ABSTRACT: 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),
Ks (half velocity constant), Y (cell yield coefficient), and Kd (decay coefficient) were found to be 4.46 day