CA1082821A - Biological sewage treatment apparatus - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

The disclosed apparatus includes an elongated semi-cylindrical trough closed at its ends and divided lengthwise into a series of neighbouring compartments, each partially accomodating a group of biological organism support members having axially or radially extending paddles or fins and co-rotatable with each other on a common shaft extending lengthwise of the trough; said trough being installed into the upper regions of a sewage settlement tank so that its bottom is spaced above the bottom of the settlement tank and its top is located slightly above the anticipated level of the sewage in the tank; a sewage inlet into the tank being provided at one corner thereof near the top of the tank and an inlet weir into the trough being provided into the top of the first compartment at one end of the trough diagonally opposite the location of sewage inlet into the tank so that sewage entering the tank through said inlet is required to flow diagonally across the tank and under the trough into said first compartment through said inlet weir, said first compartment having also slotting in its bottom; other weirs being provided in the tops of the partitions separating the compartments to establish a meandering path for said liquid flowing from said first compartment to the last through the intervening compartments; a discharge outlet being provided from said last compartment into an adjacent final settlement tank incorporating a chemical treatment zone.

Description

~.0~'~8Zl The invention relates to apparatus for the biological treatmc-nt of waste ~ater sewage and the like containing organic matter.

It is ~ell known to treat ~Jaste water sewage and the like by the biological organisms contained in the organic matter in the ~aste water, which decompose the waste thereby purifying the water. An accelerated form of such biological action is produced in equipment in which a plurality of support members, typically disc like rotors, are rotated into and out of the waste water at a slow rate of rotation.
Biological organisms in the water will adhere to such support members, and as the support members are then raised upwardly into the air, the organisms will have free access to the oxygen and other nutritive elements in the air and their growth is thereby substantially accelerated. A layer of such - organisms will rapidly build up on the supports, and as the organisms are then again rotated through the waste water, the decomposition action produced by such organisms is greatly accelerated. In this way, it is possible to treat substantial volumes of waste water in relatively small tanks.
Various problems are encountered in the design of such tanks however. Conventionally, the treatment takes place in three stages namely a primary settlement, a decomposition stage and a final settlement or clarifica*ion 25 stage. The provision of three separate tanks involves the -use of a relatively large amount of space, which may disfigure the landscape, or render the adjacent area unsuitable for other use. Odors emanating from some types of equipment may be noticeable in the immediate surroundings. Consequent-30 ly, this type of equipment is usually located at a distance 108'~2~

