Supply-chain environmental effects of wastewater utilities

Abstract

This letter describes a comprehensive modeling framework and the Wastewater-Energy Sustainability Tool (WWEST) designed for conducting hybrid life-cycle assessments of the wastewater collection, treatment, and discharge infrastructure in the United States. Results from a case study treatment plant which produces electricity using methane offgas are discussed. The case study system supplements influent with 'high-strength organic waste' to augment electricity production. The system balance is 55 kg of greenhouse gases per million liters of wastewater. Sensitivity analysis confirms that reusing biogas from anaerobic digestion for electricity reduces life-cycle greenhouse gas emissions by nine times. When biogas is captured and reused for electricity, material production (e.g., chemicals and pipes) and the corresponding supply chains, rather than energy production, are responsible for most of the environmental effects. When biogas is flared, the material and energy production contributions are similar.

Feasibility of Water Efficiency and Reuse Technologies as Demand‐Side Strategies for Urban Water Management

“…Further investigation of the environmental externalities associated with both supply-and demand-side water projects can provide decision-makers with a more complete view of the full environmental costs of water management. For example, reduction of water demand volume from water efficiency technology adoption is associated with direct impacts on drinking water distribution and wastewater treatment plant operations (Stokes and Horvath, 2010, 2009Alvarez-Gaitan et al, 2014;Lundie et al, 2004;Short et al, 2014). Indirect impacts from avoided importation, desalination, and recycling supply-side projects, which can be associated with higher energy-use intensity than are traditional water provisions, also must be estimated.…”

Boundaries matter: Greenhouse gas emission reductions from alternative waste treatment strategies for California's municipal solid waste

“…Both digesting organic waste and improving landfill gas capture rates can be done using already existing infrastructure. Conventional wastewater treatment plants already have anaerobic digesters for liquid wastes (Stokes and Horvath 2010), and co-digestion of liquid and solid wastes has been shown to increase methane generation (Edelmann 2000;Sosnowski et al 2008), though the mixing of liquid and solid wastes brings on added risks of pathogens, and can limit the possibilities for land application of the waste (Murray et al 2008). …”

Life cycle impact analysis of tertiary treatment alternatives to treat secondary municipal wastewater for reuse in cooling systems

“…These studies have identified energy consumption, chemical manufacturing, and sludge handling and disposal to be the main contributors to environmental emissions . LCA results for a case study of a wastewater treatment plant that produces electricity using methane gas obtained from the biological treatment of high‐strength organic wastewater were developed using the WWEST model . The results of the case study showed that the treatment phase dominated the results, contributing 63–106% to each emission category .…”

“…LCA results for a case study of a wastewater treatment plant that produces electricity using methane gas obtained from the biological treatment of high‐strength organic wastewater were developed using the WWEST model . The results of the case study showed that the treatment phase dominated the results, contributing 63–106% to each emission category . Another LCA study for municipal wastewater reclamation and reuse alternatives showed that tertiary treatment contributed to additional environmental impacts, but the benefit of reusing water for industrial and commercial purposes helps preserve freshwater .…”

“…A wastewater‐energy sustainability tool (WWEST) was designed to conduct hybrid life cycle assessments of the wastewater collection, treatment, and discharge infrastructure in the United States. This tool uses emission factors incorporated in the economic input–output LCA (EIO‐LCA) model and Gabi , process‐based LCA model, to determine the environmental effects of multiple wastewater treatment activities, including material production, material delivery, equipment use, sludge disposal, and some direct GHG emissions . The WWEST tool requires detailed data for allocation of costs inputs and deals mainly with primary and secondary wastewater treatment processes.…”