Promotion of short-chain fatty acids production and fermented sludge properties via persulfate treatments with different activators: Performance and mechanisms

This study explored the influences of peroxydisulfate (PDS) and peroxymonosulfate (PMS) activated with different catalysts on the anaerobic fermentation of waste activated sludge (WAS). All the treatments were effective in promoting short-chain fatty acids (SCFAs) production, particularly acetic acid, in the order of PMS/MnO₂ > PMS/Zn > PDS/Zn > PMS/Fe > PDS/Fe > PDS/MnO₂. Mechanistic investigations demonstrated that WAS disintegration was intensely induced by the free radicals (i.e., SO₄^[rad]− and [rad]OH) generated in PDS and PMS treating reactors. It significantly promoted the solubilization and hydrolysis processes and thereby provided sufficient bioavailable substrates for further acidogenic metabolisms. Additionally, it enlarged the abundance of functional bacteria responsible for SCFAs production. The simultaneous promotion of bioavailable substrates and fermentative microorganisms markedly contributed to the SCFAs enhancement. Moreover, the dewaterability and stabilization of fermented sludge were both improved with the PDS and PMS treatments, which were beneficial to the final disposal of WAS.