from buildings, or other areas of the landscape which may be usecl for recreation for example. In addition it is clearly desireable to minimize work on excavation, pouring foundations and the like.
Various attempts have been made to render the equip-ment more compact. In particular attempts have been made to combine two or more tanks together to make the equipment more readily concealed in the landscape. This however has not been carried out without some impairment of the overall 10 decomposition process and it has~not been totally successful. ~ -In addition, the servicing of this type of equipment should preferably be kept to a minimum and the design of such equipment should preferably be adaptable to a wide range of different sizes of tankg 80 that installations of widely ranging capability should be available with a minimum of engineering requirement.
One of the more unusual problems encountered with this type of equipment is the problem of maintaining a satisfactory layer of active biological organisms on the -rotating support members during all conditions of use.
When the equipment is continuously being supplied -with quantities of raw waste water and the like, it is found -that the biological organismsj will grow rapidly and maintain themselves in a highly active state. As the layers of such organisms accumulate on the supports become excessively thick, they will gradually flake off the supports, and fresh layers of organisms will then adhere to the supports and the entire growing and flaking cycle takes place continuously.
However, when the supply of raw waste water is discontinued for any length of time the organisms wither 941 P/2 C~ - 2 -1082~Zl and die, and the waste water contained in the equipment may eve~ start to become stagnant. When fresh raw waste water i8 then supplied to the equipment once more, it takes an apprec~able time for the layers of organisms to re-establish themselves and consequently, for an appreciable length of time no decomposition treatment is taking place.
It has suprisingly been found that this problem can be overcome by ensuring that a certain degree of circulation takes place between the decomposition tank and the primary settlement tank so that even during extended periods of shortage of fresh raw waste water, the organisms in the decomposition tank are continuously supplied with nutrients from the primary settlement tank. In this way, as soon as further supplies of raw waste waters are received 1~ in the equipment, the organisms are immediately available to carry out their decomposition function.
Such a self maintaining feature has been absent from previous installations of this general type, and is a particularly advantageous feature of the present invention.
The invention therefore will be seen to generally provide apparatus for the biological treatment of waste water, sewage and the like, containing organic matter, and having a settling tank havlng side and end walls and a bottom wall for collecting solid matter from said waste water, and for containing a predetermined volume of said waste water, a decomposition trough, said trough being shaped and positioned with at least a portion of said trough within an upper portion;of said settling tank and extending from end to end thereof at least partially below the liquid level in said tank, partition means located in 941 P,/2 Cl~ _ 3 _ ~08Z821 said trou~h at spaced intervals therealong, and defining separate consecutive treatment compartments, and weirs in said partition means communicating between said compartments in sequence, alternate weirs being offset whereby to establish a meandering liquid flow path through said compartment$, a plurality of biological organism support members, mounted for rotation on a common shaft, and arranged in spaced apart groups, there being at least one said group located at least partially in each of said compartments, with said shaf.t means extending longitudinally along the length of said trough, and incorporating power operated drive means for 510wly rotating the same, opening means in said settling tank for the introduction of raw waste water thereto at one end thereof offset to one side of said trough and above the lowermo9t portion of said trough, inlet weir means in a side of said trough, communicating between said settling tank and a first said compartment of said trough at a -predetermined level and at a side and end of said tank remote from said opening means whereby to establish a liquid flow path in said tank from said opening means, beneath said trough, to said inlet weir means, longitudinal slotted -opening means communicating between said first compartment of said trough and said settling tank below said predetermined level whereby to establish a liquid recycle flow path from said settling tank into said first compartment of said trough at a predetermined level, through said inlet weir means, and then downwardly within s,aid first compartment and through said slotted opening means back into said settling tank below said predetermined level, outlet opening means at a last said compartment of said trough for flow of -1082~21 treated water therefrom.
One of the significant features of the invention is the provision of apparatus of the type described wherein the bacl;eria support members are in the form of a plurality of rotors mounted on a common shaft, and including paddle means mounted on at least some of said rotors in the first compartment, whereby to induce flow of liquid from the first compartment of the trough downwardly into the settlement tank;
such downward flow being balanced by return flow from the settlement tank back into the first compartment of sald trough through the inlet weir.
It is a further and related objective of the invention to provide apparatus having the foregoing characteristics wherein the final settlement tank is separate lg from the primary settlement tank and trough, and wherein the shaft means from the decomposition tank extends over it, to-ward the final settlement tank, whereby suitable motor drive means may be mounted thereon. ~ ~-The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated and described preferred embodiments of the invention.
In the drawings:
Fig. 1 -- is an isometric view of the primary and final settlement tanks of the invention with portions broken away to reveal interior structure and with one group of 941 P/2 C~ - 5 -: .
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organism support members in position;
Fig. 2 -- is a top plan of the apparatus of Fig. 1 sectioned along the line II-II of Fig. 4 with the support members in place;
Fig. 3 -- is a side elevational view, sectioned along the line III-III of Fig. 2;
Fig. 4 -- is a section along the line IV-IV of Fig.
3;
Fig. 5 -- is an enlarged isometric view of a group of bacteria support members in cross-section, and ~ -Fig. 6 -- is an isometric view of a group of bacteria support members with a modified form of paddle mounted thereon.
Referring now to the drawings, the embodiments of the invention which is illustrated therein for the expository purposes of this submission, and without limitation, will be seen to comprise a primary settlement tank lO of generally, open-topped, hollow rectangular shape. It is formed of a substance suited to its function, e.g. concrete.
A trough 12 is located in the upper part of the tank lO with its top no lower than the top of tank 10 and preferably slightly higher. The trough 12 is typically, although not necessarily, of sheet metal construction, formed in an essentially semi-cylindrical shape and will preferably incorporate end walls 14 which may butt up against opposite ends of tank lO, or even be formed integrally therewith, as shown. In this way liquid can flow from one side of the tank 10 to the other only by passing under the trough 12.
Since most of the trough is below the normal operating liquid ' level for tank lO, this means that flow must ta~e place downwardly beneath trough 12.

