Chemical precipitation in the simultaneous removal of NH4−N and PO4−P from wastewaters using industrial waste materials

Thesis event information

Date and time of the thesis defence

Place of the thesis defence

Via remote connections, connection: Zoom: Join URL:

Topic of the dissertation

Chemical precipitation in the simultaneous removal of NH4−N and PO4−P from wastewaters using industrial waste materials

Doctoral candidate

Master of Science Pekka Myllymäki

Faculty and unit

University of Oulu Graduate School, Faculty of Technology, Research Unit of Sustainable Chemistry

Subject of study

Process technology


Professor Ari Väisänen, University of Jyväskylä


Professor Ulla Lassi, University of Oulu

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Nutrient-rich recycled fertilizers from industrial waste materials and side-streams

The use of industrial waste materials as precipitation chemicals in the simultaneous removal of ammonium and phosphate from nutrient-containing wastewaters was studied in this dissertation. The studied waste materials were calcined paper mill sludge, fly ash (alkaline earth metal activated), and calcined dolomite.
Phosphorus and nitrogen compounds are the main nutrients in waste waters that cause algae formation, oxygen depletion and eutrophication in water systems. These nutrients are released into waterways e.g. from agriculture, industry, municipal waste streams and energy production. Most of the industrial waste materials have previously been landfilled, but the revised European Union (EU) waste legislation and circular economy strategy aim to prevent waste generation, improve the recycling of waste materials and encourage the use of various industrial side- and waste-streams.
Ammonium and phosphate removal experiments were started using synthetic wastewater in order to generate experimental comparative data. In the last stage, authentic wastewaters from bio-gasification plant and agricultural sludges were studied. The formed precipitates were characterized in consideration of their suitability as recycled fertilizers. Results indicated that the precipitates contained valuable nutrient-containing compounds, such as monetite, hydroxyapatite, and struvite. Fly ash and dolomite acted well in the removal of ammonium and phosphorus, and calcined paper mill sludge acted well in the removal of phosphorus.
By combining industrial waste materials with nutrient-containing wastewater, a useful recycled fertilizer product, which is also of low environmental impact, can be generated. It is necessary to recycle nutrients in order to prevent eutrophication of water bodies and in order to guarantee the sufficiency of phosphorus minerals.
Last updated: 1.3.2023