Process investigation on activated sludge in-series system treating pharmaceutical wastewater

A lab-scale study on completely-mixed activated sludge aeration tank in-series (CMAS in-series) treating pharmaceutical wastewater from a Harbin pharmacy plant was conducted to optimize the practical full-scale plant operation parameters and to explore the removal of various pollutants. In CMAS in-series system, such operational conditions like F/M=0.1-0.2 or 0.8-1.5 gCOD/(gMLSS·d), SRT=8-10 d, ρ (DO)=1-3 mg/L and temperature 27-34°C benefited sludge settling ability and obtained the removal rate of COD and TSS over 90% and 95%, respectively. Specific oxygen uptake rate of SOUR_avg=49.5 mgO₂/(gMLSS·h) indicated good sludge activity in the aeration tanks of CMAS in-series. Increasing the tank number of CMAS in-series system favored sludge settling ability under the same HRT. Bio-degradation of COD in this system followed a mathematical model of ρ(COD_e)=ρ (COD₀) × e^-at. Practical project operation performance from the simulation results showed that the system was effective and steady, and the effluent met the first level criteria of the Integrated Wastewater Discharge Standard (GB8978-1996).