U.S. patent application number 17/173515 was filed with the patent office on 2021-07-29 for treatment using fixed film processes and ballasted settling.
This patent application is currently assigned to Evoqua Water Technologies LLC. The applicant listed for this patent is Evoqua Water Technologies LLC. Invention is credited to Nathan Antonneau, Robert Backman, Andrew G. Bishop, Timothy Lindemann, Todd Schwingle, Michael Casey Whittier, Steven E. Woodard.
Application Number | 20210230033 17/173515 |
Document ID | / |
Family ID | 1000005523192 |
Filed Date | 2021-07-29 |
United States Patent
Application |
20210230033 |
Kind Code |
A1 |
Antonneau; Nathan ; et
al. |
July 29, 2021 |
TREATMENT USING FIXED FILM PROCESSES AND BALLASTED SETTLING
Abstract
A system and method is provided for water and wastewater
treatment. The system comprises a fixed film biological process and
a ballasted flocculation process.
Inventors: |
Antonneau; Nathan;
(Wauwatosa, WI) ; Lindemann; Timothy; (Jefferson,
WI) ; Schwingle; Todd; (Franklin, WI) ;
Whittier; Michael Casey; (Waukesha, WI) ; Woodard;
Steven E.; (Cumberland, ME) ; Backman; Robert;
(Wayland, MA) ; Bishop; Andrew G.; (Windham,
ME) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Evoqua Water Technologies LLC |
Pittsburgh |
PA |
US |
|
|
Assignee: |
Evoqua Water Technologies
LLC
Pittsburgh
PA
|
Family ID: |
1000005523192 |
Appl. No.: |
17/173515 |
Filed: |
February 11, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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14405175 |
Dec 3, 2014 |
10919792 |
|
|
PCT/US2013/032313 |
Mar 15, 2013 |
|
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17173515 |
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61658102 |
Jun 11, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C02F 3/085 20130101;
C02F 3/04 20130101; Y10T 29/49716 20150115; C02F 3/101 20130101;
C02F 2303/16 20130101; C02F 3/121 20130101; C02F 3/082 20130101;
C02F 1/481 20130101; C02F 1/56 20130101; C02F 3/08 20130101; Y02W
10/10 20150501; C02F 2101/203 20130101; B01D 21/01 20130101; C02F
2001/007 20130101; C02F 1/52 20130101; C02F 9/00 20130101; C02F
11/02 20130101; C02F 1/5245 20130101; C02F 2305/12 20130101 |
International
Class: |
C02F 3/04 20060101
C02F003/04; C02F 11/02 20060101 C02F011/02; C02F 3/10 20060101
C02F003/10; C02F 1/52 20060101 C02F001/52; C02F 3/08 20060101
C02F003/08; C02F 9/00 20060101 C02F009/00; B01D 21/01 20060101
B01D021/01 |
Claims
1. A system for treating wastewater comprising: a fixed film
reactor fluidly connected to a source of wastewater and configured
to provide a fixed film effluent; a source of ballast fluidly
connected to the fixed film effluent and configured to provide a
ballasted effluent; and a clarifier fluidly connected to the
ballasted effluent, the clarifier comprising a treated effluent
outlet and a ballasted solids outlet and configured to separate a
treated effluent from a ballasted solids.
2. The system of claim 1, further comprising a source of flocculant
fluidly connected to the ballasted effluent.
3. The system of claim 1, further comprising a source of coagulant
fluidly connected to the fixed film effluent and configured to
provide a coagulated effluent.
4. The system of claim 1, wherein the fixed film reactor comprises
at least one of a moving bed bioreactor, a trickling filter, and a
rotating biological contactor.
5. The system of claim 1, wherein the fixed film effluent comprises
about 50 mg/l to about 300 mg/l of biological solids.
6. The system of claim 1, wherein the ballast comprises
magnetite.
7. The system of claim 1, wherein the system is configured to treat
between about 200 gallons per day per square foot of a surface area
of the clarifier to about 6,000 gallons per day per square foot of
the surface area of the clarifier.
8. The system of claim 3, wherein the ballasted solids outlet of
the clarifier is fluidly connected to at least one of the
coagulated effluent and the fixed film reactor.
9. The system of claim 8, further comprising a ballast recovery
system positioned downstream of the ballasted solids outlet of the
clarifier and upstream of at least one of the source of ballast and
the fixed film reactor.
10.-20. (canceled)
Description
FIELD OF TECHNOLOGY
[0001] One or more aspects of the disclosure relate generally to
water and wastewater treatment, and more particularly to systems
and methods for water and wastewater treatment using fixed film
processes and ballasted settling.
