Enhancing phosphorus release from waste activated sludge by combining high-voltage pulsed discharge pretreatment with anaerobic fermentation

The effect of high-voltage pulsed discharge (HVPD) pretreatment on waste activated sludge (WAS) for phosphorus (P) release enhancement via anaerobic fermentation (AF) was studied. Batch tests were performed to investigate the P release via HVPD pretreatment and AF. The P release could be enhanced by a 26.7% soluble ortho-P [SOP_(L)] concentration increase via HVPD + AF compared with the control sample (AF of WAS without pretreatment). The HVPD and AF contributed 42.2% and 57.8% to the total SOP_(L) increase, respectively. The P speciation analyzed using the Standards, Measurements, and Testing extraction protocol indicates that the decrease of non-apatite inorganic P (NAIP) in the solid phase is consistent with the increase of SOP_(L) in the liquid phase and the release of poly-P from WAS could be enhanced due to the destruction of sludge flocs by HVPD. In addition, removal rates of 23.8% of total suspended solids (TSS) and 34.3% of volatile suspended solids (VSS) were calculated for the HVPD-pretreated solid phase, which suggests that the soluble organics production and WAS reduction were also enhanced via HVPD + AF. The results reveal that HVPD pretreatment is a promising method for the recovery of P from WAS and WAS reduction.