U.S. patent application number 11/695154 was filed with the patent office on 2007-08-09 for growth media wastewater treatment reactor.
Invention is credited to Murphy Martin III Arcemont, Michael David Catanzaro, Christopher Edward Cox, Raleigh Lee Cox, Brenda Guy, Travis Lee LeJeune.
Application Number | 20070181494 11/695154 |
Document ID | / |
Family ID | 34910643 |
Filed Date | 2007-08-09 |
United States Patent
Application |
20070181494 |
Kind Code |
A1 |
Cox; Raleigh Lee ; et
al. |
August 9, 2007 |
Growth Media Wastewater Treatment Reactor
Abstract
A reactor chamber for placement in a wastewater treatment
system, where the reactor chamber has a chamber formed from a
sidewall which forms an interior of the chamber. The sidewall has a
top portion and a bottom portion and fixed channel growth media
positioned in the interior of the chamber. The fixed channel growth
media is positioned below the top of the sidewall, so that when
positioned in a treatment system, most of the growth media is
located below the water level in the treatment system. The top of
the sidewall near the water level (when positioned in a treatment
system) is substantially impermeable to wastewater. The reactor
includes an air distribution manifold system having a series of air
release sites positioned below the fixed channel growth media and
adapted to release air which disperses upwardly through the fixed
channel growth media. Influent is discharged into the treatment
tank near the air discharge sites.
Inventors: |
Cox; Raleigh Lee; (Baton
Rouge, LA) ; Cox; Christopher Edward; (Denham
Springs, LA) ; Guy; Brenda; (Baton Rouge, LA)
; Catanzaro; Michael David; (Baton Rouge, LA) ;
Arcemont; Murphy Martin III; (Gonzales, LA) ;
LeJeune; Travis Lee; (Baton Rouge, LA) |
Correspondence
Address: |
JONES, WALKER, WAECHTER, POITEVENT, CARRERE;& DENEGRE, L.L.P.
5TH FLOOR, FOUR UNITED PLAZA
8555 UNITED PLAZA BOULEVARD
BATON ROUGE
LA
70809
US
|
Family ID: |
34910643 |
Appl. No.: |
11/695154 |
Filed: |
April 2, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
11063084 |
Feb 22, 2005 |
7223343 |
|
|
11695154 |
Apr 2, 2007 |
|
|
|
10447464 |
May 29, 2003 |
6942788 |
|
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11063084 |
Feb 22, 2005 |
|
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Current U.S.
Class: |
210/615 |
Current CPC
Class: |
Y02W 10/15 20150501;
Y02W 10/10 20150501; C02F 3/101 20130101; Y02A 20/208 20180101;
Y02A 20/216 20180101; C02F 3/1247 20130101 |
Class at
Publication: |
210/615 |
International
Class: |
C02F 3/00 20060101
C02F003/00 |
Claims
1. A treatment system comprising: (a) a tank for processing
wastewater, said tank having a water level; (b) a growth media
reactor positioned in said tank, said growth media reactor having a
least one outer sidewall defining an interior forming a mixing
zone, said at least one outer sidewall extending above said water
level, said outer sidewall adapted to substantially fluidly isolate
said interior of said reactor from the exterior of said reactor
near said water level; (c) growth media positioned in said interior
of said growth media reactor; (d) an outlet removing waters from
said treatment system, said outlet exterior to said growth media
reactor; (e) at least one air discharge site adapted to be
connected to an air source, said air discharge site positioned so
that air released from said air discharge site will substantially
flow and disperse upwardly through said growth media; and (f) an
inlet feeding wastewaters external to said tank for treatment in
said treatment system, said inlet discharging into said tank near
said air discharge site.
2. A treatment system according to claim 1 wherein said growth
media comprises fixed channel growth media.
3. A treatment system according to claim 2 wherein said at least
one sidewall is partially formed by a portion of said fixed channel
growth media.
4. A treatment system according to claim 3 wherein said side wall
is substantially impermeable to wastewater.
5. A treatment system according to claim 2 wherein said fixed
channel growth media comprises a first component media and a second
component media, said mixing zone having a wastewater circulation
path having an upward flow portion and a downward flow portion,
said upward flow portion substantially flowing through said first
component media, said downward flow substantially flowing through
said second component media.
6. A treatment system according to claim 5 wherein said first
component media and said second component media each form channels
having a respective minimum cross-sectional area, said minimum
cross-sectional area of said first component media being smaller
than said cross-sectional area of said second component media.
7. A treatment system according to claim 2 wherein said fixed
channel growth media has a first component having cross flow
channels.
8. A treatment system according to claim 7 wherein said fixed
channel media has a second component substantially lacking cross
flow channels.
9. A treatment system according to claim 2 wherein said fixed
channel growth media is composed of a series of vertically
orientated panels forming channels between adjacent panels.
10. A treatment system according to claim 7 wherein said cross flow
channels are orientated at an angle from the vertical.
11. A treatment system comprising: (a) a tank for processing
wastewater, said tank having a water level; (b) a clarifier
positioned in said tank defining a quiescent zone; (c) a growth
media reactor positioned in said clarifier, said growth media
reactor having a least one outer sidewall defining an interior
forming a mixing zone, said at least one outer sidewall extending
above said water level, said outer sidewall adapted to
substantially fluidly isolate, in a region adjacent to said water
level, said mixing zone from the exterior of said mixing zone; (d)
growth media positioned in said interior of said growth media
reactor; (e) an outlet removing waters from said mixing zone, (f)
at least one air discharge site adapted to be connected to an air
source, said air discharge site positioned so that air released
from said air discharge site will substantially flow and disperse
upwardly through said growth media (g) an inlet feeding wastewaters
external to said tank for treatment in said treatment system, said
inlet discharging near said air discharge site.
12. A treatment system comprising: (a) a tank for processing
wastewater, said tank having a mixing zone and a dilution zone
separated by at least one sidewall positioned in said tank; said
mixing zone having a bottom portion in fluid communication with
said dilution zone; (b) said dilution zone and said mixing zone
having a water level; (c) an outlet positioned in said dilution
zone, said outlet located at or below said water level in said
dilution zone; (d) growth media positioned in said mixing zone,
said growth media positioned substantially below said water level;
(e) an air discharge site adapted to be connected to an air source,
said air discharge site located near said lower portion of said
growth media and positioned so that air released from said air
release site will substantially flow upward diffusing only through
said mixing zone; and (f) an inlet positioned in said tank to
discharge into said near said air discharge site.
13. The treatment system of claim 1 wherein said inlet is
positioned below said air discharge site.
14. A treatment system comprising: (a) a tank for processing
wastewater, said tank having a water level; (b) a growth media
reactor positioned in said tank, said growth media reactor having a
least one outer sidewall defining an interior forming a mixing
zone, said at least one outer sidewall extending above said water
level; (c) growth media positioned in said interior of said growth
media reactor; (d) an outlet removing waters from said treatment
system, said outlet exterior to said growth media reactor; (e) at
least one air discharge site adapted to be connected to an air
source, said air discharge site positioned so that air released
from said air discharge site will substantially flow and disperse
upwardly through said growth media; and (f) an inlet feeding
wastewaters external to said tank for treatment in said treatment
system, said inlet discharging into said tank near said air
discharge site.
