JP2005288257A - Method and apparatus for treating sewage containing oil and fat - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To dispense with a periodical oil and fat removal operation by efficiently decomposing oil and fat intercepted in an oil interceptor with a simple apparatus configuration. <P>SOLUTION: Aeration piping 7 disposed in a first chamber 3, a second chamber 4, and a third chamber 5 of the interceptor 1 is connected to an ozone generator 10 to aerate each chamber with ozone-containing air. The molecular weight of the oil and fat is decreased by the ozone to produce hydrophilic groups, such as -COOH. In case of Na ion-containing sewage, such as kitchen wastewater, as H of a carboxyl group of the oil and fat is substituted by Na to saponify the oil and fat, the oil and fat can be efficiently decomposed and discharged, which dispenses with the periodical oil and fat removal operation. Soap is harmless even after discharge. The deodorizing action and sterilization action of ozone can prevent an offensive odor, propagation of various germs, and the like. As it is sufficient that only the ozone generator 10 and the aeration piping 7 are added to the existing interceptor 1, the apparatus configuration is not complicated, and its control is simple. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention belongs to the technical field of sewage treatment in an oil interceptor.

  For example, wastewater from kitchens for business use such as hotels, inns, restaurants, etc. contains a large amount of oils and fats, and it is not desirable to discharge them as they are, so it is mandatory to install a trap called a grease trap. . The waste water from which the fats and oils have been removed by the interceptor is discharged to the public sewer, and the collected fats and oils are regularly removed from the interceptor by, for example, vacuum and processed.

  However, since the cleaning of the interceptor is an extremely dirty and troublesome operation, the removal is not performed at an appropriate cycle, and the collected oil and fat tends to stay in the interceptor for a long period of time. The accumulated oils and fats not only become unsanitary because they cause bad odors and breed germs, but they are discharged together with the waste water and may cause clogging of the drain pipe and pollution of the river.

It is difficult to process floating oils and fats that stay in the interceptor for a long time and become semi-solid. Various techniques are proposed, including the technique disclosed in Japanese Patent Laid-Open No. 10-296294 (Patent Document 1). However, there was still room for improvement.
JP-A-10-296294

  The technique of Patent Document 1 is a means and process for aeration that can change the amount of air to be aerated when oils and fats are assimilated and decomposed by microorganisms put into the interceptor and decomposed. Either one of the means for adding water at a substantially constant temperature to the wastewater to be treated or the means for adding the cationic surfactant to the wastewater to be treated is provided. The device configuration is complicated and the control is not simple.

  An object of the present invention is to efficiently decompose oils and fats collected by an oil and fat interceptor while eliminating the need for periodic oil and fat removal operations, although the apparatus configuration is simple.

The method for treating oil-containing fat wastewater according to claim 1 is characterized in that ozone is supplied into the wastewater of the oil interceptor.
In some cases, ozone is used mainly for deodorization in sewage treatment or the like, but the present invention is completely different from the conventional use of ozone, and is used to lower the molecular weight of oil in the interceptor.

Generally, fats and oils are a mixture of many triglycerides (neutral fats) in which one glycerin and three fatty acids are ester-bonded.
In the case of a catcher for kitchen drainage, the inflowing fats and oils include vegetable oils such as rapeseed oil and olive oil, and animal fats such as pork fat, beef tallow, fish fat and butter. In reality, these are complicated and mixed, but most of the edible fats and oils contained in the sewage and flowing into the interceptor can be considered oleic acid. Thus, the action of ozone in the present invention will be described using oleic acid as a representative example.

  Oleic acid has the structure shown below and is an unsaturated fatty acid having a double bond.

  When ozone is reacted with this, a structural intermediate called an ozonide (ozone compound) is formed at the double bond portion.

  This ozonide undergoes secondary decomposition and changes to hydrophilic groups such as —OH, —COOH, and —CHO. That is, the double bond is cleaved to form a hydrophilic group. As a result, the fats and oils are reduced in molecular weight and become hydrophilic due to the hydrophilic group, so that the sewage is in a smooth state.

Moreover, the action of ozone is not limited to this.
As exemplified in oleic acid, fatty acids have a carboxyl group, and a carboxyl group is also generated when the molecular weight is lowered as described above. These are represented by the following general formula 3.

