WO2002020123A1

WO2002020123A1 - Method and device for filtrating sewage fluid

Info

Publication number: WO2002020123A1
Application number: PCT/JP2001/007201
Authority: WO
Inventors: Masahide Uchino
Original assignee: Japan Field Co., Ltd.
Priority date: 2000-09-05
Filing date: 2001-08-23
Publication date: 2002-03-14
Also published as: JP3539680B2; TWI233372B; AU2001280114A1; JP2002079012A

Abstract

A method of filtrating sewage fluid capable of not only eliminating the use of a pump and simplifying a mechanism for the filtration of fluid but also completely eliminating the need for considerations to the fluid resistance and heat resistance of the pump, comprising the steps of, by utilizing a negative pressure caused by the decompression, leading sewage fluid (11) into a decompressed leading-in tank (13) decompressed by a decompression mechanism (28) connected thereto, disposing a filtrating means (18) for the sewage fluid (11) in a fluid passage ranging from the inlet side to the outlet side of the sewage fluid (11), and filtrating the sewage fluid (11) by a filtrating means (18), whereby, even if large particles and chips are present in the sewage fluid, the sewage fluid can be transferred, the sewage fluid can be transferred rapidly to the decompressed leading-in tank of the sewage fluid by a decompression means for rapid filtration, and the waste remaining in the decompressed leading-in tank after the filtration can be dried easily.

Description

Specification

FIELD OF THE INVENTION

The present invention relates to a filtration method for removing dirt from a cleaning liquid used for cleaning an object to be cleaned, a plating liquid, a processing liquid used for cutting or rolling, a processing liquid used for a surface treatment step, and other waste liquids. It concerns the device. Background art

Conventionally, in order to perform the above-mentioned filtration of a liquid, as shown in FIG. 3, a filtration device (4) is provided from a waste liquid storage tank (2) containing a waste liquid (1) using a pump (3). The waste liquid (1) is filtered by feeding the waste liquid (1) to the wastewater (1), and the waste liquid (1) is recovered by returning the filtered waste liquid (1) to the waste liquid storage tank (2). It is circulating for filtration.

However, in the conventional method as described above, a pump is used to transfer the sewage, so there are limitations on the pumps that can be used due to the liquid resistance, chemical resistance, heat resistance, etc. of the pump. Often there is a limit on the possible sewage.

Further, when the pump is used in a filtration device, the pump may be damaged or cannot be pumped due to the size and material of the particles contained in the waste liquid. In addition, when a pump is used, the flow rate is determined by the capacity of the pump, so rapid movement of wastewater is restricted, and rapid filtration of wastewater is often difficult. In other words, it is difficult to transfer wastewater rapidly by using a pump.

Also, with conventional filtration equipment, it is difficult to drain and dry the liquid adhering to the waste, and the waste is discarded with a large amount of liquid adhering to the environment. However, it is extremely unfavorable in terms of environmental protection. In addition, in the conventional method of filtering waste liquid using a pump, a strainer is often provided on the injection side of the pump in order to protect the pump from large waste such as cutting chips. In this way, dirt deposited on the bottom of the dirt tank, for example, dirt with a large particle diameter, such as relatively large swarf or metal powder, is introduced into the circulation path of the pump to be filtered and removed. Was difficult because it could damage the pump and clogged the strainer. For this reason, conventionally, small particles in wastewater are removed by a filter in the circulation path of the pump, but the above-mentioned relatively large particle-based waste, metal powder, and cutting chips remain deposited inside the liquid tank. In this state, only small particles were removed by a filter, and it was difficult to completely filter the waste liquid.

Conventionally, to remove the relatively large diameter metal powder and cutting powder, all the liquid in the waste liquid tank is discharged, and then the cleaning is performed manually by hand or the like. Also in this case, since the liquid used for the treatment is attached to the deposited waste such as metal powder and cutting powder having a relatively large particle size, the waste is discharged to the outside together with this liquid, thereby reducing environmental problems. It was very likely to occur. Disclosure of the invention

The present invention is intended to solve the above-described problems. The present invention aims to solve the above-mentioned problems by transferring a sewage to a filtration means without using a pump, and treating the pump with chemical resistance and heat resistance. Make sure that you are not restricted by gender. In addition, the filter operation can be performed promptly regardless of the size and material of the particle diameter contained in the waste liquid. Then, a rapid liquid transfer is performed, and a quick liquid transfer from the waste liquid storage section to the filtration tank enables a quick filtration operation of the waste liquid.