15. A method of treating wastewaters in a treatment tank, said
wastewater having a water level in said treatment tank, said
treatment tank including growth media positioned in said tank and
at least one air discharge site, an inlet and an outlet, said
method including the steps releasing wastewaters from said inlet
into said treatment tank below said water level in said treatment
tank and near said air discharge site, aerating wastewaters near
said growth media so that air released from said air discharge site
will substantially flow and disperse upwardly through said growth
media; and removing wastewaters from said treatment tank through
said outlet.
Description
CROSS REFERENCE
[0001] This application is a continuation of application Ser. No.
11/063,084 filed on Feb. 22, 2005, which is a continuation-in-part
of application Ser. No. 10/447,464 filed May 29, 2003, and claims
the benefit thereof.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to wastewater processing reactors, and
in particular, to aerated fixed channel growth media reactors.
[0004] 2. The Prior Art
[0005] Aerated wastewater treatment systems designed for small
applications (less than 50,000 gallon daily capacity) generally
involve an aeration treatment chamber or zone for injecting air
into the wastewater, and a clarifier chamber of zone, a quiescent
zone in which particles are allowed to settle out of the system. An
example of such a treatment chamber is shown in Hansel. As can be
seen, the aeration treatment zone is generally an empty chamber
having several air release sites, usually located at the bottom of
the chamber. An aerated treatment system treats wastewater through
aerobic bacterial degradation of the waste materials present in
wastewater or sewage. Aerobic bacterial metabolic degradation
requires dissolved oxygen and hence, the release of air into the
treatment chamber. Anoxic (oxygen free) degradation can also occur,
and such is particularly efficient in removing undesired nitrates.
In the Hansel system, waters in the aerobic treatment chamber are
aerated, and in the process of aeration, mixing occurs, assisting
in the transfer of oxygen into the wastewaters. Waters in the
treatment chamber will eventually migrate to the clarifier zone. In
the clarifier zone, no mixing occurs and the waters are calm,
providing conditions to allow suspended solids to settle out of the
clarifier zone to be returned to the treatment zone for further
processing.
[0006] In the Hansel device, mixing and aeration occurs in a media
free zone. The bacteria/microbes float freely in the treatment
zone, having no surfaces (other than the container/clarifier
sidewalls) on which to attach. While such free floating bacteria
are effective in treating wastewaters, it is believed that more
efficient treatment can be accomplished by providing a surface for
bacterial and microbe attachment as in trickling type filtration
systems, and directing the waters through the treatment media for
treatment. Systems utilizing submerged growth media include that of
U.S. Pat. No. 6,153,099 to Weis, et al; U.S. Pat. No. 5,156,742 to
Struewing; U.S. Pat. No. 5,030,353 to Stuth; U.S. Pat. No.
5,200,081 to Stuth; U.S. Pat. No. 5,545,327 to Volland; and U.S.
Pat. No. 5,308,479 to Iwai, et al, all incorporated by reference.
In these systems, growth media is provided in the treatment or
reactor chamber (such as the floating media balls in Stuth or the
corrugated panels of Volland, and the cross flow media or vertical
flow media manufactured by Brentwood Industries of Reading, Pa.,
also shown in U.S. Pat. No. 5,384,178 and U.S. Pat. No. 5,217,788,
all incorporated by reference). Air lift or air release channels or
draft tubes (airlift pumps) are provided through the media, such as
in Struewing (reference 26), Iwai (reference 3P), Weis (reference
28), Stuth '754 (reference 12), and Stuth '081 (reference 8). Air
may also be released on an external side of the media, such as
shown in Volland. However, in these devices, oxygen is not directly
transferred to the growing biomass on the growth media, but only
indirectly and inefficiently through oxygen absorbed in wastewaters
(dissolved oxygen) transferred during the air lift operation.
[0007] Another device addressing clogging of media fixed film base
treatment is the device shown in U.S. Pat. No. 5,484,524 to
MacLaren, et al (incorporated by reference). This device shows
media disposed in a tank with a central media free core. An
aspirator or air release site is positioned in the media free core,
which induces a current in the tank, upward through the core, and
then substantially downward through the media (See FIGS. 8 and 9).
This device does not provide oxygen directly through the media, and
hence, still suffers from clogging (See U.S. Pat. No 6,105,593 to
MacLaren, et al, describing a cleaning probe for the '524 device)
and is not as efficient in providing oxygen directly to the growing
biomass.
[0008] A device utilizing air dispersed through the fixed media is
shown in U.S. Pat. No. 5,500,112 to McDonald. McDonald shows a
series of chambers filled with media. Air is released under
essentially the entire media bottom through a membrane covered
panel at the tank bottom and consequently, there is no established
circulation path through the media volume--upward flowing waters
and downward following waters are intermixed throughout the media
volume. Additionally, the McDonald device is a series of tanks
substantially filled with media: the McDonald device lacks a media
free treatment volume (a buffer zone or dilution zone). This lack
results in the need for an excessive amount of media to effect
treatment, making the McDonald device inefficient and uneconomic.
Additionally, the lack of a dilution or buffer zone in each reactor
chamber makes treatment inefficient. With no dilution zone,
McDonald places the aeration panels on the floor of each reactor.
The reactor floor is where sludge (fully digested waste materials)
normally would be deposited by precipitation. The McDonald device
forces sludge in all three reactor chambers to remain in suspension
until the sludge can be directed to a quiescent zone, the remote
McDonald 4th chamber. However, access from one reactor to the next
and eventually to the 4th zone, is through the fluid channels at
the very top of the reactor, also tending to keep sludge, which
would normally participate, in suspension in each reactor chamber.
Consequently, in McDonald each reactor chamber will have higher
sludge concentration levels than in systems having a dilution zone.
With higher concentration of solution sludge, treatment is more
inefficient as the ratio of usable (digestible) waste materials to
total waste materials is suppressed.
[0009] In aerated growth media reactors, current flow in the system
is induced by air injection. The induced current within the media
is generally an upward flow through the air lift tubes (or in the
case of Volland, on the side of the growth media) and downward
through the fixed media. In aerated growth media treatment systems,
waters remote from the treatment media must also be transported to
the media surfaces for treatment, as treatment is substantially
localized in the growth media. Hence, efficient mixing throughout
the entire chamber is highly desirable. The use of air lift tubes
generally induces a current in the treatment center sufficient to
provide the needed full system mixing, that is, to bring waters
remote from the growth media to the growth media for contact and
treatment by bacterial colonies attached to the growth media.
