Uncoupled metabolism stimulated by chemical uncoupler and oxic-settling-anaerobic combined process to reduce excess sludge production |
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Authors: | Fen Xia Ye Ying Li |
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Institution: | (1) Department of Chemical Engineering, Ningbo University of Technology, Cuibai Road, 20 Houhe Lane, 315016 Ningbo, China |
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Abstract: | The effects of three uncoupled metabolic systems (conventional activated sludge process with the addition of 3,3′,4′,5-tetrachlorosalicylanilide
TCS], oxic-settling-anaerobic OSA] process modified by insertion of a sludge-holding tank in the sludge return line, and
TCS and OSA combined process) on reducing excess sludge production were studied. Compared with the control conventional activated
sludge process, the most effective system was the combined process, which could reduce excess sludge production by 46.90%.
The 180-d operation results confirmed that TCS is an effective chemical uncoupler in reducing the sludge yield but that it
had an adverse effect on substrate removal capability, effluent nitrogen concentration, and sludge settleability. The OSA
process decreased excess sludge production by only 26% but had less adverse effect on effluent quality and could improve sludge
settleability. The effluent total phosphorous concentration of the three systems was slightly lower than of the control unit.
Microbial populations were monitored by both microscopic and molecular biologic analysis method (polymerase chain reaction
PCR]-denaturing gradient gel electrophoresis DGGE]). The presence of TCS caused metazoans to disappear and decreased the
number and activity of protozoa. PCR amplification of 16S rRNA and sequent DGGE analysis found a shift in the diversity of
the predominant species. The results imply that OSA combined with the chemical uncoupler process may effectively reduce excess
sludge yield and not affect process performance significantly. |
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Keywords: | Activated sludge process excess sludge reduction oxicsettling-an aerobic process 3 3′ 4′ 5-tetrachlorosalicylanilide uncoupler |
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