CA1038090A

CA1038090A - Reactor for biological water treatment

Info

Publication number: CA1038090A
Application number: CA215,277A
Authority: CA
Inventors: Svatopluk Mackrle; Vladimir Mackrle; Oldrich Dracka
Original assignee: Agrotechnika NP
Current assignee: Agrotechnika NP
Priority date: 1973-12-04
Filing date: 1974-12-03
Publication date: 1978-09-05
Also published as: NL172436B; FR2252985B1; AU7580374A; NL172436C; SE7415155L; FR2252985A1; DE2456953C3; BR7410116A; DE2456953A1; JPS5537316B2; AT335931B; SE412375B; DE2456953B2; IT1026744B; ES432486A1; NL7415763A; AR201345A1; JPS5090143A; ATA917374A

Abstract

ABSTRACT OF THE DISCLOSURE
Reactor for biological water treatment, comprising a tank with a mantle, an inclined partition wall having substan-tially the shape of a funnel in the upper part of the tank, di-viding said tank into a fermentation space below the partition wall and into a space used for fluid filtration above the par-tition wall, an inlet opening in the lower part of the spaced used for fluid filtration, which has a hydraulic resistance and connects the fermentation space with the space used for fluid filtration and allows the entrance of the treated liquid from the fermentation space to the space used for fluid filtration and the passage in the opposite direction into the fermentation space of the particles of coagulated suspension retained in the space used for fluid filtration, a further wall provided below said partition wall which determines in the fermentation space a rectifying channel opened at both ends and which communicates at its lower end with the inlet opening into the space used for fluid filtration, a supply conduit which supplies the treated water into the fermentation space, a discharge conduit for re-moving the excess sludge at the bottom of the fermentation spa-ce, agitating means in the fermentation space which create in the rectifying channel a liquid flow with a downward component, and collecting means of cleaned water in the upper part of the space used for fluid filtration.

