Water Reuse And Recycling Are Becoming   Much More Common As Demands For Water Exceed Supply. Unplanned reuse occurs as the result of waste effluents entering receiving waters or ground water and subsequently being taken into a water distribution system.

Planned reuse utilizes waste-water treatment systems deliberately designed to bring water up to standards required for subsequent applications. The distinction also needs to be made between recycling and reuse. Recycling occur internally before water is ever discharged. Reuse occurs, for example, when water discharged by one user is taken as a water source by another user.

Reuse of water continues to grow because of two major factors:

(i)         Lack of supply of water.

(ii)        Widespread deployment of modern water treatment processes significantly enhances the quality of water available for reuse.

Since drinking water and water used for food processing require the highest quality of all large applications, intentional reuse for portable water is relatively less desirable. This leaves three applications with the greatest potential for reuse:

(i)             Irrigation for cropland, golf course, and other applications requiring water for plant and grass growth this is the largest potential application for reuse water and one that can take advantage of plant nutrients, particularly nitrogen and phosphorus, in water.

(ii)            Cooling and process water in industrial applications. For some industrial applications, relatively low quality water can be used and secondary sewage effluent is a suitable source.

(iii)           Ground water recharge. Ground water can be recharged with reused water either by direct injection into an aquifer or by applying the water to land, followed by percolation into aquifer.