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| The Urban Water Center at Colorado State University is actively involved in a number of research projects investigating the reuse of graywater in individual households under the direction of Dr. Larry Roesner and Dr. Sybil Sharvelle. This webpage provides brief introduction to graywater reuse and the Urban Water Center’s involvement in researching this emerging water conservation technique. | ||||||
| What is graywater? | ||||||
| Graywater is the water that drains from bathroom sinks, showers and washing machines in a typical household. Water that drains from kitchen sinks, dishwashers and toilets is not considered graywater because it contains higher levels of organic waste. | ||||||
| Why reuse graywater? | ||||||
| The primary reason for reusing graywater is to reduce a household’s demand for potable (fully treated) water. Potable water is treated to EPA drinking water standards which ensure that persons that drink, cook or bathe in that water will not get sick. In most households, potable water is also used to flush toilets and irrigate outdoor landscapeds. However, water used for toilet flushing and outdoor irrigation does not need to be treated to such high standards. By reusing graywater for toilet flushing and outdoor irrigation, instead of using potable water, a household can cut its potable water demand by up to 50% at certain times of the year. | ||||||
| How do you reuse graywater? | ||||||
| Most households that reuse graywater
use it to flush toilets and irrigate plants and lawns outdoors.
After entering drains, the graywater is collected and stored in
a container until it is needed for those purposes. | ||||||
| Is graywater safe? | ||||||
| The best answer at this time is “We don’t know.” Graywater is known to contain bacteria and other pathogens that do not make it safe for drinking, cooking or bathing. However, in the United States the restrictions vary from state to state. Some states have deemed it safe for toilet flushing and outdoor irrigation while others have restricted its reuse due to potential health concerns and/or water rights issues. The Urban Water Center is currently involved in a first-of-its-kind study to evaluate the potential health concerns of reusing graywater. Preliminary results show that graywater is indeed safe for a variety of purposes such as toilet flushing and outdoor irrigation. | ||||||
| The Urban Water Center's graywater research | ||||||
| The Urban Water Center has been involved with graywater reuse research for the past 8 years. A summary of past and current research projects is provided below. | ||||||
2000-present – Household Graywater Reuse System Evaluation The Urban Water Center has been conducting ongoing research at a household with an existing graywater reuse system since 2000. Various research projects have evaluated the use of various treatment technologies such as filtering, UV and peroxide to reduce bacteria and pathogen concentrations. 2007-present – Constructed Wetland Treatment of Graywater In 2007, the Urban Water Center began evaluating the effectiveness of using constructed wetlands for treating graywater. The project is evaluating the effectiveness of two types of wetlands, a free-surface wetland and a subsurface gravel wetland. The 12-month study began in September 2008. Preliminary results can be viewed here. (Jokerst EWRI paper) Photo gallery of Constructed Wetland system 2008-present – Long-Term Study on Landscape Irrigation using Household Graywater This 3-year study is a first-of-its-kind study to evaluate the effects of graywater reuse for outdoor irrigation. The study involves collecting plant and soil samples from several locations that have been (or will be) irrigated with graywater, and analyzing those samples for constituents that may be of concern for human health and the environment. 2009 – Effectiveness of Graywater Reuse 2009 – Economics of Graywater Reuse | ||||||
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