Occurrence and removal of progestogens from wastewater treatment plants in China: Spatiotemporal variation and process comparison

This study investigated the overall occurrence and spatiotemporal variation of 19 progestogens in 608 samples collected from 17 wastewater treatment plants (WWTPs) distributed across China during four seasons. The aqueous removal efficiencies of progestogens were calculated and the efficacies of process segments, secondary and advanced processes, and process units in the removal of progestogens were explored. The results indicated that progestogens were widely detected in investigating WWTPs, with the progesterone, dydrogesterone, dienogest, ethisterone, and norethindrone were always dominant in the influent, secondary effluent, final effluent, and excess sludge. Seasonally, the influent exhibited more variability than the other matrices, that 10 progestogens concentrations varied significantly during the four seasons. Spatially, the influent concentrations of progestogens were generally higher in northern WWTPs than that in southern WWTPs during spring and summer. Eight progestogens were stably removed by the WWTPs across seasons, and most progestogens varied considerably in removal in different WWTPs. The conventional process segment was the dominant contributor to progestogen removal. The anaerobic-anoxic-oxic process and a combined process consisting of densadeg and cloth media filter and ultraviolet disinfection showed the highest removal of progestogens among various secondary and advanced treatment processes, respectively. Mass balance analysis showed that most progestogens were effectively eliminated in the aerobic unit, with biodegradation being the primary removal pathway. This study presents the first picture of the spatiotemporal dynamics of the distribution of progestogens in WWTPs of China and provides valuable information for better understanding of the occurrence and removal of progestogens in WWTPs.