DomesticGreywater Reuse: Preliminary Evaluation

ReportNo WSAA 60

July 1993

SYNOPSIS

Residentialreuse of wastewater for non potable purposes has been in practice overseas formore than a century. The economics of supplementing water supply resources andreducing wastewater discharge have been the catalyst for many of theauthorities which approve the practice.

Thesegregation of domestic wastewater at the source into two separate flows gives“Blackwater” and “Greywater” (also referred to as sullage). Blackwater is watercloset, bidet and bidette waste and thus has gross faecal contamination.Greywater is all the remaining household waste water e.g. bath, laundry etc andby definition is not deemed to be faecally contaminated. Investigationsundertaken during this project indicate, however, that this is not a reliabledefinition as it greatly depends on practices within the home.

Theproject was conducted to provide an insight into the potential for on-sitedomestic use of greywater in Australia and included a comprehensive postalenquiry of foreign embassies and overseas environmental protection agencies,literature searches using the key word “greywater”, and enquiries to all themajor water authorities within Australia. Some users of septic tank pump-outsystems in the Brisbane Region were also surveyed. This report describesoverseas practices, water and cost saving benefits, scientific analysis ofhealth risks for Domestic Greywater Reuse and design criteria.

Residentialreuse of greywater is not presently permitted in Australia but neither is itprecluded because the terminology is not recognised. Potential risks to publichealth, the impact on the urban environment and the economics of greywaterreuse need to be investigated before such use can be permitted.

Thepreliminary studies undertaken in this project indicate that the volume ofgreywater produced in most households is sufficient to meet all toilet flushingrequirements and/or a significant portion of current outdoor usage on lawns andgardens and that, subject to the development and implementation of guidelinesto protect public health and the environment, there would be no appreciablerisks involved. Further studies are being undertaken to develop theseguidelines.

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