Physicochemical and Bacteriological Quality of Surface Water Resources Receiving Common Wastewater Effluents in Drylands of Algeria

Abstract

The assessment of water quality and pollution of surface water resources is crucial to maintain the integrity of aquatic environments. This study aims at characterizing water physicochemical and bacteriological quality of Wadis of Biskra (northeastern Algeria). Water samples were collected monthly from three different Wadis receiving common wastewater effluents from the city of Biskra. Using standard methods, each sample underwent several analyses to determine physicochemical parameters (temperature, pH, electrical conductivity, turbidity, biological and chemical oxygen demand “BOD5 and COD”, and concentrations of suspended solid materials, dissolved oxygen, phosphate, nitrites, nitrates, and ammoniacal nitrogen) and bacterial quality (total coliforms, faecal coliforms, faecal streptococci, and sulfite-reducing Clostridia). Most of the measured physicochemical parameters reached unsuitable quality limits according to FAO and WHO standards. The water of Wadis of Biskra are characterized by slightly alkaline water pH (7–7.79), electrical conductivity >1,500 μS/cm, turbidity >5 FTU, very low level of suspended solid materials (1–1.33 mg/L), dissolved oxygen 2 mg/L, BOD5 > 5 mg/L, COD >30 mg/L, nitrite >0.1 mg/L, and NH3–N > 0.5 mg/L. Our findings emphasized the high contamination load of bacterial groups studied that exceeded WHO standards: total coliforms (56,917–76,167 CFU/100 mL), faecal coliforms (457–6,100 CFU/100 mL), faecal streptococci (1,432–5,217 CFU/100 mL), and sulfite-reducing Clostridia (886–5,217 CFU/100 mL). These results revealed a significant faecal pollution in the water of study Wadis. The spatiotemporal trend of different physicochemical and bacterial parameters, as well as the relationships between bacteria densities and physicochemical parameters were tested and discussed. The discharge of untreated wastewater into natural Wadis of drylands results in high and potential pollution risk with serious health and environmental issues. Therefore, the appropriate water treatment prior to wastewater discharge is needed urgently to prevent aquatic ecosystem pollution and degradation.