  Kitchen drainage and the like contain a large amount of sodium ions mainly derived from salt. When ozone acts on this carboxyl group, it relaxes the bond of OH of the same group and promotes substitution of the H with Na ions in the sewage. As a result, as shown in Chemical Formula 3, the fatty acid is quickly denatured into fatty acid sodium, that is, soap. At this time, H substituted with Na remains in the water as OH groups, and a part of the H is combined with Na ions to form sodium hydroxide to help the soap.

Needless to say, because the soap is familiar with the water and discharged together with the sewage, the oil in the sewage is prevented from stagnating and accumulating in the interceptor.
Not only that, it works extremely effectively in the lump processing of floating oils and fats that have already stayed in the interceptor for a long time and have become semi-solid. That is, since the lower part of the levitated oil and fat is in contact with the sewage, the above-mentioned soaping is performed on this surface part, and the soap is dissolved in the sewage. This soap acts as a surfactant on the floating accumulated fat and oil and dissolves it in the sewage. The fats and oils that have dissolved in the sewage are soaped, and further the subsequent fats and oils are promoted. That is, the levitated fats and oils are soaped one after another, and the levitated fats and oils are lumped as self-disintegrating. Therefore, even if there is floating accumulated fat in the interceptor, it is efficiently dissolved and discharged as soap.

  According to the method for treating oil-containing fat / sewage according to claim 1, by simply supplying ozone into the oil / water catcher's waste water, the unsaturated bond of the oil / fat is cleaved to reduce the molecular weight, and —OH, —COOH, — Since a hydrophilic group such as CHO is generated, oil and fat are prevented from staying in the interceptor. Therefore, the obstructed oil and fat is retained in the interceptor for a long period of time, causing bad odors and breeding germs. It is also possible to prevent flotation deposits and fats from being discharged together with sewage and causing drainage clogging and river pollution. Since the fats and oils do not stay in the interceptor for a long time, it is not necessary to periodically remove the fats and oils.

  In addition, in the case of sewage containing a relatively large amount of Na ions, such as kitchen wastewater, the carboxyl group produced by the cleavage of the unsaturated bond and the H of the carboxyl group of the fat is replaced with Na to make soap. The oil and fat blocked by the vessel can be efficiently decomposed and discharged. This soaping action efficiently dissolves and discharges the levitated fats and oils, eliminating the need for periodic removal of the levitated fats and oils.

Moreover, since ozone has a deodorizing action and a bactericidal action as is well known, it can also prevent bad odors and propagation of germs.
In short, it is possible to prevent the fats and oils from staying in the interceptor for a long period of time, and to remove and discharge the agglomerated fats and oils well, so that various inconveniences caused by the fats and oils can be prevented very well.

  In particular, the interceptor for kitchen drainage is mostly installed under the floor of the kitchen or in the ground near the kitchen, but the above effect can be obtained in such an interceptor. Can improve the sanitary environment.

  As an apparatus configuration, a structure for discharging ozone into the sewage, that is, a discharge means for discharging gas into the sewage in the oil interceptor according to claim 4, and air containing ozone is supplied to the discharge means. It is only necessary to provide ozone supply means. The ozone supply means can be constituted by an ozone generator and a blower, and the discharge means can be only a pipe and a diffuser (or only a small hole is provided in the pipe), and the apparatus configuration is not complicated. Also, since the operating conditions of the ozone generator and blower do not change frequently once set, the actual operation only needs to be turned on and off (actually, once turned on, it will remain for a long time. The control is also simple.

  The ozone supplied to the sewage does not need to be pure, but rather low-concentration ozone mixed with air is preferable because it is easy to handle and safe. That is, as described in claim 2, in the method for treating oil-containing fat and wastewater according to claim 1, it is desirable to employ a configuration in which the ozone is supplied by aeration with air containing ozone.

  If the ozone concentration at that time is less than 5 ppm, the expected effect may be insufficient. On the other hand, when the ozone concentration is about 50 ppm, the effect of ozone hardly changes even if the concentration is increased further. Therefore, as described in claim 3, in the method for treating oil-containing fat / sewage according to claim 2, the ozone concentration of the aerated air is preferably 5 to 50 ppm. Particularly preferred is the range of 15 ± 5 ppm.

