Abstract
Recycling and recovery of phosphorus will soon be essential to sustain the agriculture industry. Phosphorus can be recovered from wastewater in the form of struvite, a crystalline solid consisting of magnesium ammonium phosphate hexahydrate (MgNH4PO4*6H2O). Struvite precipitation from dairy manure has consistently posed problems for researchers; however, several motivations exist to support further research to develop successful phosphorus recovery techniques. Batch precipitation tests identified high calcium concentration and high ionic strength as the major interfering factors to struvite recovery from anaerobically digested dairy manure. A pretreatment was developed to remove dissolved calcium by chemical precipitation with pH increase. Dilution was explored to increase struvite precipitation potential by lessening ionic strength. The feasibility of struvite recovery from anaerobically digested dairy manure was assessed following calcium removal pretreatment. Ultimately, there still exists at least one major interfering factor to struvite formation from anaerobically digested dairy manure, even after pretreatment for calcium removal.