TY - JOUR
T1 - Long-term formation of microbial products in a sequencing batch reactor
AU - Ni, Bing Jie
AU - Rittmann, Bruce
AU - Fang, Fang
AU - Xu, Juan
AU - Yu, Han Qing
N1 - Funding Information:
The authors wish to thank the Natural Science Foundation of China ( 50625825 , 50738006 and 50828802 ), and the Key Special Program on the S&T for the Pollution Control and Treatment of Water Bodies ( 2008ZX07316-002 and 2008ZX07010-005 ) for the support of this study.
PY - 2010/7
Y1 - 2010/7
N2 - Activated sludge in a sequencing batch reactor (SBR) is subjected to alternating feast-and-famine conditions, which may result in the enhanced production of microbial products: extracellular polymeric substances (EPS), soluble microbial products (SMP), and internal storage products (XSTO). In this work, the long-term formation of these three microbial products by activated sludge in an SBR is investigated using an expanded unified model with a parallel experimental study. We also use the model to compare the impacts in an SBR to those in a continuous-flow activated sludge system. The model captures all experimental trends for all components with solids retention time (SRT) for global steady state and within a cycle. At an SRT of 20 days, the active microorganisms constitute about 28% of the mixed liquor volatile suspended solids (MLVSS); the remaining biomass is comprised of residual inert biomass (XI) of 40%, EPS of 31%, and XSTO of ∼1%. The active biomass becomes a smaller fraction with the increasing SRT, while the inert biomass becomes increasingly dominant. For soluble components, effluent chemical oxygen demand (COD) is dominated by SMP, which varies to some degree in a cycle, peaking as external substrate becomes depleted. Within the SBR cycle, external substrate (S) declines strongly in the first part of the cycle, and SMP shows a small peak at the time of S depletion. XSTO is the only biomass component that varies significantly during the cycle. It peaks at the time that the input substrate (S) is depleted. Simulation for a continuous-flow activated sludge system and comparison with an SBR reveals that the constant " famine" conditions of the continuous system lead to lower EPS and XSTO, but higher MLVSS and XI.
AB - Activated sludge in a sequencing batch reactor (SBR) is subjected to alternating feast-and-famine conditions, which may result in the enhanced production of microbial products: extracellular polymeric substances (EPS), soluble microbial products (SMP), and internal storage products (XSTO). In this work, the long-term formation of these three microbial products by activated sludge in an SBR is investigated using an expanded unified model with a parallel experimental study. We also use the model to compare the impacts in an SBR to those in a continuous-flow activated sludge system. The model captures all experimental trends for all components with solids retention time (SRT) for global steady state and within a cycle. At an SRT of 20 days, the active microorganisms constitute about 28% of the mixed liquor volatile suspended solids (MLVSS); the remaining biomass is comprised of residual inert biomass (XI) of 40%, EPS of 31%, and XSTO of ∼1%. The active biomass becomes a smaller fraction with the increasing SRT, while the inert biomass becomes increasingly dominant. For soluble components, effluent chemical oxygen demand (COD) is dominated by SMP, which varies to some degree in a cycle, peaking as external substrate becomes depleted. Within the SBR cycle, external substrate (S) declines strongly in the first part of the cycle, and SMP shows a small peak at the time of S depletion. XSTO is the only biomass component that varies significantly during the cycle. It peaks at the time that the input substrate (S) is depleted. Simulation for a continuous-flow activated sludge system and comparison with an SBR reveals that the constant " famine" conditions of the continuous system lead to lower EPS and XSTO, but higher MLVSS and XI.
KW - Activated sludge
KW - Extracellular polymeric substances (EPS)
KW - Internal storage products (X)
KW - Sequencing batch reactor (SBR)
KW - Solids retention time (SRT)
KW - Soluble microbial products (SMP)
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U2 - 10.1016/j.watres.2010.04.035
DO - 10.1016/j.watres.2010.04.035
M3 - Article
C2 - 20537674
AN - SCOPUS:77953807420
VL - 44
SP - 3787
EP - 3796
JO - Water Research
JF - Water Research
SN - 0043-1354
IS - 13
ER -