期刊
WATER RESEARCH
卷 43, 期 18, 页码 4617-4625出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.watres.2009.07.015
关键词
Conditioning; Dewatering; Rheology; Shear sensitivity; Yield stress; Enzyme
资金
- US National Science Foundation [0229293]
- Div Of Chem, Bioeng, Env, & Transp Sys
- Directorate For Engineering [0229293] Funding Source: National Science Foundation
Shear sensitivity of digested sludge was evaluated by two methods: a CST shear test and a strain sweep rheological method of measuring yield stress. Sludge pretreatment by an enzyme formulation was used to alter the sludge's response to shear and, potentially, to improve dewaterability. Also varied were the polymer conditioning dose and the amount of shear applied by mixing. A bench-scale device was then used to simulate dewatering by belt press in order to assess the CST shear tests and the rheological test. CST-based shear tests showed that the optimum chemical conditioner doses With low shear levels became sub-optimal with increasing mixing times. For all three polymer conditioners, longer shear times increased the dose requirements. When the polymer dose was held constant, and the extent of mixing varied, the CST test was a poor indicator of effects on dewaterability. The benefits of enzyme treatment, apparent by actual dewatering, were not predicted by the CST results. In contrast, yield stress values were significantly correlated with cake solids values, and inversely correlated with filtrate solids. Yield stress is not adequate by itself to predict final cake solids after dewatering, because enzyme pretreatment gave higher solids concentrations when both shear extent and initial yield stress were held constant. (C) 2009 Elsevier Ltd. All rights reserved.
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