JP2013052327A - Water treatment method and water treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water treatment apparatus capable of maintaining the membrane filteration efficiency of a membrane module over a long period of time.SOLUTION: The water treatment apparatus includes: a foaming tank 1 where wastewater containing oil flows in; a foam detector 21 that detects an amount of foam in the foaming tank 1; a surfactant supply device that supplies a surfactant to the foaming tank 1; a controller 30 that controls the supply quantity of the surfactant to increase the addition amount of the surfactant when the amount of foam in foaming tank 1 does not exceed an predetermined value, and to decrease the addition amount of the surfactant when the amount of foam exceeds a predetermined value; and the membrane module 5 disposed in the downstream of the foaming tank 1.

Description

  The present invention relates to a water treatment method and a water treatment apparatus for wastewater containing oil.

  As one of the water treatment methods, waste water is introduced into an activated sludge treatment tank and treated with activated sludge to remove organic matter, etc., then reverse osmosis (RO) membrane, ultrafiltration (UF) membrane, microfiltration ( MF) Membrane modules, hollow fiber (HF) membranes and other membrane modules equipped with filtration membranes are passed through and subjected to membrane filtration treatment for suspended microorganisms, other suspended substances (abbreviated as SS), and other impurities. There is a membrane separation activated sludge method (Membrane BioReactor) to separate.

  The membrane separation activated sludge method has the merit that the final sedimentation site can be omitted and the apparatus can be miniaturized because solid-liquid separation is performed using a membrane module.

  However, when wastewater containing oil is subjected to membrane filtration, there is a problem that the oil adheres to the membrane and clogs, the frequency of washing the membrane module increases, and water treatment efficiency decreases.

  Patent Document 1 discloses that a flocculant is added to oil-containing wastewater to coagulate and precipitate the oil and organic matter in the wastewater to reduce the oil and suppress clogging of the membrane.

JP-A-2-268893 Japanese Patent Publication No. 6-59478

  However, in the method disclosed in Patent Document 1, a large amount of sludge is generated, and there is a problem that the sludge treatment cost increases. Even with this method, depending on the properties of the waste water, the oil component may not be sufficiently reduced and may be used in the membrane module, and clogging of the membrane may not be sufficiently suppressed.

  Therefore, the objective of this invention is providing the water treatment method and water treatment apparatus which can maintain the membrane filtration efficiency in a membrane module over a long period of time.

  In order to achieve the above object, the water treatment method of the present invention introduces wastewater containing oil into a foaming tank, adds a surfactant to the wastewater in the foaming tank, and mixes the wastewater with a membrane module to form a membrane. A water treatment method for filtration, wherein the amount of foaming in the foaming tank is detected, and when the amount of foaming does not exceed a predetermined value, the addition amount of the surfactant is increased so that the amount of foaming is predetermined. When the value is exceeded, the addition amount of the surfactant is controlled so as to decrease the addition amount of the surfactant.

  According to the water treatment method of the present invention, waste water containing oil is introduced into a foaming tank, and the waste water containing oil and the surfactant are mixed in the foaming tank. At that time, since the addition amount of the surfactant is controlled on the basis of the foaming amount in the foaming tank, the surfactant required for micellizing the oil in the wastewater can be supplied almost without excess or deficiency. For this reason, it is possible to emulsify and disperse the oil contained in the waste water almost completely into micelles and prevent the oil from adhering to the membrane. Further, since the addition amount of the surfactant can be optimized, the drug cost can be reduced.

  In the water treatment method of the present invention, it is preferable that the surfactant is sprayed toward the membrane surface of the membrane module continuously or intermittently during the membrane filtration treatment. According to this aspect, since the oil component that has adhered to or near the membrane module forms micelles by the reaction with the surfactant injected toward the membrane surface, clogging of the membrane can be efficiently prevented. . Furthermore, since the organic substance such as protein is denatured and swelled by the surfactant, it is possible to prevent the solid matter other than oil from adhering to the film.

  In the water treatment method of the present invention, the amount of foaming in the foaming tank is preferably detected by a method selected from an optical method, an electrical method, and an image method.

  In the water treatment method of the present invention, a biodegradable surfactant is preferably used as the surfactant. According to this aspect, the influence on the environment to the surroundings can be reduced.

