Abstract
Experimental analysis of citric acid and bacterial pretreatment on waste activated sludge (WAS) was performed in a semi-continuous anaerobic reactor for assessing the sludge reduction. The sludge pretreatment was carried out by deflocculating the WAS using 50mM/L citric acid and subjecting to bacterial disintegration using 2g dry cell weight/L of Bacillus licheniformis. The pretreatment resulted in a COD solubilization of about 40%. Anaerobic digestion (AD) of pretreated sludge was carried out in a 3.5 L semi-continuous anaerobic reactor. The AD results reveal that an organic loading rate (OLR) of 1g/Ld operated at 15d hydraulic retention time was preferably the pertinent OLR for the efficient digestion. AD of pretreated sludge resulted in 43% of suspended solids reduction and 48% of volatile solids (VS) reduction, respectively, with biogas yield of 189.61mL/g VS added.