(614c) An MINLP Model for Sustainable Water Management in Macroscopic Systems Under Economic Penalty Scenarios

Authors: 
Rico-Ramirez, V., Tecnologico Nacional de Mexico en Celaya
Garibay-Rodriguez, J., Instituto Tecnologico de Celaya
Ponce-Ortega, J. M., Universidad Michoacana de San Nicolás de Hidalgo
In a sustainable system, the amount of water available from the natural sources in a watershed would be sufficient to meet the demands of the users without compromising their future availability. Furthermore, the amount and type of pollutants discharged over the water bodies would be completely degraded by the natural flora and fauna present in the aquatic ecosystems. However, this is not a common scenario.

Optimal resources distribution and wastewater treatment in a system (which involves a complex network of usage and disposal of water) cannot always be achieved just by imposing environmental regulations. In most cases, a compromise between the economic and environmental aspects has to be taken into account. This is not a simple task, because the needed investment for water treatment sometimes becomes prohibitive, especially when the users (e.g. domestic, industrial, agricultural) have many economic concerns regarding budgets, profitability of their products, market share, etc. An efficient strategy is still needed to mitigate harmful consequences on the environment.

Literature reports several efforts to deal with pollution over water bodies from a trading and penalty perspectives. These approaches are based on an ideal scenario, where charging environmental violators with fines and exchanging pollution credits among various sources achieve lower global costs while environmental constraints are met. However, none of those approaches has considered a macroscopic system which also takes into account the sustainability of water resources within a watershed and its surroundings.

This paper proposes a model to account for the sustainability of a macroscopic system through resources management, including the evaluation of alternative technologies for fresh water consumption reduction, and a distributed treatment system to treat wastewater from different sources; however, our approach also considers the possibility of penalty scenarios due to the violations of environmental regulations. The aim is to assess the implications of the penalties over the costs and the environmental goals of the problem.

Our approach results in an MINLP multi-period model which has been solved through the GAMS® modeling environment. A case study with different scenarios shows the scope of the proposed approach and the results show the significance of the results; the solution of the optimization problem allows finding the minimum investment to meet the desired environmental goals with respect to freshwater consumption and pollution over water bodies. This investment consists of the number, size and location of rainwater storage devices, the number, size, type and location of treatment plants in the distributed wastewater treatment system, the total amount of recycled wastewater and the total amount of fines charged to the users for violation of environmental constraints regarding pollution over water bodies.