Effect of citric acid induced deflocculation on the ultrasonic pretreatment efficiency of dairy waste activated sludge

• 0.05 g/g SS of citric acid solubilized flocs efficiently.
• The phase separation disintegration is a new approach.
• Kinetic parameters confers the efficient sludge degradation rate.
• Biogas production was more at deflocculated-171.9 kJ/kg TS (specific energy).
• Ultrasonic pretreatment enhanced the anaerobic biodegradability.

In this investigation, the application of citric acid was explored for the removal of extracellular polymeric substance (EPS) from waste activated sludge (WAS), followed by ultrasonic pretreatment, which enhanced the subsequent anaerobic biodegradability. EPS was removed with 0.05 g/g SS of citric acid. The chemical oxygen demand (COD) solubilization and suspended solids (SS) reduction that occurred for specific energy input of 171.9 kJ/kg TS, in deflocculated (EPS removed and ultrasonically pretreated) sludges were found to be 22.70% and 20.28% and was comparatively higher, than the flocculated (with EPS and ultrasonically pretreated). The biogas yield potential of flocculated and deflocculated sludges (specific energy input – 171.9 kJ/kg TS) was found to be 0.212 L/(g VS) and 0.435 L/(g VS), respectively. Accordingly, the deflocculation and ultrasonic pretreatment improved the anaerobic biodegradability efficiently. Thus, this chemo mediated sonic pretreatment is an effective method for enhancing biodegradability and improving clean energy generation from WAS.