Elimination of Micropollutants from Biologically Treated Municipal Wastewater using Combined Membrane and Activated Carbon-based Adsorption Processes

Abstract

In the present article different process configurations based on microfiltration and activated carbon adsorption for the removal of micropollutants from biologically treated municipal wastewater are investigated. In the PAC contact process a PAC dose of 5 mg/l and PAC contact times of 12, 24 and 48 h were tested. Longer PAC contact times improve the removal; a PAC dosage of 5 mg/l at a PAC contact time of 48 h is not sufficient for the elimination of a wide spectrum of substances by ≥ 80 %. Higher PAC dosages could not be investigated due to strong membrane fouling. Pre-filtration with a microfiltration system has no effect on the elimination of micropollutants by granular activated carbon filters. However, the time interval for filter backwash was reduced from 1.4 d to 10.3 d due to extended solids removal. Higher empty bed contact times are advantageous for a higher wastewater throughput with the same objective: for the most micropollutants the criteria c/c0 of 0.05 and c/c0 0.20 were reached at a higher wastewater throughput by an empty bed contact time of 12.5 min. The evaluation methodology has a significant influence on the interpretation of the upcoming activated carbon exchange: compared with a conventional evaluation of the present concentrations in the influent and effluent (c/c0) higher throughputs were achieved with an integrated approach. The reduction of (filtrated) COD below the threshold of 20 mg/l according to the German Wastewater Levy Act was guaranteed by the activated carbon filters during the trial period.