JP7049109B2 - Treatment method of oil-impregnated wastewater - Google Patents

Description

In the present invention, oil-containing wastewater containing oil such as industrial wastewater and domestic wastewater is aggregated and separated into an oil layer, an aqueous layer, and a sludge layer by static or a flocculant, and then the emulsified oil contained in the aqueous layer water is separated by an oil-water separator. The present invention relates to a method for treating oil-impregnated wastewater which is treated to obtain membrane-filtered treated water.

Contains cutting oil used in metal processing such as cutting, grinding, casting, rolling, polishing, etc. in the machine industry and metal industry, wastewater containing machine oil, lubricating oil, etc., and oil-based products such as plasticizers from chemical plants. Wastewater to be discharged, industrial wastewater such as wastewater from the food industry containing vegetable oil, animal oil, etc., and wastewater such as domestic wastewater must be treated to a state where they can be discharged into rivers and the sea, or to a state where they can be reused. There is.

Conventionally, in addition to the methods of evaporation and precipitation, a method of treating emulsified organic substance-containing wastewater such as emulsified oil with a membrane separation device using an ultrafiltration membrane or the like has been used (Patent Documents 1, 2 and 3). ).

However, in the membrane treatment process for oil-containing wastewater such as industrial wastewater and domestic wastewater, the membrane deteriorates over time and the membrane is damaged due to fine metal fragments in the raw wastewater, and part of the raw water is treated water. There is a problem that it leaks to the side, and there is a problem that a part of the oil leaks to the treated water side due to the oil emulsification state and the oil content of the wastewater fluctuating due to the fluctuation of the manufactured product type of the factory.

As a method of detecting film breakage during film treatment, Patent Document 4 states that the detection length is lengthened and foreign matter is mixed in by changing the flow path by colliding the liquid flowing into the sight glass device with the partition wall. A technique for preventing the sight glass window from becoming dirty by colliding the flowing liquid with the sight glass window of the sight glass device while improving the visibility of the liquid turbidity due to the above is disclosed, and the visibility is not easy. In the case of turbidity, it is described that turbidity is detected by a sensor that detects the amount of light transmitted through the fluid.

However, Patent Document 4 does not describe the monitoring of filtered water from the membrane separation device, and the prevention of stains on the sight glass window is insufficient, especially in the monitoring of drainage leakage to the filtered water due to membrane defects in oil-containing wastewater treatment. Since the sight glass device is complicated, there is a problem that it takes time and effort to disassemble and clean the sight glass window.

Japanese Unexamined Patent Publication No. 60-38004 Japanese Unexamined Patent Publication No. 60-68005 Japanese Unexamined Patent Publication No. 2008-183470 Japanese Unexamined Patent Publication No. 2006-17523

Therefore, the present invention detects the outflow of oil due to a membrane abnormality or the like in the UF membrane filtration treatment of wastewater containing emulsified oil by a simple turbidity detection mechanism, and promptly responds to the abnormal turbidity to cause the outflow of unspecified wastewater. To prevent troubles in the post-treatment process and maintain the UF membrane filtration membrane water in a state where it can be drained to the outside or in a reusable state, and to re-use the UF membrane filtration membrane water with an RO membrane (reverse osmosis membrane). It is a method for treating oil-impregnated wastewater in which the filtration treatment is controlled so as to maintain a treatable state, and provides a method for treating oil-containing wastewater in which the turbidity detection mechanism can be easily cleaned.

In order to solve the above problems, the method for treating oil-impregnated wastewater of the present invention has the following features.

(1)
In a method in which wastewater containing emulsified oil is passed through a UF membrane filtration treatment device equipped with an oil-water separable UF membrane to perform UF membrane filtration treatment to obtain UF membrane filtration treatment water having a lower oil content.
A sight glass and a non-contact photoelectric sensor are installed in combination as a turbidity detection mechanism to detect the outflow of oil in the outlet pipe of the UF membrane filtration treated water.
When the turbidity is detected by the turbidity detection mechanism, the UF membrane filtration processing device is stopped.
The concentrated oil water in the UF membrane filtration treatment device is discharged, and the concentrated oil water is discharged.
A method for treating oil-impregnated wastewater that restarts and controls water flow to the UF membrane filtration treatment device after cleaning or replacing the UF membrane.
A method for treating oil-impregnated wastewater , wherein the sight glass is a sight glass provided with a branch screw stopper .

(2)
In (1), when the turbidity detection by the turbidity detection mechanism is lower than the predetermined reference value or level in the continuous measurement of the UF membrane filtration treated water by the photoelectric sensor, the site. A method of treating oil-impregnated wastewater, which is to visually check for turbidity from the glass.

