Rheological characteristics of mixture of raw primary and thickened excess activated sludge: impact of mixing ratio, solid concentration, temperature and sludge age

Abstract

AbstractWastewater treatment process generates large quantities of sludge from different operational steps. The rheological behaviour of sewage sludge at different steps of wastewater treatment plant is useful for the design, operation, optimization of polymer dosing, hydrodynamics and mixing of anaerobic digestion and for efficient sludge management. In this research work, the impacts of solid concentration, temperature, mixing ratio and ageing of sludge on the rheological behaviour of mixture of raw primary and thickened excess activated sludge (TEAS) (mixed sludge) were investigated. Solid concentration, temperature, primary to TEAS mixing ratio, and sludge age were found to affect the viscosity, yield stress, flow index and flow consistency of mixed sludge. The decrease in total solid (TS) concentration of mixed sludge from 30 to 20 g/L resulted in significant decrease of yield stress from 7.4 to 1.1 Pa (85% reduction). The decrease in mixing ratio of TEAS to raw primary sludge from 80 to 20% resulted...