[0010] Use of air lift tubes thus induces a current and provides
indirect oxygen to the biomass. Air lift tubes also present
scouring of the growth surfaces caused by rising bubbles
interacting against the growth surfaces. As the introduced air is
not passing upwardly through the growth media, upward turbulence
through the growth media is reduced. Reduced upward turbulence in
the growth media increases the potential for bacterial growth to
occlude the channels, thereby plugging or clogging the flow
channels in the media. One attempt to minimize plugging is shown by
Volland. Volland uses corrugated panels placed back to back
creating channels orientated at 60 degrees from the vertical.
Volland thus tries to direct the bacterial slough-off down the
channels to the bottom of the media.
[0011] Growth media treatment systems as shown additionally
introduce wastewaters into the growth media by pumping incoming
wastewaters into a portion of the system remote from the media, and
allowing the induced current to transport the new influx of
treatable materials to the treatment media. This process, however,
dilutes the raw incoming sewage or wastewater and extends the time
for materials present in the incoming waters to be transported to
the treatment media.
[0012] Finally, all small plant treatment systems in the United
States must pass stringent regulatory requirements for effluent
quality and plant performance. Two of the plant performance
characteristics that fixed growth media treatment plants have
difficultly achieving are start-up time and vacation time. These
are time requirements during which a plant must meet effluent
standards: start-up time refers to the time a newly installed plant
must meet effluent standards after initial start-up; vacation time
refers to the time a plant must meet effluent standards after
re-starting from a dormant period (a vacation). The regulatory
requirement for start-up vacation times are difficult to achieve
for growth media surfaces as the biomass on the growth surfaces
must either be established (for start-up) or replenished after a
period of starvation (during the dormant period). The biomass
response time to condition changes, when localized as on a growth
media, is generally slower than in the extended aeration system,
such as the Hansel system. Consequently, a growth media treatment
system will take longer to start-up than an extended air treatment
system.
OBJECTS OF THE INVENTION
[0013] It is an object of the invention to provide an aerated
wastewater treatment system with growth media where air flow is
directed to disperse upwardly through the media.
[0014] It is an object of the invention to provide an aerated
wastewater treatment system with growth media with both upward and
downward flow through the growth media.
[0015] It is an object of the invention to provide an aerated
wastewater treatment system with growth media of at least two
differing flow paths.
[0016] It is an object of the invention to provide an aerated
wastewater treatment system with growth media and an integrated
clarifier.
[0017] It is an object of the invention to provide an aerated
wastewater system using growth media that provides for increased
oxygen transfer while maintaining adequate circulation in the
system.
SUMMARY OF THE INVENTION
[0018] The invention comprises a growth media reactor chamber
designed for placement in a wastewater treatment system. The growth
media reactor is a side-walled chamber having a growth media
positioned therein, where the bacterial growth media creates fixed
airway passages through the growth media. The outer walls of the
chamber extend above the growth media. When positioned in a
treatment system, the growth media is substantially at or below the
water level in the treatment system. Generally positioned below the
media is a series of air release sites, allowing air released from
these sites to disperse upwardly through the media. When positioned
in a treatment center, inlet waters are directly discharged into
the top of the reactor chamber. The top portion of the walls of the
reactor chamber should fluidly isolate the top interior portion of
the reactor chamber from the top exterior portion of the reactor
chamber. The reactor chamber creates a mixing/treating zone within
the wastewater treatment system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a prospective view of one embodiment of the
present invention showing the major components of the treatment
system.
[0020] FIG. 1A is a vertical cross-sectional view through FIG.
1.
[0021] FIG. 1B is a top view of the embodiment shown in FIG. 1.
[0022] FIG. 2 is a prospective view of a prior art treatment
system.
[0023] FIG. 2A1 is a side cross-sectional view of another
embodiment of the invention.
[0024] FIG. 2A2 is a top cross-sectional view of another embodiment
of the invention.
[0025] FIG. 2B1 is a side cross-sectional view of another
embodiment of the invention.
[0026] FIG. 2B2 is a top cross-sectional view of another embodiment
of the invention.
[0027] FIG. 2C1 is a side cross-sectional view of another
embodiment of the invention.
[0028] FIG. 2C2 is a top cross-sectional view of another embodiment
of the invention.
[0029] FIG. 3A is a side cross-section of an embodiment of the
invention where the mixing zone is essentially the interior of the
reactor.
[0030] FIG. 3B is a top elevation view of the invention depicted
in
[0031] FIG. 3A.
[0032] FIG. 4 is a cross-section view through another embodiment of
the reactor and air release locations, where the air release
locations are positioned internally in the reactor.
[0033] FIG. 5A is a side view (edge on) of six cross flow
panels.
[0034] FIG. 5B is a prospective view of two adjacent cross flow
panels showing the orientation of the corrugations on adjacent
sheets as being opposed.
[0035] FIG. 6A is a side view of two adjacent panels of vertical
flow fixed channel media.
[0036] FIG. 6B is a prospective view of two adjacent panels of
vertical flow fixed channel media.
[0037] FIG. 7 shows a front elevation view of a fixed channel media
panel having a series of dimples creating a series of fixed channel
cross flow paths.
[0038] FIG. 8A is a prospective view of a reactor having vertical
cross flow fixed channels where the sidewalls are constructed from
the vertical flow media panels.
[0039] FIG. 8B is a prospective view of a reactor having cross flow
fixed channels where the sidewalls are constructed from the cross
flow media panels.
[0040] FIG. 9 is a top cross-sectional view of a reactor showing
the media sheets, where some portion of the sheets extends above
the water level.
[0041] FIG. 10 shows a cross-section view of a reactor having a
mixture of vertical flow and cross flow media panels.
[0042] FIG. 11 shows a horizontal cross section of the treatment
system showing (by the reference to the dashed area) possible
locations of the inlet terminus.
[0043] FIG. 12 shows another embodiment of vertical flow media.
[0044] FIG. 13 shows a reactor volume constructed from the panels
of FIG. 13.
DETAILED DESCRIPTION OF THE INVENTION
A. The Treatment System--Retrofit
[0045] Shown in FIG. 2 is a prospective view of a prior art Hansel
system, showing a tank 1, a sidewall 2 creating an internal volume
considered the clarifier (also called the quiescent zone). The
volume external to the clarifier area contains a series of discrete
air release sites 300, connected by an air distribution manifold
301 to an air compressor. The volume external to the clarifier area
is considered the mixing zone. Wastewaters are brought into the
mixing zone through an inlet 6, and removed from the system through
outlet 7 positioned in the clarifier. FIG. 1 shows a Hansel-type
treatment system modified for incorporation in the present
invention. Shown is tank 1, having a closed bottom and closable
top, and is generally constructed of resin reinforced fiberglass,
concrete or metal. Positioned within the tank 1 is the clarifier
sidewall 2. As shown, tank 1 is a cylinder with clarifier sidewall
2 forming a second cylinder (the clarifier) having an open bottom
and open top positioned in the interior of the tank 1. Located in
the interior of the clarifier is the growth media reactor 100, with
growth media 200 positioned therein. Located below the reactor is a
series of air release sites 300, connected through a distribution
manifold 301. Inlet 6 brings incoming wastewater into the top of
the reactor 100. The volume of the treatment system below the
reactor 100 containing the air sites 300 is considered the air
release volume. The tank's volume is thus partitioned or separated
into four zones: (1) the interior of the reactor chamber
(considered the mixing zone 3); (2) the air release volume, the
volume of the tank where air injection takes place, preferentially
located beneath and adjacent to the reactor; (3) the quiescent
zone, the volume internal to the clarifier excluding the reactor
volume; and (4) the remainder of the tank external to the
clarifier, considered the dilution zone. This partition differs
from that of the standard Hansel type system where the interior of
the clarifier is considered the quiescent zone and the remainder of
the tank is the mixing zone. The quiescent zone is in fluid
communication with the dilution zone through the bottom open end of
the clarifier sidewall (that is, the reactor chamber does not block
fluid communication through the clarifier bottom opening). Note,
the clarifier sidewall is generally impermeable to wastewaters.
