SE441595B - DEVICE WASTE CLEANING MEDIUM ANAEROBIC FERMENTATION - Google Patents

Description

It is previously known to digest anaerobic wastewater sludge which contains biodegradable organic material in a two-stage digestion mortar, in which both stages have been fitted inside each other. For example. In Finnish patent 57579 a device is thus known for digesting sewage sludge in two successively connected stages, which are fitted inside each other, wherein sludge water and digested sludge, part of which is led back to the first stage, are removed from the second stage. . In this type of reactor, digestion can still not be carried out separately by means of two bacterial traps of different kinds, since these would automatically be mixed with each other, as a part of the sludge from the second stage is led to the first stage as inoculation sludge. In fact, this device thus refers to a totally mixed reactor, although it has been divided into two interconnected stages.

It is clear that the disadvantages caused by the totally mixed reactors can be eliminated by using two separate reactors, which are connected to a series, the first of the reactors acting as an acid stage and the second as a methane stage. Such a device would still be relatively expensive and complicated in comparison with a totally mixed reactor and in addition it would require more space. The object of the present invention is thus to provide a device for purifying waste water by means of anaerobic fermentation, in which device acid and methane reactions can be carried out under the conditions which best suit these reactions, without the acid and methane bacteria being substantially mixed with each other, and which device still in large -graa is as cheap and enlel as a totally mixed reactor.

The main features of the invention appear from the appended claim 1. A device according to the present invention is very simple and economical, since both acid and methane reactions are carried out together and in the same vessel. Both acid and methane reactions can be realized in the device according to the present invention under near optimal conditions and without significant admixture of acid and methane bacteria, since the vessel has been divided into two parts on top of each other by anaerobic filter comprising a creeper layer containing one or more layers of porous fillers. acts as a fastening base for the methane bacteria, whereby each filler layer can be either inert or active independent of the properties of other possible filler bodies. The acid reactions then take place in a stirring section under a filter, into which the waste water to be purified is ingested and from which the waste water after acid reactions together with gas formed during the acid reactions rises to a part above the filter and reacts immediately with the methane bacteria which are present. both on the surfaces of the filter filler bodies and in the upper part of the filter. Some of the sludge removed from the stage below the filter can be recycled back to the reactor, but then to the same stage, not mixing it with the sludge in the second stage, as in the solution according to Finnish patent 57579Ä Directly below the filter there is a in a separate lamella separator for dividing water flowing upwards through the filter upwards from the filter evenly over the filter, for enlarging the bubbles in water and for separating and recirculating the sludge particles to the stage below the filter.

Gravel, light gravel (leca-gravel), plastic particles and various porous materials such as coke, coal, slag and activated carbon can be used as fillers for the anaerobic filter. Advantageously, however, light gravel and slag were used, to the surfaces of which metsnbskterierss adhere. A large total area of said material increases the attachment possibilities of the methane bacteria. _. , e .._.__._._:.-_...... -___ ...__........._......-._-_ .. Above the anaerobic filter a relatively thick fluidizing layer is maintained, which is formed of sludge and possibly of filtering and / or fluidizing materials such as activated carbon, ash, especially fala ash, sand or mud. When activated carbon was used as a filter and fluidizing material according to the present invention, the surprising observation was made that activated carbon was regenerated by itself.

Activated carbon has previously been used as a filler for the anaerobic filter - according to German application publication 2531598.

According to this method, the wastewater has been purified by means of the anaerobic filter, in which activated carbon has been used as the filler body, and subsequently also by means of aerobic treatment.

This method has been tested under different conditions and it has been possible to purify wastewater and sludge by means of it, but the gas production has been relatively low and in addition activated carbon has to be replaced from time to time, which has made treatment more difficult and caused interruptions in production. In the device according to the present invention, it is not necessary to exchange activated carbon, which was used as a fluidizing material, which was a very surprising observation. The cause of this effect is not known. Thus, it is not necessary to replace activated carbon used as a fluidizing material in the device of the present invention because its filtering ability would be weakened. During the acid step, toxicity-removing materials, such as activated carbon, can also be used.

The invention is described in more detail below with reference to the accompanying drawing, in which: Fig. 1 shows diagrammatically in cross section a preferred embodiment of the invention in vertical section and Fig. 2 shows a similar alternative embodiment of the invention in vertical section.

