JPH08182998A - Decompostion of fats and oils in oil-containing waste water - Google Patents

Abstract

PURPOSE: To efficiently decompose fats and oils in an oil-containing waste water by anaerobically treating a digestion sludge collected from a methane fermenter in an oil- containing culture medium to separate and cultiate an anaerobic and oils decomposing bacterium and proliferating the cultivated anaerobic fats and oils decomposing bacterium in the methane fermenter into which the oil-containing waste water is to be fed. CONSTITUTION: The anaerobic fats and oils decomposing becterium is separated and cultivated by treating the digestion sludge collected from the methane fermenter 1 in the oil containing culture medium under anaerobic condition and the cultivated anaerobic fats and oils decomposing bacterium is proliferated in the methane fermenter 1 into which the oil-containing waste water is to be fed. That is, a porous granular unwoven fabric carrier on which the anaerobic fats and oils decomposing bacterium is stuck is fed to the methane fermenter 1 to form the unwoven fabric carrier layer 2. For example, a garbage raw material is fed to the methane fermenter 1 from a raw material tank 3 by using a pump 4 and is methane-fermented at about 55 deg.C while circulating the raw material in the tank by using a circulating pump 5. Since the anaerobic fats and oils decomposing bacterum is proliferated at pH 6-8, it can proliferate by only once addition to the methane fermenter 1 while treating the waste water. Accordingly, special control is unnecessary.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for decomposing oil-containing wastewater discharged from various living and business systems.

[0002]

2. Description of the Related Art Waste water from food factories, cafeterias, and households often contains a large amount of fats and oils. The presence of fats and oils in wastewater causes various problems in sewers and wastewater treatment facilities.

For this reason, oil and fat separation facilities (grease interceptors, etc.) are provided in food factories, restaurants, buildings, etc.
Oils and fats are removed from oil-containing wastewater. The wastewater from which the oils and fats have been removed is directly treated in the septic tank, or is further treated in the septic tank after the oils and fats have been further removed by a separate oil / water separator.

Further, a technique for utilizing a microorganism to aerobically treat oil-containing wastewater as it is has been developed. This method is an improvement over the conventional activated sludge method, in which microorganisms that decompose fats and oils are put into an aerobic treatment tank in advance, and the oil-containing wastewater is treated there.

Such oil-and-fat-degrading bacteria include those belonging to aerobic bacteria and those belonging to anaerobic bacteria. As the former bacteria, for example, the lipase-producing bacterium Bacillus sp. No.
351 and Pseudomonas sp. No. 6 have already been isolated.

[0006]

Generally, fats and oils solidify into balls or form sludge-like scum on the surface of waste water, which causes troubles at facilities such as pump stations. When the oil and fat in the waste water is separated by the conventional oil and fat separation facility (grease interceptor, etc.), the facility must be cleaned several times a week. If not properly cleaned, fats and oils may leak from the facility, leading to environmental pollution. Some facilities did not clean at all based on the survey results of the actual cleaning status of the oil and fat separation device. Further, since most of the separated oils and fats are disposed of by incineration, there is a problem that the cost for incineration increases.

In the method of treating oil-containing wastewater by aerobic treatment, which is an improved method of the activated sludge method, it is said that the activated sludge treatment becomes difficult when the fat and oil concentration becomes 100 mg / liter or more. In other words, it is difficult to evenly suspend the fats and oils in the tank, and as the concentration of fats and oils increases, the processing capacity decreases.
There is a problem that it is difficult to apply to wastewater containing oil and fat at a high concentration. In addition, when treating oil-containing wastewater by aerobic treatment, it is difficult to uniformly suspend fats and oils, and the treatment capacity decreases as the concentration of fats and oils increases. The principle is the same as in conventional activated sludge treatment. Therefore, there are problems that energy consumption such as aeration power is large and that excess sludge is generated.

As described above, the conventional fat and oil treatment of oil-containing wastewater has various problems in terms of maintenance, treatment method, treatment capacity and the like. The present invention is intended to solve such a troublesome problem.

[0009]

According to the present invention, digested sludge collected from a methane fermentation tank is treated in an oil-containing medium under anaerobic conditions to separate and cultivate anaerobic oil-degrading bacteria, and the cultured anaerobic oil and fat. Provided is a method for decomposing fats and oils of oil-containing wastewater, which comprises proliferating degrading bacteria in a methane fermentation tank into which oil-containing wastewater is charged. Here, in the methane fermentation tank into which the oil-containing wastewater is charged, it is preferable to suspend the granular non-woven fabric carrier on the liquid surface.

[0010]

[Function] Anaerobic fat-and-oil-degrading bacteria also inhabit the digested sludge of a normal methane fermentation tank used for garbage treatment. This anaerobic oil-degrading bacterium can be separated and cultured by treating it with an appropriate oil-containing medium under anaerobic conditions. If the anaerobic oil-degrading bacteria are grown in a methane fermentation tank while the oil-containing wastewater is being added, the input oil-containing wastewater is decomposed and the oil and fat components can be efficiently removed.

