The major cations and trace elements in Notwane river, Botswana and its suitability for irrigation

Abstract

Notwane river in Botswana, is a perennial river in which the treated secondary or tertiary sewage effluent from Gaborone activated sludge treatment plant is discharged to. The objective of this study was to evaluate the major cations and trace elements in the water of Notwane river for irrigation purposes. Six sites were used for the study. The results of the study showed that the major cations and heavy metal concentration differed significantly (P< 0.0001) among the sampling sites, but the concentrations of the heavy metals were far below the recommended limits for effluent discharge guidelines to perennial or ephemeral rivers and irrigation water quality. The concentration of Ti, V. Cr, Mn. Fe, Co, Cu, Zn, As, Se, Sr and Pb ranged between 95-131.54, 41.03-89.50. 4.47-10.0. 7.26-42.04, 390-1000.10, 2.0- 2.87, 2.46-5.26. 11.96-16.24, 5.14-6.44, 3.01-5.48, 76.51-78.61 and 3.38-8.56 ug L1. respectively. The SAR values of the Notwane river water ranged between 3.57 to 3.64, which is within the maximum recommended (<9) for irrigation water by FAO. Based on major cation content, SAR and heavy metal concentration in the water of Notwane river along the sampled sites, the water is suitable for irrigation of field, fodder, horticultural crops and drinking water for livestock.