activated sludge wastewater treatment processes and control of foam formation

8/19/2019 Activated Sludge Wastewater Treatment Processes and Control of Foam Formation

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Activated sludge

wastewater treatmentprocesses and control of

foam formationsd / March 12, 2014

Abstract: activated sludge aeration tank serious bubble phenomenon is a common

problem, mainly due to Nocardioorm actinomycetes and Microthri! parvicella

abnormal gro"th caused by the genus# Microbial cell surace hydrophobicity

$%&'(, sludge retention time $&)*(, p' value, dissolved o!ygen $+( is such an

important actor in the gro"th o -lamentous bacteria# .oam control methods are

spraying "ater, adding chemicals, reducing the mean cell residence time,

adusting the p' euent, additional biological selector, a continuous packing

reactors#

ey"ords: activated sludge oam Nocardioorm actinomycetes Microthri!

parvicella .ormation and %ontrol

0 3ntroduction

currently , the "orld"ide most urban se"age treatment plant using activated

sludge treatment process# ne common problem is that aeration pool suraces

oten produce serious bubble, a lot o oam to make aeration pool surace is

covered, i the overo" rom the pool "ill cause the e!ternal device and the

e!ternal "all o the pollution, seriously a5ecting the surrounding environment, to

66*7 operation and management brought di8culties, but also resorted to "ater

9uality deterioration# According to the survey o domestic se"age treatment

plant, most o them to varying degrees by the impact o the oam problem,especially the use o delay aeration 7rocess "aste"ater treatment plant even

more so#

1 oam ormation

activated sludge process, the ormation o oam generally have the ollo"ing

orms, including crat oam ormed during the initial run, denitri-cation blistering,

surace oaming suractant and bio oam 1;#


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no" generally believed that the main reason or the ormation o bio?oam is:

under the inuence o various actors, resulting in -lamentous microorganisms

such as bacteria and actinomycetes o the abnormal gro"th o -lamentous

bacteria is higher than the speci-c gro"th rate o oc bacteria, -lamentous

bacteria and the large speci-c surace area, thereore, -lamentous bacteria to

obtain substances and o!idation euent


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.igure 4 Nocardia amarae and Microthri! parvicella D;

.igure 4# Nocardia amarae and Microthri! parvicella D;

studies sho" that -lamentous bacteria microbial cell surace hydrophobicity orhydrophobic $cell surace hydrophobicity, %&' ( is the ormation o bio?oam and

stabiliBe the important reasons# 'elen &tratton $1FFG( and so isolated rom the

biological oam nocardiorm and )hodococcus rhodochrous other bacteria, ungal

acid on the cell surace component $mycolic acid content(,

*able 1 "ith the main bubble ormation genus

*able 1# Main bacteria involved in oams orming

No Name gram of bacteria species and morphology 1 Nocardia amarae G+ actinomycetes

(actinomycete), Twiggy mycelium 2 Nocardia pinesis G+ actinomycetes, pine-like 3

Rhodococcus sp. G+ actinomycetes, branched hyphae 4 Microthrix parvicella G+ filamentous

bacteria (filament), no sheath unbranched, filamentous 5 Eikelboom Type0092 G-FCB doors,

filamentous bacteria 6 Eikelboom Type0411 G-FCB doors, filamentous bacteria 7 Eikelboom

Type1863 G-FCB doors, class Proteobacteria, filamentous bacteria 8 Eikelboom Type0803 G-

FCB doors, class Proteobacteria, filamentous bacteria

Note: .%< gate means .le!ibacter?%ytophaga?


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*able 2 dominant -lamentous bacteria associated "ith the condition F;

*able 2# %onditions being related to predominant -lamentous bacteria

generate conditions silk like Species in the low DO Microthrix parvicella, S. Natans, 1701 lowF / M Microthrix parvicella, 0041,0092 completely mixed bioreactor H. Hydrossis, Nocardia

spp., 021N, 1851,1701 septic waste / sulfide Beggiatoa, Thiothrix spp., 0914 undernourished

S. Natans, Thiothrix spp., 021N; may have H. Hydrossis, 0041 low pH control of fungal

bacteria 2

oam bubble ormation mechanism based on its inuencing actors can be

physical chemistry and biological control method o oams# Especially biological

control oam bubbles are actually not eliminate Microthri! parvicella other

bacteria produce, the main "ay is to create a suitable aeration system abnormal

gro"th o -lamentous bacteria environment in the activated sludge inhibiting

e!cessive prolieration, silk like bacteria and oc?orming bacteria to maintain abalanced ratio o gro"th#