  In order to carry out the method for treating oil-containing fat / sewage according to claim 2 or 3, the oil-containing fat / sewage treatment device according to claim 4 is suitable. The oil-containing fat / sewage treatment apparatus according to claim 4 includes an oil / foul interceptor, discharge means for discharging gas into the waste water in the fat / fat catcher, and ozone supply means for supplying air containing ozone to the discharge means. Therefore, as described above, the apparatus configuration is not complicated and the control is simple.

Next, the best mode for carrying out the present invention will be described by way of examples of the present invention. It should be noted that the specific numerical values shown below are examples, and the present invention is not limited to these examples.
[Example]
As shown in FIG. 1, the interceptor 1 is divided into a first chamber 3, a second chamber 4, and a third chamber 5 by a partition plate 2. However, a gap serving as a flow path of sewage is provided between the partition plate 2 and the bottom, and the chambers 3, 4, and 5 communicate with each other. The first chamber 3 is provided with an inflow pipe for allowing sewage to flow in and a strainer for filtering solid matter, and the third chamber 5 is provided with an outflow pipe for allowing upper sewage to flow out. However, these illustrations are omitted. The interceptor 1 itself is not different from a known one. In this embodiment, a 200-liter grease trap (interceptor) is used.

  On the bottom of the interceptor 1, one aeration pipe 7 is installed in the first chamber 3, two in the second chamber 4, and one in the third chamber 5. The tip of each aeration pipe 7 is closed by a cap, and diffusers (not shown) are attached to two horizontal portions along the bottom of the interceptor 1. The aeration pipe 7 is connected to a header 9 via a valve 8, and the header 9 is connected to an ozone generator 10.

  The ozone generator 10 includes a blower 11, a filter 12, and an ozone generator 13. In addition, although there are two ozone generation units 13, normally only one of them is operated (the other is a spare).

  The blower 11 sucks and discharges air, but a part of the discharged air is branched and sent from the filter 12 to the ozone generator 13. Oxygen (a part thereof) in the air that has flowed into the ozone generator 13 is changed to ozone by corona discharge in the ozone generator 13. The air containing ozone again merges with the air from the blower 11 and is sent to the header 9 and discharged into the interceptor 1 from the aeration pipe 7 (diffuser).

The specification of the ozone generator 10 is that the ozone generation amount is 75 mg / h and the discharge amount is 40 l / m, so the ozone concentration of the discharged air is 15 ppm.
Now, when the sewage is poured into the interceptor 1 from the inflow pipe, the sewage whose solids are filtered by the strainer flows from the first chamber 3 into the second chamber 4. In the second chamber 4, the fats and oils in the sewage float up and gather near the water surface, and the lower layer sewage from which the fats and oils are separated flows to the third chamber 5. In the third chamber 5, fine solids and the like are precipitated and the supernatant is discharged from the outflow pipe. The aspect of this sewage treatment is the same as that of a known grease trap.

In the case of the present embodiment, air containing ozone is discharged from the aeration pipe 7 (diffuser) to the interceptor 1 in the course of this sewage treatment.
As mentioned above, this ozone cleaves unsaturated bonds of fats and oils contained in sewage and lowers the molecular weight to generate hydrophilic groups such as —OH, —COOH, and —CHO. To stay in the water. As a result, the obstructed oil and fat can be prevented from staying in the obstructor 1 for a long period of time, causing bad odor and breeding of various germs. It also prevents contamination. Since the fats and oils do not stay in the interceptor 1 for a long period of time, it is not necessary to periodically remove the fats and oils.

  Moreover, in the case of sewage containing a relatively large amount of Na ions, such as kitchen wastewater, the carboxyl group produced by the cleavage of the unsaturated bond and the H of the carboxyl group of the oil and fat are replaced with Na to make soap. The oil and fat collected in 1 can be efficiently decomposed and discharged. This soaping action dissolves and discharges the levitated fats and oils efficiently, eliminating the need for periodic oil removal work. It is well known that soap has very little secondary damage, such as deterioration of downstream water quality or problems in sewage treatment.

