, it may not be necessary
to coat the entire interior of the pipe with the amphoteric
compound, but rather only coat the portion of the inner pipe
surface designed to be in contact with the water. It will be
obvious that the decision concerning how much of the inner surface
of the pipe should be coated is a engineering design choice which
will vary according to the design parameters. One manner of
applying the amphoteric compound will simply be to immerse the
section of pipe to be coated in an amphoteric compound containing
solution such as disclosed above. For example, the solution could
be a 1 to 3 molar ferric nitrate or ferric chloride solution or a
0.1 to 5 molar solution of either birnessite or cryptomelane, or
aluminum or silicon. Alternatively, the amphoteric solution could
be applied directly to the pipe surface by spraying and the
like.
[0086] The piping could be formed out of conventional concrete or a
CPP material such as described above. The CPP piping would most
likely be used when the pipe grade was above the water table or
placed in soil which could otherwise readily absorb runoff. In this
manner, runoff flowing through the water could be at least
partially returned to the ground around the run of the pipeline.
The CPP piping could in one embodiment have a hydraulic
conductivity ranging from about 0.0001 to about 1.0 cm/sec. Both
the CPP piping and conventional concrete piping could have the
amphoteric compound introduced in the mixing process prior to the
concrete mixture being placed in the pipe forms. It is also in the
scope of the present invention to include conventional fired clay
piping which has been coated with an amphoteric compound or a
specially made clay piping which has had the amphoteric compound
added as part of the clay mixture before the pipe is fired.
[0087] Another embodiment of the present invention comprises
forming a filter by placing an amphoteric compound in a clay liner
or in a roadway sub-base. As used herein, the term "sub-base"is
intended to include a roadway sub-base formed of clay, silt or sand
or a mixture of these materials or recycled materials. This
sub-base may be water pervious or impervious. Conventionally, a
sub-base is formed by placing a layer of uncompacted soil or
recycled material over the area where the sub-base is to be
constructed. Water is then added to bring the sub-base to its
optimum compacted moisture content. The layer is then compacted to
a predetermined density. Typically, this process is carried out in
layers or "lifts" as is well known in the art. The optimum
compacted moisture content is determined by standard testing
procedures such as set out in ASTM D698. An improved sub-base
according to the present invention may be constructed by raising
the uncompacted sub-base to its optimum compacted moisture content
with a solution containing an amphoteric compound. It may not be
necessary to add the amphoteric solution to all lifts, but simply
the upper most 1 to 3 lifts. Clays have a wide range of SSA values
ranging from approximately 15 m.sup.2/g for clays like kaolinite or
illite up to approximately 850 m.sup.2/g for clays like sodium
montmorrillinite. Their large SSA values make clays a highly
effective substrate for applying amphoteric compounds.
[0088] Another geotechnical structure utilizing amphoteric
substance could be water impervious clay liners. While clay liners
are intended to be water impermeable, it is common for liners to
have some permeability resulting in water escaping from within the
liner into the surrounding soil. If the clay liner is treated with
an amphoteric substance, water traveling along the liner (toward
the break) or through the liner will have ionic constituents sorbed
from it. In a similar manner, some roadways are built with
sub-bases which are intended to be water impervious. Generally, it
is also not intended to have water flow through the pavement to the
sub-base. However, cracking in roadways is commonplace and
rainwater migrates through the cracks to the sub-base. If the
sub-base retains its water impermeable characteristics, water will
flow laterally to the edge of the roadway. If the sub-base is
coated with an amphoteric substance, ionic constituents are
effectively removed as the water travels along the sub-base toward
the edge of the roadway. If the sub-base also forms cracks, water
flowing through the sub-base will be treated.
[0089] FIG. 5C is a further filter system embodiment of the present
invention. Filter system 45 generally comprises rigid filter
housing 51 having an inlet 52 and an outlet 53. Positioned within
housing 51 is a filter media containment 56. In one preferred
embodiment, filter media containment 56 is form of a porous
flexible material such as a geosynthetic fabric 57 with sufficient
strength characteristics to contain the selected media without
tearing or failing. This embodiment of media containment 56 is
sized to be generally the same shape as and to fit closely against
the walls of housing 51. A handle 58 may be attached to media
containment 56 to allow easy insertion into and removal from
housing 51.
[0090] In the embodiment shown, media containment 56 encloses a
quantity of granular media 59. In a preferred embodiment, granular
media 59 is a crushed concrete aggregate having an amphoteric
compound formed thereon (as described above). A typical size range
for the aggregate will be about 1-10 mm, but is not limited to this
size range. The crushed concrete aggregate could be formed from
porous or nonporous cementitious concrete. Likewise, granular media
59 could be formed of other substances such as sand coated with an
amphoteric compound. Naturally geosynthetic fabric with less
porosity would be used when the media is sand as opposed to the
larger crushed concrete media pieces. In an alternative embodiment,
floating granular media could also be employed. It will be
understood that although FIG. 5C (and FIGS. 6A-8B) are showing open
space within media containment 56, the figures are intended to
convey conceptually that media containment 56 is substantially full
of granular media 59. In each of these configurations lightweight
media with a specific gravity of less than 1.0 can be applied.
[0091] A somewhat different configuration of filter system 50 is
shown in FIGS. 6A and 6B. FIG. 6A is a side view of filter system
50 illustrating a rigid filter housing 51 having an inlet 52 and
outlet 53. The filter system of FIG. 6A differs from that of FIG.
5C in that there is an interior hollow column 54 which forms an
annular space 55 (best seen in FIG. 6B) between the outer wall of
housing 51 and hollow column 54. The liquid stream to be treated
enters the top of hollow column 54 and flows downward to exit
through side openings 60 in the bottom of hollow column 54 and
enter into annular space 55.
[0092] Positioned within annular space 55 is the toroidal or ring
shaped media containment 56. As in the previous embodiment, media
containment 56 could be formed of geosynthetic fabric 57 of
sufficient strength characteristics, but could also be of any
material (flexible or rigid) which contains granular media 59.
While in the embodiment shown, media containment 56 is formed of a
uniformly porous fabric, other embodiments of media containment 56
could include other configurations wherein less than the entirety
of media containment 56 is porous. For example, the top and bottom
of media containment 56 (where fluid must pass) being porous while
the sides of media containment 56 are substantially non-porous. As
with the previous embodiment, granular media 59 could comprise a
crushed concrete aggregate having an amphoteric compound formed
thereon, coated sand, or any other coated granular media such as
media with a specific gravity less than 1.0.
[0093] A still further embodiment is seen in FIGS. 7A and 7B. FIG.
7A illustrates a down spout filter 65. Filter 65 generally
comprises a flexible media containment 66 of sufficient strength
characteristics filled with granular media 68 and having a
connecting sleeve portion 69 which slides over the terminal end of
conventional drainage down spout 70. Media containment 66 will
generally not be sufficiently porous to allow the passage of water.
However, outlet apertures 67 (or a porous area) will be formed in
some portion of media containment 66 (the top portion in the
example of FIG. 7A) in order to allow water flowing into media
containment 67 to exit there from after passing through filter
media 68.