2#1 physical and chemical methods to control oam

J spraying "ater

spraying "ater or "ater droplets can break bubbles oating in the "ater in order

to reduce oam# the role o non?polar

characteristics# &ince the presence o these t"o points, a large number o ne"

stable oam is di8cult to generate, and the oam layer on the surace o the "ater

turbulence, bubbles continuously broken by the shearing orce, the surace o

"ater as continuous evaporation o the "ater -lm bubble, the bubble continuously

crushing the oam layer also gradually disappear 10;#

lo" concentration o '22 is a more commonly used to eliminate oam agent in

the activated sludge dosing "hen dosing lo" concentrations o '22, the

concentration su8cient to kill the e!tensor surace Boogloea out o the

-lamentous bacteria, only some biological o!idation residues and eliminate

metabolic processes occurring to!ins, puriy Loogloea environment or bacterial

gro"th, and promote the advantages Boogloea bacteria gro"th, so Boogloea


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bacteria and -lamentous bacteria gro"th reached a ne" e9uilibrium, so as to

achieve the purpose o controlling biological oam and "ater 9uality does not

deteriorate# '22 should in return sludge dosing, dosing concentration o 20

2mg '22 / $kg MC&&( 11;#

Oong"oo '"ang and other se"age plants through observation, laboratory tests

and -eld applications, the oam is ound in se"age typical seasonal occur, the

regulation o metabolism and kinetics are not very successul in suppressing

Microthri! parvicella overgro"th and oam generation, through the chlorine,

cationic polyacrylamide comparison o t"o chemical agents, in addition to

-lamentous bacteria ound poly9uaternary ammonium hydro!ide $9uaternary

ammonium?based anti?-lament polymer, A.7( is one o the most e5ective

physical Microthri! parvicella chemical methods to suppress e!cessive

prolieration, can e5ectively control the oam did not bring about changes in "ater

9uality are given 12;#

.urther, such as chlorine, oBone, and chlorinated polyethylene glycol pickling iron

and copper mi!ed "ith strong o!idiBing agents etc#, but also can be used as

deoamer#

2#2 biological methods to control oam

J lo"er mean cell residence time

lo"er mean cell residence time is a very e5ective method o controlling oam,

namely the use o real silk like bacteria mean generation time is longer in the

characteristics o oc?orming bacteria, inhibit e!cessive prolieration o

-lamentous bacteria, mean cell residence time is shorter, less -lamentous ungus,

the less oam#

K adusting the p' euent

study, the most suitable p' o the gro"th o Nocardia amarae I#G, most suitable

or the gro"th o Microthri! parvicella p' o I#I to G#0, the p' value is rom I#0

do"n to #0 to #D, can e5ectively control the e!cessive gro"th o these

organisms, reduced oam ormation 1=;#

P reduce aeration air input rate

reduces the aeration air input rate, one can reduce the aeration tank stripping

strength, slo"ing oating -lamentous bacteria speed second is to reduce the

concentration o dissolved o!ygen in the aeration tank, Nocardia amarae is strictly

aerobic bacteria in ano!ic or anaerobic conditions, di8cult to gro", but Microthri!parvicella able to endure the lack o o!ygen state# .urthermore, reducing the


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amount o aeration air input also a corresponding reduction o the ormation o

microbubbles, a reduction o -lamentous bacteria and actinomycetes oating

body o the carrier, thereby delaying the ormation o oam#

Q reu! anaerobic digester supernatant

tests sho"ed that anaerobic digester supernatant genus )hodococcus

rhodochrous can inhibit the gro"th o anaerobic digester supernatant back to the

e!posure *he method o the gas tank, aeration tank, the surace can also control

the ormation o oam# 'o"ever, due to the anaerobic digester supernatant

containing high concentrations o substrates and aerobic ammonia, "hich "ill

a5ect "ater 9uality, and should thereore be used "ith caution#

R additional biological selector

organisms are aerobic selector selector selector and hypo!ia are t"o, its purpose

is to make into the aeration tank o se"age sludge prior to reo" in "hich the

mi!ing, by adusting the . / M, + and other actors, the development o selective

oc?orming bacteria, inhibit e!cessive prolieration o -lamentous bacteria# 3n the

design o the selector, the selector re9uires sub?grid settings, and more generally

