Use cascade analysis to optimize water networks

E P www.cepmagazine.org July 2006 45 The drive toward environmental sustainability and the rising costs of fresh water and effluent treatment have encouraged the process industries to find new ways to reduce fresh water and wastewater flowrates. At the same time, the development of systematic techniques for water reduction, reuse and recycling within a process plant has advanced. The introduction of water pinch analysis (WPA ) as a tool for the design of optimal water networks has been one of the most significant advances in the area of water conservation over the last decade ( 1 – 1 3 ) . Water pinch analysis is a systematic technique for implementing strategies to maximize water reuse and recycling through integration of water-using activities or processes. In the context of W PA, re u s e means that the effluent from one unit is used in another unit and does not re-enter the unit where it has been previously used, whereas re c y c l e a l l o w s the effluent to re-enter the unit where it has been used ( 1 ) . W PA involves two steps: 1. setting the minimum fresh water and wastewater flowrates (i . e . , the baseline water targ e t s ) 2. network design to achieve the baseline targ e t s . In setting the baseline targets and locating the pinch points, graphical techniques (such as composite curves) and numerical techniques (such as problem tables) have been used in heat * Foo is currently at the Univ. of Nottingham Malaysia Campus. E n v i ronmental Management