The researchers studied how treating wastewater at the Kermanshah wastewater treatment plant in Iran affects the nearby Qarasou River. They collected water samples and found that the treatment process reduced levels of pollutants like total suspended solids, nitrate, phosphorous, biological oxygen demand, and chemical oxygen demand. Acidity and dissolved oxygen levels slightly increased due to aeration during treatment. An environmental change index showed minimal impact on the river, with an average efficiency of 80-92% in removing pollutants. Overall, the treatment plant's process is effective and does not harm the environment.