Ammonium-nitrogen recovery as struvite from swine wastewater using various magnesium sources

Struvite (MgNH4PO4·6H2O) precipitation is widely used for nutrient recovery from swine wastewater. Additional magnesium source is required to produce struvite for nitrogen recovery due to the limited magnesium content in swine wastewater. The present study investigated the optimized condition for treating swine wastewater and producing struvite crystals using swine slurry, commercial MgCl2, and seawater as magnesium sources. The results showed that swine slurry as an alternative source is feasible both technically and economically. The struvite precipitation process using swine slurry at pH 9.0 and [P]0/ [Mg]0/ [N]0 M ratio = 1.2/1.0/1.0 achieved removal efficiencies of 82.7 %, 83.1 %, and 92.7 % for nitrogen, phosphorus, and magnesium, respectively. X-ray diffraction analysis validated the solid product consisted of struvite. Further investigations revealed the harvested precipitate had a struvite content of 72.7 % with low heavy metal impurity, which could be used as fertilizer. Nutrient recovery from swine manure is a future driver for the economic and environmental sustainability of agricultural and wastewater treatment processes.