The peroxidase toxicity assay for the rapid evaluation of municipal effluent quality

Rapid and cost-effective tests for the evaluation of industrial and municipal effluents are urgently needed for environmental monitoring. In this context, peroxidase (PER) activity has been proposed as an early-warning biosensor for assessing the water quality of various wastewater discharges and leachates. The peroxidase-toxicity (Perotox) assay includes 0.1 µg/mL PER, albumin, DNA (for the DNA protection index), 0.001% monounsaturated Tween-80, and the substrates luminol and H2O2. The results revealed that an initial burst of luminescence was followed by a steady decrease in luminescence within the first minute, accompanied by periodic (cyclic) changes in the intermediate compound III (CIII) of PER. When urban effluents were added, PER activity was inhibited, with a concomitant increase in lipid peroxidation, indicating oxidative damage. The reduction in PER activity was also associated with the collapse in the periodic formation of CIII, alongside a steady increase in CIII over time. The addition of DNA to the reaction mixture helped mitigate the inhibition of PER by certain effluents, enabling the calculation of a DNA protection index. The levels of polystyrene (PS) in the organic fraction of the effluents were higher in the primary aeration lagoon (36 µg/L) compared to secondary lagoons and membrane filtration (< 16 µg/L). Data analysis revealed that PER activity was negatively correlated with population size (r = -0.34) and the levels of PS materials (r = -0.56). In conclusion, the Perotox assay is proposed as a rapid screening tool for identifying potentially toxic environmental complex mixtures, such as municipal effluents.