Document Detail


Waste activated sludge hydrolysis and short-chain fatty acids accumulation under mesophilic and thermophilic conditions: effect of pH.
MedLine Citation:
PMID:  19555988     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The effect of pH (4.0-11.0) on waste activated sludge (WAS) hydrolysis and short-chain fatty acids (SCFAs) accumulation under mesophilic and thermophilic conditions were investigated. The WAS hydrolysis increased markedly in thermophilic fermentation compared to mesophilic fermentation at any pH investigated. The hydrolysis at alkaline pHs (8.0-11.0) was greater than that at acidic pHs, but both of the acidic and alkaline hydrolysis was higher than that pH uncontrolled under either mesophilic or thermophilic conditions. No matter in mesophilic or thermophilic fermentation, the accumulation of SCFAs at alkaline pHs was greater than at acidic or uncontrolled pHs. The optimum SCFAs accumulation was 0.298g COD/g volatile suspended solids (VSS) with mesophilic fermentation, and 0.368 with thermophilic fermentation, which was observed respectively at pH 9.0 and fermentation time 5 d and pH 8.0 and time 9 d. The maximum SCFAs productions reported in this study were much greater than that in the literature. The analysis of the SCFAs composition showed that acetic acid was the prevalent acid in the accumulated SCFAs at any pH investigated under both temperatures, followed by propionic acid and n-valeric acid. Nevertheless, during the entire mesophilic and thermophilic fermentation the activity of methanogens was inhibited severely at acid or alkaline pHs, and the highest methane concentration was obtained at pH 7.0 in most cases. The studies of carbon mass balance showed that during WAS fermentation the reduction of VSS decreased with the increase of pH, and the thermophilic VSS reduction was greater than the mesophilic one. Further investigation indicated that most of the reduced VSS was converted to soluble protein and carbohydrate and SCFAs in two fermentations systems, while little formed methane and carbon dioxide.
Authors:
Peng Zhang; Yinguang Chen; Qi Zhou
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2009-06-06
Journal Detail:
Title:  Water research     Volume:  43     ISSN:  1879-2448     ISO Abbreviation:  Water Res.     Publication Date:  2009 Aug 
Date Detail:
Created Date:  2009-07-28     Completed Date:  2009-08-07     Revised Date:  2009-08-20    
Medline Journal Info:
Nlm Unique ID:  0105072     Medline TA:  Water Res     Country:  England    
Other Details:
Languages:  eng     Pagination:  3735-42     Citation Subset:  IM    
Affiliation:
State Key Laboratory of Pollution Control and Resources Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai, China.
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MeSH Terms
Descriptor/Qualifier:
Biodegradation, Environmental
Bioreactors
Carbohydrates / analysis
Carbon / analysis
Fatty Acids / metabolism*
Fermentation
Hydrogen-Ion Concentration*
Hydrolysis
Membrane Glycoproteins / analysis
Methane / analysis
Sewage / chemistry*
Temperature*
Chemical
Reg. No./Substance:
0/Carbohydrates; 0/Fatty Acids; 0/Membrane Glycoproteins; 0/S-layer proteins; 0/Sewage; 74-82-8/Methane; 7440-44-0/Carbon

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