SUMMARY
[0002] A system for treating wastewater is provided. The system
comprises a fixed film reactor fluidly connected to a source of
wastewater and configured to provide a fixed film effluent. The
system further comprises a source of ballast fluidly connected to
the fixed film effluent and configured to provide a ballasted
effluent. A clarifier is provided in the system that is fluidly
connected to the ballasted effluent. The clarifier comprises a
treated effluent outlet and a ballasted solids outlet and is
configured to separate a treated effluent from a ballasted
solids.
[0003] A method for treating a wastewater is also provided. The
method comprises introducing a source of wastewater to a fixed film
reactor to provide a fixed film effluent. The method further
comprises adding a ballast to provide a ballasted effluent. The
method further comprises separating the ballasted effluent into a
treated effluent and a ballasted solids in a clarifier, and
separating the ballasted solids into a recovered ballast and a
ballast-free solids. The method further comprises adding the
recovered ballast to the coagulated effluent.
[0004] A method for retrofitting a wastewater treatment system is
also provided. The wastewater treatment comprises a fixed film
bioreactor and a clarifier positioned downstream of the fixed film
bioreactor. The clarifier comprises a solids outlet. The method for
retrofitting comprises installing a coagulation tank in the
clarifier, and installing a ballast feed tank connected downstream
of the coagulant tank in the clarifier. The method of retrofitting
further comprises connecting the solids outlet of the clarifier to
the ballast feed tank.
DESCRIPTION OF THE DRAWINGS
[0005] The accompanying drawings are not intended to be drawn to
scale. For purposes of clarity, not every component may be labeled
in the drawings, nor is every component of each embodiment of the
disclosure shown where illustration is not necessary to allow those
of ordinary skill in the art to understand the disclosure.
[0006] In the drawings:
[0007] FIG. 1 presents a schematic of a treatment system
implementing a fixed film process, ballasted settling, and recovery
of ballast in accordance with one or more embodiments of the
disclosure; and
[0008] FIG. 2 presents a schematic of reaction tanks integrated
into a clarifier tank in accordance with one or more embodiments of
the disclosure.
DETAILED DESCRIPTION
[0009] Systems and methods are provided for treating water or
wastewater. The systems and methods may comprise treating a water
or wastewater in a fixed film reactor, also referred to as a fixed
film biological system or attached growth system. The systems and
methods may further comprise treating the effluent from the fixed
film biological system in a ballasted settling process, or a
ballasted flocculation system.
[0010] A fixed film biological system may oxidize and reduce
soluble substrate, eliminating impurities and producing solids.
Fixed film processes may maintain biological growth on a surface or
inert carrier or sheet and the treated effluent from the fixed film
bioreactor may contain about 50 milligrams per liter (mg/l) to
about 300 mg/l of biological solids. In certain embodiments, the
treated effluent may contain between about 100 mg/l to about 200
mg/l. In certain embodiments, the treated effluent from the fixed
film bioreactor may contain about 50 mg/l to about 2,000 mg/l of
biological solids Examples of fixed film processes include, without
limitation, moving bed bioreactors (MBBR's), trickling filters, and
rotating biological contactors. Typically, wastewater is filtered
through a primary or coarse screen and/or is treated in a primary
clarification unit. Effluent of these primary processes or a raw
wastewater may enter a fixed film biological system where soluble
substrate is oxidized or reduced to biological solids in the form
of slough from the fixed biomass on the inert carrier or sheet of
the fixed film reactor. Aeration may be supplied in aerobic zones
to supply oxygen and mixing to the system. In anaerobic, anoxic, or
aerated anoxic based systems, mixers or mixers with aeration may be
provided to maintain mixing throughout.
[0011] The fixed film biological system may provide an effluent
comprising biological solids, often referred to as slough, which
requires separation from a treated effluent in a downstream
process. While fixed film processes have a small footprint,
effluent biological solids from the process are often difficult to
settle with conventional sedimentation processes frequently
requiring a large settling area. Clarification, therefore, is often
the limiting step in the rate of wastewater treatment involving
fixed film biological systems or fixed film reactors.
[0012] Ballasted flocculation systems or ballasted settling systems
may comprise the addition of a coagulant, ballast, and, optionally,
a flocculant to improve the removal of dissolved, colloidal,
particulate and microbiological solids. In certain embodiments, the
coagulant may be optional. For example, ballast and flocculant may
be added, without coagulant. In other embodiments, ballast may be
added without coagulant and flocculant. In other embodiments,
ballast and coagulant may be added, without flocculant. The
precipitation and enhanced settlability of ballasted solids
provides for a small clarification step, which may allow for a
small footprint system comprising biological and clarification
steps. According to embodiments of the present disclosure,
ballasted flocculation systems may eliminate the need to provide a
secondary clarifier directly downstream of a fixed film biological
system or reactor. Further, the ballasted flocculation system may
be installed between the fixed film bioreactor and the secondary
clarifier, thereby using the existing secondary clarifier as the
ballasted flocculation clarifier and eliminating the need for a new
clarifier.
