Toxicity assessment of wastewater using a battery of bioassays in two textile wastewater treatment plants from a large industrial park in Guangxi, Southwest China.

Textile effluents are important sources of pollutants in aquatic environments. The textile industry in China has been relocating from developed to less developed regions, yet the potential environmental impact of textile effluents remains unclear. Here, we investigated the acute toxicity of wastewater collected from different processing units of two textile wastewater treatment plants (WWTPs) in a large industrial park in Guangxi province (Southwest China), using whole effluent toxicity testing. Moreover, we explored the relationships between the toxicity of wastewater and its characteristics, including physicochemical parameters, heavy metals, fluorescence intensity, and non-persistent and persistent organic pollutants. Untreated textile effluents were highly toxic to all test organisms, with toxic units reaching 42.9 for lux-modified bacteria, 14.0 for green algae, 10.1 for duckweed, and 17.3 for zebrafish embryos. Their toxicity was reduced significantly but not removed completely, following treatment processes that included coagulation, anaerobic-aerobic process, Fenton oxidation process, chlorine disinfection and wetland treatment systems. In the wetland effluent, both toxicity and physicochemical parameters met the textile effluent discharge standards in China and other countries. The toxicity of wastewater was associated with various characteristics, such as chemical oxygen demand (COD), fluorescence intensity related to fulvic acid-like materials, 4-nonylphenol, bisphenol A, bis(2-ethylhexyl) phthalate, perfluorobutane sulfonic acid, and acenaphthene. These results suggest the effectiveness of the investigated WWTPs in treating textile effluents concerning both physicochemical parameters and acute toxicity. The present study highlights the importance of integrating ecotoxicological data alongside chemical data to enhance the risk assessment and evaluation of the environmental safety of effluent discharges.