technical features
recycled water
RISK MANAGEMENT: BOVINE JOHNE'S DISEASE AND WATER RECYCLING T Anderson Summary
The catchment of South East Water's Pakenham sewage treatment plane includes a car tie sale yard and an abattoir. T reared effluent from rhe plane is used to irrigate pasrure grazed by dairy cattle. There is a consequent possibility char cattle diseases can be transmitted to the grazing animals. Advice from the Victorian Insrirute of Animal Science indicated that the cattle co ndition of most concern was Bovine Johne's Disease (BJD). T his disease is common in dairy herds in a num ber of scares withi n Australia and management practices are well developed and widespread in the dairy industry. The disease reduces milk production in mature animals and affects the value of both the carcass and infected land . South East Water has undertaken a number of actions to quantify and manage the incremenral risk of BJ D occurring at Pakenham as a result of water recycling. These actions include obta ining opi nion from persons expert in BJD, sponsoring research projects, obtaining advice on the possible link with Crohn's d isease in hu mans and legal advice. The outcome is char there is no evidence of a material ri sk to either humans or mature cattle although the risk co susceptible animals such as calves cannot be d iscounted. As a consequence, measures designed co eliminate exposure of calves to recycled water have been incl uded in agreements with recycled water cuscomers. Introduction
South East Water is a government-owned retail water company formed in 1995 with about 1.3 m illion cuscomers in the south eastern suburbs and outlying areas around Melbourne. The Company purchases potable water from Melbourne Water Co rporation, delivers it to customers and collects the consequent sewage and trade waste. There are two other similar retail water companies in Melbourne - Yarra Valley Water and City West Water.
Quantifying and managing the risk of disease transmission.
Cattle on pasture irrigated with treated sewage at Pakenham.
In South East Water's case, about 90% of the sewage and trade waste is retu rned to Melbourne Water for treatment at one of the two major facilities serving the central metropolitan region. The remain ing 10% of waste arises in townships remote from rhe central system and is treated in small facilities owned by South East Water and with capacities in the range 0.5 co 15 ML/day. When these plants were firs t established, the effl uenr discharged co local water courses which drained inco either Port Phillip Bay or Western Pore. Th is approach became inco nsistent with government policy expressed in Stare Environment Protection Policies first published by the Viccorian EPA during the 1980s. These policies consistently favour recycling of effluent from sewage treatment plants co land wherever "practicable". In response to this policy position, South East Water has sought to eliminate discharge co inland water courses at each of its treatment planes. Effluent recycling represented a predomi nantly new activity for the Melbou rne water industry at rhe time when South East Water was formed as a separate
organisation in 1995. As a consequence, South East Water sought co identify risks associated with ch is new activity and develop appropriate management systems. The purpose of rhis present paper is to describe South East Water's general approach to risk management and rhe speci fie actions taken to manage the possibility chat effluent from the Pakenham sewage treatment plane could increase the incidence of disease in cattle. General Approach
South East Water's general approach to management of risk is based on the concept char compliance with regu lations is a necessary but not always sufficient bas is for / 1 managing risk. For example, regulations and guidelines may not be adequate to manage either well recognised risks or specific issues arising from unique or unusual circumstances. In such circumstances, the obligation under Civil Law to exercise due care requires that all reasonable efforts are made to identify, evaluate and mitigate the risk. Because of chis general approach to management of risk, South East Water
Journal of the Australian Water Association
Water
AUGUST 2007 71