Thermal Activation of Peroxymonosulfate for Enhanced Volatile Fatty Acids Production and Phosphorus Release During the Anaerobic Fermentation of Iron-Rich Sludge

Abstract

Anaerobic fermentation (AF) is widely employed to drive the release of phosphorus (P) from iron-rich sludge, although P is often bound to inorganic minerals, impeding its release during AF. Heat-peroxymonosulfate (PMS) pre-treatment is an emerging technology that is increasingly being used during AF for enhanced resource recovery. This study investigated the effects of PMS on P release and the production of volatile fatty acids ( VFAs) during AF. Results indicated that maximum P concentrations were increased from 10.3 ± 0.4 mg/L in PMS-0 to 246.1 ± 1.6 mg/L in the PMS-0.8 group, while the production of VFAs on day 5 increased from 2409.1 ± 30.8 mg COD/L in PMS-0 to 2995.4 ± 86.5 mg COD/L in PMS-0.8. Heat-PMS pre-treatment effectively promoted sludge lysis, providing an abundance of bioavailable substrates for further AF process. Furthermore, the sulfate produced by PMS activation was reduced to S2- by sulfur-reducing bacteria, which reacted with Fe in Fe-P to form FeS, further facilitating the release of P. 16S rRNA gene amplicon revealing a significant increase in the acidogenic bacteria Romboutsia (24.5%) in PMS-0.8. Metagenomic analysis showed that an increase in PMS dosage was detrimental to P release during polyphosphate hydrolysis by polyphosphate-accumulating organisms, while the functional genes involved in S cycling increased, suggesting that sulfate reduction was a critical cause of P release from iron-rich sludge during AF. These results provide important insights for the improvement of P release efficiency and acid production during AF, enhancing the potential for resource recovery from iron-rich sludge.

Keywords: Phosphorus release, Sulfate reduction, Peroxymonosulfate, Iron-rich sludge, Anaerobic fermentation