Nitrogen recovery from pig slurry by struvite precipitation using a low-cost magnesium oxide

Abstract Ammonia nitrogen management is a recurrent problem in intensive livestock areas. Struvite precipitation stands as mature technology to recover ammonia and prevent associated environmental problems. However, the feasibility of struvite from pig manure limited by reagents cost. This research aimed optimise formulation stabilizing agent (SA) synthesised using an industrial low-grade MgO by-product (LG-MgO) phosphoric acid for efficient TAN recovery via precipitation. Experimental results showed that H3PO4/LG-MgO ratio controls magnesium phosphate mineral phase SA (bobierrite and/or newberyite). Newberyite-rich highest removal efficiency (66–73%) compared formed mixture newberyite bobierrite (51–59%) (26%). Particle size reduction LG-MgO did not improve SA's efficiency, although XRD patterns precipitates experiments contained some unreacted newberyite. The economic analysis higher reactivity formulated ratios compensated reagent costs. with 0.98 most economical treatment cost, which was estimated at 7.5 € per kg manure. Finally, optimum successfully 200-L pilot plant, capacity only 10% lower than one lab-scale.