Risk-based planning for water recycling in an Australian context

Australia has seen an unprecedented proliferation in large scale water recycling schemes since the late 1990s. This has been driven by a recent decade of drought, policies to encourage water efficiency in new homes and buildings in urban areas, and to reduce pressure on rain-fed water supplies by replacement with alternate water sources in rural areas. Underpinning these drivers are principles of economic and environmental sustainability and protection of public health. National guidelines for recycling of treated sewage, released in 2006, replaced an approach using prescriptive end point water quality targets, with a 12-step risk-based framework for the planning and operation of Australian water recycling schemes. Essential to this risk-based approach is an understanding of the sewage treatment system and assessing the risks in the catchment, the treatment process, distribution system and end use environment. Inherent also in this process is the identification of critical control points with tangible operational targets for pre-empting, preventing and correcting off-spec conditions before they derail a scheme. Validation of systems through microbial log reduction targets for indicator viruses, bacteria, protozoa and helminths, differentiated according to end use and expected exposures, may be obtained through treatment, site controls or a combination of both. Drawing on case studies from the Australian states of New South Wales (NSW) and Queensland (Qld), this paper gives insight to preventative risk management of water recycling schemes with typical risk profiles. Some advantages and disadvantages of the guideline approach are considered. The information paints a picture of the industry's risk management obligations in the planning phase and may be of use to practitioners in other regions where planning for safe and sustainable water recycling is developing.