GB1572838A

GB1572838A - Device and process for the aeration of water

Info

Publication number: GB1572838A
Application number: GB18718/77A
Authority: GB
Original assignee: Stamicarbon BV
Current assignee: Stamicarbon BV
Priority date: 1976-05-06
Filing date: 1977-05-04
Publication date: 1980-08-06
Also published as: CH617870A5; DD130471A5; FR2350305B1; ZA772677B; AU506979B2; LU74888A1; FR2350305A1; ATA317577A; JPS52135566A; IT1079647B; DE2720447A1; NL7704827A; CA1093117A; SE7705216L; SE422455B; AU2486877A; ES458506A1; AT351467B; BE854304A

Abstract

In order to suppress troublesome noise and the formation of mist at the feed pipe (1) around the outlet orifices (5) through which the water is returned to the aeration tank, one or more covering means (2, 3) are provided. These extend at least as far as the water surface and do not touch the profile of the water jets. In addition, at least one orifice (6) is provided through which air can be drawn in. <IMAGE>

Description

(54) DEVICE AND PROCESS FOR THE AERATION OF WATER (71) We, STAMICARBON B.V., a Netherlands Limited - Liability Company, of P.O. Box 10, Geleen, The Netherlands, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to apparatus for the aeration of water, comprising an aeration tank and recycling means for pumping water out of the tank and returning it to the said tank through at least one tube containing discharge orifices disposed above the normal water level in the tank. Such apparatus is used for the purification of waste water in the presence of biologically active sludge.

In some embodiments of such apparatus jets of water strike the water surface in the tank at a particular angle. In particular the biologically active sludge needed in the purification of the water may be maintained in suspension by a propeller, the impingement effect of the jets ensuring that the oxygen required for purification of the sludge is introduced beneath the surface of water in the tank.

In another embodiment, by appropriate selection of the impingement angle of the jets and also of the output velocity of water from the tank, the required uptake of oxygen is ensured and also the sludge is maintained in suspension. This embodiment is described in Patent Specification 1,458,302.

Such devices however suffer from disadvanrages. In particular due to the large amounts of water to be recycled in the aeration tank, a large number of water jets are required.

With a large installation the operation of a large number of jets is noisy. Furthermore the use of jets in such installations tends to generate a large volume of mist in the atmosphere surrounding the tank.

The invention is directed to an arrangement for the aeration of water using water jets, whereby such disadvantages are mitigated.

The invention provides apparatus for the aeration of water, comprising an aeration tank and recycling means for pumping water out of the said aeration tank and returning it to the said tank through at least one feed tube containing discharge orifices disposed above the normal water level in the tank, wherein one or more guards are fitted on the said feed tube(s) adjacent the orifices and which reach at least onto the surface of the water contained in the tank, and disposed so as to be clear of the jets of water emerging from the said orifices, air inlet ports being provided in at least one of the said guards through which air can be drawn towards the said water jets.

The guards used according to the invention are provided for the purpose of reducing noise nuisance and mist formation to a minimum, the effect of the water jets as described in Patent Specification 1,458,302 being changed to the least possible extent. This is achieved by selecting the diameter of the silencer so as to be sufficiently large, the immersed length of the silencer being kept at a minimum. The device according to the invention does not operate as an injector.

In one embodiment of the invention the said guards are plates which are attached to the feed tube and parallel to the centre line thereof on each side of the outflow orifices.

The position of the air inlet ports should be above the water surface. Very effective suppression of noise and mist during operation is achieved by providing the ports in the guard adjacent the outflow openings. The air inlet ports must be sufficiently large to admit enough air to the jets.

In another embodiment of the invention the said guards are tubes attached to the said feet tube(s) coaxially with the outflow openings therein, and are of diameter in excess of the maximum dfameter of the water jets at the water surface, the said tubes extending to below the water surface and being provided with ports through which air can be drawn in. The diameter of this tube is preferably three times the effective diameter of the outflow opening. This has the advantage that the efficiency of the device is in no way impaired, a particularly marked reduction in noise and mist formation being effected.

