U.S. patent application number 14/995941 was filed with the patent office on 2016-07-21 for wastewater treatment system.
The applicant listed for this patent is LEADERMAN & ASSOCIATES CO., LTD., NATIONAL CHIAO TUNG UNIVERSITY. Invention is credited to Chin-Te Chen, Ming-Kuei Chiang, Yi-An Chiang, Chien-Ju Lan, Der-Ming Lee, Jih-Gaw Lin, Keng-Chuan Sung, Cheng-Yu Tsai.
Application Number | 20160207807 14/995941 |
Document ID | / |
Family ID | 56407300 |
Filed Date | 2016-07-21 |
United States Patent
Application |
20160207807 |
Kind Code |
A1 |
Lee; Der-Ming ; et
al. |
July 21, 2016 |
WASTEWATER TREATMENT SYSTEM
Abstract
The wastewater treatment system of the present invention is
adapted to remove COD and nitrogenous compounds from wastewater.
The system includes a carbon-removing anaerobic fluidized bed
reactor and a nitrogen-removing fluidized bed reactor. The
carbon-removing anaerobic fluidized bed reactor is mainly adapted
to transfer most of the COD in the wastewater into methane through
hydrolysis, acedogenesis and methanogenosis reactions. The
nitrogen-removing fluidized bed reactor is adapted to transfer
ammonium nitrogen and residual COD in the wastewater into nitrogen
gas through partial nitrification, anammox and denitrification
reactions.
Inventors: |
Lee; Der-Ming; (Taipei City,
TW) ; Chiang; Ming-Kuei; (Taipei City, TW) ;
Chen; Chin-Te; (Taipei City, TW) ; Sung;
Keng-Chuan; (Taipei City, TW) ; Lan; Chien-Ju;
(Taipei City, TW) ; Lin; Jih-Gaw; (Hsinchu City,
TW) ; Chiang; Yi-An; (Taipei City, TW) ; Tsai;
Cheng-Yu; (Kaohsiung City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LEADERMAN & ASSOCIATES CO., LTD.
NATIONAL CHIAO TUNG UNIVERSITY |
TAIPEI CITY
HSINCHU CITY |
|
TW
TW |
|
|
Family ID: |
56407300 |
Appl. No.: |
14/995941 |
Filed: |
January 14, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C02F 3/305 20130101;
C02F 2003/001 20130101; C02F 3/301 20130101; Y02E 50/343 20130101;
C02F 9/00 20130101; C02F 3/2833 20130101; Y02E 50/30 20130101; Y02W
10/37 20150501; C02F 3/2853 20130101; C02F 3/307 20130101; C02F
3/286 20130101; C02F 3/2806 20130101 |
International
Class: |
C02F 3/28 20060101
C02F003/28 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 15, 2015 |
TW |
104101327 |
Claims
1. A wastewater treatment system, for at least partially removing
COD and nitrogenous compounds from wastewater, the nitrogenous
compounds including ammonium nitrogen, the wastewater treatment
system comprising: a carbon-removing anaerobic fluidized bed
reactor, including a first cylinder, a plurality of first granular
carriers, a first sedimentation tank, a first fluidized means,
first microorganisms and extracellular enzymes; the first cylinder
defining therein a first fluidized chamber, the first cylinder
having a first upper opening and a first lower opening, the first
upper and lower openings both being communicated with the first
fluidized chamber; the first fluidized chamber being locally filled
by the first granular carriers; the first sedimentation tank having
a first bottom opening and a first outfall locationally higher than
the first bottom opening, the first bottom opening being
communicated with the first upper opening; the first fluidized
means being for guiding the wastewater into the first fluidized
chamber through the first lower opening and for suspending the
first granular carriers in first fluidized chamber; a part of the
COD performing hydrolysis reaction with said extracellular enzymes
to decompose organic compounds of the COD into at least one of
amino acids, carbohydrates and fatty acids, at least one part of
said first microorganisms being attached to the first granular
carriers, said first microorganisms including acidogenic bacteria
and methanogens, wherein the acidogenic bacteria perform
acedogenesis reaction to transfer said at least one of amino acids,
carbohydrates and fatty acids into fatty acids having 4 or fewer
carbons on their backbone chains, hydrogen gas and carbon dioxide,
and the methanogens perform methanogenesis reaction to transfer the
fatty acids having 4 or fewer carbons on their backbone chains,
hydrogen gas and carbon dioxide into methane and carbon dioxide,
said first fluidized chamber having an oxidation-reduction
potential therein smaller than -400 mv; the first outfall allowing
the wastewater to be drained from the carbon-removing anaerobic
fluidized bed reactor; and a nitrogen-removing fluidized bed
reactor, including a second cylinder, a plurality of second
granular carriers, a second sedimentation tank, a second fluidized
means and second microorganisms; the second cylinder defining
therein a second fluidized chamber, the second cylinder having a
second upper opening and a second lower opening, the second upper
and lower openings both being communicated with the second
fluidized chamber, the second lower opening serving to introduce
the wastewater that has been processed in the carbon-removing
anaerobic fluidized bed reactor; the second fluidized chamber being
locally filled by the second granular carriers; the second
sedimentation tank having a second bottom opening and a second
outfall locationally higher than the second bottom opening, the
second bottom opening being communicated with the second upper
opening; the second fluidized means being for guiding the
wastewater into the second fluidized chamber through the second
lower opening, and for suspending the second granular carriers in
the second fluidized chamber; at least one part of said second
microorganisms being attached to the second granular carriers, said
second microorganisms including nitrifying bacteria, anammox
bacteria and heterotrophic denitrifying bacteria, the nitrifying
bacteria performing partial nitrification reaction to oxidize
ammonium nitrogen into nitrite nitrogen, the anammox bacteria
performing anammox reaction to transfer ammonium nitrogen and
nitrite nitrogen into nitrogen gas and nitrate nitrogen, the
heterotrophic denitrifying bacteria performing denitrification
reaction to transfer nitrate nitrogen and at least a part of the
residual COD into nitrogen gas.
