Physicochemical properties of wastewater in three typical South African sewage works

Abstract

The physicochemical qualities of the effluent samples of three municipal sewage treatment plants in the Eastern Cape of South Africa were evaluated from September 2015 to February 2016 using standard methods. The physicochemical parameters assessed include pH, temperature, total dissolved solid (TDS), turbidity, chemical oxygen demand (COD), alkalinity, dissolved oxygen (DO), free chlorine, chloride, sulphate, phosphate, ammonium, and electrical conductivity (EC). The results of the evaluation were as follows: temperature (19-36ºC), EC (60-1,095 mS/m), alkalinity (2.6-20.9 mg/L), nitrate (0.24-26.5 mg/L), nitrite (0.01-90 mg/L), phosphate (0.02-5.12 mg/L), ammonium (0.06-112 mg/L), sulphate (3-72 mg/L), chloride (3.25-224 mg/L), COD (17-394 mg/L), and turbidity (1.96-715 NTU). Free chlorine concentrations and DO were within the recommended limits for most of the sampling period and ranged between 0.17-0.48 mg/L and 0.19-21.9 mg/L, respectively. Also, the pH, phosphate, sulphate, and free chlorine concentrations were within acceptable limits, while EC, temperature, TDS, turbidity, COD, chloride, ammonium, nitrate, and nitrite did not conform to recommended limits. We conclude that these municipal sewage plants are sources of pollution to their respective receiving watersheds and threats to public and environmental health.