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| Influencial factors of extracellular polymer substances in activated sludge hydrolysis and acidification |
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Abstract Variation of extracellular polymer substances (EPS) during activated sludge hydrolysis-acidification process and influencial factors including temperature, pH, sludge characteristic and sludge concentration were investigated at ambient temperature by batch experiments. pH and sludge characteristic had an important effect on the EPS composition and amount. Under strong acidic (pH =3, 4) and strong basic condition (pH=11) the yields of EPS was one time higher than that of neutral condition. However, under strong acidic condition, much more biologic cells were broken and DNA accounted for 20% of total EPS, while carbohydrate mass accounted for 80% of total EPS under strong alkaline condition. The yield of EPS produced by A/O sludge was the highest with an average value of 41.1 mg/gVSS followed by SBR sludge, A2/O sludge and OD sludge. The ratios of polysaccharide to protein (φ) for OD sludge was the lowest. When temperature increased from 18℃ to 35℃, the EPS yields grew by 50% and the percentage of polysaccharide in total EPS rised gradually. EPS yields could be 38.1 mg/gVSS when the MLSS increased from 2000 mg/L to 6000 mg/L, however, the EPS yields would decrease to 23.1 mg/gVSS if the MLSS increased to 8000 mg/L.
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Received: 15 May 2009
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