Description

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The present invention relates to a reactor for the biological treatment of waste waters by fluid separation of a suspension and automatic return of part of activated sludge into a fermentation space, which reactor is particularly adapted to treat concentrated waste waters.
The higher the concentration of activated sludge in the fermentation space is, the higher the efficiency o the bioloyical cleaning treatment of waste waters is. It is therefore advisable to maintain a high concentration of activated sludge in the fermentation space. This can be accomplished by return of a part of the sludge, which has been separated from the water in a separation or ~iltration space, b~ck into the fermentation space. ~p to now the highest ef~iaiency in the field of bioloyical wa~er tr~atment has been achieved ~
using a reactor, wherein both th~ fermentation and separation spaces are in a single container and a part of the activated slud~e in the separation space returns automatically into the fermentation space because of the gravity.
Some apparatuses are known, which however present varlous drawbacks. One of these drawbacks lies in that none of these apparatuses provide for a proportional balance between separation and fermentation when treating waste waters of different concentration, while simultaneously maintaining optimum dimensions and optimum operating and economic parameters. The efficiency of the separation depends in particular on the size of the separation surface on the fermentation capacity and on the volume of the ermentation 5pace. When the concentrations of waste waters are different, these parameters are different. The requi-rement of optimum yield has led to the presently known apparatu-ses which all have substantially different cons-tructions for different kinds of waste water. With some other apparatuses, other factors of dimensions must be taken into account. For example, the capacity o~ the apparatus may be changed (depend-ing on the surface and space available with respect to the size of the apparatus), which requires alterations of design depending on the capacities of every cleaning stations. These ~actors cause various technical difficulties, such as, for instance, hydraulic conditions, individual designs and adjustments of the apparatus, and, therefore, cause difficulties with standardization, mass production an~ the like. These difficulties of course have repercussions on the costs oE ~he apparatuses. Another drawback of the actually known apparatuses of this kind is that, in case of an aerobic activation, use cannot be made of a deeply immersed turbine agitator, which turhine agitator is that among all the known aeration system which has the highest efficiency. By turbine agitator, it must be understood a device which generates an intensiv~ suction in the axial direction and throw~ th~ uid in a radial direction. This drawback i~ callsed by tho fact that the separation in the reactors depends on the flow in the fermen-tation space and by the fact that a deeply immersed turbine agitator creates in the fermentation space entirely diEferent conditions of flow from that required in the serating system used in these reactors. A consequence thereof is a high consump-tion of energy in operation.
The subject invention proposes to overcome the drawbacks up to now encountered in the known reactors and to provide ~
therefor a reactor which allows a much wider application under different conditions. The reactor according to the present invention comprises a tank provided with a mantle having advanta-geously a cylindrical shape, which mantle is divlded by an inclin-ed partition wall into a space or fluid filtration located above the partition wall and into a fermentation space located below the partition wall. The fluid Eil-tration space is provided witll an inlet opening into its lower part, which inlet connects i.~
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~ the fermentation space to the fluid filtration space to allow passage of the water to be treated from the fermentation space into the filtration space and passage in the opposite direction of particles of coagulated suspension retained in the fluid suspension space into the fermentation space. The fermentation space is provided with a liquid agitator which creates near the inlet opening a liquid flow having a downward direction towards the inlet opening. Another wall is located below the partition wall, which other wall defines in the fermentation space a rectifying channel open at both ends and communicating at its lower end with the inlet opening in the fluid filtration space.
The reactor of course also comprises a conduit for supplying the water to be treated into the fermentation space and discharge conduit for removing the e~cess of sludge at the bottom of the fermentation space.
~ s liquid agitator a turbine ayitator can be advanta-geous,ly used which turbine is preferably supplied in its suction part with some oxydizing medium. In the fermentation space, baffle walls may be provided for ,suppressing a rotating motion of the water around the vertical axis of the tank.
The subject invention will now be better illustrated with reference to the enclosed drawings wherein Figs. 1 and 2 show two different alternative reactors in an axial sectional elevation, and the following description divided to preferred embodiments.
The reactor shown in fig. 1 comprises a tank having a cylindrical shape with a vertical axis, provided with a mantle 1 and a cover lq. The upper part of the space defined in the reactor is divided by a funnel shaped partition wall 2 in-to two operating spaces, namely a Eermentation space ~ below the partition wall 2, wherein the microbiological water cleaning pro-cess is proceeded and a space F for fluid filtration above the i - 3 -.
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partition wall 2, used for separating the suspension of activatedsludge created in the fermentation space A. The space F used for fluid filtration is in its lower part connected with the fermentation space A, by a central inlet opening 3 which inlet opening 3 is formed in the partition wall 2. Another wall 4 is provided in the fermentation space A below the partition wall

2, which wall 4 defines a rectifying channel G, which is opened at both ends and communicates by way of the inlet opening 3 with the space F for fluid filtration. The wall 4 is also funnel-shaped and is concentrical with the partition wall 2. The recti~ying channel G defines by both walls 2 and 4 is widening downwards.
A turbine agitator 5 is located in the fermen-tation space A, near the bottom thereof. Some oxydizing medium is supplied wi-thin the suction area oE the agitator 5 so that this agitator 5 s~rves simultaneously as part oE th~ ox~di~incJ sy~tt?m oE the rt?actor.
The internal arr~ngement o~ the reactor permits to use also other types of agitators for liquid, with or without supply oE oxydizing medium, such as for instance a propeller agitator or an air lift pump located at the circumference of the reactor. If a turbine agitator is used, the fermentation space A
is preferably provided with baffle walls 7 in order to elimina-te any rotating motion of the liquid. The reactor is furthermore provided with a sludge discharge conduit 8 for removing the excess of sludge from the fermentation space A. The water which is to be cleaned, is supplied into the fermentation space A through a supply conduit 10. Venting conduits 9 are located at the top of the fermentation space, which conduits 9 terminate into a space O above the space F ;Eor Elwid filtrat:ion. The spact? O
is separated from the space F by a partition wall 12, and is used for removing gases. The space O has at its top a venting conduit 13 and at its bottom a discharge condwit 15 which termina-tes into the fermentation space ~. The cleaned wa-ter is drained 33~