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108'~8Zl Within the trough there are provided essentially flat partitions 16, 18 and 20 which may be of sheet metal and of generally semi-circular shape mounted on edge along the length of the trough 12, at equally spaced intervals defining four treatment compartments or zones 22, 24, 26 and 28. Gates or weirs 16', 18' and 20' are formed in the partitions 16, 18 and 20, at alternate corners thereof, whereby fluid flowing from one compartment to another must follow a generally zigzag meandering path, as shown, thereby inducing maximal exposure of the fluid to the treatment apparatus to be described.
Within each of the zones or compartments, there is provided a group 30 of bacteria support members. As better - shown in Fig. 4, the bacteria support members each comprise a generally circular plate-like disc 32 of any suitable material, mounted on a common shaft 34, and preferably interconnected around their edges by means such as the spacers 36 shown in Fig. 5. The discs 32 may be,for example, of thermo plastic material, either in a generally waffle plate design, or having a corrugated surface, or may be in the form of a mesh or open weave of thermo plastic material, such as to provide a maxium wetted surface area for each such disc 32. The discs 32 will not normally be required to carry extreme loads and can be made of quite thin material so as to permit accomodation of a relatively large number thereof in each treatment zone; only a few being shown in the drawing for the sake of clarity.
Shaft 34 is preferably supported in any suitable bearing means such as 38, at either end of trough 12.
A final settlement tank 40 is provided wh~ch, in 941 P/2 C~ - 7 -~Ot~ 8Z'l this embodiment of the invention, is shown separated from the primary tank 10 and trough 12. The settlement tank 40 can be manufactured of sheet metal, or poured concrete or any other suitable material. Preferably, as shown in Fig. 2, an end portion of shaft 34 will extend over an upper edge of tank 10, and suitable drive means 42 may be provided and mounted on such edge of tank 10 and coupled to the shaft 34 through any suitable gear reduction mechanism (not shown) the details of which require no description, but which will suffice to rotate the shaft 34 at a suitable speed usually in the region of two to six revolutions per minute.
A raw sewage inlet 44 is provided at an upper corner - ~ ~-of primary tank 10 adjacent to the final settlement tank 40.
At the diagonally opposite end of tank 10, a transfer port or inlet weir 46 i5 provided in the side wall of trough 12 communicating with the first compartment or tank zone 22.
In accordance with the invention such port or weir 46 will be on the side of trough 12 opposite from the raw sewage entry 44 of tank 10, and at the opposite end thereof. In this way, fluid entering port 44 is forced to flow the entire length of tank 10 and also to pass underneath trough 12 and well or flow upwardly on the other side thereof before it can pass into trough 12.
An elongated slotted opening 48 is provided along the bottom of trough 12, in compartment 22 only. Any solids passing into trough 12, from tank 10, can thus return to tank 10 from the first compartment 22.
From the last compartment 28, a transfer passage or duct 50 communicates between compartment 28 of trough 12, and the final settlement tank 40.
A clarified liquid outflow port 52 is provided as shown in the opposite side of tank 40 from (and preferably offset with respect to) the port or duct 50 whereby clarified liquids may be removed from tank 40.
In order to assist in ensuring a thorough contacting between the rotor disc 32 and the liquid in the various com-partments of trough 12, some form of liquid disturbers may be provided on the rotors 30, such as the paddles 54. The paddles also sweep around the inner su~face of the trough 12, and dislodge any solids or slime therefrom. The particular design of the paddles 54 may vary widely depending upon the design requirements of the particular unit. In addition, the paddles 54 on the rotor 30 in the first zone 22 will also materially assist in procuring flow of liquids and solids downwardly through the slotted opening 48 into the tank 10.
It will of course be appreciated that any such down-ward flow of liquids or solids will be immediately matched by a return flow of an equal volume of liquids from the tank 10 ~:
into the trough 12, usually through the weir 46 or in some circumstances back up through the opening 48 itself. In this way, organic material is constantly being supplied to the trough 12, even during relatively extended periods of inactivity.
It will be appreciated that the final settlement tank 40 may also incorporate a chlorination zone indicated as 60 in Fig. 1. Such a chlorination zone would essentially consist of a small partition separating a corner of the settlement tank 40 from the remainder, and incorporating any suitable mechanical chlorinator such as are well known in the art and require no further description.
Any suitable form of cover, such as the semi-cylindrical dome-shape cover 62 may be provided over the 941 P/2 CA _ 9 _ ... . .
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10828Z~

