Pesticide and\nPharmaceutical Abatement within Nonpotable\nand Potable Reuse Treatment Trains

Organisms can be exposed to sewage-derived contaminants\nvia stormwater\nrunoff when nonpotable reuse effluents are used for irrigation and\nwhen reverse osmosis (RO) concentrates from potable reuse systems\nare discharged. To characterize mitigation of ecotoxic potentials,\nwe measured 11 pesticides and 6 pharmaceuticals in samples collected\nalong 6 nonpotable and 5 potable reuse trains. While previous research\nfocused on pharmaceuticals, our results indicated that the pesticides\ndiuron, fipronil, and imidacloprid have high potential to cause ecological\nhazards. Anaerobic secondary effluents featured lower concentrations\nfor most contaminants. The filtration and disinfection processes used\nin nonpotable reuse trains each reduced diuron, fipronil, imidacloprid,\nand metoprolol concentrations by <25%, although higher reductions\nwere observed for sulfamethoxazole by media filtration (93%) and for\nclothianidin (80%) and diclofenac (65%) by disinfection. RO treatment\nin potable reuse trains rendered contaminants nondetectable in all\ncases except for one unusually high clothianidin concentration measured\nduring one event, although subsequent advanced oxidation process (AOP)\ntreatment removed the clothianidin. However, RO treatment produced\nconcentrates with contaminant concentrations 4.4-fold higher than\nin secondary effluents. Ozonation/biological activated carbon (O<sub>3</sub>/BAC) filtration upstream of RO reduced contaminants in RO\nconcentrates by >87% relative to secondary effluents for most contaminants\nexcept imidacloprid (∼20–40%).