Solubilization of organic sludge by thermophilic aerobic bacteria as a pretreatment for anaerobic digestion

Solubilization of organic sludge by thermophilic aerobic bacteria as a pret reatment for anaerobic digestion was investigated. The thermophilic bacteri a which solubilized organic sludge were isolated from the thermophilic aero bic digestion reactor. The bacterium type SPT2-1 could grow at pH ranging f rom 5.0 to 8.5 with optimal temperature at 60-70 degrees C. In batch experi ments, 25-30% of volatile Suspended solids (VSS) in the pre-heated sludge w ere solubilized on inoculating with the isolated bacteria although little w as solubilized without inoculation. The isolated bacteria appeared to secre t the extracellular enzymes including proteases and amylases. In continuous flow experiments, sludge solubilization rate (VSS removal) was around 40% under aerobic as well as microaerobic conditions. No accumulation of volati le fatty acids in the treated sludge was observed under aerobic conditions while significant amounts of them were accumulated under microaerobic condi tions. Production of biogas on anaerobic digestion of the microaerobically- pretreated sludge was increased by 1.5 when compared with the sludge withou t pretreatment.