Insight into the sludge reduction performances by hydrodynamic cavitation

Insight into the sludge reduction performances by hydrodynamic cavitation (HC) were investigated. Mixed liquor suspended sludge (MLSS) and mixed liquor volatile suspended solids (MLVSS) decreased first and then increased as the increase of HC time from 0 to 240 min, and the lowest MLSS was 756.86 mg/L at 120 min. HC treatment promoted the increase in the solute chemical oxygen demand (sCOD) concentration and disintegration degree (DDsCOD) of sludge, and the values of sCOD and DDsCOD at 240 min were 319.66 mg/L and 22.98 %, respectively. The particle sizes at the 10th percentile (d(0.1)), the 50th percentile (d(0.5)) and the 90th percentile (d(0.9)) in particle size distributions decreased from 8.97, 21.10 and 49.10 μm to 0.04, 4.45 and 26.90 μm, respectively. The protein concentration in tightly bound extracellular polymers (TB-EPS) reduced with the increasing HC time from 0 to 240 min, while that in loosely bound EPS (LB-EPS) decreased firstly (during 0–120 min) and then gradually increased (during 120–240 min). As the increase of HC time, tryptophan protein in LB-EPS at 120 min and tyrosine protein in TB-EPS at 240 min disappeared in 3D excitation–emission matrix spectra.