STEAM-EXPLOSION PRE-TREATMENT FOR ENHANCING ANAEROBIC DIGESTION OF MUNICIPAL WASTEWATER SLUDGE
Abstract:This study evaluated the use of steam explosion as a pre-treatment for municipal wastewater treatment sludges and biosolids as a technique for enhancing biogas generation during anaerobic digestion. Samples of dewatered anaerobic digester effluent (biosolids) and a mixture of thickened waste activated sludge (TWAS) and biosolids were steam exploded under differing levels of intensity in this study. The results indicate that steam explosion can solublize components of these sludge streams. Increasing the intensity of the steam explosion pressure and temperature resulted in increased solublization. The steam explosion pre-treatment also increased the bioavailability of sludge components under anaerobic digestion conditions. Increasing the steam explosion intensity increased the ultimate yield of CH4 during anaerobic digestion. Batch anaerobic digestion tests suggested that pre-treatment at 300 psi was the most optimal condition for enhanced biogas generation while minimizing energy input. Semi-continuous anaerobic digestion revealed that the results that were observed in the batch tests were sustainable in prolonged operation. Semi-continuous digestion of the TWAS-biosolids mixture that was pre-treated at 300 psi generated approximately 50% more biogas than the controls. Semi-continuous digestion of the pre-treated biosolids resulted in a 3-fold increase in biogas as compared to the controls. Based on capillary suction test (CST) results steam-explosion pre-treatment at 300 psi improved the dewaterability of the final digested sludge by 32% and 45% for the TWAS/bisolids mixture and biosolids respectively as compared to controls.
Document Type: Research Article
Publication date: January 1, 2005
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