Integrating wet oxidation and struvite precipitation for sewage sludge treatment and phosphorus recovery

In this study, wet oxidation of sewage sludge and struvite-precipitation processes were integrated to safely manage sludge and to recover organic acids and phosphorus. To understand this process integration, the effects of temperature, treatment time, and sludge concentration during wet oxidation, and pH and magnesium dosage during struvite precipitation on total suspended solids (TSS), volatile suspended solids (VSS), organic acids production, and phosphorus recovery were investigated. The results showed that TSS and VSS destruction, organic acids production, and phosphorus recovery from sludge into the liquid phase are more sensitive to temperature and time than sludge concentration during wet oxidation. These are novel findings of this work. Furthermore, pH during struvite precipitation had a strong effect on phosphorus recovery. Wet-oxidised sludge was mainly converted to acetic acid, and its concentration increased with increasing temperature and time. These results may be used for optimised operation and revenue generation from wastewater treatment processes when integrated with wet oxidation and struvite precipitation.