Academic journal article Journal of Environmental Health

Graywater Use Still a Gray Area. (Guest Commentary)

Academic journal article Journal of Environmental Health

Graywater Use Still a Gray Area. (Guest Commentary)

Article excerpt

As clean water resources become scarcer, a concept of separating graywater from a home's waste stream and using it to supplement the family's water supply grows increasingly popular. Graywater is generally defined as all wastewater generated from household activity except that produced from the toilet.

Reuse is an integral part of ecosystem management. Reuse and recycling efforts are looked upon with favor these days, and the concept of reusing graywater seems to hold much potential. The possibility of disease transmission, however, makes the actual process of permitting safe, low-maintenance systems quite complex.

In arid parts of the United States, the practice of using graywater for irrigation has a long history. Certainly, the chores of more than a few pioneer women included marching into the yard to dump dishpans of water on some struggling little rosebush. This was graywater use at its most basic. While graywater use is common in rural areas and has been practiced by many people in urban areas for years, it is technically illegal in many places in the United States.

While the idea seems simple, the careless use of many gallons of untreated graywater could result in disaster. Before society rallies around the idea that graywater recycling can solve all of our water shortage problems, it would be wise to investigate potential hazards associated with the practice, as well as review some of the current permitted applications.

A significant portion of the nation's wastewater results from domestic activities; if deemed safe and practical, recycling graywater could be an integral part of a household's water conservation effort. The average amount of graywater produced is 40 gallons per day per person--an estimated 60 to 65 percent of a household's total water demand (Bilson, 1998). If this amount of wastewater could be treated and applied to outdoor use, that would create a meaningful reduction in demand. Reduction of water demand through conservation is probably the cheapest and most environmentally sound and effective way of extending water supplies.

Technology for reuse can range from simple methods, like saving the rinse water from the clothes washer for immediate use as wash water in the next load, to rather complex treatment systems. Some methods use multiple cells containing water plants and sand filtration systems--and those systems can be simple and low-cost or highly complex and expensive.

Most of the permitted systems send the effluent, after minimal treatment, to underground irrigation piping or leachfields designed to prevent runoff or ponding. Presumably, graywater is naturally purified by biological activity in the topsoil. Soil microorganisms break down the organic contaminants, and the treated water percolates to recharge the underlying groundwater.

There also are commercially packaged plants that produce a filtered, disinfected product suitable for many uses (but not drinking). Unfortunately, most of these recycling systems are fairly expensive to purchase and operate (requiring electric motor-driven pumps). They should be installed by professional, licensed plumbing contractors and only with the approval of local health departments.

In all instances, blackwater (wastewater generated by the toilet) must be disposed of through a separate treatment system, and the graywater system must be plumbed so it can be diverted to the sewer system when necessary.

What Is in Graywater?

As defined by the California Graywater Standards (California Administrative Code, n.d.), graywater is untreated household wastewater that has not come into contact with toilet waste. Specifically, graywater includes water from bathtubs, showers, bathroom wash basins, and water from clothes washing machines and laundry tubs. Wastewater from kitchen sinks, dishwashers, or laundering of soiled diapers typically is heavily contaminated. …

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