Water Journal : Water Journal July 2011
reuse and recycling refereed paper 92 JULY 2011 water technical features Abstract A review of current and proposed applications of indirect potable reuse (IPR) in Australia was undertaken. Particular attention was paid to the role of the environmental buffer and its contribution to the provision of safe drinking water. Identified limitations or shortcomings of these IPR schemes were then assessed in terms of whether a change to direct potable reuse (DPR) might facilitate necessary improvements to the overall management of recycled water. A number of key issues differentiating IPR and DPR were identified. Depending on precise scheme design factors, additional advantages of DPR may extend to reduced costs and energy consumption, improved water quality, more rigorous system validation and risk management, the availability of a protected emergency water supply, improved flood management and a more immediate solution to urban water shortages. Introduction During the decade 2000--2010, provision of urban drinking water supplies grew to become one of the key environmental, social and political issues in Australia. As traditional water sources began to reach sustainable limits, the use of alternative supplies, including planned indirect potable reuse (IPR), was initiated. It is apparent that a broad consensus has developed among the Australian water industry and its regulators regarding the ability to protect public health by a well planned, carefully designed and properly managed IPR scheme. However, this consensus has clearly not extended to the alternative practice of 'direct potable reuse' (DPR). In IPR schemes, reclaimed water is returned to an environmental 'buffer' such as a river, lake or aquifer, where it mixes with other environmental waters before being re-extracted for drinking water treatment and potable use. IPR differs from DPR where highly treated reclaimed water is introduced 'directly' into the drinking-water system (or to the inlet of a conventional drinking water treatment plant) without environmental retention. Current and Proposed Practices of Indirect Potable Water Reuse During the last two decades, there have been a number of planned IPR schemes proposed in Australia, which have not eventuated due to failure to win community support. However, by 2007 it had become clear that some of Australia's largest cities would need to adopt varying approaches to IPR in order to make full use of available water supplies. Major schemes have since been partially developed in Queensland and Western Australia. Nonetheless, their full implementation as IPR schemes is yet to be realised due to State Government- imposed management restrictions and/ or the need for improved characterisation and validation of the performance of the 'environmental buffer'. The Western Corridor Recycled Water Project (WCRWP) was developed during 2007--2010, partly as a means to supplement raw potable water supplies in Lake Wivenhoe, SE Queensland. This is the primary source of drinking water supply for Brisbane and much of the surrounding area. The WCRWP uses municipal effluent from six wastewater treatment plants, which is then subjected to advanced water treatment at three new advanced water treatment plants at Bundamba, Luggage Point and Gibson Island. Some of this advanced-treated water is now used for industrial purposes, but the IPR aspect has been postponed until storage supplies drop to below 40% of capacity. Water Corporation, which manages Perth's water resources, is currently undertaking a three-year project known as the Ground Water Replenishment Trial (GWRT). The GWRT involves the treatment of reclaimed municipal effluent by a new advanced water treatment plant located at Beenyup in the northern suburbs of Perth. This water is being used to recharge the Leederville Aquifer, which is an important drinking water aquifer in the north of Perth. If the trial is successful, up to 27GL per year of reclaimed water may be injected to the aquifer by 2015. However, depending on the final scheme design, none of this injected water is predicted to reach extraction wells until after 2020. Methodology An analysis of the case for DPR was undertaken by a detailed consideration of current practices and proposals for IPR in Australia. Case studies of existing and proposed IPR schemes were used to evaluate the implementation and operation of these schemes in terms of their compliance with current risk management requirements and their ability to supplement water supplies in a timely and cost-effective manner. Careful consideration was given to current Australian guidelines for water recycling and accepted practices for risk management within the Australian water sector. Identified limitations or shortcomings of current and proposed IPR schemes were then assessed in terms of whether a change to DPR may facilitate necessary improvements to the overall management of recycled water in Australia. Stuart J Khan THE CASE FOR DIRECT POTABLE WATER REUSE IN AUSTRALIA presented at The Western Corridor Recycled Water Project (WCRWP) under development. PHOTO: WESTERN CORRIDOR RECYCLED WATER PTY LTD.
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