Techno-economic evaluation and comparison of PAC-MBR and ozonation-UV revamping for organic micro-pollutants removal from urban reclaimed wastewater

Abstract The presence of sewage-borne Organic Micro-Pollutants (OMP) in Wastewater Treatment Plants (WWTP) effluents represents an increasing concern when water is reclaimed for irrigation or even indirect potable reuse. During eighteen months, an innovative hybrid water reclamation scheme based on a Membrane Biological Reactor (MBR) enhanced with Powder Activated Carbon (PAC) was operated at pilot-scale (70 m 3 /d) in order to compare it with state-of-the art Wastewater Reclamation System (WWRS) also revamped with a final step of ozonation-UV. Removal of persistent OMP, water quality and treatment costs were evaluated and compared for the different treatment schemes. OMP removal efficiency results for the different schemes concluded that established technologies, such as physico-chemical and filtration systems as well as MBR, do not remove significantly (>15%) the most recalcitrant compounds. The upgrading of these two systems through the addition of ozonation-UV step and PAC dosing allowed improving average recalcitrant OMP removal to 85 ± 2 and 75 ± 5%, respectively. In term of costs, PAC-MBR represents an increase of 37% of costs regarding conventional systems but presents improvements of 50% reduction in space and water quality. On the other hand, ozonation requires up to a 15% increase of foot-print; nevertheless, represents lower costs and lower carbon footprint. Ozonation-UV seems to be the best option for upgrading existing facilities, while PAC-MBR should be considered when space represents a critical limitation and produced water is reused for high water quality purposes.