Disinfection of treated wastewater as an essential purification step for safe urban reuse: a comparative pilot study of UV- and ClO2-disinfection systems for urban reuse applications in China

Abstract

Disinfection of wastewater is vital in addressing the potential health risks of urban water reuse. To compare the applicability of wastewater disinfection methods other than chlorine, identical pilot plants that used ultraviolet (UV) irradiation and chlorine dioxide (ClO2) dosing were installed at municipal wastewater treatment plants in Shanghai, China and Darmstadt, Germany. The investigation included public health and environmental aspects associated with the two disinfection methods. The results of the pilot-scale studies suggest that, in order to comply with Chinese water quality standards for urban water reuse, it is advisable to have a tertiary treatment before wastewater disinfection. Both methods were able to achieve a 4 log10 reduction in both total coliforms and Escherichia coli (E. coli). There was no evidence for regrowth of E. coli. However, after an initial 3 log10 reduction, HPC increased within 48 h by more than 10-fold after UV irradiation as well as after low doses of ClO2. An increase in acute toxicity was detected after dosing with ClO2 but not after UV irradiation.