Abstract
Municipal sewage contains significant embedded resources in the form of chemical and thermal energy. Recent developments in sustainable technology have pushed for the integration of resource recovery from household wastewater to achieve net zero energy consumption and carbon-neutral communities. Sewage heat recovery and fit-for-purpose water reuse are options to optimize the resource recovery potential of municipal wastewater. This study presents a comparative life cycle assessment (LCA) focused on global warming potential (GWP), eutrophication potential (EUP), and human health carcinogenic potential (HHCP) of an integrated sewage heat recovery and water reuse system for a hypothetical community of 30,000 people. Conventional space and water heating components generally demonstrated the highest GWP contribution between the different system components evaluated. Sewage-heat-recovery-based district heating offered better environmental performance overall. Lower impact contributions were demonstrated by scenarios with a membrane bioreactor (MBR) and chlorination prior to water reuse applications compared to scenarios that use more traditional water and wastewater treatment technologies and discharge. The LCA findings show that integrating MBR wastewater treatment and water reuse into a district heating schema could provide additional environmental savings at a community scale.
Highlights
Emerging wastewater treatment technologies permit application of waste-to-resource approaches, in the recovery of various products from municipal wastewater
The life cycle assessment (LCA) calculations were performed with OpenLCA ver. 1.8.0 [31] using the TRACI 2.1 impact assessment method developed for North America [32] and the approach previously described by Schoen et al [13]
The core interest in the current study was the environmental impact of a transitional design whereby sewage heat recovery is used for district heating alongside community-based wastewater treatment for water reuse
Summary
Emerging wastewater treatment technologies permit application of waste-to-resource approaches, in the recovery of various products from municipal wastewater. This idea has historically been exhibited through the production of compost and fertilizer for agriculture, but increasingly complex processes have been developed enabling the recovery of resources in the form of chemical energy and heat [1,2]. Sewage heat recovery systems are an attractive waste-to-resource approach that has been gaining interest in recent years [3,4]. Global water insecurity has resulted in emerging wastewater reclamation initiatives and applications in recent years [8,9,10]. The concept of extracting wastewater from an existing sewer to Environments 2020, 7, 36; doi:10.3390/environments7050036 www.mdpi.com/journal/environments
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