Simultaneous enhancing phosphorus recovery and volatile fatty acids production during anaerobic fermentation of sewage sludge with peroxydisulfate pre-oxidation

Phosphorus release and sludge hydrolysis are the keys for phosphorus and carbon recovery from sewage sludge via anaerobic process. In this study, iron-rich sludge (a common phosphorus-rich sewage sludge) was pre oxidized by heat-activated peroxydisulfate (PDS) to enhance volatile fatty acids (VFAs) production and ironbound phosphorus (Fe-P) release during anaerobic fermentation (AF). With low-dosage PDS pre-oxidation (33.75 mg/g total solids), the concentration of recoverable phosphorus increased by 49.3% than that noted in control along with enhanced VFAs production after 4 days. This is mainly because PDS oxidation not only effectively disintegrated sludge, but also generated sulfate simultaneously. Sludge disintegration enhanced organic matter hydrolysis, promoting VFAs yield, while sulfate was reduced to sulfide during AF and precipitated with iron, leading to Fe-P release. The application of PDS pre-oxidation on iron-rich sludge could not only improve the resourcefulness of sludge but also reduce secondary pollution (sulfate or hydrogen sulfide).

Automated summary

This study found that pre-oxidation of iron-rich sludge with heat-activated peroxydisulfate (PDS) can enhance the production of volatile fatty acids (VFAs) and the release of iron-bound phosphorus (Fe-P), thereby increasing the concentration of recoverable phosphorus. PDS oxidation effectively disintegrated the sludge and generated sulfate simultaneously. The disintegration of sludge promoted the hydrolysis of organic matter, leading to increased VFAs yield, while the sulfate was reduced to sulfide during anaerobic fermentation (AF) and precipitated with iron to release Fe-P.