Estrone biodegradation in laboratory-scale systems designed for total nitrogen removal from wastewater

Abstract

Changes in regional regulations are causing a shift towards the implementation of total nitrogen removal technologies. Conventional nitrification systems do not remove total nitrogen, instead only oxidizing ammonia and ammonium in the influent to nitrate. Conventional nitrification does, however, result in degradation of estrone (E1), a major contributor to the estrogenicity of wastewater treatment plant (WWTP) effluent. The objective of this research was to provide guidance on the impact that changes in wastewater treatment practices could have on E1 degradation. This was accomplished by comparing E1 removal in a laboratory-scale conventional nitrification system with that in a range of idealized laboratory-scale systems designed to remove total nitrogen from wastewater: the modified Ludzack-Ettinger (MLE) system (a two-stage anaerobic–aerobic system with recycle), a granular activated sludge system (cycled anaerobic–aerobic), a sequencing batch reactor (cycled anaerobic–aerobic), and an anaerobic ammonia oxidation (anammox) system. As anticipated, E1 removal was excellent when fed to the nitrification, MLE, and sequencing batch reactors, at >96% mean E1 loss. The granular activated sludge system operated in our laboratory failed to remove E1, which was perhaps not unexpected given the high COD loading under which our system was operated. Despite the anaerobic nature of anammox, it also resulted in excellent E1 removal (95% mean E1 loss) without concomitant 17β-estradiol production. This work demonstrates that the choice of nitrogen removal technology used by a treatment plant could have an impact on the estrogenicity of WWTP effluent, but low energy total nitrogen removal systems do exist that are capable of excellent E1 removal.