[0013] Flocculation may be a process of contact and adhesion
whereby particles and colloids in liquid such as a water or
wastewater form larger-size clusters of material. Particles may
cluster together into a floc. A flocculant may comprise a material
or a chemical that promotes flocculation by causing colloids and
particles or other suspended particles in liquids to aggregate,
forming a floc. Polymer may be used as flocculants. For example,
acrylic acid/acrylamide copolymers and modified polyacrylamides may
be used.
[0014] Coagulation may be a process of consolidating particles,
such as colloidal solids. Coagulants may include cations, such as
multivalent cations. They may include cations such as aluminum,
iron, calcium or magnesium (positively charged molecules) that may
interact with negatively charged particles and molecules that
reduce the barriers to aggregation. Examples of coagulants include
bentonite clay, polyaluminum chloride, polyaluminum
hydroxychloride, aluminum chloride, aluminum chlorohydrate,
aluminum sulfate, ferric chloride, ferric sulfate, and ferrous
sulfate monohydrate.
[0015] According to some embodiments of the disclosure, a fixed
film biological system may be used in conjunction with ballasted
clarifiers to treat water or wastewater. The systems and methods of
the present disclosure may be particularly advantageous, for
example, in treatment plants where a small footprint is required
such as, for example, a retrofit for industrial plants, small flow
plants or package plants, hybrid wastewater plants, combining fixed
film processes and activated sludge processes, and lagoon plants
requiring nitrification. Also, this combination may be used in
small flow systems that do not have significant operator interface
yet require a high quality effluent. The use of a fixed film
process in combination with ballasted settling is not limited to
the examples given. Many uses in biological and chemical treatment
of wastewater or potable water are possible.
[0016] In certain embodiments, a fixed film process followed by a
ballasted flocculation process may be utilized for biological
treatment of water or wastewater to remove at least one of nitrogen
compounds, such as nitrates, biological oxygen demand (BOD),
chemical oxygen demand (COD), and phosphorus compounds. Fixed film
processes may oxidize ammonia to nitrate and/or reduce nitrate to
nitrogen gas. Biological solids produced may then be removed in
addition to dissolved, colloidal and particulate solids by the
ballasted clarifiers. In certain embodiments, at least one of
nitrogen compounds, such as nitrates, biological oxygen demand
(BOD), chemical oxygen demand (COD), and phosphorus compounds may
be removed prior to disinfection to provide potable water or
drinking water to distribute it to a water supply grid.
[0017] Ballasted flocculation systems may comprise the addition of
a coagulant, a ballast and, optionally, a flocculant to improve the
removal of dissolved, colloidal, particulate and microbiological
solids. In certain embodiments, the coagulant may be optional. For
example, ballast and flocculant may be added, without coagulant. In
other embodiments, ballast may be added without coagulant and
flocculant. In some embodiments, ballast and coagulant may be
added, without flocculant. In certain embodiments, a magnetic
ballast may be used.
[0018] The enhanced settlability of these ballasted solids may
provide for a small clarification step, which may allow for a small
footprint system comprising biological and clarification steps.
Recirculation of solids, either ballasted solids or ballast-free
solids, to at least one of the ballasted flocculation processes,
such as the ballast mixing step, and to the fixed film process can
further enhance the reliability of the overall system. These
features may be utilized in existing wastewater treatment plants,
small flow plants or package plants, combined sewer overflow (CSO)
treatment plants, new plants that require a small footprint, hybrid
treatment plants (fixed film and activated sludge), and lagoon
treatment plants requiring nitrification. One benefit is that an
existing clarifier downstream of a fixed film process is readily
convertible to a ballasted system using the system of the present
disclosure. Conventional clarifiers may be even more readily
convertible if the ballasted system uses a magnetic material, for
example, magnetite, as the ballast.
[0019] In some embodiments of the disclosure, a system for treating
wastewater is provided. The system comprises a fixed film reactor
fluidly connected to a source of wastewater and configured to
provide a fixed film effluent. A fixed film biological system may
be employed which may comprise one or more fixed film reactors,
which are utilized in parallel or in series, and in which one or
more of the fixed film reactors is operational at a given point in
time. In certain embodiments, the fixed film effluent may comprise
about 50 mg/l to about 300 mg/l of biological solids. The fixed
film effluent may flow to a ballasted flocculation system in which
a source of coagulant may be fluidly connected to the fixed film
effluent and configured to provide a coagulated effluent. The
source of coagulant may be optional. A source of ballast may be
fluidly connected to the coagulated effluent and configured to
provide a ballasted effluent. In some embodiments, the source of
ballast may be fluidly connected to at least one of the fixed film
effluent or the coagulated effluent. The source of ballast may
comprise a powdered ballast. The ballast may not be in a liquid
such that it may be added in dry powdered form. In some
embodiments, the ballast may be added by an operator or by
machinery, such as by a dry feeder. It is to be understood that the
source of ballast being fluidly connected to the fixed film
effluent or the coagulated effluent, or to any effluent or
wastewater stream of the system, may comprise the source of ballast
may be in a dry (non-liquid) or powdered form. A clarifier may be
fluidly connected to the ballasted effluent, the clarifier
comprising a treated effluent outlet and a ballasted solids outlet
and configured to separate a treated effluent from a ballasted
solids. The ballasted solids outlet of the clarifier may be fluidly
connected to at least one of the coagulated effluent and the fixed
film reactor. In some embodiments, the ballasted solids outlet may
be fluidly connected to the source of ballast.
