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This study aims to provide relevant information to plan and design urban wastewater infrastructure to achieve low energy and GHG footprint. The study addresses the following objectives, 1) To study the influence of treatment technology choices, scale of operation, variations within and across treatment stages and disposal standards on energy use and total GHG emissions, 2) To understand the drivers influencing the total energy and GHG emissions in an urban wastewater infrastructure and comparison of various design options, taking Delhi as a case study and 3) To analyze the potential of application of renewable energy to reduce overall energy and GHG footprints of urban wastewater treatment systems.
This study has looked into the entire Urban Wastewater Chain and used models based on the mass balance approach and they form the basis of LCA model for estimating energy consumption and GHG emissions from various sources. The study presents the sources of energy and carbon emissions from different technologies, different stages and processes of treatment. It covers 14 different wastewater treatment options and estimates are based on primary data from 51 WWTPs in India and UK. The study also looked into the Water-Energy-Carbon nexus with reference to wastewater infrastructure of a city, including wastewater transport and treatment, and takes into account the embodied energy and emission of the materials used in the infrastructure. The data is analysed separately for various regions within a city and for centralized and decentralized systems to understand the factors that influence energy use and GHG emissions. To check the feasibility of application of renewable energy, the design of the solar PV was considered. The study offers information and insights for designing low carbon strategies for urban wastewater infrastructure.
Total energy use of WWTPs in India ranged from 0.09-8.33 kWh/m3. Average electrical energy intensity in WWTPs in India is much lower (0.14 kWh/m³) than that in the UK (0.46 kWh/m³). The average net energy and GHG footprint of wastewater infrastructure in NCT of Delhi is 0.26 kWh/m3 and 1.426 kg CO2-eq/m3 respectively. Resource recovery methods reduce the energy and GHG footprints by 30%-40%. In centralized and decentralized WWTP, 44.6% and 100% of the electrical energy used was substituted by the solar PV, respectively. With India planning to achieve ambitious target of using renewable energy, this study will help the urban planners and policy makers to focus on the wastewater treatment sector to create a more reliable and efficient system which will facilitate better urban growth. Shifting the energy economics from coal based electricity generation to use of solar PV modules can change the dynamics of the country and help to achieve the millennium goals
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