2. A wastewater treatment system, for at least partially removing
COD and nitrogenous compounds from wastewater, nitrogenous
compounds includes ammonium nitrogen, the wastewater treatment
system comprising: a carbon-removing anaerobic fluidized bed
reactor, including a first cylinder, a plurality of first granular
carriers, a first sedimentation tank, a first fluidized means,
first microorganisms and extracellular enzymes; the first cylinder
defining therein a first fluidized chamber, the first cylinder
having a first upper opening and a first lower opening, the first
upper and lower openings both being communicated with the first
fluidized chamber; the first fluidized chamber being locally filled
by the first granular carriers; the first sedimentation tank having
a first bottom opening and a first outfall locationally higher than
the first bottom opening, the first bottom opening being
communicated with the first upper opening; the first fluidized
means being for guiding the wastewater into the first fluidized
chamber through the first lower opening and for suspending the
first granular carriers in first fluidized chamber; a part of the
COD performing hydrolysis reaction with said extracellular enzymes
to decompose organic compounds forming the COD into at least one of
amino acids, carbohydrates and fatty acids, at least one part of
said first microorganisms being attached to the first granular
carriers, said first microorganisms including acidogenic bacteria
and methanogens, wherein the acidogenic bacteria perform
acedogenesis reaction to transfer said at least one of amino acids,
carbohydrates and fatty acids into fatty acids having 4 or fewer
carbons on their backbone chains, hydrogen gas and carbon dioxide,
and the methanogens perform methanogenesis reaction to transfer the
fatty acids having 4 or fewer carbons on their backbone chains,
hydrogen gas and carbon dioxide into methane and carbon dioxide,
said first fluidized chamber having an oxidation-reduction
potential therein smaller than -400 mv; the first outfall serving
to drain the wastewater that has been processed through hydrolysis
reaction, acedogenesis reaction and methanogenesis reaction; an
anaerobic fluidized membrane reactor, including a third cylinder, a
plurality of third granular carriers, a third sedimentation tank, a
third fluidized means and at least one tubular membrane, the third
cylinder defining therein a third fluidized chamber, the third
cylinder having a third upper opening and a third lower opening,
the third upper and lower openings both being communicated with the
third fluidized chamber, the third lower opening serving to
introduce the wastewater that has been processed in the
carbon-removing anaerobic fluidized bed reactor; the third
fluidized chamber being locally filled by the third granular
carriers; the third sedimentation tank having a third outfall, the
third sedimentation tank is provided atop the third cylinder, the
third sedimentation tank being communicated with the third
fluidized chamber through the tubular membrane, the tubular
membrane extending form the third sedimentation tank into the third
fluidized chamber, the tubular membrane being defined by a porous
wall, the third fluidized means being for guiding the wastewater
into the third fluidized chamber through the third lower opening
and for suspending the third granular carriers in the third
fluidized chamber; the third outfall serving to drain the
wastewater from the anaerobic fluidized membrane reactor; and a
nitrogen-removing fluidized bed reactor, including a second
cylinder, a plurality of second granular carriers, a second
sedimentation tank, a second fluidized means and second
microorganisms; the second cylinder defining therein a second
fluidized chamber, the second cylinder having a second upper
opening and a second lower opening, the second upper and lower
openings both being communicated with the second fluidized chamber,
said second lower opening serving to introduce the wastewater that
has been processed in the anaerobic fluidized membrane reactor; the
second fluidized chamber being locally filled by the second
granular carriers; the second sedimentation tank having a second
bottom opening and a second outfall locationally higher than the
second bottom opening, the second bottom opening being communicated
with the second upper opening; the second fluidized means being for
guiding the wastewater into the second fluidized chamber through
the second lower opening, and for suspending the second granular
carriers in the second fluidized chamber; at least one part of said
second microorganisms being attached to the second granular
carriers, said second microorganisms including nitrifying bacteria,
anammox bacteria and heterotrophic denitrifying bacteria, the
nitrifying bacteria performing partial nitrification reaction to
oxidize ammonium nitrogen into nitrite nitrogen, the anammox
bacteria performing anammox reaction to transfer ammonium nitrogen
and nitrite nitrogen into nitrogen gas and nitrate nitrogen, the
heterotrophic denitrifying bacteria performing denitrification
reaction to transfer nitrate nitrogen and at least a part of the
residual COD into nitrogen gas.
3. The wastewater treatment system of claim 1, wherein a dissolved
oxygen concentration in the second fluidized chamber is 0.1-0.5
mg/L.
4. The wastewater treatment system of claim 2, wherein a dissolved
oxygen concentration in the second fluidized chamber is 0.1-0.5
mg/L.
5. The wastewater treatment system of claim 1, wherein the first
sedimentation tank is atop provided with a methane vent.
