University of Oulu

Pesonen, J.; Myllymäki, P.; Tuomikoski, S.; Vervecken, G.; Hu, T.; Prokkola, H.; Tynjälä, P.; Lassi, U. Use of Calcined Dolomite as Chemical Precipitant in the Simultaneous Removal of Ammonium and Phosphate from Synthetic Wastewater and from Agricultural Sludge. ChemEngineering 2019, 3, 40. doi:10.3390/chemengineering3020040

Use of calcined dolomite as chemical precipitant in the simultaneous removal of ammonium and phosphate from synthetic wastewater and from agricultural sludge

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Author: Pesonen, Janne1; Myllymäki, Pekka1; Tuomikoski, Sari1;
Organizations: 1Research Unit of Sustainable Chemistry, University of Oulu, P.O. Box 8000, FI-90014 Oulu, Finland
2Life sciences & Chemistry, Thomas More, Geel, 2440 Antwerp, Belgium
3Unit of Applied Chemistry, Kokkola University Consortium Chydenius, University of Jyväskylä,P.O. Box 567, FI-67101 Kokkola
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 7.7 MB)
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Language: English
Published: Multidisciplinary Digital Publishing Institute, 2019
Publish Date: 2019-10-04


Phosphorus as phosphate and nitrogen as ammonium or nitrate are the main nutrients in wastewaters and agricultural sludges. They runoff easily to waterways and cause eutrophication in water bodies. However, ammonium and phosphate could be precipitated simultaneously and used as recycled nutrients. In this research, dolomite calcined at 650 °C, 750 °C, or 950 °C and commercial MgO were used as precipitants in simultaneous phosphate and ammonium removal from synthetic (NH₄)₂HPO₄ solution and agricultural sludge. Calcination at 750 °C was the preferred option as dolomite was decomposed to MgO and CaCO₃ for optimal struvite precipitation. Molar ratios of 1.1–1.6:1–2:2 (Mg:P:N) were employed in the experiments. Very robust ammonium removal was obtained with MgO (57%), dolomite 650 °C and dolomite 750 °C (75%). MgO removed almost all phosphate, while dolomite 650 °C removed 65%, and dolomite 750 °C removed 60% (70% from agricultural sludge). Some part of the phosphate was adsorbed, most likely by CaCO₃, during dolomite precipitation. Struvite was the only identified reaction product in all samples after 24 h of precipitation. Calcined dolomite had great potential in ammonium and phosphate precipitation from both synthetic waters and agricultural sludges and the precipitates could be used as recycled fertilizers.

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Series: ChemEngineering
ISSN: 2305-7084
ISSN-E: 2305-7084
ISSN-L: 2305-7084
Volume: 3
Issue: 2
Article number: 40
DOI: 10.3390/chemengineering3020040
Type of Publication: A1 Journal article – refereed
Field of Science: 218 Environmental engineering
116 Chemical sciences
Funding: This work was done under the auspices of the Waterpro (ERDF project no: A74635, funded by Central Ostrobothnia Regional Council.
Copyright information: © 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (