Assessment of treatment water effects on macrobenthic invertebrates in an urban stream

Increasing human settlements and the use of fertilizers and detergents in urban areas contribute to eutrophication of freshwater. Macroinvertebrates may be adversely affected by this treatment water because its physicochemical properties may be altered. In order to determine how this treatment affects macrobenthic invertebrates, sampling carried out at three stations (stream connected to the polluted natural lake, stream coming from the Biological Waste Water Treatment Plant and stream that mix of both) located in the Sarıyer district of Istanbul, Türkiye in two seasons. Biological Monitoring Working Party (BMWP), Average Score Per Taxon (ASPT), Shannon-Wiener, and Margalef indexes were performed. It was found that all stations were highly polluted and poorly diverse, based on the results of the study. Additionally, the nMDS results showed no significant difference between stations and seasons. Polluted water indicates that the wastewater treatment plant is not performing effectively. Also in the RDA analysis, which is one of the results of this study, Physidae showed a positive correlation with TDS and pH, while dissolved oxygen and Chironomidae family were grouped together. This study revealed that the physicochemical properties of the treated water were very similar to those of the stream flowing from the polluted lake. There is no significant difference between ecological parameters and biological variables before and after the treatment of wastewater in the study area. In light of these results, it is apparent that the wastewater treatment plant is not providing adequate treatment. In order to fully understand the environmental effects of these treatment plants, further research is required.