An Add-on Nitrifying Membrane Bioreactor as Effluent Polishing Technique for 17α -Ethinylestradiol

摘要

17a-ethinylestradiol (EE2), the active compound of the contraceptive pill, is a recalcitrant estrogen with a high endocrine disrupting potency. This compound is not adequately removed in the current wastewater treatment plants (WWTP). Increasing concern about the fate of low-level concentrations of endocrine disruptors stimulates research on alternative methods for WWTP effluent polishing. The aim of this study was to establish an innovative and effective biological removal technique for EE2 by means of a nitrifier enrichment culture (NEC) applied in a membrane bioreactor (MBR). In batch incubation tests, the NEC was able to remove EE2 from both synthetic minimal medium and WWTP effluent (maximum removal rate of 9 μg EE2 g-1 VSS h-1). The role of nitrification was demonstrated by means of a specific test in which nitrification was selectively inhibited. Application of the nitrifying consortium in a MBR resulted in a continuous removal of EE2, in combination with a complete nitrification. Variation of the ammonium concentration in the influent pointed out that an optimal EE2 removal efficiency of 99 % was possible at an environmentally relevant influent concentration of 83 ng EE2 L-1 and a minimal ammonium concentration of 1 NH4 +-N mg L-1. Consequently, the advanced removal of EE2 from WWTP effluent can be achieved without the addition of supplementary nitrogen. This research opens new perspectives to remove estrogenic compounds from WWTP effluents. The application of nitrifying consortia in an add-on MBR system can offer a sustainable solution for these point sources of endocrine disruptors in the environment.