Emongor, VE; Khonga, EB; Ramolemana, GM; Marumo, K; Machacha, S; Motsamai, T
The objective of this study was to evaluate the suitability of treated secondary sewage effluent for irrigation of horticultural crops in Botswana. Secondary effluent water was sampled every month for one year, from a breather pipe on the pivot irrigation system at the Botswana College of Agriculture, Notwane Farm, Gaborone, Botswana, using USEPA procedures and guidelines. The results of the study showed that the secondary sewage effluent from the activated sewage treatment plant in Gaborone had the following physico-chemical properties: Electrical Conductivity (EC) of 0.51 dS m-1, pH 9.08, total dissolved solids of 358 mg L-1, total alkalinity of 234 mg L-1 as CaCO3, Cl- 70 mg L-1, NaCl 115 mg L-1, Sodium Adsorption Ratio (SAR) of 2.26, NO3- 5.56 mg L-1, NH4+ 0.3 mg L-1, NO2- 0.0184 mg L-1, total Fe 0.623 mg L-1 and faecal coliforms of 5/100 mL. The current results suggest that the Gaborone secondary sewage effluent is suitable for unrestricted irrigation of horticultural crops based on the EC, SAR, Cl-, NaCl, faecal coliforms, available plant nutrients and the low concentration of heavy metals (Pb, Cr, Cu, Co, Cd, As and Se all present in parts per billion).
activated sludge; ammonium; arsenic; cadmium; chloride; chromium; cobalt; copper; crop production; electrical conductivity; faecal coliforms; heavy metals; horticultural crops; iron; irrigation; irrigation systems; lead; nitrate; nitrogen dioxide; pH; selenium; sewage effluent; Botswana; Southern Africa; Africa South of Sahara; Africa; Least Developed Countries; Developing Countries; ACP Countries; Commonwealth of Nations; SADC Countries; Anglophone Africa; fecal coliforms; hydrogen ion concentration; potential of hydrogen; sewage treatment plants; watering; Horticultural Crops (FF003) (New March 2000); Plant Production (FF100); Soil Water Management (Irrigation and Drainage) (JJ800) (Revised June 2002) [formerly Soil Water Management]; Human Wastes and Refuse (XX300)