Two-phase nutrient recovery from livestock wastewaters combining novel membrane technologies

The application of new technologies in the agro-industrial sector is needed to close the loop of the nutrient cycle in the food chain. The aim of this work is to study the feasibility of the combination of two nutrient recovery technologies. In a first step, the novel gas-permeable membrane technology recovers N from the wastewater as an ammonium sulfate solution (a bio-based fertilizer). Secondly, the electrodialytic process recovers P, as an electrolyte solution, from which P can then be precipitated as struvite (a slow-release fertilizer). The process was tested in two different livestock wastewaters: swine manure (SM) and anaerobically digested SM (digestate). Recovery efficiencies for N were 53% for SM and 92% for digestate; for P the efficiencies were 100% and 74% for SM and digestate, respectively. The results showed a great potential of combining these novel membrane technologies in livestock wastewaters, promoting the sustainability of the sector in the realm of the bioeconomy.