6. The wastewater treatment system of claim 2, wherein the first
sedimentation tank is atop provided with a methane vent.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field
[0002] The present invention relates to wastewater treatment, and
more particularly to a wastewater treatment system that uses
microorganisms to treat COD and ammonium nitrogen in water.
[0003] 2. Description of Related Art
[0004] In the field of biological wastewater treatment, the
traditional nitrification-denitrification method was once
predominant until a recently introduced technology based on anammox
bacteria have been regarded better in terms of energy efficiency
and increasingly adopted. During anaerobic ammonium oxidation,
ammonium nitrogen and nitrite nitrogen act as an electron donor and
an electron acceptor, respectively, and are then transferred into
nitrogen gas and nitrate nitrogen.
[0005] It is reported that anammox bacteria is more suitable for
wastewater having high ammonium nitrogen concentration (with
ammonium nitrogen concentration greater than 500 mg N/L). One
reason for this is that since anammox bacteria grow slowly, if the
supply of ammonium nitrogen is not abundant, the startup time of
the relevant biological reactor may be significantly increased and,
in worse cases, the establishment of a reaction system based on
anammox bacteria may totally fail. It is known that municipal
wastewater has relatively low ammonium nitrogen concentration,
which is typically 20-85 mg N/L, and for this reason anammox
bacteria are considered ineffective in treating municipal
wastewater. Besides, domestic wastewater usually has its COD higher
than ammonium nitrogen concentration. When COD is extremely high, a
reactor based on anammox bacteria may fail to remove COD
effectively.
SUMMARY OF THE INVENTION
[0006] In view of this, the primary objective of the present
invention is to provide a wastewater treatment system effective in
removing at least some COD and nitrogenous compounds from
wastewater.
[0007] For achieving the foregoing and other objectives, the
disclosed wastewater treatment system for at least partially
removing COD, ammonium nitrogen and other nitrogenous compounds
from wastewater comprises a carbon-removing anaerobic fluidized bed
reactor and a nitrogen-removing fluidized bed reactor. The
carbon-removing anaerobic fluidized bed reactor includes a first
cylinder, a plurality of first granular carriers, a first
sedimentation tank, a first fluidized means, first microorganisms
and extracellular enzymes. The first cylinder defines therein a
first fluidized chamber. The first cylinder has a first upper
opening and a first lower opening. The first upper and lower
openings are both communicated with the first fluidized chamber.
The first fluidized chamber is locally filled by the first granular
carriers. The first sedimentation tank has a first bottom opening
and a first outfall locatioanlly higher than the first bottom
opening. The first bottom opening is communicated with the first
upper opening. The first fluidized means serves to guide wastewater
into the first fluidized chamber from the first lower opening and
serves to suspend the first granular carriers in first fluidized
chamber. A part of the COD performs hydrolysis reaction with said
extracellular enzymes to decompose organic compounds of the COD
into at least one of amino acids, carbohydrates and fatty acids. At
least one part of said first microorganisms is attached to the
first granular carriers. Said first microorganisms include
acidogenic bacteria and methanogens, wherein the acidogenic
bacteria perform acedogenesis reaction to transfer at least one of
said amino acids, carbohydrates and fatty acids into fatty acids
having 4 or fewer carbons on their backbone chains, hydrogen gas
and carbon dioxide, and the methanogens perform methanogenesis
reaction to transfer the fatty acids having 4 or fewer carbons on
their backbone chains, hydrogen gas and carbon dioxide into methane
and carbon dioxide. Said first fluidized chamber has an
oxidation-reduction potential therein smaller than -400 mv. The
first outfall serves to drain the wastewater from the
carbon-removing anaerobic fluidized bed reactor. The
nitrogen-removing fluidized bed reactor includes a second cylinder,
a plurality of second granular carriers, a second sedimentation
tank, a second fluidized means and a second microorganism. The
second cylinder defines therein a second fluidized chamber. The
second cylinder has a second upper opening and a second lower
opening. The second upper and lower openings are both communicated
with the second fluidized chamber. The second lower opening serves
to introduce the wastewater drained from the first outfall. The
second fluidized chamber is locally filled by the second granular
carriers. The second sedimentation tank has a second bottom opening
and a second outfall locationally higher than the second bottom
opening. The second bottom opening is communicated with the second
upper opening. The second fluidized means serves to guide the
wastewater into the second fluidized chamber through the second
lower opening and serves to suspend the second granular carriers in
the second fluidized chamber. At least one part of said second
microorganisms is attached to the second granular carriers. Said
second microorganisms include nitrifying bacteria, anammox bacteria
and heterotrophic denitrifying bacteria. The nitrifying bacteria
perform partial nitrification reaction to oxidize ammonium nitrogen
into nitrite nitrogen. The anammox bacteria perform anammox
reaction to oxidize ammonium nitrogen and nitrite nitrogen into
nitrogen gas and nitrate nitrogen. The heterotrophic denitrifying
bacteria perform denitrification reaction to transfer nitrate
nitrogen and at least a part of the residual COD into nitrogen
gas.