[0094] FIG. 7B illustrates a filter system connected to a bridge
down spout 71. The embodiment of FIG. 7B is largely similar to that
of FIG. 7A. However, it will be understood that media containment
66 might typically hang freely from bridge down spout 71 and must
have sufficient material strength to support the weight of filter
media 68 by way of sleeve portion 69 being firmly clamped to down
spout 71. As with the previous embodiment, granular media 68 could
comprise a crushed concrete aggregate having an amphoteric compound
formed thereon, coated sand, or any other coated granular media. A
media formed of amphoteric compound coated polymer beads or other
lightweight media would be particularly suitable for the embodiment
of FIG. 7B since this would provide the least weight stress on the
hanging media containment 66.
[0095] The size and shapes of media containments 66 (and other
media containments disclosed in this application) will largely
depend on the flow path in which it is desired to direct the
liquid. The flow path should be sufficiently long to ensure the
liquid has sufficient residence time when passing through the
filter media in order to bring a sufficient percentage of the
liquid borne contaminants into contact with the filter media.
Factors such as the pressure, head loss and flow rate of the
liquid, the media size, hydrodynamics, desired residence time, and
ultimately performance will affect the size and shape of the media
containment.
[0096] FIG. 8A illustrates a still further embodiment of the
filtration system of the present invention. In FIG. 8A, filter
system 75 consists of a granular media 78 positioned within filter
containment 76. In this embodiment, filter containment 76 will
comprise a mesh material 77 which could be a porous geosynthetic
material, natural porous material but could also be a wire mesh
such as conventional "hardware cloth", "chicken wire" or chain-link
fencing wire. In the typical situation where the wire mesh has
openings larger than the media particles, a finer mesh such wire
window screening could be placed as a liner within the larger gauge
wire mesh.
[0097] In a preferred embodiment, filter containment 76 will be
shaped such that when filled with filter media, filter containment
forms a block shape. Then filter containment 76 (or several filter
containments 76) will be arranged in the flow path of the liquid
stream to be filtered. FIG. 8A suggests that the liquid steam is
flowing toward the top portion of filter system 75. It can be seen
that the filter media 78 in FIG. 8A is formed of a size gradation
of media particles. Toward the center of media containment 76 are
coarser media particles (e.g. on the order of 25 to 100 mm in
diameter) while around the outer sides of media containment 76 are
finer media particles 80 (e.g. on the order of 1 to 20 mm in
diameter). The purpose of these media size differences is to allow
freer flow of liquid to the center area of media containment 76 and
retard the flow of liquid toward the edges of media containment 76.
This media configuration will help ensure sufficient residence time
of the liquid flowing from top to bottom through the media as
opposed to liquid taking a shorter side path toward the outer edges
of media containment 76.
[0098] FIG. 8B illustrates yet another embodiment of the filter
system of the present invention. Filter system 90 will comprise
concrete blocks 91 with bore holes 93 formed therethrough. FIG. 8B
is a cross-sectional view and it will be understood that continuous
concrete extends around the parameter of blocks 91 to maintain the
block's structural integrity. The bore holes 93 will be filled with
granular amphoteric compound coated media 94 and a porous fabric or
wire mesh 95 will extend across the tops and bottoms of bore holes
93 in order to retain the granular media therein. As with the
previous embodiment, blocks 91 will be position in the liquid steam
path such that the liquid is directed through the media filled bore
holes 93.
[0099] FIG. 8C illustrates a filter system 100 which will generally
be employed adjacent to a paved area 101 such as a parking lot or
roadway (in which case the paved area 101 may act as a roadway
shoulder). A trench 105 is formed adjacent to the paved area 101.
Trench 105 will have a perforated drain pipe 105 positioned at its
bottom and will be filled with a granular media 103 such as
amphoteric compound coated sand. A cap 102 of cementitious porous
pavement will then be placed over granular media 103. In operation,
contaminant containing runoff from paved area 101 will flow across
and into porous pavement 102 and then through coated media 103
wherein positively and/or negatively charged (depending on the
media coating) ions and complexes are removed before the treated
water exits through discharge drain 104. As one illustrative
example, trench 105 could be approximately 60 cm deep, 30 cm wide,
and cap 10 cm thick. However, the filter system 100 could take on
any dimensions required by the particular design being
implemented.
[0100] In certain media embodiments described above where the
amphoteric substance is applied as a coating, the coating may be
comprised predominately of aluminum, iron, manganese, silicon or
combinations of these metals (or their oxides) such that the total
dry mass of the applied coating (to external and internal surface
areas) is greater than 0.05 milligrams per dry gram of media
substrate. Multiple layers of applied coatings would have a
linearly proportional composition per dry gram of media substrate.
For example, two applied layers would result in a media with a dry
mass of applied coating that is greater than 0.10 milligrams per
dry gram of media substrate.
[0101] In certain embodiments where the amphoteric substance is
applied as an admixture, the admixture may be comprised of
predominately of aluminum, iron, manganese, silicon or combinations
of these metals (or their oxides) such that the total dry mass of
remaining admixture that is a component of the media is greater
than 0.05 milligrams per dry gram of media.
[0102] In one embodiment where the media is coated with a
cementitious layer, the cementitious coating shall be such that the
total dry mass of the applied cementitious coating (to internal and
external surface areas of the media) is greater than 0.10
milligrams per dry gram of media substrate. Multiple layers of
applied coatings could have a linearly proportional composition per
dry gram of media substrate. For example, two applied cementitious
layers would result in a media with a dry mass of applied coating
that is greater than 0.20 milligrams per dry gram of media
substrate.
[0103] In many of the embodiments described above, the total dry
mass of the applied amphoteric substance per dry gram of media may
be at least 0.5 mg/g and alternatively ranging from about 0.5 mg/g
to about 50 mg/g. In alternative embodiments, amphoteric substance
could range from about 1 to about 20 mg/g or from about 5 mg/g to
about 10 mg/g. Other embodiments include all sub-ranges between
about 0.5 mg/g and about 50 mg/g.
Alternative Embodiments
[0104] While the foregoing invention has often been described in
terms of specific examples, those skilled in the art will recognize
many variations which are intended to fall within the scope of the
claims. For example, while the above has described the media as
utilized for removal of dissolved cations and anions, complexed
species and particulate-bound species from water, the media could
be utilized to remove many types of airborne or waterborne
non-ionic constituents. In particular, sand or polyethylene beads
filters could readily be adapted to treat flows of air for ionic
constituents such as aerosols, charged particulate matter, odors,
and gas emissions containing water vapor with anionic or cationic
species.
[0105] One embodiment of a filtration system for removing
negatively or positively charged ions, complexes or particulates
from an aqueous stream, may include: a) an aqueous stream formed
substantially of urban runoff; b) a filter containment
communicating with the aqueous stream such that at least part of
the stream passes through the filter containment; and c) a filter
media disposed within the filter containment, the filter media
comprising an amphoteric material applied thereto, wherein is
amphoteric material is an oxide of at least one of Al, Mn, Fe or
Si. The above filtration system wherein the aqueous stream is a
variable stream generated by a rainfall-runoff or snowmelt
event.
