GB2096908A - Waterwheel system for aeration - Google Patents

Abstract

A waterwheel system for the economical aeration or cooling of water in sewage treatment tanks and fishponds, in which an aerator waterwheel (1) including a plurality of porous tubes (2a) encircling and fixed to a rotary shaft (3) in parallel therewith by means of disks (4) is disposed near the water surface of a water tank (10) so that the tubes situated at the bottom are immersed in the water, and the waterwheel is rotated at such a slow speed that heavy splashing will not be produced by the waterwheel. <IMAGE>

Description

SPECIFICATION Waterwheel system for aeration The present invention relates to a waterwheel system for the aeration or cooling of water in sewage treatment tanks or in fishponds.

In one sewage treatment method utilizing active sludge, the water in the treatment tank is agitated and aerated by ejecting compressed air from an air blowing device disposed at the bottom of the tank, thereby imparting oxygen to bacteria to promote their breeding, so that the water may be purified by consumption of organic matter in the water.

In such a sewage treatment method involving aeration, there is a considerable difference in weight between water and air, and therefore the air bubbles float to the surface abruptly.

Consequently, notwithstanding the significant effect of agitation thus attained, the all important time for the water to make contact with the air for dissolving oxygen in it is short, resulting in very low aeration efficiencies.

With increasing blowing depths, the required pressure or the potential energy augments. Thus this pressure energy is exhausted without much contribution to the effect of aeration. This is the reason why the active sludge process requiring the use of a large absolute quantity of oxygen consumes a considerable amount of power.

Also, in another active sludge process which uses a splashing and sprinkling system incorporating a high speed rotary impeller at the water surface or the method of aeration by a water wheel system in fishponds, the effect generated by the splashing is dissipated in a short period of time as in the previous method.

Moreover, since the energy loss resulting from collision between water, solids and air increases in direct proportion to the square of their relative velocities, at high rotational speeds of the waterwheel, the impact energy loss is excessively large, thus consuming more power than in the previous method.

It is known for cooling hot or warm water, to use a water cooling tower system involving the sprinkling of a large amount of heavy water raised to the top of the tower. Such a cooling system is disadvantageous in that its operating efficiency is lower than the method of water bottom blow-off, consuming a considerable amount of energy, and moreover, is more expensive to install.

The main object of the present invention is to provide a waterwheel system for aeration purposes in which the aforesaid disadvantages are reduced or avoided.

From one aspect, the present invention consists in a waterwheel system for aeration characterized in that the waterwheel is formed by encircling its shaft with a plurality of porous tubes, and the agitation and aeration of water are effected by turning this waterwheel relatively slowly, while keeping the honeycombed tubes at the bottom position immersed in water.

From another aspect, the present invention consists in a method of aerating or cooling water characterized by slowly rotating a waterwheel including a plurality of porous tubes such that the lowermost tube or tubes is or are immersed in the water.

In order that the invention may be more readily understood, some embodiments thereof will now be described, by way of example with reference to the accompanying drawings, in which:~ Fig. 1 is a part-sectional front elevation of a waterwheel system constructed in accordance with this invention, Fig. 2 is a cross-section taken on the line Il-Il of Fig. 1, Fig. 3 is an end view to an enlarged scale looking in the direction of the arrows on line Ill-Ill of Fig. 1 and showing an end plate of the waterwheel, Fig. 4 is a perspective view of one embodiment of a porous tube made of a synthetic resin used in the waterwheel;; Fig. 5 is a similar perspective view of another embodiment of porous tube made of a synthetic resin, being a composite tube formed of two tubes, Fig. 6 is an end view of the waterwheel system as incorporated in a sewage treatment plant, Fig. 7 is a front elevation of the treatment plant of Fig. 6, Fig. 8 is a perspective view of one embodiment of filter medium of a synthetic resin for use in the sewage treatment system, Fig. 9 is a longitudinal section of Fig. 8, Fig. 10 is a perspective view of another embodiment of filter medium, Fig. 1 1 is a longitudinal section of Fig. 10, Fig. 12 is a cross-section of a third embodiment of filter medium, and Fig. 13 is a perspective view of a fourth embodiment of filter medium.