[0008] For achieving the foregoing and other objectives, the
present invention further provides a wastewater treatment system
for at least partially removing COD and nitrogenous compounds that
include ammonium nitrogen from wastewater. The wastewater treatment
system includes a carbon-removing anaerobic fluidized bed reactor,
an anaerobic fluidized membrane reactor and a nitrogen-removing
fluidized bed reactor. The carbon-removing anaerobic fluidized bed
reactor includes a first cylinder, a plurality of first granular
carriers, a first sedimentation tank, a first fluidized means,
first microorganisms and extracellular enzymes. The first cylinder
defines therein a first fluidized chamber. The first cylinder has a
first upper opening and a first lower opening. The first upper and
lower openings are both communicated with the first fluidized
chamber. The first fluidized chamber is locally filled by the first
granular carriers. The first sedimentation tank has a first bottom
opening and a first outfall locationally higher than first bottom
opening. The first bottom opening is communicated with first upper
opening. The first fluidized means serves to guide the wastewater
from the first lower opening into the first fluidized chamber, and
serves to suspend the first granular carriers in the first
fluidized chamber. A part of the COD performs hydrolysis reaction
with said extracellular enzymes to decompose organic compounds of
the COD into at least one of amino acids, carbohydrates and fatty
acids. At least one part of said first microorganisms is attached
to the first granular carriers. Said first microorganisms include
acidogenic bacteria and methanogens, wherein the acidogenic
bacteria perform acedogenesis reaction to transfer at least one of
said amino acids, carbohydrates and fatty acids into fatty acids
having 4 or fewer carbons on their backbone chains, hydrogen gas
and carbon dioxide, and the methanogens perform methanogenesis
reaction to transfer the fatty acids having 4 or fewer carbons on
their backbone chains, hydrogen gas and carbon dioxide into methane
and carbon dioxide. Said first fluidized chamber has an
oxidation-reduction potential therein smaller than -400 mv. The
first outfall serves to drain the wastewater from the
carbon-removing anaerobic fluidized bed reactor. The anaerobic
fluidized membrane reactor includes a third cylinder, a plurality
of third granular carriers, a third sedimentation tank, a third
fluidized means and at least one tubular membrane. The third
cylinder defines therein a third fluidized chamber. The third
cylinder has a third upper opening and a third lower opening. The
third upper and lower openings are both communicated with the third
fluidized chamber. The third lower opening serves to introduce the
wastewater drained from the first outfall. The third fluidized
chamber is locally filled by the third granular carriers. The third
sedimentation tank has a third outfall. The third sedimentation
tank is located above the third cylinder and is communicated with
the third fluidized chamber through the tubular membrane. The
tubular membrane extends from the third sedimentation tank into the
third fluidized chamber and is defined by a porous wall. The third
fluidized means serves to guide the wastewater into the third
fluidized chamber through the third lower opening and serves to
suspend the third granular carriers in the third fluidized chamber.
The third outfall serves to drain the wastewater from the anaerobic
fluidized membrane reactor. The nitrogen-removing fluidized bed
reactor includes a second cylinder, a plurality of second granular
carriers, a second sedimentation tank, a second fluidized means and
second microorganisms. The second cylinder defines therein a second
fluidized chamber. The second cylinder has a second upper opening
and a second lower opening. The second upper and lower openings are
both communicated with the second fluidized chamber. The second
lower opening serves to introduce the wastewater drain from the
third outfall. The second fluidized chamber is locally filled by
the second granular carriers. The second sedimentation tank has a
second bottom opening and a second outfall locationally higher than
second bottom opening. The second bottom opening is communicated
with second upper opening. The second fluidized means serves to
guide the wastewater into the second fluidized chamber through the
second lower opening and serves to suspend the second granular
carriers in the second fluidized chamber. At least one part of said
second microorganisms is attached to the second granular carriers.
Said second microorganisms include nitrifying bacteria, anammox
bacteria and heterotrophic denitrifying bacteria. The nitrifying
bacteria perform partial nitrification reaction to oxidize ammonium
nitrogen into nitrite nitrogen. The anammox bacteria perform
anammox reaction to oxidize ammonium nitrogen and nitrite nitrogen
into nitrogen gas and nitrate nitrogen. The heterotrophic
denitrifying bacteria perform denitrification reaction to transfer
nitrate nitrogen and at least a part of the residual COD into
nitrogen gas.
[0009] The disclosed wastewater treatment system advantageously
requires significantly reduced startup time as compared to any
known wastewater treatment, and provides effective nitrogen removal
even for wastewater having low ammonium nitrogen concentration. The
disclosed wastewater treatment system is capable of transferring
most COD into methane.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic view of a wastewater treatment system
according to one embodiment of the present invention;
[0011] FIG. 2 according to one embodiment of the present invention
shows variations of ammonium nitrogen concentration and ammonium
nitrogen removal rate over time;
[0012] FIG. 3 according to one embodiment of the present invention
shows variations of total target nitrogen concentration and total
target nitrogen removal rate over time.
DETAILED DESCRIPTION OF THE INVENTION
[0013] Referring to FIG. 1, a wastewater treatment system according
to one embodiment of the present invention is configured to at
least partially remove COD and nitrogenous compounds including
ammonium nitrogen from wastewater. The wastewater treatment system
has a carbon-removing anaerobic fluidized bed reactor 10, an
anaerobic fluidized membrane reactor 20, and a nitrogen-removing
fluidized bed reactor 30. The disclosed wastewater treatment system
has its front half mainly serving to remove carbon-containing
compounds from water and has its rear half mainly serving to remove
nitrogenous compounds from water.