[0106] The above filtration system wherein the aqueous stream has a
pH of between about 6 and about 9. The above filtration system
wherein the filter media is a granular media having a total
porosity of between about 0.1 and about 0.6. The above filtration
system wherein the filter media is a fixed matrix media having a
total porosity of between about 0.1 and about 0.4. The above
filtration system wherein the fixed matrix is a cementitious porous
material.
[0107] The above filtration system wherein the amphoteric media
comprises both an oxide of Si and an oxide of one of Al, Mn, or Fe.
The above filtration system wherein the Si oxide media and the
media comprising an oxide of one of Al, Mn, or Fe are intermixed.
The above filtration system wherein the Si oxide media and the
media comprising an oxide of one of Al, Mn, or Fe are positioned in
distinct layers. The above filtration system wherein the filter
containment is formed by a porous textile (or geotextile) material.
The above filtration system wherein the filter containment is
formed by a porous mesh material. The above filtration system
wherein the porous mesh material is a wire mesh. The above
filtration system wherein a substantial portion of the aqueous
stream is runoff from an urban, constructed, disturbed or paved
surface.
[0108] The above filtration system wherein the cementitious media
has a depth divided into a first and second portion and one
amphoteric material is applied to the first portion. The above
filtration system wherein a second amphoteric material is applied
to the second portion. The above filtration system wherein the
amphoteric material is applied as an admixture. The above
filtration system wherein the filter system includes a rigid media
housing and the filter containment is a flexible material generally
shaped to fit within the media housing. The above filtration system
wherein the filter media is a granular media having a hydraulic
conductivity of between about 1 and about 0.0001 cm/sec. The above
filtration system wherein, the filter media is a fixed matrix media
having a hydraulic conductivity of between about 1 and about 0.0001
cm/sec. The above filter system wherein the filter containment is
in a toroidal shape.
[0109] The above filter system wherein the filter containment is
formed by positioning granular media within a trench and placing a
layer of porous cementitious pavement over the media. The above
filter system wherein the filter containment is formed of a mesh
material with smaller granular media positioned in the outer
portions of the filter containment and larger granular media
positioned in the inner portions of the filter containment. The
above filter system wherein the filter containment comprises bore
holes through a rigid matrix material.
[0110] An alternate filtration system for removing ions, complexes
or particulates from an aqueous stream would include: a) an aqueous
stream containing ions, complexes or particulates; b) a filter
containment communicating with the aqueous stream such that at
least part of the stream passes through the filter containment; and
c) a filter media disposed within the filter containment, the
filter media comprising an amphoteric material applied thereto,
wherein the amphoteric material is an oxide of Fe and has a crystal
inhibiting agent creating a SSA on the filter media of at least
about 10 m.sup.2/gm.
Additional Numbered Embodiments
[0111] Numerous additional embodiments are described in the
following numbered format.
1. Discrete Media, Amphoteric Coating of Single Oxide with Crystal
Inhibitor
[0112] One embodiment of the present invention is a
sorptive-filtration media for the capture of waterborne or airborne
constituents and particles. The media comprises a granular
substrate and a single amphoteric compound, preferentially an oxide
of aluminum, manganese, iron or silicon bonded to a substrate in
the presence of a crystal inhibiting agent.
2. Discrete Media, Amphoteric Coating of Single Oxide without
Crystal Inhibitor
[0113] Another embodiment of the sorptive-filtration media for the
capture of waterborne or airborne constituents and particles is a
media comprised of a granular substrate and a single amphoteric
compound, preferentially an oxide of aluminum, manganese, iron or
silicon bonded to granular substrates in either the absence or
presence of a crystal inhibiting agent.
3. Discrete Media, Amphoteric Coating of Mixed Oxides with Crystal
Inhibitor
[0114] Another embodiment of the sorptive-filtration media for the
capture of waterborne or airborne constituents and particles is a
media comprised of a granular substrate and a mixture of amphoteric
compounds, preferentially from oxides of aluminum, manganese, iron
or silicon bonded to granular substrates in the absence or presence
of a crystal inhibiting agent. The solution mixtures are generally
binary mixtures (excluding silicon or other crystal inhibiting
agent) of iron and manganese, aluminum and manganese, iron and
aluminum, iron and manganese, or silicon in combination with either
iron, manganese or aluminum. The proportions of the selected oxides
will be dependent, in part, on the surface charge, net point of
zero charge (pzc), and the relative population of charged sites
(both positive and negative) created by the resulting mineral
coating at a given pH, in order to target a specific constituent or
competitive combination of constituents. Solution mixtures do not
have to be only binary. For example, manganese can be added to a
binary mixture of iron and aluminum to create a lower net pzc and
create a relatively higher proportion of negatively charged sites
allowing the treatment of both positively and negatively charged
constituents. Certain combinations of oxides will obviate the need
for a crystal inhibiting agent. For example, combining a manganese
oxide in percentages as low as 1% with an iron oxide can inhibit
iron oxide crystal formation.
4. Discrete Media, Amphoteric Coating of Mixed Oxides without
Crystal Inhibitor
[0115] Another embodiment of the sorptive-filtration media for the
capture of waterborne or airborne constituents and particles is a
media comprised of a granular substrate and a mixture of amphoteric
compounds, preferentially from oxides of aluminum, manganese, iron
or silicon bonded to granular substrates in the absence of a
crystal inhibiting agent. The solution mixtures are binary
mixtures, examples of which are iron and manganese, aluminum and
manganese, iron and aluminum or silicon in combination with either,
iron, manganese or aluminum. The proportions of the selected oxides
may be dependent, in part, on the surface charge, net point of zero
charge (pzc), and the relative population of charged sites (both
positive and negative) created by the resulting mineral coating at
a given pH, in order to target a specific constituent or
competitive combination of constituents. Solution mixtures do not
have to be only binary. For example, manganese can be added to a
binary mixture of iron and aluminum to create a lower net pzc and
create a relative increase of negatively charged sites allowing the
treatment of both positively and negatively charged constituents.
One of ordinary skill in the art will recognize that differing
ratios of these oxides will result in coatings with a range of
differing sorptive-filtration properties and these variable
affinities would be altered by design depending on the competitive
combination of constituents, aqueous chemistry (for example pH),
hydrodynamics, equilibrium capacity and kinetics of the particular
situation.
5. Embodiment 1 Through 4 Having a Specific Gravity Between 0.2 and
1.0
[0116] Another embodiment of the present invention includes a
sorptive-filtration media which comprises a substrate as described
in embodiment 1 through 4 and having a specific gravity between
approximately 0.2 and 1.0.
6. Embodiment 1 Through 4 Having a Specific Gravity Between 1.0 and
6.0
[0117] Another embodiment of the present invention includes a
sorptive-filtration media as described in embodiment 1 through 4
and having a specific gravity between approximately 1.0 and
6.0.
7. Embodiment 1 Through 4 Composed of Rock, Earthen or
Modified-Earthen Substrate
[0118] Another embodiment of the present invention includes a
sorptive-filtration media which comprises a substrate of rock,
native earthen material; such as clay, silt, sand, volcanic
material, biological materials such as shells or modified earthen
material (for example to create a specific size gradation, altered
surface area or bulk density) such as perlite, fired silt or clay
particles or rubble, cemented soil material, volcanic material
(such as pumice), or calcareous material.