[0020] Optionally, a source of flocculant may be fluidly connected
to the ballasted effluent. At least one of the sources of
coagulant, ballast and flocculant may be provided in line to a
fixed film effluent stream. Alternately, tanks may be used such
that the fixed film effluent flows to a coagulant tank, into which
a coagulant is added from a source of coagulant. The coagulated
effluent may then flow to a ballast tank, into which a ballast is
added from a source of ballast. The ballasted effluent may then
flow to a flocculant tank, into which a flocculant is added from a
source of flocculant. The flocculant effluent may then flow to the
clarifier. In certain embodiments, a flocculant tank and source of
flocculant may not be included in the ballasted flocculation
system, and the ballasted effluent may flow directly to the
clarifier. In some embodiments, a coagulant tank and source of
coagulant may not be included in the ballasted flocculation
system.
[0021] As discussed above, the ballast may be a magnetic ballast.
The magnetic ballast may comprise an inert material. The magnetic
ballast may comprise a ferromagnetic material. The magnetic ballast
may comprise iron-containing material. In certain embodiments, the
magnetic ballast may comprise an iron oxide material. For example,
the magnetic ballast may comprise magnetite (Fe.sub.3O.sub.4). The
magnetic ballast may have a particle size that allows it to bind
with biological flocs to provide enhanced settling or
clarification, and allow it to be attracted to a magnet so that it
may be separated from the biological flocs. The particle size of
the magnetic ballast may be less than about 100 micrometers
(.mu.m). The particle size of the magnetic ballast may be less than
about 40 .mu.m. The particle size of the magnetic ballast may be
less than about 20 .mu.m.
[0022] Sand ballasted systems often implement larger ballast size
to effectively recover the ballast. Ballast is also non-magnetic.
Sand ballasted systems have also implemented the use of cleaning
agents to separate the biological solids from the sand particles.
This could be a result of a large surface for bacteria to attach,
requiring more than shearing forces of a vortex mechanism alone to
remove biological solids from the sand particle surface, or the
need to dissolve chemical bonds that assist in the binding of the
ballast.
[0023] Unlike sand based ballast that requires growth of floc
around relatively large size sand particles, magnetite ballast can
be used with small size, such as less than about 100 .mu.m,
allowing for the magnetite particles to impregnate existing floc.
The result may be an enhanced separation of flocculants. The
ballasted effluent or the flocculant effluent may be directed to at
least one clarifier where ballasted solids, such as magnetite
ballasted solids, may be removed by gravity at an enhanced rate
greater than conventional gravity clarifiers. The clarifier, being
configured to provide a treated effluent and a ballasted solids,
may be fluidly connected to at least one of the source of ballast,
the coagulated effluent, and the fixed film reactor. In certain
embodiments, the ballasted solids outlet of the clarifier may be
fluidly connected to at least one of the coagulated effluent and
the fixed film reactor. This may allow at least a portion of the
ballasted solids to return to the fixed film biological system and
to the source of ballast, for example, the ballast tank connected
to a source of ballast. A portion of the biological solids may also
be removed from the system. This may involve utilizing a magnetic
separation apparatus, which may allow recovery of magnetic
particles, which would not be feasible with, for example, sand
particles. In certain embodiments, mechanical shearing may be
employed to shear the biological solids prior to ballast recovery,
for example, prior to magnetite recovery. In some instances, such
as re-seeding and high flow events, a portion of the settled
biological solids may be recycled to the front of the fixed film
system. These solids may either be ballasted or solids stripped of
magnetite through the magnetic separation. In certain embodiments,
such as small-scale operations, it may not be necessary or feasible
to recover the ballast, such as the magnetic ballast from the
system.
[0024] In certain embodiments, the system may be configured to
treat between about 200 gallons per day per square foot of a
surface area of the clarifier to about 2,000 gallons per day per
square foot of the surface area of the clarifier. In certain
embodiments, the system may be configured to treat between about
200 gallons per day per square foot of a surface area of the
clarifier to about 6,000 gallons per day per square foot of the
surface area of the clarifier. In certain other embodiments, the
system may be configured to treat between about 100 gallons per day
per square foot of a surface area of the clarifier to about 36,000
gallons per day per square foot of a surface area of the
clarifier.