[0046] As shown in FIG. 1, outlet 7 removes water from the
quiescent zone (here, the interior of the clarifier external of the
mixing zone or reactor chamber; as shown by the dotted outline of
outlet 7A in FIG. 1A, the outlet 7 may also be positioned in the
dilution zone external to the clarifier). The mixing zone 3 is in
fluid communication with the quiescent zone 4 through with the
interior of the clarifier, and in fluid communication with dilution
zone through the open bottom 5 of the reactor chamber and the open
bottom of the clarifier. The outlet 7 removes treated waters from
the system. Also shown is air manifold 301 connected to a source of
air (a compressor, not shown), the air manifold terminates in a
series of openings, the air release locations 300, located beneath
the reactor chamber 100. When the air manifold is charged, air
travels through the manifold to be discharged from the air release
locations. A preferred structure for the air release location is
shown in U.S. Pat. No. 5,714,061 to Guy, et al, incorporated herein
by reference. In addition, the opening of the air release location
may be terminated in an open "L" shaped pipe fitting. Upon system
start-up, water in the air manifold may be discharged through the
open ends of the air release locations. The L shaped fitting acts
to re-direct downward flow of wastewater emanating from the air
distribution manifold away from the bottom of the tank to minimize
sediment disturbance. In most of the figures, the general locations
of the air release sites are indicated by an "O." The "O" is
intended to show the general location, but not the structure, of an
air release location.
[0047] FIG. 1A shows a cross-section through the treatment system
in FIG. 1, while FIG. 1B shows a top view of the treatment center
in FIG. 1. An additional feature shown in FIG. 1A is a
recirculation means, here an air lift tube 700, later
described.
[0048] The specific geometry of the tank arrangement utilizing a
growth media reactor can vary. Shown in FIGS. 2A-2C are other
arrangements of tank and clarifier sidewalls. In FIG. 2A, a top and
side cutaway view a circular tank 1 is shown with the clarifier
sidewall 2 forming a cylinder positioned in the tank 1. In this
embodiment, the mixing zone 3 is three reactors 100 located in the
dilution zone located between the clarifier sidewall 2 and the
exterior wall of the tank. Outlet 7 is located in the quiescent
zone internal to the clarifier. Each reactor 100 has an inlet 6
(connected through a wastewater distribution manifold, not shown)
and an associated air release volume shown directly beneath each
reactor chamber. Inlet 6 empties directly into the interior of each
reactor chamber 100 and an outlet 7 draws water from the quiescent
zone 4 for discharge from the treatment system. Each reactor has
growth media 200 positioned in the reactor with discrete air
release locations 300 positioned below the reactor 100 A discrete
air release locations.
[0049] In FIG. 2B, a top and side cross-sectional view of a
rectangular tank 1 is shown with clarifier sidewall 2 partitioning
the tank volume into two adjacent rectangular volumes, the
clarifier volume being the quiescent zone, and the dilution zone.
Located in the dilution zone portion is the reactor 100, with the
interior of the reactor forming the mixing zone 3. The air release
volume is positioned below the reactor. As shown, the clarifier
sidewall 2 stops before reaching the bottom of the tank, allowing
fluid communication across the clarifier sidewall 2 (the clarifier
sidewall 2 in this embodiment is typically sloped to create a zone
having larger volumes near the water surface than below the water
surface). Also shown is a deflection plate 500 positioned at the
bottom of the portion of the tank partition remote from the reactor
100 to re-direct solids settling out of this zone back into the
area of the tank containing the reactor chamber.
[0050] Shown in FIG. 2C is a square tank 1, with a four sided
sidewall 2 forming a pyramidal shaped truncated open bottom frustum
clarifier. Shown within the clarifier interior is a reactor chamber
100, air release locations 300 positioned below the media 200
located in the reactor chamber 100, and an inlet 6 (emptying into
the top of the reactor chamber) and outlet 7 located in the
quiescent zone interior to the clarifier. The air distribution
system is not shown in FIGS. 2A and 2C for clarity. The reactor
chamber is positioned above the tank bottom and can be supported
from the bottom of the tank (by using a stand), or supported from
the top area or sides of the tank (or clarifier side wall) by the
use of brackets or the like.
[0051] As shown, the invention can conveniently and economically be
incorporated into a variety of existing treatment systems, such as
by a converting septic (or anaerobic) system into an aerobic system
through incorporation of the growth media reactor and air injection
system. Alternatively, the invention can be incorporated into a
Hansel type aerobic system, as shown in FIGS. 1A, 2A-2C. In these
types of aerobic systems, the reactor can be placed in the
clarifier or external to the clarifier.
[0052] Common features of these treatment systems are inlet 6 which
brings wastewater into the mixing zone (and more preferred,
discharging into the mixing zone above the water level in the
mixing zone) while outlet 7 removes treated waters from the
treatment system external to the mixing zone, either the quiescent
zone or the dilution zone. Additional common features are the
placement of air release locations 300 below the reactor chamber
100 to create the air release volume. It is necessary that air
diffuse upwardly through the reactor chamber. Releasing air to
diffuse upwardly through the reactor provides direct contact of
oxygen with the active biomass growing on the growth media within
the reactor. Such direct contact promotes efficient (a) oxygen
intake, (b) microbial metabolism and (c) degradation of waste
matter in the wastewater. While some released air may also flow
around the exterior of the reactor chamber (in which case there
would be no quiescent zone), it is not preferred.
[0053] When the tank is operational, the tank will have a water
level 8, generally defined by the level of the outlet discharge.
The reactor chamber has an outer sidewall 101 which is positioned
above the water level and is constructed of materials near the
water level to substantially fluidly isolate the mixing zone 3 and
the quiescent zones 4 (or the dilution zone if the reactor is
placed in the dilution zone) near the water level 8 in the tank.
The growth media 200 positioned in the reactor 100 is generally
located below the water level 8. It is desired that a majority of
the wastewaters entering the system from inlet 6 traverse into the
mixing zone for treatment, rather than entering the dilution zone.
