A techno-economic analysis of a co-located wastewater treatment and hydrogen facility

Hydrogen is expected to play a significant role as a low-carbon fuel and energy carrier in the net-zero transition, but the associated infrastructure is undeveloped. Wastewater treatment is energy intensive and is often named specifically in emissions and energy reduction discussions. Electrolytic hydrogen production creates by-product oxygen which can improve the efficiency and performance of the wastewater treatment process during the aeration stage. This study analyses a co-located wastewater treatment plant and hydrogen facility and evaluates the techno-economic feasibility of the combination. The analysis is conducted as a case study of Northern Ireland Water's wastewater treatment network by applying an uplift model for enriched oxygen in wastewater treatment plants using industry standard performance parameters. The wastewater treatment network used 93.33 GWh of electrical energy in 2019, accounting for 1.21% of total regional usage. Whole-network analysis of the treatment plants under a hub-and-spoke oxygen distribution model showed a tension between locating for maximal network benefit and locating for optimal on-site benefit. Concentrated oxygen injection could significantly increase the efficiency and throughput of the water treatment process, but this study shows that the sum value of tangible and intangible benefits is expected to be less than 1% of the market value of the oxygen required. It is concluded that by-product oxygen could provide the necessary concentrated oxygen instead, either viewed as acting to subsidise the cost of hydrogen production or as an energy-recovery method that returns on the order of 0.5%–2% of the energy required to produce hydrogen.