EP0195005A1 - Method and arrangement for growing microorganisms and causing contact between gas and/or liquid medium and contact elements - Google Patents

Abstract

Process for cultivating microorganisms and producing contact between a medium and / or liquid and contact elements, the medium and the contact elements mixing by bringing the medium into contact with the contact elements of higher density and density lower in the middle. The best contact is obtained by rotating the containers which can be linked together for a gradual treatment, turned in different ways and containing contact elements of different size, density and relative number depending on the nature of the medium and the treatment progress. The rotation is caused by a displacement of weight inside the containers. In the first stage, for example, a partially perforated cylinder (1, 2) is provided with longitudinal shovels (8) allowing the gas produced in the cylinder to press the fluid, which causes a radial displacement of the weight and a rotation. The cylinder is fitted in a surrounding container (3) at a certain distance therefrom. This distance is reduced by a propeller (4) placed around the rotary cylinder. The propeller partially directs the medium among the contact elements in the outer cylinder while partially advancing the solid particles having passed through the perforations. In another step, the particles are collected at the top of an essentially vertical container, so that the light contact elements are pushed into the bottom of the container and cause a displacement of weight, rotating the container around. an axis (18) located halfway up the container. In the upper part of the containers, the light contact elements are collected and compressed forming a filter (25). In the containers and the cylinders are arranged deflectors (5) guiding the medium to pass over an optimal number of contact elements during the treatment. This procedure and this device are particularly useful in purification and

Description

Method and arrangement for growing microorganisms and causing contact between gas and/or liquid medium and contactelements

The present invention concernes a method and arrangement for growing of microorganisms and causing contact between a gas- and/or liquid medium, especially in connection with waste-water treatments and plants for production of biogas. As the supply of imported fuel reduces and the prices hereby increases, the interest of taking care of domestic energi sources will increas. Such an important energy source is waste- water from communities and industries, which is often rich in organic material. Through anaerobic fermentation of this organic materials, biogas, i.e. methane and carbon dioxide can be produced. At present there are a few establishments for production of biogas in Sweden, but the interest is increasing and some research is going on to get more effective and more commersially profitable establishments. A plant for treating of waste-water which is now in use comprises of a hydrolysis reactor, a sludge separator and a submerse filter. In the hydrolysis reactor, which is a container provided with stirrer, carbon dioxide is composed. After having passed the hydrolysis reactor the waste-water reaches the sludgeseparator, and thereafter part of the sludge is taken out of the process and part of it recirculates to the hydrolysis reactor.

The waste-water cleansed from sludge takes along for rotting in the submerse filter, which is a container with contactelements, which can consist of any inert material, such as stone, sand, plastic. By using contactelements the rotting time will be reduced to less than half the time used in rotting without contactelemnts, that is approx. 9 days against 20-24 days (in rotting without contactelements). The microorganisms will stick on the contactelements andthere will be a large contact area towards the waste-water. The problem with this wellknown arrangement is obstruction of filters and a lumping of the contactelements.

Because of the problems with an effective slurry separation there is now another type of establishment with direct rotting of the sludge in two steps. In the first step there is a mesophil rotting at a temperature of 33-40ºC for about 10 days and in another step a termophil rotting at 50-60°C for about 10 days. Thus there is a time of about 20 days which is a great disadvantage for this type of process. Trials have also been made with fluidizing and expanding beds of contactelements for treating sewage. These beds can be described as submerse filters where the dirty water flows in from below with such a speed that the contactelements will be lifted up (more in a fluidizied bed than in an expanded) and prevent obstructions, at least until the contactelements have lumped together, which will happen after some time. The reasons why fluidizing beds have not been practically used are the difficulties to take away and cleanse the contactelements, infected with bacteries, and demands od exact density and flow of incoming waste-water.

In Swedish application for at patent nr 8005865-5 is also indicated the use of contactelements with higher and lower density than the medium. But these are placed in limited spaces which prevents friction between the contactelements of unequal weight. The purpose with the present invention is to make a new method and a new arrangement to take care of the advantages by using contactelements, a simple way to reroll them and avoid the disadvantages. Thus the present invention comprises a way to grow microorganisms and cause contact between a gas- and/or liquid medium and contactelements, a way characterized by mixing of medium and contactelements. This will be done by putting the medium in contact partly with contactelements having higher density than the medium and partly with those which have lower density than the medium in containers, which are partly turned radially by displacement of wheigt, when gas, made free by cultureprocess or brought into the container, is caught by on the inside of the container applied shovels and stirrers and there exerts elevation, and partly axially by displacement of weight arising by collect- ion of particles in one end of the container.