In addition, waste that has accumulated on the lower bottom of the waste storage section will be quickly introduced into the filtration means together with the waste liquid, making it possible to introduce the accumulated waste, which was difficult using a pump. It also makes it easier to dry filth removed from sewage. In order to obtain a filtration device that is easy to carry out, removes waste liquid that has a negative impact on the environment when disposing of waste material, enables disposal of waste material after drying, and allows for environmental consideration. Is what you do.

In order to solve the above-mentioned problems, the present invention utilizes a negative pressure due to the reduced pressure to introduce a waste liquid into a reduced-pressure introduction tank connected to a reduced-pressure mechanism, and the waste liquid is introduced from the introduction side to the discharge side. The method is characterized in that a means for filtering waste liquid is disposed in a flow path leading to the wastewater, and that the waste liquid is filtered by the filtering means.

Further, the apparatus for realizing the above invention is connected to a pressure reducing mechanism, and the pressure is reduced. The vacuum is introduced using the negative pressure resulting from the reduced pressure, and the vacuum introducing tank capable of discharging the waste liquid. And a filtering means disposed in a flow path from the introduction side to the discharge side of the reduced-pressure introduction tank to filter waste liquid.

Further, the depressurization introduction tank may be one in which a pressurized gas can be introduced and the filtered liquid can be discharged by the pressure of the pressurized gas.

Further, the vacuum introduction tank may be one in which the inside of the tank is decompressed and the remaining waste can be dried under reduced pressure.

The present invention is configured as described above. In order to perform filtration of cleaning oil, cutting work, cutting oil used for cutting metal materials, and other contaminants for filtration, first, the pressure is reduced. The pressure in the introduction tank is reduced by the pressure reducing mechanism. If the waste liquid storage unit and the vacuum introduction tank are communicated with each other in the reduced pressure state in the vacuum introduction tank, the waste liquid is rapidly transferred into the vacuum introduction tank by negative pressure. Since this transfer does not use a pump, the wastewater in the wastewater storage section can move rapidly and rapidly according to the reduced pressure state of the vacuum introduction tank.

Further, since the wastewater is transferred to the filtration means without using a pump, there is no restriction on the chemical resistance and heat resistance of the pump to be treated. In addition, the filtration operation can be performed quickly irrespective of the size and material of the particle diameter contained in the waste liquid. In addition, waste that has accumulated on the lower bottom of the waste storage section is quickly introduced into the filtration means together with the waste, and a pump is used. It would be possible to introduce the accumulated waste, which was difficult in the previous work.

The filtration means may be disposed in the flow path from the introduction side to the discharge side of the waste liquid into the vacuum introduction tank, and the vacuum introduction tank may be provided on the inflow side of the waste liquid. It may be provided on the outflow side of the waste liquid from the tank, or may be provided in the vacuum introduction tank. Then, the waste liquid is filtered by the filtering means in the flow path of the waste liquid. The wastewater filtered by the filtration means may be restored to the wastewater storage section, and the wastewater may be filtered while being circulated, or may be stored at another appropriate position. good.

As described above, when the waste liquid is introduced into the vacuum introduction tank and the waste contained in the waste liquid accumulates in the vacuum introduction tank by filtration, the waste is directly removed from the vacuum introduction tank. However, if the waste is removed in an untreated state, the waste will be disposed of with the waste liquid, such as the cleaning solvent, cutting oil, and plating liquid, attached to the waste, and this will affect the environment. High impact is not desirable.

Therefore, by operating the decompression mechanism in a state in which dirt is accumulated in the decompression introduction tank, if the inside of the decompression introduction tank is set to a negative pressure state, the dirt in the decompression introduction tank to which the liquid is attached can be removed. The waste liquid evaporates due to the lowering of the boiling point due to the reduced pressure, and is sucked into the pressure reducing mechanism. By taking this out of the vacuum introduction tank, it is possible to make the waste free of liquid adhesion, to have little effect on the environment, and to make the treatment extremely easy. In addition, the contaminated waste liquid is condensed and reused.

Further, the filtration means is not provided only in the reduced-pressure introduction tank, but may be provided in the flow path from the introduction side to the discharge side of the waste liquid with respect to the reduced-pressure introduction tank. Therefore, the above-mentioned drying of the waste becomes effective when the filtering means is disposed in the pressure-reducing introduction tank or when the waste is introduced into the pressure-reducing tank using the pressure-reducing means.

