Page 229 - Membranes for Industrial Wastewater Recovery and Re-Use

198 Membranesfor Industrial Wastewater Recovery and Re-use

Table 4.6 Resulting inlet and outlet concentration for the processes after relaxing C1 for
P2 and P3

Waterl'argeta
Process 1 (Pl) 0 50 0 50
Process 2 (P2) 34 134 34 83
Process 3 (P3) 121 171 100 150
Water
Process 1 (Pl) 0 50 0 50
Process 2 (P2) 33 33 133 83
Process 3 (P3) 86 172 64 150

Technology limited (further referred to as LM software), Aspen Water@
commercialised by Aspen Technology, Water provided by UMIST to the members
of its Research Consortium and Water Close@ commercialised by American
Process with an emphasis on mills (American Process Inc, 2002; Retsina and
Rouzinou, 2002).
Aspen Water@ supports the work flow at each stage of the design, addressing
the total problem including process, utility and treatment systems. The company
is able to call upon its library of standard water-using unit operation including
boilers, evaporators, cooling towers, vessels, reactors and heat exchangers, as
well as purification technologies such as membrane processes. The flow-sheeting
structure allows users to develop new unit operation models for their own
specialised application. Moreover, using Aspen Water@ allows the water
chemistry to be modelled using the Aspen Properties@ physical property system.
Additionally, using the Aspen Equation Modeler@, dynamic simulation is
possible. Lourens (2002) provides an example of an industrial study performed
using Aspen Waterm.
The capability of WaterTarget@ is comparable to that of Aspen Water@ but it
does not have the functionalities of a library containing different unit operations
and treatment techniques. Simplified linear equations are provided to calculate
the effluent concentration in unit operations based on the influent concentration
and simplified treatment units are provided to mimic the processes involved. It is
assumed the effluent concentration is inferred from the influent concentration
and a single removal ratio determined for a specific contaminant. Cost functions
are linearly dependent on the flow rate.
The project builder of WaterTargetm (Fig. 4.2 1) allows different
contaminants to be selected, preferably limited to five in number, the processes
to be defined, the sources (mains water, ground water, etc.) and sinks
(sewer, surface water, etc.) to be identified and treatment techniques to be
selected. Any constraints on the system design can be imposed via the Bounds
editor (Fig. 4.22). Several types of bounds may be inserted, for example
restriction on flow rates, costs of connection of one process to another, or any