JPH08182996A - Treatment of oil containing waste water - Google Patents

Abstract

PURPOSE: To simply and efficiently treat to decompose an oil containing waste water in a biological reactor by floating a porous granular upwoven fabric carrier on the liquid surface in a methane fermentation tank or an activated sludge tank at the time of decomposing oils and fats in the waste water by feeding the oil containing waste water to the vessel. CONSTITUTION: The unwoven fabric carrier 8 on which an anaerobic oils and fats decomposing bacterium or an aerobic oils and fats decomposing bacterium is immobilized is fed to the activated sludge tank 17 so as to reach a quantity capable of covering the surface of a fermentation liquid by two layers. The waste water is introduced into the activated sludge tank 17 from a raw water tank 18 by using a pump 19 and is treated at 30 deg.C by controlling the residence time of the waste water to about 10hr while feeding air from an aeration blower 2 to an air diffusing pipe 20 in the tank. The treated water is discharged through a discharge line 22. The unwoven fabric carrier 8 is formed by sticking a porous sheet composed of a glass fiber or a plastic fiber to the outside of a particle body of a lightweight plastic (preferably a granular body having 5-6mm diameter).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating 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, and such fungi have already been searched and separated. For example, lipase-producing bacteria such as Bacillus sp.
seudomonas sp. No. 6 is known.

[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.

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, when the oil-containing wastewater is put into a methane fermentation tank or an activated sludge tank to decompose oils and fats in the wastewater, the liquid level in the tank is porous. The present invention provides a method for treating oil-containing wastewater, which comprises suspending a granular non-woven fabric carrier. Here, as the non-woven fabric carrier, a porous sheet made of glass fiber or plastics fiber is used as a lightweight plastics granular material (preferably a granular material having a diameter of 5 to 60 mm), and the liquid level in the tank is one step. Float a sufficient quantity to cover the above.

[0010]

[Function] When the oil-containing wastewater is put into the methane fermentation tank in which the anaerobic oil-degrading bacteria inhabit or the activated sludge tank in which the aerobic oil-degrading bacteria inhabit, these bacteria grow while decomposing the oil and fat. However, if the oil-containing wastewater is simply put into such a biological treatment tank, the oil and fat in the oil-containing wastewater has the property of floating near the liquid surface of the treatment tank. The chances of contact with the minute are reduced and it cannot be decomposed efficiently.

However, according to the present invention,
When a granular non-woven fabric carrier is suspended on the liquid surface, fat-decomposing bacteria are fixed on this non-woven fabric carrier, and active growth activity occurs there, so the oil and fat components floating near the liquid surface are well decomposed, and overall efficiency is improved. Good processing is possible.

The non-woven fabric carrier used in the present invention comprises a porous sheet composed of glass fibers or plastics fibers, and a granular body of lightweight plastics (preferably having a diameter of 5 to 6).
It is applied to the outside of a 0 mm granular material) and is suspended in a sufficient number 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. Then, by using lightweight granular plastics such as hollow plastics and plastic foams as a core material for holding the porous sheet, this nonwoven fabric carrier can be freely flown and floated on the liquid surface in the tank. Both of the plastics as the core material also function as a microorganism carrier.

FIG. 1 shows an example of the shape of a porous granular nonwoven fabric carrier used in the present invention, which has a structure in which a nonwoven fabric 3 is attached around a hollow granular plastics 2 having a cavity 1 inside. As the shape of the granular plastics 2 as the core material, various shapes such as a sphere, a square, an ellipse, a rhombus, and a ring can be used as shown in the figure. Good. Then, the non-woven fabric 3 is applied to the periphery of these core materials to form non-woven fabric carrier particles having a diameter of about 5 to 60 mm.

FIG. 2 shows the same non-woven carrier particles as in FIG. 1 except that the foamed plastics 4 is used as the core material. The non-woven fabric carrier particles thus constructed have a larger surface area of the non-woven fabric as the particle size is reduced, and thus the amount of the microbial carrier can be increased.
If the diameter is smaller, the manufacturing cost is higher, and if the diameter is larger than 60 mm, the surface area of the nonwoven fabric cannot be taken sufficiently.
The preferred particle size is 10 to 50 mm.