Separating of particles and/or rotting gradually takes place in separate containers thus for instance in one container particles and/or organic material will be collected and/or rotted to some degree, after which the medium with a pump or pressure in a conduit is transferred to one or several containers where in the medium remaining particles and/or organic substance will be kept and/or rotted.

By treating media with variable size of particles, e.g. kitchen waste, the first step can for instance consist of a cylinder (1,2) arranged in a surrounding tank containing relatively big contactelements. Some of the smaller particles will pass the arrangement relatively untreated through the outflow (23) further on to the next step e.g. a mainly vertical reservoir supplied with for instance small lighter and big heavier contactelements.

Sixe, density and relative number of contactelements can vary in the different containers depending on the medium which is to be treated and how far the treatment has proceeded.

To get the wanted rerolling also the way of rotation in the different steps can be varied.

The variation of contactelements in combination with different rotation methods, will give media with varying size of particles optimal contact area.

Separation of particles will accur partly by that particles which has been stucked on the contactelements will fall off them and after eventual rotting will be feeded out of the arrangement either with a feeding screw and/or by sedimentation through outflow in the containers, partly by that some contactelements are kept in the upper part of the containers (1,17) and by the flow and/or elevation power of the medium will be pressed together becoming separators of particles in gas and/or liquid flowing through the outflows.

This method can be applied as well by treating fluid like waste-water and - sludge, as for instance purification of gases. In one form of execution of the invention there has deposited micoorganisms, especially methangas producing bacteries on the surface of the contactelements. The microorganisms are growing on the contactelements and, when growing, organic material is destructed by producing so called biogas. With the present invention it is possible depending on the characters of the medium to use contactelements with different density, both such flowing on the liquid which will be treated and such sinking in the liquid. In this way there will be a better mixing of the medium which will be treated by rotation of the container. The heavier elements are sinking the lighter are rising and so there will be to some extent a friction between the elements preventing sludge or dust to stick to and between the elements in a way that obstruction arises. In addition, the appearance of a monolayer of microorganisms on the contactelements is supported and because of that a big contact area.

The invention also comprises an arrangement for performing the method, characterised by including revolving containers where especially the first one in the step consists of a cylinder (1), with partly perforated outer mantle (6), mounted in an outer container (3) in a distance from the inner wall of the outer container (3). On the outer surface of the cylinder and between this one and the outer container (3) there is a helical tightening and feedingscrew (4) running along the cylinder. In the cylinder (1) one or several shovels and carriers (8) are arranged for rerolling of the medium and the contactelements and radial torsion of the cylinder (1) through gas, which is produced by the bacteries or will be lead into the cylinder (1). Separation of particles will go on in the upper part of the outer container (3) consisting of contactelements kept in the container (3) of a filtercloth or a net. The second step in the treatment can consist of a container (17) preferably containing smaller but a greater number of flowing contactelements and smaller number but heavier contactelements for more effective separation of particles and/or rotting than in step one. In the container (17) there will be a displacement of weight by incoming media partly will stick in the upper part of the container. The volume of the medium assisted also by the flow will gradually force lighter contactelements down into the lower part of the container so this one becomes lighter than the upper part. As the containers can lean the upper part weighs down and the lower part lifts up and the container will turn. Now the contactelements redresses the balance and partly directed by baffles they cause a stirring in the container as the light contactelements flow up and the heavy ones are sinking in the container. The same principle of stirring is true for step one in the cylinder (1) where the carriers, shovels are pulling the contactelements up respectively down.