(3)
In (1) or (2) , a method for treating oil-containing wastewater in which the photoelectric sensor used in the turbidity detection mechanism is a sensor using laser light.

(4)
In any of (1) to (3) , the branch screw plug is composed of a branch pipe branched from the sight glass main body provided with the branch screw plug and a screw plug that closes the opening at the tip of the branch pipe. A method for treating oil-impregnated wastewater, wherein the screw plug is detachably provided in the opening, and the inside of the sight glass window portion can be cleaned from the opening from which the screw plug is removed.

(5)
In any one of (1) to (4) , a method for obtaining highly treated water by further RO membrane treating the UF membrane filtration treated water.
When the turbidity detection mechanism detects turbidity, the supply of the UF membrane filtration membrane water to the RO membrane treatment apparatus is stopped, the UF membrane filtration treatment apparatus is stopped, and the concentrated oil water in the UF membrane filtration treatment apparatus is discharged. A method for treating oil-impregnated wastewater that restarts and controls water flow after cleaning or replacing the UF membrane.

According to the method for treating oil-containing wastewater of the present invention, oil-containing wastewater such as industrial wastewater and domestic wastewater, especially emulsified oil-containing wastewater such as metal processing mold mold release agents and iron-based cutting oil, is treated with oil water. In a method of passing water through a separable UF membrane to obtain UF membrane filtration-treated water having a lower oil content, the outlet pipe of the UF membrane filtration-treated water is provided with a branch screw plug as a turbidity detection mechanism for detecting the damage of the membrane. By installing and controlling the ultrafiltration and photoelectric sensor in combination, it is possible to detect drainage leakage of the membrane due to deterioration and breakage of the membrane and changes in drainage properties at an early stage, and easily clean the inner surface of the sight glass window. can.
As a result, when an abnormality is detected in the UF membrane filtration treated water, an alarm is issued and the equipment is temporarily stopped to prevent the water quality from deteriorating when the UF membrane filtration treated water is discharged to the outside and the water quality when it is reused internally. Stabilization and stabilization treatment when re-treating with RO membrane in the subsequent stage are possible.

In the present invention, by using a photoelectric sensor using a laser beam, it is possible to accurately detect stains on treated water due to film breakage or the like.

It is a schematic diagram explaining the treatment method of oil-containing wastewater of this invention. It is a schematic diagram explaining the treatment method of oil-containing wastewater including RO treatment in the latter part of this invention. A perspective view (a), a BB sectional view (b), a CC sectional view (c), and a left side of a turbidity detection mechanism in which a sight glass equipped with a branch screw plug used in the present invention and a photoelectric sensor are combined. It is a sectional view (d). It is a graph which shows the change of the turbidity measurement value with time which is the Example of this invention. It is a graph which shows the change of the turbidity measurement value with time which is the Example of this invention. It is a graph which shows the change of the turbidity measurement value with time which is the practice of this invention. It is the perspective view (a) and the DD sectional view (b) of the simplified sight glass used in this invention.

In the present invention, wastewater containing emulsified oil is passed through a UF filtration membrane device provided with an oil-water separable UF membrane, and the turbidity of the obtained UF membrane filtration-treated water is measured by a turbidity detection mechanism to separate the emulsified oil. This is a method for treating oil-containing wastewater, in which the flow of wastewater to the UF membrane filtration treatment device is stopped when turbidity is detected, and the UF membrane filtration treatment device is cleaned and the membrane is replaced.
By this oil-impregnated wastewater treatment method, the water quality of the UF membrane filtration treated water can be maintained in a state where it can be drained to the outside or in a reusable state, and the UF membrane filtration treated water is further re-used with an RO membrane or the like. Even in the case of processing, stable operation of each processing device becomes possible.

In the present invention, the turbidity detection mechanism is basically a combination of a sight glass and a non-contact photoelectric sensor that does not come into contact with the measurement target, preferably a sight glass having a branch screw plug and a non-contact photoelectric sensor. Consists of combinations.
When the UF membrane filtration treated water exceeds a predetermined standard value or level by continuous measurement with a photoelectric sensor, after visually confirming the turbidity, an alarm etc. is issued and the equipment is temporarily suspended. The equipment will be put into operation after stopping and cleaning the UF membrane filtration device or replacing the membrane.
By controlling the operation in this way, it is possible to prevent deterioration of water quality due to leakage of discharged water to the outside, stabilize the quality of recycled water, and stabilize treatment of the RO membrane treatment equipment in the subsequent stage.

