A range of toxicity bioassays which account for the biological effects of the pollutants has been developed to assess the potential toxicity risk of chemical mixtures against living cells. The current study aimed to determine the cytotoxic and estrogenic effects of treated wastewater effluents discharging into a main River in Tunisia. According to preliminary chemical analysis, high organic pollution was detected for some samples of treated wastewater due to high levels of chemical oxygen demand which exceeded the Tunisian guidelines. On one hand, significant cytotoxicity on Caco-2 human intestinal epithelial cells was registered for the highest concentration of water samples using MTT assay. In fact, the cell viability decrease was dose dependent for all the tested samples. On the other hand, Modified E-screen assay confirmed the presence of estrogenic compounds in the effluent samples. Estrogenic potencies induced a significant proliferation level of MCF-7 cells in a dose dependent manner. Thus, water samples may contain diversity of organic contaminants considered as potentially hazardous complex mixtures and representing a potential environmental risk for surface water. The implemented assays pointed out the insufficiency of the applied treatment technology to completely eliminate toxic micropollutants from treated effluent which may threaten aquatic life and human health as well. (C) 2015 The Authors. Published by Elsevier Ltd.