In addition, by connecting a mechanism to fill the depressurized gas introduction tank with a pressurized gas, when the liquid after filtration is transferred, the pressurized gas is introduced into the decompression gas tank to quickly filter the contaminated liquid. Can be transferred to the destination Become.

In addition, the sewage adhering to the sewage remaining in the vacuum introduction tank can be removed to a considerable extent from the sewage by the pressurized gas and transferred to the target part. After the transfer of the waste liquid by the pressurized gas and the removal of some waste liquid from the waste, the decompression mechanism is operated to reduce the pressure in the vacuum introduction tank, thereby reducing the amount of liquid adhering to the waste. Volatile drying accompanying lower boiling point can be further facilitated.

According to the present invention, as described above, the waste liquid is transferred to the reduced-pressure introducing tank by the depressurizing means without using a pump, and is filtered in the transfer passage. Can do it. In addition, the filtered waste can be easily dried by reducing the pressure in the vacuum introduction tank, and the effect on the environment can be minimized. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a sectional view showing an embodiment of the present invention. FIG. 2 is a sectional view of a different embodiment of the present invention provided with an auxiliary tank. FIG. 3 is a cross-sectional view showing a conventionally known filtration device. BEST MODE FOR CARRYING OUT THE INVENTION-One embodiment of the present invention will be described below with reference to Fig. 1. (10) is a waste liquid storage unit, and a tank for storing waste liquid (11) is provided. It may be a more formed one or a source of sewage. The waste liquid (11) is stored in the waste liquid storage part (10). This waste liquid (11) can be stored in the waste liquid storage part (10) before the filtration operation, or can be restored and stored after the filtration operation is completed. The waste liquid (11) is a cleaning solvent for the object to be cleaned, a cutting oil, or a plating liquid used for plating, and is a liquid used for an appropriate industrial treatment.

In addition, a transfer pipe (12) is connected to the liquid discharge side of this waste liquid storage part (10), and this transfer pipe (12) is fixed to the liquid outlet side of the vacuum introduction tank (13). Connected. A first on-off valve (14) is formed in the transfer pipe (12), and a pressure gauge (15) is provided between the first on-off valve (14) and the depressurization introduction tank (13). Deploy. Also, a second on-off valve (16) is arranged between the first on-off valve (14) and the pressure gauge (15) of the transfer pipe (12), and the second on-off valve (16) is interposed. To the pressure gas inlet (17).

Further, a filtration means (18) such as a filter is formed in the vacuum introduction tank (13), and the filtration of the contaminated liquid (11) is performed by passing the filtration means (18) through the filtration means (18). It is possible. In addition, a lid (20) for sealing the upper end is arranged in the vacuum introduction tank (13) via a packing (21) and the like, and an air release valve (22) is connected. .

Further, a discharge pipe (23) of the waste liquid (11) is fixedly connected to a lower end on the liquid discharge side of the vacuum introduction tank (13) through a filtration means (18), This discharge pipe (23) is fixedly connected to the liquid introduction side of the waste liquid storage part (10) via a third on-off valve (24). A second pressure gauge (25) is arranged between the third on-off valve (24) and the discharge pipe (23). In the discharge pipe (23), a fourth on-off valve (26) is disposed at a position through the third on-off valve (24) with respect to the waste liquid storage part (10). A pressure reducing mechanism (28) such as a vacuum pump and an ejector mechanism is connected to a pressure reducing pipe (27) connected to the on-off valve (26). In this decompression mechanism (28), a strainer (30) is arranged in a decompression pipe (27) between the fourth on-off valve (26) and a large-sized contaminant such as cutting chips flowing in. The introduction to the pressure reducing mechanism (28) is prevented.

In order to filter the waste liquid (11) stored in the waste liquid storage part (10) using the vacuum introduction tank (13) in the above-structured, the first on-off valve After closing the (14), the second on-off valve (16), the third on-off valve (24) and the atmosphere release valve (22), the fourth on-off valve (26) is opened and the pressure reducing mechanism ( Activate 8). By the operation of the pressure reducing mechanism (28), the pressure in the pressure reducing introduction tank (13) is reduced. When the inside of the depressurization introduction tank (13) becomes a certain depressurized state, the fourth on-off valve (26) is closed, and then the first on-off valve (14) is opened, thereby causing contamination. The waste liquid in the liquid storage unit (10) is reduced Due to the negative pressure in 3), it is introduced into the vacuum introduction tank (1 3) via the transfer pipe (1 2).

