A Graywater Reuse Study in Southern Arizona and the Water Conservation Demonstration Garden in San Diego, California

An Essay on a presentation made by Val Little to Diwan al-Mimar on May 31, 2001

Prepared by Majd Musa with Mohammad al-Asad, 2002

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Support for the publication of this essay has been made possible by a grant from the Prince Claus Fund for Culture and Development. Additional support has been provided by Darat al-Funun - The Khalid Shoman Foundation





Table of content: 

1. Introduction

2. Residential graywater Reuse Study

3. The Water Conservation Demonstration Garden

4. Questions and Answers

5. Notes

6. List of Figures 



In arid regions, the issue of water conservation is one of great significance for the sustainability of water resources. One effective approach to water conservation is the reuse of graywater. Graywater is all wastewater generated in the household excluding toilet wastes. Its sources in homes include sinks, showers, tubs, and washing machines. Graywater recycling is not limited to large-scale projects, for individual households can effectively save and reuse their graywater for irrigating landscapes and flushing toilets (1). Another approach is the incorporation of principles and practices of water conserving landscapes (2). The presentation of Val Little (3) dealt with these two approaches to water conservation. Concerning graywater reuse, Little discussed a residential graywater research study that the Water Conservation Alliance of Southern Arizona (Water CASA) (4) undertook in the greater Tucson (5) area between the years 1998 and 2000. Little also discussed demonstration gardens as tools for educating the public in water conservation, particularly in the creation of water conserving landscapes. More specifically, she presented the example of the Water Conservation Demonstration Garden in San Diego, California.

 Residential Graywater Reuse Study

The residential graywater reuse study that Water CASA carried out was supported by the Arizona Department of Water Resources, the Arizona Department of Environmental Quality, and the Pima County Department of Environmental Quality. The study included two parts, each of which examined one aspect of graywater use in the greater Tucson area. The first part was a survey that looked into the number of households that used some portion of the graywater they generated, and examined their graywater resources. The second part examined health concerns relating to the use of graywater, and the potential of graywater for transmitting disease. Little emphasized that the subject of safety relating to graywater reuse is one that needed to be cleared up as it constituted a major obstacle in the way of getting graywater reuse legalized. Consequently, the second part of the study included testing the water quality of residential graywater and the effects of that graywater on the soil that was irrigated with it (6).

Little provided a quick overview of the survey part of the study. She mentioned that the study team mailed a questionnaire to owner-occupied, single-family residences in the area of the study. Survey recipients were asked whether they reuse or do not reuse portions of their graywater. The results of this survey were used to draw tentative conclusions concerning graywater reuse in the Tucson area. It showed that 13 percent of the single-family residences used a portion of the graywater they generated. The survey also showed that those users of graywater did not obtain the permits required by the county in order to reuse their graywater legally. Regulatory agency in Arizona, which is the Arizona Department of Environmental Quality, had specific rules that needed be followed when reusing graywater, and those rules were not taken into consideration by those surveyed. Little added that those 13 percent of households who reuse their graywater translated to somewhere between 20,000 and 30,000 of the households of Pima County, which represents 50,000 to 80,000 persons. According to Little, the results of the study caught the attention of the regulatory agencies, which knew of the illegal reuse of graywater, but were not aware of it being so widespread. The study therefore brought attention to the need to simplify existing regulations for residential graywater reuse, and to create new ones that are based upon "performance standards," an issue that will be discussed in more details below.


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