S ssoosvo-2 In the drawing, number 1 generally refers to a vertical cylindrical reactor. In the embodiment shown in Fig. 1, a vertical cylinder 10 is centrally fitted on the inner side of the reactor 1, which is open from its upper and lower ends. On the inner side in the upper stage of this vertical cylinder 10 a vertical pipe 12, open from both ends, has also been fitted, into which a stirrer 11 extends from the upper part of the reactor 1 and to which a: pipe 2 for the waste water to be purified : hums outside the reactor l.

In addition, the reactor 1 has been divided into two stages one above the other by means of a filter 8, through which the vertical cylinder 10 extends so that the waste water led through the feed pipe 2 to the cylinder 10, which is to be purified and stirred by means of the stirrer 11, sinks to a part below the filter 8, in which it is still stirred by means of the stirrer 4 to prevent the acid-forming bacterial slurry from sinking to the bottom of the reactor 1. In the lower part of the reactor 1 there is also a drain pipe 3 for the reduction of the slurry length, from which a pipe 13 branches , in which there is a pump 14 for feeding sludge which has been removed from the acid phase of the reactor 1, together with the waste water to be purified, from the feed pipe 2 to the stirring pipe 12 present in the vertical cylinder 10. In the vertical cylinder 10 and in the vessel part under the filter 8, acid-forming bacteria react with the wastewater, which contains organic matter and forms sludge and gas.

Directly below the filter 8 is a lamella separator 15, in which water is forced to flow from below between inclined lamellae upwards to divide water evenly over the entire cross-sectional area of the filter 8, to enlarge the gas bubbles in water and to separate and return existing sludge particles to the water. under the filter p. 8300570-2 The anaerobic filter 8 contains inert filler bodies, such as light gravel and / or slag, which act as a fixed base for the methane bacteria and which have a large surface area for the slow-growing methane bacteria to be washed away. On the filter 8 there is a relatively thick sludge and fluidizing layer 9 for more efficient actual fermentation, whereby for this reaction step a larger and more evenly divided microbial culture is obtained. Activated carbon is used as the fluidizing material, which also acts as a filter. In the step above the filter 8, further methane gas is formed and the gas is separated from water and slag mixture with oblique surfaces by a bubble separator 7 fitted on the upper part of the reactor vessel 1. The purified waste water and the sludge present therein are finally led out of the reaction vessel 1 by the effluent above the bubble separator 7, and the gases separated in the bubble separator 7 are removed through the drain pipe 6 at the upper end of the reaction vessel 1.

Fig. 2 shows a somewhat simpler embodiment of the device according to the invention, in which the waste water to be purified is led directly by means of the pipe 2 to the lower part of the reactor 1, which is separated from the upper part by means of the anaerobic filter 8. Excess sludge is removed from the lower part of the reactor 1 by means of the drain pipe '3- In the upper part of the reactor 1, on the other hand, there are means 7 for separating gas from the mixture of the treated wastewater and sludge, before the water is removed by the drain pipe 5. With waste water with particularly difficult purification the gas bubble separator can be improved. 12 fitted on. upper part of the reactor. The gases are again removed via a pipe 6, which is placed centrally on the upper part of the reactor.

By means of the device according to the present invention, better purification results and greater tolerance for toxic materials are obtained, then. activated carbon is used as a filter and fluidizing material, because it surprisingly retains its usual filter flux, in other words regenerates by itself, whereby it does not need to be renewed. The device according to the invention is furthermore very simple and inexpensive, since the investments and other ancillary costs are small and the operating costs are low. Example 3 A multi-stage reactor according to the invention has been compared with the previously known total mixed reactor with respect to the purification result. With the multi-stage reactor according to the invention comprising an acid fennation step, lamella separator and above it a filter and fluidizing part within the methane fennation step, a noticeably smoother purification result has been obtained than with the totally mixed reactor, in which both acid and methane refraction take place during the same reaction.

Leca gravel and activated carbon chewing gum were used as a filler body in the multi-stage reactor according to the invention. The liquid volume of the reactor was 30.8. liters and the temperature during sample was 34 days; 1 ° C. The pH of the effluent which was rerxed, adjusted neutrally or for pH7.