This allows for direct contact of the high strength waters with the
biological mass in the mixing zone 3 prior to dilution. For this
reason, it is desired that the outer sidewall 101 substantially
fluidly isolate the mixing zone 3 from waters exterior the mixing
zone 3 near the water level 8 of the chamber. Some leakage through
the sidewall is possible, but not preferred. However, leakage
through the sidewall at locations distant from the inlet is more
tolerable. In certain designs, substantial leakage is allowed, for
instance where the top portion of the mixing zone 3 is partitioned,
as later described.
[0054] When a growth media reactor 100 is included within a
clarifier structure (as shown in the previous embodiments, FIGS.
1A, 2A-2C), it may be desirable for the growth media reactor 100 to
dispense with a separate sidewall 101 and use in its place the
clarifier sidewall 2 as the outer chamber wall 101 (that is, the
sidewall of the clarifier can function as the outer wall or
sidewall of the growth media reactor, for instance, where the
reactor occupies much of the internal space of the clarifier). The
clarifier sidewall extends above the water surface and is
impervious to wastewater (in the sense that wastewater cannot flow
through the sidewall) and hence has the desired properties of a
reactor sidewall.
[0055] An alternative to above mentioned treatment systems is shown
in FIG. 3A and 3B. FIG. 3 represents a "stand alone" reactor in a
treatment system, not utilizing or incorporating a separate
clarifier structure. In this embodiment, the treatment tank has
three recognizable volumes or zones: (1) the mixing zone interior
to the reactor; (2) the air release volume, the volume generally
below the reactor where air is released or injected into the
treatment system; and (3) the remainder of the treatment tank,
considered the dilution zone. As shown in FIG. 3A, the growth media
reactor 100 has an outer sidewall 101 forming a chamber having a
substantially opened top 103 and bottom 104. Also shown is
recirculation means 700 later described.
B. The Growth Media Reactor
[0056] For the embodiment of FIG. 3A, the growth media reactor 100
has an outer wall or outer sidewall 101 which extends above the
upper surface of the media positioned within the reactor extends
above the water level 8 in the treatment system. As indicated
above, the outer walls 101 substantially fluidly isolate the top
portion of the mixing zone 3 from the other surface waters in the
tank, that is tank waters exterior to the mixing zone 3 do not
substantially communicate with the mixing zone 3 thorough the top
portion of the reactor chamber. In general, the sidewall will be
impermeable to wastewaters along the entire length of the
sidewalls. In FIG. 3A, the mixing zone 3 is in fluid communication
with the remainder of the treatment system through the open bottom
104 of the outer walls 101 of the growth media reactor 100. Inlet 6
is positioned to release waters into the top of the growth media
reactor 100. Located in the interior of the growth media reactor
100 is the growth media 200 which provides the attachment surfaces
to which colonies of bacteria adhere to. It is preferred that the
upper surface of the growth media 200, positioned within in the
reactor walls 101, be below the water level 8 to allow for
distribution of incoming wastewater across at least a portion of
the top surface of the reactor.
[0057] If the growth media 200 is formed from impervious panels,
the outer walls 101 of the growth media reactor 100 may be
partially or wholly formed by panels (shown in FIG. 8B). Positioned
below the growth media 200 in the growth media reactor 100 is the
air release sites or sites 300. As shown in FIGS. 3A and 3B, six
air release sites 300 are provided and are distributed near the
bottom portion of the reactor 100 close to the bottom surface of
the growth media 200 (again, the air distribution manifold is not
fully shown).
[0058] In all embodiments, the inlet 6 empties into the top portion
of the growth media reactor 100 which is isolated from the adjacent
surface waters of the quiescent zone or dilution zone by the
sidewall 101 or outer wall of the mixing zone. This inlet location
is desired to insure that inlet waters, upon entering the treatment
system, pass through a substantial portion of the growth media
prior to entering the dilution zone to be diluted with the large
volume of water present in the dilution zone. In this fashion,
incoming high-strength (high BOD) wastewaters will be exposed to
the biomass for more efficient treatment than would be possible
with diluted (lower BOD) wastewater if the inlet were located in
the dilution zone.
[0059] An additional feature shown in FIG. 3A is that the outer
walls 101 of the reactor chamber 100 extend downwardly past the air
release locations 300. This aspect of the device "shields" the air
release locations or the air release volume from the dilution zone
(or quiescent zone) to insure that air released at the release
locations travel through the mixing zone 3 and not elsewhere. This
shield or skirt portion 105 may be a separate structure attached to
the growth media reactor, the air distribution manifold or other
structure, or dispensed with all together.
[0060] Growth media 200 is positioned slightly below the water
surface 8 in the growth media reactor 100 (approximately 1-2 inches
below the surface, although greater depths could be used). This
placement of the growth media 200 allows the incoming wastewaters
to be distributed across a large portion of the top surface of the
reactor allowing the incoming waters access to a large portion of
the reactor volume for "presentation" to the biomass in the reactor
volume for treatment. While not preferred, the growth media 200 may
be positioned at the water level 8 and mixing and distribution
across the top surface will be accomplished by upwardly flowing
currents induced by air released from the air release
locations.
[0061] Shown in FIG. 4 is another embodiment of the reaction
chamber 100. In this embodiment, the reactor chamber has a top 110
and a bottom section 130, and the air release volume 120 is located
within the reactor between the top and bottom sections. Disposed in
portions of the top and bottom sections are growth media. Located
in the intermediary section 120 are the air release locations or
site(s) 300. It is preferred that growth media 200 substantially
fill the top section 110, but may not necessarily fill the bottom
section 130. The growth media 200 disposed in the top section 110
and the bottom section 130 may have different characteristics.
C. The Growth Media
[0062] Growth media 200 is media that provides a surface area for
bacteria/microbes to attach and grow on to develop an active,
thriving biomass. The growth media is positioned within the growth
media reactor 100. It is preferred that the growth media be
positioned in the growth media reactor below the water level in the
mixing zone, as shown in FIGS. 2 and 3.
[0063] Preferred growth media is a fixed channel media consisting
of a series of fixed corrugated panels. As used herein, "fixed
channel media" is used to define a growth media that creates
spatially fixed paths where the path is spatially invariant as
opposed to a spatially variant path as would be present when the
growth media is free floating loose media, such as disclosed in
U.S. Pat. No. 5,911,877 (FIG. 3) to Perez (incorporated by
reference). "Fixed channel cross-flow media" means a fixed channel
media where a particular channel or path is in fluid communication
at locations along a portion of the channel length with at least
one adjacent or near by channels. Non-cross flow fixed channel
media would hence be fixed channels with substantially no fluid
communication between adjacent or nearby channels along the
channel's length. Types of fixed channel media are disclosed in
U.S. Pat. No. 5,217,788 and 5,384,178, herein incorporated by
reference.
[0064] One type of fixed channel media are corrugated panels
positioned in a vertical orientation so that the corrugations
created a plurality of fixed upwardly orientated channels or
pathways through which air, when released under the panels, travels
upwardly through the channels to the surface waters in the mixing
zone. Two types of fixed channel growth media are preferred, that
being cross flow media and vertical flow media manufactured by
Brentwood Industries of Reading, PA. Both types of media are
composed of a series of corrugated plastic panels as described in
the Brentwood brochures, incorporated by reference.
