Poor and inadequate sanitation systems have been considered not only a human health issue, but also an environmental threat that instigates climate change. Nine heavy metals—arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn)—were evaluated in influent and effluent water samples from four wastewater treatment plants in the Durban metropolis, KwaZulu-Natal, South Africa. The results indicate that the mean concentrations of all the heavy metals in the influent samples ranged from 0.122 to 1.808 mg/L, while the effluent samples had a concentration ranging from 0.118 to 0.854 mg/L. Iron was found to be in the highest concentration and the concentration of Co was the lowest across the wastewater treatment plants. The levels for most of the heavy metals in this study were found to be above the recommended maximum concentrations in surface and effluent waters as stipulated by the World Health Organization, United States Environmental Protection Agency, Food and Agriculture Organization, and the Department of Water Affairs and Forestry of South Africa. According to the toxicity effect due to non-carcinogenic risks, As, Pb, Cr, and Cd are considered to be of medium risk in this study, indicating that a probable adverse health risk is very likely to occur. Additionally, the cancer risk (RI) values were lower than 10⁻³, which shows that cancer development is very likely in individuals who are exposed. Cancer development associated with dermal absorption is quite negligible; thereby, it does not raise any concerns.

Triclosan (TCS) and triclocarban (TCC) are antimicrobial agents that have been used in personal care and consumer products in the past decades. In this study, influent, effluent, and sludge samples collected in selected wastewater treatment plants across the Durban metropolis were qualitatively and quantitatively investigated. It was revealed that the concentration of TCS ranged from 1.906 to 73.462 µg/L, from 1.732 to 6.980 µg/L, and from 0.138 to 2.455 µg/kg in influent, effluent, and sludge samples, respectively. The concentrations of TCC were found to be between 0.320 and 45.261 µg/L, <LOQ–1.103 µg/L, and from 0.107 to 8.827 µg/kg in the influent, effluent, and sludge samples, respectively. Higher concentrations of TCS as compared with TCC were observed in the aqueous samples. However, the concentrations of TCC in the sludge samples were significantly higher than the level of TCS. More water solubility of TCS could be responsible for the observed trend in the influent and effluent samples, while the trend observed in the sludge could be due to the more hydrophobicity character of TCC. The results of this study indicated that substantial amounts of TCS and TCC are been removed during the treatment process which could be a major reason for the decline in the levels recorded in the effluent samples, therefore, reducing the amount of the TCS and TCC that would eventually end up in the surface rivers. Qualitative analyses of the samples indicated the presence of caffeine, tert-butylhydroquinone, chloroxylenol, phenol, 4-(1,1,3,3-tetramethyl butyl), and dimethyl-bisphenol A. Further investigative ecological risk assessment studies are crucial due to the potential threat the contaminants may pose to aquatic lives and humans.