The outflow orifices may be of any known design. In a preferred design the outflow orifices are holes in the feed tube which cause the water jets to strike the water surface at an angle of from 5 to 60 , preferably from 400 to 600.

When the guards are in the form of plates which are attached to the feed tube and disposed parallel to the centre line thereof on either side of the outflow orifices, they are preferably made of an elastomeric material e.g. an EPDM rubber or a polyolefine, or material which is a mixture thereof and is particularly made of a thermoplastic rubber obtained under the Trade Mark KELTAN TP. Plates made of elastomers have some flexibility, so that they can adapt to different water levels in the aeration tank, and due to the low specific gravity of the material can experience buoyancy in the water.

In a special embodiment of the invention the ports for drawing air to the water jets are provided with means for cutting of the supply of air to the water jets. The advantage of this is that with this embodiment it is possible to perform an anaerobic purification of the waste water before or after the aerobic purification.

The invention is hereinafter particularly described and illustrated in the accompany drawings, of which: -Figure 1 is a perspective view of one embodiment of the invention in which the guards consist of a pair of plates, Figure 2 is a transverse section of the arrangement of Figure 1, and Figure 3 is a top plan view of an aeration tank having two feed tubes fitted with guards according to the invention.

Referring to the drawings, Figures 1 and 2 represent a feed tube 1 connected with means (not shown) for pumping water out of a tank.

Feed tube 1 has two guards in the shape of plates 2 and 3 fitted one on each side of the supply pipe and one of the said guards floating on the surface of water in a tank or dipping a small distance into the water. The feed tube is provided with outflow orifices 5. Jets of water flow from these orifices striking the water surface at an angle between 5 and 600.

From Figure 2 it is clearly seen that the guards 2 and 3 dip for a small distance into the water. At regular intervals plate 2 is provided with air inlet ports 6. Arrow 7 indicates the direction of flow of the water.

Referring to Figure 3, a tank 8 is fitted with supply and discharge lines 9 and 10, two feed tubes 1 connected to pumps 11 which pump water out of the tank and deliver it to tubes 1.

Fresh waste water feed line 9 terminates in the suction line of pump 11. The feed tubes 1 are as in Figures 1 and 2 fitted with guards.

In Figure 3 only guard 3 is shown, The air inlet ports are in the guard, but not shown.

In the feed tubes there are a number of outflow orifices 5 in the shape of holes.

The following practical Examples of the invention are provided.

Example 1.

Measurements were made on a water jet striking the water surface at an angle of 600 in a cylindrical tank with a volume of 1 m5.

The diameter d of the outflow orifices was 23.6 mm.

The accompanying Table shows the measuring results obtained with guards in the shape of cylindrical tubes of varying diameter coaxially disposed with the outflow openings.

The internal diameter d of the guard and the immersed length a were varied. The efficiency of a water jet without guard was assessed at 100%.

Dia D of outflow Diad Oxygenation Test opening (mm) (mS a (mm) efficiency (eye) 1 23.6 - - 100 2 23.6 35 50 77 3 23.6 53 50 93 4 23.6 53 20 97 5 23.6 72 50 99

In all tests with the guard, the noise had at least been reduced to half, thus falling below the noise level of nearby equipment and rendering a further reduction unnecessary.

Also mist formation was strongly reduced.

From the Table it appears that at a d/D ratio in excess of three, the efficiency within the measuring error was equal to the original efficiency.

Without guards, mist formation appeared to be strongly dependent on the angle at which the water jet strikes the water surface. At very small angles, i.e. smaller than 200 C, mist was formed. At angles of between 400 and 60 , a reduction was already achieved and nuisance was experienced only under special weather conditions, such as strong breeze etc.

Example 2.

