American Society of Civil Engineers

Rapid Determination of Wastewater Sludge Dewatering Performance Using Capillary Suction Timer

by Jianpeng Zhou, Ph.D., P.E., (Assistant Professor, Department of Civil Engineering, Southern Illinois University Edwardsville, IL 62026-1800 E-mail:
Section: Wastewater I, pp. 1-6, (doi:

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Document type: Conference Proceeding Paper
Part of: World Environmental and Water Resource Congress 2006: Examining the Confluence of Environmental and Water Concerns
Abstract: The handling of wastewater sludge is a significant challenge, because the amount of wastewater sludge is large, the handling, processing and final disposal of sludge are difficult and expensive, which could count for 40% of total operational costs of a wastewater treatment facility. It is important to determine rapidly the performance of sludge dewatering (solids recovery and sludge cake dryness) and to optimize timely the dosing of the conditioning chemical, so the operational cost can be reduced. This paper reports findings from a recent study that investigated the feasibility of using capillary suction timer (CST) as a tool to determine the performance of sludge dewatering. This laboratory research studied sludge samples taken from three different sludge treatment processes: mesophilic aerobic, mesophilic anaerobic, and thermophilic aerobic digestion. Two polymers, carrying high and low cationic charges, were used to condition a thermophilic aerobically digested sludge sample. Conditioned sludge was centrifuged at 2,000 rpm for 20 minutes. Experimental results revealed that when unconditioned sludge samples of various sources are compared, CST was not an appropriate indicator to predict quantitatively dewatering performance of sludge samples; when conditioned sludge samples (dosed by polymer at various rates) from a single source are considered, quantitative relationship exists between the solids concentration in the supernatant of the centrifuged sludge and CST of the uncentrifuged samples. Findings from this study suggest that CST can be used as an efficient tool to assist wastewater operators to assess rapidly the performance of dewatering process and make prompt decision for efficient and cost-effective operation of the dewatering process, which would help to reduce the costs of wastewater treatment facility operation.

ASCE Subject Headings:
Wastewater management