Physicochemical Quality and Trace Metal Levels of Municipal Water from Three Reservoirs in Osun State,Nigeria

Abstract

The physicochemical quality of municipal water from three waterworks in Osun State, Nigeria was monitored in terms of temperature, pH, electrical conductivity, dissolved oxygen, solids (total, suspended and dissolved), nitrates and phosphates from April, 2003 to March, 2004 in order to assess the adequacy of treatment at the waterworks. The trace metal levels as well as the microbial quality of the municipal water from these waterworks were also monitored for the same length of time to establish their pollution levels.

The temperature values varied between 24.6°C and 32.0°C. The annual mean pH values for the three municipal water varied between 6.92 and 7.54 and therefore conforms with the WHO guideline of <8.0 in drinking water. The electrical conductivity values obtained ranged from 120.05 μS/cm to 265.00 μS/cm.

The mean levels of oxygen-demanding substances, nitrate, phosphate, total solids and dissolved solids were generally low and ranged from 6.23 mg/l to 8.99 mg/l; Not Detected (ND) to 2.59 mg/l; ND to 3.56 mg/l; 77.33 mg/l to 180.00 mg/l and 58.27 mg/l to 116.67 mg/l respectively. The concentrations of these substances were within safe limits. The coliform population varied from zero to 93 coliforms per 100 ml, the total bacteria count ranged between 0.3 × 10 $^4$ Cfu/ml and 45.50 × 10 $^8$ Cfu/ml while Escherichia coli was rarely detected throughout the study. Among the nine trace metals of interest only Hg, As and Cd occurred at concentrations above the WHO limits for drinking water and this give cause for concern