Since the anaerobic fat-and-oil-degrading bacteria grow at a pH of 6 to 8, the anaerobic fat-and-oil decomposing bacteria grow while treating the wastewater by adding it once to the methane fermentation tank. Therefore, no special management is required, and only maintenance similar to normal methane fermentation is required. Aeration power is not required unlike aerobic treatment, and excess sludge emissions are small. In addition, it is economical because it can recover methane gas as an energy source.

In carrying out the present invention, when a porous and granular non-woven fabric carrier is floated on the liquid surface of a methane fermentation tank, the oil and fat in the oil-containing wastewater has a property of floating near the liquid surface of the treatment tank. Therefore, the chances of contact between the oil and fat near the liquid surface and the anaerobic fat-decomposing bacteria adhering to the non-woven fabric carrier increase, and the proliferative activity of the anaerobic fat-decomposing bacteria becomes active through this porous carrier, and Decomposition proceeds more efficiently, and oil-containing wastewater containing oil and fat at high concentration can be easily treated.

As the porous granular nonwoven fabric carrier, a porous sheet composed of glass fiber or plastics fiber is used as a lightweight plastics granular body (preferably having a diameter of 5 to 5).
It is preferable to cover it around a 60 mm granular body,
Float this in sufficient quantity to cover the liquid level in the tank with one or more steps. The porous sheet (nonwoven fabric) made of glass fiber or plastics fiber has a high ability to fix microorganisms, and there is no risk that oil-degrading bacteria fixed to this will flow out. And
By using lightweight granular plastics such as hollow plastics and plastic foams as the core material for holding the porous sheet, the nonwoven fabric carrier can be freely flown and suspended in the tank and the cores Plastics as a material also functions as a microorganism carrier.

[0014]

【Example】

In the following examples, the analysis of the components of waste water was based on the Industrial Waste Water Test Method (JIS K 0102).

[Example 1] 0.5 ml (milliliter, the same applies hereinafter) of high temperature methane fermented sludge after garbage treatment was sampled,
100 ml of the medium shown in Table 1 was inoculated. This medium was used after being sterilized by an autoclave at 120 ° C. for 20 minutes. For culturing, use an anaerobic jar fermenter 55
The cells were cultured at 0 ° C for 2 weeks. Since the culture was carried out in the same atmosphere as in the methane fermentation tank, the gas layer was cultivated while aeration of gas of CH ₄ : CO ₂ = 7: 3.

After this culture treatment, 0.5 ml of the culture solution was added to Table 2.
The medium was inoculated into 100 ml of the medium shown in, and tested for the presence or absence of oil and fat degrading. Regarding the oil and fat degradability, the change with time of the n-hexane extract was used as an index. The result is shown in Figure 1.
It was shown to.

[0018]

[Table 1]

[0019]

[Table 2]

As shown in FIG. 1, the n-hexane extract gradually decreased after inoculation with the anaerobic oil and fat decomposing bacteria, and was reduced to 10% or less 2 weeks after the inoculation with the anaerobic oil and fat decomposing bacteria. . From this result, it is considered that the anaerobic oil-and-fat-decomposing bacteria separated by this method were able to remove the oil and fat by 90% or more.

[Example 2] The anaerobic fat-and-oil-degrading bacteria isolated in Example 1 were inoculated into the same medium shown in Table 2 above and grown at 55 ° C to give a bacterial concentration of 1 x 10 ⁸ cells / ml. By the way, we put in a non-woven fabric carrier with a diameter of 2 cm, and
After culturing for a week, anaerobic fat and oil decomposing bacteria were attached to the carrier. This non-woven fabric carrier is one in which a non-woven fabric sheet made of glass fiber is adhered around hollow resin balls.

The non-woven fabric carrier to which the anaerobic fat-and-oil-degrading bacteria have been attached in this manner is shown in FIG.
I put it in. Reference numeral 2 in the figure denotes this nonwoven fabric carrier layer. The concentration of the anaerobic fat-and-oil-degrading bacteria at the time of adding the non-woven fabric carrier in the methane fermentation tank was about 5 × 10 ⁸ cells / ml.

In the methane fermentation tank 1, the kitchen waste material having the composition shown in Table 3 is charged from the raw material tank 3 by the pump 4.
While circulating the raw materials in the tank by the circulation pump 5, methane fermentation was performed at 55 ° C. so that the residence time was 6 days. In addition, the desulfurization device 7 is installed in the digestion gas line 6 of the methane fermentation tank 1.
And a gas meter 8 is attached.

