Maximizing ammonium and phosphate recovery from food wastewater and incinerated sewage sludge ash by optimal Mg dose with RSM

Abstract Nitrogen (N) and phosphorus (P) removal and recovery as struvite from various waste streams have drawn much attentions for environmentally friendly and economically competitive fertilizer production. In this study, integrated approach of using food wastewater (FW) and incinerated sewage sludge ash (ISSA) as the alternative N and P sources and optimum Mg dosage were investigated for the first time to achieve maximal nutrient recovery as struvite (MgNH4PO4∙6H2O). Response surface methodology (RSM) successfully established the optimum condition for the maximum recovery of PO43--P (97.7%), NH4+-N (74.8%), and Mg2+ (95.5%) as precipitate at pH 9.63 and molar ratio of PO43--P:NH4+-N:Mg2+ of 1:0.6:1.59. The recovered precipitate mostly consists of struvite (72.6%) and shows high P-bioavailability (98.8%) with very low heavy metals content indicating a high performance fertilizer. Moreover, economic analysis highlights that the struvite production pathway could gain $149.1/m3 of FW to move forwards for economical struvite production.