The dual role of potassium ferrate in promoting primary sludge hydrolysis and acidogenesis in anaerobic fermentation

Potassium ferrate (PF), a green disinfectant has been widely used in drinking water disinfection and has drawn immense attention for its application in sludge treatment. This research study has investigated the effects of PF on the hydrolysis and acidification of primary sludge (PS) to promote the short chain fatty acids (SCFAs) recovery, while achieving solid waste treatment and carbon emission reduction. The results showed that PF could effectively promote the accumulation of SCFAs, and maximum SCFAs yield of 4686.56 mg COD/L was achieved by PF assisted PS fermentation at a PF dosage of 0.4 g/g VSS, which was 2.05 times higher than the control. Substance transformation and enzyme activity analysis indicated that PF significantly promoted the release and hydrolysis of insoluble organic matters from PS through chemical oxidation and alkaline hydrolysis. Furthermore, high doses of PF could also inhibit the growth of methanogens and alter the dominant fermentation flora responsible for SCFAs production. Under the influence of high-dose PF, the foremost acidogenic bacteria were shifted into Trichococcus, Enterococcus, Streptococcus and Gallicola, which might be selectively enriched under the stress of residual Fe (Ⅲ) in the system. The PS fermentation liquid produced after PF pretreatment exhibited a higher C/N ratio and lower phosphorus concentration, which enhanced its suitability as carbon sources for denitrification in WWTPs. This study offered an environmentally friendly method for recovering SCFAs from PS and provided a viable approach to addressing the issue of carbon source shortage in wastewater treatment processes.