Liquid clarification tank

Details Liquid clarification tank Liquid clarification tank

2000-06-05

2001-11-27

Upton, Christopher (Department: 1724)

Liquid purification or separation

Gravitational separator

Material supply distributor

C210S532100, C210S540000

Reexamination Certificate

active

06321916

ABSTRACT:

This invention relates generally to apparatus for treating liquids to remove dissolved or suspended solids, such as for treating water to clarify it for potable or industrial use, or for treating wastewater, and more particularly to clarifiers in which the liquid flows in an upward helical path, gradually decreasing in velocity until precipitated or suspended solids separate from the rising water to create a rotating sludge blanket beneath a region of clarified water.
BACKGROUND OF THE INVENTION
An upflow water clarifier, such as those disclosed in Wyness U.S. Pat. Nos. 4,146,471 and 4,765,891, is a type of clarifier that has a prominent conical portion extending upwardly and outwardly from a central lower cylindrical end. Contaminated water enters the clarifier near the lower end. Inside, the water is given a rotational movement, often in part by feeding it into the clarifier in a tangential direction, resulting in a generally upward helical flow of the water within the clarifier.
The increasing diameter of the clarifier toward its upper end causes a decrease in velocity of the liquid as it moves upwardly. As the velocity decreases, suspended solids having a higher density than water agglomerate and separate from the water, forming a revolving sludge blanket that remains behind as clarified water continues moving upwardly until being withdrawn as clarified effluent.
Conventionally, the effluent is removed from the clarifier over weirs or troughs, while sludge is periodically removed through a sludge concentrator, which is typically located on the central axis of the clarifier, but which can alternatively be provided off of the central axis or even outside of the vessel, immediately adjacent the vessel wall.
One problem with upflow clarifiers is a limitation in the maximum practical size. In order to handle large flow rates, upflow clarifiers can become undesirably tall, leading to difficulties in maintaining structural stability and in fitting into an existing hydraulic profile. If the top of the clarifier is to be at ground level, more difficult and expensive excavation is needed; if the base of the clarifier is to be at ground level, more energy is needed to pump the liquid through the clarifier. Aesthetic concerns may also be a significant problem.
Use of multiple smaller vessels is often not a good solution. Multiple smaller vessels may be more expensive and may require more land than is readily available, and can also create piping and valving problems.
SUMMARY OF THE INVENTION
The applicants have developed a new shape for an upflow clarifier that allows for the clarifier to handle a proportionally greater flowrate of liquid without becoming excessively tall. This results in a clarifier that can fit into a tighter hydraulic profile, allowing greater stability and requiring less pumping energy and less excavation. The more efficient size can also reduce the number of vessels required on a site, reducing the expense and the overall land requirements as well as piping and valving requirements.
Instead of a conventional circular lower chamber for receiving the liquid to be clarified, the claimed design includes a lower chamber that has an extended shape with two curved ends connected by a straight section. The clarifier includes a conventional outer wall extending upwardly and outwardly from the lower chamber, one or more conventional inlets in liquid communication with the lower chamber, a conventional means for withdrawing clarified liquid from near the top of the clarifier, and a conventional sludge removal structure.
A centrally-disposed dividing wall in the lower chamber may aid in the establishment of rotational movement in the liquid as it enters the lower chamber.
Improved construction efficiencies may also be possible. For example, a modular approach can be used to construct clarifiers of various different sizes. Conceptually, a typical clarifier can be cut in half by vertical plane, resulting in a pair of curved sections, and then those halves can be spread apart horizontally and connected by adding a straight section between the curved sections. This allows the capacity of the clarifier to be changed by simply lengthening or shortening the length of the relatively easy-to-fabricate straight section. By enabling the capacity of the clarifier to be changed without requiring any changes in the more complicated curved sections of the clarifier, significant cost savings may be realized.


REFERENCES:
patent: 1607280 (1926-11-01), King
patent: 3965013 (1976-06-01), Jackson
patent: 4487692 (1984-12-01), Kersten
patent: 4976875 (1990-12-01), Ryynänen
patent: 4983294 (1991-01-01), Lamb
patent: 4983295 (1991-01-01), Lamb et al.
patent: 5100545 (1992-03-01), Brooks
patent: 5804062 (1998-09-01), Wyness
patent: 6092671 (2000-07-01), Ruehrwein et al.
patent: 6171498 (2001-01-01), Fassbender et al.

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