Page 134 - Sustainability in the Process Industry Integration and Optimization

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must be considered so that subsequent water-using processes
will not be adversely affected. This aspect is discussed in
more detail in Section 5.2.4.
Several particular methodologies for water minimization are
listed in the chapter by Klemeš and Perry (2007b):
• Water Pinch Analysis techniques
• Mathematical optimization techniques
• Efficient management and control of process operations
• Integrating optimization and production planning techniques
in conjunction with real-time plant measurements to control
for product quality and minimize losses
5.2.4 Minimizing Water Usage and Wastewater

Overview of the Measures
The task of minimizing water usage and wastewater discharge has
received considerable attention during the last few years as water has
become more costly and an environmentally strategic concern. Smith
(2005) summed up the measures applied to minimizing water usage
and wastewater as follows:
1. Process changes: These include all the measures described
under item 1 of the listing in Section 5.2.3. Water quality can
also be improved by reducing the use of certain processing
components, such as hazardous cleaning agents, chemicals,
and additives. Additional process changes may be driven
through inspection or through process optimization via
developed technologies—for instance, Process Integration
(Pinch Technology). Reduced consumption and increased
efficiency may be achieved either by upgrading equipment
or adopting new technologies.
2. Reuse: This is a viable strategy when wastewater from a given
operation is used directly in other operations, provided that
the pollutants in the reused water do not disturb the processes
in the downstream operations. Methods for maximizing
water reuse are detailed in Section 5.3, along with a discussion
on the use of recycled water in food processing.
3. Regeneration reuse: This is the process of purifying wastewater
from one operation and then reusing it in another operation
or process.
4. Regeneration recycling: Here the contaminants in the
wastewater are only partly eliminated before the water is
returned for use in the same process.