Greywater has the potential to be a significant water resource for household gardens across Victoria. The Millennium Drought increased the utilisation of greywater at the household level. By 2007, 55% of Australian households used greywater to some extent, with 43% of Victorian households utilising greywater as the main source of water for the garden (ABS 2007).
However greywater quality is highly variable. Many household cleaning products, detergents and personal care products have high concentrations of chemicals that may be detrimental to plant and soil health. In addition, current greywater use largely involves temporary use of hoses and buckets which result in suboptimal collection and distribution of greywater and potential manual handling risks. If household greywater use is to develop beyond a temporary drought relief measure, householders require information on whether permanent greywater diversion and treatment systems are a viable solution.
To enable this, relevant, household-specific information on greywater quality management is required. This information needs to incorporate the number of people in a household, garden type and area, and the cleaning and personal care products used around the home have on greywater quality and, therefore, on the suitability of permanent greywater systems for specific households.
Smart Water Fund responded to this knowledge gap by investing in the “GreySmart” research, project and producing information to guide household decision-making in a consolidated and user friendly manner. This information will continue to be of benefit beyond the Millennium Drought. Water efficiency will remain a focus for households and the water industry going forward, and any return to drier conditions will likely see a spike in the usage of household greywater.
The GreySmart project consisted of two components.
Initially, the project developed a comprehensive assessment of the hazards in commercial household cleaning and personal care products, and detailed their associated environmental risks. This included a review of greywater literature to identify the potential hazards and mitigation strategies for these. Once known, an assessment tool – the GreySmart rating system – was developed to scientifically assess whether particular household products make greywater use unsuitable for use on gardens. The assessment tool was developed using the approach in the 2006 Australian Guidelines for Water Recycling. This tool led to production of a list of detergents, household cleaning and personal care products labelled as “GreySmart” or “GreySmart with Care” (i.e. garden friendly).
The second part of the project developed a web-based calculator to rate greywater, rainwater and potable water use to encourage the most beneficial water use options for each household. . Again, the calculator considered the number of water users, the garden design, and footprint of the household. A literature review of existing rainwater tank model methodologies was completed to validate the calculator’s model. Once developed, the model methodology was reviewed and refined by greywater experts. A website was built to house the new calculator, known as the ‘H20meCalc’, along with an education package and knowledge bank to encourage of good practice in sustainable greywater use.
The GreySmart project delivered the GreySmart rating system methodology for assessing household cleaning and personal care products. This tool was initially used to complete an environmental risk assessment of 143 different clothes washing detergents, using data publicly available from literature. The risk assessment determined if products could be considered “GreySmart” or if their used posed a risk to gardens irrigated with greywater. This risk assessment provides valuable information for households to use in making informed decisions on greywater use. Of the 143 detergents assessed from literature data, only 22 (15%) of these were determined as environmentally safe to irrigate gardens:
- 15 were considered very low risk and therefore achieved a GreySmart rating – Ideal for use if greywater will be used to irrigate the garden
- 7 products were considered low risk and achieved a GreySmart with care rating – Ok for use if greywater will be used to irrigate the garden but will probably need some management of the soil within a year or two (e.g. pH adjustment, nutrient management of addition of gypsum, lime or organic matter to manage soil structural changes).
Availability of the GreySmart rating methodology now means that new (or reformulated) cleaning and personal care products can be scientifically assessed for their greywater suitability as they enter the market.
The tool is used routinely in studies undertaken by CHOICE, in co-operation with City West Water, on high performance laundry detergents. The study compares detergents for wash performance, their impact on gardens when laundry greywater is used and the impact on recycling at wastewater treatment plants.
** When reviewing the outputs from this project, be aware that the website housing the ‘H20meCalc’ and the greywater knowledge bank has been taken down. The GreySmart rating system methodology for the environmental risk assessment tool, and the model methodology for the ‘H20meCalc’ calculator is still available via the links on this page. **