8. Embodiment 1 Through 4 Composed of a Cementitious Substrate
[0119] Another embodiment of the present invention includes a
sorptive-filtration media which comprises a substrate of
cementitious material such as created with a Portland cement,
lime-cement, combination of calcium-alumina-silica, or a material
with pozzolanic attributes; where a pozzolan is a siliceous or
siliceous and aluminous material that possesses little or no
bonding ability, but when finely ground into a high surface area
particles and in the presence of moisture will react with calcium
hydroxide at ambient temperatures to form resulting compounds that
possess cementitious properties.
9. Embodiment 1 Through 4 Composed of Cementitious Substrate and
Amphoteric Admixture or Amphoteric Coating
[0120] Another embodiment of the present invention includes a
sorptive-filtration media which comprises a substrate of
cementitious material such as created with a portland cement,
lime-cement, combination of calcium-alumina-silica, or a material
with pozzolanic attributes combined with an metal oxide or metal
salt admixture in the cementitious material. One example of such an
embodiment is described. The formulation can be scaled to meet
specific media amount requirements, or altered to fit porosity,
bulk density, surface area or surface charge requirements. This
example illustrates an amphoteric coating process for aluminum
oxide. However, the coating can be comprised of an oxide of iron,
manganese or silicon or a combination of these oxides as described
above.
1. Mix portland cement and clean water at a water/cement (w/c)
ratio of approximately 0.3 to 0.7. In one embodiment, the water,
containers, mixers, forms, admixtures, air-entraining agents, and
cement should be free of contamination from the compounds that are
intended to be treated by the media produced by this method.
Keeping such contaminants out of the resulting substrate/media is
beneficial since the substrate will not be acid-washed as with
other substrates such as clay, silt, sand, polymeric media, etc. 2.
Add a gas-entraining agent. A gas-entraining (or foaming or
blowing) agent can function to lower the dry density of the
resulting cementitious matrix towards 50 pounds per cubic foot by
creating a very large number of very small entrained air bubbles
(the conventional philosophy for a concrete based on strength and
dimensional stability); or function to create larger and fewer
pores. This latter function can be combined with an altered w/c
ratio to create a porous cementitious matrix of lower density and a
pore size distribution (PSD) that can range from single micron size
to millimeter size. The latter function is preferred because the
resulting media is a high surface area material with internal media
pores that are sufficiently large to result in one mode of
hydraulic communication through the media as well as another mode
of hydraulic communication through the pore space between the
media. 3. There are many gas-entraining agent (derivatives of
organic acids, natural or synthetic resins, detergents, anionic
surfactants, sulfonates, etc.) and systems that are available.
These agents should not contain significant levels of contaminants
that are intended to be removed by the media and should not produce
a toxicity product. This embodiment utilizes a permeable
cementitious matrix in a different manner than in a conventional
"impermeable" or "non-pervious application. The preferred
attributes of one embodiment of this permeable cementitious media
are a non-uniform PSD, open pore structure, lower density,
reasonable specimen strength (for example a 28-day compressive
strength, f'.sub.c of 50 psi or greater and some resistance to
abrasive handling), no contaminants or toxicity residuals and a
material that carbonates over time converting calcium hydroxide to
calcium carbonate. 4. Once water/cement and gas-entraining or
similar agent are mixed and the gas-holding matrix is created, the
mix is placed in a mold whose geometry is based on convenience,
curing, handling, later crushing, stacking, etc. For example,
thinner slabs will allow greater carbonation of material as
compared thicker geometries of less surface area. The gas-entrained
cementitious material is then cured for a minimum of 12 hours for
ambient air curing. Curing can be steam or pressure curing, or
both, but this is not required. 5. Once cured, the material is
broken or crushed to a selected media size and shape. Broken or
crushed media that does not fit the media size requirements is
discarded or re-used. The media size gradation can range from
uniform (approximately one equivalent diameter size) to
non-uniform. Media sizes and size gradations can range from 0.01 to
500 mm depending on head loss requirements and sorptive-filter
efficiency requirements. 6. The media is then coated with a minimum
concentration of about 0.1-M (or higher depending on coverage
requirements) aluminum nitrate. This can be a batch coating
process, a dipping process or a spraying process. The porous
cementitious material coats well. Once coated, the media is dried
at a minimum temperature of 60 C for a minimum of 4 hours to
dryness and then washed with clean tap water. The dry media is then
sacked or placed in cartridges.
10. Embodiment 1 Through 9 with Substrate SSA Greater than 0.1
m.sup.2/Gm
[0121] Another embodiment of the present invention includes a
sorptive-filtration media which comprises a substrate with a
specific surface area (SSA) of greater than 0.1 m.sup.2/gm.
11. Embodiment 1 Through 5 with a Polymeric Substrate of SSA
Greater than 0.03 m.sup.2/Gm
[0122] Another embodiment of the present invention includes a
sorptive-filtration media which comprises a polymeric substrate
with a specific surface area (SSA) of greater than 0.03
m.sup.2/gm.
12. Embodiment 1 Through 5 with a Cemented or Metamorph of Clay or
Silt Substrate
[0123] Another embodiment of the present invention includes a
sorptive-filtration media which comprises a clay or silt substrate
that has been cemented or has undergone metamorphosis through
heating and/or pressure and/or chemical modification. Cementing of
clay or silt substrates to form sorptive-filtration media or
aggregates can be carried out with Portland cement, lime or
cementing agents that are used to form larger aggregate media from
binding much smaller clay or silt particles together. Media size
ranges can have equivalent diameters between 0.01 mm and 500
mm.
13. Embodiment 12 without an Amphoteric Coating
[0124] Another embodiment of the present invention includes a
sorptive-filtration media which comprises a clay or silt substrate
that has been cemented or has undergone metamorphosis through heat
and/or pressure and/or chemical modification and no amphoteric
coating.
14. Embodiment 1 Through 13 with a Particle Size Range from 0.01 mm
to 500 mm
[0125] Another embodiment of the present invention includes a
sorptive-filtration media ranging in size from 0.01 mm to 500 mm.
Below 0.01 mm, hydraulic conductivities are too low for the medium
to function effectively as a filter at common surface loading rates
between 0.1 and 10 gallons/ft.sup.2-minute and above 500 mm,
specific surface area, pore size and residence times are too large
to have a significant benefit on treatment for particles or
solutes.
15. Embodiment 12 with an Amphoteric Coating
[0126] Another embodiment of the present invention includes a
sorptive-filtration media which comprises a clay or silt substrate
that has been cemented or has undergone metamorphosis through heat
and/or pressure and/or chemical modification with an amphoteric
coating. One example of such an embodiment is described The
formulation can be scaled to meet specific media amount
requirements, or altered to fit porosity, bulk density, surface
area, surface charge requirements or contaminant sorption
requirements. This example illustrates an amphoteric coating of
aluminum oxide. However, the coating can be comprised of an oxide
of iron, manganese or silicon or a combination of these oxides as
described above.
