WO1984000157A1

WO1984000157A1 - Improvements in a process in microbiological purification and device and materials therefor

Info

Publication number: WO1984000157A1
Application number: PCT/SE1983/000266
Authority: WO
Inventors: Kaowe Kaowert
Original assignee: Kaowe Kaowert
Priority date: 1982-06-29
Filing date: 1983-06-29
Publication date: 1984-01-19
Also published as: EP0126728A1; US4468326A

Abstract

Process at bio-processing of waste water with bio-rotors submerged in the water, with the substrate growth surface constituting the rotor is dimensioned relative to the water volume so that the amount of water is 1 to 10 litre water per m2 substrate surface, preferably 2 to 8 litres per m2 substrate surface. The materials have a specific surface of 150-400 m2 per m3 material outer volume (preferably 200-350 m2 per m3). When this results in water volumes in excess of the submerged rotor volume the basin is increased but with one or more shields being arranged in the basin to prevent the water from bypassing the rotor.

Description

Improvments in a proce s s in microb io lo gical pur if icat ion and device and mater ials there for .

The present invention relates to biological purification of waste water. Biological purification of waste water has of course always existed in the nature and with the increased demands on purification of waste water attempts have been made also to utilize these effects economically.

Purification was first carried out in such a way that the waste water was kept in big basins having a large surface through which bubbles of oxygen or air were optionally passed to get a bacterial degradation of the organic substances in the water. In order to achieve a more economical biological purification of the waste water more complicated devices have also been constructed to reduce the size of these basins.

One example thereof is the rotating biological contactor (RBC) which means in principle that the bacterial growth or the biological degradation in the water is made to take place on the surface of contactor materials. The contactor materials are more or less submerged in a basin and are rotated to bring the microorganisms into contact with the air as well as the water and the organic material therein to be degraded. However, so far no real optimization of the constructions and the function of those RBC has been made. One reason has been that these RBC have been found to be so substantially much more economical than what has been the case before that no further possible development has been considered.

The optimization attempts that of course have been made for economical reasons have been relatively hazardous and unsystematical, and therefore no unitary rules and optimization conditions of RBC's are present so far. It is therefore the object of the invention to define a process in microbiological purification making possible an optimization of the operating conditions and consequently a minimizing of the required costs.

The present invention also relates to a device based on these principles to indicate the purely practical application of the principles. In accordance with the invention two parameters are important when dimensioning RBC plants apart from the downright dimensioning of capacity. The first parameter is that the amount of basin water per m² of substrate surface should lie between 1 and 10 liter of water per m², preferably between 2 and 8 liter per m² of substrate material. The second important parameter is that the specific substrate surface per rotor volume of material according to the invention should be between 150 and 400 m ² per m³. This range has also been illustrated in the appended diagram.

Brief description of the drawings The invention will be described in greater detail with reference to the accompanying drawings wherein Fig 1 is a graph of the dimensioning parameters. Fig:s 1a, 1b and 1c are schematic views of arrangement in the basins and the rotation of the RBC's provide the pumping of the water which is necessary for oxidation of the water.

If it is further assumed that the water first passes the RBC steps 1 and 2, the water in this part of RBC and this basin half will of course contain a larger amount of biologically degradable material, which results in a greater load of sludge, and therefor this RBC have a somewhat less tight material, i.e. with better passageways and a somewhat smaller surface per m of material body. With interconnected separation of coarse sludge, the following RBC part 3 and 4 may have a larger specific surface per m³ contactor. It is also possible to have an anaerobic degradation over certain length sections of the RBC's. It is possible to have a nitrification in the end section with an increased RBC diametre and a specific surface material, giving a longer retention time to permit purification that is as complete as possible. It is wellknown that carbon compounds in waste water treatments requires shorter retention time for breaking up than nitrogen compounds. With interconnected separation of slurry after the first steps it is to recommend in the same RBC a nitrification step with a greater contactor diametre and a greater basin volume and higher specific surface of substrate material to reach a longer retention time.

