CA1093117A - Device and process for the aeration of water - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A water aeration device as described in which the water-distributing spray tube which delivers the water onto the surface of an aeration tank is provided with a pair of plates extending from the tube to at least the surface of the water. The plates or baffles are positioned on either side of openings in the delivery tube and define a channel having access to ambient air for spraying water onto the surface of and mixing with the water contained in the aeration tank itself.
The plates are preferably flexible and provide for suppression of noise and/or water overspray conditions previously encountered.
In another embodlment provides in tubes concentrically to the openings in the delivery tube and have a diameter in excess of the maximum diameter of the water jets and are extending below the water surface of the tank.

Description

~93~7 This invention relates to apparatus eor the aeration of w~ter, comprising an aeration tank and recycling rneans ~or pumping water r,ut o~ the tank and returning it ~o the said tank through at loaqt ons tube containing discharge oriflces disposed above the normaL water level in the t~nk.
Such apparatus is used ~or the purliicatlon o~ waste water in the pre~ence o~ biologically active sludge.
In some embodiments oP such apparatus Jets o~ water strlke the water sur~ace in the tank at a particular angle. In particuler the blolo-gically active sludge needed in the purli~tcation Oe the water may be maintained in suspension by a tubular propeller, the impingement e~ect o~ the ~ets ensuring that the oY.ygen requlred ior purl~ication oi the ~ludge is introduçed beneath the sur~ace oi water in the tank.
In another embodiment, by appropriate selection o~ the implnge-ment angle o~ the jets and also Oe the output veloclty oi water erom the tank, the required uptake o~ oxygen is en~ured and also the sludge is =aintained in suspenslon. This embodiment i3 described in~Pakent spe¢i~ication 1.458,302, Such devices however su~i'er from disadvantage~ In particular due to the large amounts oi water to be recy¢led in the aeration tank, a large number oi' water jets are required. With a large in~tallation the operation oi' a large number o~ jet3 is noi~y. Furthermore the use oi jets in qu¢h installations tend~ to generate a large volume o~ mist in the atmosphere surroundlng th0 tank.
The inventiotl i~ directed to an arranKometlt lor ths aeratlon o~
water uslng water Jet~, whereby ~uch diY~vantaees are mltlgate~.
The invention provl~o~ apparatll~ eOr th~ aoratlon Oe wate~, comprising an aeration tank and recy¢llnK means ~or pumpln~ water out o~
the said tank and returninK it to the ~aid tank through at loast one tube containing dis¢harge orieice~ dl~po~ud above th~ normal wator lovel in the tank, v~herein one or more guard~ are ~ltted on the said eeed tube(s) adJ~aent th~ orl~lc~ nd whloh r~a~h ~t leaot onto tha ~urra~o ~31~7 of the water contained in the t~nk, ~nd disposed so as to ~e clear of the jets of water ~merying ~rom the ~aid orifices, one or more ports being provided in the said yuards through which air can be drawn towards the said water jets The guards consist of plates itted to the feed tube and parallel to the centre line thereof on either side of -the outflow openings and extending to the water surface, at least one air inlet port being provided thèrein.
The position of the air inlet ports is not critical provided they are abo~e the water surface. Very effective suppression of noise and mist during operation is achieved by providing the ports in the guard near the outflow openings. The air inlet ports must be sufficiently large to admit enouyh air to the jets.
The said ports are preerably located on the side of the guards facing the water surface. In some instances they may also be placed at the ends of the plates. They are preferably provided with noise silencing means.
In another embodiment of the invention a tube of a diameter in excess of the maximum diameter of the water jet at the water surface is disposed concentrically with each outflow orifice through which the water is recycled into the aeration tank, the said tube extending to below the water surface and being provided with a port through which air can be drawn in. The diameter of thi~ tube i~ pre~era~l~ thre~ tirn~ th~ e~Eectlve diameter o the out10w opening. rrhl~ ha~ the advanta-3e that the efficiency of the d0vic~ Ln no way lrnpair~d, a particu-larly rnarked reduction in noi~e ~nd ml~t orrnation ~alng effected.
The guard~ u~ed accordiny to the lnvention are provided ~or the purpo~e o~ reduciny no$~e nui~ancc and mi~t ormation to a minimum, the effect of the water j~t~ aE de~cribed in Vnited Kingdom Patent Specification l,~58,302 being changed to the ~ 3 ~

1439~3~7 least possible extent. This is ~chieved by selecti~g the diameter of the silencer so as to be suf~iciently large, the i~nersed length of the silencer being kept at a minim~n. The device according to the invention thus does not operate a~ an injector.
The out1Ow orifices may be of any known d~sign. In a preferred design the outflow orifices are holes in the feecl tube which cause the water jets to strike the water surface at an angle of from 5 to 60, preferably from 4U to 60.
The guards 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 o 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 o the material can experience buoyancy in the water.
In a special embodiment of the invention the port 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 thi~ 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 ~he accompanying drawinyr~, o~ whlch:
Figure 1 is a per~peckive view o~ orle cl~odlrnent of the invenkion in whLch the guardl~ compri~e a pair Oe plat~
Figure 2 i~ a tran~v~rr~ ~cctlon o~ the arrangem~nt of Figure 1, Figure 3 i~ a top plan view o~ an aeration tank having two feed tube~ fitted ~Iith yuard~ according to the invcntion, and 1~33L~

F.igure 4 is a transverse section of an arrangement in which the guards comprise tubes.
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 fl ~