The sight glass used in the present invention can be used for confirming changes in the presence or absence of fluid flowing in pipes used in manufacturing processes, water treatment processes, etc. of various industries, changes in fluid mixing state, etc., and visually confirming changes in flow rate. Similar to those used in clear glass joints for use can be used.
For example, as shown in FIG. 7, a simple sight glass 7 having a sight glass main body 4 connected in the flow direction of the fluid in the pipe and a sight glass window portion 3 having a structure for monitoring from a direction perpendicular to the flow direction is provided. , It is preferable because it is easy to clean the dirt of the sight glass window portion 3.
Further, as shown in FIG. 3, in the sight glass 1a provided with the branch screw plug 2 and the sight glass window portion 3 on the sight glass main body 4, the opening at the tip of the branch pipe 2a branched from the sight glass main body 4 is closed. A structure in which the screw stopper 2b of the above is detachably provided is preferable. With that structure, when the inner surface of the sight glass window 3 becomes dirty, it becomes easy to remove the screw plug 2b and insert a cleaning tool through the opening to remove the dirt inside the sight glass window 3. .. Further, the photoelectric sensor (photoelectric sensor projection unit 1b and photoelectric sensor light receiving unit 1c) is fixed to the frame 4a or the like connected to the sight glass main body 4 toward the sight glass window portion 3 and is not attached to the sight glass window portion 3. By preparing for contact, it becomes the turbidity detection mechanism 1 of the present invention.

FIG. 1 shows a schematic diagram of a method for treating oil-impregnated wastewater according to the present invention. Emulsified oil-containing wastewater (raw water) from the raw water tank is sent to the concentrated circulation tank to store a specific amount, and then treated with an oil-water separable tubular type UF membrane filtration device (oil-water separation membrane) to concentrate oil water and treated water. The concentrated oil water is returned to the concentrated circulation tank, and the treated water is discharged to the sewage or sent to the subsequent equipment for reuse while continuously measuring the turbidity by the turbidity detection mechanism.
By circulating the emulsified oil-containing wastewater between the concentrated circulation tank and the tubular type UF membrane filtration device, when the oil content in the concentrated oil water exceeds a specific concentration, the concentrated oil water is discharged to empty the concentrated circulation tank. After injecting the emulsified oil-containing wastewater into the concentrated circulation tank again to store a specific amount, the circulation treatment by the tubular type UF membrane filtration device is restarted.

A UF membrane (ultrafiltration membrane) is used for the UF membrane filtration device having oil-water separability used in the present invention. For example, in the case of tubular type UF membrane filtration, emulsified oil, solid matter, metal powder, waste oil, etc. are passed by passing water-soluble oil-impregnated wastewater through the UF membrane that is in close contact with the inner surface of the porous fiber. Remains in the tube and is returned to the concentration circulation tank.
The water to be treated is concentrated as the water permeates from the UF membrane filtration treatment device. Basically, the treated water discharged from the UF membrane filtration treatment device is oil-free and does not contain solid content.

The RO membrane (reverse osmosis membrane) used in the present invention is a membrane that allows water to pass through and does not allow impurities other than water such as ions and salts to permeate, and the pore size is approximately 2 nanometers. Below, those smaller than the UF membrane can be used. By pressurizing the treatment water side such as wastewater containing impurities such as ions and salts, the treated water passing through the RO membrane and containing no impurities can be obtained.

The preferred photoelectric sensor of the present invention (photoelectric sensor floodlight section and photoelectric sensor light receiving section) has a structure integrated with a sight glass provided with a branch screw plug to form a turbidity detection mechanism. As a result, the inner surface of the sight glass window can be easily cleaned from the opening by removing the screw plug at the tip of the branch tube of the sight glass without removing the photoelectric sensor.
When the photoelectric sensor and the conventional sight glass without a branch screw plug are simply combined, it is necessary to remove the sight glass window from the pipe and clean it. Therefore, as shown in Fig. 7, the internal structure of the liquid is simple. A general simple sight glass 7 that monitors the flow from a perpendicular direction is preferable, and a structure in which the photoelectric sensor can be easily removed is preferable.

