CO2e footprint and eco‐impact of ultralow phosphorus removal by hydrous ferric oxide reactive filtration: A municipal wastewater LCA case study. (25th August 2022)

• Record Type: Journal Article
• Authors: Taslakyan, Lusine; Baker, Martin C.; Shrestha, Dev S.; Strawn, Daniel G.; Möller, Gregory
• Is Part Of: Water environment research. Volume 94:Number 8(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-08-25
• Subjects: carbon footprint -- environmental impacts -- eutrophication -- life cycle assessment -- phosphorus removal -- reactive filtration -- wastewater treatment; Water quality management -- Periodicals; Water -- Purification -- Periodicals; Water -- Pollution -- Periodicals; Water -- Pollution; Water -- Purification; Water quality management; Sewage; Water Pollution; Periodicals; Electronic journals; Periodicals; 628.16
• DOI: 10.1002/wer.10777
• Languages: English
• ISSNs: 1061-4303

Abstract

Abstract: Dual upflow reactive filtration by a slowly moving sand bed with continuously renewed, hydrous ferric oxide‐coated sand is used for removing polluting substances and for meeting the ultralow 0.05 mg/l total phosphorus discharge permit limits at a 1.2 million liters per day (0.32 million gallons per day) water resource recovery facility in Plummer, Idaho, in the United States. A life cycle assessment (LCA) of this reactive filtration installation was carried out to assess the environmental hotspots in the system and analyze alternative system configurations with a focus on CO2 equivalent (CO2 e) global warming potential, freshwater and marine eutrophication, and mineral resource scarcity. "What if" scenarios with alternative inputs for the energy, metal salts, and air compressor optimization show trade‐offs between the impact categories. Key results that show a comparative reduction of global warming potential include the use of Fe versus Al metal salts, the use of renewable energy, and the energy efficiency benefit of optimizing process inputs, such as compressor air pressure, to match operational demand. The LCA shows a 2 × 10 −2 kg CO2 e footprint per cubic meter of water, with 47% from housing concrete, and an overall freshwater eutrophication impact reduced by 99% versus no treatment. The use of renewable hydropower energy at this site isolates construction concrete as a target for lowering the CO2 e footprint. Practitioner Points: The main LCA eco‐impact hotspots in this dual reactive filtration tertiary treatment are construction concrete and the ferric sulfate used. Iron salts show smaller impact in global warming, freshwater eutrophication, and mineral resource scarcity than "what if scenario" aluminum salts. The energy mix for this site is predominantly hydropower; other energy mix "what if" scenarios show larger impacts. Operational energy efficiency and thermodynamic analysis show that fine tuning the air compressor helps reduce carbon footprint and energy use. LCA shows a favorable 2 x 10‐2 kg CO2e/m3 water impact with 99% reduction of freshwater eutrophication potential versus no treatment. Abstract : The LCA of tertiary reactive filtration used to meet ultralow P discharge limits shows freshwater eutrophication impact was reduced by 99% and a carbon footprint dominated by construction concrete. Reduction of carbon footprint includes use of Fe versus Al metal salts, renewable energy, and energy efficiency process optimization.