[0025] In certain embodiments, a ballasted recovery system may be
positioned downstream of the ballasted solids outlet of the
clarifier. The ballasted recovery system may be positioned upstream
of at least one of the source of ballast and the fixed film
reactor.
[0026] In certain embodiments, the use of a magnetic ballast
provides advantages over use of other ballast materials. For
example, the use of a magnetic ballast provides for enhanced
removal of biological solids from the ballast. For example, a
magnetic drum may be used to separate the biological solids from
the magnetic ballast. Optionally, mechanical shearing may be
utilized prior to separation. This process may sufficiently remove
the biological solids from the ballast. Recirculation of settled
solids to the reaction tanks further enhances performance and
reliability while the optional recycle to the fixed film system,
whether with ballasted or ballast-free solids, allows for
additional flexibility for treatability and recovery in process
upsets or startups. In certain embodiments, cleaning solutions may
be unnecessary in separating ballast from the biological
solids.
[0027] A system for treating wastewater is shown in FIG. 1. A
source of wastewater, stream 1, which may be screened wastewater or
primary clarification effluent, enters fixed film biological system
or fixed film reactor 4. Fixed film reactor 4 may comprise a moving
bed bioreactor, a trickling filter, or a rotating biological
contactor, for example. Soluble substrate may be oxidized or
reduced to biological solids in the form of, for example, a slough,
from the fixed biomass on an inert carrier or sheet of fixed film
reactor 4. Aeration may be supplied in aerobic zones to supply
oxygen and mixing for the reactor 4. In the case of anaerobic or
anoxic based systems, mixers can be provided to keep the system
fully mixed. Fixed film effluent 5 exits the reactor 4. Fixed film
effluent 5 comprises wastewater and solids produced in reactor 4.
Fixed film effluent 5 enters a series of feed reaction areas which
may be inline or utilize tanks.
[0028] Source of coagulant 7, such as metal or prehydrolized metal
salt, is added in reaction area 6 to provide a coagulated effluent.
Following coagulation addition 6, flow continues on to ballast
reaction area 8. Source of ballast, is introduced to provide a
ballasted effluent. The source of ballast may comprise raw ballast
9, recycled or recovered ballast 10, recycled ballasted solids 11,
or combinations thereof. The ballast may comprise a magnetic
material. The ballast may comprise a ferrous material. The ballast
may comprise magnetite (Fe.sub.3O.sub.4). The ballast may be in
powdered form. Raw ballast 9, or fresh ballast, is ballast that has
not before been introduced to the waste system. Recycled or
recovered ballast 10 is ballast that is separated from solids in
another part of the system, for example, recovery system 20,
described below, and recycled to the ballast reaction area.
Ballasted solids comprise biological solids impregnated or
partially impregnated with ballast. Recycled ballasted solids 11
are ballasted solids returned to the ballast reaction area 8 from
an outlet of the clarifier 15 without first being introduced to a
recovery system 20 for separation.
[0029] After ballast addition 8, source of flocculant 13 may
optionally be added in flocculant reaction area 12 to further
flocculate solids and ballasted solids prior to being introduced
into clarifier 15. Flocculant 13 may comprise a polymer.
[0030] As discussed below, clarifier 15 incorporated into the
wastewater treatment system may be a converter or retrofitted
clarifier. The details and particular components of the clarifier
may be chosen by a person of ordinary skill in the art as required.
The clarifier may, for example, comprise lamella. The clarifier may
be configured to separate treated effluent 16 from ballasted solids
24 and comprises outlet 26 for treated effluent 16 and outlet 28
for ballasted solids. Solids settle in clarifier 15 and separated
treated effluent 16 continues on to further disinfection if
required. A portion of the settled solids may be recycled ballasted
solids 11 returned to ballast reaction area 8. In addition or in
the alternative, another portion of the ballasted solids 23 may be
recycled to fixed film system 4.
[0031] At least a portion of settled solids 17 may be introduced
into a ballast recovery system 20. Optionally, settled solids 17
may first be introduced to mechanical shearing device 19 to aid in
breaking up the ballast and non-ballast components of the settled
solids. Alternatively, the mechanical shearing device 19 may be
by-passed by stream 18. The ballast recovery system 20 may comprise
a magnetic separator. For example, the separator may be a wet drum
magnetic separator. In a wet drum magnetic separator, magnetic
ballast adheres to the surface of a rotatable drum and is directed
to a separate outlet from nonmagnetic components, or ballast-free
solids, of the feed. Stripped solids may comprise waste sludge 21
that exits the system 20 for further solid waste treatment and
disposal. A portion of these stripped solids, or ballast-free
solids, may optionally be recycled to fixed film system 4 via
optional feed line 22. It should be understood that ballast-free
solids refers to solids that have a majority portion of the ballast
removed from the solids. In some embodiments, at least about 90% of
the ballast has been removed. In other embodiments, at least about
95% of the ballast has been removed.
