In an increasingly water-stressed world, graywater systems, which reuse high-quality water normally disposed of after a single use, can help to reduce the demand for new water supply and reduce the energy and carbon footprint of water services according to a new report from the
Pacific Institute .The
Overview of Greywater Reuse: the Potential of Greywater Systems to Aid Sustainable Water Management details the opportunities and challenges of reusing greywater and discusses what is needed to scale up emerging international efforts to reuse graywater.
Graywater is the relatively high-quality wastewater generated from household uses like bathing and washing clothes. As pressures on freshwater resources grow and new supply sources are increasingly scarce, expensive, or controversial, reducing demand by increasing water-use efficiency is key. Graywater reuse is one such strategy.
“Graywater reuse is part of an important paradigm shift in how we manage water, toward a more rational approach where we match the quality of water to the need” says Meena Palaniappan, director of the Pacific Institute International Water and Communities Initiative and coauthor of the report. “By reusing graywater in the home for watering landscapes or flushing toilets, we can reduce the use of high quality, expensive, and energy-intensive drinking water for those purposes.”
The new report examines the state of graywater implementation and policy, along with challenges that must be addressed for graywater reuse to be accepted and implemented effectively at larger scales.
In the United States, Arizona has one of the most supportive graywater policies, and in a survey of the city of Tucson, 13% of respondents indicated that they reused graywater in 1999, leading to new permitting policy in 2001. Graywater use is growing even in regions with laws restricting its use and those with no explicit policies regarding graywater; therefore it makes sense to consider how to create policies that encourage responsible graywater reuse.
“The percentage of household water that is graywater varies regionally and between households, but it is generally between 50% and 80%,” says Juliet Christian-Smith, senior research associate at the Pacific Institute and coauthor of the report, who will be presenting the research at the Graywater Alliance Roundtable. “That adds up to a significant amount of water. Graywater systems have tremendous potential to reduce water demand by replacing the use of potable water in non-potable applications.”
Graywater systems range from simple low-cost devices that divert graywater to direct reuse, such as in toilets or outdoor landscaping, to complex treatment processes incorporating sedimentation tanks, bioreactors, filters, pumps, and disinfection. The research shows that when the systems are designed and implemented properly, possible public health concerns with using different water qualities can be addressed. As greywater reuse becomes more widely adopted, regulations can be put in place to ensure that water quality is appropriately matched to water need.
Current water reuse policies in many countries are very restrictive of responsible on-site greywater reuse, and public perception of greywater as unsafe for reuse, or uncertainty around how to safely reuse greywater, is a major challenge for its increased use. The Greywater Reuse report outlines the steps needed for implementation of wider use of greywater internationally.
For more information, visit the
Greywater Alliance