over through the conduit 11 at the upper part of the s~aee F used for fluid filtration.
The shape of the above described arrangement of the reactor of course can vary through a cylindrical shape is the most advantageous for metal mantles. However, a square cross-section mantle made of concrete can be suitably used.
The above described reac-tor operates as follows:
The liquid to be treated which contains organic sub~tanee and is mostly a waste wa~er ~aving a high content of organie matter, is supplied via the supply conduits 10 into the fermentation space A. The arrangement of the fermentation space permits to clean the water both with sufficient or insufficient supply of oxygen depending on the ermentation processus. The only difference whieh exist.s between the reaetors used for these two kinds o~ Eermentation proe~ssus .i~ th~ n~cl oE a suppl~ of oxydizing medium in the ease o~ the aerobie proe~ssus Eor eleaninc~
; water. The aerobie eleaning ean be an aetivating proeess; one example of a eleaning with insuffieient supply o~ oxygen is the denitrifieation of waste waters. The reactor shown in Fig. 1 is adapted for carrying out an aerobic activating proeess and is therefor provided with a eonduit 6 for supplying an oxydating medium such as for instanee, air or eoneentrated oxygen. As liquid agitator in the fermentation space A, use is made of a turbine agitator 5 whieh generates the required flow of liquid in the turbulenee for inereasing the effieieney of the supply of oxygen from the gaseous oxydizing medium into the liquid. For this pur-pose the use of a turbine agitator is partieularly advantageous sinee this part.Lcular type of acJitator cJenerates turbulenccs whieh permit to achieve a high oxygenation with a high efficiency.
The turbine agitator c3enerates in the fermentation space ~ a vertieal Elow and a radial ;Elow in the horizontal direetion. The oxydizing medium is supplied into the suction area ~ .

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of the turbine agitator through the supply conduit 6~ Baffle walls 7 situated in the fermentation space A near the mantle 11 avoid the rotating movement of the liquid and the dispersed oxydizing medium around the vertical axis of the tank and rectify its flow in a vertical direc-tion along the mantle 1. The upward flow of the liquid is deviated in the upper part of the fermenta-tion space A toward the axis of the space and drops along this axis toward the suction area of the turbine agitator. In the course of this flow, the dispersed gases are separated from the liquid in the upper part of the fermentation space A and are removed through the vent.ing tubes 9. A part of the flow in the upper part of the fermentation space A which has an inclined downward direction, enters the rectiEyin~ ~h~nn~l G :Eormed by the wall 4, which is concentrically arranged with respeat to the partition wall 2 separatin~J the ferment~tion space ~ rom the space F for 1uid fi.ltration. The flow of the liquid in the rectify.ing channel G has the same direction as the main stream of the liquid in the fermentation space A below the wall 4. The task of the rectifying channel G is to reduce the speed of passage of the liquid near the inlet opening 3, by means of which the fermentation space A is communicating with the space F for fluid filtration. The reduction of the speed of the liquid near the inlet opening 3 prevents the generation of whirling currents- in : the fluid filtration space F, inorder to achieve a highly efficient separation of the suspension by. fluid filtration. The rectifying channel G is widened downwards; the reduction of its cross section because of its :Eunnel shape is thus compensa-ted.
During the p~ssa~e oE the liquid in the rectifying channel G/

