Home > Greywater use in the backyard: what are the health risks?

Greywater use in the backyard: what are the health risks?

December 1, 2010

Greywater can be collected from a variety of sources in the home, but how safe is it?

(Project 3006) Project Leader – Martha Sinclair, Monash University

Water restrictions have resulted in increasing use of alternative water sources for watering domestic gardens. Greywater (collected from the shower/bath, laundry and kitchen) is commonly used but no information is available on the frequency of use for irrigation of lawns or ornamental plants as compared to vegetables or fruit. Greywater sometimes contains significant levels of faecal contamination and therefore poses a risk of exposure to faecal pathogens for household occupants.

This project will survey greywater use in 600 Melbourne households to characterise the prevalence, frequency and purposes of use. The survey will be conducted in three ways; by mail, by telephone interview, and via a website. Households responding to the survey will be asked to take part in the second stage of the project where water quality data (E. coli and coliform levels in different grey water sources) and health diary data (occurrence of gastroenteritis symptoms) will be collected from a subset of 100 households. Limited testing for the two most common pathogens responsible for community gastroenteritis (Norovirus and pathogenic E.coli) will be conducted on greywater samples from a subset of 25 households.

The survey will provide information about the way in which greywater is used and allow a comparison of household practices with guidance provided by the Department of Health and EPA Victoria (both of which advise against use on vegetables to be eaten without cooking). In addition, associations between levels of faecal contamination, household demographics and greywater sources will be examined. Finally, in collaboration with researchers from the University of Melbourne, Quantitative Microbial Risk Assessment will be used to model the disease burden associated with current greywater use practices. The project is funded by the Smart Water Fund Victoria and WQRA.