Performance evaluation of textile wastewater treatment techniques using sustainability index: An integrated fuzzy approach of assessment

The Textile Wastewater Treatment Technique (TWWTT) plays a prominent role in reducing effluent contaminants and thus keeping the environment cleaner. To select appropriate technology, evaluating the unified performance of TWWTTs towards social, technical, economic, and environmental sustainability parameters is of utmost importance. Though there are TWWTTs available, no ready framework exists that can help decision makers choose the appropriate technology based on their requirement. The study proposes a novel and systematic decision-making framework and a comprehensive mathematical model for judiciously selecting the TWWTT. It integrates fuzzy Delphi and hybrid Fuzzy Analytical Hierarchy Process (FAHP) approach of Multi Criteria Decision Making (MCDM). A total of 38 sub-indicators of sustainability are identified from past studies and expert opinions. Fuzzy Delphi is applied to identify the essential sub-indicators of sustainability, and hybrid FAHP is used to rank the sustainability dimensions, key sub-indicators, and alternatives. Twenty-eight sub-indicators are rounded down from the initial 38. The results from hybrid FAHP indicate that the technical dimension of sustainability is of paramount importance while selecting the TWWTTs followed by the economic dimension. The key sub-indicators for the selection of TWWTTs that scored higher than the others in technical, economic, social, and environmental aspects respectively are as under (i) color removal efficiency, COD removal efficiency, and quantity of sludge generation; (ii) cost of construction, operation, and maintenance; (iii) awareness within textile industries, public safety; (iv) effluent suitability for reuse and space requirements. The five TWWTTs, namely, Activated Sludge Process (ASP), Membrane Biological Reactor (MBR), Electrochemical Coagulation (EC), Mixed Bed Bio Reactor (MBBR), and the Rotating Biological Contactors (RBC), are compared using the estimated entropy weights also called as sustainability indices. MBR has scored the highest sustain ability index value, and ASP has the least value. MBR, EC and MBBR have higher sustainability indices proving them better sustainable alternatives than ASP and RBC. The MBR permeate quality is good enough to be reused in the textile industry without any further treatment. This will reduce the effluent quantity and groundwater demand leading to cleaner production of textile. The study will help the decision-makers in the overall assessment of the sustainability of TWWTTs prior to selection.