JP2001038347A - Treatment of wastewater of oil station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove the contaminants of the wastewater discharged from an oil station by processing the water part separated from oil with an adsorbent. SOLUTION: When the wastewater discharged from the oil station or the like and containing gasoline or the like is treated, the wastewater is first introduced into a treatment tank 1 of the uppermost stream. Activated carbon is put in the tank 1 and an air injecting pipe 10a is inserted at the bottom. When air is injected into the wastewater in the tank 1 through the pipe 10a, the wastewater is agitated and the activated carbon becomes a fluidized state. As a result, the contaminants in the wastewater are efficiently brought into contact with the activated carbon and adsorbed on it, and the wastewater is furthermore purified by aeration treatment. The wastewater thus treated with the activated carbon in the tank 1 is introduced into a treatment tank 2 for purification with fluidized activated carbon while being agitated by the air injected through an air injecting pipe 10b. The wastewater discharged from the tank 2 is subjected to a similar treatment in a treatment tank 3 as in the tank 2. The purified wastewater is then discharged to the outside.

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 gas discharged from a gas station, and more particularly to a method for efficiently removing and purifying pollutants contained in water discharged from a gas station. The present invention relates to a method for treating gas discharged from a gas station.

[0002]

2. Description of the Related Art In a gas station, dangerous substances such as gasoline, kerosene, and light oil are handled, and safety measures are extremely important. In particular, great care has been taken in measures to prevent the leakage of these dangerous substances.For leakage from underground tanks, leakage during unloading, and leakage during refueling, leakage detection, diffusion prevention,
Strict leakage prevention measures have been taken through recovery measures.

However, it is actually unavoidable to eliminate these leaks. Therefore, gasoline and the like that have flowed to the road surface due to leakage during unloading from the lorry or during refueling work are first stopped from diffusing, and are guided to a drain ditch provided around the gas station facility. The drainage groove also serves as a flow path for water and rainwater at the time of washing, and the bottom of the drainage groove is provided with a gradient so that drainage does not stay.

A sump for depositing sand and the like is provided at the end of the drainage ditch, and is subsequently connected to a storage tank and an oil / water separator via a switching valve. Normally, the drainage of the wastewater is closed by a switching valve to the storage tank, and the wastewater is directly guided to the oil-water separator.If a large amount of pollutants suddenly flows into the wastewater, the oil-water separator Close the flow path to
The wastewater is once collected in a storage tank and specially treated separately.

[0005] In the oil-water separation device, oil is recovered and water is discharged. However, some gasoline contains methyl-t-butyl ether and other contaminants as a base material, and methyl-t-butyl ether partially dissolved in water is supplied to an oil-water separator. Can not be removed and is discharged while being dissolved in water.

[0006] In particular, methyl-t-butyl ether is concerned as a substance which has an adverse effect on the human body, and its collection and removal is an urgent task. However, there is no effective solution yet. It is.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems, and contaminants contained in the water portion obtained by separating oil and water from the gas discharged from a gas station, especially methyl-t-butyl ether.
It is an object of the present invention to provide a method for treating gasoline effluent that can effectively remove tels.

[0008]

Means for Solving the Problems In order to achieve the above object, the present inventor paid attention to a process after oil / water separation during a process of circulating wastewater from a gas station, and as a result of intensive studies, as a result, By treating the water part obtained by separation with an adsorbent, it has been found that the above object can be achieved,
The present invention has been completed based on this finding.

That is, the present invention provides a method of treating gas discharged from a gas station, wherein the water portion obtained by separating oil and water from the gas discharged from the gas station is treated with an adsorbent.

[0010]

Embodiments of the present invention will be described below. Gasoline, etc., which has flown to the road surface due to leakage during unloading from the lorry or during refueling work, first stops diffusion, and is guided to the drainage ditch provided around the gas station facilities together with the water that has washed the road surface. .

A sump for depositing sand and the like is provided at the end of the drainage ditch, and is subsequently connected to a storage tank and an oil / water separator through a switching valve. The relationship and function of the switching valve, the storage tank, and the oil-water separator are as described above. The storage tank is made of concrete or steel plate, and is provided with an opening / closing lid for checking drainage and a vent pipe for releasing pressure to the atmosphere.

Drainage in which oil such as gasoline and water such as washing water are mixed is separated into oil and water by an oil-water separator, and the oil is recovered. This oil-water separation device separates the two using the weight difference between oil and water,
Usually, it is made of concrete and is composed of a plurality of chambers, and is a step of repeating oil-water separation.

