Physico-chemical and bacteriological quality assessment of surface water at Lake Tonga in Algeria

Abstract

Maintaining standard water quality of aquatic ecosystems requires continuous monitoring of water physicochemical and bacteriological characteristics. This study aimed at assessing water physicochemical and microbiological proprieties of Lake Tonga (northeastern Algeria). Water samples were collected monthly (January–June) from three different stations at different depths. Several physicochemical parameters (pH, electrical conductivity, turbidity, hardness, biological oxygen demand (BOD5), concentrations of suspended solid materials, dry residuals, dissolved oxygen, phosphate, nitrites, nitrates, ammonium, calcium, magnesium, chloride, potassium and sulfur dioxide) and bacterial group sdensity (total heterotrophic bacteria, total coliforms, faecal coliforms and faecal Streptococci) were measured. Physicochemical analysis of Tonga Lake water revealed a slightly alkaline environment pH (6.5 < pH < 8.5), electrical conductivity < 1500 μS/cm, turbidity > 7.02 NTU, dry residues < 2000 mg/L, suspended solid materials (11.8 mg/L, < 30 mg/L), dissolved oxygen < 5 mg/L, phosphates > 5 mg/L, BOD5 < 5 mg/L, nitrate < 50 mg/L, nitrite > 0.1 mg/L, and NH4+ > 0.5 mg/L, Ca2+ < 200 mg/L, Mg2+ < 150 mg/L, Cl–> 500 mg/L, K+ > 20 mg/L and sulfates < 200 mg/L. In addition, microbiological results indicated the presence of different groups of faecal bacteria with an average of 32.3 × 10³ CFU/100 mL for total heterotrophic bacteria, 24 × 10³ CFU/100 mL for total and faecal coliforms, and 37 × 10³ CFU/100 mL for faecal Streptococci. Tonga Lake is currently in an eutrophication state and further severe ecosystem degradations may occur if the appropriate management measures are not taken in short term.