Effect of Phenolic Organics on the Precipitation of Struvite from Simulated Dairy Wastewater

The production of struvite (MgNH4PO4·6H2O) from dairy lagoon wastewater (DW) improves phosphorus (P) resource sustainability and reduces the rate of deposition of P into surface waters. Struvite formation can be hindered by dissolved organic matter (DOM) and calcium (Ca), but the prevalence of the phenolic functional group (R-OH) in DW DOM may counteract any limiting effects. A constant composition reactor was used to determine the effect of R-OH on the precipitation of struvite from simulated DW in the presence of Ca, with phenol (Ph) as a model R-OH. The presence of Ph increased the struvite precipitation rate relative to those of Ca, Ph, blank (no Ca or Ph), and Ca treatments (51.3, 30.5, 5.8, and 2.7 μmol of struvite min–1, respectively). Solid analysis showed that Ph limited the struvite morphology deformation caused by Ca and Ca mineral coprecipitation. Coprecipitation with Ca–P minerals with or without Ph did not significantly change the thermal properties of struvite, with the thermogravimetric mass loss associated with ammonia gas and water vapor emissions occurring at 80–160 °C. The observed effects of Ph on struvite formation suggest a beneficial contribution of dissolved low-molecular weight organics such as R-OH to improved recovery of struvite from DW.