DOI: 10.5061/dryad.2547d7x2d
title: The potential of wastewater treatment on carbon storage through ocean alkalinity enhancement

description: 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 over 10 mmol kg−1 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 Tg CO2 per year globally, with notable potential in the 20°N to 60°N
 region.
description: # **The potential of wastewater treatment on carbon storage through ocean
 alkalinity enhancement**
 [https://doi.org/10.5061/dryad.2547d7x2d](https://doi.org/10.5061/dryad.2547d7x2d) **Description of the data and file structure** HydroWASTE (Macedo et al., 2022) has supplied a spatially explicit global database of wastewater treatment plants (WWTPs), with 0.14 km3 day−1 of discharge from the 9,480 WWTPs located within 10 km of the ocean and with outfalls in the sea. Salinity, dissolved inorganic carbon, and total alkalinity levels in seawater near the WWTP outlets were from the Ocean Carbon and Acidification Data System (OCADS) (Jiang et al., 2023). Lehmann et al., 2023 and Cai et al., 2008 reported total alkalinities in rivers across latitudes. | \*\* variables\*\* | **units** | **description** | | :--------------------------------- | :----------------------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | WASTE\_ID | categorical | ID of wastewater treatment plant (WWTP) in HydroWASTE | | SOURCE | categorical | National/regional dataset: 1 = Europe; 2 = United States; 3 = Brazil; 4 = Mexico; 5 = China; 6 = Canada; 7 = Australia; 8 = South Africa; 9 = India; 10 = New Zealand; 11 = Peru; 15 = South Korea; 13 = Japan; 14 = United Kingdom; 12 = Remaining Countries | | ORG\_ID | categorical | ID from national/regional dataset | | WWTP\_NAME | categorical | Name of the WWTP from the national/regional dataset (replacing with "n/a" if the information is not reported) | | COUNTRY | categorical | Country in which WWTP is located | | CNTRY\_ISO | categorical | Country ISO | | LAT\_WWTP | degrees | Latitude of reported WWTP location | | LON\_WWTP | degrees | Longitude of reported WWTP location | | LAT\_OUT | degrees | Latitude of the estimated outfall location | | LON\_OUT | degrees | Longitude of the estimated outfall location | | Salinity | psu | Salinity in  seawater near the WWTP outlets | | water\_temp. | ℃ | Water temperature in  seawater near the WWTP outlets | | Alk\_OUT\_seawater | 10^-6 mol kg^-1 | Total alkalinity in  seawater near the WWTP outlets | | DIC\_out\_seawater | 10^-6 mol kg^-1 | Concentration of dissolved inorganic carbon in  seawater near the WWTP outlets | | WASTE\_DIS | m^3 day^-1 | Treated wastewater discharged by the WWTP | | k\_sp\_diluted water | mol kg^-1 | Apparent solubility product of aragonite in diluted seawater with 90 wt% treated wastewater | | river\_alkalinity across latitudes | 10^-6 mol kg^-1 | Averaged value of total alkalinity in rivers in regions at the same latitude as WWTPs | | error\_river\_alkalinity | 10^-6 mol kg^-1 | Standard deviation of total alkalinity in rivers in regions at the same latitude as WWTPs | | waste\_Alk\_add | 10^-6 mol kg^-1 | Artifical alkalinity addition of  the discharged wastewater from WWTP | | error\_waste\_Alk\_add | 10^-6 mol kg^-1 | Uncertainty in the estimation of artificial alkalinity addition | | Alk\_WASTE | t co2 per year per plant | Carbon sequestration potential of the WWTP | | error\_Alk\_WASTE | t co2 per year per plant | Uncertainty in the estimation of carbon sequestration potential | **Access information** Data was derived from the following sources: * Jiang, L. et al. Global Surface Ocean Acidification Indicators From 1750 to 2100. J. Adv. Model. *Earth Syst.* **15**, (2023). * Macedo, H. E. *et al.* Distribution and characteristics of wastewater treatment plants within the global river network. *Earth Syst. Sci. Data* **14**, 559–577 (2022). * Lehmann, N. et al. Alkalinity responses to climate warming destabilise the Earth's thermostat. *Nat. Commun.* **14**, 1648 (2023). * Cai, W.-J., Guo, X., Chen, C.-T. A., Dai, M., Zhang, L., Zhai, W., Lohrenz, S. E., Yin, K., Harrison, P. J. & Wang, Y.  A comparative overview of weathering intensity and HCO3− flux in the world's major rivers with emphasis on the Changjiang, Huanghe, Zhujiang (Pearl) and Mississippi Rivers. *Cont. Shelf Res.***28**, 1538–1549 (2008).