Abstract: Method and system for treating wastewater includes treating sludge with ozone in a plug-flow type reactor to cause lysis of biosolids in the sludge. The ozonated sludge may be provided to an anaerobic or anoxic section of the wastewater treatment system to aid the denitrification processes occurring in the anaerobic or anoxic section of the wastewater treatment system or to other sections of the wastewater treatment system such as a fermenter, an aerobic digester, or an anaerobic digester.

Abstract: A method and apparatus for injecting a gas into a liquid in which a rotating helical impeller within a draft tube submerged in the liquid creates a liquid flow within the draft tube. Gas bubbles are injected into the draft tube either above or below or alongside the helical impeller or in all three locations. The liquid is drawn into the draft tube with a superficial velocity greater than a substantially uniform terminal ascent velocity of the gas bubbles to allow entrainment of undissolved gas bubbles in the bulk liquid into the liquid being drawn into the draft tube. The gas bubbles are injected with a uniform diameter of between about 10.0 microns and about 1.0 millimeters. The small bubble size enhances the dissolution of the gas into the liquid and also allow the entrainment of the gas into the liquid being drawn into the draft tube.

Abstract: A method of operating a waste water treatment facility to prevent bulking in which growth of floc forming bacteria is promoted within a selector aeration tank by controlling absorption and bio-oxidation of biodegradable soluble chemical oxygen demand by the bacteria. Absorption is controlled through measurement of a percentage removal of biodegradable soluble chemical oxygen demand and bio-oxidation is controlled through measurement of temperature corrected specific oxygen uptake rate. Both the absorption and bio-oxidation levels are controlled by decreasing the degree to which wastewater influent flow bypasses the selector aeration tank in favor of the main aeration tank when either of absorption or bio-oxidation are below targeted ranges and increasing flow rate of recycle activated sludge from the clarifier to the main aeration tank while decreasing recycle activated sludge flow rate to the selector aeration tank when absorption and bio-oxidation are above such targeted ranges.

Abstract: A method and apparatus for injecting a gas into a liquid in which a rotating helical impeller within a draft tube submerged in the liquid creates a liquid flow within the draft tube. Gas bubbles are injected into the draft tube either above or below or alongside the helical impeller or in all three locations. The liquid is drawn into the draft tube with a superficial velocity greater than a substantially uniform terminal ascent velocity of the gas bubbles to allow entrainment of undissolved gas bubbles in the bulk liquid into the liquid being drawn into the draft tube. The gas bubbles are injected with a uniform diameter of between about 10.0 microns and about 1.0 millimeters. The small bubble size enhances the dissolution of the gas into the liquid and also allow the entrainment of the gas into the liquid being drawn into the draft tube.

Abstract: A method and apparatus for injecting a gas into a liquid in which a rotating helical impeller within a draft tube submerged in the liquid creates a liquid flow within the draft tube. Gas bubbles are injected into the draft tube either above or below or alongside the helical impeller or in all three locations. The liquid is drawn into the draft tube with a superficial velocity greater than a substantially uniform terminal ascent velocity of the gas bubbles to allow entrainment of undissolved gas bubbles in the bulk liquid into the liquid being drawn into the draft tube. The gas bubbles are injected with a uniform diameter of between about 10.0 microns and about 1.0 millimeters. The small bubble size enhances the dissolution of the gas into the liquid and also allow the entrainment of the gas into the liquid being drawn into the draft tube.

Abstract: A method and system for controlling dissolved oxygen levels in a secondary treatment system of a wastewater treatment facility that can employ a membrane bioreactor in which oxygen introduction into mixed liquor is controlled to prevent bulking and minimize generation of extra cellular polymeric substances. The control is exercised by insuring that dissolved oxygen levels within the mixed liquor do not fall below a minimum system level at which microorganism stress would occur. This is done by setting a minimum dissolved oxygen level control point equal to a sum of the minimum system level and an adjustment factor determined on the basis of oxygen uptake rate and time delays inherent in sensing oxygen levels and changes thereof within the mixed liquor. The minimum system dissolved oxygen level can be continually calculated on the basis of an inferred food to mass ratio that would vary with sensed mixed liquor suspended solids.

Abstract: A method and system for controlling dissolved oxygen levels in a secondary treatment system of a wastewater treatment facility that can employ a membrane bioreactor in which oxygen introduction into mixed liquor is controlled to prevent bulking and minimize generation of extra cellular polymeric substances. The control is exercised by insuring that dissolved oxygen levels within the mixed liquor do not fall below a minimum system level at which microorganism stress would occur. This is done by setting a minimum dissolved oxygen level control point equal to a sum of the minimum system level and an adjustment factor determined on the basis of oxygen uptake rate and time delays inherent in sensing oxygen levels and changes thereof within the mixed liquor. The minimum system dissolved oxygen level can be continually calculated on the basis of an inferred food to mass ratio that would vary with sensed mixed liquor suspended solids.

Abstract: A method and apparatus for injecting a gas into a liquid in which a rotating helical impeller within a draft tube submerged in the liquid creates a liquid flow within the draft tube. Gas bubbles are injected into the draft tube either above or below or alongside the helical impeller or in all three locations. The liquid is drawn into the draft tube with a superficial velocity greater than a substantially uniform terminal ascent velocity of the gas bubbles to allow entrainment of undissolved gas bubbles in the bulk liquid into the liquid being drawn into the draft tube. The gas bubbles are injected with a uniform diameter of between about 10.0 microns and about 1.0 millimeters. The small bubble size enhances the dissolution of the gas into the liquid and also allow the entrainment of the gas into the liquid being drawn into the draft tube.

Abstract: A system and method for ozone vent gas reuse is provided. The disclosed system and method involve controlling or conditioning the ozone vent gas stream or degassing unit vent gas stream and directing the stream to a mechanically agitating contactor in an aerobic section of the wastewater treatment system. The oxygen content of the vent gas stream is controlled so as to ensure sufficient oxygenation to the aerobic section of the wastewater treatment system. Control may be effected by adjusting the oxygen content of the vent gas stream in response to sensor or measurement inputs characterizing the gas contents of the vent gas stream or the dissolved oxygen levels. The volumetric flow of the vent gas stream to the aerobic section may also be controlled by adjusting the rotational speed of the mechanically agitating contactor in an aerobic section of the wastewater treatment system.