In the BioP-Rec project, funded by the Ministry of the Environment and led by Prizztech, Huittinen Treatment Plant, and Berner Chemicals, a pilot-scale struvite crystallization system has been acquired for the Huittinen Treatment Plant. The system operates in batch mode and can process 1000 L of liquid fraction suitable for struvite crystallization at a time. Suitable liquid fractions contain a sufficient amount of soluble phosphorus (over 70 mg/L).
The system has been tested with return sludge from the biological phosphorus removal process at the Huittinen Treatment Plant, successfully crystallizing small amounts of struvite. Struvite is an excellent fertilizer as its nutrients are released slowly into the soil, making them readily available for plants in a controlled manner.
The system consists of an aging tank, an IBC container, a sand filter, and a crystallizer. In the aging tank, wastewater sludge is aged to release phosphorus from microbes back into the liquid fraction. In the IBC container, polymer can be added to settle the sludge and separate the liquid fraction. The sand filter further purifies the liquid fraction. In the crystallizer, struvite crystallizes under the influence of additives, including magnesium products from Berner Chemicals, and through mixing.
Anna Halinen, CEO of Huittinen Treatment Plant, states: “The project is important for Huittinen Treatment Plant in terms of promoting nutrient recycling and ensuring chemical supply security. A small treatment plant usually doesn’t have the means to undertake such projects alone, so collaboration with companies and Prizztech is an essential part of advancing these efforts.”