[0014] The carbon-removing anaerobic fluidized bed reactor 10
includes a first cylinder 11, a plurality of first granular
carriers 12, a first sedimentation tank 13, a first fluidized
means, first microorganisms and extracellular enzymes.
[0015] The first cylinder 11 defines therein a first fluidized
chamber 111. The first cylinder 11 has a first upper opening 112
and a first lower opening 113. The first upper and lower openings
112, 113 are both communicated with the first fluidized chamber
111. The first upper opening 112 is provided at the top of the
first cylinder 11. The first lower opening 113 is provided at the
bottom of the cylinder 11 for introducing wastewater.
[0016] The first fluidized chamber 111 is locally filled by the
first granular carriers 12. In the present embodiment, the first
granular carriers 12 are beads of natural zeolite but are not
limited thereto.
[0017] The first sedimentation tank 13 has a first bottom opening
131 and a first outfall 132 locationally higher than first bottom
opening 131. The first sedimentation tank 13 is provided at the top
of the first cylinder 11. The first bottom opening 131 is
communicated with first upper opening 112. The first sedimentation
tank 13 is atop provided with a methane vent 133.
[0018] The first fluidized means serves to guide the wastewater
into the first fluidized chamber 111 through the first lower
opening 113 and serves to suspend the first granular carriers 12 in
the first fluidized chamber 111. In one application, the first
granular carriers 12 do not enter the first sedimentation tank 13
because of the first fluidized means. The first fluidized means
includes any equipment that can generate upward flow in the first
fluidized chamber 111, such as water pumps like a magnetic pump 141
and/or a peristaltic pump 142. The water pumps may be used in any
number as long as the generated upward flow is speedy enough to
suspend the first granular carriers 12.
[0019] At least one part of the first microorganisms is attached to
the first granular carriers 12. Said first microorganisms include
acidogenic bacteria and methanogens, such as Methanosaeta spp. Said
extracellular enzymes refer to enzymes synthesized intracellularly
and then secreted outside to act extracellularly and these
extracellular enzymes are supportive to hydrolysis reaction. A part
of the COD in the wastewater perform hydrolysis reaction with the
extracellular enzymes, so that the organic compounds forming the
COD are decomposed into at least one of amino acids, carbohydrates
and fatty acids. The acidogenic bacteria perform acedogenesis
reaction to transfer at least one of said amino acids,
carbohydrates and fatty acids into fatty acids having 4 or fewer
carbons on their backbone chains (such as acetic acid, propanoic
acid, butyric acid), hydrogen gas and carbon dioxide. The
methanogens perform methanogenesis reaction to transfer the fatty
acids having 4 or fewer carbons on their backbone chains, hydrogen
gas and carbon dioxide into methane and carbon dioxide, also known
as biogas. The first fluidized chamber 111 maintains an anaerobic
environment therein without oxygen supply, and has its
oxidation-reduction potential smaller than -400 mv. The nitrogenous
compounds in the COD have been also transferred into ammonium
nitrogen in the precious process. The wastewater processed through
hydrolysis reaction, acedogenesis reaction and methanogenesis
reaction is then drained from the first outfall 132. At least one
part of the generated methane and carbon dioxide exhausts through
the methane vent 133 and is collected. The total reaction in the
first fluidized chamber 111 may be expressed by the following
reaction formula:
C a H b O c N d + ( 4 a - b - 2 c - 3 d 4 ) H 2 O .fwdarw. 4 a - b
- 2 c - 3 d 8 CH 4 + 4 a - b - 2 c - 3 d 8 CO 2 + d NH 3
##EQU00001##
[0020] For acclimating the first microorganisms in the first
fluidized chamber 111, activesludge carrying the first
microorganisms may be input into the first fluidized chamber 111.
At least one part of the first microorganisms is then attached to
the first granular carriers 12 and grows. In one example, the
activesludge input was acquired from the anaerobic digester in
Linkou Wastewater Treatment Plant (Taiwan) and the amount input was
500 ml. The mixed liquor suspended solid (MLSS) concentration was
22.5 g/L, and the mixed liquor volatile suspended solid (MLVSS)
concentration was 5.5 g/L.
[0021] The anaerobic fluidized membrane reactor 20 includes a third
cylinder 21, a plurality of third granular carriers 22, a third
sedimentation tank 23, a third fluidized means and one or more
tubular membranes 24.
[0022] The third cylinder 21 defines therein a third fluidized
chamber 211 and has a third upper opening 212 and a third lower
opening 213. The third upper and lower openings 212, 213 are both
communicated with the third fluidized chamber 211. The third upper
and lower openings 212, 213 are located at two ends of the third
cylinder 21, respectively. The third lower opening 213 serves to
introduce the wastewater drained from the first outfall 132. The
third fluidized chamber 211 also maintains therein an anaerobic
environment without particular aeration. In one possible
embodiment, the third fluidized chamber 211 also has its
oxidation-reduction potential smaller than -400 mv.
[0023] The third fluidized chamber 211 is locally filled by the
third granular carriers 22. In the present embodiment, the third
granular carriers 22 are beads of natural zeolite, but are not
limited thereto.
[0024] The third sedimentation tank 23 has a third outfall 231. The
third sedimentation tank 23 is provided at the top of the third
cylinder 21. The third sedimentation tank 23 is communicated with
the third fluidized chamber 211 through the tubular membrane 24.
