Enhanced volatile fatty acids production from waste activated sludge with synchronous phosphorus fixation and pathogens inactivation by calcium hypochlorite stimulation

An efficient approach for synchronous volatile fatty acids (VFAs) promotion, phosphorus fixation and pathogens inactivation during waste activated sludge (WAS) anaerobic fermentation was achieved with optimal calcium hypochlorite (Ca(ClO) 2 ) stimulation. The maximal VFAs were 3.6 folds of control in reactors with 0.01 g Ca(ClO) 2 /g TSS addition. The low dosage of Ca(ClO) 2 enhanced WAS solubilization and hydrolysis by disrupting the extracellular polymeric substance (EPS) effectively. Sufficient substrates for fermentative bacteria were thereby provided with the maintenance of acceptable microbial activity and viability. However, high dosage of Ca(ClO) 2 deteriorated the performance of anaerobic fermentation due to its strong oxidative ability, resulting in cell lysis greatly. Moreover, the largely released phosphorus during WAS fermentation was effectively precipitated and removed by the combination of Ca 2+ at 0.01 g Ca(ClO) 2 /g TSS dosage. In addition, Ca(ClO) 2 had distinguished effects on pathogens inactivation. The simultaneous phosphorus fixation and pathogens reduction during VFAs production increased the utilization value of fermentation liquid and benefitted the further disposal of fermented sludge.