A comparative study of the phosphate levels in some surface and ground water bodiesof Swaziland

Abstract

The levels of total phosphate in selected surface water and groundwater bodies from Manzini and Lubombo regions of Swaziland were determined using UV spectroscopic method. Samples were collected from three rivers (upstream and downstream of each), three industrial effluents, one reservoir, one pond, one tap water and fifteen boreholes. Mean phosphate levels in the tap water and reservoir varied between 0.08-0.09 mg/L while for the river samples, the range was 0.11-0.37 and for the industrial discharge, it was 0.11-1.60 mg/L PO₄–P. For the ground water systems it ranged between 0.10-0.49 mg/L PO₄–P. The mean phosphate levels in all the analyzed surface and groundwater samples were below the recommended maximum contaminant level (MCL) by SWSC (Swaziland Water Service Corporation) – i.e. 1.0 mg/L for drinking water; 2.0 mg/L for rivers and industrial effluents, and the South African criterion of 1.0 mg/L PO₄–P, for sewage effluents being discharged into receiving waters. However, pooled mean values for all the sites were higher than the USEPA criterion of 0.03 mg/L maximum for uncontaminated lakes. Dominant factors considered to have influenced the levels of phosphates in both the surface and groundwater samples analyzed include industrial activities (where present), agricultural activities (including livestock), population density, location (urban, suburban or rural), soil/rock type in the vicinity of the sampling point, climate and rainfall pattern of the area or region concerned.

KEY WORDS:  Surface water, Groundwater, Limiting nutrient, Eutrophication, Algal bloom, Anthropogenic phosphate sources

Bull. Chem. Soc. Ethiop. 2008, 22(2), 197-206.