This is part two of a paper about the potential environmental impacts of treated effluent from a wastewater treatment plant (WWTP) discharging to the Detroit River in Windsor, Ontario, Canada. The WWTP uses conventional activated sludge with nitrification.
The assessment was conducted over six months using a variety of established tests, including in vitro cell-based screening assays, as well as acute, chronic and full-life cycle in vivo exposures. Effluent monitoring included pharmaceutically active compounds and endocrine disrupting compounds.
No tests reported significant toxicity. However, enhanced algal growth was observed in a Pseudokerchneriella subcapitata growth inhibition test. In full life-cycle fathead minnow exposure, liver-somatic index changes were noted in exposed fish – increases for males, decreases for females – and production of viable fry decreased. Neither alteration is thought biologically significant. Because the effluent is diluted substantially by the receiving water, the level of risk posed to aquatic receptors and the environment is probably negligible.