Kinetics of Pulp and Paper Wastewater Treatment by High Sludge Retention Time Activated Sludge Process

Abstract

Paper and pulp industrial processes lead to the discharge of wastewater that contains high pollutants concentrations into the environment, which subsequently contaminate freshwater. Thus, it necessitates a sustainable treatment approach. This study focused on the start-up of the bench-scale activated sludge system fed with pulp and paper wastewater to verify the influence of HRT, wastewater concentration, and sugarcane bagasse on COD and ammonia removal efficiencies during the treatment process. An activated sludge process was operated at a flow rate of 5 L/day, while the reactor kept running at 72 h, 48 h, and 24 h HRT, respectively. Wastewater concentrations were set at 1039, 3158, 5248 mgCOD//L and 13.74, 40.37, 67.04 mgNH4+-N/L corresponding to 10, 50 and 100% respectively. Findings revealed high removal efficiencies up to 98.11% and 92.67% for COD and ammonia, respectively. After treatment, effluent concentrations for both parameters have satisfactorily met the Standard "A" standard limits for industrial discharge at 48 hours HRT. Therefore, further testing is not required. The First order and Modified Stover-Kincannon models evaluated substrate removal rates. In the Modified Stover–Kincannon model, high correlation coefficients R2 of 0.9999 and 0.9998 were obtained for COD and ammonia, respectively. Unfortunately, the activated sludge process in the bioreactor could not be described by the first-order kinetic model. The modified Stover-Kincannon model proved to best suit the experimental data.