Optimizing conditions for struvite precipitation as byproduct in fugate

abstract

English

Fugate is a by-product of anaerobic digestion in biogas plants and it can be defined as a liquid fraction of digestate, that contains high ammonia nitrogen content. The use of fugate as a fertilizer in agriculture is limited due to its rapid release of ammonia nitrogen, which causes high nitrogen concentrations in soil and groundwater. Nowadays, there are many well-known separation procedures for these contaminants, but it is more than desirable to deal with the conversion of the separated substances into a further usable product. Using crystallization, separated ammonia nitrogen can be converted into struvite, which is widely used as a gradual release fertilizer in agriculture. This paper will deal with the chemical description and precipitation problems of struvite. In the first part, the precipitation curves of all substances that can form during precipitation were theoretically described. Furthermore, laboratory experiments were designed to determine the optimum pH and the Mg:P:N ratio for struvite precipitation. Finding the optimum conditions then allowed for experiments to be carried out with real fugate samples. The results show that converting contaminants into a usable product is realistic and effective if the correct precipitation conditions (pH, Mg:P:N ratio, temperature) are maintained. A semi-operational technology with several different types of precipitation reactors is currently being proposed. After experimentally verifying the struvite precipitation efficiency in individual reactors, the best one will be selected, and the technology will be installed for full operation at the biogas plant.

Fugate, Ammonia nitrogen, Struvite , Precipitation

MAYEROVÁ, K.; KALIVODA, J.; LINDOVSKÝ, J.; KRIŠTOF, O.

26. 8. 2024

Praha

1

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