CA1205929A

CA1205929A - Apparatus for aerating water bodies or wastewater

Info

Publication number: CA1205929A
Application number: CA000433016A
Authority: CA
Inventors: Reinhart V. Nordenskjold
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-07-23
Filing date: 1983-07-22
Publication date: 1986-06-10
Also published as: DE3227672A1; SE8304058D0; SE8304058L; FI832674A; DE3227672C2; FI74694C; FI74694B; FI832674A0; NO832687L; DK322083D0; DK322083A

Abstract

ABSTRACT OF THE DISCLOSURE
An apparatus for aerating water bodies, such as ponds, or of wastewater contained in a bioactive sludge basin, said apparatus comprising at least one air supply duct floating on the water and anchored as by means of a rope to opposite banks, and a plurality of spaced aeration units branching off of said air supply duct and extending down into the water, each aeration unit including an aeration body for instance in the form of a ceramic "candle" for introducing the air into the water, and a connection duct attached to the air supply duct for connecting it to said "candle". The invention enables an apparatus of this type to be readily installed and uni-versally employed without impairment of its function by providing that each of said connection ducts is formed as a flexible hose.

Description

3~
1 Field o the Invention . The present invention relates to an apparatus for aerating water bodies, such as ponds, or wastewater con-tained in a bioactive sludge basin, and more particularly to such an apparatus comprising at least one air supply duct floating on.the water and anchored to opposite banks as by means of a.xope, and a plurality of aeration units connected to said supply duct at intervals and extending into the water, each aeration unit compris.ing an aeration body in the form.for instance of a ceramic candle for injecting air into the water, and a connection duct connecting said air supply duct to said aeration body.
Backgrol~nd of the Invention In order to maintain the biological equilibrium of stagnant water bodies such as by desludging them, or for operating bioactive sludge basins for the biological purification of wastewater, apparatus oE the type referred to above is used for injecting air into the water in the form of fine bubbles, the ducts connected to the air supply duct ~or supplying air to the candles being generally formed as.rigid metal tubes.
For starting.operation of a wastewater purifi-cation basin of this type, the basin is initially filled with normal water up to a certain level, whereupon the aeration apparatus is installed with the aid of a con-siderable number of personnel, so that the candles rest on the ground and the connection ducts extend obliquely upwards due to the low water level. Apart from the fact ., ,. ~

1 that handling of the apparatus during its installation is rather cumbersome due to its considerable weight, it frequently happens that the candles.res-ting on the ground or theix connections are damaged. 'rhere is also the dan~er that the obliquely extending connection ducts of adjacent parallel air supply ducts become entangled with each other. For the above reasons, the installati.on of apparatus of this type in a wastewater purification basin is rendered rather difficult.
If.apparatus of the type described is used.for aerating a pond or a.lake, the candles.attached to the rigid connection ducts may ~urrow-themselves into sludge hills encountered on the loor of the water body and get clogged.thereby. This results in.no.air being actually injected at those.locations whereat the injection of air would be particularly important for decomposi*ion of the sludge hills. It would of course be possible to employ shorter connection ducts in the range ~f such sludge hills. Apart from the increased costs, however;
replaçement of the connection ducts in the~ water is rather cumbersome. After such.a sludge hill.has been partially decomposed, the candles would moreover be spaced at too great a distance from the sludge hill, i.e. they would no longer be in a particularly ef~ective position.
Another difficulty is frequently encountered in winter, when a pond or lake ~reezes over and the water is drained, as this results in the ice cover b~ing . .

. ~

s~

1 directly supported by the connection ducts, so that the latter may become bent, and the candles resting on -the floor of the water body are damaged.
In view of the described difficulties, apparatus of this type is only conditionally suited for aerating ponds or lakes, and at least has to be adapted to the given conditions a*.considerable expense.
It is an,object of the present invention to improve an apparatus of.the type- set forth in the introduction ; 10 in such a manner that it may,be readily installed and universally employed without its function.being impaired.

