ROTATING BIOLOGICAL CONTACTOR MATERIAL

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 Biolo¬ gical 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 thro¬ ugh 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 arr¬ anged 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 e ossment with a tooth¬ like protrusion and to arrange these emossments with their pro¬ trusions in straight rows between which are arranged correspond¬ ing rows of grooves or protrusions in which an adjacent protru- sion 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 la teral guiding or fixing is obtained. The number of grooves e ceeds that of toothed embossings and the teeth can therefore always find a grip in a groove irrespectively of the length- wise location, which will vary when a spiral is wound. As a result a RBC material is obtained -which requires no glueing welding and which consequently makes the RBC far cheaper tha what is known from previous techniques. When the RBC material is spiral wound it is preferably l ed in its final position by the use of a periferal band or s which is tightened so that constant pressure towards the sha is created,maintained during the whole rotational cycle. In way wearing of the RBC material due to alternating pressure tension and hence during rotation is avoided. In some cases it may be desirable to have several spiral wound sections mounted on a common axle and in these cases t binlike propellers may be arranged between the sections. The RBC material can of course also be provided "with holes permit a radial flow. It may further be noted that the easily acces ible flow paths peripherily as well as longitudinally allow simple washing. An example of the invention is described below in connec tion with the drawings, in which Fig. 1 is a plan view of th sheet material according to the invention and Fig. 2 and 3 r sp-ectively are cross-sections of the sheet seen laterally an longitudinally showing how the different layers grip into ea other. As can be seen from Fig. 1 from the sheet 1 bobs or embos ings 2. are embossed in the sheet extending upwardly from the sheet. These embossings are in the shown embodiment more or pyramidal but they may of course have any desired shape with leaving the scope of the invention. In the top of each embos or pyramide 2 teeth 3 are formed. These teeth are intended t grip into the over-laying sheet in its rows of grooves 4 ext ing longitudinally between rows of embossings 2. It is not n cessary to have such rows of grooves between each row of em¬ bossings. V. ' hen winding a RBC from the above described sheets prefe 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 gui¬ dance 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 gi¬ ving 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 achie.ved by winding two alternate sheets with corrugation in angle to each other. A further, advantage with the shown embodiment as well as other possible shapes is that the RBC need not be bulky on de¬ livery 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 thick¬ ness 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 obτ. : tain a self-floating RBC, thus reducing the load on the bear, rings 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 con¬ stituted by the sheet 1 but merely at intervals at different locations in the rotor in order to give the desired lifting ef- feet. 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 dθλ</n by it journaled axis and then as the slime grows finally is subjected to a force downwards. In thi way an essentially simplified supporting structure for the bi logical rotor is achieved. In order to have additional oxygen introduced in or brou in contact with the biological growth the embossings or bobs be given such shape as to trap air that is then released in t * water bubbling away up through rotor. One way of achieving th is to insert a closing strip provided with holes. A further great advantage of the invented RBC material ex in the field of RBC s with high specific surface, that is the relation between the ' surface of the material and the volume. has a great impact on the optimizing of the process. Preferab the relation between material surface and water volume is 200 2/ " 3, which in the case- of RBC materials with high spec fie surface, > 100 - 200 2/ m3 ( material sur ace/'growth ma rial, volume)-. .-^3REA

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 h a r a c t e r i z e d i n 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 a r a c t e r i z e d i n that the protrusions (3) are teeth and that the grooves (4) have corres¬ ponding lengths giving lateral as well as longitudinal guidance or loc¬ king 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 distan¬ ce 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 a r 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 a r a c t e r i z e d ' i 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 h a r a c t e r i z e d i n that the material is spi¬ ral 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 a r a c t e ¬ i z e d i that the material makes possible the manufacturing of ? ■* . for instance RBC with high specific surface (75-250 m / r. preferably 150-200 ra / m 3 with oxygenation and removal of sludge without clogging.

Inventors: HALLEN L
Applicants: HALLEN L, NORDISKA VATTENPROJEKT AB NOVA, NORDISKA VATTENPROJEKT AB
Application year: 1980
Main classification: C02F3
IPC codes: C02F3