Hierarchical and Fuzzy Analysis for Wastewater Treatment Criteria Selection

Wastewater treatment is often required before discharging treated water into rivers and lakes to comply with municipal water disposal regulations. Basic systems such as waste stabilization ponds, aerated lagoons, and activated sludge treatment plants are commonly selected by engineers. However, selecting the appropriate treatment system is challenging despite known parameters and variables such as flow rate, available area, and population density. Cost, including total investment and operational expenses, is often overlooked. Selecting an alternative treatment is challenging due to the lack of standardized rules and specialized software. Hierarchical and fuzzy scale methods can help identify the most significant variables, reducing uncertainty and improving correlation accuracy. A hierarchical scale (-1, 0, 1) was applied to develop a triangular mathematical model for comparison. Coefficients for four fuzzy scales were calculated for each wastewater treatment type. Results indicate that total investment and population density were consistently rated as 1, making them less reliable for decision-making compared to flow rate and area, which had varying fuzzy values (-1, 0, 1), indicating their significance. A linear correlation of R² = 0.65, p = 0.04 was observed between these variables. Additionally, total investment correlated with area, flow rate, and population density, making it a useful metric for budget estimation.