WO1981002570A1

WO1981002570A1 - Rotating biological contactor material

Info

Publication number: WO1981002570A1
Application number: PCT/SE1980/000070
Authority: WO
Inventors: L Hallen
Original assignee: Nordiska Vattenprojekt Ab Nova; L Hallen
Priority date: 1980-03-10
Filing date: 1980-03-10
Publication date: 1981-09-17
Also published as: EP0054017A1; IT1138716B; IT8120212A0

Abstract

Rotating biological contactor constituted by sheet layers (1) of for example plastic material which has been provided with numerous embossings (2) in order to keep a distance between the different layers (1) and in order to give an increased surface for the growth of microorganisms. In order to give a stiff and at the same time easily fabricated structure some or each of the embossings (2) are at their tops provided with protrading teeth (3) that can grip into corresponding grooves (4) in an adjacent layer. The layers can be identical and offset in order to allow the grooves (4) to be arranged in rows between the embossings (2).

Description

Rotating Biological Contactor Material

This invention relates to an improvment of Rotating Biological Contactors (RBC). These are used in the processing of waste water. During the slow rotation of the RBC, microorganisms are exposed t.o substrate when passing through the waste water and to oxygen when passing through the air. Also oxygen dissolved in the wastewater is utilized by the bacteria. Oxygen and substrate are both necessary for the growth of the microorganisms.

In order to minimize rotational resistance and at the same time allowing a low resistance axial flow through the rotor it is previously known for example from US patent 4115 268 to use spiral wound sheets with bobs or embossings therein resulting in a short distance between the sheets, those bobs or embossings leave flowpaths circumferentially as well as longitudinally through the RBC. As a result of this the described rotor will have no tendency to lift water and hence a rather small torque can turn the rotor.

In previous devices of this kind the different, layers of sheet are sp irally wound and welded as in the case of the US patent 4115 268 or glued, as in the case with the Swedish patent application 7801463-6, together to form the rotor. It is clear that this procedure of manufacturing a RBC due to the welding or glueing becomes somewhat less economical than desired. One object of the invention is to eliminate this set-back.

In other RBCs, for example in accordance with the US patent 3847-811, segment or cupshaped sections of RBC material are arranged side-by-side around a shaft and the flow is essentially radial- circumferential. It is the object of the invention also in this case to provide an improved RBC mater-ial that is easy to handle and easily fabricated. The desired improλ-'ement is in accordance with the invention accomplished by providing each bob or emossment with a toothlike protrusion and to arrange these emossments with their protrusions in straight rows between which are arranged corresponding rows of grooves or protrusions in which an adjacent protrusion or tooth of an embossment can grip in. From layer to layer a slight laterel off-set give the layers a steady grip in each other. By a suitable design of the teeth and grooves also lateral guiding or fixing is obtained. The number of grooves exceeds that of toothed embossings and the teeth can therefore always find a grip in a groove irrespectively of the lengthwise location, which will vary when a spiral is wound. As a result a RBC material is obtained which requires no glueing or welding and which consequently makes the RBC far cheaper than what is known from previous techniques.

When the RBC material is spiral wound it is preferably locked in its final position by the use of a periferal band or strip which is tightened so that constant pressure towards the shaft is created,maintained during the whole rotational cycle. In this way wearing of the RBC material due to alternating pressure and tension and hence during rotation is avoided. In some cases it may be desirable to have several spiralwound sections mounted on a common axle and in these cases tur binlike propellers may be arranged between the sections. The RBC material can of course also be provided "with holes permitting a radial flow. It may further be noted that the easily access ible flow paths peripherily as well as longitudinally allow simple washing.

An example of the invention is described below in connection with the drawings, in which Fig. 1 is a plan view of the sheet material according to the invention and Fig. 2 and 3 respectively are cross-sections of the sheet seen laterally and longitudinally showing how the different layers grip into each other.

As can be seen from Fig. 1 from the sheet 1 bobs or embossings 2. are embossed in the sheet extending upwardly from the sheet. These embossings are in the shown embodiment more or less pyramidal but they may of course have any desired shape without leaving the scope of the invention. In the top of each embossing or pyramide 2 teeth 3 are formed. These teeth are intended to grip into the over-laying sheet in its rows of grooves 4 extending longitudinally between rows of embossings 2. It is not necessary to have such rows of grooves between each row of embossings.

