The EPS present in the sludge was removed by sodium hydroxide and formaldehyde to enhance solubilisation and increase the bacterial enzymatic activity. The present study deals with sludge solubilisation by bacterial enzymatic pretreatment. Sludge pretreatment is needed to increase the solubilisation and the efficiency of treatment methods. The untreated sludge is an environmental menace, so sludge management techniques are introduced to treat and dispose sludge in a proper way. The effect of extracellular polymeric substances (EPSs) on the solubilisation of municipal wastewater sludge by protease-secreting bacteria was investigated. This value was higher compared to the biodegradability increase induced by individual ALK pre-treatment (5.7%) or individual ULS pre-treatment (20.7%) under the same conditions applied. ALK+ULS pre-treatment resulted in 37.8% biodegradability increase compared to the untreated sludge. Sludge anaerobic biodegradability was significantly enhanced with the simultaneous application of ALK+ULS pre-treatment. Excitation emission matrix fluorescence spectroscopy analysis identified soluble microbial product-like and humic acid-like matters as the main solubilization products. Organics with molecular weight larger than 300kDa increased from 7.8% to 60%, 16% and 42.3% after ULS, ALK and ALK+ULS treatment, respectively. ![]() ![]() Organics with molecular weight around 5.6kDa were solubilized because of the synergistic effect of ultrasound and alkali. Soluble chemical oxygen demand (SCOD) increased from 1200 to 11,000mg/L after such treatment. This work provides insights on the solubilization products after a simultaneous combination of alkaline and ultrasonic (ALK+ULS) pre-treatment of sewage sludge.
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