a part of the suspension is separated from the liquid. This reduces to a certain degree the amount of 10ccular suspension to be separated from the space Eluid filtration F and thus increases the efficiency of the separation process ln the space F. The water with the floccular suspension of activated sludge enters from the , , ~3~
rectifying channel G by way of the inlet opening 3 into the spa-ce fluid filtration ~. During the filtration in the fluid layer, the floccular suspension coagulates and the heavier particles of the suspension sink due to the gravitation forces and pass through the inlet opening 3 into the rectifying channel G, wherefrom they are returned into the fermentation space _ by the liquid flowing downwards.
The water clarified by fluid filtration is collected in the collecting conduits ll situated in the upper part of the O space fluid filtration F. The draining of the excess of sludge is accomplished periodically by means of the discharge conduit, duriny a short interruption of agitation o the liquid in khe fermentation space A. IE the concentrated waste waters which are worke~ orm A large amount o~ foam, the :r~ct~r .is adv~nta-geously provided with the ad~itional space O whicl~ is s~parat~d from the space F us.ed for fluid filtration by the parti~ion wall 12. The space O is closed on the top by the cover 14 and is ~ provided with a venting conduit 13 for removing the gases from the reactor. The space O serves for gravitational thickening of the foam, which enters this space O via the venting conduits 9 together with gases separated in the fermentation space _.
The co.ndensed foam flows by gravitation over the discharge con-duit 15 back into the fermentation space A.
The space O can be also utilized for collecting the non-utilized concentraked ox~gen if concentrated oxygen is used as oxydizing medium. The non-utilized oxygen and the gases yene-rated during the fermentation process which are collected in the space O can be supplied to another reactor, thus increasing the efficien~y of its use.
The reactor according to the present invention is not limited to the aerobic cleaning o:E was-te waters. As another example of use, the denitrificat:ion of water with an insufficienk ~31Y C~
supply of oxygen can be mentioned. In that casa, a limited amount of oxydizing medium or no oxydizing medium is supplied to the fermentation space, for avoiding to supply aerobic'conditions for a fermentation process. The most suitable agitator for the liquid in the fermentation space A is for instance a propeller agitator or a pneumatic system based on an air lift effect with a low efficiency of oxygen supply. soth mentioned agitators create in the fermentation space' A a flow of liquid similar to the one generated by a turbine agitator and provide the rectifying channel G with the flow which is necessary -to achieve an efficient separation in the space F for fluid filtration.
Fig. 2 shows another embodiment of the invention which is suitable ~or reackors having larger capacities. In Fig. 2, the same numeral reerences are used for the same el~ments as in Fiy. 1. ~'he shape and operation Oe this reactor are substantial-ly identical to those o~ the reactor shown Fig. 1, with the difference that the space F used for fluid filtration is in the upper part of the reactor along the circumference of the mantle 1.' The mantle 1 of the reactor is in its upper part funnel shaped.
The partition wall 2 separating the space F used for fluid fil tration from the fermentation space A in in the shape of an over turned funnel terminated at the top by the cover 14 and provided with a venting tube 13. The lower edge of the partition wall 2 and the mantle 1 form t~le inlet opening 3, connecting the fluid filtration space F with the fermentation space A. The fermenta-tion space A is provided with an agitator 5 used for simulta-neously dispersing the oxydatinc3 medium and increasing the turbulence o the liquid. As agitator', a turbinc ac3itator 5 is used and some oxydatiny medium is fed within its suction area via the supply conduit 6 so as to be introduced into the ermen-tation space'A. Inside the fermentatioll space A, a wall 4 is located concentrically around the turbine agitator 5, into " 1 ~
~ 3, the region of the radial flow of the liquid from the turbine agitator 5. Baffle walls 7 are located inside the fermentation space A, for avoiding any rotational movement of the liquid in the fermentation space A around the vertical axis thereof. The inlet opening 3 into the space F used for fluid filtration is connected with the fermentation space _ by way of a connecting channel P formed by a wall 16 and the mantle 1. The connecting channel P ~,erminates into the Eermentation space A in the region where the flow generated by the turbine agitator and the wall 4 has a substantially downward direction. Tl~e wall 4 extends beyond the termination of the connecting channel P and forms together with the wall 16 a recti~ying channel G, the shape and dimension~
of which are chosen so as to reduce any whirling currents in the connecting channel P and to contribute to th~ rcturn af tho coac~ulated suspension from ~he spac~ ~lui~ E~ ra~:ion ~ k into the Eermentation ~pace ~. The closed spac~ O, in the embodi-ment shown in Fig. 2, is located only above the central part of the fermentation space.
The arrangement according to Fig. 2 operates similar-ly to that shown in Fig. 1. The location of the fluid filtration space F at the circumference of the upper part of the reactor permits to increase the separating surface of the fluid filtra-tion space F by the widening of the funnel-shaped mantle 1 in the upper part of the reactor. The connecting channel P permits in this case to use a turbine agitator as agitator 5 for the liquid in the fermentation space . As the reactor shown in Fig. 1, the reactor shown in Fig. 2 can be used both for aerobic cleaning processus and, Eor instance, for a denitrification processus requiring a lack of oxygen. As agitator 5, a propeller agitator or a pneumatic system using an air lift effect can be used to provide a sufficient flow of the liquid and a low supply of oxygen for the microbiological fermen-tation processus. The _ 9 _ .~ .
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provision of a closed fermentation s~ace A gives a highly effec-tive oxydating system as it permits an economic utilization of concentrated oxygen as oxydizing medium in the aerobic water cleaning processus. The shape of mantle is not limited to a cylin-drical shape, which is advantageous when use is made of metal mantles. Use can also be made of any other suitable shape, such as for instance a square cross sectional shape if the mantle 1 of the reactor is made of concrete.
The reactor according to the present invention present several advantages. The ratio of the dimension of the separating surface to the dimensions of the activating space can be easily adjusted by changing the height of the reactor without any other substantial changes in shape, while the flow conditions remain the same. Thus standart apparatus can be used Eor waske waters of dif~erent concentrations. The adjustable shape oE thc Leaator accordiny to the invention permits to use it Eor optimum cons-tructional arrangements o different capacity. For instance, small reactors with mantles of ro-tational shape can be advantageously composed of a number of easily -transportable segments, which can be manufactured in large quantities and already provided in the factory with a perfect protective coating. Thus a mass manufac-ture is permitted, which reduces costs for transport and assembl-ing. In all fields, substantial savings are achieved. The shape of the reactor requires a small floor space, that is particular-ly advantageous if the cleaning stations are additionally built in plants which are already opened, where it lacks space. The possibility of an easy closing of the fermentation space enables to perEorm in the reactor also operations with insu~Eicient sup~y of oxygen, such as for instance denitrifications. The possibility of application of a deeply immersed turbine agitator contributes to in~rease the efficienty of the aerating process (up to ~ kg O2/KWh) and thus to reduce the need in energy. ~hen concentrated . ~ . ) ~3~10 waste waters are cleaned~ the efficiency of usiny an oxydating medium is increased and the requirement for floor space reduced due to the height of the reactor. The high efficiency obtained with an oxydizing medium together with the possibility of an easy closing of the fermentation space enable an economical use of expensive oxydizing mediums such as, for instance, concentra-ted oxygen. A11 -these advantages are particularly substantial when cleaniny concentrated waste waters.

