U.S. patent application number 11/826131 was filed with the patent office on 2007-11-01 for method and apparatus for nitrogen removal and treatment of digester reject water in wastewater using bioagumenation.
Invention is credited to Walter F. JR. Bailey, Leonard Benson, Timothy Constantine, Glen T. Daigger, Dimitrios Katehis, Sudhir N. Murthy, Thomas E. Sadick.
Application Number | 20070251868 11/826131 |
Document ID | / |
Family ID | 38002676 |
Filed Date | 2007-11-01 |
United States Patent
Application |
20070251868 |
Kind Code |
A1 |
Bailey; Walter F. JR. ; et
al. |
November 1, 2007 |
Method and apparatus for nitrogen removal and treatment of digester
reject water in wastewater using bioagumenation
Abstract
An efficient system and process for removing nitrogen from
wastewater while enriching seed sludge in the mainstream treatment
process. Bioaugmentation of seed autotrophic organisms facilitate
the nitrification reactions by enhancing the rates of reaction
advantageously within a smaller volume or within a shorter
activated sludge solids retention time. Likewise, bioaugmentation
of seed denitrification organisms will also enhance rate of
reaction within a smaller volume or shorter activated sludge solids
retention time. Separate treatment of high ammonia digester reject
water is an efficient method to treat nitrogen in recycle streams
as well as to enrich the seed nitrifying and denitrifying
cultures.
Inventors: |
Bailey; Walter F. JR.;
(Washington, DC) ; Murthy; Sudhir N.; (Washington,
DC) ; Benson; Leonard; (Washington, DC) ;
Constantine; Timothy; (Whitby, CA) ; Daigger; Glen
T.; (Parker, CO) ; Sadick; Thomas E.; (Newport
News, VA) ; Katehis; Dimitrios; (Chalfont,
PA) |
Correspondence
Address: |
DICKSTEIN SHAPIRO LLP
1825 EYE STREET NW
Washington
DC
20006-5403
US
|
Family ID: |
38002676 |
Appl. No.: |
11/826131 |
Filed: |
July 12, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11585796 |
Oct 25, 2006 |
|
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11826131 |
Jul 12, 2007 |
|
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60730035 |
Oct 26, 2005 |
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Current U.S.
Class: |
210/195.3 |
Current CPC
Class: |
C02F 3/121 20130101;
Y02W 10/15 20150501; C02F 3/302 20130101; C02F 3/301 20130101; Y02W
10/10 20150501 |
Class at
Publication: |
210/195.3 |
International
Class: |
C02F 3/12 20060101
C02F003/12 |
Claims
1-16. (canceled)
17. A system for the treatment of wastewater comprising: a
mainstream reactor receiving wastewater as influent and outputting
an effluent; and a seed production reactor for receiving and
performing bioaugmentation on the mainstream reactor effluent,
wherein the seed production reactor outputs bioaugmentation seed
sludge, at least a portion of which is returned to the mainstream
reactor.
18. The system of claim 17, wherein the solids retention time for
carbonaceous substrate removal in the mainstream reactor is within
the range of about 1 to about 3 days.
19. The system of claim 17, wherein the solids retention time for
the seed production reactor is within the range of about 7 to about
20 days.
20. A system for the treatment of wastewater comprising: a
mainstream reactor for receiving wastewater as influent and for
producing mainstream reactor effluent; a seed production reactor
for receiving and treating the mainstream reactor effluent and for
producing a quantity of seed sludge; and a sidestream
bioaugmentation enrichment reactor (SBER) for receiving and
treating the quantity of seed sludge and for producing
bioaugmentation sludge, at least a portion of which is returned to
the mainstream reactor.
21. The system of claim 20, wherein the SBER also receives digester
reject water as influent.
22. The system of claim 20, wherein the mainstream reactor sends at
least a portion of its effluent to the SBER for treatment to
enhance the formation of nitrite in the SBER and in the mainstream
reactor.
