Energy shifting in wastewater treatment using compressed oxygen from integrated hydrogen production

Integrating renewable hydrogen production via electrolysis with wastewater treatment is an opportunity to manage environmental resources more sustainably while providing a pathway to producing sustainable hydrogen at industrial scale. The synergies of integrating oxygen production from water electrolysis and oxygen use in wastewater treatment benefit both hydrogen production and wastewater industries. However, the understanding of the most suitable integrated process configuration and scale of renewable equipment is not known. A novel energy shifting process is proposed here using compressed and stored oxygen produced by water electrolysis and used in the activated sludge process, replacing traditional aeration in the wastewater treatment plant and eliminating the high energy consuming blowers supplying air to submerged fine bubble diffusers. In the proposed energy shifting process, excess oxygen produced by water electrolysis at times of peak renewable electricity production is stored and used for wastewater treatment at times of peak oxygen demand. Wastewater treatment data from the activated sludge process was used to calculate oxygen demand in 1-h intervals over a 24-h period, and the system response of the integrated plant was simulated at hourly intervals and equipment size determined according to an optimisation algorithm that balances oxygen and electricity supply and demand over a 24-h period. Sensitivity analysis of operational parameters is assessed and the case for replacing traditional WWTP aeration with newer technologies is quantified using a high efficiency oxygen transfer system such as a Speece cone as an example that is shown to be a prerequisite for the feasibility of the process. The results produced by this study provide valuable information to the hydrogen and wastewater industries on how an integrated plant could be configured. Besides the environmental advantages of sustainably produced hydrogen, using oxygen as a biochemical energy storage medium in this configuration means WWTP powered from renewable electricity becomes more viable reducing the industries reliance on fossil fuels.