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Claims

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

1. A reactor for the biological treatment of water said reactor comprising:
- a tank with a mantle, - an inclined partition wall having substantially the shape of a funnel in the upper part of the tank said partition wall, dividing the tank into a fermentation space below the partition wall and a fluid filtration space above the partition wall, - an inlet opening into the lower part of the fluid filtration space said inlet collecting the fermentation space with the fluid filtration space to allow passage of the water to be treated from the fermentation space to the fluid filtration space and passage in the opposite direction of particles of coagulated suspension retained in the space fluid filtration space into the fermentation space, - another wall located below the partition wall, said other wall defining in the fermentation space a rectifying channel open at both ends, said channel communicating at its lower end with the inlet opening into the fluid filtration space, - a conduit for supplying the water to be treated into the fermentation space, - a discharge conduit for removing the excess of sludge at the bottom of the fermentation space, - agitating means in the fermentation space for creating in the rectifying channel a liquid flow having a downward direction, and - means for collecting the treated water in the upper part of the fluid filtration space.

2. A reactor as in claim 1, wherein the partition wall between the fermentation space and the filtration space has the shape of a funnel in normal position: the inlet opening into the fluid filtration space is near the axis of the tank, and the other wall forming the rectifying channel has also a funnel shape.

3. A reactor as in claim 1, wherein the partition wall between the filtration space and the fermentation space has the shape of an overturned funnel; the rectifying channel has a downward inclination toward the circumference of the mantle of the tank; the inlet opening into the filtration space is near the circumference of the mantle of the tank, and another channel is provided in the fermentation space at the circumference of the mantle of the tank to connect the inlet opening into the filtra-tion space with the lower part of the rectifying channel.

4. A reactor as in claim 1, further comprising means for supplying an oxydizing medium to the suction are of the agitating means.

5. A reactor as in claim 1, further comprising baflle walls in the fermentation space to avoid rotating motion of the water around the vertical axis of the tank.