As part of the digestate valorisation route (biogas route) of the Waste4Soil project, IRTA has designed and constructed a pilot plant for the recovery of ammonia nitrogen from the different digestates produced by LEITAT, which combines microbial electrolysis cells (MECs) and hydrophobic membranes. The scaling up of this type of system is still a challenge in the field of waste (water) treatment with a high organic content, so the construction of this pilot plant marks an item in this regard.
The pilot plant consists of 3 MECs in series coupled to 2 hydrophobic membrane modules. A refrigerated tank to avoid substrate degradation, and an acid tank and containers for catholyte and effluent collection are integrated into the system. The pilot plant is equipped with pH probes and level sensors, and it is programmed to operate automatically in semi-continuous mode with a feeding rate of about 1.5 L digestate/day.
The use of this technology will allow to recover the ammonia nitrogen present in the different residues proposed in the Living Lab of Catalonia in the form of ammonium sulphate ((NH₄)₂SO₄), an inorganic fertilizer.
The plant operation has recently started and tangible results are expected in mid-2025.