  In the water treatment method of the present invention, it is preferable that the waste water that has passed through the foaming tank is introduced into an activated sludge treatment tank and treated with activated sludge, and then subjected to membrane filtration through the membrane module. According to this aspect, in the activated sludge treatment tank, organic matter and micellized oil can be treated, and cleaner treated water can be obtained.

  Further, the water treatment apparatus of the present invention includes a foaming tank into which waste water containing oil is introduced, a foam detector that detects the amount of foaming in the foaming tank, and a surfactant that supplies a surfactant to the foaming tank. When the foaming amount in the foaming tank does not exceed a predetermined value, the addition amount of the surfactant is increased, and when the foaming amount exceeds the predetermined value, the addition amount of the surfactant is increased. It is characterized by comprising a control device for controlling the supply amount of the surfactant so as to decrease, and a membrane module disposed downstream of the foaming tank.

  According to the water treatment apparatus of the present invention, waste water containing oil is introduced into a foaming tank, and the waste water containing oil and the surfactant are mixed in the foaming tank, but the surface activity is based on the amount of foaming in the foaming tank. Since the addition amount of the agent is controlled, the surfactant required for micellizing the oil in the wastewater is supplied almost without excess or deficiency. For this reason, since the oil contained in the waste water is almost completely micelle and emulsified and dispersed, it is possible to prevent the oil from adhering to the membrane and clogging during membrane filtration treatment similar to the membrane module. Further, since the addition amount of the surfactant can be optimized, the drug cost can be reduced.

  The water treatment apparatus of the present invention preferably includes a surfactant injection device that injects a surfactant toward the membrane surface of the membrane module. According to this aspect, the oil component adhering to or near the membrane forms micelles by the reaction with the surfactant injected from the surfactant injection device, so that clogging of the membrane can be efficiently prevented. Furthermore, since the organic substance such as protein is denatured and swelled by the surfactant, it is possible to prevent the solid matter other than oil from adhering to the film.

  The water treatment device of the present invention preferably includes an oil film sensor disposed upstream of the foaming tank. And it is preferable to provide further the bypass line which bypasses the said foaming tank and flows the waste water from which the oil film was not detected with the said oil film sensor. According to this aspect, since the addition of the surfactant to the waste water containing no oil can be prevented, the amount of the surfactant used can be further reduced.

  In the water treatment apparatus of the present invention, it is preferable that the foam detector is configured to detect the foam amount by a method selected from an optical method, an electrical method, and an image method.

  In the water treatment apparatus of the present invention, the surfactant is preferably a biodegradable surfactant. According to this aspect, the influence on the environment to the surroundings can be reduced.

  The water treatment apparatus of the present invention preferably includes an activated sludge treatment tank, and the membrane filtration apparatus is disposed downstream of the activated sludge treatment tank or in the activated sludge treatment tank. According to this aspect, in the activated sludge treatment tank, organic matter and micellized oil can be treated, and cleaner treated water can be obtained.

  According to the present invention, since the addition amount of the surfactant is controlled based on the foaming amount in the foaming tank, the surfactant required for micellization of the oil content in the wastewater can be supplied almost without excess or deficiency. . For this reason, the oil contained in the wastewater can be almost completely micelle, and the oil can be prevented from adhering to the membrane. Further, since the addition amount of the surfactant can be optimized, the drug cost can be reduced.

It is a schematic block diagram of 1st Embodiment of the water treatment apparatus of this invention. It is a control flowchart in the control apparatus of the water treatment apparatus. It is a schematic block diagram of 2nd Embodiment of the water treatment apparatus of this invention. It is a schematic block diagram of 3rd Embodiment of the water treatment apparatus of this invention. It is a control flowchart in the control apparatus of the water treatment apparatus.

  A first embodiment of the water treatment apparatus of the present invention will be described with reference to FIG.

  A pipe L1 extending from the wastewater field is connected to the foaming tank 1.

  A foaming detector 21 and a stirring device 2 are arranged in the foaming tank 1. The foam detector 21 is not particularly limited. An apparatus configured to detect the amount of foaming by a method selected from an optical method, an electrical method, and an image method can be used. Examples of the device that detects the foaming amount by an optical method include a light (laser) level sensor and a gamma ray level sensor. Examples of the device that detects the amount of foaming by an electrical method include a device that detects a change in potential when bubbles come into contact, such as a bubble level detector and a dielectric constant level switch. As an apparatus for detecting the foaming amount by an image technique, an automatic video recognition apparatus such as a camera can be cited. The measurement result of the foam detector 21 is input to the control device 30.