Moreover, since ozone has a deodorizing action and a bactericidal action as is well known, it can also prevent bad odors and propagation of germs.
[Experimental example]
A sewage treatment experiment was conducted on the existing interceptor 1 in which the ozone generator 10 and the aeration pipe 7 were added to form the apparatus configuration of the example. Since it is existing, as shown in FIG. 2 (before installation), a large amount of the floating accumulated oil and fat was accumulated in the interceptor 1 and solidified into a firm state.

  When the ozone-containing air from the ozone generator 10 was supplied to the interceptor 1 and aerated, the levitation accumulated fats and oils softened when 2 hours passed (2 hours after installation in FIG. 2) and 5 hours passed (see FIG. 2). 5 hours after the installation of 3) all became foamy, and when 12 hours passed (12 hours after the installation of FIG. 3), all the floating oils and fats were dissolved and the sewage became almost transparent. Note that the dumplings floating in the second chamber and the third chamber are not fats and oils but are aggregates mainly composed of gluten. This agglomerate may be picked up and processed, and since the amount of generation is small, there is no problem.

  And when 24 hours passed, the dramatic effect as shown below was confirmed. The sample is discharged water from the outflow pipe.

[Table 1]
Water hydrogen ion concentration at the start of the experiment (liquid temperature ° C) 4.6 (21.0) JIS K0102-12.1
Biochemical oxygen demand 4500 mg / l JIS K0102-21. JIS K0102-32.3
Chemical oxygen demand 1000 mg / l JIS K0102-17.
Amount of suspended solids 11000 mg / l Appendix 8 of the 1971 Environment Agency Notification No. 59
n-Hexane Extracted Substance Content 430 mg / l Showa 49 Environment Agency Notification No. 64 Appendix 4
Number of coliforms 1800 / cm3 Showa 37 Ministry of Health and Welfare Ordinance No. 1 Annex 1

[Table 2]
Water hydrogen ion concentration at 24 hours (liquid temperature ° C) 5.3 (18.4) JIS K0102-12.1
Biochemical oxygen demand 720 mg / l JIS K0102-21. JIS K0102-32.3
Chemical oxygen demand 380 mg / l JIS K0102-17.
Amount of suspended solids 460 mg / l Appendix 8 of the 1971 Environment Agency Notification No. 59
n-Hexane extractable substance content 10 mg / l Table 4 of the Environment Agency Notification No. 64 in 1974
Number of coliform bacteria: 480 / cm3
From the above results, since the content of the n-hexane extractable substance has been drastically reduced from 430 mg / l to 10 mg / l, the reaction between the flotation deposited fat and ozone is not a simple emulsion (emulsification) reaction, This confirms the more aggressive change from fats and oils to other substances, that is, the rapid progress of the aforementioned low molecular weight and soaping processes. And it can be inferred that the water quality barometer of BOD and COD has improved significantly due to the synergistic effect of low molecular weight and soap.

Explanatory drawing of the oil-containing fat wastewater treatment apparatus of an Example. Explanatory drawing of the wastewater treatment experiment by ozone aeration. Explanatory drawing of the wastewater treatment experiment by ozone aeration.

Explanation of symbols

1 ... Interceptor (Oil and fat interceptor),
2 ... partition plate,
3 ... 1st room,
4 ... Second room,
5 ... Room 3
7: Aeration piping (discharge means),
10 ... Ozone generator (ozone supply means),
11 ... Blower (Ozone supply means),
13: Ozone generator (ozone supply means).

Claims (4)

  A method for treating oil-containing fat wastewater, comprising supplying ozone into the wastewater of the oil interceptor. In the processing method of the oil-containing fat wastewater of Claim 1,
The supply of ozone is performed by aeration with air containing ozone. In the processing method of the oil-containing fat wastewater of Claim 2,
The method for treating oil-containing fat wastewater, wherein the ozone concentration of the aerated air is 5 to 50 ppm. An oil interceptor,
Discharge means for discharging gas into the sewage in the oil interceptor;
An oil-containing fat / sewage treatment apparatus comprising ozone supply means for supplying air containing ozone to the discharge means.