ta~',c 10 and trough 12.
Generally speaking the final settlement tank 40 may be covered with any suitable form of flat cover plate (not shown) the details of which are well known in the art.
Before touching on the operation of the apparatus described, it is desired to affirm, as will indeed be obvious, ~
that various distortionshave been incorporated into the ~ ~-drawing for the sake of clarity. ;
In operation, untreated waste water and sewage will be introduced intermittently through the port 44 where it will flow into the tank 10. Once a working level of liquid has been achieved in tank 10, liquid will then flow in a path along the tank 10 and under the trough 12, welling up on the other side of the trough 12 and flowing through the weir or gate 46. The liquid will then flow into the trough 12 filling up the various compartments 22, 24, 26 and 28 until they are filled to essentially the same liquid level as the tank 10. Once the normal working level has been achieved, then flow of liquid will take place in response to the introduction of additional raw waste water at the port 44, but will otherwise remain essentially static.
The downward, diagonal,and lengthwise flow path of liquids in tank lO,tends to promote the deposit of solids in tank 10, leaving at least partially clarified liquids to pass into trough 12.
The shaft 34 is rotated continuously at a speed which may be selected for the most efficient build-up of bacteria for any given type of waste water. Generally speaking the speed will be somewhere between two and six revolutions per minute, although the speed may be higher or lower depending upon the particular make-up of the waste water being supplied 941 P/2 ~A - 10 -., :- .. . .. .
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~O~Z~Zl to the installation.
As the discs 32 rotate through the liquid in the trou~h 12, they will acquire a liquid film, containing bacteria from the liquid, and as the discs 32 rotate through the air the liquid will be dried, leaving the bacteria adhering to the rotors 32. Such bacteria, being thus suspended in air will grow very much more quickly than they would grow in the liquid medium, and a film of such actively growing bacteria will thus build up on the discs -~

10 32 of the rotors 30. The action of the bacteria as they ~-pass through the liquid in the trough 12 is to actively decompose the organic materials and contaminants contained in the liquid and provide a purifying action.
The layer or film of bacteria on the disc 32 gradually increases in thickness until the layers flake away and fall into the liquid in the trough 12, at which time fresh bacteria are deposited on the disc 32 and the entire cycle takes place once again. The flakes of bacteria returning to the liquid will either flow downwardly through the slit 48 into the tank 10, or else will flow along the trough 12 in the zigzag flow path around the partitions 16, 18 and 20, as described and illustrated.
The flow path of the liquid along the trough 12 takes place around the opposite corners of the partitions 25 16, 18 and 20, from the first zone through successive zones to the last zone 28. In the last 28, the liquid flows through the port or weir 50 into the final settlement tank 40. The final settlement tank 40 permits settlement of any further solids, and any suspended flakes of bacteria and the like to settle out into the bottom of the tank 40, and 941 P/2C~

, . : ., ~ :~ -- ,: : . , : -~0~1 clarified liquid will then be free to flow through the outlet gate or weir 52. Depending upon the requirements of -~
particular municipalities, such clarified water may either be discharged directly into bodies of water, water courses and the like, or else may be chlorinated, in for example the chlorination zone 60 being discharged, or may even in certain circumstances require further treatment before being returned to the water supply.
When supplies of raw waste waters are being passed -.

