The effect of operational parameters on the dewatering characteristics of municipal wastewater sludges

Abstract

This research study examined the effect operational parameters, dissolved oxygen (D.O.) and food to microorganism ratio (F:M ratio) had on the thickening and dewatering from laboratory-scale and full-scale activated sludge treatment processes. Differences observed in sludge thickening and dewatering at CWWTP and BWWTP were investigated. Data was collected and operational parameters at full-scale facilities monitored. A laboratory-scale activated sludge reactor was constructed and operated on line with the CWWTP, which experienced filamentous bulking conditions since startup and operational parameters of the reactor monitored. Laboratory-scale experiments involved varying mixed liquor D.O. concentration and mean cell residence time (MCRT) and observing the resultant sludge thickening and dewatering characteristics.

Increase in mixed liquor D.O. concentration, F:M ratio and reduction of MCRT at CWWTP resulted in improved sludge thickening and dewatering performance. Results showed sludge thickening characteristics were enhanced at D.O. concentrations greater than 3.0 mg/1 and less favorable at D.O. concentrations less than 2.0 mg/1. No trend correlation existed between aeration basin D.O. concentration and sludge dewatering resistance in the range of 3.0 to 7.0 mg/1. Correlation between laboratory-scale and full-scale activated sludge systems demonstrated that laboratory-scale reactor units can be. utilized to predict plant operational changes in relation to sludge thickening and dewatering performance.