Enhanced bioproduction of short-chain fatty acids from waste activated sludge by potassium ferrate pretreatment

Recently, bioproduction of short-chain fatty acids (SCFA) from waste activated sludge (WAS) has attracted much attention. Many pretreatment methods were investigated to improve the hydrolysis efficiency of WAS. However, studies on sludge pretreatment employing ferrate (VI) remain limited. Therefore, this literature explored how the potassium ferrate affects the SCFA production as well as the underlying correlation between the microbial community and the system performance. It was found that the ferrate pretreatment promoted the SCFA production significantly after 8 days' digestion from 475 mg COD/L of the control to 2835 mg COD/L at a dosage of 0.9 g/g. The analysis of extracellular polymeric substance (EPS) showed that the extracted EPS had a positive linear relationship with the final SCFA production, which indicated that the extracted EPS could be adopted as an excellent indicator to reveal the pretreatment effect of this method. The concentrations of protein and carbohydrate both showed uptrends with the increasing dosage of potassium ferrate, whereas it imposed a negative impact on the phosphate concentration, which could be explained by precipitation of Fe ion and phosphate. Terminal restriction fragment length polymorphism (T-RFLP) analysis showed that the biodiversity and population distribution evenness were reduced markedly and it further indicated that ferrate pretreatment enhanced the community function by giving rise to acid-producing bacteria, which was in accord with the observed SCFA yield.