Grit Separation Module Performance and Influencing Factors for Grit Removal Efficiency from Activated Sludge

Abstract

In wastewater treatment plants, grit accumulation reduces the ratio of volatile suspended solids/total suspended solids (i.e., reduces biomass in activated sludge), and therefore impairs the efficiency of wastewater treatment. A grit separation module was developed to reduce grit accumulation in such wastewater treatment systems, and a pilot scale field study was conducted at a full-scale wastewater treatment plant in Chongqing, China. The results suggest that feed pressure (working pressure) and outlet ratio (the ratio between the underflow outlet and overflow outlet diameter) were the most important control parameter and structural parameter, respectively. Grit separation efficiency was satisfactory when the feed pressure was controlled between 0.15 and 0.175 MPa and the outlet ratio K was between 0.4 and 0.6. The greatest grit separation efficiency was obtained at a cone angle of 20°, an overflow outlet diameter of 22 mm, an underflow outlet diameter of 13 mm, and a feed pressure of 0.175 MPa. Under these conditions 48% of the grit contained in feed sludge was recovered in the underflow stream with a split rate of 0.17, suggesting that the grit can efficiently be separated from activated sludge by the module presented in this study.