Recycling of greywater in households: a practice in need of regulation

With regard to sustainable development, the recycling of greywater in a household setting is often cited as a way to preserve water resources and reduce the consumption of drinking water. Over the last few years, interest in this practice has grown and certain countries such as Australia, the United States, Israel and Japan have begun looking to these additional solutions when faced with shortages of fresh water.

In 2011, ANSES was asked by the Directorate General for Health to assess the health risks of the recycling of greywater for household purposes, a practice which is currently prohibited in France. The opinion and report resulting from the expert appraisal were published today. They establish microbiological and physicochemical quality criteria for greywater treated for certain household uses and recommend the implementation of a number of preventive measures.

Health risks linked to the various uses of greywater: each project is unique

Raw greywater is water from showers, bathtubs, bathroom sinks, washing machines, kitchen sinks and dishwashers. The work conducted by ANSES's experts shows that the currently available data are insufficient to provide an in-depth and exhaustive characterisation of either the hazards of the various physicochemical and microbiological contaminants found in greywater, or of the levels of exposure corresponding to its various uses and applicable to all situations.

Greywater contains particulate and organic matter and is contaminated by microorganisms, including pathogens and physicochemical contaminants from hand washing, personal care products and cosmetics, household cleaning products, detergents and laundry care products. Due to its characteristics, raw greywater cannot be recycled for domestic purposes without first undergoing treatment. Therefore, the recycling of greywater requires treatment, transport and storage phases that need to be controlled.

In addition, the use of treated greywater in the home requires the installation of a system completely separate from the distribution system for water intended for human consumption (WIHC), and the feedback received has emphasised the fact that the existence of a non-potable water system inside dwellings is a major source of risk. In fact, the interconnection between the WIHC system and the system for greywater can cause contamination of the public WIHC distribution system, making it non-compliant with the regulations in force and likely to have an effect on the health of consumers.

ANSES's recommendations

ANSES considers that the practice of reusing greywater in dwellings must only be considered for strictly limited uses, in geographical environments durably and repeatedly subject to water shortages.

As long as appropriate treatment and management measures are implemented, treated greywater can be applied to three types of household uses, provided it fulfils specific quality criteria at its point of use:

• supplying water for flushing toilettes;
• watering green spaces (except for vegetable gardens and agricultural uses);
• washing surfaces out of doors without the generation of aerosols (excluding use in high-pressure cleaning equipment). However, for this type of use, the addition of cleaning products to the treated greywater should be avoided.

Under these conditions, a regulatory framework for the conditions of collecting, storing and treating raw greywater is necessary in order to reduce the health risks to exposed individuals.

Due to the lack of data needed to conduct an assessment of the health risks linked to the various uses of treated greywater, ANSES recommends that each project for reuse of raw greywater in a household setting be systematically subjected to a risk analysis in order to ensure that the benefits outweigh the risks to the health of the residents and workers who will be using the treated greywater in dwellings.

The Agency recommends that policymakers, individuals, co-owners, elected officials, etc. be informed of the possible health, environmental and economic impacts of greywater reuse operations. 

Furthermore, the addition of a greywater system to a building may also create health risks for users and/or residents which may be linked to the installation, operation or maintenance of the system, or to the quality of the water provided. Traceability is therefore essential to ensure health and safety over time and to avoid any possible problems.

Users of this type of system (building residents, workers, occasional users) must also be informed that a greywater recycling system is in operation on the premises and of the possible health risks involved. Users must also be trained in the conditions of use required to minimize the risks of a non-potable water system.

ANSES has also provided a list of practical recommendations for professionals working with greywater recycling systems.

In a sustainable development context which aims to preserve water resources and avoid water waste in general, the Agency wishes to emphasise the importance of responsible water use in all situations.

Other work by ANSES

ANSES has already issued a number of opinions on the recycling of treated wastewater.

It was also recently asked to assess the topic of rainwater recycling.