Pesticide and Pharmaceutical Abatement within Nonpotable and Potable Reuse Treatment Trains

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Organisms can be exposed to sewage-derived contaminants via stormwater runoff when nonpotable reuse effluents are used for irrigation and when reverse osmosis (RO) concentrates from potable reuse systems are discharged. To characterize mitigation of ecotoxic potentials, we measured 11 pesticides and 6 pharmaceuticals in samples collected along 6 nonpotable and 5 potable reuse trains. While previous research focused on pharmaceuticals, our results indicated that the pesticides diuron, fipronil, and imidacloprid have high potential to cause ecological hazards. Anaerobic secondary effluents featured lower concentrations for most contaminants. The filtration and disinfection processes used in nonpotable reuse trains each reduced diuron, fipronil, imidacloprid, and metoprolol concentrations by <25%, although higher reductions were observed for sulfamethoxazole by media filtration (93%) and for clothianidin (80%) and diclofenac (65%) by disinfection. RO treatment in potable reuse trains rendered contaminants nondetectable in all cases except for one unusually high clothianidin concentration measured during one event, although subsequent advanced oxidation process (AOP) treatment removed the clothianidin. However, RO treatment produced concentrates with contaminant concentrations 4.4-fold higher than in secondary effluents. Ozonation/biological activated carbon (O₃/BAC) filtration upstream of RO reduced contaminants in RO concentrates by >87% relative to secondary effluents for most contaminants except imidacloprid (∼20–40%).