A comprehensive assessment of membrane bioreactor contaminant removal efficacy through analytical chemistry, fish exposures, and microbiome characterization.

This article evaluates the efficacy of membrane bioreactor treatment (MBR) compared to traditional oxidation ditch (OXI) secondary treatment in removing contaminants of emerging concern (CECs) from municipal wastewater effluent and their biological impacts. Using a municipal wastewater treatment plant with split primary effluent (PRI), the study combined analytical chemistry, 21-day fathead minnow exposure experiments, and microbiome characterization of fish and effluent to assess treatment performance. Both MBR and OXI substantially reduced most CECs relative to PRI, with pesticides and some pharmaceuticals showing recalcitrance to both methods; MBR notably reduced microbial abundance and diversity more than OXI. Fish exposed to OXI or MBR effluents exhibited only subtle biological differences without adverse apical outcomes, consistent with low exposure:activity ratios derived from chemical analyses. The findings suggest MBR is a viable alternative to OXI, potentially obviating the need for tertiary disinfection, though further research is needed on persistent pesticides and ecological effects under natural conditions.