Fates of Benzotriazoles, Benzothiazoles, and p-Phenylenediamines in Wastewater Treatment Plants in Malaysia and Sri Lanka

Benzotriazoles, benzothiazoles, and p-phenylenediamines discharged from wastewater treatment plants (WWTPs) are of concern because they pose risks to aquatic organisms. South/Southeast Asian countries are heavily populated and face challenges in providing clean water. Here, the chemical fates in five WWTPs in Malaysia and Sri Lanka were investigated and their environmental risks were assessed. Benzotriazoles and benzothiazoles were dominant (at concentrations of 3.4–21000 and 7.0–2500 ng/L, respectively). The p-phenylenediamine concentrations were much lower (not detected─60 ng/L). The WWTP removal efficiencies varied widely, from negative to 100%, lower than in developed countries, indicating the WWTP elimination capacities were limited and secondary releases of the chemicals from particles could occur. The highest total consumptions (72–5000 mg/(d·1000 inhabitants)) were for a hospital WWTP in Malaysia, mainly contributed by benzotriazoles (81%). The daily total chemical mass loadings in effluents from WWTPs in Malaysia and Sri Lanka were 0.04–48 and 0.27–9.4 g/d, respectively. Benzothiazoles and N-(1,3-dimethylbutyl)-N′-phenyl-1,4-phenylenediamine-quinone pose medium–strong risks to aquatic organisms and should be prioritized for wastewater management. The results improve our understanding of emerging contaminant fates and effects in WWTPs and how management systems could be modified to ensure clean water.