Influence of Quaternary Ammonium Compounds on Activated Sludge Yield and Their Removal Efficiency

The influence of benzyl quaternary ammonium compounds(BAC)on COD removal and sludge yield in activated sludge system was investigated,and the removal efficiency of BAC by activated sludge was studied.The results show that the BAC have significant inhibitory effects on the sludge yield and its ability in substrate removal.When BAC concentration is increased from 0 to 10 mg/L,the removal rate of COD is decreased from 51.4% to 1.28% and the sludge yield is decreased from 0.76 to 0.09 gVSS/gCOD after 6 h.When BAC concentration is 20 mg/L,the substrate removal by sludge and its growth stop.The removal of BAC from the wastewater is achieved mainly via rapid adsorption on the sludge,and the removal rates of BAC are 95.6%,93.1% and 90.8% when their initial concentrations are 5,10 and 20 mg/L respectively.BAC can be degraded by the activated sludge,and the degradation needs a relative long time.The degradation of BAC follows the first order kinetics model,and the degradation half life is(10.33±0.66)h.