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

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.