The discharged water portion separated from the oil and water is discharged after being discharged. The present invention is a method for treating gas discharged from a gas station, wherein a water portion obtained by the oil-water separation is treated with an adsorbent. There is no particular limitation on the adsorbent used in the present invention, and activated carbon, silica gel, activated clay, molecular sieve, activated alumina, zeolite,
A normal adsorbent such as a porous resin can be employed, and among them, activated carbon is preferable.

There is no particular limitation on the form of the adsorbent.
It may be granular or massive. In the present invention, as a mode of bringing the water portion obtained by oil-water separation into contact with the adsorbent, a method of dispersing the adsorbent in the water portion, and a method of storing the adsorbent in a water-permeable bag and storing And the like. When the method of dispersing the adsorbent in the water part is adopted, it is preferable to use a powdery adsorbent in order to further improve the contact with the contaminants contained in the water part. In the case of adopting a method of storing in a water-based bag and keeping it in a water portion, it is preferable to use a granular or massive adsorbent.

As the water-permeable bag, a cloth bag or a net-like cloth or resin bag can be used. There are no particular restrictions on the properties of the adsorbent, for example,
When activated carbon is used, the porosity is 50 to 80%, the apparent density is 0.3 to 0.6 g / cm ² , and the average pore diameter is 1
It is preferable to employ one having a diameter of 0 to 15 °, a surface area of 800 to 1500 m ² , and a pore volume of 0.8 to 2.0 cm ² .

Further, the activated carbon may be any of coconut shell charcoal, charcoal, petroleum pitch charcoal and the like. The present invention treats a water portion obtained by oil-water separation with such an adsorbent, and specifically, may be carried out by bringing the water portion into contact with the adsorbent.

As the contact method, as described above, in addition to the method of dispersing the adsorbent in the water part and the method of storing the adsorbent in a water-permeable bag and keeping it in the water part, the adsorbent is adsorbed on the fixed bed. It is also possible to employ a method in which the agent is filled and passed through a water portion, a method in which both are brought into contact with each other by a moving bed, and the like. Among these methods, the method of dispersing the adsorbent in the water part and the method of storing the adsorbent in the water-permeable bag and keeping it in the water part are simple and easy to adopt, and are preferable methods.

In particular, the latter method can be said to be a more preferable method since it is not necessary to separate the adsorbent by filtration, and it is sufficient to simply lift the bag and replace it with a new adsorbent.
When the adsorbent is dispersed in the water part, or the adsorbent is stored in a water-permeable bag and placed in the water part to contact the water part with the adsorbent, even if it is a single-stage treatment, even if it is a single-stage treatment, The treatment may be carried out by using a tank.

In order to improve the contact efficiency, it is also desirable to inject air into the wastewater stream or the tank to enhance the dispersibility of the adsorbent and activate the flow state of the wastewater. FIG. 1 shows an embodiment in which an adsorbent is dispersed in a water portion and the number of treatment steps is multi-stage.

First, waste water is introduced into the uppermost processing tank 1. Activated carbon is contained in the processing tank 1, and an air press-fitting pipe 10 a is inserted in a lower portion of the processing tank 1. Air is sent from the air press-fitting pipe 10a into the wastewater of the treatment tank 1, and bubbles are generated by the air and rise, and the wastewater is stirred, so that the activated carbon is in a fluidized state. As a result, the pollutants in the wastewater are efficiently contacted with and adsorbed by the activated carbon, and the pollutants are also subjected to aeration. There is no limitation on the amount of air to be injected, and any amount may be used as long as the activated carbon exhibits a sufficiently fluid state in the treatment tank.

Activated carbon used in the uppermost processing tank 1 is extracted from the lower part of the processing tank 1 by an activated carbon transfer means 7a such as a pump or an ejector and guided to a regeneration tower (not shown) for regeneration treatment. The wastewater treated by the activated carbon in the treatment tank 1 is led to a treatment tank 2 connected to the treatment tank 1 with a step. In order to guide the waste water from the processing tank 1 to the processing tank 2, as shown in FIG.
A method is preferred in which a flow-down hole 9 is formed in the upper part of the container, and drainage water flows down from the hole. In addition, a method of overflowing from the partition wall 8 of the processing tank 1 or a method of guiding the flow through a pipe communicating with the processing tanks 1 and 2 is also possible.

