Biological treatment of dairy wastewater using activated sludge

The objective of the research was to evaluate the performance of a laboratory-scale biological treatment unit for dairy-industry wastewater and to determine the kinetic parameters for the activated sludge process. A laboratory-scale treatment unit comprising an aeration tank and final clarifier was used for this purpose. The treatment unit was operated continuously for three months by varying the hydraulic retention times from 2 to 12 days. The biological oxygen demand (BOD) of the influent and effluent and the mixed liquor suspended solids of the aeration tank were determined at various detention times to generate data for the kinetic coefficients. The kinetic coefficients k (maximum substrate utilization rate), K-s (half velocity constant), Y (cell yield coefficient), and K-d (decay coefficient) were found to be 4.46 day(-1), 534 mg/l, 0.714, and 0.038 day(-1), respectively, based on the BOD. These coefficients may be used for the design of activated sludge process facilities for dairy wastewater.