"ith 4 to D grid ma!imiBe selector -rst grid . / M value, the ormation o . / M

gradient also controls the selector hydraulic retention time, usually 10 to 1

minutes# Another study sho"ed that: aerobic selector can be controlled to some

e!tent Microthri! parvicella, but no maor impact on the genus Nocardia "hile

ano!ic selector control action or a genus Nocardia, but then Microthri! parvicella

"ithout much e5ect 14; #

S -ller using a continuous reactor

+#Mamais $1FFG(, also -nds no evidence that the anaerobic and ano!ic selector

can be absolutely successul spread and control Microthri! parvicella prolieration,

continuous o" and se9uencing batch e!periments sho"ed that the gro"th

control Microthri! parvicella the best "ay is to use a continuous o" reactor

packing, or t"o reasons: .irst, the use o oc?orming bacteria high adsorptioncapacity to remove a large number o slo"?biodegradable %+ &econd, to avoid

hydrolysis o colloidal material di5usion o soluble products G;#

= -eld e!amples


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2004 Nian 2 .ebruary 14 to .ebruary 1I period, aeration tank surace in a serious

bubble began to take to the aeration tank

"ater sprayed on the surace o the measures, but the deoaming e5ect is not

ideal# .ebruary 1G, taken to reduce the intensity o aeration air input measuresand the secondary settling tank into the "ater in the dosing o about 2C $0#mg /

C( o cationic polyacrylamide solution, continuous dosing seven days, observed

daily and recorded as a oam covering the percentage o the aeration tank, sho"n

in .igure 4# &tart adding the oam coverage has reached F0T, 20 .ebruary bubble

coverage dropped to I0 percent, to 24 .ebruary coverage dropped to 12T, then

stabiliBed at 10T#

.igure 4 aeration tank oam coverage "ith dosing time variation o cationic

polyacrylamide relationship

.igure 4# Uariation relationship bet"een bestre"ing rate o oams in aeration pool

and

adding time o acrylamide?based cationic polymer

4 %onclusion

activated sludge process conditions and mechanism o bubble remains

controversial, but the current study suggests that, mainly due to the genusNocardia and Microthri! parvicella abnormal gro"th, and its speci-c gro"th rate

higher than the oc oc?orming bacteria caused by the speci-c gro"th rate ,

Nocardia spp Microthri! parvicella and highly hydrophobic cell surace, migrate

and remain in the bubble surace, thus the bubble stability# .oaming phenomenon

"ith air > "ater interace concentration o hydrophobic compounds#

oams are mainly the physical and biochemical methods, by adding chemicals to

change the chemical nature o the surace o bacterial cells is still a common

method o controlling the bubble generation, and the "idely used ungicide

common negative role, because e!cessive or improper dosing position, "ill be a

substantial reduction reaction cell oc?orming bacteria and the number o total

biomass#

short, the current dosing chemicals commonly used method is only a stopgap

measure rather than simply solving approach, thereore, also through a deeper

and more practical biological methods o research, to -nd a more reasonable and

e5ective , more economical methods or the control o the genus Nocardia and

Microthri! parvicella gro"th and the ormation o oam, to ensure the normal

activated sludge process and e8cient operation#


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References

1; 6arrer V# Activated sludge bulking and oaming control M;# *echnomic

publishing %o# 3nc# Cancaster, 1FF4#

2; %hu @uang Oi, et al # *alking bubble 6aste"ater *reatment V;# &handongEnvironment, 1FFG,4:2F#

=; 7# Madoni, et al# *esting the control o -lamentous microorganisms responsible

or oaming in a ull?scale activated sludge plant running "ith initial aerobic or

ano!ic contact Bones V;#


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1=; Cee +ynasty, et al# activated sludge .rance biological oam ormation and

control V;# %hina 6ater X 6aste"ater, 2001,1I $4( :I=?ID#

14; %ha +', et al# 7rocess control actor inuencing nocardia populations in

activated sludge V;# 6at# Environ# )es, 1FF2,D4: =I?4=#

activated sludge wastewater treatment processes and control of foam formation

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