Development of a minimum incremental cost model for process plant water integration and retrofit

The study presents a method for targeting minimum incremental cost for water reuse projects particularly in process plant water integration and retrofit. Previous works aimed for the minimum amount of freshwater generation as a target, costing out the designed network, and selecting the one featuring the lowest cost. This study shows that this does not necessarily minimize total cost. The study focused on developing a model incorporating investment, operating and maintenance costs to come up with an optimal solution of water reuse at a minimum cost. This was indirectly achieved through targeting the maximum annual net savings using genetic algorithm through Excel Premium Solver. After which, the model was simulated using data from an existing industrial facility and compared to the conventional model. Results showed that the minimum incremental cost model attained the same minimum freshwater target that was achieved by the conventional model. Freshwater consumption was significantly reduced by 68 percent, amounting to an annual water savings of as much as Php.1.17 M. Behavior of the model was also evaluated by applying nine scenarios with varying interest rates and equipment life for pumps, pipes and tanks. The minimum incremental cost model\u27s behavior was consistent for all scenarios. The generated water reuse networks have the least cost compared to the conventional model