1. Mix 2 kg of water at 15 to 35 C with a biological blowing agent.
One preferred blowing agent is yeast which is added at
approximately 1% or greater by dry weight of total dry clay. There
are a variety of biological blowing agents that can be added.
Depending on the mixing conditions, yeast and temperature, this
mixing may require several minutes or longer. As soon as the
mixture begins to froth or bubble with evolved gas, ground clay is
added and mixed into the gas-water mixture. As with a cementitious
matrix there are many gas-entraining, foaming or blowing agents for
a cohesive matrix. In this example, yeast spores are uniformly
interspersed in the clay matrix, coming out of a spore-phase
because of the water, temperature and nutrients, to produce copious
amounts of gas bubbles. Organic and inorganic chemical blowing
agents or phase-changing blowing agents can also be utilized.
Physical blowing agents can also be utilized and have shown
success. One of the benefits of yeast is that the there is little
residual agent left after firing. 2. Mix or blend in 1 kg of ground
kaolinite (a common clay mineral) into the 2 kg of water 3. After
the kaolinite is blended in, mix rapidly in about 1/3 of 0.5 kg of
sodium bentonite (main ingredient in drilling mud, sealing mud,
slurry mud), trapping and coalescing the gas bubbles. Allow the
viscous clay to set for a minute or longer. A very lumpy texture
will begin to form. After several minutes mix in the balance of the
bentonite. Put in molds where in this case, clay slurry depth is
important. Clay slurry depth in the molds should be at least 1 inch
deep. Allow the clay to remain in the molds for 30 minutes or
longer at a temperature of at least 15 C before placing in an oven
at 60 C for at least 2 hours. One of ordinary skill in the art will
recognize that there are many variations of this formulation that
will provide differing media porosities and bulk densities
depending on media requirements. 4. After drying with sufficient
moisture driven off fire the clay at a minimum temperature of 500 C
for at least 1 hour or longer. After the firing, allow to cool and
the crush or break to same specifications as embodiment 14. 5. Soak
media in a 0.1-M or greater nitric acid solution for 30 minutes to
remove any residual contaminants that are part of the clay, water,
molds or agents. Rinse off acid from media surface with clean
water. If there are no contaminants or trace levels of contaminants
this step is not required. 6. The media is then coated with a
minimum concentration of 0.1-M (or higher depending on coverage
requirements) aluminum nitrate. This can be a batch coating
process, a dipping process or a spraying process. The porous clay
material coats very well because of high surface area and surface
charge. Once coated, the media is dried at 60 C for at least 4
hours to dryness and then washed with clean water. The dry media is
then sacked or placed in cartridges. The resulting media is very
porous, hydroscopic, with a very porous and a rough surface for
filtration and has a good compressive strength (cannot be crushed
by hand) and is not friable. The media can have significant
internal pore structure.
16. Embodiment 1 Through 14 with an Amphoteric Admixture
[0127] Another embodiment of the present invention includes a
sorptive-filtration media which comprises a clay or silt substrate
that has been cemented or has undergone metamorphosis through heat
and/or pressure and/or chemical modification with an amphoteric
substance admixture.
17. Embodiment 1 Through 14 with an Amphoteric Admixture and
Coating
[0128] Another embodiment of the present invention includes a
sorptive-filtration media which comprises a clay or silt substrate
that has been cemented or has undergone metamorphosis through heat
and/or pressure and/or chemical modification with an amphoteric
admixture and a further amphoteric coating.
18. A Porous Pavement Medium with a Single Oxide Amphoteric
Coating
[0129] One embodiment of the present invention is a pavement medium
material for the capture of waterborne constituents including
particles. The pavement material comprises a porous pavement
substrate and a single amphoteric compound, preferentially an oxide
of aluminum, manganese, iron or silicon applied to the porous
pavement medium substrate in either the absence or presence of a
crystal inhibiting agent.
19. A Porous Pavement Medium, with Amphoteric Coating of Mixed
Oxides
[0130] Another embodiment of the present invention is a pavement
medium material for the capture of waterborne constituents
including particles. The pavement material comprises a porous
pavement substrate and a mixture of amphoteric compounds,
preferentially from oxides of aluminum, manganese, iron or silicon
applied to the porous pavement medium substrate in the absence or
presence of a crystal inhibiting agent.
20. A Porous Pavement Medium, with Admixture in Binder
[0131] Another embodiment of the present invention is a pavement
medium material for the capture of waterborne constituents
including particles. The pavement material comprises a porous
pavement substrate matrix made from a binder wherein the water
fraction of this binder is comprised in part of an aqueous solution
of an amphoteric metal oxide or salt admixture.
21. A Cementitious Porous Pavement Medium, with W/C Admixture
[0132] Another embodiment of the present invention is a pavement
medium material for the capture of waterborne constituents
including particles. The cementitious pavement material comprises a
porous pavement substrate matrix made from a water:cement ratio and
an amphoteric compound or combinations of aluminum, manganese, iron
and silicon compounds utilized as part of the water:cement ratio.
In this embodiment, the pavement substrate is also comprised of
fine and/or coarse aggregate.
22. A Porous Pavement Medium, with Full-Depth Layered Amphoteric
Coatings
[0133] Another embodiment of the present invention is a pavement
medium material for the capture of waterborne constituents
including particles. The pavement material comprises a porous
pavement substrate with separate horizontal coating layers of
amphoteric compounds, preferentially from oxides of aluminum,
manganese, iron or silicon, applied to the porous pavement medium
substrate in the absence or presence of a crystal inhibiting
agent.
23. A Porous Pavement Medium, with Partial-Depth Layered Amphoteric
Coatings
[0134] Another embodiment of the present invention is a pavement
medium material for the capture of waterborne constituents
including particles. The pavement material comprises a porous
pavement substrate with separate horizontal coating layers of
amphoteric compounds, preferentially from oxides of aluminum,
manganese, iron or silicon, applied to the porous pavement medium
substrate in the absence or presence of a crystal inhibiting agent.
In one variation of this embodiment, the upper 20% or less of the
pavement remains uncoated.
24. A Porous Pavement Medium, with Full-Depth Mixture of Amphoteric
Coatings
[0135] Another embodiment of the present invention is a pavement
medium material for the capture of waterborne constituents
including particles. The pavement material comprises a porous
pavement substrate and a mixture of amphoteric compounds,
preferentially from oxides of aluminum, manganese, iron or silicon
applied to the porous pavement medium substrate in the absence or
presence of a crystal inhibiting agent. In this embodiment the full
depth of the pavement is coated with a mixture of amphoteric
coatings.
25. A Layered Porous Pavement Medium, with Partial-Depth Layered
Amphoteric Coatings
[0136] Another embodiment of the present invention is a pavement
medium material for the capture of waterborne constituents
including particles. The pavement material comprises a porous
pavement substrate with separate pavement material layers. In this
embodiment one or more layers will not be applied with an
amphoteric compound while one or more other layers will be applied
with one or a mixture of amphoteric compounds, preferentially from
oxides of aluminum, manganese, iron or silicon, applied to the
porous pavement medium substrate in the absence or presence of a
crystal inhibiting agent.
