Method and apparatus for treating organic wastewater

DETAILED DESCRIPTION Referring now to the drawing of the apparatus, all standard components shown, such as the valves, pumps, blower, air compressor assembly, liquid level controller and piping (which are not described in the claims) are conventional and their uses and functions are well known in the art.
The configuration shown in the FIGURE is sized for a sewage strength of 200 mg/l BOD.
sub.
5 and a treatment rate of 12,000 gallons per day (gpd).
The normal mixed liquor concentration will be 10,000 mg/l SS, making a food to micro-organism (F:M) ratio of 0.
20.
Sizing and dimensions are only approximate and could be scaled upward or downward, depending on the strength and quantity of sewage to be treated.
Organic waste water that has been screened and degritted (or macerated) is pumped continuously or intermittently (as needed) into the aerator unit (vessel #1) by means of a single stage centrifugal pump 4, through a flap gate check valve 5 into the return sludge pipeline 6, where it intermixes with the return sludge and enters into vessel #1.
Mixed liquor (return sludge mixed with incoming sewage) from conduit 6, is dosed with a continuous stream of air bubbles rising from aerator head 7 located in the bottom of pressure vessel #1.
The diffused air bubbles 8 become attached to the sludge floc and buoy it upward to the interface of the air dome 9, where the floc is further saturated with air before sinking downward along the walls of vessel #1.
Oxygen transfer to the mixed liquor occurs through diffusion of air bubbles from aerator head 7 into the liquor and from a rolling interface of the liquor with the air dome 9.
Elevated pressure within the containment vessel #1 (up to 35 pounds per square inch gauge) provides an extremely efficient driving force for transfer of oxygen into the mixed liquor.
The mixed liquor in vessel #1 cycles continuously upward at the center and downward near the perimeter, eventually flowing out (by gravity) through conduit 10 into aeration vessel #2.
As receiving unit for sewage influent, the first stage aerator (vessel #1) sustains the highest oxygen demand