The photoelectric sensor used in the present invention is a sensor for detecting turbidity, and preferably by using a laser beam, the directivity is high and the coherence is good, so that the accuracy of detecting the occurrence of turbidity is improved.
Generally, a transmitted light detection sensor is used when the turbidity is large, and a scattered light detection sensor is used when the turbidity is small. Generally, since the turbidity becomes large, a transmitted light detection sensor having a small device and being simple is preferably used.
For example, the turbidity monitoring measurement value in the examples of the present invention is a numerical value of the ratio of the measured light transmission amount of the monitored liquid to the light transmission amount of the transparent liquid in the ideal state by the transmitted light detection photoelectric sensor. If the liquid to be monitored is a transparent liquid due to the transmission light attenuation factor of the device or the like, the value is around 2500. However, when leakage occurs due to a change in the characteristics of the treated water, the amount decreases to about 1000 or less, and when leakage occurs due to damage to the filtration membrane, the amount decreases to about 500 or less.

(Example 1)
Polyacrylic acid (mass average molecular weight 25,000) flocculant is added to wastewater containing cutting oil (COD 1000 mg / L, n-hexane extract amount 100 mg / L) from a machine parts processing factory so as to be 200 mg / L. After treatment, it was aggregated and separated into an oil layer, an aqueous layer, and a sludge layer.
The obtained aqueous layer water is adjusted to pH 4.5 with a sulfuric acid solution, and contains high-concentration emulsified oil by a tubular type UF membrane filtration treatment device using a tubular module (MH-25) manufactured by Daisen Membrane Systems. It was separated into water (concentrated oil water) and treated water.
At the outlet of the treated water, a turbidity detection mechanism that combines a sight glass equipped with a branch screw plug and a laser photoelectric sensor is installed, and since turbidity was detected in the treated water visually with the photoelectric sensor, the UF membrane filtration processing device The UF membrane was washed, and the UF membrane was replaced because it was confirmed that the UF membrane was damaged.
Along with the cleaning work of the UF membrane, the screw plug at the tip of the branch of the sight glass was removed, and a cleaning tool was inserted through the opening to clean the window of the sight glass.
After the replacement of the UF membrane and the cleaning of the sight glass window were completed, the UF membrane filtration processing apparatus was restarted. Almost no treated water containing emulsifying oil was discharged from the occurrence of membrane breakage to the stoppage, and the stoppage time was about 1 hour. FIG. 4 shows a graph showing changes in turbidity measurement values over time.

(Example 2)
In Example 2, the treated water obtained by the tubular type UF membrane filtration treatment device of Example 1 is further treated with an RO membrane separation device (BW30XFR400 manufactured by Dow Chemical Co., Ltd.) to separate it into an emulsified oil-containing layer and highly treated water. Has a step to do.
Then, a turbidity detection mechanism that combines a sight glass equipped with a branch screw plug installed at the treatment water outlet of the tubular type UF membrane filtration processing device and a laser photoelectric sensor detects turbidity in the treated water visually with the photoelectric sensor. Therefore, the RO membrane separation device and the tubular type UF membrane filtration treatment device were stopped to clean the tubular type UF membrane. The UF membrane was not replaced because it was confirmed that the cause of the turbidity was the overconcentration of the agglomerate ultrafiltration water.
Along with the cleaning work of the UF membrane, the screw plug at the tip of the branch pipe of the sight glass was removed, and a cleaning tool was inserted through the opening to clean the inside of the window of the sight glass. After cleaning the UF membrane, confirming the cause of turbidity, and cleaning the sight glass window, the UF membrane filtration device was restarted, and the RO membrane separation device was restarted.
Almost no treated water containing emulsified oil was discharged from the drainage leak to the stop, and the RO membrane separation device restarted normally with no abnormality in the membrane. The stop time was about 1 hour. FIG. 5 shows a graph showing changes in turbidity measurement values over time.

(Example 3)
In Example 1, a UF membrane filtration processing device was operated using a general simple sight glass and a laser photoelectric sensor instead of the sight glass provided with a branch screw plug as a turbidity detection mechanism.
The turbidity was detected by the photoelectric sensor, and the turbidity was confirmed visually, so when the UF membrane filtration processing device was stopped and the UF membrane was checked, the membrane was found to be damaged, so the membrane was replaced and restarted, but the sight glass window The base data of the turbidity measurement value deteriorated due to the dirt on the part. The UF membrane filtration treatment device was stopped, the sight glass was disassembled, the sight glass window was cleaned, and then the operation was restarted.
Almost no treated water containing emulsifying oil was discharged from the membrane breakage to the stoppage, and the stoppage time was about 12 hours. FIG. 6 shows a graph showing changes in turbidity measurement values over time.