  A pipe L <b> 2 extending from the surfactant storage tank 3 is connected to the upper part of the foaming tank 1. A pump P1 is interposed in the pipe L2. The drive of the pump P1 is controlled by the control device 30. In this embodiment, the surfactant storage tank 3, the pipe L2, and the pump P1 correspond to the “surfactant supply device” in the present invention.

  An activated sludge treatment tank 4 is disposed downstream of the foaming tank 1. The foaming tank 1 and the activated sludge treatment tank 4 are connected via a pipe L3.

  The activated sludge treatment tank 4 is not particularly limited as long as the activated sludge containing microorganisms stays in the tank and the activated sludge treatment can be performed by decomposing organic matter by the action of microorganisms. For example, an aeration tank containing aerobic microorganisms such as ammonia oxidizing bacteria and nitrite oxidizing bacteria, an intermittent aeration tank containing anaerobic microorganisms such as nitrite oxidizing bacteria and anaerobic microorganisms such as denitrifying bacteria can be used. A sludge extraction pipe L4 extends from the lower part of the activated sludge treatment tank.

  In this embodiment, the membrane module 5 is disposed in the activated sludge treatment tank 4 so as to be immersed in the treatment liquid in the tank.

  From the secondary side of the membrane module 5 (the side through which the filtered treated water circulates), a pipe L5 intervening with the pump P2 extends, and the treated water in the tank is converted into a membrane by operating the pump P2. The membrane 5 is subjected to membrane filtration.

  As a filtration membrane used for the membrane module 5, any general filtration membrane can be used. For example, a reverse osmosis (RO) membrane, an ultrafiltration (UF) membrane, a microfiltration (MF) membrane, a hollow fiber (HF) membrane, etc. are mentioned. Examples of the material for the filtration membrane include polyacrylonitrile, polyimide, polyethersulfone, polyphenylene sulfide sulfone, polytetrafluoroethylene, polyvinylidene fluoride, polypropylene, and polyethylene. The form of the membrane module 5 is not particularly limited, and examples thereof include a hollow fiber membrane module, a flat membrane type module, a spiral type module, and a tubular module.

  Below the membrane module 5, an aeration (bubbling) device 6 is arranged, and aeration is performed every predetermined time to prevent the membrane module 5 from being clogged.

  In this embodiment, the membrane module 5 is disposed in the activated sludge treatment tank 4, but may be disposed outside the activated sludge treatment tank 4.

  Next, 1st Embodiment of the water treatment method of this invention is described using the water treatment apparatus shown in FIG. In addition, as wastewater used as the process target of the water treatment method of this invention, what is necessary is just wastewater containing oil, and there is no limitation in particular. For example, factory waste water discharged from a chemical factory or a food factory.

  First, waste water is supplied to the foaming tank 1 and the stirring device 2 is operated to stir the waste water supplied into the tank. Then, the pump P1 is operated to supply a predetermined amount of the surfactant, and the oil content in the wastewater is micellized.

  There is no limitation in particular as surfactant. For example, anionic surfactants such as sodium fatty acid, sodium alkyl sulfate ester, sodium alpha olefin sulfonate, sodium lauryl sulfate, sodium laureth sulfate, sodium cocoyl glutamate, sodium cocoyl methylalanine, disodium lauryl sulfosuccinate, steartrimonium chloride And cationic surfactants such as cetrimonium chloride, amphoteric surfactants such as cocobetaine, sodium lauroamphoacetate, sodium cocoamphoacetate, laurylhydroxysultain, lauramidopropylbetaine, and cocamidopropylbetaine. Among these, biodegradable surfactants such as fatty acid sodium, sodium alkyl sulfate ester, sodium alpha olefin sulfonate and the like are preferably used because they do not accumulate in nature and can reduce the environmental burden.

  The waste water foamed by adding and mixing the surfactant in the foaming tank 1 is supplied to the activated sludge treatment tank 4 to be treated with activated sludge. Then, the treated water after the activated sludge treatment is subjected to membrane filtration treatment by the membrane module 5, and the filtered water is sent to a drainage system, and chlorine and the like are added to drain out of the system. In addition, the sludge that has accumulated at the bottom of the activated sludge treatment tank 4 is periodically extracted from the pipe L3, sent to a sludge treatment system (not shown), and processed by performing a drying process and a dehydrating process.