[0065] In the Brentwood cross flow media shown in FIG. 5A (an edge
on view), each corrugated panel 1000 has corrugations 1100 placed
at an angle to the vertical (in one embodiment, the angle is about
45-60 degrees degrees). As shown in FIG. 5B, adjacent panels 1000
are positioned in a mirror image arrangement so that the
corrugations on adjacent panels are orientated in the opposite
direction from the adjacent panels (for instance, if one panel has
corrugations at +60 degrees from the vertical, the next panel [if
the angle is kept constant] would have corrugations orientated at
-60 degrees from the vertical). This arrangement is accomplished by
"flipping" or rotating adjacent panels about the vertical
centerline, demonstrated in FIG. 5B.
[0066] This arrangement of adjacent sheets creates a criss-crossing
pattern of opposed corrugations on adjacent sheets. Each
corrugation creates an upwardly directed fixed channel which
crosses or opens into a series of opposed corrugations formed by
the adjacent panel. Each channel or corrugation is in fluid
communication with each crossing channel or corrugation of the
adjacent sheet. Hence, air released beneath adjacent sheets will
take a zigzag path through the opposing sheets, eventually to reach
the surface water. Such a zigzag path allows released air to be in
contact with the growth media for a longer period of time,
promoting oxygen transfer to the biomass. The zigzag pattern also
promotes mixing/redistribution of the wastewater within the
media.
[0067] The panels are sufficiently rough or roughened to provide an
attachment surface for bacteria. Other types of fixed panel or
fixed channel designs will also provide upwardly directed channels
with crisscrossing paths. For instance, panels constructed with
discrete indentations or dimples 60 orientated along an angle, as
shown in FIG. 7, will also provide a zigzag path with fluid
communication across the entire width of adjacent panels. It may
also be desirable to have fluid communication between adjacent
panels, such as by providing cutouts in the panels.
[0068] Another type of fixed channel media is the Brentwood
vertical flow panels shown in FIG. 6 and FIG. 12. The panels in
FIG. 6 have substantially vertically orientated corrugations half
way up the panel (the bottom), with the second half of the panel
being substantially planar without corrugations (the top). Adjacent
panels are placed with the top of one placed adjacent the bottom of
the adjacent panel, as indicated in FIG. 6B. The panels in FIG. 12
depict a second panel which creates vertically orientated flow
paths when combined with additional panels, as shown in FIG. 13.
Vertical flow panels can also be formed from discretely formed
channels (such as tubes) and stacked together to create a honeycomb
of vertical channels. The corrugations can be at an angle from the
vertical, or substantially vertically formed, as shown in FIG. 6B
and FIG. 12. Vertical flow channel media allows the upward travel
of air released below the media to proceed with few changes of
direction, that is, with few zigzag paths available. Obviously, if
the vertical paths are orientated on an angle, the upward path of
air will be angular, but generally not a zigzag path as would occur
in cross flow media. As used herein, "vertical flow fixed channel
media" is used to define a growth media that creates spatially
fixed channels substantially vertically orientated. Such media may
have some sharp channel path directional changes, such as embodied
by the Brentwood Industries vertical flow media.
[0069] When fixed channel media is employed, the outer walls 101 of
the growth media reactor 100 may be formed from the panels of the
fixed channel growth media. For instance, if using a cube formed
from a series of the cross flow media panels, the two terminal side
panels 108 will form two outer opposing walls (non-porous along the
length). The remaining two side walls of the reactor can be formed
from two panels 107, vertically orientated, but orientated at 90
degrees for the remaining panel media, as shown in FIG. 8B. In this
case, it is preferred that the four panels composing the outer side
walls (107 and 108) of the reactor extend vertically above the
horizontal level of the remaining panels to fluidly isolate the
interior of the growth media reactor near the water level from the
exterior volume adjacent to top of the growth media reactor.
Because this is fairly cumbersome to construct, the growth media
may be placed in a separate open top and bottom plastic or
fiberglass chamber.
[0070] Shown in FIG. 9 is a top view of a growth media reactor 100
having a series of parallel sheets 200 as growth media. As shown,
portions 500 of the sheets in the reactor 100 extend above the
water level (those portions shown in solid lines are located above
the water level, while the dotted lines represent those portions
below the water line), creating a partitioning of the surface
waters in the media reactor. By suitable placement of some portions
of the sheeted growth media above the water level, a designer can
direct the surface flows through the growth media reactor in a
desired pattern. For instance, a partition could be employed to
divide the top of the mixing zone into two halves that are
substantially fluidly isolated from each other. In this instance,
one half would receive influent from inlet 6 and the other half
would not. The half that did not receive influent directly from the
inlet 6 would not need to be fluidly isolated from the dilution
zone near the surface waters.
[0071] Other types of growth media can be used. For instance,
instead of corrugated sheets of solid plastic, fiberglass sheets
can be used or other type of fixed film media. Corrugated sheets
formed from a porous or semi-porous material could also be
utilized, such as semi-porous stiff foam. Such semi-porous sheets
provide for some degree of fluid communication through the sheet
and also provide additional locations for bacteria to attach and
grow.
[0072] As shown in FIG. 2A, air release locations 300 are
positioned below the growth media to allow released air to travel
up and disperse through the growth media. Several air release
locations 300 are shown. The released air creates a circulation
pattern within the growth media reactor 100: released air is
entrained in rising waters to create an upward flow through the
growth media reactor. When the upward flowing waters reach the
surface of the growth media reactor, the waters must flow downward
back through the growth media reactor as the top volume portion of
the growth media reactor is fluidly isolated from the other surface
waters in the treatment system. Waters exit the reactor from the
bottom volume of the reactor (either through the open bottom of the
reactor, or through downward flow paths which open on the sides of
the reactor). Portions of the downward flowing waters, upon exiting
the growth media, will be re-directed upward by the induced upward
current created by the released air to pass again through the
growth media reactor for further treatment. The remaining portions
of the downward flowing waters will enter the dilution zone. A
circulation pattern is thus established within the reactor, and
indeed, the current induced by the air injection will induce an
overall circulation pattern in the treatment system. The current
induced within the treatment system will eventually bring waters
remote from the mixing chamber (that is, within the dilution zone
and the quiescent zone, if present) back to the reactor for further
treatment. How quickly remote waters are returned to the reactor
depend on the strength of the induced current. The strength of the
induced current will depend on the ability of the released air and
entrained waters to flow through the reactor chamber. In general,
the more circuitous the route through the reactor chamber, the
weaker the induced current (for a given air injection rate).
Additionally, if the channels in the fixed channel media are small
or the released air not flowing at a sufficient rate, a weak
current will be induced. If the induced current is too weak,
insufficient mixing throughout the entire wastewater treatment
system may occur. That is, the induced current may be too weak to
timely bring waters in the treatment system remote from the reactor
to the reactor for treatment. In this instance, a recirculation
means may be employed.
