Greywater reuse: An assessment of the scheme water savings that can be achieved at a household scale

Ceri Evans

In Perth, domestic irrigation constitutes over 50% of the total urban scheme water demand and at a time when urban water resources are diminishing, greywater reuse has the potential to enable significant reductions in scheme water consumption to be achieved. Greywater technology has been slow on the uptake in Western Australia as there has been greater focus from State government and Water Corporation on large scale water supply augmentation, such as seawater desalination. Some debate exists as to how useful greywater reuse can be in contributing to scheme water savings as limited studies have been carried out which collect real data. Monitoring was carried out at 9 case studies in the Perth Metropolitan area between 1st October 2008 and 31st March 2009. Water meters and data loggers were installed to monitor scheme water input, rainwater input (if applicable), greywater output, and exterior tap consumption. The objective of the study was to determine the scheme water savings that could be achieved through greywater reuse and to investigate factors that influence the level of savings. The factors investigated were: the volume of greywater generated, greywater technology and system, and irrigation as the end use application. Scheme water savings ranged from 9% - 37% across the case studies. Each of the factors investigated influenced the level of savings achieved, however those of most significant impact were: 1) an irrigation and landscape design that was in balance with the volume of greywater generated; 2) correct system maintenance; and 3) connection of both bathroom and laundry fixtures to the greywater system. Greywater reuse provides an opportunity for domestic scheme water consumption to be reduced, however for this opportunity to be fully realized, further guidance is required to enable homeowners to design an effective system. For greywater reuse to become an effective water conservation tool, modifications to the Code of Practice for Reuse of Greywater in WA, are required, to extend beyond safe disposal of greywater. Recommendations include incorporation of a site specific analysis to enable irrigation demand through calculation of plant water requirements to be balanced with estimated greywater volumes. This would increase the beneficial use of greywater and enable maximum scheme water savings to be achieved.

Greywater reuse: An assessment of the scheme water savings that can be achieved at a household scale

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