  Although water treatment is performed in this way, in the present invention, the operation amount of the pump P1 is controlled by the control device 30 as follows to adjust the supply amount of the surfactant.

  Hereinafter, the control in the control device 30 will be described with reference to the flowchart of FIG.

  In step S1, it is determined whether the amount of foam detected by the foam detector 21 is greater than or equal to a threshold value.

  When the foaming amount detected by the foaming detector 21 is less than the lower limit threshold, the surfactant required to completely micelle the oil in the wastewater is insufficient, so in step S2 Then, a command is output to the pump P1 to increase the addition amount of the surfactant, and the process returns to step S1.

  On the other hand, if the amount of foam detected by the foam detector 21 is equal to or greater than the lower limit threshold value, it is next determined in step S3 whether it is equal to or greater than the upper limit threshold value.

  If it is less than the upper limit threshold value, it can be determined that the surfactant required for completely micellizing the oil in the wastewater is supplied almost in excess and deficiency, and the control ends.

  On the other hand, if it is equal to or greater than the upper threshold value, the amount of surfactant added in step S4 is reduced because the surfactant required for complete micellization of the oil in the wastewater is supplied in excess. A command is output to the pump P1 and the control is terminated.

  According to the present invention, since the addition amount of the surfactant is controlled based on the foaming amount in the foaming tank 1, the surfactant required for micellizing the oil content in the wastewater is supplied almost without excess or deficiency. it can. For this reason, the oil contained in the wastewater can be almost completely micelle, and the oil can be prevented from adhering to the membrane of the membrane module 5. Furthermore, when the oil component is micellized and emulsified and dispersed in the wastewater, the oil component is easily treated in the activated sludge treatment tank 4, and the oil component can be more difficult to adhere to the membrane of the membrane module 5. For this reason, the cleaning frequency and replacement frequency of the membrane module 5 can be suppressed. Further, since the addition amount of the surfactant can be optimized, the drug cost can be reduced.

  A second embodiment of the water treatment apparatus of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the location substantially the same as 1st Embodiment, and the description is abbreviate | omitted.

  In the water treatment apparatus of this embodiment, an injection port 7 for injecting a surfactant toward the primary side of the membrane of the membrane module 5 (the side to which filtered water is supplied) is disposed in the activated sludge treatment tank 4. ing. The injection port 7 is connected to a pipe L6 extending from the surfactant storage tank 3 and provided with a pump P3. The timer of the pump P3 is controlled so as to operate intermittently at a predetermined timing in synchronization with the pump P2 or while the pump P2 is operating. In other words, the membrane module 5 is controlled so as to operate continuously or intermittently during the membrane filtration process.

  In this embodiment, the injection port 7, the surfactant storage tank 3, the pipe L6, and the pump P3 correspond to the “surfactant injection device” in the present invention.

  According to this water treatment apparatus, the surfactant is jetted from the jet port 7 toward the primary side of the membrane of the membrane module 5 while the wastewater is being membrane-filtered by the membrane module 5. Since the oil component adhering to the vicinity of the membrane 5 or to the membrane module 5 reacts with the surfactant sprayed toward the membrane surface to form micelles, the clogging of the membrane can be efficiently prevented. Furthermore, since the organic substance such as protein is denatured and swelled by the surfactant, it is possible to prevent the solid matter other than oil from adhering to the film.

  A third embodiment of the water treatment apparatus of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the location substantially the same as 1st, 2nd embodiment, and the description is abbreviate | omitted.

  In this water treatment apparatus, an oil film sensor 22 for detecting an oil film of an oil film of wastewater flowing through the pipe L1a and a switching valve V1 are arranged in a pipe L1a extending from the wastewater source. A pipe L1b connected to the foaming tank 1 and a pipe L7 connected to the activated sludge tank 4 extend from the switching valve V1. The oil film sensor 22 is not particularly limited, and a conventionally known oil film sensor can be used. For example, an oil film detection sensor such as a laser scanning type, an ellipsometric type, or a UV light irradiation type may be used. The measurement result of the oil film sensor 22 is input to the control device 31.

  Hereinafter, the control in the control device 31 will be described with reference to the flowchart of FIG.

  In step S11, it is determined whether an oil film is detected by the oil film sensor 22.

  If no oil film is detected, the connection between the pipe L1a and the pipe L1b is disconnected by the switching valve V1, the pipe L1a and the pipe L7 are connected, and the operation of the pump P3 is completely stopped at step S12. End.

