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Effect of extra polymeric substance removal on sludge reduction potential of Bacillus licheniformis at its optimised pH condition



The effect of extracellular polymeric substances (EPSs) on the solubilisation of municipal wastewater sludge by protease-secreting bacteria was investigated. The untreated sludge is an environmental menace, so sludge management techniques are introduced to treat and dispose sludge in a proper way. Sludge pretreatment is needed to increase the solubilisation and the efficiency of treatment methods. The present study deals with sludge solubilisation by bacterial enzymatic pretreatment. The EPS present in the sludge was removed by sodium hydroxide and formaldehyde to enhance solubilisation and increase the bacterial enzymatic activity. After the removal of EPS with different normalities of NaOH, there was about 11–18% sludge solubilisation and about 8–16% sludge reduction during bacterial pretreatment. Bacterial enzymatic pretreated sludge was further treated using aerobic digesters. From the results obtained in aerobic digestion, 0.06 N NaOH was chosen as the optimal concentration to remove EPSs.