[0073] A recirculation means recirculates waters from the dilution
zone back into the treatment chamber. One recirculation means is
shown in FIG. 3. In this embodiment, the recirculation means 700
includes a tube or pipe with open ends, one end (the suction end
602) being placed in the dilution zone, and the other end 603 will
empty into the top of the reactor. As shown, the discharge end 603
is shown placed above the water level in the top of the reactor.
The discharge end could also be placed below the water level in the
reactor. If the treatment system includes a clarifier, it is
preferred that the suction end of the recirculation means be
positioned in dilution zone, not the quiescent zone. Location of
the suction end 602 is not critical, but it should not be too close
to the bottom (to avoid sucking in bottom sludge) and it is
desirable that the suction end be remote from the outlet or
discharge 7. It is desired that the water volume near the outlet be
calm (to allow suspended solids to settle out prior of the waters
prior to discharge), and hence, the suction end should be remote
from the outlet 7. The suction end 602 can be placed adjacent to
the bottom of the reactor chamber but removed from the air
injection volume.
[0074] Alternatively, to create supplemental flow through the
reactor, an existing air release location located underneath the
reactor could be used. In this instance, a vertical flow channel (a
2 inch cross section pipe, for instance) would be placed through
the reactor and located above the selected air release site. Such
an arrangement is shown as reference 800 in FIG. 2A.
[0075] Air from the compressor or other source is injected into the
air lift tube 601 near the suction end 602. Air can be drawn from
the air distribution manifold, such as by a flexible hose or fixed
tubing, for this purpose. The injected air will rise up with
entrained water to empty into the top of the rector chamber
creating an addition flow of waters into the top of the reactor.
Because the suction end 602 is located in the dilution zone, it is
desired that substantially all air injected into the air lift tube
601 remains within the tube and does not escape into the quiescent
zone.
[0076] If supplemental recirculation is needed, use of the air lift
pump as a recirculation means is convenient and efficient as the
present treatment system uses air for injection into the system
under the reactor media and the air distribution manifold can be
tapped for delivering air into the recirculation pipe. Obviously,
other types of pumps could be used to drive a recirculation means,
such as a centrifugal pump. Using a recirculation means, a
supplemental current is created in the dilution zone to help cycle
waters in this zone back through the reactor chamber for further
treatment.
[0077] The induced current also induces a circulation pattern in
the mixing zone, that is, within the interior of the reactor:
upward flow along a first portion of the growth media reactor and
downward flow in a second portion of the growth media reactor. This
pattern may not be stable, but vary over a period of time. However,
by suitable choice of airdrop placement and/or selection of types
of fixed media channels, the reactor unit can be designed to
produce a fairly stationary current pattern within the reactor
volume: a portion of the reactor designed for upward flow, and a
portion designed for downward flow.
[0078] It may be desirable to vary the characteristics of the
growth media in the growth media reactor 100 to take advantage of
the circulation pattern within the reactor. For instance, a mixture
of both vertical and cross flow fixed channel media in the reactor
chamber can be utilized, with cross flow fixed channel media 525
positioned below and adjacent to the air release locations, and
with vertical flow fixed channel media 550 positioned elsewhere in
the growth media reactor, one such embodiment is shown in the top
view of the reactor shown in FIG. 10. In this embodiment, air
injection occurs below cross flow media 525 and hence upward flows
of waters will occur substantially in the cross flow media 525.
Downward flow occurs in the center of the reactor through the
vertical flow media 550. The velocity of the upward flow is
determined by the rate of air injection, the number of injector
locations, and the type and volume of the media employed. The down
flow rate is dependent upon the type and volume of media employed
for down flow in relationship to the volume of upward flow
(obviously the upward flow must equal the downward flow). For
instance, by enlarging the middle volume of the reactor chamber in
FIG. 10, the down flow rate through the center can be slowed.
[0079] Using two different media characteristics for the two flow
paths allows the designer to tailor the reactor's growth surfaces
for different properties of the upward flowing and downward flowing
waters. Waters flow upward with entrained air providing increased
mixing and oxygen transfer and some scouring of the growth media
walls by the rising air bubbles. Waters descending through the
reactor lack entrained air bubbles, and hence, less scouring of the
walls will occur on the portions of the growth reactor
accommodating downward flow. With less scouring and/or possible
decreased downward flow velocity, the minimum cross sectional area
of the downward flowing channels can be increased (with respect to
the media accommodating upward flow) to accommodate heavier build
up of bacterial growth, or build up of an alternate type of
bacterial growth.
[0080] A pretreatment tank can be placed in series with the current
wastewater treatment system, with waters from the pretreatment tank
delivered to the mixing zone. Additionally, a post-treatment tank
can also be utilized in series with the output of the present
wastewater treatment system, with waters from the quiescent or
dilution zone being the input to the post treatment tank, such as
discussed in Cormier, U.S. Pat. No. 6,093,316, incorporated herein
by reference.
D. Operation
[0081] While the fixed media growth reactor is highly efficient due
to the high concentration of treating biomass (it is estimated that
a single pass through the system may remove as much as 70% of the
wastes), treatment requires a cycling of waters through the
reactor. In most applications, the present treatment system
operates in cycles: incoming wastes do not enter the system in a
continuous flow, but enter the system in pulses or doses. For
instance, in home systems, the system will be pulsed during the
mornings and the evenings when bathrooms are heavily utilized.
During the day, the treatment system may not be pulsed at all, or
pulsed infrequently. Alternatively, input to the treatment system
may be accomplished from a pretreatment dosing tank, wherein a
dosing pump operates to pump waters to the treatment system when
the waters in the dosing tank exceed a given level.
[0082] When the system is being pulsed, incoming wastes will be
directly fed to the reactor for efficient treatment. When not being
pulsed (that is, the system is dormant), it is desirable to
continue treating the fluids in the treatment system, that is,
treat the waters in the mixing zone and the dilution zone. In these
dormant periods the treatment system continues to operate to treat
the water in the system by drawing wastes to the reactor for
treatment by cycling waters through the reactor though injection of
air at the air release sites (generally, air is continuously
injected into the system, unless trying to induce a period of low
oxygen levels to achieve denitrification).
[0083] The dilution zone should be sufficient to buffer the waste
strength of incoming wastewaters, and the size needed will depend
upon the effluent standards to be achieved. In large treatment
systems (over 100,000 gal/day) with current EPA secondary guideline
effluent standards (BOD=30mg/liter TSS=30mg/liter), it is believed
that the ratio of reactor volume to tank volume should generally be
under 0.50 as the influent approximates a continuous flow (however,
this has not been tested). Further, in large scale municipal type
treatment facilities, even with sufficient dilution zone capacity,
it is believed that the volume of media required to effectively
achieve EPA secondary guideline effluent standards becomes less
cost effective than other technologies.
