The potential of wastewater treatment on carbon storage through ocean alkalinity enhancement

Ocean alkalinity enhancement (OAE) implemented through wastewater treatment plants increases the alkalinity of the effluents and discharges them into the ocean, referred to as wastewater-based OAE. However, the alkalization capability and its carbon storage stability when adding alkaline minerals to wastewater treatment are uncertain. In this study, total alkalinity was enhanced to more than 10 millimoles per kilogram and phosphate removal was improved when we added olivine to wastewater in a laboratory setting. The alkalization rate by olivine dissolution in aerobically treated wastewater was 20 times higher than in seawater. We estimated the potential of carbon sequestration through wastewater-based OAE to be 18.8 ± 6.0 teragrams of CO₂ per year globally, with notable potential in the 20°N to 60°N region.