To attach the non-woven fabric 3 around the granular plastics 2 and 4 as the core material, as shown in FIG.
A method of wrapping the periphery of the core material 2 (or 4) with a plurality of hemispherical non-woven fabric segments 3 and joining the segments with an adhesive 5 (Fig. 3-a), or wrapping the core material 2 (or 4) If a method of enclosing the core material 2 with a non-woven fabric 3 having a large area and joining the neck portion with the adhesive 5 (FIGS. 3B and 3C) is adopted, even a non-woven fabric made of glass fiber having relatively low flexibility is sufficient. Can be installed. In addition, as the adhesive 5, if a usual polymer type adhesive such as an epoxy type adhesive is used,
This also functions as part of the carrier.

In any case, the non-woven fabric carrier constructed as described above should be sufficiently lightweight so as to be able to float on the liquid surface when loaded into a methane fermentation tank or an activated sludge tank. And by using a non-woven fabric resistant to temperature (eg glass fiber), it can be applied to a wide range of processing temperatures (eg 10 to 60 ° C.).

Generally, fats and oils have the property of floating as oil balls in the biological reaction tank, and therefore it is difficult to uniformly disperse them in the biological treatment tank by ordinary stirring. Microorganisms are damaged, causing problems such as a decrease in activity and an increase in stirring energy. However, according to the present invention, the non-woven fabric carrier floats on the liquid surface together with the oil balls, and the fats and oils fixed there are decomposed. Since the bacteria can directly contact the oils and fats, the oils and fats can be efficiently decomposed and removed with the same degree of stirring as in the past.

[0018]

【Example】

[Test Example] In order to investigate the size of the non-woven fabric carrier capable of decomposing fats and oils with high efficiency, various types of non-woven fabric carriers shown in a to c of FIG. 3 were tested. The plastic material of the core material is a hollow body, and the non-woven fabric 3 is a sheet made of glass fiber. An epoxy resin was used as the adhesive 5.

Since it is possible to think that the oil and fat degradability depends on the amount of microorganisms immobilized on the nonwoven fabric carrier, the ability of the prototype nonwoven fabric carrier to immobilize microorganisms was measured. Immobilization was carried out by immobilizing microorganisms on each carrier by the method described in Example 1 below. An anaerobic oil-degrading bacterium was used as the immobilized microbial cells. The anaerobic fat and oil decomposing bacteria were separated by the method described in Example 1 below. The measurement result is shown in FIG. From this result, it was found that the ability to fix microorganisms was almost constant regardless of the shape of the nonwoven fabric carrier.

When the liquid surface area of the biological treatment tank is constant, the surface area can be increased by decreasing the particle size of the nonwoven fabric carrier. Therefore, Fig. 3-
A fat and oil decomposition experiment was conducted using the nonwoven fabric carrier of a. As an experimental method, a non-woven fabric carrier on which anaerobic fat-and-oil-degrading bacteria were immobilized was put into a medium containing fat and oil, and the removal rate of fat and oil was measured after 10 days. The biological treatment tank used in the experiment has a liquid surface area of 0.785 m.
^Two methane fermentors were used. The results are shown in FIG. 5 organized by the value of (liquid surface area of biological treatment tank) / (cross-sectional area of non-woven fabric carrier). The "cross-sectional area of the non-woven fabric carrier" as used herein refers to the horizontal cross-sectional area of each particle when particles of the same particle size are floated so that the liquid surface is fully covered with the non-woven fabric carrier.

