Screening of municipal effluents with the peroxidase toxicity assay

Abstract The peroxidase (Per) reaction is a quick and inexpensive biosensor for the screening of environmental contaminants. The purpose of this study was to screen various municipal wastewaters before and after 7 different types of treatment processes. Wastewater samples before (influents) and after the following treatments (effluent) were tested using the Per activity test: advanced biofiltration, biofiltration, aerated lagoons, secondary aeration sludge, trickling filter, secondary membrane filtration, and primary. The influents and effluents were collected for 3 days composites and concentrated to 500 X on a reverse-phase (C18) extraction cartridge. The ethanol extracts were examined for dissolved organic carbon, plastic-like materials, polyaromatic hydrocarbons and polystyrene nanoplastics. The samples were then tested using the Per reaction alone and in the presence of DNA to detect DNA binding agents. The result show that population size tended to increase Per activity and 60% of the effluents decreased Per activity leading to H2O2 persistence. More advanced treatments (biofiltration, membrane biofiltration, secondary aeration) produced stronger changes from the corresponding untreated influents. The addition of DNA during the Per reaction revealed that population size had no influence and that significant changes occurred in 60% of treated effluents suggesting release of genotoxic compounds in the aquatic environment by most treated wastewaters. The toxic implications of these results to aquatic organisms are discussed.