SUMMARY OF THE INVENTION
In order.to attain this obiect the invention provides that each connection duct is formed as a ~ flexible hose.
: -This provision greatly facilitates the installa-tion of the apparatus in a wastewater purification basin initially filled only partially with water. In this

2() case,. the flexible hoses forming the connection ducts adapt themselves to the low water level by bending without thereby exerting any significant force on the candles resting on the floor. It is moreover even possible to install.the înstallation in a still dry wast~water purifi-cation basin and to subsequently fill the basin withwater without the danger of parts of'the apparatus being damaged in the process~

~;'`' `
..

l The above noted provision also permits the apparatus to be readily employed for aerating a pond or a lake, even if there are sludge hills on the floor of the water body. In this case,-the candles slide over the surface of the sludge hill without burrowing thereinko.
As a result, ~.he candles do not become clogged, so that they can perform their function without hindrance. As thP
sludge hills are progressively decomposed, the candles lying on their surfaces merely sink down together therewith, so as to always remain in a favourable operating position.
If in winter a lake or pond provided with the apparatus of the type described freezes over and the water is drained, the apparatus is not endangered~ as the flexible hoses forming the connection ducts are not able to transmit the weight of the ice cover to the candles resting on the floor of the pond or lake.
It is a further particular advantage of the invention that the flexible hoses forming the connection ducts may be made of a corrosion-resistant synthetic material, so that the lifespan of such a flexible hose-duct cannot even be impaired by aggressive wastewater.
In aerating wastewater in a bioactive sludge basin it is o importance that the air be injected as uniformly as possible over the entire area of the bio-active sludge basin. In the known apparatus r in which the connection duGts connected to the air supply duct ,~ .

1 were in the form of rigid metal tubes with the aeration bodies attached to the lower ends thereof. and in which the aeration bodies were disposed parallel to the air supply duct,, the air exiting therefrom more or less closely above $he floor caused the aeration bodies to drift back and forth over a certain drifting range within the basi~, as long, as the air supply duct was not kept under tension by . the anchoring ropes, but was able to form a bend. The back and forth drifting movement of the air supply ducts., a plurality of which were generall~ disposed in parallel spaced relationship, resulted in a large-area thorough aeration of the wastewater-and o~.$he bioactive sludge contained therein. . --To .the surprise.even of those skilled in the art~
it has now,been found that this dri~ting movement of the air supply ducts also takes place if the,connection ducts are formed as flexible hoses.. It had rather to.be expected that in this case the drifting aeration bodies would simply escape sideways or-float up.' Quite to the contrary, how~ver, it has been ~ound that the back and forth drifting movement of the aeration bodies is fully ensured even if the aeration bodies are in ground,contact~ Even in this case, th~ reversal of the drifting movement occurs adjacent the reversa]. lines of the air supply ducts,,,which would have been impossible with connection ducts in the form of rigid metal tubes. This advantage is of considerable importance for the cooperation with drifting air supply ducts, as it prevents the aeration strings from getti~g 5 _ , ~%~9z~

1 hung up at obstacles. Any hang~up of the a~ration strings would otherwise result in the collapse of the biological equilibrium as through loss of the ~ioac~ive sludge. This provision thus results in a considerable improvement of the operation of drifting air supply ducts.
In addition, the employ of flexible hoses for the connection ducts results in a considerable simplifi-cation of such apparatus as well as in a reduction of costs, as it is possible to employ commercially available hoses~ preferably of a synthetic material, for this purpose. This advantage is of particular importance in cases in which the length of the connection ducts can only be determined ln situ. In these cases, which frequently occur in connection with natural water bodies, the flexible hoses may be simply cut to the proper lengths.
The invention also permits partially clogged or d~maged aeration bodies-to be readily replaced or cleaned by simply lifting them out of the water, which feat is greatly acilitated by the flexible hose connection ducts.
It is of particular advantage if each connection duct has its ends readily releasably connected to the air supply duct and to the associated aeration body, respectively, as by means of clamping rings or other quick~
release connection means. This provision permits an existing apparatus to be readily adapted to changing con-ditions quickly and without difficulty by simply .

..~, r .` .
~ 1 5~2~9 1 replacing the connection ducts. By this provision it is also.made possible in the case o~ the aeration o.~ ponds or lakes, to initiall~ employ shorter connection.ducts in the vicinity of particularly high sludge mounds, and to replace.them by longer ones as the decomposition of the sludge mou~ds proceeds.