When guiding from the partition wall 8 as shown in FIG. 1 by the downflow holes 9, it is preferable to form a plurality of holes so that the step between the processing tanks 1 and 2 can be adjusted. In addition, in order to prevent the outflow of the activated carbon at the time of the drainage, the downflow hole is reduced, a wire mesh is applied to the downflow hole,
Countermeasures such as providing a baffle plate are effective. The wastewater introduced into the processing tank 2 is purified by the flowing activated carbon while being stirred by the air from the air injection pipe 10b as in the processing tank 1. The waste water after the treatment flows down the downstream treatment tank 3 provided with a step, and the same treatment is repeated here.

On the other hand, the activated carbon in the processing tank 2 is extracted from the lower part of the processing tank 2 by an activated carbon transferring means 7b such as a pump or an ejector, and is introduced into the upstream processing tank 1. In the present invention, the processing may be completed in such a two-stage process, or may be a three-stage process as shown in FIG. In the processing tank 3, the processing tanks 1, 2
Is performed.

The activated carbon used here is introduced into the treatment tank 2 by activated carbon transfer means 7c such as a pump or an ejector. When the processing tank 3 is the most downstream processing tank, that is, the processing tank in the final stage, the activated carbon used in the processing tank 3 is the activated carbon regenerated in the regeneration tower and / or new activated carbon. Supplied. In such a treatment step, the capacity of the treatment tank may be appropriately selected depending on the amount of treatment wastewater, the number of treatment tanks connected in series, and the like. Usually, the residence time of wastewater per treatment tank is 10 to 30 minutes. It is preferable to adjust so that

According to the present invention, as described above, the wastewater from a gas station is first separated into oil and water, and then the obtained water part is treated with an adsorbent, preferably activated carbon, to thereby obtain contaminants contained in the water part. In particular, a method for treating gas station effluent that can effectively remove methyl-t-butyl ether is provided.

[0026]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. Example 1 An oil-water separation tank using an API type oil-water separation tank was used to discharge oil from a gas station containing 3 liters / min of methyl tert-butyl ether and 0.1% by weight of oil, which was determined by analysis of a collected sample. Part and the water part.

[0027] This water flow is retained in a 30 L square,
Powdery coconut shell activated carbon (porosity 60%, density 0.
4 g / cm ² , average pore size 12 mm, surface area 1000
m ² , pore volume 1 cm ² )
Minutes. Analysis of the collected sample confirmed that the content of methyl-t-butyl ether in the water part after the treatment was 10 ppb.

Example 2 The flow of the water part obtained in the same manner as in Example 1 was kept still, and a cloth bag containing 2000 g of activated carbon same as that in Example 1 was placed in the container and treated for 30 minutes. The content of methyl-t-butyl ether in the water after the treatment was 10 ppb.

Example 3 Example 3 was carried out in the same manner as in Example 1 except that activated carbon was dispersed and air was injected at a rate of 5 L / min through an air injection pipe. Methyl- in water after treatment
t-Butyl ether was 8 ppb.

[0030]

According to the present invention, a gas discharged from a gas station can effectively remove pollutants, particularly methyl-t-butyl ether, contained in a water portion obtained by separating oil and water from the gas discharged from the gas station. And greatly contributes to environmental protection in the field of production and distribution of petroleum products.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention.

[Explanation of symbols]

 1 and 2: processing tanks 7a, 7b, 7c: pump or ejector 8: partition wall 9: downhole 10, 10a, 0b, 10c: air press-fit pipe

Claims (7)

[Claims] 1. A method for treating gas discharged from a gas station, wherein a water portion obtained by separating oil discharged from the gas station is treated with an adsorbent. 2. The method according to claim 1, wherein the water portion obtained by the oil-water separation is methyl-
The method for treating gas discharged from a gas station according to claim 1, wherein the gas contains t-butyl ether. 3. The method according to claim 1, wherein the adsorbent is activated carbon.
The method for treating gasoline effluent described in 4. 4. The method according to claim 1, wherein the adsorbent is dispersed in a water portion obtained by separating oil and water. 5. The treatment of drainage at a gas station according to claim 1, wherein the adsorbent is contained in a water-permeable bag and is installed in a water portion obtained by separating oil and water. Method. 6. The method according to claim 1, wherein the step of treating with the adsorbent is a multi-step process. 7. A method for treating gas discharged from a gas station according to claim 1, wherein the step of treating with an adsorbent disperses the adsorbent in a water portion by injecting air. .