Contexte

In this context, within the K-EcoFeRtilizer project, the struvite-K precipitation process is intended to be applied to the treatment of effluents from nitrification-denitrification (NDN) systems, which have a low N concentration but a significant K content (a major nutrient in relation to N and P), as well as a rather low buffer capacity compared to the initial slurry (due to biological treatment). Precipitation also produces treated water with reduced salinity (and a corrected P and K composition), suitable for reuse for irrigation of adjacent crops.
In the field of pig slurry liquid fraction treatment, the integration of biological N removal (BNR) with the recovery of MPP-type phosphoric precipitates (containing P and K) has proven to be technically feasible. In order to study it, a series of precipitation tests were carried out on a laboratory scale. In these trials, synthetic media or denitrified effluent and purified sludge obtained at the outlet of the Mas Monellots NDN bioreactor were used.
This project involved the design, construction and installation in situ of a prototype crystalliser at the Mas Monellots farm, owned by Granges Terragrisa, for the recovery of struvite-K from the denitrified effluent from the NDN reactor. The struvite-K fertiliser obtained was applied in field trials carried out on experimental crops and/or crops of the Sant Martí de Tous Agricultural Cooperative. With the application of struvite-K or mixtures of this product with compost and sludge as fertiliser for a spring barley crop, similar or slightly higher yields are achieved than with the reference Mineral treatment.