Objective: In addition to macro-pollutants detected in surface waters, micro-pollutants in water bodies and the toxicity of these pollutants have become increasingly important in recent years. The removal efficiency of these pollutants reaching domestic and industrial wastewater and wastewater treatment plants has increased to up to 80%. However, considering the wastewater throughput of metropolitan cities, it is known that these pollutants reach surface waters with the discharge at the end of the plant, as the increased load presses on the removal efficiency. Our aim in this study is to determine the acute toxicity in water samples from surface waters in Istanbul.

Methods: The study was conducted primarily in areas where effluent from advanced biological treatment plants discharged via the stream mixes with surface waters.

Results: An acute toxicity test with bioluminescent bacteria (Aliivbrio fischeri) was performed and the results were interpreted using analytical methods. “Hormesis” data were generally found in the results from these stations. Noteworthy are the numerical results of the “extremely toxic” values in the surface water of the Ambarlı station and the “very toxic” values of the Atakoy station.

Conclusion: Pollutants and micropollutants contained in the effluents of industrial facilities that illegally discharge into the sewerage system and enter the treatment plant can ecotoxicologically affect water quality at the point where they mix with surface waters. Rapid, sensitive and microscale toxicity tests are recommended as a promising tool for integrated environmental quality assessment.