Improving the amenability of municipal waste activated sludge for biological pretreatment by phase-separated sludge disintegration method

• 0.05 g/g SS of citric acid dosage disrupt flocs & enhances sludge enzyme activity.
• Suspended solids reduction was superior in deflocculated sludge of about 16.2%.
• Kinetic parameters show that rate was 4 times higher in deflocculated sludge.
• Citric acid mediated bacterial pretreatment enhances biogas production potential.
• Biogas production was higher in deflocculated sludge than the control.

The significance of citric acid, a cation binding agent, was investigated for the exclusion of extracellular polymeric substance (EPS) from waste activated sludge (WAS) and anaerobic biodegradability following enzymatic bacterial pretreatment. EPS was removed with 0.05 g/g SS of citric acid. The results of pretreatment found that the suspended solids reduction and chemical oxygen demand solubilisation were 21.4% and 16.2% for deflocculated-bacterially pretreated sludge, 14.28% and 10.0% for flocculated sludge (without EPS removal and bacterially pretreated) and 8.5% and 6.5% for control sludge (raw sludge), respectively. Further assessing anaerobic biodegradability, the biogas yield potential of deflocculated and bacterially pretreated, flocculated, and control sludges were found to be 0.455 L/(g VS), 0.343 L/(g VS), and 0.209 L/(g VS), respectively. Thus, phase-separated disintegration enhanced anaerobic biodegradability efficiently.

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