more or less continuously to the tank 10 then flow will take place through the tank 10 and trough 12 and into the final settlement tank 40 more or less continuously in response to such flow volumes as are introduced.
In this case, the action of the bacteria build-up and flake away in the trough 12 is more or less continuous as described above.
However, during periods of inactivity or only limited use when supplies of fresh waste water to tank 10 are reduced or indeed discontinued for any extended period of time, then the action of the rotors 30, and the disturbers ~ -or paddles mounted thereon, in the first zone 22, will be -such as to provide a continuous recirculation flow of liquid from the compartment 22 downwardly through the slotted opening 48 into the tank 10, and return flow from the tank 10 back through the gate or weir 46 or opening 48 into the ~ough 12. In this way, there is a continuous exchange of liquid taking place between the trough 12 and the tank 10.
Thus during such periods of inactivity, the bacteria layers on the rotors 32 will be able to regenerate themselves continuously due to the presents of nutrients in the water 941 P/2C~ - 12 -1082~21 continuously circulating to and fro from the tank 10.
Moreover, the recirculation also transfers aerated liquid from trough 12 to tank 10 thus usefully oxygenating, to a degree, the contents of the latter.
As has been explained, such recirculation is created by so to speak "sweeping" compartment or zone 22 with the paddle 54 in the described manner. However, it is possible to procure substantially the same recirculation with the alternative form of paddle shown as fin 65 located on and projecting from each group 30 of discs 32; being located on a chord or diameter of at least one outside disc 32 as shown on Fig. 6; this alternative being provided to meet situations in which the lateral dimensions of trough 12 are somewhat critical.
The foregoing is a description of the preferred embodiment of the invention which is given here by way of example only. The invention is not to be taken as limited to any of these specific features as described, but comprehends all such variations thereof that has come within the scope of the appended claims.

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Claims (7)

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

1. Apparatus for the biological treatment of sewage in which organic matter is suspended in waste liquid, said apparatus comprising a settling tank for said sewage having side and end walls and a bottom for collecting organic matter settling out of said liquid; a trough in the upper portion of said settling tank extending horizontally therein from one said end to the other with its bottom spaced above the tank bottom and its top slightly above the anticipated level of the sewage in the tank;
partitions spaced at intervals along the length of said trough dividing it into separate consecutive treatment compartments; a weir at the top of each partition, the weirs in neighbouring partitions being offset relative to each other for establishing a meandering liquid flow path in the top of the trough from one of its ends to the other; a plurality of biological organism support members, mounted for rotation on a common shaft and arranged in spaced apart groups, there being at least one said group located partially in each of said compartments with said shaft extending longitudinally along the length of said trough, and incorporating power operated drive means for slowly rotating the same; opening means in said settling tank, for the intro-duction of raw sewage at one end thereof; inlet weir means in a side of said trough, communicating between the upper portion of said settling tank and the top of a first compartment at one end of said trough; said opening means and said inlet weir means being disposed at diagonally opposite upper corners of said tank whereby to establish a liquid flow path in said tank from said opening means, beneath said trough, to said inlet weir means;
longitudinal slotted opening means in the bottom of said first compartment communicating between it and said settling tank establishing a liquid recycle flow path from said settling tank through said inlet weir means into said first compartment then downwardly through said slotted opening means back into said settling tank, and outlet opening means at a last said compart-ment of said trough for discharge of liquid therefrom.

2. Apparatus as claimed in Claim 1 wherein said trough is of generally semi-cylindrical conformation.

3. Apparatus as claimed in Claims 1 or 2 wherein said groups of biological organism support members have paddles extending co-rotatably therefrom for disturbing the trough contents while rotating.

4. Apparatus as claimed in Claims 1 or 2 wherein said group of biological organism support members have fins transversing and projecting from the outer biological organism support members of the groups for disturbing the trough contents while rotating.

5. Apparatus as claimed in Claim 1 wherein said shaft means extends from one end of said settlement tank to the other, and one end thereof overhangs said settlement tank and said drive means is mounted exteriorly of said settlement tank.

6. Apparatus as claimed in Claims 1 or 2 wherein said groups of biological organism support members have paddles extending co-rotatably therefrom for disturbing the trough contents while rotating and further including a final settlement tank connected with said last compartment of said trough.

7. Apparatus as claimed in Claims 1 or 2 wherein said groups of biological organism support members have paddles extending co-rotatably therefrom for disturbing the trough contents while rotating and further including a final settlement tank connected with said last compartment of said trough;

chemical tank treatment means being incorporated in said final settlement tank.