Abstract: A continuous flow multistage aerobic wastewater sludge treatment system and process comprising at least two stages connected in series, each stage comprising one or more covered tanks, tank segments or compartments, each having an enclosed separate gas headspace, wherein the gas headspaces of each stage are connected in a specified sequence that may be identical to or different from the staging sequence followed by the sludge liquid. An oxygen containing gas stream, such as air or an oxygen enriched gas stream, is supplied to the headspace of each stage, and a means for aerating the sludge in one or more of the tanks, tank segments or compartments is provided to enhance the transfer of oxygen from the gas headspace into the sludge liquid for use by bacteria in digestion of the sludge. At least one stage of the sludge digestion system is operated at a thermophilic temperature above 50° C.

Abstract: A continuous flow multistage aerobic wastewater sludge digestion system comprising at least two stages connected in series, each stage comprising one or more covered tanks, tank segments or compartments, each having an enclosed separate gas headspace, wherein the gas headspaces of each stage are connected in a specified sequence that may be identical to or different from the staging sequence followed by the sludge liquid. An oxygen containing gas stream, such as air or an oxygen enriched gas stream, is supplied to the headspace of each stage, and a means for aerating the sludge in one or more of the tanks, tank segments or compartments is provided to enhance the transfer of oxygen from the gas headspace into the sludge liquid for use by bacteria in digestion of the sludge. At least one stage of the sludge digestion system is operated at a thermophilic temperature above 50° C.

Abstract: A continuous flow multistage aerobic wastewater sludge digestion system comprising at least two stages connected in series, each stage comprising one or more covered tanks, tank segments or compartments, each having an enclosed separate gas headspace, wherein the gas headspaces of each stage are connected in a specified sequence that may be identical to or different from the staging sequence followed by the sludge liquid. An oxygen containing gas stream, such as air or an oxygen enriched gas stream, is supplied to the headspace of each stage, and a means for aerating the sludge in one or more of the tanks, tank segments or compartments is provided to enhance the transfer of oxygen from the gas headspace into the sludge liquid for use by bacteria in digestion of the sludge. At least one stage of the sludge digestion system is operated at a thermophilic temperature above 50° C.

Abstract: The invention is an improved surface aeration impeller for use in a liquid filled tank which particularly increases the surface turbulence and the entrainment of gas into the liquid surface. The impeller is an axial flow impeller and may be either a pitched blade turbine (PBT) or have airfoil shaped blades. In either case, the impeller has a portion which extends radially along an edge thereof which projects above the surface of the liquid being mixed in a vertical direction. The blades of the impeller are modified to include a top horizontal plate to lower the spray height of the liquid and an optional endcap, both of which can enhance and increase the standard aeration efficiency. Preferably, the impeller is rotated in an up-pumping direction and propels the liquid being aerated in a radially upward and outward direction. A sufficient upward surge of liquid is produced so that the liquid is observed to splash back onto the surface a plurality of times in the course of operation of the impeller.

Abstract: A surface aeration impeller for use in a liquid filled tank. The impeller is rotatable about an axis perpendicular to the static liquid surface. The impeller has a plurality of blades mounted on the underside of a disc or disc-like surface. Each blade has a multi-faceted or curved geometry ranging from vertical at the point of attachment to the disc to partially inclined at the bottom. The blades are spaced circumferentially about the axis and are disposed at acute angles to radial lines from the axis of rotation of the impeller. The lower portions of the blades, which are inclined but non-vertical, are positioned at or below the static liquid surface. When the impeller is rotated, the lower portion pumps the liquid up onto the vertical portion of the blades where the liquid is discharged into a spray umbrella in a direction upwardly and outwardly away from the impeller.

Abstract: A surface aeration impeller for use in a liquid filled tank. The impeller is rotatable about an axis perpendicular to the static liquid surface. The impeller has a plurality of blades mounted on the underside of a disc or disc-like surface. Each blade has a multi-faceted or curved geometry ranging from vertical at the point of attachment to the disc to partially inclined at the bottom. The blades are spaced circumferentially about the axis and are disposed at acute angles to radial lines from the axis of rotation of the impeller. The lower portions of the blades, which are inclined but non-vertical, are positioned at or below the static liquid surface. When the impeller is rotated, the lower portion pumps the liquid up onto the vertical portion of the blades where the liquid is discharged into a spray umbrella in a direction upwardly and outwardly away from the impeller.