[0084] As new influent enters the treatment system on the top
surface of the reactor, the new influent must thus pass through the
reactor and come into contact with the active biomass (at least
once on the downward flow). This is substantially different from
treatment systems where influent enters the system elsewhere in the
treating system, as entry elsewhere implies that the influent is
mixed with other wastewater and effectively diluted prior to
treatment. The diluted wastewaters now take longer to treat. For
instance, if incoming wastewaters are diluted by a factor of 10
before entering the treatment reactor, then it will take 10 times
longer to treat the same amount of wastes, as now ten times the
wastewater must pass through the reactor to present the same wastes
to the biomass (this is somewhat simplistic, as it assumes complete
mixing).
[0085] The present system relies upon direct contact and dilution
to meet treatment standards. The dilution zone acts to absorb and
dilute wastes after new influent passes at least once through the
reactor, allowing the overall system (reactor and dilution
zone/quiescent zone waters) to meet wastewater effluent standards.
For instance, assume 300 BOD wastewaters are influent, a 70%
efficiency for the reactor, and dilution in the larger dilution
zone by a factor of 10. Also assume effluent standard is 25 BOD
(Biological Oxygen Demand --a measure of waste strength, other
standards also come into play, such as Total Suspended Solids
(TSS), nitrate levels, fecal coliform levels, etc). If 300 BOD
waters were positioned in the dilution zone prior to entering the
reactor, the dilutive effect results in an average BOD of 30
(factor of ten dilutions). Contrast these levels with that of the
present system, where the 300 BOD waters passes through the
bioreactor once and the resulting BOD, after a single pass of the
influent through the reactor, would be reduced to 90 BOD (70%
efficiency (the higher reactor efficiency is attributable to
aeration under the reactor and the ability present high BOD wastes
to the biomass without dilution effects)). After dilution of this
preliminary treated water, the strength of the waters in the
treatment tank is now 9 (factor of ten dilutions). Hence, in this
instance, the treatment system increased performance by a factor of
3, making effluent standards more readily achievable.
[0086] In period of low flows (or the system at rest), the system
cycles waters through the reactor to remove wastes, dropping the
waste levels in the wastewater and preparing the system for the
next pulse of high strength wastewaters. In period of influent, the
high strength incoming influent shocks the system by raising
overall BOD levels, but the high BOD waters are treated initially
in the reactor and the remaining wastes are diluted in the
quiescent zone allowing the system to absorb the shock and to
maintain effluent standards. If the system had no periods of rest
(low or no influent), wastewater BOD levels (and other pertinent
performance characteristics) would slowly rise in the tank despite
efficient treatment by the bioreactor, as the system can not "keep
up" or process the continuous influent quickly enough. At some
point, the system would fail to meet effluent standards.During the
rest periods, the treatment system "recovers" from a prior period
of influent by continuing to treat the diluted wastewater reducing
further the BOD levels without having to treat new influent.
Obviously, a larger dilution zone (larger volume) allows the system
to adapt to longer influent flows or higher strength influent flows
and still maintain effluent standards. Hence, in systems where flow
approximates a continuous flow, additional treatment is desirable
(more reactor volume) and additional dilution zone is also
desirable.
[0087] As described, the reactor could be utilized with no
clarifier structure or an internal clarifier. One embodiment
structured as in FIG. 3 used a 700 gallon tank (system capacity of
treating about 500-700 gallons/day of typical domestic strength
wastewater (180-300 BOD, and TSS) with a 2'.times.2'.times.4' block
of fixed channel media (placed in a 2'.times.3'.times.4' chamber to
isolate the top of the media from the quiescent zone), utilizing
six air release locations (release was effected through 3/4 PVC
tubing) connected to a compressor running at six c.f.m. Good
quality effluent was obtained over an extended period. More
recently, higher flow rates have been utilized (15-20 c.f.m).
Higher flow rates induce more active mixing and more efficient
oxygen transfer, however, too high a flow rate will result in
scouring of the bacterial mass from the growth media. Flow was
induced by air injectors located about two inches below the bottom
of the reactor, and the reactor was positioned about 19 inches from
the bottom of the tank floor. The system was also run using a
single supplemental air lift pump for recirculation, producing a
supplemental flow of 10 gallons/minute into the top of reactor
(tapping the existing air manifold and using a 2 inch pipe as the
airlift tube). Using the supplemental air lift pump, it was found
that the treatment center more readily meet requirements for
start-up and vacation. For a 2'.times.2'.times.4' reactor, tank
sizes in the 200-2100 gallons range should produce a reasonable
treatment effluent quality; and in general, for a given reactor
volume, the ratio of reactor volume to total volume in the range of
about 0.05 to about 0.6 (and potentially to 0.75) should produce a
reasonable treatment effluent quality.
[0088] For larger applications (one using multiple
2'.times.2'.times.4' reactor unit blocks), it may be desirable to
split the inlet 6 into several feed pipes to more evenly distribute
the incoming wastes across the top surface of the mixing zone. The
placement of the reactor in the tank volume is not critical,
however, it is desirable that the air injectors not be place too
close to the tank bottom, particularly for flat bottomed tanks. The
tank bottom serves as sludge storage area for the treatment system.
If air injection takes place near the tank bottom, the bottom of
the tank will be subject to currents and little space will be
available for sludge storage (requiring a quiescent zone for
deposition), as the sludge will tend to remain suspended, and
thereby raising the TSS levels of the effluent. It is believed that
for flat bottomed tanks, the injectors should be at least 6 inches
off the bottom, with 12-20 inches more preferred.
[0089] As can be seen, feeding the reactor from the top of the
reactor chamber forces the wastewater to pass through the reactor,
allowing for the wastes to be directly contacted with the
biological mass prior to significant dilution. However, it is also
possible to achieve similar contact by "feeding" the reactor near
the air injectors. The air injectors create an "updraft" or
upwelling current, and hence, by feeding influent into the tank
near the air injectors, the updraft will draw the incoming
wastewaters from the influent pipe and direct a portion of such
waters into the reactor chamber. Possible locations for the
influent terminus include locations in the dilution zone to the
side of the air injectors or below the air injectors.
Alternatively, the influent terminus could be located above the air
injectors but below the reactor chamber. Finally, while not
preferred, the influent terminus could be positioned in the
interior of the reactor chamber. For the influent discharging into
the dilution zone, it is preferred that the influent terminus or
discharge end location be positioned so that a substantial amount
(over 50%) of the incoming influent will be drawn into the mixing
zone by action of the air injectors. FIG. 11 shows a volume near
the air injectors (shown by the dashed line) for the location of an
inlet terminus or discharge site(s) for a "bottom fed" reactor.
Note that the possible volume is skewed near the side of the
reactor closest to the discharge or outlet location. This is to
minimize the potential of a short-circuit, that is, influent
entering the system and reaching the outlet prior to passage
through the mixing zone. Finally, if the reactor is bottom fed, is
it not necessary that the top of the reactor remain substantially
fluid isolated from the remaining surface waters, however, such an
arrangement is preferred.
[0090] Other uses and embodiments of the invention will occur to
those skilled in the art, and are intended to be included within
the scope and spirit of the following claims.
* * * * *