Precipitating phosphorus as struvite from anaerobically-digested dairy manure

Midwestern US agroecosystems suffer greatly due to excess phosphorus (P) in runoff from land-applied manure. Precipitating P as struvite would remove it the manure stream, allowing efficient storage, transportation, and use slow-release fertilizer. To achieve precipitation, organic solids calcium (Ca) must first be removed This study assessed precipitation dairy using a novel processing pipeline: diluting manure, then acidifying treating with Ca chelator, followed by simultaneously flocculating solids, finally raising pH precipitate struvite. The manipulations were determined through chemical equilibrium modeling Visual MINTEQ. Oxalic acid was most chelator tested, reducing soluble 200 mg/L below 40 while leaving magnesium concentrations unaffected. An anionic low-weight flocculant effective at removing 1.2% 0.5% diluted (4:1) process train comprising oxalic flocculant, reduced dissolved 93% producing an estimated yield equivalent 72% of total initially present Results this show that simple one-step removal can efficiency comparable multi-step methods.