The invention will be further described by aid of the drawing figures in which Fig. 1 shows a form of execution of the arrangement for the performance of for instance step one. Fig. 2 shows the arrangement according to fig. 1 in section. Fig. 3 shows another form of execution of container (3) and cylinder (1,2) in section. Fig. 4 shows a form suitable for instance for step two according to the invention. Referring to fig 1 an arrangement according to the invention comprises a rotatory cylinder, with partly perforated outer mantle, divided in two connected parts 1 and 2. This cylinder 1,2 is placed in an outer surrounding container 3 in a distance from it. On the mantle surface of the inner cylinder there is a helical tightning 4 between the outer container and the inner cylinder. Baffles 5 are arranged partly between the parts of the inner cylinders, extending into the inner part of the cylinder and out towards the outer container 3 and is tightning towards it, partly within the cylinder guiding media and contactelements. The tightening 4 has two important functions in the invention. Partly it is arranged to prevent liquid alluvion etc which will be treated in the inner cylinder, to pass this and flow into the space between the outer container ans the cylinder and pass out of the arrangement untreated. The other important function of the tightening is to feed rotted material forwards. This material is piercing the perforation of the mantle surface of the cylinder and enters the room between where it will be feeded towards the outflow of outflows.

Also the ends of the inner cylinder can be perforated to permit percolation of the liquid alluvion but prevent the contactelements to pass out of the inner cylinder.

The outer container is closed with the exception of necessary in and outflow for material which will be treated, gas, cleaned liquid, rotted material etc. At 23 there is for instance an outflow for rotted material which has been collected along the mantle surface of the inner cylinder and has been feeded forwards as mentioned above. The mantle surface of the cylinder 1,2 is partly perforated 6 and partly gastight 7. The gastight parts 7 of the mantle surface makes the outer part of a number of shovels and carriers 8 arranged inside the inner cylinder as shown in fig. 2.

The inner cylinder 1,2, is rotatable in the direction of the arrow 9 and supplied with oblique baffles 5 guiding media and contactelements for optimal contact with each other.

In the arrangement there are contactelements, which can possibly recirculate together with a part of the medium. The possibly recirculated contactelements are those which are smaller than the holes in the perforated inner mantle.

The material which is to be treated will be lead in at for instance 10, possibly together with recirculated contactelements. A smaller part of treated liquid alluvion and prospective contactelements for recirculation proceeds from 11 via tubes through the container 3. Rotted sludge will be piercing the perforations 6 of the mantle surface of the cylinder 1,2 into the space between the inner cylinder and the exterior container. By the tightening 4 the sludge is driven forwards along the axle of the cylinder and part of it forced back through the perforation into the cylinder 1,2 where it acts as contactelements until they are finally feeded out ar for example 23.

The arrangement can also be used only as a filter for gas or liquid, when one or more of the proceeding ways of emptying can be applied and separated material can be transferred to the next step of the treatment.

Fig. 3 shows how the mixing is caused when the drum rotates in the direction of the arrow 13, so that the contactelements are brought by the shovels and the carriers 8 and are mixed further more as lighter contactelements 14 rises after the turning and heavier contactelements 15 is sinking. Rotted silt 16 will be forced out and in through the perforations and is feeded forwards by the helical tightening in the space between the cylinder 1,2 and the container 3.

The rotation of the cylinder 1,2 is caused by gas, produced by the rotting, which will raise and be collected in the shovels 8, where it exerts an elevating power because the shovels having a gastight surface out against the mantle of the cylinder. This elevating power can be increased by a gas being conducted from outside. Fig. 4 shows a type of container suitable for step 2 according to the invention. This type of container may also be used before step one if it is provided with relatively big contactelements and there treat and/or retain some particulary bigger particles and therefore relieve step one. It can also be used for separation of dust from gascompounds in other connections than rotting

The container 17 is axially rotatory arranged to be turned to and fro to half a turn round a horizontal axis 18. The containers may have variable inclination. In the ends a resp. b there are for instance outlet pipes 19 resp 20 for cleansed gas and/or liquid and a strain 21 to keep contactelements 22 which catch and retain particles and contactelements on the way of the medium through the container. When the container is in the position shown in the left part of fig. 4 gas, mixed with dust or liquid alluvion which will be treated is lead in through one or more conduits 23 or 24, and treated liquid and/or gas and sludge will be taken out through one or more conduits 19,24,23. When the arrangement has been in operation for some time there will be obstructions and the percolation will be bad. The collection of particles which now takes place in the upper part of the container will press down most of the light contactelements. Then the upper part of the container, a, becomes heavier than the lower part, b, which makes the container turn by the displacement of wheigt so the end b comes up and the end a down, as is shown in the right part of fig. 4. Consequently the in and outlets for gas resp. liquid alluvion will be reversed. In this way a self-cleaning filter is achieved. Of course the container can also be turned manually or with an engine if the percolation will be intensified. By taking out or let in the medium and/or the contactelements in different places along the containers it is possible to get different degrees of filtering effect respectively rotting effect. That part of the medium and/or the contactelements which is taken out along the mantle surface of the container will mainly be cleansed/filtered, but such material which will be left in the container towards the end of the outflow will stay a longer time in the containers and will therefore to a greater extend be rotted.