Referring to Figs. 1 to 5, there is shown an aerator waterwheel 1 comprising a rotary shaft 3, a plurality of honeycombed tubes 2a made of a synthetic resin encircling the rotary shaft 3, and extending parallel thereto, forming tube wings 2, and a pair of circular end plates 4 fixed to the rotary shaft 3, and supporting the honeycombed tubes 2a at their ends.

The aerator waterwheel 1, although its diameter is relatively small, has a sufficiently large length in the direction of its rotary shaft 3, as to correspond substantially in length to the width of the water treatment tantank. This structure is considerably different from the conventional thin, large diameter, waterwheels. This waterwheel should run at a rotational speed of 10 m/min. to 100 m/min., which is a slow enough range to produce a small impact on the water and thus avoid heavy splashing yet is not so slow that sticky animals and plants are deposited on the waterwheel, and breed there and grow.

The tube wings 2 for scooping up water which are the major component of the waterwheel 1, are long honeycombed tubes 2a made of a synthetic resin. A plurality of such tubes are spaced around the outer circumference of the waterwheel 1, at specified intervals by the end plate discs 4, 4 which are fixed to the shaft 3 by fittings 5, 5 integral with the shaft 3, and clamping bolts 8, 8 so that the tubes are fast for rotation with the shaft. If the waterwheel has a length which is more than twice as great as its diameter, wobbling at the center of a tube wing 2 formed of a small diameter honeycombed tube 2a may occur when the tube is scooping up water. This wobbling may be prevented by securely locating, on the rotary shaft 3, intermediate supports 6 for fixing the tube wing 2 at as many intermediate positions on the shaft 3, as required.In Fig. 1, the intermediate supports 6 include semi-circular bands 7 which are clamped rigidly around the external periphery of the tubes 2a.

In this way, even though the tube wings 2 are honeycombed tubes 2a made of a synthetic resin having having only a small strength, the waterwheel 1 of great length is very sturdy. In order that the aerator waterwheel 1 can perform a water raising function, as described later, the end plates 4 are made with a diameter which is nearly equal to the outer circumference of the waterwheel for prevention of water leakage in the directions towards both ends of the rotary shaft 3.

The end plates 4 are rigidly secured to the tube wings 2, by means of short tubular supports 9 which project axially towards each other in the position illustrated from the inside surface of the end plates 4 and have an outer diameter equal to the inner diameter of the tube wing 2. The ends of the tube wings 2 are firmly fitted over the tubular supports 9. Alternatively, the supports 9 may have an inner diameter equal to the outer diameter of the tube wings 2 and the latter be fitted into the supports 9. Either of these methods may be usable, and, of course, the fixation is made more effectively by applying both means.

The rotary shaft 3 of the aeration waterwheel 1 is horizontally supported, as shown in Fig. 1, on the tops of the water tank walls 10 through the intermediary of bearings 11, 11. The waterwheel 1 is so positioned above the water surface 12 that the bottom tube wing 2 is immersed in the water and the shaft 3 is rotated at a low speed falling in the aforementioned range by driving means which may be of any suitable kind and which have, therefore, not been shown.

Since the aerator waterwheel 1, has little impact on the water surface at the low speed of rotation, the energy loss involved in its running is incomparably smaller than that of the hitherto known high speed rotary wing waterwheels which produce heavy splashing, but its aeration effect does give rise to question. However, as the essential requirements for aeration involve matters of how the contacting surface between water and air can be increased and whether the contacting surface parts can successively form new interfaces, the best aeration is not achieved by splashing and dispersion, the blowing-in of small bubbles and the air blow-off method.

