Rapid health-risk assessment of effluent irrigation on an Australian university campus

Rapid health-risk assessment of chlorinated sewage-effluent irrigation of lawns, fields and crops adjacent to populated areas at the University of Western Sydney was carried out in response to warnings from the supplying authority of deteriorating bacteriological quality of the water. Irrigation with low-quality effluent offered potential for the contamination of a range of foodstuffs and the exposure of staff, students and visitors. The need for early investigation was emphasised by eutrophication presenting as sudden algal bloom in one of the campus dams and an odour suggestive of anaerobic proteolysis on irrigation. No baseline data existed regarding improvement or deterioration in water quality with passage through the dams, or relating to potential for direct or indirect exposure. The assessment design incorporated three methodologies to generate biophysical, environmental and social data. Environmental and social data were used to augment short-term data for biophysical indicators in the estimation of risk. Where required qualitative information was converted to quantitative data using categorical ranking tables, and risk evaluation was carried out using ranked risk and uncertainty values. Results for biophysical indicators showed a steady improvement in water quality with passage through campus dams, emphasising a need to regard the impoundments as part of a treatment chain, rather than as passive storage units. Effluent quality at most irrigation sites marginally exceeded regional action thresholds for relevant crop types, suggesting a need for risk management through revised irrigation practice, system design, distribution management and risk communication. Problems requiring urgent intervention included the concentration of contaminants of bovine faecal origin in one dam as the result of a closed loop within the reticulation. Also of concern was the exposure of certain most susceptible individuals including crèche children who visited pastureland and orchards where irrigated oranges were collected, and potentially immunocompromised or mentally challenged adults in a work-opportunity gardening scheme. Despite its limitations, rapid risk assessment enabled identification and proactive management of major risk factors, promoted risk communication and awareness, and laid the foundation for ongoing risk surveillance.