Abstract A close examination of the World-Wide water demand-supply balance reveals that in many countries, the demand is rapidly outstripping the available supply. A single most resource readily available to make up the deficit is reuse of wastes produced in industry, agriculture, and domestic uses. Unfortunately, these waste waters cannot be reused directly without upgrading their quality. Conventional waste and water treatment methods are both inadequate and uneconomical to prepare these wastes for reuse. Membrane processes, primarily developed for conversion of saline waters to fresh quality water supplies offer considerable promise for preparing the wastes for multiple reuse.