1 has two guards in the shape of plates 2 and 3 itted ~ne on each side o~
the supply pipe ancl one of the said guards floating on the surface of water in a tank or clipping a small distance into the water. The feed tu~e is prc~
vided with outflc~7 orifices 5. Jets of water flc~7 frc~m these oxifices strik-ing the water surface at an angle between 5 and 60.
From Figure 2 it is clearly seen that the guards 2 and ~ dip for a small distan oe into the water. At rec~ular intervals plate 2 i5 prDvicled with air inlet ports 6. Arrow 7 indicates the direction of flcw of the water.
Referring to Figure 3 a tank 8 is fittecl with suppl~ and discharge lines 9 and 10, two feed tubes 1 connected to pu~ps 11 which punp ~7ater out of the tank and deliver it to tubes 1. Fresh waste water feed line 9 ter~
m mates in the sectlon line of pump 11. The ~eed tubes 1 are as in Figure 1 and 2 fitted with guards. In Figure 3 only guard 3 is ~hcwn. The air inlet ports are in the g~ard but not shown. In the feed tubes there æe a numker of outflow orifices 5 Ln the shape of holes.
Referring to Fig~re 4, there is disclosed an e~cdirrent in which the guards comprise tubes 20 having air inlet ports 21. The tukes 20 surrcund the outflow orifices 5 and are spaced therefrom. The tukes 20 project into the water surface b~ a distance a.
The following practical Exa~les of the invention are provided.
Exa~ple I
Measure~ents were made on a water jet striking the water surface at an angle of 60 in a cylindrical tank with a volume of 1 m3. The diameter d of the outflow orifices ~1as 23.6 ~. !
The accc~r~anyiny Tahle ~hc~3 ~h¢ m~a~u~ing r~sult~ oht~ncd with guards in the ~hape of ~ylindrical tu~ 20 o~ v ~yLrlg dL~(~t~r coaYl~lly di~-~osed with the outfl~w c~P3ning~3. r~ :Ln~¢rnal d~ t¢r d of thl~ cJuurd and the immers3d length a ~r~ vari~d. ~r~ of~lc ~n~ o~ a ~7ater j~t~ ~ut gu~rd was asses~ed at 1()0%.

C

Test Dia D o~ out~low Dla d a ~mm) Oxygenation opening (n~) tmm) e~iciency (%) l 23.6 - - lO0

2 23.6 35 50 77

3 23.6 53 50 g3

4 23.6 53 20 97 23 6 72 50 g9 In all tests with the guard, the noise had at lea~t been reduced to hal~
thus falling below the noise level o~ nearby equipMent and rendering a further reduction unn~cessary.
Also mist ~ormation was strongly reduced. From the Table lt appears that at a d/D ratio in exce~s o~ three, the ei'~iciency withln the mea-suring error wa~ equal to the orlginal e~ii¢iency.
Without guards, mist ~ormation appsared to be strongly dependent on-the angle at which the water ~et strikes the water sur~ace. At very small angle~, i.e. smaller than 20 C, mist was i'ormed. At angles oP
between 40 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 o~ a device as described with re~erence to Figs. l and 2, a number o~ test~ have been carried out, both with and without guards. Dispo~ed in ieed tube l were sevqn outi'low openings 5, each having a diameter o~ l~0 mm. 'rh~ water Jot~ ~truck tho wator ~uri'uce at an angle o~ 60 , The oxygenatlon e~iciency withuut ~uar~s wa~ a~essq~
at 100 %. Under un~avourablo weath~r condition~ somo ml~t wa~ tormod.
With guard~ mounted, the oxygenation o~Lci~n¢y wa~ 97 '~, whlch, 1n vlew o~ the accuracy oi thi~ type o~ mea~uremont~, doo3 not ~l~nl~laantly di~er ~rom lO0 %. The noi~e produced by the water jots was at least lO dB(A~ lower than without guards and no ml~t was tormq~ ov~n undor very un~avourable wheater condltlon~.

Claims (9)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Device for the aeration of waste water containing biologically active sludge in suspension, comprising an aeration tank and recycling means for pumping water out of the said 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, wherein one or more guards in the shape of plates, which are attached to the feed tube parallel to the centre line thereof on either side of the outflow orifices, are fitted of the said feed tube(s) adjacent the said orifices and which reach at least onto the sur-face of the water contained in the tank, and disposed so as to be clear of the jets of water emerging from the said orifices, one or more ports being provided in the said guards through which air can be drawn towards the said water jets.

2. Apparatus according to Claim 1 wherein the air inlet port(s) are disposed adjacent to the water outflow openings.

3. Apparatus according to Claim 2, wherein the said port(s) are located on that side of the guard that is facing the water surface.

4. Apparatus according to Claim 1, wherein the said port(s) are disposed at the ends of the plates.

5. Apparatus according to Claim 1 or 2 or 3, wherein the said port(s) are provided with silencing means.

6. Device for the aeration of waste water containing biologically active sludge in suspension, comprising an aeration tank and recycling means for pumping water out of the said 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, wherein one or more guards in the shape of tubes are attached coaxially with the outflow openings which tubes have a 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.

7. Device according to Claim 6, characterized in that the diameter of the tube is at least three times the effective diameter of the outflow opening.

8. Apparatus according to Claim 1 or 2 or 3, wherein the said dis-charge 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 60°.

9. Device according to Claim 1 or 2 or 3, characterized in that the ports for drawing air to the water jets are provided with means for cutting off the entry of air.