Ecotoxicological effects of disinfected wastewater effluents: a short review of in vivo toxicity bioassays on aquatic organisms

Wastewater disinfection has attracted attention with regard to fecal-oral transmission during the current coronavirus disease 2019 (COVID-19) outbreak in China. Disinfection reduces the risk posed by waterborne pathogens; however, it threatens ecological safety. Comprising residual disinfectants, disinfection byproducts (DBPs), and other contaminants, disinfected wastewater effluents have a negative impact on aquatic organisms as well as on the balance of the aquatic ecosystem of the recipient water body. Here, we reviewed the in vivo toxicity bioassays of disinfected wastewater effluents on the aquatic organisms at different trophic levels, including freshwater organisms and marine organisms. Associated variables, i.e., total suspended solids (TSSs), ammonia nitrogen (NH3-N), residual disinfectants, and features of the effluent (water temperature and sampling season), can significantly influence the results of these in vivo toxicity bioassays. Each typical test organism has its own pros and cons, where the species type, life stages, and test endpoints have crucial influences on the bioassays; therefore, they should be taken into account before and during the studies on ecotoxicological effects. More efforts should be expended toward conducting more practical bioassays involving the scenarios of the recipient water body in order to better simulate real ecotoxicological effects of disinfected wastewater effluents; extended exposure time should be considered to gain additional insights into the long-term or pass-generation ecotoxicological effects, approaching true levels in the recipient water body.