Gas and liquid contact apparatus – Contact devices – Rotating
Reexamination Certificate
1999-12-30
2001-05-08
Bushey, C. Scott (Department: 1724)
Gas and liquid contact apparatus
Contact devices
Rotating
C261S091000
Reexamination Certificate
active
06227525
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a device for treating liquids, in particular waste water, which comprises a surface aerator and also a mixer.
2. Prior Art
Aerators and mixers for treating waste water are known. By way of example, Belgian Patent BE 893,687 describes an aerator or mixer comprising a power source, attached to a float, which drives a shaft to which a screw pump is attached. In aerators of this type, the screw pump is usually surrounded by a water-guidance cylinder (pump housing), in which the water is pushed towards the surface of the water and is distributed over this surface. Below the screw pump, the pump housing may, for example, be shaped further to form a suction cone in order to promote the suction of water.
When treating waste water, it may be advantageous alternately to aerate the water (by introducing oxygen) and to mix the water (without the introduction of oxygen). The result is alternating processes of nitrification and denitrification which can be controlled as desired. In some cases, it may also be appropriate to aerate and mix simultaneously.
In deep pools, it is also possible to bring about simultaneous zones of aeration (nitrification) at the top and mixing (denitrification) at the bottom. If more than one unit is placed in a pool, it is possible to create different aeration zones and mixing zones which may be dimensioned and controlled in accordance with the requirements of the process.
Therefore it is not infrequently the case that a mixer is disposed fixedly in the pool, for example on the bottom of the pool or on a side wall, with the result that the two components are present as separate entities.
However, the fixed arrangement of a mixer in a pool is not an ideal solution, and such a mixer, if it is positioned on the bottom, is difficult to manipulate, to move or to maintain. For example, every manipulation requires additional material (bridge and hoisting crane) to be deployed. If the mixer is attached to the side wall of the pool, mixing is often limited to a specific zone and the desired mixing effect is not obtained. Especially in deep pools, it has been found that this arrangement does not allow an adequate mixing pattern to be achieved.
It has also already been proposed (for example in French Patent Application 87 00604) to lengthen the shaft of the aerator and to arrange a screw on this shaft in the pool, so that the appliance is simultaneously an aerator and a mixer.
However, such an apparatus has the drawback that the mixer and the aerator cannot function independently of one another and that, for example during a denitrification process, the aerator cannot be shut down. In other circumstances, it is not necessary for the mixer to function continuously together with the aerator in order, for example, to keep the particles in suspension. In many cases, it may be advantageous for the mixer and the aerator to be able to function alternately. Moreover, with regard to efficiency it is advantageous to save the power required to drive the mixer if mixing were to be unnecessary or disadvantageous for treating the water.
It is to be noted that U.S. Pat. No. 3,865,909 describes an aerating device having a submersible motor supported by a float member and a propeller which propels the water upwardly against a diffuser. This apparatus can be arranged to carry a second motor and propeller to move the water upwardly from deeper depths and thus to improve the action of the main submersible motor. However, this device does not create different aeration and mixing zones and both propellers do not function independently of one another to allow the creation of either a nitrification and/or a denitrification process. Furthermore, this device does not constitute an efficient and economic aeration process as the power source is situated under water and in the absence of a guidance housing can not create a strong upward movement of the water.
SUMMARY OF THE INVENTION
The object of the invention is to propose an apparatus, device or appliance which comprises both a mixer and an aerator which are able to operate independently of one another, with the result that the apparatus offers more possibilities than a dual-purpose appliance which can only either aerate or mix in the same pool or pool zone.
The device according to the invention comprises a surface aerator which draws in liquid and distributes it over the surface of the liquid, as well as a structure which extends beneath the surface of the liquid and to which at least one mixer is attached, which mixer functions independently of the aerator.
The result is a surface aerator and a mixer which form a single unit and can easily be moved as a unit, but in which the two components can operate either separately or together.
Such a device makes it possible to obtain a mixing pattern which is adapted to the volume of the pool, the pool geometry and the requirements of the treatment process.
Thus such a device can also be used to carry out simultaneous nitrification and denitrification in the same pool, if the water circulation of the aerator and the mixer are controlled in such a manner that the two flows have little or no effect on one another.
Thus the device according to the invention makes it possible to employ only surface aeration or only a mixing action, or to employ both functions together. By introducing air or oxygen in the vicinity of the mixer, it is also possible to bring about bottom aeration.
According to one embodiment of the invention, the device may be positioned on a float, the aerator being attached to the float and the float or one of the components of the aerator comprising the structure to which the mixer is attached. The float may be assembled from one or more floats.
According to a further embodiment, the apparatus may be attached fixedly or movably above the pool.
According to a preferred embodiment, the mixer is displaceably attached to the structure, so that the mixer can be displaced vertically. It is also possible to make the orientation of the mixing member of the mixer changeable, so that it is possible to obtain a mixing pattern in all possible directions.
It is also possible to position the mixer eccentrically with respect to the aerator. In this arrangement, all other positions are possible, such as vertical adjustment and changeable orientation. If, in this case, the device is placed on a float, the float must always be dimensioned so as to ensure the stability in all embodiments.
REFERENCES:
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patent: 2530814 (1950-11-01), De Becze et al.
patent: 3521864 (1970-07-01), Welles, Jr.
patent: 3572658 (1971-03-01), Ravitts
patent: 3650950 (1972-03-01), White
patent: 3865721 (1975-02-01), Kaelin
patent: 3865909 (1975-02-01), Cramer, Jr.
patent: 4290885 (1981-09-01), Kwak
patent: 4869818 (1989-09-01), DiGregorio et al.
patent: 527773 (1972-10-01), None
patent: 366644 (1989-10-01), None
patent: 2609459 (1988-07-01), None
patent: 57-113891 (1982-07-01), None
patent: 57-177394 (1982-11-01), None
Aquasystems International N.V.
Bushey C. Scott
Hovey Williams Timmons & Collins
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