The question of satisfactory aeration is answered by having the tube wings 2 of the aerator waterwheel 1 in the form of a porous, perforated, honeycombed or otherwise porous tubes. Thus, when each tube wing 2 is submerged under water while the wheel is turning, water jets into the tube through the numerous small perforations on its circumference, expelling air in the tube wing 2 to replace it, or capturing air bubbles in admixture, and then, the air bubbles are discharged into the water.On the other hand, when this tube emerges above the water surface, water drips through the numerous small perforations; air is sucked into the tube; the residual water captures air bubbles, and flows down, while rotating along the inside and outside of the tube wing 2, following the angular positions of the turning tube wing 2, and so forth, so that not only is there an increase in the contacting surface with air but also there is ideal variation of aeration in the state of interface in perfect compliance with the requirements for aeration.

Such a tube wing has an aeration effect incomparable to that attainable with the mere plate wing which barely serves to entrain air or bring up water. On this ground, it offers a system no less efficient than the splashing and dispersing method, which suffers only a very small impact loss, raises only a very small amount of water to a low level, thus consuming only a very small amount of energy. If the in and outside tube wall surfaces of the tube wing 2 are not mere porous smooth surfaces, and the rough surfaces have growing degrees of undulation, such surfaces are more effective for increasing dripping water and entraining air bubbles.

For the honeycombed or porous, or perforated tubes of synthetic resins of this type, the mesh tube 2' as shown in Fig. 4 manufactured by the method of Japanese Patent Gazette Publication No. Sho 34-4185 or No. Sho 38-21224 can be said to be the best among all such tubes. This tube 2' is a mesh woven of molten resin wires by bringing together and securing them in place, to be formed into a tubular shape, followed by setting by water cooling. The degree of undulating roughness on the inside and outside surfaces is very coarse. Honeycombed (porous) tubes with such a high undulating surface roughness formed by a single process without relying on other treatments are not available. According to a preferred embodiment of this invention, the tubes may be manufactured with part of the tube wall being made blind as shown at 2" in Fig. 4. If this blind part 2" is located in the place where the tube plays the role of an effective paddle plate for scooping up water when the waterwheel 1 is being turned, the capacity of the waterwheel 1 for scooping up water can be much greater.

With regard to ease of manufacture and strength, the waterwheel 1 having tube wings 2 is advantageous in comparison to the conventional plate wing type waterwheels. Such a waterwheel shows a very small strain under the stress resulting from scooping up water, which may be adequately dealt with some synthetic resins which have a strength of only one several tenth of that of metal.

The tube wings 2 can be easily and satisfactorily fitted. Moreover, this tube wing is superior in corrosion resistance and durability to metal products which is important since the tube wings 2 are submerged under water. This superiority is remarkable especially where porosity and undulating roughness count.

The rotary shaft 3 and the end plates 4 of the waterwheel 1 are desirably made of a noncorrosible or corrosion resistant metal and since adhesives are not effective for integrally securing the assembly of metal and synthetic resin parts, and bolting tends to loosen, the method of engaging fitting of tube wings on end plates may be said to be the best way of fixation. The employment of this tube wind 2 makes possible low cost manufacture of a waterwheel 1 which is very simplified, has a small number of parts, and is long and light in weight. Adaptation to the width of the already installed water tank may be made by altering the length of the rotary shaft 3 and the tube wing 2 of the waterwheel 1. Then, the demand will be met by instant delivery of other quantity produced standardized parts on hand.

With a view to omitting the intermediary supports, both ends of two honeycombed tubes may be integrally welded as at 13 (Fig. 51 to form a composite tube 14, which in turn, is rigidly secured by means of the end plates 4, 4 and projecting supports 9', 9' (Fig. 3) for the composite tube. With this assembly of waterwheel 1, the major stress of water acting on the tube wings 14 while the waterwheel 1 is turning is applied in the direction tangential to the outer circumference of the waterwheel 1 , which is borne by the composite tube 14 possessing the strength of two tubes. Thus this waterwheel can bear greater stresses.

