Developing a Closed-Loop Water Conservation System at Micro Level Through Circular Economy Approach

Abstract

A closed loop system for micro-level conservation of fresh water at household user point has been developed in this work in a comprehensive circular economy (CE) framework encompassing technical, environmental and economic aspects in a concurrent manner. The system has been developed through field survey of households in an urban setting in Indian context and experimental investigation on membrane filtration and recirculation of grey water generated from domestic use like cooking, bathing, washing etc. Pollution load of the grey water utilized in the sample involved high alkalinity (pH = 9.00), total suspended solid (TSS = 536 mg/L), odour (TON 2). Membrane based filtration process has been developed to ensure that the reclaimed water is of acceptable quality as alkalinity decreases to 7.2, TSS reduces to 95 mg per litre and odour in terms of TON reduces to one. Economic feasibility of implementing such a system is assessed by cost benefit analysis. Estimated annualized total cost (capital and operating) for treating and reusing a cubic meter of waste water in this CE framework amounts to US $1.5 only. Preference score derived from utility estimates of conjoint analysis (CA) reveal that consumers have positive attitude to accept water conservation strategy in circular economy framework. The ideal composition of reclaimed grey water to be preferred is odourless (TON value near 1), low TSS (less than 102 mg/L) and neutral pH (nearly7.00) The study reveals that about half of fresh water demand per day per capita can be saved by developing a closed-loop production system at micro level, where grey water generated as waste from domestic use is not discharged as followed in traditional open-ended economic model. Instead of take-make-use-discharge, waste water is added in the production system as a resource. After applying an advanced cost-effective clean technology, grey water is kept in a material loop and usage creating further value for a longer period. Sustainable water system development by this holistic circular water conservation approach is no longer an option but a necessity to protect the life-sustaining valuable freshwater resource. Developing water conservation system in closed-loop model provides a novel solution as it will yield positive and significant utility and economic value in a very cost effective green design.