The total mixed reactor of the same size and the same sample range was used as in the above-mentioned multi-stage reactor. The results shown have been shown in the table below. ovarmänxrzda reactor types. The table shows that the multi-stage reactor has a noticeably better EST reduction (on average 80%) than the total mixed reactor (on average 50%). The multi-stage reactor had a better OODCr reduction, also gas production.

Table They use the quantities between the multi-stage and the totally mixed reactors as comparison parameters.

Multi-stage reactor Total mixed reactor: ag reduction: d eo so 8300571142 s BS-ï value mg / l wastewater iso _ soo-eoo coDCr reaction a * so _ 45 Gas production m3 / kg B87 add 0.20 0.15 uptime, days 150 135 xBS ~ reduction: 7 CODCr reduction: reduction of (mg 02/1) biological oxygen burning during 7 days zránskráng or reduction (m9 chemical oxygen burning 02/1) of the Gas production and BS7 reduction levels have been varied in both reactors according to the properties of the wastewater.

When the impact of toxic wastewater was investigated, the ßS7 reduction rate was higher than average, because the quality of wastewater used was consistent during the investigations. The effect of toxic water on the reactor's function was evident from the usual results in the reactor's operation. The multi-stage reactor BS7 reduction, which was at the beginning of this test about 90%, dropped from here, when toxic wastewater was treated, to the level of about 70% and recovered, when the toxicity of wastewater stopped, to the reduction level of about 90%. The ßreduction of the total mixed reactor decreased the initial level of 80% to the level of about 30% and recovered from the corresponding afterwards only to the reduction level of about 70%. This proves that toxic wastewater has a stronger effect on the operation of the totally mixed reactor. Instead, the operation of the multistage reactor according to the invention was constantly noticeably smoother. This shows the noticeably better ability of the multi-stage reactor to withstand toxic wastewater. 9 8300570-2 Despite the long operation of the multi-stage reactor (150 days), the purification result did not change, although the hydraulic residence time was gradually shortened. Aktivkcl did not need to be renewed to improve the purification effect, as was previously customary.

Claims (1)

8500570-2 Patent claim Device for purification of wastewater by means of. anaerobic fermentation comprising an acid and a methane fermentation step, comprising a closed vessel (1) and therein means (2, 10) for feeding the waste water to be purified into the vessel, means (5, 6, 3) for removing purified water, gas and sludge from the vessel, means (4) for agitating the contents of the vessel and means (7) for separating gas in the upper part of the vessel, characterized in that the vessel (1) has to. keep the acid and methane fermentation steps substantially separated from each other divided into two superimposed parts by means of a filter (8) comprising a filler body layer containing at least one filler body material, which acts as a fixed support for the methane bacteria, and on this a sludge and fluidizing layer, so that in the lower part of the vessel below the filter is the first part, in which the stirring means (4) are located and in which the supply means (2, 10) for the waste water to be purified, opens, the acid fermentation step taking place substantially in the first part and in the upper part of the vessel is the second part, in which the drainage means (5, 6) for purified water and gas open, and to which belongs the filter (8), the methane fermentation step taking place substantially in the part. Device according to claim 1, k ä characterized in that under the filter (8) there is a lamella separator (15) for dividing water flowing downwards through the filter upwards nt in addition to the filter and for enlarging existing bubbles in water and for separating and recirculating sludge particles to the first source part under the filter. Device according to claim 1 or 2, characterized in that the means for supplying waste water to be purified comprise a centrally fitted on the vessel (1) and from its upper and lower end open cylinder (10), which extends from above the means (7) present in the upper part of the vessel for separating gas downwards through the filter (8), and the means (2) for inlet of the waste water to be purified to the upper part of the cylinder (10). Device according to claim 3, characterized in that in the upper part of the cylinder (10) and advantageously in the middle thereof there is a stirrer (11), which is surrounded by a vertical pipe (12) open from both ends. , with which the supply means (2) for the waste water to be purified has been connected. Device according to one of the preceding claims, characterized in that in the first vessel part under the filter (8) there are means (3) for removing sludge and possibly for partial return (13) of sludge with the waste water (2), which is fed into the vessel (l) for purification. Device according to one of the preceding claims, characterized in that the filling body layer present in the filter (8) contains gravel, preferably light gravel. Device according to one of Claims 1 to 5, characterized in that the filling body layer present in the filter (8) contains slag. Device according to any one of the preceding claims, characterized in that the fluidizing material is activated carbon, which also functions as a filter material.