Integrated Life Cycle Assessment and Life Cycle Cost Assessment based fuzzy multi-criteria decision-making approach for selection of appropriate wastewater treatment system

The current study proposes a comprehensive fuzzy formulated Multi-Criteria Decision Making (MCDM) framework with integrated Life Cycle Assessment (LCA) and Life Cycle Cost Assessment (LCCA) approach for selection of best suitable wastewater treatment (WWT) system, especially for multi-storeyed residential buildings. By utilising a thorough literature survey, experts' opinions and questionnaires, the study attempts to identify four dimensions of sustainability with associated key nineteen indicators. Furthermore, the study is benefited by undertaking quantitative parameters related to environmental and economic sustainability assessed by LCA and LCCA respectively. The proposed three-phase methodological framework illustrates the identification of widely used WWT systems in the first phase followed by Fuzzy Analytic Hierarchy Process (FAHP) assessment for criteria and indicators' screening and finalisation in the second phase and ranking of alternative by Fuzzy Technique for Order of Preference by Similarity to Ideal Solution (FTOPSIS) in the third phase. Moreover, the current paper suggests a novel approach of incorporating "environmental floor" in multi-storeyed building, where gravity governed nature-based wastewater treatment tanks of Decentralized On-Site Integrated WAste Management (DOSIWAM) system can be positioned. To test the proposed framework, the sustainability of DOSIWAM system is compared with five widely used wastewater treatment systems viz. membrane bioreactor (MBR), moving bed biofilm reactor (MBBR), sequencing batch reactors (SBR), activated sludge process (ASP), soil biotechnology (SBT). Results of alternative ranking indicate DOSIWAM (allocated at environmental floors) as the best suitable option followed by the second, third and fourth rank of MBR, SBT and SBR respectively whereas, MBBR and ASP are the least preferred. It has been observed that the experts prefer mostly natural treatment systems since they are more sustainable in environmental and economic considerations. In addition, by changing the weights of the main criteria, sensitivity analysis is carried out considering five scenarios, which signifies in three out of five scenarios; relative percentage change in criteria weight does not affect the first rank of the DOSIWAM system. The developed framework successfully facilitates a reliable base for the selection of the best suitable WWT system for multi-storeyed residential building and could be made available to the relevant local planning authority to incentivize the effort undertaken for the welfare of citizens as well as the government.