In introducing the waste liquid (11) into the vacuum introduction tank (13), the transfer of the waste liquid (11) to the filtration means (18) is performed without using a pump. Therefore, there is no restriction on the chemical resistance and heat resistance of the pump to be treated. In addition, the filtration operation can be performed promptly regardless of the size and material of the particle diameter contained in the waste liquid (11). In addition, the waste accumulated at the lower bottom of the waste storage part (10) was quickly introduced into the filtration means together with the waste (11), and the introduction of the accumulated waste, which was difficult with a pump, was difficult. Is also possible.

After the introduction of the waste liquid, the waste liquid (11) is filtered by the filtration means (18). Although any method can be used for the filtration by the filtration means, in one embodiment, a filter, a screen, or the like is disposed on the inner periphery of the vacuum introduction tank (13), and the filtration means ( The waste liquid (11) is returned to the waste liquid storage part (10) by passing through 18).

The restoration of the waste liquid (11) from the decompression introduction tank (13) to the waste liquid storage section (10) is performed by the first on-off valve (14), the second on-off valve (16), and the fourth on-off valve. After closing the valve (26), the air release valve (22) and the third on-off valve (24) are opened, so that the filtered waste liquid (11) can be stored in the waste liquid storage part (10). Can be restored. In this case, if the waste liquid storage section (10) is located below the vacuum introduction tank (13), the pressure of the waste liquid (11) is reduced by the weight of the waste liquid (11). ) Can be easily transferred to the waste liquid storage section (10). Also, the waste liquid (11) can be restored to the waste liquid storage part (10) more quickly, or the waste liquid storage part (10) can be flush with the vacuum introduction tank (13). Or, when it is located further upward, the pressure gas is introduced from the pressure gas inlet (17) into the reduced-pressure introduction tank (13).

The transfer of the waste liquid (11) from the vacuum introduction tank (13) to the waste liquid storage part (10) using the pressurized gas is performed by the air release valve (22) and the first on-off valve (14). ) And the fourth on-off valve (26) are closed, and then the third on-off valve (24) is opened. As a result, the second on-off valve (16) is opened, and the pressurized gas is introduced into the reduced-pressure introduction tank (13) from the pressure gas inlet (17). By introducing the pressurized gas, the waste liquid (11) in the reduced-pressure introduction tank (13) can be forcibly transferred under pressure into the waste liquid storage part (10). Then, when the waste liquid (11) in the vacuum introduction tank (13) is pressure-transferred to the waste liquid storage part (10) by the introduction of the pressurized gas, the waste liquid (11) can be quickly transferred. Not only is it possible, but also the waste liquid (11) remaining in the decompression introduction tank (13) and adhering to the waste is separated from the waste within a certain range, and the waste liquid storage part (10) side The waste will be drained because it is transferred to

If the pressurized gas is introduced into the pressure-reducing tank (13) even after the draining of the filtered sewage (11) and the draining of the sewage are completed, the pressure gas will be released to the sewage collection unit (1). 0) Sent to (1) to wrap the waste liquid (11) in the waste liquid storage part (10). As a result, the waste contained in the waste liquid (11) in the waste liquid storage part (10) floats in the waste liquid (11). In this floating state, if the pressure inside the vacuum introduction tank (13) is reduced and the waste liquid (11) in the waste liquid storage part (10) is sucked into the vacuum introduction tank (13), the waste will be reduced. The transfer efficiency into the vacuum introduction tank (13) can be increased, and efficient filtration can be performed.

Next, after closing the third on-off valve (24), the first on-off valve (14), the second on-off valve (16) and the air release valve (22), the fourth on-off valve (2 6) Is released, the pressure reducing mechanism (28) is operated, and the pressure in the vacuum introduction tank (13) is reduced. The waste liquid (1 1) remaining in the vacuum introduction tank (13) and adhering to the contaminants is removed. ) Can reduce the boiling point, evaporate and evaporate as a result of decompression by the decompression mechanism (28), and dry filth. By removing contaminants adhering to the contaminants in this way, it is possible to reduce environmental pollution caused by discarding solvents, cutting oils, and other liquids while keeping them adhered. Becomes The waste liquid (11) vaporized and evaporated from the waste is liquefied and condensed by a condenser (not shown) or the like and collected.

