How efficient is on-site water reuse as a water management option

Sustainable management of freshwater resources has become a focus of the planning process to ensure future development in many urban areas is possible in New Zealand. Where water resources are in, or predicted to be in short supply, a holistic approach towards water management is required to provide efficient water management, rather than tackling water use and management options in a fragmented way. Several councils in New Zealand are already choosing water recycling and reuse in urban areas above water conservation measures with inadequate assessment of whether this is the most efficient water management option. This study compares the annual net present value (NPV) over a 20-year period for three water reuse systems which require different levels of treatment and therefore have different costs. It determines the level of water usage which would be needed to achieve a payback period in five years for the lowest cost treatment system and concludes that water conservation is important to effect a change in behaviour is required to effectively manage water.