[0032] Additional optional components include clarifier 3 fluidly
upstream of fixed film system 4, and bypass line 2 which may allow
stream 1 to bypass fixed film system 4 if necessary, for example,
during a high flow event, such as a rainfall or storm event.
[0033] In certain embodiments of the present disclosure, a method
of treating a wastewater may be provided. The wastewater may be
treated at a of between about 200 gallons per day per square foot
of a surface area of the clarifier to about 2,000 gallons per day
per square foot of the surface area of the clarifier. In certain
embodiments, the system may be configured to treat between about
200 gallons per day per square foot of a surface area of the
clarifier to about 6,000 gallons per day per square foot of the
surface area of the clarifier. In certain other embodiments, the
system may be configured to treat between about 100 gallons per day
per square foot of a surface area of the clarifier to about 36,000
gallons per day per square foot of a surface area of the clarifier.
In certain embodiments, the rate may be an average rate over a
predetermined period of time. The method may comprise introducing a
source of wastewater to a fixed film reactor to provide a fixed
film effluent. The fixed film effluent may comprise about 50 mg/l
to about 300 mg/l of biological solids. In other examples, the
fixed film may comprise about 50 mg/l to about 2,000 mg/l. The
method may further comprise optionally adding a coagulant to
provide a coagulated effluent. In some embodiments, the coagulant
may be added to the fixed film effluent. The method may further
comprise adding a ballast to provide a ballasted effluent. In some
embodiments, the ballast may be added to at least one of the fixed
film effluent and the coagulated effluent. The ballast may comprise
a magnetic material. The ballast may comprise magnetite. The method
may further comprise separating the ballasted effluent into a
treated effluent and a ballasted solids in a clarifier. The
ballasted solids may include a small amount of residual
ballast-free solids and other residual components, as separation
processes and ballasting processes will never be perfectly
complete. The method may further comprise separating the ballasted
solids into a recovered ballast and a ballast-free solids. Once
again, the recovered ballast may also comprise some residual
non-ballast components. Likewise, the ballast-free solids may
comprise some residual ballast. The method may further comprise
adding the recovered ballast to the coagulated effluent.
[0034] The method may also further comprise adding a flocculant to
the ballasted effluent. The method may also further comprise adding
a portion of the ballast-free solids to at least one of the source
of wastewater, the fixed film effluent, and the coagulated
effluent. The method may also further comprise adding a portion of
the ballasted solids to at least one of the source of wastewater,
the fixed film effluent, and the coagulated effluent. The method
may also further comprise adding a portion of the ballast-free
solids to at least one of the source of wastewater and the
coagulated effluent. The method may also further comprise adding a
portion of the ballasted solids to at least one of the source of
wastewater and the coagulated effluent.
[0035] Wastewater treatment systems and methods such as those
disclosed above may be accomplished by constructing reaction tanks
directly inside a clarifier. This clarified unit may be constructed
as part of a new wastewater treatment system or may be constructed
as part of a retrofitting. Such a configuration may address
potential obstacles to the disclosed wastewater systems and methods
including locating the reaction tanks, and minimizing the length of
pipe run between the reaction tanks and clarifier. The tanks could
be constructed of mild steel, concrete, stainless steel,
fiberglass, or the like. Construction of reaction tanks directly
inside a clarifier would minimize the footprint and capital cost
associated with installation of the disclosed system, particularly
in cases where existing clarifiers would require modifications to
make them work better in a ballasted flocculation system. These
existing clarifiers are often oversized for the task of settling
ballasted floc, and therefore the extra space may be used to
incorporate reaction tanks by installing the reaction tanks inside
the clarifiers. This effectively reduces the hydraulic retention
time of the over-sized clarifiers, minimizes the required footprint
of the water treatment system installation, and provides the
opportunity to use common wall construction to further reduce
capital cost. Clarifiers designed for ballasted clarification do
not typically include scum collection systems, so there would be no
interference of the reaction tanks with such a system.
[0036] A schematic of an embodiment of a system is shown in FIG. 2.
System 200 comprises clarifier 205. Integrated into clarifier 205
may be coagulation tank 210, ballast feed tank 215, and
flocculation tank 220. Source of coagulant 235 may be fluidly
connected to coagulation tank 210. Source of ballast 240 may be
fluidly connected to ballast feed tank 215. The ballast may
comprise a magnetic material. For example, the ballast may comprise
magnetite. The magnetite may be in powdered form. Source of ballast
240 may be introduced to ballast feed tank 215. For example, the
delivery may be accomplished automatically through a control system
or manually. The delivery of ballast may be continuous or it may be
intermittent. Likewise, for coagulant and flocculant delivery may
be automatic or manual, and continuous or intermittent. Optionally,
source of flocculant 245 may be fluidly connected to an optional
flocculation tank 220. The flocculant may comprise, for example, a
polymer. While the present embodiment has all three tanks
incorporated into the clarifier, other combinations are possible.