On the other hand, how~ver, the employ o shorter connection.ducts.in this particular case results in a considerable disadvantage, as.the air discharge is in this case reduced by comparison to-aeration bodies having longer connection ducts.
In order to avoid this disad~antage, it may be preferred to inelude throttle means in the conneetion between ~he air supply duct and the connection duct_for adjustably or non-adjustably reducing the air supply to the respective aeration body. In this manner it is possible to reduce.or even to temporarily shut o~f the air supply .to the aerati~n.bodies attached to the longer conneetion ducts, so.that the aeration bodies .attached to the shorter con.neetion ducts adjacent a sludge mound are preferentially supplied with air, whereby decomposition of the sludge mound is substantially.aeeelerated.

, BRIEF DESCRIPTION OF THE DRAWINGS
An embodiment of the invention shall now.be described with reference to the accompanying drawings, wherein:

_ 7 _ , .

~æc~

1 Fi.g. 1 is a fragmentary.elevational side ~iew o a portion of an air supply duct with an aeration unit connected thereto, Fig. 2 is a diagrammatic top view ~f a bioactive sludge purification basin equipped with the apparatus according to the invention, and Fig. 3 is.a longitudinal section through the basin taken along the line III-III in Fig. 2.

DETAILED DESCRIPTION
Shown diagrammatically in Figs~ 2 and 3 is an apparatus 1 for the biological purification of wastewater 2 in a bioactive sludge basin 3, As particularly evident from Fig. 3, the basin is constructed as a simple earth basin.preferably having.a substantially flat bottom ~ 15 for ensuring the aeration of the wastewater and the : bioactive.sludge as closely as possible abov~ the bottom.
On the othe~ hand, however, the bottom does not have to be absolutely flat, but may also be contoured as in the case of ponds or lakes.
: In the exa.mple shown~ basin 3 is equipped with three air supply ducts 5. Each air supply duct consists of a series of hose sections and a plurality of T-junctions 7 (Figure 1) interposed there~etween and having a horizontal cross tube sealingl~ connected at its opposite ends to the adjacent hose sections as ~y means of clamping bands~or other quick-release connection means.

~ ~z~

1 The ends of each air supply duct are connected to ropes or chains 16 by means o which the air supply duct is.attached to posts:8 located adjacent the basin~s edge on the bank of ths water bod~. Each air supply duct thus constitutes an aeration string 4 consisting of the above defined components. The aeration strings ~ are not.kept under tension between the.respective posts 8, but are attached thereto-with a certain slack, so that thèy are able *o.form a wide arch.between the.respective postsj the 1~ latter being located.adjacent the shorter sides of the rectangular basin as shown in Fig. ?.
One end.of. each air supply duct 5 is connected to.an air supply manifold 9 serving.to supply the air.
supply ducts~with c.ompressed.air from a compressor 10.
Between each pair of-adjacent hose sections of each air supply duct.5 ther~ is provided an aeration unit generally designated 6, ~11 of the aeration units 6 being lvcated at regularly spaced intervals.
As evident from Fig. 1, each aeration unit 6 includes one of the T-junctions 7 connected,between adjacent hose sections and equipped with a float 11.
~ach T-junctiQn 7 has a connecting branch or tu~e 17 extending vertically,down into the water bod,y.
Attached to branch 17 is the upper end of ~ connection duct or.conduit formed as a flexible hose 12. In the example shown, the end vf hose 12 is slipped onto branch 17 and secured thereto by means of a clamping band 14.
It is also possible, of course, to connect t~e upper end ';~1 1 of hose 12 to branch 17 by quick-release connection means, for instance by means of a bayonet coupling.
The lower end of hose 12 is slipped onto a tubular stud or branch tube 18 of an aeration body-in the form of a reramic candle 13, and is secured thereto by means of a clamping band in the example shown. Also in this case, a quick-release connection means such as a-bayonet coupling may be employed for connecting.hose.l2 to a~ratio.n body 13.
The aeration body.13 extends parallel to air supply duct 5. It consists of a porou`s material through the pores o~ which the air escapes in the form of small bubbles so as to be e~enly distributed in the water.
Such aeratio.n.bodies are fre~uently designed in the form of ceramic "candles". In this case they are formed as a tube of a`porous ceramic material closed at both ends, so that the supplied compressed air is forced to escape through the fine pores o~ the material.
Figs. 2 and 3 show the employ of.an apparatus comprising a.plurality of air supply ducts 5 in a waste-water basin. The escape of the co.mpressed air results in.
a lateral force acting on the aeration strings, causing them to drift periodically back and forth within a specific area allocated to each aeration string. Fig. 2 shows two end positions of the righthand aeration string, namely, a lefthand end position drawn in full lines, and a righthand end position draw~ in an arcuate phantom line.