23. The system of claim 20, wherein the SBER sends at least a
portion of the bioaugmentation sludge to the seed production
reactor.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority to U.S. Provisional
Patent Application Ser. No. 60/730,035, filed on Oct. 26, 2005, the
disclosure of which is incorporated by reference in its
entirety.
FIELD OF THE INVENTION
[0002] The present invention relates generally to wastewater
treatment and in particular to the treatment of digest reject
water.
BACKGROUND OF THE INVENTION
[0003] With reference to FIG. 1, a block diagram of a conventional
wastewater treatment process is shown. The treatment includes
influent wastewater 111 being settled in a primary settling basin
110. Settled sludge 115 (i.e., primary sludge) is sent to an
anaerobic sludge digester 140, while the settled wastewater 112 is
sent for secondary treatment. This secondary treatment may include
biological aeration in aeration tanks 120 and a final settling
process in a final settling basin 130. A portion of the sludge 114
from the final settling basin 130 is returned to the secondary
treatment in order to maintain biological compounds in the
influent. Effluent water stream 118 that meets water quality
standards is output from the final settling basin 130. The
remainder of the waste activated sludge 113 from the final settling
basin 130 is sent to the anaerobic sludge digester 140. After the
anaerobic sludge digestion process, the removed water 116 is mixed
with the incoming influent wastewater 111 and the stabilized solids
(biosolids) 117 are now safe for application as fertilizers, for
example.
[0004] One problem that plagues conventional wastewater treatment
plants is nitrogen removal to meet effluent discharge water quality
standards. There are various sources of nitrogen in municipal
wastewater, including human feces, industrial wastes, and other
garbage. Typically, nitrogen removal at wastewater treatment plants
is achieved by a series of nitrification and denitrification steps.
Specifically, nitrifying bacteria convert ammonia to nitrite and
subsequently to nitrate, followed by denitrification of nitrite or
nitrate to nitrogen gas. The general chemical equations for these
processes are: ##STR1##
[0005] The capability to remove nitrogen is constrained by the rate
limiting aerobic nitrification reactions to convert ammonia to
nitrite and/or nitrate by slow growing autotrophic organisms. The
cumulative volume requirements for nitrogen removal depends on the
completion of these reactions. Accordingly, there is a need and
desire for a more efficient nitrogen removal process by encouraging
the nitrification/denitrification processes in the mainstream
reactor.
BRIEF SUMMARY OF THE INVENTION
[0006] The present invention, as illustrated in the various
exemplary embodiments, includes an efficient process for removing
nitrogen from wastewater while enriching seed sludge in the
mainstream treatment process. Bioaugmentation of seed autotrophic
organisms will facilitate the nitrification reactions by enhancing
the rates of reaction within a smaller volume or within a shorter
activated sludge solids retention time ("SRT"). Likewise,
bioaugmentation of seed denitrification organisms will also enhance
the rate of reaction within a smaller volume or shorter activated
sludge solids retention time. Additionally, separate treatment of
high ammonia digester reject water is an efficient method to treat
nitrogen in recycle streams as well as to enrich the seed
nitrifying and denitrifying cultures.
[0007] In accordance with one exemplary aspect of the invention,
direct mainstream bioaugmentation of sludge is performed and at
least a part of the treated seed sludge is returned to a part of
the mainstream reactor.