V.^'hen winding a RBC from the above described sheets prefer ably two sheets are used with their embossings turned outwardly in order never to close the space in between. Due to the many different grooves in the rows it is irrespectively of the radius of the sheet possible to have these grip into each other. As the grooves and teeth have corresponding lengths a longitudinal guidance or locking is also achieved.

It is thus rather easy to wind up a complete RBC from one or two strips of the sheet material.

In order to improve aerobic conditions in the center of the spiral where the peripheral velocity is small, the bobs can be formed to provide a larger distance between the sheets thus giving a lower specific surface in this area, as compared to the outer parts of the spiral.

The desired distance between sheets in the spiral can also be achieved by winding two alternate sheets with corrugation in angle to each other.

A furthe r advantage with the shown embodiment as well as other possible shapes is that the RBC need not be bulky on delivery as the sheet material can be delivered with one embossing totally filling an embossing in the next layer, that is each layer of sheet material does not add more than roughly the thickness of the sheet material in itself. This is, as can be easily understood, a great advantage from a transportation point of view, In some cases it might be preferred or advantageous to obtain a self-floating RBC, thus reducing the load on the bearings and minimizing the energy comsumption. In order to achieve this it is possible to insert strips of sheet material closing some of the embossings to closed spaces. In Fig. 1 such a strip is shown dotted and given the referance numeral 5. The sheet 1 is prefabricated to take up this closing strip without affecting the overall dimensions. It is of course not necessary to put in such a closing strip over the entire spiral or filter body constituted by the sheet 1 but merely at intervals at different locations in the rotor in order to give the desired lifting effeet. Moreover those closing strips can either be simply put in place and held there by the winding or it is possible to weld or glue them in place. The lifting force is preferably dimensioned so that the initial status of the biological rotor is that it is actually pressed down by it journaled axis and then as the slime grows finally is subjected to a force downwards. In this way an essentially simplified supporting structure for the biological rotor is achieved. In order to have additional oxygen introduced in or brought in contact with the biological growth the embossings or bobs may be given such shape as to trap air that is then released in the water bubbling away up through rotor. One way of achieving this is to insert a closing strip provided with holes. A further great advantage of the invented RBC material exists in the field of RBC:s with high specific surface, that is the relation between the surface of the material and the volume. This has a great impact on the optimizing of the process. Preferably the relation between material surface and water volume is 200 m ²/ m³, which in the case of RBC materials with high specifie surface, > 100 - 200 m ²/ m³ ( material surface/ growth mate rial, volume).

Claims

C l a i m s

1. A Rotating Biological Contactor material constituted by sheets with embossings (2) thereon giving a distance between adjacent sheet layers (1), c har ac t e r i z e d in that at least some embossings (2) are provided with protrusions (3) that can grip into grooves (4) arranged in the adjacent sheet layer in rows.

2. Material according to claim 1, c h ar a c t e r i z e d in that the protrusions (3) are teeth and that the grooves (4) have corresponding lengths giving lateral as well as longitudinal guidance or locking and that there are more grooves (4) than teeth (3) , in order always to allow the .teeth (3) on the embossings (2) to grip into a groove (4) even when the sheets are spiral wound and the radius and thus the distance between the embossings change.

3. Material according to claim 1 or 2, c h a r a c t e r i z e d i n that the embossings (2) in the sheet material with their protrusions are turned outwardly whereas the grooves (43 are turned inwardly and that between rows of embossings (2) are arranged rows of grooves (4) so that with an offset between layer (1) identically formed layers may grip into each other.

4. Material according to one of claim 1-3, c h ar a c t e r i z e d i n that strips (4) of sheet material are inserted covering or closing the interior space in some of the embossings (2) giving airfilled spaces that can keep a rotor floating.

5. Material according to one of claim 1-4, c h ara c t er i z e di n that perforated strips are inserted between the layers enabling transportion of air down in the waste water, then to be released as the angle of the material changes.

6. Rotating Biological Contractor incorporating the material of one of claims 1-5, c har a c t e r i z e d in that the material is spiral wound of one or two spiral wound sheets that are offset from layer to layer, and that the material is locked into position by the use of an outer periferal strip which is tightened in order to create a constante pressure towards the shaft.

7. Process of material according to claim 1 or 2, c h ar a c t e r i z e d i n that the material makes possible the manufacturing of for instance RBC with high specific surface (75-250 m²/m³ preferably

150-200 ra / m 3 with oxygenation and removal of sludge without clogging