Since this aerator waterwheel 1 turns at a level where it is slightly immersed in the water below the surface 12, it is simply impossible for the water at the bottom of a deep water tank to be aerated.

As a remedy, a vertical diaphram 15 is placed through the intermediate depth of the water tank 10, extending in the direction of the waterwheel shaft 3, to partition the tank, thereby forming a U-shaped communicating vessel, and thus providing a vertical circulation route of water flow in the tank (as indicated by the arrows 16 in Fig. 2). In addition, an arcuate diaphragm 18 contiguous or continuous with the top of the said diaphram 1 5 is extended towards the turning direction (as indicated by the arrow 1 7 in Fig. 2) of the waterwheel 1. In this way, the waterwheel will serve as a low lift water raising apparatus for producing circulation of a large amount of water at a very high efficiency without any backflow, the said apparatus thus being freed of drawbacks in the effect of aeration.

In that way, the low temperature heavy water at the bottom of the water tank can undergo repetition of the circulation (as indicated by the arrows 16 in Fig. 2) in which the water is sucked up due to the effect of the communicating vessel, is aerated, while being carried on or by the waterwheel, and is then, discharged on the water surface on the opposite side of the waterwheel: this achieves an agitating effect no less powerful than that achieved by the air blowing device at the bottom of the water tank. For this agitation on the small head difference between both sides of the vertical diaphragm 1 5 affects the system as regards the consumption of the potential energy.

Thus, such consumption of potential energy as required for counteracting the total pressure of the water depth in the air blow-off at the bottom of the water tank is entirely spared, the consumption of potential energy in this apparatus being one several tenths of that in the water-bottom blowoff method.

Figs. 6 and 7 illustrate one of the best uses of the waterwheel device of this invention which is its use in a sewage treatment plant.

The aerator waterwheel 1 is mounted on the top of a treating tank 10 at such a level that the tube wings 2 at the lower level are immersed in the water to be treated. Then inside the treating tank 10, there are provided a vertical diaphragm 21 directly beneath the aerator waterwheel 1, an arcuate diaphragm 22 contiguous or continuous to the top of this diaphragm 21 , following closely along the outer circumference at the bottom of the aerator waterwheel 1, and a screen 23 below the bottom of the vertical diaphragm 21 , so that by the turning of the aerator waterwheel 1, a circulating water flow is induced as shown by the arrows 24 in Fig. 6.Inside one the chambers 1 Oa of the treating tank 10 bisected by the vertical diaphragm 21, a large number of filter media 25 made of a synthetic resin are disposed in such an amount that they are suspended in the water over the range trom the top of the screen 23 to the water surface.

The filter medium 25 made of a synthetic resin is formed with a synthetic resin net tube. Such filter media are put in to the treatment tank 10 to compose a floating submerged filter bed 26, on which solid organic matters, if contained in the water to be treated, are to be captured.

Accordingly, when the aerator waterwheel 1 and the submerged filter bed 26 formed with synthetic resin filter media 25 are jointly utilized, a biological film filter tank holding aerobic microbes may be provided, in which the lower part of one chamber 1 Oa also serves as the sludge settling tank, affording an extremely large area of contact between the aerobic microbes and the water to be treated. Thus a sewage treatment plant which is very compact, has high treating capacity and is low priced can be offered.

A preferred synthetic resin filter material for the medium 25 to form the submerged filter bed 26 is hard polyethylene having preferably a specific gravity of about 0.95 since this material allows easy separation from the sludge, cleaning of the clogged parts and handling. A flat laminated reticular small lump having a side about 50 mm which is formed of a net of thin unit wires of about 0.3 mm diameter as its base material, with the unit wires being thin but hard, disposed at intervals of 8-3 mm both vertically and laterally, and having no large cavities inside, is desirable.

Ideally, such media individually should not entangle in air or under water, but slide easily on each other, thus dispersing inside the water tank, showing small resistance to water passage, and allowing the relative positions between them to be altered even by very small water flow and pressure.

