Australia faces a significant water management challenge from prolonged drought, record breaking low rainfall and streamflows, continuing economic and population growth, and changing water quality characteristics. The future predictions for climate change and population growth in the Melbourne metropolitan area project an increasing demand for water, not only for drinking and domestic urban uses, but also for industrial and irrigation applications.

The focus of this investigation was to replace drinking water with fit-for-purpose recycled water and stormwater for industrial users.

A decision making framework was developed to give a holistic and sustainable approach to finding the most appropriate alternative water supply option. An integrated planning approach that utilised tools for multiple criteria analysis (MCA), rapid design and cost estimation, cost benefit analysis (CBA) and decision making science. A wide range of options for servicing, treatment and water sources were identified and compared using the integrated planning approach. The decision making framework considered non-monetary criteria such as water quantity and quality, technical feasibility, constructability, operability, greenhouse gas footprint, energy use, public acceptance and safety, chemical use and residuals generation. Monetary criteria such as capital, operational costs and net present value were also considered using a cost benefit analysis to provide a balanced and unbiased view during the decision making process.

Alternative water supply options were developed using a full range of water sources and treatment alternatives. The options for alternative water supply were also developed by considering a range of delivery or servicing methods ranging from centralised systems to individual localised treatment systems.

The centralised options were superior in terms of ease of operation, consistency of supply and cost, while the importation of recycled water from a neighbouring treatment plant or from sewer mining were found to be more secure water sources that could yield more consistent product water quality.