(Comparative Example 1)
In Example 3, the UF membrane filtration treatment apparatus was operated while visually confirming the turbidity of the UF membrane filtration treatment water every 6 hours using a general flow orthogonal monitoring type simple sight glass without using a photoelectric sensor. Since turbidity was visually confirmed, the UF membrane was found to be damaged when the UF membrane filtration processing device was stopped and the UF membrane was checked. The sight glass window was very dirty, so I disassembled the sight glass, cleaned the sight glass window, and then restarted the operation. However, a large amount of treated water containing emulsifying oil was discharged from the occurrence of UF membrane breakage to the stoppage, and the stoppage time was about one day.

(Comparative Example 2)
In Example 1, a visible filter was installed at the UF membrane filtration treatment water outlet instead of the turbidity detection mechanism, and a visual check was performed every 6 hours. Was removed and cleaned, and the UF membrane was cleaned and replaced by checking for membrane damage. It took about two days to remove and clean both of them, and a large amount of treated water containing emulsifying oil was discharged from the occurrence of membrane damage to the time when filter stains were visible.

As described above, from the results of Examples 1 to 3 and Comparative Examples 1 and 2, according to the oil-containing wastewater treatment method of the present invention, even if wastewater leaks to the UF membrane filtration treated water due to UF membrane breakage or the like occurs, it is rapid. Correspondence is possible. The treated water containing emulsified oil is rarely discharged, and in particular, in Examples 1 and 2 using the sight glass provided with the branch screw plug, the oil-containing wastewater treatment device can be restarted with a short stop. became.

According to the method for treating oil-containing wastewater according to the present invention, the emulsified oil content of the wastewater containing oil such as industrial wastewater and domestic wastewater is removed by the membrane filtration treatment of the UF membrane, and the turbidity of the UF membrane filtration treated water can be easily made. It is possible to monitor drainage leakage from the UF membrane by continuous measurement by a detection mechanism that is easy to clean and visual confirmation when abnormal data is generated. As a result, the UF membrane filtration treated water can be maintained in a stable water quality, and it is possible to prevent troubles at the time of draining or reusing the treated water to the outside, or at the time of retreatment with the RO membrane in the subsequent stage.

1 Turbidity detection mechanism 1a Sight glass 1b Photoelectric sensor floodlight
1c Photoelectric sensor light receiving part 2 Branch screw plug 2a Branch tube 2b Screw plug 3 Sight glass window 4 Sight glass main body 4a Frame 5 Water flow inlet to detection mechanism 6 Water flow outlet from detection mechanism 7 Simple sight glass

Claims (5)

In a method in which wastewater containing emulsified oil is passed through a UF membrane filtration treatment device equipped with an oil-water separable UF membrane to perform UF membrane filtration treatment to obtain UF membrane filtration treatment water having a lower oil content.
A sight glass and a non-contact photoelectric sensor are installed in combination as a turbidity detection mechanism to detect the outflow of oil in the outlet pipe of the UF membrane filtration treated water.
When the turbidity is detected by the turbidity detection mechanism, the UF membrane filtration processing device is stopped.
The concentrated oil water in the UF membrane filtration treatment device is discharged, and the concentrated oil water is discharged.
A method for treating oil-impregnated wastewater that restarts and controls water flow to the UF membrane filtration treatment device after cleaning or replacing the UF membrane.
A method for treating oil-impregnated wastewater , wherein the sight glass is a sight glass provided with a branch screw stopper . When the turbidity is detected when the measured value or level of turbidity is lower than a predetermined reference value or level in the continuous measurement of the UF membrane filtration-treated water by the photoelectric sensor, the turbidity is visually detected through the sight glass. The method for treating oil-containing wastewater according to claim 1, which is to be confirmed. The method for treating oil-containing wastewater according to claim 1 or 2 , wherein the photoelectric sensor is a sensor using laser light. The branch screw plug is composed of a branch pipe branched from the sight glass main body of the sight glass provided with the branch screw plug and a screw plug that closes the opening at the tip of the branch pipe.
The claim is characterized in that the screw plug is detachably provided in the opening, and the inside of the sight glass main body of the sight glass window portion can be washed from the opening from which the screw plug is removed. The method for treating oil-impregnated wastewater according to any one of claims 1 to 3 . A method for obtaining highly treated water by further treating the UF membrane filtration treated water with an RO membrane.
When the turbidity detection mechanism detects turbidity, the supply of the UF membrane filtration treatment water to the RO membrane treatment apparatus is stopped and the UF membrane filtration treatment apparatus is stopped.
The invention according to any one of claims 1 to 4 , wherein the concentrated oil water in the UF membrane filtration treatment apparatus is discharged, the UF membrane is washed or replaced, and then the water flow is restarted and controlled. How to treat oil-impregnated wastewater.

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