The tubular membrane 24 extends from the lower part of the third
sedimentation tank 23 into the third fluidized chamber 211. The
tubular membrane 24 is defined by a porous wall. The third
sedimentation tank 23 and the third fluidized chamber 211 are not
communicated directly and there may be a partition arranged between
the third sedimentation tank 23 and the third fluidized chamber
211. In the present embodiment, the tubular membrane is a hollow
fiber film having an outer diameter of 1.2 mm, an inner pore size
smaller than 0.1 .mu.m and a total membrane surface area of 0.08
m.sup.2.
[0025] The third fluidized means serves to guide the wastewater
into the third fluidized chamber 211 through the third lower
opening 213 and serves to suspend the third granular carriers 22 in
the third fluidized chamber 211. In one application, the third
granular carriers 22 do not enter the third sedimentation tank 23
because of the third fluidized means. The third fluidized means
includes any equipment that can generate upward flow in the third
fluidized chamber 211, such as water pumps like a magnetic pump 251
and/or a peristaltic pump 252. The water pumps may be used in any
number as long as the generated upward flow is speedy enough to
suspend the third granular carriers 22. As the third granular
carriers 22 are lifted by the upward flow, they naturally scrub the
surface tubular membrane 24, thereby eliminating the need of
cleaning the tubular membrane with chemicals. The anaerobic
fluidized membrane reactor 20 maintains therein an anaerobic
environment without oxygen supply, and mainly serves to remove the
suspended solids form the wastewater. The processed wastewater is
then drained through the third outfall 231.
[0026] For verifying how effectively the carbon-removing anaerobic
fluidized bed reactor 10 and the anaerobic fluidized membrane
reactor 20 remove COD and suspended solids, some tests have been
conducted with the conditions described below. In one test,
domestic wastewater was continuously introduced into the
carbon-removing anaerobic fluidized bed reactor 10 through the
first lower opening 113. The domestic wastewater was obtained from
the wastewater treatment facility of National Chiao Tung
University, Taiwan. The organic loading rate (OLR) of the
carbon-removing anaerobic fluidized bed reactor 10 was controlled
at 1.75-4.7 Kg/m.sup.3/d. The hydraulic retention time (HRT) for
the carbon-removing anaerobic fluidized bed reactor 10 was 1 hour.
The membrane flux of the anaerobic fluidized membrane reactor 20
was controlled at 8.33-12.5 LMH. The hydraulic retention time for
the anaerobic fluidized membrane reactor 20 was 2-3 hours. The test
lasted for 111 days, and the results are listed in Table I below.
In Table I, AFBR represents the carbon-removing anaerobic fluidized
bed reactor; AFMBR represents the anaerobic fluidized membrane
reactor; TSS represents total suspended solids; VSS represents
volatile suspended solids and TKN represents total Kjeldahl
nitrogen. In the table, except for pH, all items for Influent and
Effluent are recoded in mg/L.
TABLE-US-00001 TABLE I Sample Effluent Removal Rate (%) Item No.
Influent AFBR AFMBR AFBR AFBR + AFMBR pH 30 7.15 .+-. 0.21 7.01
.+-. 0.08 7.19 .+-. 0.1 COD 26 130 .+-. 38 42 .+-. 11 20 .+-. 5 66
.+-. 12 84 .+-. 5 TSS 12 58 .+-. 31 12 .+-. 10 2 .+-. 3 74 .+-. 28
96 .+-. 7 VSS 12 44 .+-. 18 9 .+-. 8 1 .+-. 1 74 .+-. 5 97 .+-. 5
TKN 4 61 .+-. 22 48 .+-. 7 34 .+-. 7 Ammonium 11 42 .+-. 15 51 .+-.
15 47 .+-. 16 Nitrogen Nitrate 11 3 .+-. 4 2 .+-. 4 3 .+-. 4
Nitrogen Nitrite 11 0 0 0 Nitrogen
[0027] As demonstrated by the results, the carbon-removing
anaerobic fluidized bed reactor 10 and the anaerobic fluidized
membrane reactor 20 achieved a total COD removal rate of 70-90% and
a total suspended solid removal rate up to 96%. As the
carbon-removing anaerobic fluidized bed reactor 10 when solely used
provided desired removal, the anaerobic fluidized membrane reactor
20 may be omitted in some possible embodiments. During the process,
some microorganisms and extracellular enzymes in the
carbon-removing anaerobic fluidized bed reactor 10 might flow into
the anaerobic fluidized membrane reactor 20 with wastewater. Since
the anaerobic fluidized membrane reactor 20 also maintained therein
an anaerobic environment, some of the COD was transferred into
methane and carbon dioxide in the anaerobic fluidized membrane
reactor 20. The carbon-removing anaerobic fluidized bed reactor 10
and the anaerobic fluidized membrane reactor 20 achieved a specific
methane production of 0.13 L CH.sub.4/g COD.sub.removed, equal to
energy of 0.0024 kWh/m.sup.3.
[0028] On the other hand, the nitrogen-removing fluidized bed
reactor 30 includes a second cylinder 31, a plurality of second
granular carriers 32, a second sedimentation tank 33, an aerating
apparatus 34, a second fluidized means and second
microorganisms.
[0029] The second cylinder 31 defines therein a second fluidized
chamber 311. The second cylinder 31 has a second upper opening 312
and a second lower opening 313. The second upper and lower openings
312, 313 are both communicated with the second fluidized chamber
311. The second lower opening 313 serves to introduce the
wastewater drained by the third outfall 231.
