Zero Effluent Plant Synthesis Formulation

The zero effluent synthesis formulation not only determines the optimal number and size of the storage and processing units, but also determines the schedule that will allow the resulting plant to operate in a near zero effluent operation. This is beneficial since scheduling considerations are taken into account during the plant synthesis phase. The exact problem considered in this formulation is given in the following section. 

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Two formulations were derived. The first deals with minimising the amount of effluent produced from an operation where wastewater can be reused in product formulation and the plant structure is known. The minimisation is achieved by scheduling the operation in such a manner as to maximise the opportunity for wastewater reuse. The second deals with the synthesis of a batch process operating in zero effluent mode. The formulation determines the number and size of processing and storage vessels as to minimise the cost of the equipment and the amount of effluent produced from the resulting operation, while achieving the required production. 

The methodology deals with two types of problems, namely, the wastewater minimisation problem within a given plant structure and the plant synthesis problem. Each of these is dealt with in the form of two mathematical formulations. The first mathematical formulation deals with the scheduling of an existing operation as to produce near zero effluent. The second mathematical formulation deals with the... 

The zero effluent synthesis formulation was applied to a second illustrative example. In the example the number of processing units and the size of the central storage vessel were not known. The resulting plant required only 3 processing units and no storage vessel. The resulting schedule produced 68% less effluent than the same operation without wastewater reuse. 

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