Évaluation de l'impact des rejets de station d'épuration de la région De Bouzedjar d'Ain Temouchent sur la qualité des eaux de surface : étude physico-chimique et microbiologique.

Abstract

This work focuses on evaluating the performance of the Bouzedjar wastewater treatment plant, located in the Aïn Témouchent province in Algeria. Operated by the National Sanitation Office (ONA), this station treats domestic wastewater using a biological process based on activated sludge, before discharging the treated water into the natural environment. The main objective of this work is to compare the physico-chemical and organoleptic characteristics of the water at the inlet and outlet of the plant in order to assess the effectiveness of the treatment. For this purpose, sampling was carried out in February 2025, followed by laboratory analyses of the collected samples. The parameters studied include pH, electrical conductivity, turbidity, COD, DBO5, dissolved oxygen, suspended solids (SS), nutrients (total nitrogen, nitrates, nitrites, phosphate), and sedimentation volume (V30). The results showed a clear improvement in water quality after treatment, particularly through the disappearance of unpleasant odors and the transparency of the water. The organic load was significantly reduced, with BOD5 dropping from 80 to 10 mg/l and DCO from 192 to 36 mg/l. Dissolved oxygen increased from 2 to 6 mg/l, and suspended solids decreased from 86 to 10 mg/l. Nutrients were partially removed, reducing the risk of eutrophication. However, the electrical conductivity remained high after treatment (1500 μS/cm), indicating the persistence of dissolved salts, which limits the potential for reuse without tertiary treatment. In conclusion, while the station shows good performance in primary and secondary treatment, improvements are still needed to reduce the concentration of dissolved salts, especially if the treated water is to be reused in agriculture or sensitive environments.