Several examples of the filter medium 25 which satisfy these requirements are shown in Figs. 8 to 14.

In the first example shown in Figs. 8 and 9, a hard polyethylene net tube 27 is formed with thin unit wires as the material is cut to lengths of about 50 mm. Each piece is flattened, folded in two, and then, heat-welded as at 28 of the overlapped part to be held in that shape.

In the example of Figs. 10 and 11, a net tube 27 similar to the above one is flattened; both side parts are respectively folded back onto one surface, and abutted at their edges; and in this state, the abutted edges of respective folded back parts are heat-welded at 28.

In the example shown in Fig. 12, a net tube 27 in the flattened state is folded back at both side parts onto opposite surfaces to be folded in three, and the overlapped part is heat-welded as at 28.

The overlapped part may be heat-welded at the location indicated by the illustrated arrows.

In still another example which is not shown in the drawings, a net tube 27 in the flattened state is folded in four by successively rolling in, and the overlapped part is heat-welded in the same way as above described.

In the example of Fig. 13, two of said flattened net tubes 27 are superimposed one upon the other, and the center of the overlapped part is heat-welded as indicated at 28. The number of net tubes 27 to be superimposed one upon another is not restricted to two, but three or more tubes may be freely chosen to meet the situation.

As hereabove described, besides the quite outstanding features in the aeration effect and energy saving, the described aerator waterwheels 1 are advantageous in that the use of conventional air blow-off devices and the piping work therefor may be avoided; they are free of the troubles involved in the supervision of operation of air compressors or the check and repair for clogging of the air blow-off device that occurs with passage of time, no noise is produced running at a low speed, they have high strength and durability, are very simplified and sturdy, trouble free and economic due to their low price, and their maintenance costs are low.

This aerator water wheel 1 is effective as a waterwheel 1 for cooling hot or warm water without any modification. The conventional system of raising a large amount of heavy water to the top of a water cooling tower, and sprinking it, has a lower efficiency than the water bottom air blow-off, and consumes a large amount of energy.

The aerator waterwheels described herein may be arranged in series or parallel all over the tank to be cooled; the tank is provided with a simple cover; then, adoption of the forced draft system of blowing in air horizontally from one side, and discharging it from the other side, may be readily practiced. This system requires less air blowing pressure than the cooling tower system. The energy saving effect both with water pumps and blowers is large; use of large amounts of contact media to be disposed in the tower is avoided, and the water cooling plant itself can be built at very low costs. The apparatus described herein provides for a greater saving of energy than the fountain type cooling tank.

The waterwheel systems described require minimal energy consumption without reducing the effect of agitation and aeration of water, require no piping work, avoid any trouble in monitoring the operation of the air compressor and of making checks on and repairs of the air blowing device due to clogging which will take place with passage of time, are not noisy during operation, have excellent strength and durability, are highly economical, are manufactured and maintained at low costs, and have a wide range of uses including sewage treatment, oxygen supply to fishponds.

cooling of hot and warm water, etc..

Claims (24)

1. An aerator waterwheel including a rotary shaft, two end plates fixed in spaced apart relation to said shaft, and a plurality of porous cylindrical tubes made of a synthetic resin encircling the shaft in parallel therewith and with both ends of each tube extending between and secured to the end plates.

2. An aerator waterwheel as claimed in claim 1, wherein the ends of the tubes are securely held onto the end plates at or near their outer perimeters.

3. An aerator waterwheel as claimed in claim 1 or 2, wherein each cylindrical tube has undulating rough surfaces in and outside thereof which are very coarse, and is provided with a blind wall part.

4. An aerator waterwheel as claimed in claim 3, wherein each cylindrical tube is rigidly held between the end plates in such a way that its blind part can play the role of an effective scooping board.