With the aid of a device as described with reference to Figs. 1 and 2, a number of tests have been carried out, both with and without guards. Disposed in feed tube 1 were seven outflow openings 5, each having a diameter of 130 mm. The water jets struck the water surfr.ce at an angle of 60". The oxygenation efficiency without guards was assessed at 100%. Under unfavourable weather conditions some mist was formed. With guards mounted, the oxygenation efficiency was 97 /.

which, in view of the accuracy of this type of measurements, does not significantly differ from 100%. The noise produced by the water jets was at least 10 db(A) lower than without guards and no mist was formed even under very unfavourable weather conditions.

WHAT WE CLAIM IS: 1. Apparatus for the aeration of water, comprising an aeration tank and recycling means for pumping water out of the said aeration tank and returning it to the said tank through at least one feed tube containing discharge orifices disposed above the normal water level in the tank, wherein one or more guards are fitted on the said feed tube(s) adjacent the said orifices and which reach at least onto the surface of the water contained in the tank, and disposed so as to be clear of the jets of water emerging from the said orifices, air inlet ports being provided in at least one of the said guards through which air can be drawn towards the said water jets.

2. Apparatus according to Claim 1, wherein the air inlet ports are disposed in the said guard(s) adjacent to the water outflow openings.

3. Apparatus according to Claim 1 or Claim 2, wherein the said ports are provided with silencing means.

4. Apparatus according to any of Claims 1 to 3, wherein the said guards are plates which are attached to the feed tube and parallel to the centre line thereof on each side of the outflow orifices.

5. Apparatus according to any of Claims 1 to 3, wherein the said guards are tubes attached to the said feed tube(s) coaxially with the outflow openings therein and are of diameter in excess of the maximum diameter of the water jets at the water surface, the said tubes extending to below the water surface and being provided with ports through which air can be drawn in.

6. Apparatus according to Claim 5, wherein the diameter of the tube is at least three times the effective diameter of the outflow opening.

7. Apparatus according to any of Claims 1 to 6, wherein the said discharge orifices are disposed in the said tube to provide water jets striking the surface of water in the tank at an angle between 5 and 600.

8. Apparatus according to any of Claims 1 to 7, wherein the ports for drawing air to the water jets are provided with means for cutting off the entry of pir.

9. Apparatus according to Claim 1, substantially as hereinbefore described and illustrated with reference to the drawing and/or the Examples.

10. A process for the aeration of water by means of water jets, characterized in that apparatus according to one or more of Claims 1 to 9 is employed.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. in excess of three, the efficiency within the measuring error was equal to the original efficiency. Without guards, mist formation appeared to be strongly dependent on the angle at which the water jet strikes the water surface. At very small angles, i.e. smaller than 200 C, mist was formed. At angles of between 400 and 60 , a reduction was already achieved and nuisance was experienced only under special weather conditions, such as strong breeze etc. Example 2. With the aid of a device as described with reference to Figs. 1 and 2, a number of tests have been carried out, both with and without guards. Disposed in feed tube 1 were seven outflow openings 5, each having a diameter of 130 mm. The water jets struck the water surfr.ce at an angle of 60". The oxygenation efficiency without guards was assessed at 100%. Under unfavourable weather conditions some mist was formed. With guards mounted, the oxygenation efficiency was 97 /. which, in view of the accuracy of this type of measurements, does not significantly differ from 100%. The noise produced by the water jets was at least 10 db(A) lower than without guards and no mist was formed even under very unfavourable weather conditions. WHAT WE CLAIM IS:

1. Apparatus for the aeration of water, comprising an aeration tank and recycling means for pumping water out of the said aeration tank and returning it to the said tank through at least one feed tube containing discharge orifices disposed above the normal water level in the tank, wherein one or more guards are fitted on the said feed tube(s) adjacent the said orifices and which reach at least onto the surface of the water contained in the tank, and disposed so as to be clear of the jets of water emerging from the said orifices, air inlet ports being provided in at least one of the said guards through which air can be drawn towards the said water jets.