Performance assessment on combined process of the oxidation and Biological Activated Carbon filtration for removal of Chlorinated Volatile Organic Carbons from river water

Abstract

Due to their acute toxicity, the presence of Chlorinated Volatile Organic Carbons (CVOCs) in the Nakdong River (South Korea) is of increasing concern. Among numerous other micropollutants, these occur in the Nakdong River due to urbanization, industrial development, and farming in the basin. Simultaneously, the need to ensure proper drinking water supply has made reduction of the micropollutants in the river water increasingly important. In order to assess the performance of CVOC removal by the drinking water treatment processes in this study, batch and continuous experiments were conducted to investigate the effects of oxidation and activated carbon adsorption on removal of CVOCs in river water, and to evaluate the CVOC removal performance of an Advanced Drinking Water Treatment (ADWT) system. Influent concentrations of five CVOCs [<224.3 μg/L (1,1-dichloroethylene: 1,1-DCE); <468.4 μg/L (1,1,1-trichloroethane: 1,1,1-TCA); <16.4 μg/L (carbon tetrachloride: CT); <261.4 μg/L (trichloroethylene: TCE); and <63.9 μg/L (tetrachloroethylene: PCE)] were prepared by diluting CVOC stock solution with river water. Chlorination led to increases in all CVOC components with increasing chlorine dosage. In contrast, ozonation led to relatively high removal efficiencies of 30±10% with increasing ozone dosage. Biological Activated Carbon (BAC) filters achieved 3-9 times higher CVOC removal efficiencies than Powdered Activated Carbon (PAC), which had removal efficiencies of < 20%. Thus, the system configuration of preozonation-coagulation-sedimentation (lamella pulsator)-sand filtration-postozonation-BAC biofiltration was able to almost completely remove CVOCs, regardless of the influent concentration. This shows that a combination of BAC biofiltration and ozonation could provide an alternative to conventional chlorination and filtration processes for the efficient removal of CVOCs.