[0008] In accordance with a second exemplary aspect of the
invention, sidestream bioaugmentation is performed in a seed
production reactor, and at least a part of the bioaugmentation
sludge is returned to a mainstream reactor. In accordance with a
third exemplary aspect of the invention, at least a part of the
bioaugmentation sludge is returned to a mainstream reactor and a
remaining portion of the bioaugmentation sludge is returned to the
seed production reactor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The foregoing and other aspects of the invention will be
better understood from the following detailed description of the
invention, which is provided in connection with the accompanying
drawings, in which:
[0010] FIG. 1 is a block diagram of a conventional wastewater
treatment process;
[0011] FIG. 2 is a block diagram of a portion of a wastewater
treatment process in accordance with a first exemplary embodiment
of the invention;
[0012] FIG. 3 is a block diagram of a portion of a wastewater
treatment process in accordance with a second exemplary embodiment
of the invention; and
[0013] FIG. 4 is a block diagram of a portion of a wastewater
treatment process in accordance with a third exemplary embodiment
of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0014] In the following detailed description, reference is made to
the accompanying drawings, which form a part hereof and show by way
of illustration specific embodiments in which the invention may be
practiced. These embodiments are described in sufficient detail to
enable those skilled in the art to practice the invention, and it
is to be understood that other embodiments may be utilized, and
that changes may be made without departing from the spirit and
scope of the present invention. The progression of processing steps
described is exemplary of embodiments of the invention; however,
the sequence of steps is not limited to that set forth herein and
may be changed as is known in the art, with the exception of steps
necessarily occurring in a certain order.
[0015] In accordance with the invention, and as described in more
detail below with respect to FIGS. 2-4, exemplary wastewater
treatment systems include a mainstream and a seed production
reactor. It should be understood that with each exemplary system,
other wastewater treatment processes (not shown) may be used in
conjunction with the described processes. These other processes in
no way affect the scope of the present invention.
[0016] In accordance with the invention, seed sludge is generated
in a seed production reactor. The seed production reactor is a
nitrification and denitrification process that receives a low
strength ammonia wastewater that is first nitrified and
subsequently denitrified using an external carbon substrate such as
methanol, ethanol, acetic acid, sugar, glycol or glycerol. These
denitrifying carbon substrates will produce specialized organisms
for denitrification. The influent to the seed production reactor
consists of mainly ammonia and very little carbonaceous substrate.
Autotrophic conditions are promoted, allowing organisms to use
ammonia as an energy source and convert it to nitrate, thus
producing an enriched population of autotrophic (nitrifying) seed
organisms. Subsequently, anoxic conditions are promoted for
denitrification using external carbon, thus producing an enriched
population of denitrifying seed organisms. The effluent is then
sent to a settling basin.
[0017] Portions of a first exemplary waste water treatment system
200 are shown in FIG. 2. It should be understood that the
wastewater flow 212 entering the system 200 may be similar to the
flow 112 described above with reference to effluent from a primary
clarifier (settling basin 110) in FIG. 1. In accordance with this
first exemplary bioaugmentation process, a steady state quantity of
the autotrophic seed sludge 220 is recovered and sent to the
mainstream high rate bioaugmentation reactor, or mainstream reactor
201, where nitrification is promoted. The control of ammonia flow
in the effluent of the mainstream flow 215 to the seed production
reactor 202 for seed generation and maintenance of steady state
seed quantity is important for process stability. This control is
achieved by varying the mainstream flow 215 or volume subject to
seed nitrification. The steady state quantity of seed is achieved
by sending the seed to only part of the mainstream bioaugmentation
process (between 30-60% flow or process volume), in a manner to
encourage sufficient but not excessive nitrification in the
mainstream process. Sufficient ammonia is allowed to flow into the
seed production reactor 202 for seed regeneration and steady state
maintenance.
[0018] The mainstream bioaugmentation 201 and seed 202 reactors are
operated at normal seasonal water temperatures (10.degree. C. to
27.degree. C.) and pH (6.5-7.5). The mainstream reactor 201 is
operated aggressively at a low SRT of 0.5-3 days for carbonaceous
substrate removal with seed enhanced nitrification and simultaneous
or staged step-feed denitrification/nitrification. The seed
production reactor 202 is operated in the SRT range of 7-20 days;
with an optimum range of 10-15 days.
[0019] As shown in FIG. 2, return activated sludge 208, 209 of each
of the mainstream 201 and the seed 202 reactors, respectively, may
be used as a recycle stream 208, 209 to further enhance biological
reactions in these reactors 201, 202. In addition, the waste sludge
217 can be further treated using lime stabilization, anaerobic
digestion, or other known sludge treatment techniques. The treated
waste sludge 217 may then be sent for final disposal and/or
management. Effluent water 225 from the seed production reactor 202
may be further processed, as desired. Other processes for treating
the seed production reactor effluent water 225, such as tertiary
treatments, are beyond the scope of the present invention.