26. A 3'' Porous Pavement Medium, with a Full-Depth of Amphoteric
Coating
[0137] Another embodiment of the present invention is a pavement
medium material for the capture of waterborne constituents
including particles. The pavement material comprises a porous
pavement substrate and an amphoteric compound or a mixture of
amphoteric compounds, preferentially from oxides of aluminum,
manganese, iron or silicon applied to the porous pavement medium
substrate in the absence or presence of a crystal inhibiting agent.
In this embodiment the full depth of the pavement is coated with an
amphoteric compound or mixture of amphoteric compounds and the
pavement depth is at least 3 inches.
27. A 3'' Porous Pavement Medium, with a Partial-Depth Amphoteric
Coating
[0138] Another embodiment of the present invention is a pavement
medium material for the capture of waterborne constituents
including particles. The pavement material comprises a porous
pavement substrate and an amphoteric compound or mixture of
compounds preferentially from oxides of aluminum, manganese, iron
or silicon applied to the porous pavement medium substrate in the
absence or presence of a crystal inhibiting agent. In this
embodiment the upper 20% of the pavement is not coated with an
amphoteric coating and the pavement depth is at least 3 inches.
28. A 3'' or Deeper Porous Pavement Storage Basin
[0139] A further embodiment includes a runoff or drainage storage
or storage/treatment basin capable of supporting vehicular traffic.
The basin comprises a layer of porous pavement having a hydraulic
conductivity of more than 0.0001 cm/sec. The layer of porous
pavement is at least 3 inches in depth, and the layer has a length
and a width wherein the ratio between the length and the width is
less than 50. The total porosity of the porous pavement is greater
than 0.10. The pavement may comprise a compressive strength of at
least about 2000, 3000, or 4000 psi in other embodiments.
29. A 3'' or Deeper Porous Pavement Storage Basin w/an Embodiment
from 15 Through 24
[0140] A further embodiment includes a runoff or drainage storage
or storage/treatment basin capable of supporting vehicular traffic.
The basin comprises a layer of porous pavement having a hydraulic
conductivity of more than 0.0001 cm/sec. The layer of porous
pavement is at least 3 inches in depth, and the layer has a length
and a width wherein the ratio between the length and the width is
less than 50. The total porosity of the porous pavement is greater
than 0.10.
30. Process; Substrate SSA >0.1 m.sup.2/Gm and Amphoteric
Coating from Immersion
[0141] One embodiment includes a process for producing a
sorptive-filtration media for the capture of waterborne or airborne
constituents and particulates. The process comprises the steps of
providing a substrate having a specific surface area (SSA) of
greater than 0.1 m.sup.2/gm, introducing the substrate to a
solution (through mixing and partial immersion) such as a metal
salt or oxide solution, of one or a combination of aluminum,
manganese, iron and silicon compounds and volatilizing or drying
the solution, leaving a coating on the substrate (including inside
the outer surface of the substrate for porous substrates). This
resulting coated substrate has amphoteric properties in aqueous
solution.
31. Process; Substrate SSA >0.1 m.sup.2/Gm and Amphoteric
Coating from Spraying
[0142] Another embodiment includes a process for producing a
sorptive-filtration media for the capture of waterborne or airborne
constituents and particulates. The process comprises the steps of
providing a substrate having a specific surface area (SSA) of
greater than 0.1 m.sup.2/gm, introducing the substrate to a
solution such as a metal salt or oxide solution, of one or a
combination of aluminum, manganese, iron and silicon compounds by
spraying the solution onto the substrate or passing the substrate
through a spray, and volatilizing or drying the solution, leaving a
coating on the substrate (including inside the outer surface of the
substrate for porous substrates). This resulting coated substrate
has amphoteric properties in aqueous solution.
32. Process; Cementitious Coating with Admixture
[0143] Another embodiment includes a process for producing a
sorptive-filtration media for the capture of waterborne or airborne
constituents and particulates. The process comprises the steps of
coating a substrate with a cementitious coating wherein the aqueous
fraction of the water:cement ratio includes a solution of one or a
combination of aluminum, manganese, iron and silica oxide or salt
compounds. This coating with an admixture is dried on the substrate
with or without the benefit of drying aids such as additional
temperature, enhanced vapor gradients or convective gradients.
33. Process; Cementitious Coating with Amphoteric Coating
[0144] Another embodiment includes a process for producing a
sorptive-filtration media for the capture of waterborne or airborne
constituents and particulates. The process comprises the steps of
coating a substrate with a cementitious coating. This coating is
dried on the substrate with or without the benefit of drying aids
such as additional temperature, enhanced vapor gradients or
convective gradients. The cementitious coated substrate is
contacted with a solution of metal salt or oxide solution, of one
or a combination of aluminum, manganese, iron and silicon
compounds. The contact method is either through mixing, immersion
or spraying. The coating of metal salt or oxide solution on the
surface is volatilized or dried, leaving a coating on (and within)
the cementitious coating.
34. Process; Cementitious Media with Admixture
[0145] Another embodiment includes a process for producing a
sorptive-filtration media for the capture of waterborne or airborne
constituents and particulates. The process comprises the steps of
creating a substrate from cement and an aqueous solution where the
aqueous solution is comprised, in part, of solution of one or a
combination of aluminum, manganese, iron and silica oxide or salt
compound. The substrate slurry, paste or mixture is cured, and
formed or made into granular media of a chosen size gradation and
functions as a sorptive-filtration media.
35. Process; Cementitious Media Containing Aggregate with
Admixture
[0146] Another embodiment includes a process for producing a
sorptive-filtration media for the capture of waterborne or airborne
constituents and particulates. The process comprises the steps of
creating a substrate from cement, fine or coarse aggregate, and an
aqueous solution including a solution of one or a combination of
aluminum, manganese, iron and silica oxide or salt compound. The
substrate slurry, paste or mixture is cured and formed or made into
granular media of a chosen size gradation and functions as a
sorptive-filtration media.
36. Process; Cementitious Media w/Aggregate, w/Admixture and
Amphoteric Coating
[0147] Another embodiment includes a process for producing a
sorptive-filtration media for the capture of waterborne or airborne
constituents and particulates. The process comprises the steps of
creating a substrate from cement and an aqueous solution where the
aqueous solution includes a first solution of one or a combination
of aluminum, manganese, iron and silica oxide or salt compound. The
substrate can be created with or without fine or coarse aggregate.
The substrate slurry, paste or mixture is cured and formed or made
into granular media of a chosen size gradation and functions as a
sorptive-filtration media. The resulting sorptive-filtration
substrate is introduced to a second solution (by mixing, immersion
or spraying) such as a solution of one or a combination of
aluminum, manganese, iron and silica oxide or salt compound (which
may be the same as or different from the first solution), and
volatilizing or drying the solution, leaving a coating on the
substrate (or inside the outer surface of the substrate for porous
substrates). This resulting coated substrate is a
sorptive-filtration media.