[0030] The second fluidized chamber 311 is locally filled by the
second granular carriers 32. In the present embodiment, the second
granular carriers 32 are bioballs, which are plastic beads with
grooves on their surfaces (AQUARIUM CO., LTD, Taiwan), but are not
limited thereto.
[0031] The second sedimentation tank 33 has a second bottom opening
331 and a second outfall 332 locationally higher than the second
bottom opening 331. The second bottom opening 331 is communicated
with second upper opening 313. The second sedimentation tank 33 is
atop provided with a vent 333 for exhausting nitrogen gas generated
during the treatment.
[0032] The aerating apparatus 34 has an aerating end 341 that
extends from the second sedimentation tank 33 into the second
cylinder 31, for maintaining the dissolved oxygen concentration in
the second fluidized chamber 311 at 0.1-0.5 mg/L.
[0033] The second fluidized means serves to guide the wastewater
into the second fluidized chamber 311 through the second lower
opening 313 and serves to suspend the second granular carriers 32
in the second fluidized chamber 311. In one application, the second
granular carriers 32 do not enter the second sedimentation tank 33
because of the second fluidized means. The second fluidized means
includes any equipment that can generate upward flow in the second
fluidized chamber 311, such as water pumps like a magnetic pump 351
and/or a peristaltic pump 352. The water pumps may be used in any
number as long as the generated upward flow is speedy enough to
suspend the second granular carriers 32.
[0034] At least one part of the second microorganisms is attached
to the second granular carriers 32. The second microorganisms
include nitrifying bacteria, anammox bacteria and heterotrophic
denitrifying bacteria. The nitrifying bacteria perform partial
nitrification reaction to oxidize ammonium nitrogen in the
wastewater into nitrite nitrogen. The anammox bacteria perform
anammox reaction to transfer ammonium nitrogen and nitrite nitrogen
in the wastewater into nitrogen gas and nitrate nitrogen. The
heterotrophic denitrifying bacteria perform denitrification
reaction to transfer nitrate nitrogen and at least some residual
COD in the wastewater into ammonium nitrogen.
[0035] For acclimating the microorganisms in the second fluidized
chamber 311, activesludge carrying the second microorganisms may be
input to the second fluidized chamber 311. As the acclimation
proceeds, at least some microorganisms are attached to the second
granular carriers 32 and grow. In one example, activesludge
acquired from a landfill-leachate treatment facility in Taipei,
Taiwan was used. The activesludge was input during the startup
stage of the nitrogen-removing fluidized bed reactor 30. In the
startup stage of the nitrogen-removing fluidized bed reactor 30,
the activesludge was first input to the fluidized chamber of the
nitrogen-removing fluidized bed reactor 30. The nitrogen-removing
fluidized bed reactor 30 was operated in the startup stage with the
conditions listed in Table II below. In the example, no sludge
discharge was performed during the startup stage.
TABLE-US-00002 TABLE II Item Condition Temperature Room Temperature
Flow 2 L/min Sludge Retention Time Indefinite Duration Sludge
Concentration MLSS: 4725 mg/L MLVSS: 3510 mg/L
[0036] Then, wastewater was introduced into the second fluidized
chamber 311 through the second lower opening 313 of the
nitrogen-removing fluidized bed reactor 30. The wastewater used is
secondary settling pool wastewater coming from the secondary
settling pool of Taoyuan Wastewater Treatment Plant (Taiwan). The
quality of the wastewater is shown in Table III. Therein, TTN
refers to total target nitrogen, and total target nitrogen
concentration is the sum of the concentration values of ammonium
nitrogen, nitrite nitrogen, and nitrate nitrogen.
TABLE-US-00003 TABLE III Concentration Concentration Parameter
(mg/L) Parameter (mg/L) Ammonium Nitrogen 26 .+-. 4 COD 25 .+-. 16
Nitrite Nitrogen 0 .+-. 0 TSS 7 .+-. 8 Nitrate Nitrogen 2 .+-. 1
VSS 4 .+-. 3 TTN 28 .+-. 5
[0037] After the nitrogen-removing fluidized bed reactor 30 is
started, the second granular carriers 32 are carried by the
wastewater and suspend in the second fluidized chamber 311. The
second microorganisms attached to and growing on the second
granular carriers 32 undergo partial nitrification reaction,
anammox reaction and denitrification reaction at the same time in
the second fluidized chamber 311. The wastewater flows into the
second fluidized chamber 311 through the second lower opening 313,
and then passes through the second upper opening 312, the second
bottom opening 331 and the second outfall 332 of the second
sedimentation tank 33. The wastewater has a hydraulic retention
time in the second fluidized chamber 311 of 12-24 hours. In one
example, the hydraulic retention time for the nitrogen-removing
fluidized bed reactor 30 was 24 hours for Days 1-28, and 18 hours
for Days 29-63.
[0038] The test results are provided in Table IV below and in FIGS.
2 and 3. As evidenced, the total average ammonium nitrogen removal
rate is 98.3%. The removal rate was as high as 93.5% on the first
day of reaction and stayed steadily above 70% since Day 1, and
above 80% since Day 9, with an average at 99.7%. To discuss the
ammonium nitrogen removal rate with consideration of different
lengths of hydraulic retention time, the 24 h hydraulic retention
time (for Days 1-28) led to an average ammonium nitrogen removal
rate of 96.1% and the 18 h hydraulic retention time (for Days
29-63) led to an average ammonium nitrogen removal rate of 99.7%.