For example, coagulant tank 210 may be located outside clarifier
205, and flocculant tank 220 is optional.
[0037] Similar to FIG. 1, effluent 230 may enter coagulation tank
210, which may provide coagulated effluent stream 250. Stream 250
may enter ballast mixing tank 215, which may provide ballasted
effluent stream 255. Stream 255 may enter flocculation tank 220,
which may provide flocculated effluent stream 260. Stream 260 may
then enter the clarification portion of clarifier 205. Treated
effluent stream 265 may exit clarifier 205. Meanwhile, a separate
ballasted solids stream 270 may exit clarifier 205 at a different
outlet from that of treated effluent stream 265. A portion of the
ballasted solids may be diverted to a returned ballasted solids
stream 275 that may feed ballast feed tank 215. At least a portion
of the ballasted solids stream 270 may be directed to ballast
recovery system 280. The ballast recovery system 280 may produce a
recovered ballast stream 290 which may be directed to ballast feed
tank 215. The ballast recovery system 280 may produce a
ballast-free solids stream 285, or solids waste stream, directed
for further processing or returned to a part of the waste treatment
system.
[0038] In certain embodiments of the present disclosure, a method
of retrofitting a wastewater treatment system may be provided. The
wastewater treatment system may comprise a fixed film bioreactor
and a clarifier positioned downstream of the fixed film bioreactor.
The clarifier may comprise a solids outlet. The method may comprise
installing a coagulation tank in the clarifier. The method may
further comprise installing a ballast feed tank connected
downstream of the coagulant tank in the clarifier. The method may
further comprise connecting the solids outlet of the clarifier to
the ballast feed tank. The method may further comprise installing a
ballast recovery system downstream of the solids outlet of the
clarifier and upstream of the ballast feed tank. The method may
further comprise installing a flocculation tank in the secondary
clarifier connected downstream of the ballast feed tank.
[0039] The function and advantage of these and other embodiments of
the systems and techniques disclosed herein will be more fully
understood from the example below. The following example is
intended to illustrate the benefits of the disclosed treatment
approach, but do not exemplify the full scope thereof.
EXAMPLES
Example 1
[0040] A wastewater stream from a source of wastewater was
delivered to three fixed film moving bed bioreactor (MBBR) tanks in
series after passing through coarse screening, grit removal, and a
fine screen. The screened water was pumped to the MBBR tanks at an
average flow rate of 2.1 gallons per minute (GPM). The flow then
passed through a 6 foot diameter by 7 foot deep secondary
clarifier. Samples were taken from the effluent prior to being
passed through the secondary clarifier. The samples were placed
into liter beakers with coagulant dosages of 10 to 60 ppmv, with
ferric chloride as the coagulant. Magnetite at 10 g/L was added to
each beaker. The samples were mixed for three to six minutes, and
then allowed to settle. All samples settled rapidly in 15 to 30
seconds, with settling results ranged from 0.2 to 2.9 mg/L effluent
total suspended solids. All effluent in the beakers appeared clear
at each does of coagulant.
[0041] These results may be compared to a fixed film MBBR system
that is followed by a secondary clarifier in which about 90 ppmv of
ferric chloride is used, which results in an effluent of the
clarifier having 25 to 35 mg/L total suspended solids.
[0042] These results show that using a fixed film MBBR process in
conjunction with a magnetic ballast system enhanced the quality of
the treated water, reducing the total suspended solids. This
process also required less coagulant to be used in the process.
This system provides enhanced treatment of the water as well as
provide cost savings in terms of using less coagulant than a
conventional system.
Example 2
[0043] Wastewater was processed through a treatment system
comprising a trickling filter and a secondary clarifier. The flow
rate of wastewater entering the trickling filter was about 600 GPM
to about 700 GPM. A coagulant (alum) was added to the effluent of
the trickling filter at concentrations ranging from about 100 ppmv
to about 300 ppmv. Fifty GPM of effluent from the trickling filter
was diverted to a process comprising a ballasted flocculation
system in which magnetite was added to the trickling filter
effluent.
[0044] Data regarding biological oxygen demand (BOD) was measured
for a system including a trickling filter whose effluent was either
treated in a ballasted flocculation system or a secondary
clarifier. Samples were taken over a two week period. This data is
shown in Table 1.