5. An aerator waterwheel as claimed in any one of claims 1 to 4, wherein at least one cylindrical tube is a composite tube formed of two porous cylindrical tubes integrally welded together at their abutting peripheries.

6. An aerator waterwheel as claimed in any one of claims 1 to 7, wherein each cylindrical tube is rigidly secured to the end plates by fitting the ends of the cylindrical tube on cylindrical projections provided on the end plates.

7. An aerator waterwheel as claimed in any one of claims 1 to 6, wherein the cylindrical tubes are of honeycomb configuration.

8. An aerator waterwheel as claimed in any one of claims 1 to 6, wherein the cylindrical tubes are perforated.

9. An aerator waterwheel as claimed in any one of claims 1 to 6, wherein the material of the cylindrical tubes is in the form of a mesh.

10. An aerator waterwheel system including an aerator waterwheel as claimed in any one of claims 1 to 9, wherein the waterwheel is rotatably disposed near the water surface of a water tank so that the cylindrical tube(s) at the bottom of the waterwheel are immersed in the water and means for driving the waterwheel at such a range of rotational speeds that heavy splashing will not occur.

11. A sewage treatment plant comprising an aerator waterwheel system including an aerator waterwheel having a rotary shaft, two end plates rigidly secured to the rotary shaft in spaced apart relation, and a plurality of porous cylindrical tubes made of a synthetic resin encircling the rotary shaft in parallel to the outer circumference thereof, the aerator waterwheel being rotatably and horizontally disposed near the water surface of the water tank so that the cylindrical tube(s) at the bottom of the waterwheel are immersed in the water, the said aerator waterwheel being capable of being driven at such a range of rotational speeds that heavy splashing will not occur, there being disposed in the said water tank, a vertical diaphragm beneath the bottom of the aerator waterwheel and an arcuate diaphragm contiguous or continuous to the top of the said diaphragm and following closely the profile of the outer circumference of the waterwheel thereby to induce a circulating water flow in the water tank as the waterwheel turns, and contact or filter media made of a synthetic resin are disposed in the tank to be in the circulating water flow.

12. A sewage treatment plant as claimed in claim 11, wherein the filter medium is formed as a laminated, reticular, flat small lump with porous net tubes formed of thin unit wires.

13. A sewage treatment plant as claimed in claim 11, wherein the filter medium is formed as a laminated, reticular, flat small lump with honeycombed net tubes formed of thin unit wires.

14. A method of aerating or cooling water characterized by slowly rotating a waterwheel including a plurality of porous tubes such that the lowermost tube or tubes at any one time is or are immersed in the water, the speed of rotation being such as to avoid heavy splashing arising from the rotation of the waterwheel through the water.

1 5. An aerator waterwheel substantially as hereinbefore described with reference to Figs. 1 to 3 of the accompanying drawings.

16. An aerator waterwheel substantially as hereinbefore described with reference to Figs. 1 to 4 of the accompanying drawings.

17. An aerator waterwheel substantially as hereinbefore described with reference to Figs. 1 to 5 of the accompanying drawings.

18. An aerator waterwheel system incorporating a waterwheel as claimed in any one of claims 1 to 8, 15 to 17.

19. A sewage treatment plant incorporating an aerator waterwheel as claimed in any one of claims 1 to 8 and 15 to 17 or an aerator waterwheel system as claimed in any one of claims 11 to 13 and 18.

20. A sewage treatment plant substantially as hereinbefore described with reference to Figs. 6 and 7 of the accompanying drawings.

21. A sewage treatment plant substantially as hereinbefore described with reference to Figs. 6 to 9 of the accompanying drawings.

22. A sewage treatment plant substantially as hereinbefore described with reference to Figs. 6, 7, 10 and 11 of the accompanying drawings.

23. A sewage treatment plant substantially as hereinbefore described with reference to Figs. 6, 7 and 12 of the accompanying drawings.

24. A sewage treatment plant substantially as hereinbefore described with reference to Figs. 6, 7 and 13 of the accompanying drawings.