If the filtering means (18) such as a filter installed in the vacuum introduction tank (13) is removable from the vacuum introduction tank (13), the filtering means By removing (18) from the vacuum introduction tank (13) and taking it outside from the vacuum introduction tank (13), it is extremely easy to remove dried contaminants. Also, the first on-off valve (14) and the third on-off valve (24) are, for example, butterfly valves and the like which have a low flow resistance of liquid and are not easily clogged by dirt. If it is used, the waste liquid (11) can be quickly introduced into the vacuum introduction tank (13) via the transfer pipe (12), and the waste liquid storage (10) from the vacuum introduction tank (13) can be used. It is possible to restore the waste liquid (11) to the wastewater.

In the above embodiment, it is assumed that the liquid discharge side of the waste liquid storage unit (10) and the liquid introduction side of the vacuum introduction tank (13) are separated by the transfer pipe (12). And the liquid discharge side of the vacuum introduction tank (13) and the liquid introduction side of the waste liquid storage section (10) are not separated by the discharge pipe (23). Fixedly connected. However, in another different embodiment, the transfer pipe (12) and the discharge pipe (23) connected to the waste storage part (10) are connected to and detached from the waste storage part (10). If the transfer pipe (1 2) and the discharge pipe (2 3) can be connected to any waste liquid storage section (10), the decompression tank (13) can be connected to any waste liquid storage section. It is possible to transfer to the position where (10) is installed and to filter the filth (11) in any filth container (10), which significantly improves the efficiency of use as a filtration device. It can be increased.

The connection method of the transfer pipe (12) and the discharge pipe (23) to the above-mentioned optional waste storage section (10) is as follows.着脱 The discharge pipe (2 3) may be formed with a detachable opening, or the transfer pipe (1 2) and the discharge pipe (2 3) may be inserted from the upper part of the waste liquid storage section (10). You can use it.

In the above embodiment, the depressurization introduction tank (13) is one tank, and this one depressurization introduction tank (13) is directly connected to the decompression mechanism (28). The wastewater (11) is introduced by depressurizing the inside of the) with the decompression mechanism (28). However, when directly depressurizing the one decompression introduction tank (13), the decompression inside the decompression introduction tank (13) is accompanied by the introduction of the waste liquid (11). Since the degree is reduced, only a small amount of sewage can be introduced than the volume of the vacuum introduction tank (13). For this reason, filtration is performed by introducing a waste liquid that is less than the filtration capacity of the vacuum introduction tank (13), which is not efficient.

Thus, in another different embodiment, as shown in FIG. 2, the vacuum introduction tank (13) provided with the filtration means (18) for the waste liquid (11) is more than the vacuum introduction tank (13). A large-capacity auxiliary pressure-reducing tank (13a) is connected, and the auxiliary pressure-reducing tank (13a) is connected to the wastewater storage unit (10), and an auxiliary pressure-reducing tank (13a) is connected. A pressure reducing mechanism (28) is connected to 13a) to reduce the pressure in the auxiliary vacuum introducing tank (13a). Then, by introducing negative liquid from the waste liquid storage unit (10) using negative pressure into the auxiliary reduced pressure introduction tank (13a) in the reduced pressure state, the volume of the reduced pressure introduction tank (13) is reduced. A larger amount of waste liquid (11) can be introduced into the auxiliary vacuum introducing tank (13a), which is the same as or larger than the volume of the vacuum introducing tank (13).

If the waste liquid (11) is introduced from the auxiliary vacuum introduction tank (13a) to the vacuum introduction tank (13) via the fifth on-off valve (32), the vacuum introduction tank (13) The waste liquid (11) corresponding to the filtration capacity can be introduced into the vacuum introduction tank (13). Since the vacuum introduction tank (13) can sufficiently introduce the waste liquid (11) corresponding to the filtration capacity, it is possible to reduce the size of the vacuum introduction tank (13). You can get it. In addition, if the auxiliary vacuum introduction tank (13a) is enlarged, the filtration operation is completed and the filtered wastewater (11) is discharged to the wastewater storage unit (10) or other destinations. Without performing decompression, etc., the remaining waste liquid (11) can be immediately introduced from the auxiliary vacuum introduction tank (13a) to the vacuum introduction tank (13) to perform filtration work. Filtering work can be repeated and quickly performed in a small vacuum introduction tank (13).

