Anaerobic processes in activated sludge

Dirk De Beer; Andreas Schramm; Cecilia M. Santegoeds; Helle K. Nielsen

doi:10.1016/S0273-1223(98)00166-8

Anaerobic processes in activated sludge

Dirk De Beer^*, Andreas Schramm, Cecilia M. Santegoeds, Helle K. Nielsen

^*Corresponding author af dette arbejde

Institut for Biologi - Mikrobiologi

Publikation: Bidrag til tidsskrift/Konferencebidrag i tidsskrift /Bidrag til avis › Konferenceartikel › Forskning › peer review

21 Citationer (Scopus)

Abstract

We found anoxic zones in aerated activated sludge flocs, and demonstrated denitrification under normal operating conditions. Sulfate reduction was not found. Micro-environments and microbial conversions in flocs from bulking and non-bulking activated sludge were determined with microsensors for H₂S, O₂, NO(2^-) and N(O3^-). Denitrification and sulfate reduction rates were measured with ¹⁵N- and ³⁵S-tracer techniques. We showed that under normal reactor conditions (ca. 20% air saturation) anoxic zones develop within flocs allowing denitrification. The denitrification rates amounted to 40% of the rates under anoxic conditions. At 100% air saturation no anoxic zones were found and no denitrification occurred. However, in flocs from bulking sludge (at 20% air saturation) anoxic zones were absent and denitrification did not occur. In bulking sludge only at total anoxia was denitrification found. Confocal microscopy showed that flocs from bulking sludge were much looser than those from non-bulking sludge. The absence of anoxic zones and of denitrification was attributed to the open floc structure, allowing advective oxygen transport. Sulfate reduction was not detected in any of the sludges tested by microsensors or by tracer techniques even under anoxic conditions. This indicates that the sulfur cycle (sulfate reduction and sulfide oxidation) does not play a role in mineralization processes and bulking in activated sludge. Preliminary molecular work (in situ hybridization with the 16S-rRNA probe SRB385) indicated the presence of small amounts of sulfate reducing bacteria in all sludges. Either the probe is not specific or the sulfate reducers present are not active under reactor conditions.

Originalsprog	Engelsk
Tidsskrift	Water Science and Technology
Vol/bind	37
Nummer	4-5
Sider (fra-til)	605-608
Antal sider	4
ISSN	0273-1223
DOI	https://doi.org/10.1016/S0273-1223(98)00166-8
Status	Udgivet - 10 jun. 1998
Begivenhed	Proceedings of the 1997 2nd International Conference on Microorganisms in Activated Sludge and Biofilm Processes - Berkeley, CA, USA Varighed: 21 jul. 1997 → 23 jul. 1997

Konference

Konference	Proceedings of the 1997 2nd International Conference on Microorganisms in Activated Sludge and Biofilm Processes
By	Berkeley, CA, USA
Periode	21/07/1997 → 23/07/1997

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Citationsformater

@inproceedings{f9156ece625a4655948b393f027df6ec,

title = "Anaerobic processes in activated sludge",

abstract = "We found anoxic zones in aerated activated sludge flocs, and demonstrated denitrification under normal operating conditions. Sulfate reduction was not found. Micro-environments and microbial conversions in flocs from bulking and non-bulking activated sludge were determined with microsensors for H2S, O2, NO(2-) and N(O3-). Denitrification and sulfate reduction rates were measured with 15N- and 35S-tracer techniques. We showed that under normal reactor conditions (ca. 20% air saturation) anoxic zones develop within flocs allowing denitrification. The denitrification rates amounted to 40% of the rates under anoxic conditions. At 100% air saturation no anoxic zones were found and no denitrification occurred. However, in flocs from bulking sludge (at 20% air saturation) anoxic zones were absent and denitrification did not occur. In bulking sludge only at total anoxia was denitrification found. Confocal microscopy showed that flocs from bulking sludge were much looser than those from non-bulking sludge. The absence of anoxic zones and of denitrification was attributed to the open floc structure, allowing advective oxygen transport. Sulfate reduction was not detected in any of the sludges tested by microsensors or by tracer techniques even under anoxic conditions. This indicates that the sulfur cycle (sulfate reduction and sulfide oxidation) does not play a role in mineralization processes and bulking in activated sludge. Preliminary molecular work (in situ hybridization with the 16S-rRNA probe SRB385) indicated the presence of small amounts of sulfate reducing bacteria in all sludges. Either the probe is not specific or the sulfate reducers present are not active under reactor conditions.",

keywords = "Activated sludge, Anoxic, Confocal microscopy, Denitrification, Micro-environment, Microsensor, Oxic, Sulfate reduction",

author = "{De Beer}, Dirk and Andreas Schramm and Santegoeds, {Cecilia M.} and Nielsen, {Helle K.}",

year = "1998",

month = jun,

day = "10",

doi = "10.1016/S0273-1223(98)00166-8",

language = "English",

volume = "37",

pages = "605--608",

journal = "Water Science and Technology",

issn = "0273-1223",

publisher = "IWA Publishing",

number = "4-5",

note = "Proceedings of the 1997 2nd International Conference on Microorganisms in Activated Sludge and Biofilm Processes ; Conference date: 21-07-1997 Through 23-07-1997",

