Gray Water and Treated Effluent Reuse

Graywater and treated effluent reuse is a concept that has been gaining favor in recent years. For reuse to be implemented, issues with water usage rights, health risks, and environmental impacts will need to be resolved. Even with the resolution of these issues, graywater reuse will not become prevalent until it has been shown to be cost effective. Cities looking to implement a city-wide or community graywater or treated effluent reuse system would be particularly interested in knowing the cost savings created by water reuse. The reuse of graywater and treated effluent impacts demand for potable water supply as well as the loads placed on wastewater treatment facilities, therefore a fully integrated urban water system must be considered in any cost analysis. This report outlines a computer program developed to grapple with the problems of creating a fully-integrated urban water model. This program is capable of calculating the cost of a wide array of scenarios ranging from no urban water reuse to complete reuse of graywater and/or wastewater effluent. It considers factors such as rainfall volumes, population data, residential water demand, industrial water demand, and of course water supply and redistribution costs. Furthermore, the program can perform analyses on a seasonal or annual basis to account for varying residential irrigation demands. Average household lawn area and lawn irrigation requirements can be changed and calculations are automatically updated based on mean temperature and rainfall frequency.