37. Embodiment 30 Through 36 Resulting in Media with Specific
Gravity Between 0.2 and 1.0
[0148] Another embodiment is a sorptive-filtration media formed
through a process of providing a granular media with a specific
gravity between about 0.1 and about 0.9 and applying to said
granular media an amphoteric cementitious substance formed by any
method, including embodiments 30-36, in a full or partial coating
of said media. In certain embodiments, the thickness of the coating
will be such that the total specific gravity of the coated media
will be less than 1. In these embodiments, lower composite specific
gravities will require thinner coatings, down to about 50 microns,
whereas higher specific gravities (up to 1) can be achieved with
thicker coatings (depending in the density of the substrate) of up
to about 1 mm.
38. Embodiment 30 Through 36 Resulting in Media with Specific
Gravity Between 1.0 and 6.0
[0149] Another embodiment is a sorptive-filtration media formed
through a process of providing a granular media with a specific
gravity between about 1.0 and about 6.0 and applying to said
granular media an amphoteric cementitious substance formed by any
method, including embodiments 30-36, in a full or partial coating
of said media. Another embodiment employs a media having a specific
gravity of between about 2.4 and about 0.3 (non-limiting examples
of which are perlite and pumice). This latter embodiment could have
a size range from about 0.5 mm to about 100 mm. The specific
gravity of perlite is 2.2 to 2.4, but the bulk density of perlite
is much lower (about 0.4 to 0.8) since it is filled with voids. The
specific gravity of pumice is 0.6 to 0.7 and the bulk density is
about 0.4 to 0.6. One size range for this material that is suitable
for filtration is about 0.8 mm to 10 mm.
39. Process, Production of CPP with W/C<1 without Amphoteric
Coating/Admixture
[0150] Another embodiment includes a method for producing a porous,
cementitious material. The method includes the steps of providing
and thoroughly mixing cement and fine and/or coarse aggregate,
mixing water with the cement and aggregate into a slurry while
maintaining a water to cement ratio of less than one, initiating
curing of the slurry under pressure and in the presence of steam,
and continuing the curing at ambient temperature and pressure until
the cementitious material is substantially dry. Another embodiment
of this is to carry out curing at ambient pressure, temperature and
humidity. The total porosity of the porous pavement is greater than
0.05.
40. Process, Production of CPP with W/C<1 and with Amphoteric
Coating/Admixture
[0151] Another embodiment includes a method for producing a porous,
cementitious material. The method includes the steps of providing
and thoroughly mixing cement and aggregate, mixing an aqueous
solution comprised of one or a combination of aluminum, manganese,
iron and silicon oxide or salt compounds with the cement and
aggregate into a slurry while maintaining the water (aqueous
solution) to cement ratio of less than one, initiating curing of
the slurry under pressure and in the presence of steam, and
continuing the curing at ambient temperature and pressure until the
cementitious material is substantially dry. Another embodiment of
this is to carry out curing at ambient pressure, temperature and
humidity. The total porosity of the porous pavement is greater than
0.05. In each embodiment 39-41, those embodiments could also be
produced with a water to cement ratios of less than 0.9, less than
0.8, less than 0.7, less than 0.6, less than 0.5, or less than 0.4,
less than 0.3, less than 0.25, or less than 0.15 (if cured in the
presence of steam)
41. Process, Production of CPP without Steam, with W/C<1 and
Embodiment 35 and 36
[0152] Another embodiment includes a method for producing a porous,
cementitious material. The method includes the steps of providing
and thoroughly mixing cement and aggregate, mixing an aqueous
solution comprised of one or a combination of aluminum, manganese,
iron and silicon oxide or salt compounds with the cement and
aggregate into a slurry while maintaining the water (aqueous
solution) to cement ratio of less than one, initiating curing of
the slurry under atmospheric pressure and continuing the curing at
ambient temperature and pressure until the cementitious material is
substantially dry. The total porosity of the porous pavement is
greater than 0.05. This embodiment can also be produced without an
amphoteric compound.
42. Aggregate for Shoulder Coated with Amphoteric Compound
[0153] Another embodiment is a roadway or pavement system with a
shoulder formed of a cementitious granular material (e.g. aggregate
formed of crushed concrete) for the removal of waterborne dissolved
ionic, complexed or particulate-bound constituents. The roadway or
pavement system comprises a pavement section and a gravel shoulder
section adjacent to the pavement section. The sand to very coarse
gravel-size material has a depth of at least 3 inches and includes
sand, gravel, crushed or rubble material coated by an amphoteric
compound of aluminum, manganese, iron and silicon or combination
thereof.
43. Cementitious Aggregate for Shoulder Coated with Amphoteric
Compound
[0154] Another embodiment is a roadway or pavement system with a
cementitious granular shoulder for the removal of waterborne
dissolved ionic, complexed or particulate-bound constituents. The
roadway or pavement system comprises a pavement section and a
cementitious granular shoulder section adjacent to the pavement
section. The cementitious granular shoulder has a depth of at least
3 inches and includes cementitious granular or crushed
cementitious, aggregate or rubble material coated by an amphoteric
compound of aluminum, manganese, iron and silicon or combination
thereof.
44. Cementitious Aggregate for Shoulder with an Admixture of
Amphoteric Compound
[0155] Another embodiment is a roadway or pavement system with a
cementitious granular shoulder for the removal of waterborne
dissolved ionic, complexed or particulate-bound constituents. The
roadway or pavement system comprises a pavement section and a
cementitious granular shoulder section adjacent to the pavement
section. The cementitious granular shoulder has a depth of at least
3 inches and includes cementitious granular or crushed
cementitious, aggregate or rubble material made with an admixture
of amphoteric compound of aluminum, manganese, iron and silicon or
combination thereof.
45. Amphoteric Sub-Base or Base Material
[0156] Another embodiment includes a method of constructing a
sub-base or base subgrade for the removal of waterborne
constituents. The method includes the steps of placing a layer of
uncompacted sub-base or base material; distributing upon the layer
or mixing in the layer a solution containing an amphoteric compound
of aluminum, manganese, iron and silica oxide or salt, or
combination thereof, and compacting or densifying the layer to a
selected density.
46. Amphoteric Sub-Base or Base Material with Cementitious
Admixture
[0157] Another embodiment includes a method of constructing a
sub-base or base subgrade for the removal of waterborne
constituents. The method includes the steps of placing a layer of
uncompacted sub-base or base material; distributing upon the layer
or mixing in the layer a solution or slurry containing cement, lime
or pozzolanic material and amphoteric compound of aluminum,
manganese, iron and silica oxide or salt, or combination thereof,
mixing in and compacting or densifying the layer to a selected
density.
47. Amphoteric Sub-Base or Base Material with Cementitious
Admixture
[0158] Another embodiment is a sorptive-filtration medium for the
capture of waterborne or airborne constituents. The media comprises
a flexible, thin (less than 30 cm), planar, porous substrate such
as a synthetic or natural geotextile, geosynthetic or geocomposite
substrate material; and an amphoteric compound of aluminum,
manganese, iron and silica oxide or salt applied to the
substrate.
