Enhancing concurrent production of volatile fatty acids and phosphorus minerals from waste activated sludge via magnesium ferrate pre-oxidation

This study investigated the strategy of magnesium ferrate (MF) pre-oxidation to enhance acidogenic fermentation of waste activated sludge (WAS), targeting the simultaneous production of volatile fatty acids (VFAs) and phosphorus-minerals (struvite and vivianite). Results showed that such fermentation produced a high-value liquid within four days, achieving a peak VFA content of 241 ± 4 mg COD/ g VS_feed, ammonia nitrogen levels below 350 mg/L of and PO₄³-P under 3 mg/L. Further investigation revealed that the MF pre-oxidation raised the pH, enhanced key hydrolases activity, enriched acidogens and iron-reducing bacteria for driving the concurrent production of VFAs and phosphorus-minerals. The MF pre-oxidation promoted VFAs and phosphorus-minerals formation by enhancing the cooperation among the hydrolyzing bacteria of Acinetobacter and Proteocatella, acidogens of Fusibacter and Tissierella_Soehngenia, and iron-reducing bacteria of Dechloromonas and Thauera. This study provided an effective strategy for realizing concurrent production of high-purity VFAs along with struvite and vivianite from WAS.