Sludge digestion methods and apparatus

A method of aerobically digesting organic material in wastewater, the method comprising the steps of:

• a) providing the wastewater comprising the organic material to a digester that comprises:
• a vessel for containing a liquid, the vessel having an interior comprising an upper portion and a lower portion and a lower interior surface;
• a tube having a distal end disposed in the lower portion of the interior of the vessel, an opening in the wall of the tube for permitting liquid and air flow between the exterior and interior of the tube, and at least one discharge port disposed in the distal end;
• and
• a liquid conveyor disposed within the tube for inducing flow of the liquid through the tube in the direction of the distal end, the conveyor comprising an impeller disposed below the opening;
• and
• b) circulating the liquid in the digester by way of the tube, whereby the conveyor induces entrainment of air into the liquid drawn into the tube by way of the opening to form a liquid-air mixture and expulsion of the liquid-air mixture from the tube through the at least one discharge port, thereby inducing mixing and aeration of the liquid in the vessel and digesting organic material in the wastewater.