[0024]

[Table 3]

In this continuous process, after the carrier 2 is charged,
A sample of the fermentation broth was taken from the methane fermentation tank, the amount of n-hexane extract was measured, and its change over time was examined. The results are shown in Fig. 3. As can be seen in FIG. 3, the amount of n-hexane extract gradually decreased after the carrier 2 was added, and became 10% or less of the garbage raw water after the culture for 10 days. From this, it was found that the oil-and-fat-decomposing bacteria separated by this method can decompose the oil and fat in the kitchen waste with high efficiency simply by introducing it into the methane fermentation tank. Also, when treating wastewater continuously,
It was also found that the fat and oil can be continuously decomposed by adding the anaerobic fat and oil-degrading bacteria that have been accumulated and cultured once.

Example 3 The scum discharged from a food factory having the composition shown in Table 4 was continuously treated in the same manner as in Example 2. That is,
The methane fermentation tank 1 is filled with the non-woven fabric carrier 2 to which the anaerobic fat and oil decomposing bacteria are attached, and the concentration of the anaerobic fat and oil decomposing bacteria is about 5 × 10 ^8.
cells / ml. The methane fermentation was performed at 55 ° C. by supplying the scum so that the residence time was 6 days.

In the same manner as in Example 2, the ability to decompose fats and oils was examined using the change over time in the amount of n-hexane extract as an index. The results are shown in Fig. 4. As shown in FIG. 4, the amount of n-hexane extract decreased after inoculation of the anaerobic fat and oil degrading bacteria, and became 10% or less of the raw water after 5 days of culture. From this, it was found that the oil-and-fat-decomposing bacteria separated by this method can decompose the oil and fat in scum with high efficiency simply by adding it to the methane fermentation tank. It was also found that even when treating wastewater continuously, if the anaerobic fat-degrading bacteria that had been subjected to concentrated culture were added once, the fats and oils could be continuously decomposed.

In these examples, the anaerobic oil-degrading bacteria were separated from the high-temperature methane-fermenting sludge, but not limited to the high-temperature methane-fermenting sludge, the anaerobic oil-degrading bacteria can also be extracted from the medium-temperature or low-temperature methane-fermenting sludge. Can be separated by the same method, and the separated anaerobic oil-degrading bacterium can be used for treating oil-containing wastewater as in the above-mentioned Examples.

[0029]

As described above, when the oil-containing wastewater is treated by using the oil-and-fat-degrading bacteria separated by this method, the following effects are obtained. (1) It is not necessary to provide an oil separation facility such as a grease interceptor. (2) Since oils and fats are decomposed simply by adding oil-containing wastewater to the methane fermentation tank, the existing methane fermentation apparatus can be applied to the present invention, and new capital investment is not required. (3) Even if a new wastewater treatment device is installed, only the methane fermentation device is required, so it is space-saving and economical. (4) Unlike the aerobic treatment, the treatment of the present invention is an anaerobic treatment, so that aeration power or the like is not necessary and no running sludge is generated, so the running cost is low. (5) Since the anaerobic fat-and-oil-degrading bacteria once added grow in the methane fermentation tank, no special maintenance is required.

[Brief description of drawings]

FIG. 1 is a graph showing the oil and fat decomposing ability of anaerobic oil and fat decomposing bacteria collected from a high temperature methane fermentation tank of kitchen waste.

FIG. 2 is a schematic cross-sectional device layout diagram of an apparatus used for continuously decomposing oils and fats using anaerobic oil and fat decomposing bacteria.

FIG. 3 is a diagram showing a change with time of an oil and fat removal rate when oil-containing wastewater is continuously treated by the apparatus of FIG.

FIG. 4 is a diagram showing a change over time in the oil and fat removal rate when the scum discharged from a food factory is continuously treated by the apparatus of FIG.

[Explanation of symbols]

 1 methane fermentation tank 2 porous granular non-woven fabric carrier packed bed 3 raw water tank 4 pump 5 circulation pump 6 methane decomposition tank 7 desulfurization device 8 gas meter

[Table 4]

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kosaku Osato 2-19-1 Tobita-yari, Chofu-shi, Tokyo Kashima Construction Co., Ltd. Technical Research Institute (72) Inventor Mizue Yoshida 2-1-1-1, Tobita, Chofu-shi, Tokyo Kashima Construction Co., Ltd. Technical Research Institute (72) Inventor Tamano Hatano 2-1-1, Tobita, Chofu-shi, Tokyo Kashima Construction Co., Ltd. Technical Research Institute

Claims (2)

[Claims] 1. Methane into which digested sludge collected from a methane fermentation tank is treated in an oil-containing medium under anaerobic conditions to separate and cultivate anaerobic fat-and-oil-degrading bacteria, and oil-containing wastewater is added to the cultured anaerobic fat-and-oil-degrading bacteria. A method for decomposing fats and oils containing oil-containing wastewater, the method comprising proliferating in a fermenter. 2. The method of decomposing oil-containing wastewater according to claim 1, wherein a porous granular granular non-woven fabric carrier is suspended on the liquid surface in the methane fermentation tank into which the oil-containing wastewater is charged.