On the other hand, the total average TTN removal rate is 91.3%. The
TTN removal rate achieved 75.8% on Day 1, and stayed steadily above
80% since Day 9, with an average at 95.6%. The 24 h hydraulic
retention time (for Days 1-28) led to an average TTN removal rate
of 87.2%, and the 18 h hydraulic retention time (for Days 29-63)
led to an average TTN removal rate of 96.3%.
TABLE-US-00004 TABLE IV Hydraulic Retention Time (HRT) Parameter 18
Hours 24 Hours TTN 1 .+-. 1 mg/L 2 .+-. 0 mg/L Ammonium Nitrogen 0
.+-. 0 mg/L 0 .+-. 0 mg/L Nitrite Nitrogen 0 .+-. 0 mg/L 0 .+-. 0
mg/L Nitrate Nitrogen 1 .+-. 1 mg/L 2 .+-. 0 mg/L COD 13 .+-. 5
mg/L 17 .+-. 3 mg/L TSS 2 .+-. 5 mg/L 2 .+-. 1 mg/L VSS 1 .+-. 1
mg/L 2 .+-. 1 mg/L
[0039] It is evident that the nitrogen-removing fluidized bed
reactor 30 of the present invention provides effective nitrogen
removal even for wastewater having low ammonium nitrogen
concentration. Additionally, the present invention significantly
reduces the startup time as compared to the known treatment methods
or to the use of other reactors. For example, the system and method
disclosed in Taiwan Patent No. 201429884 involve the use of a
sequencing batch reactor. According to one example provided in the
prior patent, synthesized wastewater was introduced in the startup
stage and microorganisms such as nitrifying bacteria, anammox
bacteria and heterotrophic denitrifying bacteria were used to
remove nitrogen from the synthesized wastewater. The synthesized
wastewater had its ammonium nitrogen concentration of 400-600 mg/L.
With these settings, it takes about 90 days to complete the startup
stage and reach stable TTN removal rate above 80%, and the ammonium
nitrogen removal rate was not steady and close to 100% until Day
330. Daverey et al. (Achlesh Daverey, Nien-Tzu Hung, Kasturi Dutta,
Jih-Gaw LinChen. 2013. Ambient temperature SNAD process treating
anaerobic digester liquor of swine wastewater. Bioresource
Technology 141: 191-198) also used a sequencing batch reactor to
treat swine wastewater. During the startup stage, the ammonium
nitrogen removal rate did not steady until Day 60-70, after which
the rate stayed at 80%, and the TTN removal rate did not reach 75%
until Day 75, and finally reached 80% after 480 days from the
beginning. Keluskar et al. (Radhika Keluskar, Anuradha Nerurkar,
Anjana Desai. 2013. Development of a simultaneous partial
nitrification, anaerobic ammonia oxidation and denitrification
(SNAD) bench scale process for removal of ammonia from effluent of
a fertilizer industry. Bioresource Technology 130: 390-397) instead
used a cylindrical reactor for fertilizer industry wastewater.
During the startup stage, it took almost 30 days for the ammonium
nitrogen removal rate to reach 80%.
[0040] Generally speaking, when the efficiency of nitrogen removal
is stable above 80%, the system is deemed as started. With this
definition, it is found that the disclosed nitrogen-removing
fluidized bed reactor helps significantly reduce the required
startup time. It is also found that the nitrogen-removing fluidized
bed reactor is applicable to wastewater that contains low
concentration of ammonium nitrogen, such as municipal wastewater
that usually has its ammonium nitrogen concentration of 20-85 mg/L.
The conclusion overturns the traditional knowledge saying that
anammox bacteria are ineffective in treating domestic
wastewater.
[0041] It is to be noted that acclimation of the first
microorganisms and acclimation of the second microorganisms may be
conducted separately. In this case, the carbon-removing anaerobic
fluidized bed reactor 10 and the nitrogen-removing fluidized bed
reactor 30 are connected only after the both microorganisms have
been acclimated. The anaerobic fluidized membrane reactor 20 is
aimed at removing suspended solids from wastewater. Thus, in one
possible embodiment, the anaerobic fluidized membrane reactor 20
may be omitted, in which case the wastewater drained by the first
outfall 132 is introduced into the second fluidized chamber 311
through the second lower opening 313. In another possible
embodiment, an additional fluidized membrane reactor may be
provided downstream the nitrogen-removing fluidized bed reactor for
removing suspended solids from wastewater. While the
carbon-removing anaerobic fluidized bed reactor 10, the anaerobic
fluidized membrane reactor 20 and the nitrogen-removing fluidized
bed reactor 30 in the present embodiment all include additional
sedimentation tanks 15, 25, 35 for facilitating sediment of
suspended solids, these sedimentation tanks 15, 25, 35 may be
omitted in other embodiments.
[0042] To sum up, the disclosed wastewater treatment system is
effective in reducing COD and nitrogenous compounds in wastewater
and is applicable to domestic wastewater that contains low
concentration of target matters. The process can generate biogas
like methane, which can be further converted into energy. Also,
suspended solid concentration in the effluent can be significantly
reduced to ensure environmentally conformable water emission.
Hence, the present invention does possess great potential to become
the next-generation technology for biological wastewater
treatment.
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