Soil Science and Plant Nutrition, School of Earth and Geographical Sciences, University of Western Australia, 35 Stirling Highway, Crawley 6009, Perth, WA, Australia; Department of Biological Sciences, Tropical Resources Ecology Program, University of Zimbabwe, P. O Box MP167, Mt Pleasant Harare, Zimbabwe; Department of Civil Engineering, University of Zimbabwe, Po Box MP167, Mt Pleasant, Harare, Zimbabwe
Gwenzi, W., Soil Science and Plant Nutrition, School of Earth and Geographical Sciences, University of Western Australia, 35 Stirling Highway, Crawley 6009, Perth, WA, Australia, Department of Civil Engineering, University of Zimbabwe, Po Box MP167, Mt Pleasant, Harare, Zimbabwe; Munondo, R., Department of Biological Sciences, Tropical Resources Ecology Program, University of Zimbabwe, P. O Box MP167, Mt Pleasant Harare, Zimbabwe
The study investigated the effects of 26 years of effluent irrigation on chemical and bacteriological quality of shallow (<3.0m) groundwater. Annual loading rates for N and P exceeded pasture requirements, while trace metals were either lower or higher than guideline limits. Effluent irrigation removed TN (44-71%), TP (80%), Cr (96%) and coliform bacteria (87-99.9%) while Zn, Cu and Cd removal was negligible probably due to their enhanced mobility. Analysis of groundwater samples from effluent-irrigated and non-irrigated control sites showed that effluent irrigation increased the levels of all measured parameters compared to the control. Average groundwater quality parameters from effluent-irrigated sites compared to the control were: pH (6.1 vs. 5.7), EC (0.71 vs. 0.53d m-1), concentrations (mg L-1) for TP (2.3 vs. 0.3), DP (1.0 VS. 0.1), TN (15.1 VS. 2.5), NH4-N (2.6 VS. 0.5), No3-N (4.1 VS. 1.3), Zn (0.4 VS. 0.05), Cu (0.13 vs. 0.02), Cd (0.05 vs. 0.01) and Cr (0.06 vs. 0.03). Across effluent-irrigated sites, FC and TC were 25 and 288cfu/100ml, respectively, versus nil for the control. Overall, effluent irrigation led to groundwater contamination by N, P, trace metals and coliform bacteria, which could threaten the long-term sustainability of the practice. ©IWA Publishing 2008.
Bacteriological quality; Control sites; Effluent irrigation; Enhanced mobility; Groundwater contamination; Groundwater quality; Guideline limits; Loading rate; Loading rates; Long-term sustainability; Measured parameters; Sewage effluents; Shallow groundwater; Trace metal; Bacteriology; Chromium; Coliform bacteria; Effluents; Groundwater; Groundwater pollution; Hydrogeology; Irrigation; Metal recovery; Sewage; Trace analysis; Trace elements; Wastewater; Wastewater treatment; Water quality; Zinc; Quality control; coliform bacterium; groundwater pollution; irrigation; irrigation system; pasture; sewage; sustainability; trace metal; waste treatment; water quality; Agriculture; Colony Count, Microbial; Enterobacteriaceae; Feces; Fresh Water; Hydrogen-Ion Concentration; Metals, Heavy; Nitrates; Nitrogen; Phosphates; Quaternary Ammonium Compounds; Sewage; Soil; Solubility; Time Factors; Trace Elements; Waste Disposal, Fluid; Water Purification; Water Supply