Low temperature assisting potassium ferrate treatment to enhance short-chain fatty acids production from waste activated sludge

To recover resource from waste activated sludge (WAS) presents great roles on developing carbon-neutral operation of wastewater treatment plants. This study was conducted to evaluate SCFAs production potential from anaerobic fermentation of WAS by a novel strategy, i.e., low temperature assisting potassium ferrate (PF) treatment. Results showed that the maximal SCFAs production reached 217 mg chemical oxygen demand (COD)/ g volatile suspended solids (VSS) with the shortened fermentation time of six days, and the sum of acetic and propionic acids reached 128 mg COD/g VSS. Meanwhile, the potentially recovered carbon source, in terms of SCFAs, soluble polysaccharides and proteins, reached 437 mg COD/g VSS. The mechanism study indicated that both solubilization and hydrolysis steps were accelerated, supporting by the highest accumulations of soluble organics and ammonia nitrogen, while methanogenesis step was inhibited, supporting by the lowest methane production. In addition, it is noted that low temperature treatment facilitated organics release from extracellular polymeric substance (EPSs), with the removal efficiencies of 51.1% for polysaccharides and 44.3% for proteins, while PF facilitated cell lysis. Interestingly, compared with low temperature followed by PF treatment, PF followed by low temperature treatment performed better on facilitating disintegration of both cells and EPSs, with the highest soluble polysaccharides and proteins of 439 and 1845 mg COD/L. Also, the acid-producing bacteria was greatly enriched, with total percentage of 29.5%. The findings of this study may provide some potential solutions for SCFAs production enhancement from WAS.