Assessing closed-circuit reverse osmosis (CCRO) efficiency in removing contaminants of emerging concern (CECs) in a high-recovery water reclamation pilot study

ABSTRACT Contaminants of emerging concern (CECs) are increasingly recognized due to the proliferation of recycled water projects worldwide, particularly in California, aimed at addressing water scarcity and escalating demands. This research investigates the efficacy of closed-circuit reverse osmosis (CCRO) in treating tertiary effluent from municipal wastewater within a high-recovery framework, conducted as a pilot study at the San Jacinto Valley Regional Water Reclamation Facility. The primary aim of this pilot-scale investigation was to subject the CCRO process to elevated recovery rates and assess its capability in treating municipal wastewater. A selected list of the removal rates of CECs was examined and analyzed. Furthermore, the performance of membrane process at recovery rates ranging from 90 to 95% was evaluated. Results indicate that conventional municipal wastewater treatment effectively eliminates the majority of select CECs; however, certain contaminants may bypass conventional treatment processes. Our findings demonstrate that CECs such as select N-nitrosamines, hormones, and pharmaceuticals can be efficiently removed by the CCRO system at high recovery rates of 90–95%. Hydrophobic molecules like fluoxetine, tris(1,3-dichloro-2-propyl)phosphate, and tris(chloropropyl) phosphate exhibited high rejection rates by the rRO membrane, while some hydrophilic constituents such as N-nitrosodimethylamine and caffeine were not effectively rejected by the membrane process.