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186 Membranes for Industrial Wastewater Recovery and Re-use

References
Brauns, E. (2001). Calculation of cross-flow reverse osmosis at your desk.
Desalination and Water Reuse, 10(4), 18-25.
Brauns, E., Doyen, W., Dotremont, C., Van Hoof, E. and Genne, I. (2002). A
pragmatic cost calculation and design software tool for pressure driven
membrane filtration systems. Desalination and Water Reuse, 12( l), 40-44.

4.2 Water pinch analysis

4.2.1 Introduction
As is apparent from the example industrial sectors discussed in Chapter 2, the
use of water within and its discharge from an industrial site can be very complex.
Minimising water consumption is obviously desirable on environmental and
economic grounds, but it becomes very difficult to determine the extent to which
this can be done without endangering product quality. The complexity is
compounded not only by ignorance of water volumes involved, but also of water
quality with respect to key pollutants. The latter can relate both to effluents
generated and process water quality demanded by specific processes. Such basic
issues have to be addressed ahead of any assessment of water purification
technologies, since such purification may not even be necessary. Moreover, the
problem of assessment of water demand, discharge and quality is generally
compounded by the disparate knowledge base for individual water-consuming
processes throughout the company. Clearly an overview is required
encompassing all unit operations demanding and discharging water throughout
any one site. This information can then be used to form the basis of what
is referred to as pinch analysis which, when applied to water systems, is usually
referred to as water pinch.
In the following sections the water pinch concept is discussed in detail, and
practical methods for its application outlined. Water pinch provides a means of
determining the theoretical minimal overall water consumption for a site with
different processes, as well as indicating the requirements of a purification
technology based on a specific scenario. Although the concepts of water pinch
might seem relatively simple, applying them under real process constraints
demands a comprehensive knowledge of the overall industrial process to which it
is applied. Moreover, as many parameters are involved and interrelationships
between the various process streams can be very complex, it is apparent that
dedicated software is necessary to expedite the application of the methodology,
The latter is widely available although, as with the reverse osmosis software
discussed in Section 4.1, the software is merely a tool rather than providing a
process solution.