}

TY - GEN

T1 - Anaerobic processes in activated sludge

AU - De Beer, Dirk

AU - Schramm, Andreas

AU - Santegoeds, Cecilia M.

AU - Nielsen, Helle K.

PY - 1998/6/10

Y1 - 1998/6/10

N2 - We found anoxic zones in aerated activated sludge flocs, and demonstrated denitrification under normal operating conditions. Sulfate reduction was not found. Micro-environments and microbial conversions in flocs from bulking and non-bulking activated sludge were determined with microsensors for H2S, O2, NO(2-) and N(O3-). Denitrification and sulfate reduction rates were measured with 15N- and 35S-tracer techniques. We showed that under normal reactor conditions (ca. 20% air saturation) anoxic zones develop within flocs allowing denitrification. The denitrification rates amounted to 40% of the rates under anoxic conditions. At 100% air saturation no anoxic zones were found and no denitrification occurred. However, in flocs from bulking sludge (at 20% air saturation) anoxic zones were absent and denitrification did not occur. In bulking sludge only at total anoxia was denitrification found. Confocal microscopy showed that flocs from bulking sludge were much looser than those from non-bulking sludge. The absence of anoxic zones and of denitrification was attributed to the open floc structure, allowing advective oxygen transport. Sulfate reduction was not detected in any of the sludges tested by microsensors or by tracer techniques even under anoxic conditions. This indicates that the sulfur cycle (sulfate reduction and sulfide oxidation) does not play a role in mineralization processes and bulking in activated sludge. Preliminary molecular work (in situ hybridization with the 16S-rRNA probe SRB385) indicated the presence of small amounts of sulfate reducing bacteria in all sludges. Either the probe is not specific or the sulfate reducers present are not active under reactor conditions.

AB - We found anoxic zones in aerated activated sludge flocs, and demonstrated denitrification under normal operating conditions. Sulfate reduction was not found. Micro-environments and microbial conversions in flocs from bulking and non-bulking activated sludge were determined with microsensors for H2S, O2, NO(2-) and N(O3-). Denitrification and sulfate reduction rates were measured with 15N- and 35S-tracer techniques. We showed that under normal reactor conditions (ca. 20% air saturation) anoxic zones develop within flocs allowing denitrification. The denitrification rates amounted to 40% of the rates under anoxic conditions. At 100% air saturation no anoxic zones were found and no denitrification occurred. However, in flocs from bulking sludge (at 20% air saturation) anoxic zones were absent and denitrification did not occur. In bulking sludge only at total anoxia was denitrification found. Confocal microscopy showed that flocs from bulking sludge were much looser than those from non-bulking sludge. The absence of anoxic zones and of denitrification was attributed to the open floc structure, allowing advective oxygen transport. Sulfate reduction was not detected in any of the sludges tested by microsensors or by tracer techniques even under anoxic conditions. This indicates that the sulfur cycle (sulfate reduction and sulfide oxidation) does not play a role in mineralization processes and bulking in activated sludge. Preliminary molecular work (in situ hybridization with the 16S-rRNA probe SRB385) indicated the presence of small amounts of sulfate reducing bacteria in all sludges. Either the probe is not specific or the sulfate reducers present are not active under reactor conditions.

KW - Activated sludge

KW - Anoxic

KW - Confocal microscopy

KW - Denitrification

KW - Micro-environment

KW - Microsensor

KW - Oxic

KW - Sulfate reduction

UR - http://www.scopus.com/inward/record.url?scp=0031804547&partnerID=8YFLogxK

U2 - 10.1016/S0273-1223(98)00166-8

DO - 10.1016/S0273-1223(98)00166-8

M3 - Conference article

AN - SCOPUS:0031804547

SN - 0273-1223

VL - 37

SP - 605

EP - 608

JO - Water Science and Technology

JF - Water Science and Technology

IS - 4-5

T2 - Proceedings of the 1997 2nd International Conference on Microorganisms in Activated Sludge and Biofilm Processes

Y2 - 21 July 1997 through 23 July 1997

ER -

Anaerobic processes in activated sludge

Abstract

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