Patent ID: 7563374

Claim:
A process for treating concentrated wastewater biosludge, comprising: a) contacting biosludge liquid with feed gas containing at least 20 volume percent oxygen gas in a continuous flow, enclosed, multistage aerobic zone and for a sufficient duration to form oxygenated biosludge having an elevated temperature in at least one stage; said elevated temperature being achieved in the aerobic zone through exothermic biochemical oxidation of the biosludge liquid coincident with said gas-liquid contacting for a high rate of heat and mass transfer between gaseous and liquid phases in each contacting stage of the aerobic zone; b) discharging the oxygenated biosludge liquid from the aerobic zone at an elevated temperature and introducing the biosludge into an anaerobic zone; and c) digesting the biosludge liquid in said anaerobic zone at an elevated temperature and for a sufficient duration to achieve anaerobic stabilization of the biosludge.