Membrane biorreactor, reverse osmosis and UV/H₂O₂ process integration for ethinylestradiol removal: A cost-benefit...

The presence of 17α-ethinylestradiol (EE2) in water bodies and its potential risks to human health and the environment have been frequently described in the literature, in addition to its limited removal in conventional wastewater treatment plants. Many studies have evaluated this removal by advanced processes, including photodegradation and membrane separation. A significant number of studies also assess the economic analysis of these technologies. However, few works articulate both perspectives: the specificity involved in estrogen removal and economic analysis. Given this gap, this work evaluates the synergies involved in the integration of reverse osmosis (RO) and advanced oxidative processes by UV/H₂O₂ (AOP) in the post-treatment of membrane bioreactor (MBR) effluents. To this end, the integrated plant possibilities were represented through a superstructure that integrated EE2 removal and cost models of each process. The use of a Hook and Jeeves optimizer considering these processes standard operating conditions made it possible to determine the percentage of stream division for each equipment and even the absence of any of these in an integrated plant with lower cost and EE2 concentration output below the recommended limit by the European Union (0.035 ng.L^-1). For EE2 feed content up to 3 ng.L^-1, the lowest cost configuration is to route 20% of the MBR effluent to the AOP, 30% to the RO, and the remainder to a final mixer. For concentrations above 15 ng.L^-1, the sufficient and lowest cost configuration is the MBR-RO-AOP series. Intermediate values have a more advantageous integrated process configuration with the parallel and series configurations combined, with a stream distribution dependent on the feed concentration. Moreover, a parameter sensitivity analysis was performed, clarifying paths for design improvements and acting as a systematic guide for future work in this area. This analysis highlights that EE2 removal is more sensitive to temperature (1.04%), feed substrate concentration (-1.18%), solid retention time in the MBR (0.32%), and irradiance in AOP (-0.46%). Investment costs also proved to be decisive in the composition of the total cost, enhancing the relevance of the maturation process of these technologies in light of simple changes in operating parameters.