Presenting a two‑objective model to manage spatiotemporal pollution distribution in river with consideration of consumer demand

Abstract

Pollution of surface water especially rivers has created serious problems for both human health and environment. Due to the severe shortage of surface water resources and their pollution, it is very important than ever to plan wisely how to use water resources, especially in areas that consume more water, like drinking water, agriculture, and industry. A majority of real-world decision-making issues, especially in the field of water resources management, are multi-objective issues in which decisions are made based on different goals, sometimes conflicting goals. In this research, a new approach regarding pollution discharge management is introduced. A two-objective optimization problem is presented in this approach to find the optimal timetable and spatial planning of pollution entry to the river as well as the optimal downstream consumption pattern. For this purpose, the hydraulic and qualitative data of Gheshlagh River in Kurdistan were used to present time and location schedule for pollutants entry from eight-point pollution sources of the river in two-objectives in two different scenarios. The two-objective optimization process is performed using the MOPSO algorithm. In this case, there are 224 decision variables. From each scenario, three optimal points are selected, and the results are presented for those points. In both scenarios, the total pollution load of the polluting sources entered the river in the desired time period and from the obtained optimal spatial locations. In scenario 1, the concentration, was lower than the allowable limit in all optimal points and the consumer water demand was not fully satisfied, especially in optimal point 1. But at the second optimal point, the downstream water demand is fully satisfied showing the efficiency of the proposed model. In the second scenario, the obtained level of pollution in the optimized condition exceeded the allowable limit in some minutes and is vulnerable. Therefore, in order to reduce damage to the consumer, water harvesting is prohibited at these times. In this scenario, unlike the first optimal point, the second and third ones satisfy most of the downstream water demand.