(620e) OPTIMAL Design of Distributed TREATMENT SYSTEMS for the Effluents Discharged to the Rivers

The affluents discharged into rivers have an adverse impact on the environment owing to their pollutants; for that reason, the environmental regulations are now stricter, and the costs of water  and waste streams treatment  have increased significantly in recent years. A common practice for the treatment of waste streams is to have a central treatment plant. This practice has the disadvantage of wasting many streams that can be reused because some of them satsify the environmental regulations, and therefore, the amount of waste streams to be treated is increased. In thisregard, mass integration is an alternative to this problem, which is a holistic technique to optimize the location, separation and generation of streams. By means of mass integration it has been able to find configurations that allow to take advantage of the process streams by minimizing fresh sources. This paper presents a mixed integer non linear programming model to minimize the environmental impact caused by the discharge of effluents into the rivers at the lowest possible cost. The model was formulated to predict the behavior of the watershed impacted for the polluted discharges through the material flow analysis technique; therefore, all discharges and extractions are considered as well as the chemical reactions that take place in the watershed. The watershed model is combined with a disjunctive model for the optimal location of distributed treatment units and the selection for the type of treatment. The model considers all effluent discharged to the macroscopic system taking as constrains the maximum allowable concentration in each reach and the discharged concentration to the catchment area to ensure the sustainable natural degradation. The model allows finding the optimal location of treatment units, such that the environmental impact can be minimized because each tributary has the potential to be treated with different technologies. The objective function is aimed at minimizing the total annual cost, which includes the effluents treatment cost and the location-based cost of the new treatment plant. The proposed model is applied to clean two important watesheds in the word (one in Egypt and other in Mexico); and the results show the the proposed distributed treatment allows to satisfy the environmental constraints at the minimum cost.