On-line version ISSN 1816-7950
Print version ISSN 0378-4738
Water SA vol.34 n.3 Pretoria Mar. 2008
JF GouwsI, II; T MajoziI, III
IDepartment of Chemical Engineering, University of Pretoria, Lynnwood Road, Pretoria 0002, South Africa
IILogistics and Quantitative Methods, CSIR Built Environment, PO Box 395, Pretoria 0001, South Africa
IIIDepartment of Computer Science, University of Pannonia, Egyetem u. 10, Veszprem, H-8200, Hungary
Wastewater minimisation in chemical processes has always been the privilege of continuous rather than batch plants. However, this situation is steadily changing, since batch plants have a tendency to generate much more toxic effluent compared to their continuous counterparts which are usually encountered in bulk manufacturing.
Past methodologies for wastewater minimisation in batch processes have focused on operations based on mass transfer. They do not take into consideration the reuse of wastewater as part of product formulation. Reusing wastewater in product formulation has the major advantage of negating much of the effluent produced, thereby enabling a process to operate in an almost zero-effluent manner.
Presented in this paper is a mathematical technique for the simultaneous design and scheduling of batch operations operating in a near-zero-effluent manner. The technique determines the number and size of the processing vessels, while ensuring maximum water reuse in product. The technique was applied to an illustrative example, and an 80% savings in wastewater was achieved, with a corresponding plant design that achieves the required production.
Keywords: zero-effluent, batch process, wastewater minimisation
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Received 28 January 2008
Accepted in revised form 22 May 2008