Graywater Good For Landscape

New research funded by the Water Environment Research Foundation (WERF) and the American Cleaning Institute (ACI) finds that many landscape plants thrive from long-term graywater irrigation and may also receive additional nutritional benefits. Graywater (wastewater from bathing and laundry) makes up nearly 50 percent of a typical household's wastewater, and could supply 100 percent of the residential irrigation need in some parts of the country.

Landscape Contractors
With ever-increasing irrigation limitations, contractors could pitch installing graywater irrigation systems as a way keep landscapes green and healthy even under severe drought and watering restriction.

The study examined household graywater irrigation systems, and found soil irrigated with it showed increased levels of surfactants (surface active agents), antimicrobials and sodium compared to those irrigated with freshwater, but that only three salt-sensitive tree species (avocado, lemon and scotch pine) out of 22 plant species investigated showed negative reactions to long-term graywater irrigation. In addition, the nitrogen present in graywater had plant-growth benefits. It is possible that fertilizer addition can be reduced or eliminated where graywater irrigation is used.

The report “Long-term Study on Landscape Irrigation Using Household Graywater-Experimental Study (06-CTS-1CO)” is available for download at www.werf.org and on ACI’s Science website at www.ACIscience.org.