In the containers of the two steps of the arrangement, there can be carriers and baffles of several types. There can also be intermediate partitions and nets or strainers to keep contactelements. A filtering cloth can be arranged around part of or the whole inside of the container.

To facilitate rotting of organic material heating can be arranged along the whole or parts of the length of the container, for instance along the ends of in and outflow. The material which will be treated can also be heated before it is put into the container in special arrangements, also areobic.

The order of the steps can be changed as well as a greater number of containers can be connected in a serie or parallell with each other eventually via sedimentation vessels or be used separately.

The medium and the contactelements, or part of them can also be recirculated through the whole arrangement or through one or more parts of it, and so can also media with a relatively high dry substance be treated.

Claims

WHAT I CLAIM IS: 1. A way to cultivate micrcorganisms and causing contact between a medium in the form of gas or fluid and contactelements, c h a r ac t e r i z e d by mixing of medium and contactelements and friction between them in containers, will be caused by a medium which is partly put in contact with elements having higher density and partly with such having lower density than the medium. This will take place in containers which will turn through displacement of weight which will take place as the passage of the medium through the container(s), at which some of the lighter contactelements will be pressed together towards the upper part of the container(s) an so they constitute a filter preventing solid particles (pollutions) to follow liquid and/or gets out of the container(s).

2. A way according to claim 1, c h a r a c t e r i z e d by contact being produced between contactelements, on which surface of and space between there are micrcorganisms, and an organic substrate for cultivation of the microorganisms.

3. A way according to claim 2, characterized by the microorganisms being methanproducers.

4. Away according to claim 1, charac ter i ze d by a medium in gas-form which containers pollutions will be brought in contact with the contactelements on the surface of which the pollutions are left.

5. A way according to claim 1-4 ch a r a c t e r i z e d by a step-by-step treatment in containers in connection with each other for a gradual separation of solid particles and/or rotting. The containers will be turned in different ways and are provided with contactelements of different size, density and number depending on the kind of the medium and/or how far the treatment has proceeded.

6. Arrangement for separation and/or rotting for instance of bigger particles according to claim 1-5 ch a r a c t e r i ze d by involving one or several radially rotatory cylinders, (1,2) with partly perforated outer mantle (6) erected in an surrounding container (3) at a distance from the inner wall of the surrounding container (3), and on the surface of the cylinder(s) and between it/them and the outer container (3) a helical feeding screw and tightening is arranged passing round the cylinder. In the inner cylinder(s) one or more shovels (8) are arranged partly for rerolling of the medium and the contactelements and partly for rotating driving of the inner cylinder by gas, set free by the produced contact and/or lead into the inner cylinder(s). The surrounding container is at the top formed in a way that some contactelements are kept there and of the medium pressed together for separation of particles from gas and water. A filtering cloth is applied before the outlets of gas and/or fluid to retain the contactelements.

7. Arrangement for separation and/or rotting of for instance smaller particles according to claim 1-5 c h a r ac t e r i z ¬e d by container for separating solid material from a mixture of gases and/or microbiological treatment of liquid alluvion comprises one or several mainly vertical containers (17) which are rotatable arranged on a horizontal axis (18) located at half the height of the container(s), and the upper part of this one is weighed down by particles which are collected at the top of the container(s) and so they press down most of the lighter contactelements resulting in the fact that the upper part will be heavier than the lower part and the container(s) will turn. They also have arranged in- resp. outlets (19,20,23,24) for material which will be filtered, filtrate, gas and contactelements.

8. Arrangement according to claim 6-7 c h ar a c t e r i ze d by that the rotation of the containers is caused manuallu or with an engine.

9. Arrangement according to claim 6-8 c h a r a c t e r i ze d by that the container(s) and the cylinder(s) are supplied with baffles to give an optimal contact between medium and different types of contact elements.

10. Arrangement according to claim 5-9 c h a r a c t e r i z e d by that a pump or pressure difference will recirculate the medium and/or the contactelements through one or more of the containers.