In order to be able to realize by a simple arrangement the relatively high specific surfaces per material volume required according to the invention the material shown in Figs 2a, 2b and 2c can preferably be utilized. As is evident this material consists of conical, or isosceles triangulorly, regularly arranged embossings in a plastic material. This material is then used in several layers to build up a

RBC or a stationary biobed plant. In order to facilitate the build-up of the RBC's it is suggested in accordance with the invention that minor embossings serving as spacing means between the various plastic sheets or layers. The embossings are intended to coact with the tops of adjacent sheets. These minor embossings as well as the tops of the bigger ones are made so that a snap lock is obtained. In this way the need of adhesive or expensive spot welding of the material is eliminated. Glueing as well as welding of these materials may mean a weakening of the material immediately at the places of glueing or welding. This weakening might require that materials which are glued or welded must be dimensioned so that they are a little thicker than what is otherwise the case. The embossings are preferably circular, or triangular but other forms are of course possible incl. snaps.

The material sheets composed of plastic segment type RBC can be given final fixation by drawing two or more pull rods of a non-corroding material through holes prepared in advance right through the sheets which are forced together and fixed and a more stable and more handy segment will be achieved. In Fig 3 further embodiment of material shape is shown.

In accordance with a further development of the invention it is further suggested that the RBC material can be provided with a rough surface. In this way the shearing-off of microorganisms from the rotor surface will not result in the material grown microbiologically coming loose totally at the plastic surface. Instead, the strength of the very sludge will at last be so bad that this is broken loose. Therefore the material surface will never be quite clean which results in its turn in the continued groxvth on the same surface taking place more rapidly than what is otherwise the case, and the efficiency of plants made in this way is therefore Increased substantially.

The principles, preferred embodiments and mode of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed.

The embodiments are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations and changes which fall within the spirit and scope of the present invention as defined in the claims be embraced thereby.

Claims

WHAT I CLAIM IS:

1. A process of microbiological degradation of organic matter in continuously flowing wast water with a use of rotating biological contactor in one or more process steps, wherein the contactor is submerged in the water having the shaft above the surface of the water, the substrate of the contactor being dimensioned relative the water volume in the basin so that the water amount is 1-10 litres/m of substrate growth surface and that a substrate material is used having a specific surface of 150-400 m²/m³ material outer volume, and that the water volume is increased by increasing the width of the basin, and that in order to avoid water bypassing at least one shield is provided in each process step of the basin of the contactor.

2. A process in accordance with claim 1, c h a r a c t e r i z e d i n that one contacto r i s included a part with a greater diameter than what is used in the first process steps and that this is used as a last step in order to obtain nitrification, the greater diameter improving the nitrification degree

(more than 50%) by prolonged retention time and a choice of substrate surface with 300-400 m surface per m ³ outer volume.

3. A device carrying out the process in accordance with claim 1 or 2, c h a r a c t e r i z e d i n that it includes rotating biological contactor submerged in a basin with its shaft above the water surface (a submerging degree between 40-48% ) in such a way that "short circuiting" or "by passing" is not possible of untreated water within the separate process step of both sides of the contactor, and that relations in accordance with claims 1 or 2 exist for water volume and substrate surface.

4. A device according to claim 3, wherein the substrate material in a contactor is designed as vacuumformed protrusions of which a sufficiant number further has been provided with snap locks or similar parts designed to grip into the adjacent layer of substrate material to be glued or welded to this.

5. A device according to claim 3, c h a r a c t e r i z e d i n that the substrate material consists of separate plastic sheets, the outer edges of which are angeled in order to improve stability for each sheet.

6. A device according to claim 3, wherein the segments of plastic in the contactor is constituted by a great number of discs and that the entire segment package beside the snap lock are fixed relative each other by some rods extending through holes in the discs.

7. A process according to claim 1, wherein the amount of water is 2-8 litres per m² substrate surface and the specific surface of the material is

200-350 m per m material volume.

8. A device according to claim 3, c h a r a c t e r i z e d i n that the amount of water is 2-8 litres per m substrate surface and the specific surface of the material is 200-350 m² per m³ material surface.