Analysing water-energy-GHG nexus in a wastewater treatment plant of Mumbai Metropolitan Region, India

Abstract

Developing nations are advancing towards improving municipal wastewater treatment infrastructure. However, there have been limited efforts in these countries to understand Water-Energy-GHG nexus for sustainable wastewater treatment. This study evaluates operational energy, total embodied energy and corresponding GHG emissions of a widely implemented municipal wastewater treatment technology in Mumbai Metropolitan Region of India. Data for wastewater inflow, total energy consumption and materials used in the unit processes of the treatment plant were collected and analysed. Direct GHG emissions from the plant were estimated using the method proposed by the intergovernmental panel for climate change (IPCC). The energy embodied within the materials used in the construction and operations of the plant was estimated using country-specific information. The results show that the energy intensity for plant operation and chemical oxygen demand (COD) removal was 0.23 ± 0.05 kWh/m3 of wastewater treated and 1.12 ± 0.77 kWh/kg of COD removed, respectively. The embodied energy in chemicals and building materials during the plant's life cycle contributed 19% of the total embodied energy. Wastewater inflow with specific average energy consumption in wet-well pumping and blowers showed a negative and positive correlation, respectively. The total GHG emissions (direct and indirect) from the plant were ~0.22 kgCO2eq/m3 of wastewater treated. The study presents the energy accounting of a wastewater treatment system and extensive analysis of infrastructural data, which is scarcely accessible and available in developing countries.