In addition, the auxiliary vacuum introduction tank (13a) is arranged above the vacuum introduction tank (13), and the waste liquid (11) in the auxiliary vacuum introduction tank (13a) is gravity driven. To introduce it into the vacuum introduction tank (13). The auxiliary pressure-reducing tank (13a) is connected to the pressure gas inlet (17), introduces the pressure gas, and removes the waste liquid (13a) in the auxiliary pressure-reducing tank (13a). 1) is reduced by the pressure of the pressurized gas. It may be possible to transfer to the pressure introduction tank (13).

Further, in this embodiment, when the waste liquid discharge side of the waste liquid storage part (10) and the liquid introduction side of the auxiliary vacuum introduction tank (13a) are connected by the transfer pipe (12), the pressure is reduced. The liquid discharge side of the introduction tank (13) and the liquid introduction side of the waste liquid storage part (10) are connected by a discharge pipe (23). In addition, the decompression pipe (27) and the auxiliary decompression introducing tank (13a) are connected by a decompression communication pipe (34) via a sixth on-off valve (33), and the auxiliary decompression pipe is connected. The pressure in the introduction tank (13a) can be reduced. The pressure reduction in the auxiliary pressure-reducing tank (13a) may be performed only in the auxiliary pressure-reducing inlet tank (13a). However, when the pressure is reduced, the fifth opening / closing valve (32) is used. May be opened to reduce the pressure in the vacuum introduction tank (13) and the auxiliary vacuum introduction tank (13a) at the same time. In this case, a large number of sewage liquids (11) can be introduced into the vacuum introduction tank (13) and the auxiliary vacuum introduction tank (13a) in one decompression operation, so that the number of times of decompression work is reduced. As a result, it is possible to repeat filtration operations several times in one decompression operation.

In the above embodiment, the filtration means (18) is arranged in the reduced-pressure introduction tank (13). However, the filtration means (18) is not always required to be arranged in the reduced-pressure introduction tank (13). A filter (18) for filtering the waste liquid (11) may be arranged in a flow path from the introduction side to the discharge side of the waste liquid (11). The waste liquid can be filtered by the filtration means (18) during the introduction process or the discharge process into the vacuum introduction tank (13). Further, in the case of performing vacuum drying of the filth in the vacuum introduction tank (13), it is preferable to provide a filtration means in the vacuum introduction tank (13). Industrial applicability

Since the present invention is configured as described above and does not use a pump in filtering liquid, it not only simplifies the mechanism but also reduces the liquid resistance and heat resistance of the pump which has been a problem in the past. No consideration is needed. In addition, even if there are large particles, chips and the like contained in the sewage, the sewage can be transferred without any problem, and if the pump is damaged, the pump is damaged. There is no difficulty in transferring sewage.

In addition, since the decompression means is used, the transfer of the waste liquid to the decompression introduction tank can be performed extremely quickly, and a quick filtration operation can be performed. In addition, the use of a decompression mechanism makes it extremely easy to dry filth remaining in the depressurization introduction tank after completion of filtration, thereby minimizing adverse effects on the environment in the treatment of filth.

Claims

The scope of the claims

The wastewater is introduced into the vacuum introduction tank, which is connected to a pressure reducing mechanism and reduced in pressure, using the negative pressure due to the reduced pressure, and a filtering means for the wastewater is provided in a flow path from the introduction side to the discharge side of the wastewater. A method for filtering waste water, comprising disposing the waste water and filtering the waste water by the filtration means.

A decompression mechanism is connected to the decompression mechanism to reduce the pressure. The negative pressure generated by the decompression is used to introduce sewage, and a decompression introduction tank capable of discharging sewage is also provided. And a filtration means arranged in a flow path for filtering waste liquid. A waste gas filtration device is characterized in that a pressurized gas can be introduced into the reduced pressure introduction tank, 2. The method for filtering waste liquid according to claim 1, wherein the discharge can be performed by pressure.

3. The apparatus for filtering contaminated liquid according to claim 2, wherein a pressure gas can be introduced into the pressure-reducing tank, and the filtered liquid can be discharged by the pressure of the pressure gas.

The method for filtering waste liquid according to claim 1 or 3, wherein the pressure in the vacuum introduction tank is reduced by reducing the pressure in the tank (2) and the remaining waste is dried under reduced pressure. 5. The apparatus for filtering waste liquid according to claim 2, wherein the reduced-pressure introduction tank reduces the pressure inside the tank and enables the remaining waste to be dried under reduced pressure.