TABLE-US-00001 TABLE 1 BOD in Effluent after BOD in BOD in BOD in
Trickling Filter Effluent after Effluent from Feed to into
Ballasted Ballasted Secondary Trickling Flocculation Flocculation
Clarifier Sample Filter (mg/l) (mg/l) (mg/l) (mg/l) 1 75 51 3 Not
tested 2 87 46 4 22 3 81 28.1 9.55 12 4 Not tested 20.6 3.9 10 5
91.4 29.6 2.6 4
[0045] As shown above in Table 1, the BOD of the effluent after
treatment with the ballasted flocculation system was improved over
effluent that was treated with a secondary clarifier. These results
demonstrate the improved treated water product that may be obtained
by using the ballasted flocculation process over a conventional
secondary clarifier.
[0046] Data was also collected from testing using the ballasted
flocculation system and is shown in Tables 2-5.
TABLE-US-00002 TABLE 2 Total Suspended Total Suspended Total Solids
in Effluent Solids in Suspended of Trickling Filter, Effluent after
Solids in Feed going into Ballasted Ballasted to Trickling
Flocculation Flocculation Sample Filter (mg/l) (mg/l) (mg/l) 1 117
110 3 2 127 89 73* 3 110 95 3 4 40 43 4 5 45 34 2 *In this run, no
alum was added.
[0047] As shown above in Table 2, total suspended solids was
decreased substantially through use of the ballasted flocculation
process.
TABLE-US-00003 TABLE 3 Total Phosphorus from Total Phosphorus
Trickling Filter Effluent, in Ballasted going into Ballasted
Flocculation Clarifier Sample Flocculation (mg/l) Effluent (mg/l) 1
5.46 0.061 2 5.34 0.131 3 4.66 0.047 4 3.97 2.36 5 4.01 0.314
[0048] As shown in Table 3, phosphorus levels were reduced through
use of the ballasted flocculation process.
TABLE-US-00004 TABLE 4 Turbidity in Trickling Turbidity in Filter
Effluent, going Effluent after into Ballasted Ballasted Sample
Flocculation (NTU) Flocculation (NTU) 1 95 3.1 2 65 8.9 3 40 12.5 4
40 4.1 5 50 Not tested
[0049] As shown in Table 4, turbidity was reduced through use of
the ballasted flocculation system.
[0050] While exemplary embodiments of the disclosure have been
disclosed, many modifications, additions, and deletions may be made
therein without departing from the spirit and scope of the
disclosure and its equivalents, as set forth in the following
claims.
[0051] Those skilled in the art would readily appreciate that the
various configurations described herein are meant to be exemplary
and that actual configurations will depend upon the specific
application for which the system and methods of the present
disclosure are used. Those skilled in the art will recognize, or be
able to ascertain using no more than routine experimentation, many
equivalents to the specific embodiments described herein. For
example, those skilled in the art may recognize that the system,
and components thereof, according to the present disclosure may
further comprise a network of systems or be a component of a
wastewater treatment system. It is, therefore, to be understood
that the foregoing embodiments are presented by way of example only
and that, within the scope of the appended claims and equivalents
thereto, the disclosed system and methods may be practiced
otherwise than as specifically described. The present system and
methods are directed to each individual feature or method described
herein. In addition, any combination of two or more such features,
apparatus or methods, if such features, system or methods are not
mutually inconsistent, is included within the scope of the present
disclosure.
[0052] Further, it is to be appreciated various alterations,
modifications, and improvements will readily occur to those skilled
in the art. Such alterations, modifications, and improvements are
intended to be part of this disclosure, and are intended to be
within the spirit and scope of the disclosure. For example, an
existing facility may be modified to utilize or incorporate any one
or more aspects of the disclosure. Thus, in some cases, the
apparatus and methods may involve connecting or configuring an
existing facility to comprise at least one of a fixed film system,
a clarifier, and a ballasted flocculation system. Accordingly, the
foregoing description and drawings are by way of example only.
Further, the depictions in the drawings do not limit the
disclosures to the particularly illustrated representations.
[0053] As used herein, the term "plurality" refers to two or more
items or components. The terms "comprising," "including,"
"carrying," "having," "containing," and "involving," whether in the
written description or the claims and the like, are open-ended
terms, i.e., to mean "including but not limited to." Thus, the use
of such terms is meant to encompass the items listed thereafter,
and equivalents thereof, as well as additional items. Only the
transitional phrases "consisting of" and "consisting essentially
of," are closed or semi-closed transitional phrases, respectively,
with respect to the claims. Use of ordinal terms such as "first,"
"second," "third," and the like in the claims to modify a claim
element does not by itself connote any priority, precedence, or
order of one claim element over another or the temporal order in
which acts of a method are performed, but are used merely as labels
to distinguish one claim element having a certain name from another
element having a same name (but for use of the ordinal term) to
distinguish the claim elements.
* * * * *