Effect of Temperature on Phosphorus Release from Waste Activated Sludge Containing Ferric-Phosphate

Abstract

Achieving phosphorus (P) release from waste activated sludge (WAS) containing ferric-phosphate (FePO4) is a crucial step for P recovery. The biological reduction of sulfate to sulfide and Fe3+ to Fe2+ provides potential methods for extracting and reclaiming P. The purpose of this study was to compare the roles of sulfate-reducing bacteria (SRB) and iron-reducing bacteria (IRB) in liberating insoluble P from WAS containing FePO4 at different temperatures. Results showed that the maximum P release (80.3 ± 1.3 mg/L, 45.1%) was achieved at 35°C within 6 days, in which sulfate was reduced to sulfide that then reacted with FePO4 to form FeS. The genus Microbacter acted as SRB increased to 5.2% at 35°C. At 45°C, the highest P release percentage was 36.6%, in which Fe3+ reduced to Fe2+ by IRB facilitated P release. The genus Fonticella and Thiomonas acted as IRB increased to 17.5% and 4.3% at 45°C. The combined process of sulfate reduction and iron reduction holds promise as a novel alternative for P release.

Keywords: Iron-phosphate, Sulfate reduction, Iron reduction, Phosphorus release