From the results of FIG. 5, it was found that a high removal rate was obtained when the value of (liquid surface area) ÷ (cross-sectional area of the nonwoven fabric carrier) was around 400, and when it was 400 or more, the oil / fat removal rate did not change so much. The smaller the particle size of the nonwoven fabric carrier, the higher the manufacturing cost. Therefore, the optimum size of the non-woven fabric carrier is (liquid surface area) / (cross-sectional area of the non-woven fabric carrier)
Was found to be 10,000 to 400. In this experiment, since the liquid surface area using a methane fermentation tank of 0.785M ^2, the diameter of the nonwoven carrier is a best thing 1 to 5 cm, the cross-sectional area 7.85 × 10 ^-5 ~10 ^-3 m ² It was

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 First, 0.5 ml (milliliter, hereinafter the same) of high temperature methane fermentation sludge after the garbage treatment was sampled and inoculated into 100 ml of the medium shown in Table 1. This medium was used after being sterilized by an autoclave at 120 ° C. for 20 minutes. For culturing, an anaerobic jar fermenter was used and culturing was performed at 55 ° C. for 2 weeks. Since the culture is performed in the same atmosphere as in the methane fermentation tank, CH ₄ : CO ₂ =
The culture was performed while aerating a gas of 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 6.
It was shown to.

[0025]

[Table 1]

[0026]

[Table 2]

From the results shown in FIG. 6, the n-hexane extract was
After inoculation with the anaerobic fat-and-oil degrading bacteria, the amount gradually decreased, and after 2 weeks, it was 10% or less before the inoculation. That is, it is considered that the anaerobic fat-and-oil-degrading bacteria separated by this method were able to remove fats and oils by 90% or more.

[Example 2] The anaerobic fat-and-oil degrading bacteria isolated in Example 1 were inoculated into the same medium as 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, the spherical non-woven fabric carrier having a diameter of 2 cm shown in FIG. 3A was introduced and further cultured for 2 weeks to attach the anaerobic fat-and-oil-degrading bacteria to the carrier. The amount of anaerobic fat-and-oil-degrading bacteria adhering to the carrier after 2 weeks was 2.2 g / cm ² in dry weight.

As shown in FIG. 7, the nonwoven fabric carrier 8 on which the anaerobic fat-and-oil-degrading bacteria have been immobilized is placed in a methane fermentation tank 7 in two stages on the surface of the fermented liquid so that the surface area of the liquid is covered. I put it in. In the methane fermentation tank 7, the kitchen waste material having the composition shown in Table 3 is fed from the raw material tank 9 by the pump 10,
While circulating the raw material in the tank by the circulation pump 11, methane fermentation was performed at 55 ° C. so that the residence time was 6 days. A desulfurizer 13 and a gas meter 14 are attached to the digestion gas line 12 of the methane fermentation tank 7.

[0030]

[Table 3]

In this continuous process, after charging the carrier 8,
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 result is shown in FIG. As can be seen in FIG. 8, the amount of n-hexane extract in the fermentation broth gradually decreased after the carrier was added.
After the day, it decreased to about 10% before the carrier was added. Also, the oil balls floating on the liquid surface of the methane fermentation tank
It disappeared 5 days after the carrier was added.

Example 3 0.5 ml of activated sludge was sampled and inoculated into 100 ml of the medium shown in Table 1 (sterilized by autoclave at 120 ° C. for 20 minutes). An aerobic jar fermenter was used for culturing, and aeration culture was carried out at 30 ° C. for 2 weeks. Two weeks later, 0.5 ml of the culture solution was inoculated into 100 ml of the medium shown in Table 2 and aerobically cultured to test the presence or absence of oil and fat degradability. As for the oil and fat degradability, the change over time in the amount of n-hexane extract was used as an index as in the previous example. The results are shown in Fig. 9.

As shown in FIG. 9, the n-hexane extract gradually decreased after inoculation with the aerobic fat-and-oil degrading bacteria,
After the day, it became 10% or less before the inoculation of the aerobic fat and oil decomposing bacteria. From these results, it is considered that the aerobic fat-and-oil-degrading bacteria separated by this method were able to remove fats and oils by 90% or more.

[Example 4] The aerobic fat-and-oil-degrading bacteria isolated in Example 3 were inoculated into the medium shown in Table 2 above and grown by aeration culture at 30 ° C to give a bacterial concentration of 1 x 10 ⁸ cells / m 2.
When it became 1, a spherical non-woven fabric carrier having a diameter of 2 cm (shown in Fig. 3-a) was introduced and cultured for 1 week to attach aerobic fat-degrading bacteria to the carrier. The amount of aerobic fat-degrading bacteria adhering to the carrier after 1 week was 1.8 g / dry weight.
cm ² .