[0020] Thus, unlike conventional seed treatment processes, the
first exemplary system 200 provides for the seeding of a mainstream
reactor process. This advantageously helps to: (1) maintain the
steady state seed mass, (2) control addition of seed to a partial
flow/volume in the mainstream process, and (3) and provide for
denitrification of seed derived nitrate simultaneously or
sequentially within the mainstream process using a step-feed
process.
[0021] The advantages of this first exemplary system 200 include:
lower methanol requirements of between 25-50% for denitrification
through reductions in overall ammonia and subsequent nitrate loads
in the seed production reactor, lower denitrification volume
requirements of between 25-50% through reductions in nitrate loads,
and lower nitrification volume requirements of between 25-50%
through reductions in ammonia loads.
[0022] Turning to FIG. 3, a second exemplary wastewater treatment
system 300 is shown. The second system 300 includes a mainstream
reactor 301 having a wastewater influent 312 and a mainstream
effluent 315 that is sent to a seed production reactor 302. In
accordance with the second exemplary embodiment of the invention, a
steady state quantity of seed organism 307 generated by the seed
production reactor 302 is sent to a sidestream process, the
Sidestream Bioaugmentation and Enrichment Reactor ("SBER") 310. The
SBER is also fed a high strength anaerobic digester reject water
recycle 316, and may receive additional inputs of carbon sources
for denitrification and alkalinity, as necessary to maintain the
desired pH levels. Accordingly, the sludge stabilization technique
for a system in accordance with this embodiment is likely anaerobic
digestion in order to produce the high strength reject water 316.
Return activate sludge 308, 309 is used as a recycle stream in
mainstream and seed production reactors, 301, 302.
[0023] The SBER 310 is operated at a temperature somewhat higher
than the mainstream process 301. The temperature of the SBER 310 is
approximately between 2 and 20 degrees Celsius higher than the
mainstream reactor 301 and represents a volume-averaged temperature
of the higher temperature incoming reject water 316 recycle and the
seed sludge 307. This temperature is high enough to improve rates
of nitrification and denitrification in the SBER 310, but low
enough to allow the seed population to grow in both the SBER 310
and mainstream reactor 301. The solids retention time (SRT) of the
SBER 310 is maintained between 1 and 5 days aerobic SRT and between
1 and 5 days anoxic SRT. The pH in the SBER 310 is maintained
between 6.0-8.5 with an optimum range of 6.5-7.5. The dissolved
oxygen concentration can be maintained as high as 5 mg/L and as low
as 0.2 mg/L, during aerobic operations. The optimum dissolved
oxygen concentration will depend on the final reactions desired in
the SBER If the reactions need to stop at nitrite, the optimum
dissolved oxygen is lower. If the reaction proceeds to produce
nitrate, the optimum dissolved oxygen concentration is higher. In
accordance with an embodiment, the optimum dissolved oxygen
concentration is 2 mg/L.
[0024] The reject water 316 is treated; nitrified and then
denitrified (using the same external carbon source as the seed
production reactor) in this initial bioaugmentation step. This step
also serves as a seed enrichment step, to increase the yield of
seed nitrifying and denitrifying sludge. The enriched seed 320 is
then sent to the mainstream reactor 301 to perform bioaugmentation.
The enriched seed 320 has a high capability to perform
nitrification in the mainstream reactor 301. The mainstream 301 and
seed production reactors 302 are operated at normal seasonal water
temperatures (10.degree. C. to 27.degree. C.) and pH (6.5-7.5). The
mainstream reactor 301 is operated aggressively at a low SRT of
within the range of about 0.5-3 days for carbonaceous substrate
removal with seed enhanced nitrification and simultaneous or staged
step-feed denitrification/nitrification. The seed production
reactor 302 is operated in the SRT range of 7-20 days, with an
optimum range of 10-15 days. For maintenance of steady-state seed
sludge, the same description in the first exemplary system 200,
applies.
