US top-loading washing machine 30 gallons
European front loading .10 gallons washing machine
Dishwasher 3-5 gallons
Low flow shower head, per shower 3-7 gallons
Other sink use (shaving, washing, etc.) 1-5 gallons
Source: Lindstrom, Carl (1992). Graywater — Facts About Graywater — What it is, How to Treat it, When and Where to Use it. www.greywater.com
day, which is then drained into a septic or sewage system. This estimate does not include toilet water. Ironically, the graywater we dispose of can still be useful for such purposes as yard, garden and greenhouse irrigation. Instead, we dump the graywater into sewers and use drinking water to irrigate our lawns.
Reuse of graywater for landscape irrigation can greatly reduce the amount of drinkable water used for irrigation during the summer months when landscape water may constitute 5080% of the water used at a typical home. Even in an arid region, a three-person household can generate enough graywater to meet all of their irrigation needs.7 In arid Tucson, Arizona, for example, a typical family of three uses 123,400 gallons of municipal water per year.8 It is estimated that 31 gallons of graywater can be collected per person, per day, amounting to almost 34,000 gallons of graywater per year for the same family.9 An experimental home in Tucson, known as Casa del Aqua, reduced its municipal water use by 66% by recycling graywater and collecting rainwater. Graywater recycling there amounted to 28,200 gallons per year, and rainwater collection amounted to 7,400 gallons per year.10 In effect, recycled graywa-ter constitutes a "new" water supply by allowing water that was previously wasted to be used beneficially. Water reuse also reduces energy and fossil fuel consumption by requiring less water to be purified and pumped, thereby helping to reduce the production of global warming gases such as carbon dioxide.
Because graywater can be contaminated with fecal bacteria and chemicals, its reuse is prohibited or severely restricted in many states. Since government regulatory agencies often do not have complete information about graywater recycling, they may assume the worst-case scenario and simply ban its reuse. This is grossly unfair to those who are conscientious about what they put down their drains and who are determined to conserve and recycle water. Graywater experts contend that the health threat from graywater is insignificant. One states, "I know of no documented instance in which a person in the U.S. became ill from graywater." 11 Another adds, "Note that although graywater has been used in California for about 20 years without permits, there has not been one documented case of disease transmission." 12 The health risks from graywater reuse can be reduced first by keeping as much organic material and toxic chemicals out of your drains as possible, and second, by filtering the graywater into a constructed wetland, soilbed or below the surface of the ground so that the graywater does not come into direct human contact, or in contact with the edible portions of fruits and vegetables.
In November of 1994, legislation was passed in California that allowed the use of graywater in single family homes for subsurface landscape irrigation. Many other states do not currently have any legislation regulating graywater. However, many states are now realizing the value of alternative graywater systems and are pursuing research and development of such systems. The U.S. EPA considers the use of wetlands to be an emerging alternative to conventional treatment processes.
Graywater can contain disease organisms which originate from fecal material or urine entering bath, wash or laundry water. Potential pathogens in fecal material and urine, as well as infective doses, are listed in Chapter 7.
Fecal coliforms are a pollution indicator. Bacteria such as E. coli reveal fecal contamination of water and the possible presence of other intestinal disease-causing organisms. A high count is undesirable and indicates a greater chance of human illness resulting from
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