The non-woven fabric carrier 8 on which the aerobic fat-and-oil-degrading bacteria are immobilized is placed in an activated sludge tank 17 as shown in FIG.
The fermented liquor surface was added in two steps to cover the liquid surface area. In the activated sludge tank 17, the artificial wastewater shown in Table 4 was introduced from the raw water tank 18 by the pump 19 and the air was blown from the explosion blower 21 to the air diffuser 20 in the tank so that the residence time was 10 hours at 30 ° C. Processed in. Reference numeral 22 in the figure denotes a treated water discharge line.

[0036]

[Table 4]

In this continuous process, after the carrier 8 is charged,
A sample of the treated liquid was taken from the activated sludge tank, the amount of n-hexane extract was measured, and its change with time was examined. The results are shown in Fig. 11. As shown in FIG. 11, the amount of the n-hexane extract in the treatment liquid decreased after the carrier was added, and after 2 days, it decreased to about 10% before the carrier was added. The oil balls floating on the liquid surface of the activated sludge tank disappeared within 1 day after the carrier was added.

[0038]

As described above, according to the present invention,
Oil-containing wastewater can now be decomposed easily and efficiently in a biological reaction tank. For this reason, oil-containing wastewater can be treated without providing an oil separation facility such as a grease interceptor, and existing methane fermentation tanks and activated sludge tanks can be used directly as oil decomposition tanks. Also, since it is possible to deal with wastewater containing oil and fat at a high concentration, it can greatly contribute to the troublesome treatment of oil-containing wastewater.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a shape example of a nonwoven fabric carrier using a hollow resin core material.

FIG. 2 is a schematic cross-sectional view showing a shape example of a nonwoven fabric carrier using a foamed resin core material.

FIG. 3 is a schematic cross-sectional view illustrating a method of attaching a nonwoven fabric sheet to a core material.

FIG. 4 is a diagram showing the relationship between the type of non-woven fabric carrier and the amount of attached microorganisms.

FIG. 5 is a diagram showing the relationship between the ratio of the liquid surface area in the biological treatment tank / the cross-sectional area of the nonwoven fabric carrier and the oil and fat removal rate.

FIG. 6 is a graph showing the oil and fat decomposing ability of anaerobic oil and fat decomposing bacteria collected from a garbage methane fermentation tank.

FIG. 7 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. 8 is a diagram showing a change with time of a fat and oil removal rate in the case of continuous treatment with the apparatus of FIG.

FIG. 9 is a graph showing fat and oil degradability of aerobic fat and oil decomposing bacteria collected from an activated sludge tank.

FIG. 10 is a schematic cross-sectional device layout diagram of an apparatus used for continuously decomposing fats and oils using aerobic fat-and-oil degrading bacteria.

FIG. 11 is a diagram showing a change with time of a fat and oil removal rate in the case where continuous processing is performed by the apparatus of FIG.

[Explanation of symbols]

 1 Cavity 2 Core Material of Granular Plastics 3 Nonwoven Fabric 4 Core Material of Foamed Plastics 5 Adhesive 7 Methane Fermenter 8 Nonwoven Carrier 9 Raw Material Tank 11 Circulation Pump 12 Digestion Gas Line 17 Activated Sludge Tank 18 Raw Water Tank 20 Diffuser 21 Explosion Ki blower

Claims (3)

[Claims] 1. When the oil-containing wastewater is put into a methane fermentation tank or an activated sludge tank to decompose oil and fat in the wastewater,
A method for treating oil-containing wastewater, characterized in that a porous, granular nonwoven fabric carrier is suspended on the liquid surface in the tank. 2. The method for treating oil-containing wastewater according to claim 1, wherein the non-woven fabric carrier is obtained by coating a porous sheet composed of glass fibers or plastics fibers on a granular body of lightweight plastics. 3. The oil-containing wastewater according to claim 1 or 2, wherein the non-woven fabric carrier is a granular body having a diameter of 5 to 60 mm, and the granular body is suspended in an amount sufficient to cover the liquid level in the tank in one or more stages. Processing method.