[0025] As discussed above with reference to FIG. 2, a part of the
effluent of each of the mainstream 301 and the seed 302 reactors
may be used as recycle streams 308, 309, respectively, to further
enhance biological reactions in these reactors 301, 302. In
addition, part of the effluent 319 from the mainstream reactor 301
may be sent to the SBER 310 for bioaugmentation processing directly
and if necessary to control the formation of nitrate. It may be
desirable to stop the nitrification reaction at nitrite by reducing
the dissolved oxygen concentration, ammonia or nitrite inhibition,
or by the addition of effluent 319. These operations will result in
the wash out of organisms responsible for promoting the second step
of nitrification reaction. This partial nitrification process can
limit the amount of air and external carbon necessary. Waste sludge
317 can be further stabilized and treated using known sludge
treatment techniques. Effluent water 325 from the seed production
reactor may be further processed, using known tertiary or other
treatments, as desired.
[0026] Thus, unlike conventional processes, the second exemplary
system 300 also provides for the seeding of a mainstream reactor
process. Thus, the second exemplary system 300 appreciates the same
advantages from seeding the mainstream process as discussed
above.
[0027] Other advantages realized by this option include lower
methanol requirements of 25-50% for denitrification through
reductions in overall ammonia and subsequent nitrate loads in the
seed production reactor, lower denitrification volume requirements
of 25-50% through reductions in nitrate loads, lower nitrification
volume requirements of 25-50% through reductions in ammonia loads,
and the capability to treat high-strength reject water 316.
[0028] A third exemplary system 400 in accordance with the
invention is shown in FIG. 4. The third system 400 includes a
mainstream reactor 401 having a wastewater influent 412 and a
mainstream reactor effluent 415 that is sent to a seed production
reactor 402. Return activated sludge 408, 409 are used as recycle
streams for each both reactors, 401, 402, respectively. In
accordance with the invention, a steady state quantity of seed
organism 407 is sent to a sidestream process, SBER 410 in the third
exemplary system 400. The SBER 410 is also fed a high strength
anaerobic digester reject water recycle 416, and other inputs may
include carbonaceous substances and alkalinity. The sludge
stabilization technique for a system in accordance with this
exemplary embodiment is likely anaerobic digestion in order to
produce the high strength reject water 416.
[0029] The SBER 410 is operated at a temperature somewhat higher
than the mainstream process 401. The temperature of the SBER 410 is
approximately between 2 and 20 degrees Celsius higher than the
mainstream reactor 401 and represents a volume-averaged temperature
of the higher temperature incoming reject water 416 recycle and the
seed sludge 407. This temperature is high enough to improve rates
of nitrification and denitrification in the SBER 410, but low
enough to allow the seed population to grow in both the SBER 410
and mainstream reactor 401.
[0030] The solids retention time (SRT) of the SBER 410 is
preferably maintained between about 1 and 5 days aerobic SRT and
between 1 and 5 days anoxic SRT. The pH in the SBER 410 is
maintained between 6.0 and 8.5 with an optimum range of 6.5 to 7.5.
The dissolved oxygen concentration can be maintained as high as 5
mg/L and as low as 0.2 mg/L during aerobic operations. The optimum
dissolved oxygen concentration will depend on the final reactions
desired in the SBER. If the reactions need to stop at nitrite, the
optimum dissolved oxygen is lower at approximately 0.5 mg/L. If the
reaction needs to proceed to nitrate, the optimum dissolved oxygen
concentration is higher, at approximately 2 mg/L.
