Continuous multistage thermophilic aerobic and aerobic-anaerobic sludge treatment process

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 into enclosed, alternating mixing tanks wherein the biosludge is held in batch mode for a sufficient duration and temperature to achieve pasteurization;
• and
• c) digesting the biosludge liquid in an anaerobic zone at an elevated temperature and for a sufficient duration to achieve anaerobic stabilization of the biosludge.

A process for treating concentrated wastewater biosludge for producing a pasteurized Class A sludge, 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;
• and
• b) treating the biosludge liquid in enclosed, alternating mixing tanks wherein the biosludge is held in batch mode for a sufficient duration and temperature to achieve pasteurization, followed by treatment of the biosludge in one or more stages of said aerobic zone.