Liquid purification or separation – Processes – Treatment by living organism
Reexamination Certificate
1999-10-08
2001-05-01
Upton, Christopher (Department: 1724)
Liquid purification or separation
Processes
Treatment by living organism
C210S629000, C210S800000, C210S195400, C210S197000, C210S519000, C210S532100
Reexamination Certificate
active
06224773
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to wastewater treatment systems, and more particularly to a system having a vessel or tank with integral treatment and settling chambers.
In a common type of wastewater treatment system, wastewater is treated by aeration in a first tank. Wastewater from this treatment or aeration tank is delivered to a second tank where settling of sludge components is allowed to occur. A lower end of this settling or clarification tank is connected to a lower end of the aeration or treatment tank.
U.S. Pat. Nos. 5,766,459 and 5,830,351 to Carl E. Adams, Jr., disclose such an activated sludge system wherein the clarification and aeration tanks are chambers in the same vessel. The chambers are defined or separated by an inclined baffle plate so that the clarification chamber tapers in a downward direction to funnel the sludge towards an opening or gap at the lower end of the baffle. The sludge moves through the gap into a lower region of the aeration chamber, propelled in part by a recycle pump which draws wastewater from the aeration chamber and delivers the wastewater to the upper surface of a cylindrical or rectangular well located at the upper end of the clarification chamber. The center well serves to direct the delivered recycled wastewater in a downward direction through the clarification chamber.
In particular embodiments of these integral wastewater treatment systems, the baffle and consequently the clarification chamber may have a conical or rectangular configuration. The clarification chamber tapers at its base to a narrow throat where the sludge reenters the aeration chamber. In certain configurations, it has been noticed that the gap extending between the narrow throat at the base of the clarification chamber and the lower region of the aeration chamber, although narrow and designed to maintain a downward and outward velocity, permits miscellaneous and unpredictable backmixing generating of undesirable upward currents into the clarification chamber. These upward currents interfere with an even distribution of the returning or settling sludge in the clarification chamber and, in some cases, cause a bridging or accumulation of sludge at the base of the clarification chamber. The bridging in turn can result in floating sludge on the surface of the clarification pool. Although the floating sludge does not impair proper operation of the wastewater treatment system, that phenomenon does present an aesthetic drawback.
SUMMARY OF THE INVENTION
The present invention is directed to an improved wastewater treatment system of the above-described type. More specifically, the present invention is directed to providing a solution to the problem of backmixing and undesirable upward currents in the clarification chamber of a wastewater treatment system. The present invention introduces improvements into the design of an integral type wastewater treatment system for the purpose of enhancing directional flow of wastewater in the clarification chamber and between the clarification chamber and the aeration chamber.
A wastewater treatment system in accordance with the present invention comprises a tank and at least one baffle disposed in the tank so as to subdivide the tank to form a treatment chamber and a clarification or settling chamber. The baffle is preferably inclined relative to vertical, so that the clarification chamber tapers from an upper end to a lower end. The lower end of the clarification chamber is provided with a plurality of mutually spaced orifices or apertures communicating with a lower region of the treatment chamber, so that sludge settling in the clarification chamber is directed to the lower region of the treatment chamber via the orifices.
It is contemplated that the settling sludge passes from the base or lower end of the clarification chamber to the lower region of the treatment chamber solely through the orifices. These orifices collectively function as a bottle neck to constrict the cross-sectional area of the flow path from the clarification chamber to the treatment chamber. Accordingly, the velocity of the sludge entering the treatment chamber is increased with respect to prior wastewater treatment tank designs.
Pursuant to another feature of the present invention, the clarification chamber is provided at its lower end with a plurality of substantially vertical partitions defining a plurality of hoppers communicating with respective orifices for guiding sludge to the orifices. Where the lower end of the clarification chamber is elongate and has an axial or longitudinal dimension, the partitions extend substantially perpendicularly to the axial or longitudinal dimension. Where the clarification chamber is annular, the partitions extending radially. In general, the hoppers are equal in number to the orifices.
The hoppers facilitate a uniform feeding of sludge to the various orifices and ensure that the orifices receive a substantially constant continuous supply of sludge. The uniform and continuous feeding of sludge to the orifices assists in preventing any backflow currents. The uniform and continuous feeding of sludge may be enhanced by shaping the hoppers to optimally funnel settling sledge to the orifices. For example, the hoppers may taper down to the orifices.
In accordance with a further feature of the present invention, the wastewater treatment system further comprises a recycle pump and a distribution manifold. The pump serves to recycle wastewater from the treatment chamber to the clarification chamber and accordingly communicates at an inlet end with the treatment chamber. The distribution manifold is connected to an outlet end of the recycle pump and is provided at an outlet side with a plurality of spaced vertical nozzle pipes.
Preferably, the nozzle pipes have outlet ends disposed in the clarification chamber. A common conduit of the manifold may also be at least partially disposed in the clarification chamber. More specifically, the outlet ends of the nozzle pipes and at least a portion of the common conduit of the manifold are located in the wastewater/sludge pool in the clarification chamber.
Where the clarification chamber has an axial or longitudinal dimension, the nozzle pipes are preferably spaced from one another along the axial or longitudinal dimension. Where the clarification chamber is annular, the nozzle pipes are preferably disposed along a circular arc.
The provision of multiple vertical nozzle pipes facilitates a discharge of recycled wastewater in a downward direction and thus enhances the unidirectional downward flow of sludge in the clarification chamber.
In accordance with an additional feature of the present invention, the recycle pump and the orifices are sized so that a sludge mixture passing from the lower end of the clarification chamber to the lower region of the treatment chamber via the orifices has a velocity sufficiently great to substantially prevent backflow currents from the lower region of the treatment chamber to the lower end of the clarification chamber. More specifically, the recycle pump and the orifices are sized so that a sludge mixture passing from the lower end of the clarification chamber to the lower region of the treatment chamber via the orifices has a velocity of at least 10 cm per second and more preferably 15 cm per second or greater.
The hopper partitions and the wall structure surrounding the orifices may be made of any material that is resistant to the constituents of wastewater. Such materials include grout, steel or plastic.
The orifices and hopper partitions of the present invention can be retrofit to existing wastewater installations. Accordingly, the present invention is also directed to a method for modifying an existing wastewater installation to produce the benefits of the present invention, where the existing wastewater treatment system generally comprises a tank and at least one baffle disposed in the tank and subdividing the tank to form a treatment chamber and a clarification chamber. The baffle is inclined relative to vertical so that the clari
Coleman Henry D.
Sudol R. Neil
The Advent Corporation
Upton Christopher
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