Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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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
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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
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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%.
-- 5 --
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~.
