Powdered activated carbon addition to activated sludge in the treatment of landfill leachate

Abstract

Powdered activated carbon (PAC) addition to activated sludge is a convenient method in the treatment of wastewaters that contain high amounts of nonbiodegradable and inhibitory organics. In the biological treatment of leachate in combination with domestic wastewater, leachate constituents may exert adverse effects on the efficiency of the activated sludge process. The purpose of this study was to investigate the effectiveness and applicability of PAC added activated sludge systems in the treatment of leachate in combination with synthetic domestic wastewater. The first step in the experimental path of the study was the determination of adsorption characteristics of the activated carbon used in the study. The succeeding steps involved the biological treatment studies in PAC added activated sludge reactors. The second step was treatment of leachate in batch reactors. The third step was treatment in Semi-Continuously Fed Batch reactors which were used to simulate the Continuous-Flow Stirred Tank: Reactor (CFSTR). The fourth step was PAC addition to a continuous-flow activated sludge reactor. The results of the study demonstrated that PAC addition to activated sludge is a promising method for the treatment of leachate in combination with domestic wastewater. PAC addition resulted in considerable reductions in the effluent concentrations of organic matter due to the adsorption of nonbiodegradable organics. It was found that the removal of organic matter was a simple combination of adsorption and biodegradation in the PAC added activated sludge systems for the conditions encountered in this study. Also, bioregeneration of activated carbon hypothesis was not valid. But, PAC addition increased nitrification rates through the enhancement of nitrifier activities by adsorbing the inhibitory and/or toxic compounds in the leachate.