  On the other hand, when the oil film is detected, in step S13, the connection between the pipe L1a and the pipe L7 is disconnected by the switching valve V1, and the pipe L1a and the pipe L1b are connected. Moreover, the pump P3 is started and operated. The pump P3 is controlled by a timer so as to operate intermittently at a predetermined timing in synchronization with the pump P2 or while the pump P2 is operating.

  Next, in step S14, it is determined whether the foam amount detected by the foam detector 21 is equal to or greater than a threshold value.

  If the amount of foam detected by the foam detector 21 is less than the lower limit threshold, the surfactant required to completely micelle the oil in the wastewater is insufficient, so in step S15 Then, a command is output to the pump P1 to increase the addition amount of the surfactant, and the process returns to step S14.

  On the other hand, if the amount of foam detected by the foam detector 21 is equal to or greater than the lower limit threshold value, it is then determined in step S16 whether it is equal to or greater than the upper limit threshold value.

  If it is less than the upper limit threshold value, it can be determined that the surfactant required for completely micellizing the oil in the wastewater is supplied almost in excess and deficiency, and the control ends.

  On the other hand, if the amount is equal to or greater than the upper threshold value, the amount of surfactant added in step S17 is reduced because the surfactant required to completely micelle the oil in the wastewater is supplied. A command is output to the pump P1 and the control is terminated.

  According to the water treatment apparatus of this embodiment, wastewater that does not contain oil can be directly supplied to the activated sludge treatment tank 4 by bypassing the foaming tank, so that the amount of surfactant used can be optimized more efficiently and efficiently. Can treat water.

1: Foaming tank 2: Stirring device 3: Surfactant storage tank 4: Activated sludge treatment tank 5: Membrane module 21: Foam detector 22: Oil film sensor 30, 31: Control devices L1 to L7: Piping P1 to P3: Pump

Claims (12)

A water treatment method for introducing waste water containing oil into a foaming tank, adding and mixing a surfactant to the waste water in the foaming tank, and passing the waste water through a membrane module for membrane filtration,
The amount of foaming in the foaming tank is detected, and when the foaming amount does not exceed a predetermined value, the addition amount of the surfactant is increased, and when the foaming amount exceeds the predetermined value, the surfactant is increased. A water treatment method, wherein the amount of the surfactant added is controlled so as to reduce the amount of the surfactant added.   The water treatment method according to claim 1, wherein the surfactant is sprayed continuously or intermittently toward the membrane surface of the membrane module during the membrane filtration treatment.   The water treatment method according to claim 1 or 2, wherein the foaming amount in the foaming tank is detected by a method selected from an optical method, an electrical method, and an image method.   The water treatment method according to claim 1, wherein a biodegradable surfactant is used as the surfactant.   The water treatment method according to any one of claims 1 to 4, wherein the wastewater that has passed through the foaming tank is introduced into an activated sludge treatment tank and treated with activated sludge, and then subjected to membrane filtration through the membrane module. A foaming tank into which wastewater containing oil is introduced;
A foam detector for detecting the amount of foam in the foaming tank;
A surfactant supply device for supplying a surfactant to the foaming tank;
When the foaming amount in the foaming tank does not exceed a predetermined value, the addition amount of the surfactant is increased, and when the foaming amount exceeds a predetermined value, the addition amount of the surfactant is decreased. A control device for controlling the supply amount of the surfactant;
A water treatment apparatus comprising: a membrane module disposed downstream of the foaming tank.   Furthermore, the water treatment apparatus of Claim 6 provided with the surfactant injection apparatus which injects surfactant toward the film | membrane surface of the said membrane module.   Furthermore, the water treatment apparatus of Claim 6 or 7 provided with the oil film sensor arrange | positioned upstream of the said foaming tank.   Furthermore, the water treatment apparatus of Claim 8 provided with the bypass line which bypasses the said foaming tank and flows the waste water by which the oil film was not detected by the said oil film sensor.   The water treatment according to any one of claims 6 to 9, wherein the foam detector is configured to detect a foam amount by a method selected from an optical method, an electrical method, and an image method. apparatus.   The water treatment apparatus according to any one of claims 6 to 10, wherein the surfactant is a biodegradable surfactant.   Furthermore, the activated sludge processing tank is provided, The said membrane filtration processing apparatus is arrange | positioned in the downstream of this activated sludge processing tank, or in this activated sludge processing tank. Water treatment equipment.