Effect of sonically induced deflocculation on the efficiency of ozone mediated partial sludge disintegration for improved production of biogas

• Phase separated sono-ozone pretreatment was introduced as an innovative approach.
• 76.4 kJ/kg TS of ultrasonic specific energy disrupted flocs efficiently.
• 0.0011 mg O3/mg SS of ozone dosage enabled cell lysis effectively.
• Kinetic parameter deliberates the efficient sludge disintegration rate.
• Biogas production was superior in sonic mediated ozone pretreated sludge.

In this study, ultrasonication was used for sludge deflocculation, followed by cell disintegration using ozone. The effect of this phase separated sono-ozone pretreatment is evaluated based on extra polymeric substances release, deoxyribonucleic acid (DNA) in the medium, solubilization of intra cellular components and suspended solids (SS) reduction. Ultrasonically induced deflocculation was optimized at an energy dosage of 76.4 (log 1.88) kJ/kg TS. During cell disintegration (ozone dosage 0.0011 mg O3/mg SS), chemical oxygen demand solubilization (COD) and SS reduction of sonic mediated ozone pretreated sludge were 25.4% and 17.8% comparatively higher than ozone pretreated sludge, respectively. Further, biogas production potential of control (raw), flocculated (ozone pretreated), and deflocculated (sonic mediated ozone pretreated) sludges were observed to be 0.202, 0.535 and 0.637 L/(g VS), respectively. Thus, the phase separated pretreatment at lower ultrasonic specific energy and low dose ozone proved to enhance the anaerobic biodegradability efficiently.