~2~

1 As one of the aeration strings reaches its end posi.tion, .the aeration bodies thereof, which during the drifting movement. of the aeration string have been trailing somewhat behind this movement, will swing through under-neath the supply duct so as to subsequently drive theaeration string back in the opposite dir.ection.
In the branch 17 of T--junction 7 for instance :
there may be installed a throttle means permitting the air supply to connection duct 12 to be adjustably or non-adjustably reduced. Such throttIe means may also be auto-matically ad~ustable in response to the air flow there-through .
By the employ of flexible hoses for the connectionducts it is for instance possible, as-explained above, to carry off sludge mounds. To this purpose, thP aeration bodies may be provided.with sludge loosening tools and/or a wear-protective shielding at their lower sides In this case the employ o~ flexible hoses for the connection duc~s practically precludes the danger of the aeration bodies getting stuck.
Under certain conditions it may be advisable to design the connection.duct as a hose which is flexible onl~
in a plane perpendicular to the longitudinal extent of the air supply duct. ..

. ~, .

Claims

The embodiments of the invention in which an exclusive property ox privilege is claimed are defined as follows:

1. An apparatus for aerating a body of water;
comprising at least one air supply conduit which is adapted to float on and extend across an upper surface of the body of water and is adapted to be anchored at its opposite ends so as to have sufficient slack to permit some transverse movement thereof on the surface of the body of water, and a plurality of aeration units which are supported on said supply conduit at spaced intervals therealong and are adapted to extend generally downwardly into the body of water, each said aeration unit including an aeration body for introducing aerated air into the water and a connection conduit providing fluid communi-cation between said air supply conduit and said aeration body, said connection conduit being a flexible hose.

2. The apparatus according to claim 1, wherein said air supply conduit is provided with spaced first branch tubes which each communicate with and project downwardly from said air supply conduit, each said first branch tube being releasably coupled to an upper end of a respective said connection conduit.

3. The apparatus according to claim 2, wherein each said aeration body is a ceramic candle having a second branch tube which communicates with and projects upwardly

Claim 3 continued...

from said candle, each said second branch tube being releasably coupled to a lower end of the associated connection conduit.

4. The apparatus according to claim 3, wherein said upper and lower ends of said connection conduit are each releasably connected to the associated branch tube by a clamping ring.

5. The apparatus according to claim 1, wherein each said aeration unit includes throttle means for limiting the air supplied to the associated aeration body, said throttle means being provided in the region of the connection of the associated connection conduit to said air supply conduit.

6. The apparatus according to claim 1, wherein said connection conduit is flexible only in a vertical plane which is substantially perpendicular to the direction in which said air supply conduit extends.

7. The apparatus according to claim 1, wherein each said aeration body is generally cylindrical and is a ceramic candle; and wherein each said air supply conduit includes a plurality of spaced hose sections and a plurality of T-shaped junction members which are each disposed between a respective pair of adjacent said hose sections, each said junction member including a cross tube

Claim 7 continued...
portion coupled at each end thereof to a respective one of the adjacent hose sections by a clamping ring, and including a branch tube portion which communicates with and projects downwardly from said cross tube portion intermediate the ends thereof and which is coupled to an upper end of the associated connecting-conduit by a clamping ring.

8. The apparatus according to claim 7, wherein said air supply conduit includes a plurality of float sleeves ofd generally cylindrical shape which each encircle a respective said cross tube portion of a respective said junction member.

9. The apparatus according to claim 8, wherein each said connection conduit is made of a corrosion resistant synthetic material.