title: Long-term impacts of pasture irrigation with treated sewage effluent on shallow groundwater quality.
abstract: The study investigated the effects of 26 years of effluent irrigation on chemical and bacteriological quality of shallow (<3.0 m) 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. 0.53 dS 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), NH(4)-N (2.6 vs. 0.5), NO(3)-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 288 cfu/100 ml, 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.
authors.affiliation: Soil Science & Plant Nutrition, School of Earth & Geographical Sciences, University of Western Australia, Crawley, Perth, WA, Australia. wgwenzi@yahoo.co.uk
authors.forename: W
authors.initials: W
authors.lastname: Gwenzi
authors.forename: R
authors.initials: R
authors.lastname: Munondo
mesh_terms: D000383:Agriculture / Q000379:methods*; D015169:Colony Count, Microbial; D004755:Enterobacteriaceae / Q000166:cytology; D005243:Feces / Q000382:microbiology; D005618:Fresh Water; D006863:Hydrogen-Ion Concentration; D019216:Metals, Heavy / Q000302:isolation & purification; D009566:Nitrates / Q000032:analysis; D009584:Nitrogen / Q000032:analysis; D010710:Phosphates / Q000032:analysis; D000644:Quaternary Ammonium Compounds / Q000032:analysis; D012722:Sewage / Q000737:chemistry*; D012987:Soil; D012995:Solubility; D013997:Time Factors; D014131:Trace Elements; D014865:Waste Disposal, Fluid; D018508:Water Purification; D014881:Water Supply / Q000592:standards*
chemical_list: D019216:Metals, Heavy; D009566:Nitrates; D010710:Phosphates; D000644:Quaternary Ammonium Compounds; D012722:Sewage; D012987:Soil; D014131:Trace Elements; D009584:Nitrogen