[0031] The reject water 416 is treated; nitrified and then
denitrified (using the same external carbon source as the seed
production reactor) in this initial bioaugmentation step. This step
also serves as a seed enrichment step, to increase the yield of
seed nitrifying and denitrifying sludge. The enriched seed sludge
420 from the SBER 410 can be sent in part or in entirety to the
mainstream reactor 401 and the remaining portion of the enriched
seed is sent to the seed production reactor to maintain process
stability in case of inhibition and process upsets and to perform
additional bioaugmentation, if desired. Thus, a smaller stream 420
is sent to the mainstream reactor 401 to perform mainstream
bioaugmentation.
[0032] The mainstream 401 and seed production reactors 402 are
operated at normal seasonal water temperatures (10.degree. C. to
27.degree. C.) and pH (6.5-7.5). The mainstream reactor 401 is
operated aggressively at a low SRT with the range of about 0.5-3
days for carbonaceous substrate removal with seed enhanced
nitrification and simultaneous or staged step-feed
denitrification/nitrification. The seed production reactor 402 is
preferably operated in the SRT range of about 7-20 days, with an
optimum range of 10-15 days. For maintenance of steady-state seed
sludge, the same description described above with reference to FIG.
2 applies.
[0033] As discussed above with reference to FIG. 2, a part of the
effluent of each of the mainstream 401 and the seed 402 reactors
may be used as recycle streams 408, 409, respectively, to further
enhance biological reactions in these reactors 401, 402. In
addition, the waste sludge 417 can be further treated using known
sludge stabilization and treatment techniques. Effluent water 425
from the seed production reactor may be further processed, using
tertiary or other known processing techniques, as desired. Another
optional location for waste sludge is shown as effluent 422 from
the SBER 410.
[0034] Like the first two exemplary embodiments, a steady-state
seed sludge 420 is sent to the mainstream process 401 to perform
nitrification and denitrification, but sufficient ammonia 421 is
allowed to flow to the seed production reactor 402 for seed
regeneration.
[0035] The third exemplary system 400 may be easier to control than
the second exemplary system 300, since there is flexibility to send
seed sludge 420, 421 to either process (mainstream reactor 401 or
seed production reactor 402), thus the seed production reactor 402
can be sustained through the seed recycle 409, and does not need to
completely depend on ammonia from mainstream reactor 401 for
regeneration. It should be noted that waste sludge 422 may also be
produced in this SBER 410 for external treatment, such as sludge
stabilization prior to land disposal.
[0036] Another advantage of system 400 is the seeding of
denitrifiers to the seed production reactor 402. Since the same
external carbon source is used in both the seed production reactor
402 and SBER 410, the denitrifying populations are also enriched in
the SBER 410 and available for bioaugmentation in the seed
production reactor 402. Thus the denitrification volume
requirements are reduced even more than in the first two exemplary
systems 200, 300. In system 400, the high strength load from the
digester reject water recycle 416 is treated (nitrified and
denitrified) simultaneously as the seed sludge 407 is enriched.
[0037] Thus, unlike conventional processes, the third exemplary
system 400 also provides for the seeding of a mainstream reactor
process. Thus, the third exemplary system 400 appreciates the same
advantageous from seeding the mainstream process as discussed above
with reference to exemplary systems 200, 300.
[0038] Other advantages realized by system 400 include: lower
methanol requirements of 25-50% for denitrification through
reductions in overall ammonia and subsequent nitrate loads in the
seed production reactor, lower denitrification volume requirements
of 25-50% through reductions in nitrate loads and through seeding f
denitrifiers, lower nitrification volume requirements of 25-50%
through reductions in ammonia loads, and capability to treat
high-strength reject water.
[0039] The processes and devices described above illustrate
preferred methods and typical devices of many that could be used
and produced. The above description and drawings illustrate
embodiments, which achieve the objects, features, and advantages of
the present invention. However, it is not intended that the present
invention be strictly limited to the above-described and
illustrated embodiments. For example, the mainstream reactor may
consist of several tanks in parallel, some of which may undergo
bioaugmentation while others remain unbioaugmented. Additionally,
any modifications, though presently unforeseeable, of the present
invention that come within the spirit and scope of the following
claims should be considered part of the present invention.
* * * * *