48. 3-D Flexible Porous, Hydraulically-Conductive Medium with
Amphoteric Coating
[0159] Another embodiment is an sorptive-filtration medium for the
capture of waterborne or airborne constituents. The medium
comprises a flexible, 3-dimensional, hydraulically-conductive
porous substrate matrix; and an amphoteric compound or combination
of aluminum, manganese, iron and silicon oxide or salt applied to
the substrate matrix. In this application, hydraulically-conductive
relates to the ability of the medium to conduct liquid or gas
through the medium. The medium is a planar medium that has a
thickness of greater than 1 mm. This medium can be formed into
irregular or regular geometries and is deformable yet possesses
sufficient strength to retain a pre-determined shape under it's own
weight or without peripheral containment required to retain a
pre-determined shape. Non-limiting examples of such hydraulically
conductive matrix include porous foams, woven and non-woven
geosynthetics, or mats of natural fiber materials.
49. 3-D Flexible Porous Polymeric Medium with Amphoteric
Coating
[0160] Another embodiment is a sorptive-filtration medium for the
capture of waterborne or airborne constituents. The media comprises
a flexible, 3-dimensional, porous natural or polymeric substrate
such as a geosynthetic; and an amphoteric compound or combination
of aluminum, manganese, iron and silica oxide or salt applied to
the substrate.
50. 3-D Flexible Porous Medium (as in Embodiment 48 and 49) with
Cementitious Coating
[0161] Another embodiment is a sorptive-filtration medium for the
capture of waterborne or airborne constituents. The media comprises
a flexible, 3-dimensional, porous natural or polymeric substrate
such as a geosynthetic; and a cementitious coating with either an
admixture containing an amphoteric compound or combination of
aluminum, manganese, iron and silica oxide or salt, or a coating of
the compound(s).
51. Drainage Pipe or Fixture with Amphoteric Coating
[0162] Another embodiment is a drainage pipe, hydraulic system or
fixture capable of capturing waterborne or airborne constituents.
The pipe, system, conveyance structure or fixture has an interior
surface, at least a portion of the surface being designed to be in
contact with water or gas. One example is a pipe sewer. An
amphoteric compound or combination of compounds is then applied to
the portion of the surface designed to be in contact with the
fluid.
52. Media or Medium with Multiple Layers of Amphoteric Coatings
[0163] Another embodiment of the invention includes a process for
creating a sorptive-filtration media or medium for the capture of
waterborne or airborne constituents. The process comprises the
steps of providing a substrate (inorganic, organic, cementitious,
earthen, rock, non-cementitious, pozzolonic) and applying a first
coating of an oxide compound to the substrate; and applying a
second coating of another oxide compound to the first coating. This
coating process can continue for "n" layers of differing or similar
oxide coatings.
53. Media or Medium with Cementitious Coating and Multiple Layers
of Amphoteric Coatings
[0164] Another embodiment of the invention includes a process for
creating a sorptive-filtration media or medium for the capture of
waterborne or airborne constituents. The process comprises the
steps of providing a substrate (inorganic, organic, cementitious,
earthen, rock, non-cementitious, pozzolonic), applying a
cementitious layer to dryness, and then applying a first coating of
an oxide compound to the substrate; and applying a second coating
of another oxide compound to the first coating. This coating
process can continue for "n" layers of differing or similar oxide
coatings.
54. Shoulder with Amphoteric Admixture/Coatings
[0165] Another embodiment of the invention includes a roadway with
a shoulder or any paved area forming a filter for dissolved ionic,
complexed or particulate-bound species. The roadway or paved area
comprises a paved section such as a traveled pavement and a
cementitious, porous, shoulder adjacent the paved section and the
shoulder having an amphoteric compound or combination of amphoteric
compounds applied thereto, or admixture thereof as part of the
water:cement ratio. The total porosity ranges from approximately
0.05 to 0.6.
55. Paved Porous Area with Amphoteric Admixture/Coatings
[0166] Another embodiment of the invention includes any paved area
forming a filter for dissolved ionic, complexed or
particulate-bound species. The paved area is comprised of
cementitious, porous material having an amphoteric compound or
combination of amphoteric compounds applied or bonded thereto, or
admixture thereof as part of the water:cement ratio. The total
porosity ranges from approximately 0.05 to 0.6.
56. Porous Media with Amphoteric Admixture/Coatings
[0167] Another embodiment provides a sorptive-filtration media
having a porous structure of a fixed matrix and a total porosity of
approximately 0.05 to 0.6 and an amphoteric compound or combination
of amphoteric compounds applied thereto or as an admixture
thereof.
57. Porous Pavement with or without Amphoteric
Admixture/Coatings
[0168] Another embodiment includes a method for forming a porous
pavement roadway. This method includes the steps of providing and
thoroughly mixing cement and aggregate; mixing water with the
cement and aggregate forming it into a slurry while maintaining a
water to cement ratio of less than one; and placing the slurry into
a roadway bed. The total porosity ranges from approximately 0.05 to
0.6. The water:cement ratio can be made with or without an
amphoteric compound or combination of aluminum, manganese, iron and
silica oxide or salt.
[0169] Applications of the above embodiments include without
limitation pavement systems, media systems, clarifiers, filters,
hydrodynamic systems, transportation systems. Other embodiments
include in-situ systems such as in-situ partial exfiltration
systems where the container may be a synthetic polymeric or natural
material such as a geosynthetic serving as the containing interface
between the media and the surrounding soil environment. Still
further non-limiting applications include inlets or catch-basins
for storm water, wastewater, natural flows or anthropogenic flows
such as industrial flows, end of conduit discharges, hydrodynamic
or volumetric separation systems, directed discharges from elevated
infrastructure such as downspouts, building drains or bridge
drainage, or as inserts in or appurtenances to unit operations and
processes (UOPs). Specific embodiments of this last application
include in-line or off-line adsorptive-filtration of discharges
from these UOPs, for example treatment of discharges from a basin
or clarifier that might provide preliminary or primary treatment,
application of the sorption-filtration media or fixed medium as a
direct primary treatment, or inclusion of the sorptive-filtration
media within all or part of the volume of a unit operation or
process (sometimes called best management practices, BMPs). Ex-situ
applications before or after UOPs can include cartridge or tubular
filters or fluidized bed systems.
[0170] These in-situ or ex-situ media embodiments can be arranged
in series; for example layers of media of differing size, differing
coating, differing substrates, differing pzc or charge, differing
specific gravity, differing conductivities, or differing substrates
in a single fixed or flexible container or in separate fixed or
flexible containers such as cartridges, tubes, compartments or
zones. These in-situ or ex-situ medium embodiments such as
cementitious porous pavement or 3-dimensional porous materials can
also be arranged in series having differing characteristics. The
relative proportion of these series will depend on the treatment
performance desired for specific constituents (for examples metals
or phosphorus) and for specific particle gradations. These in-situ
or ex-situ embodiments can be arranged in series and include a
process for producing a sorptive-filtration media for the capture
of waterborne or airborne constituents and particulates. The
process comprises the steps of providing a substrate with a
specific surface area of greater than 0.1 m.sup.2/gm, introducing
the substrate to a solution such as a metal salt solution, of one
or a combination of aluminum, manganese, iron and silicon compounds
and volatilizing the solution, leaving a coating on the substrate
(or inside the outer surface of the substrate for porous
substrates). This resulting coated substrate has amphoteric
properties in aqueous solution. All of these variations are
intended to come within the scope of the following claims.
* * * * *