Application of multi-criteria group decision-making for water quality management

Abstract

Abstract The water quality of the Haraz River basin has been adversely affected by various factors, including domestic sewage discharge, agricultural runoff, population density, and proximity to the Amol landfill. The presence of 11 point sources (PS) of pollution, primarily in the form of domestic sewage, has led to high concentrations of CBOD, COD, and ammonium in the downstream reaches of the river. To investigate the water quality of the basin, a one-dimensional water quality model, QUAL2Kw, was employed to simulate and calibrate the water quality along the river. The model was validated using river quality data collected during a period of low flow in September 2020 and February 2020. The simulation results reveal that the downstream water quality, as assessed using the IRWQIsc index, is relatively bad. To mitigate this issue, various scenarios for waste load allocation (WLA) were evaluated, including no treatment, primary treatment, advanced secondary treatment utilizing the Activated Sludge (AS) method, and advanced treatment via the Membrane Bioreactor (MBR) method. Utilizing the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) and Fuzzy TOPSIS decision-making model, it was determined that the optimal solution was the implementation of secondary treatment utilizing the Activated Sludge method for the 11 PS of pollution, while still adhering to Iranian water quality standard.