Precipitation of struvite using MgSO₄ solution prepared from sidestream dolomite or fly ash
Pesonen, Janne; Janssens, Fien; Hu, Tao; Lassi, Ulla; Tuomikoski, Sari (2022-12-25)
Pesonen, J., Janssens, F., Hu, T., Lassi, U., & Tuomikoski, S. (2022). Precipitation of struvite using MgSO4 solution prepared from sidestream dolomite or fly ash. Heliyon, 8(12), e12580. https://doi.org/10.1016/j.heliyon.2022.e12580
© 2022 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/bync-nd/4.0/).
https://creativecommons.org/licenses/by-nc-nd/4.0/
https://urn.fi/URN:NBN:fi-fe2023053049970
Tiivistelmä
Abstract
Struvite (NH₄MgPO₄∗6H₂O) is a slow-release fertilizer produced from phosphorus and nitrogen-containing wastewater in the presence of Mg salts. Commercial Mg salts are the single most significant cost of struvite precipitation. In this study, H₂SO₄ formed as an industrial sidestream was used to prepare MgSO₄ solution from waste dolomite (DOL) and fly ash (FA). MgSO₄ solution was then used to precipitate struvite from a synthetic (NH₄)₂HPO₄ solution and from actual industrial process waters. The best results were obtained with real process waters where over 99% of phosphate and about 80% ammonium removals were achieved with both MgSO4 solutions after 30 min of reaction time. A higher molar ratio between Mg and P improved the phosphate removal efficiency, especially with DOL-based MgSO4 solutions; however, it had no practical effect on ammonium removal. The struvite content of precipitates was 75.49% with an FA-based chemical and 60.93% with a DOL-based chemical; other valuable nutrients (Ca, K, S, Fe, Mn, and Cl) were captured in the precipitates. The results indicate that both sidestream-based reagents perform well in struvite precipitation and that the formed precipitates could be used as fertilizers.
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