JP2001047089A - Method and apparatus for treating sewage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently utilize ozone and to enhance the quality of treated water while reducing membrane washing cost by performing the injection treatment of ozone between a sedimentation/separation tank and a circulating tank or membrane supply tank to a membrane filter apparatus. SOLUTION: Sewage 1 is allowed to flow in a denitrification tank 2 and circulated between the denitrification tank 2 and a nitrification tank 3 to be subjected to anaerobic nitrification and denitrification treatment and the treated sewage is subjected to solid-liquid separation treatment by a solid-liquid separator 4. The biologically treated water 5 being the separated liquid is transferred to a flocculation tank 7, and an inorg. flocculant 6 is added to the biologically treated water to flocculate an SS component containing phosphate ions and COD. The flocculated liquid is sent to a neutralization tank 9 and an alkali agent 8 is added to this liquid to precipitate the non-flocculated inorg. flocculant as hydroxide. Further, the flocculated liquid is separated into sedimented sludge and a supernatant liquid 11 in a sedimentation and separation tank 10 and ozone 12 is injected in the supernatant liquid 11 from an ozone generator 13 and water to be treated in which ozone is dissolved is sent to a circulating tank 14 and subsequently supplied to a membrane filter apparatus 17 from the circulating tank 14 to be subjected to solid-liquid separation treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating human wastewater, such as human waste, septic tank sludge, leachate from refuse landfills, and mixtures thereof.
The present invention relates to a wastewater treatment method and a wastewater treatment apparatus suitable for removing a D component, a chromaticity component, and the like.

[0002]

2. Description of the Related Art In recent years, a technique called a membrane separation type high-load denitrification treatment method (for example, Japanese Patent Publication No. 7-20583) is sometimes used as a treatment method for wastewater such as human waste or septic tank sludge. FIG. 6 shows a general processing flow in a membrane separation type high load denitrification processing process. The processing flow will be described with reference to FIG.

The wastewater treatment apparatus shown in FIG. 6 includes a biological nitrification denitrification treatment apparatus comprising a denitrification tank 2 and a nitrification tank 3, a membrane filtration apparatus 25, a coagulation tank 7, a sedimentation separation tank 10, a neutralization tank 9, It comprises a circulation tank 14, a membrane filtration device 17, and an activated carbon adsorption tower 20. First, the sewage 1 flows into the denitrification tank 2 without dilution or diluted at an appropriate dilution ratio, and circulates between the denitrification tank 2 and the nitrification tank 3 to anaerobically nitrify and denitrify. Is done. The wastewater subjected to the nitrification and denitrification treatment is subjected to solid-liquid separation by the membrane filtration device 25, and the biological treatment water 5 is transferred to the coagulation tank 7. In a coagulation tank 7, an inorganic coagulant 6 such as aluminum sulfate, ferric chloride or polyiron and an alkaline agent 8 such as sodium hydroxide or potassium hydroxide are added to the biologically treated water 5 to adjust the pH to 3. Under acidic conditions of ~ 5, phosphate ion and C
The SS component containing OD is aggregated. The flocculated floc is separated into settled sludge and supernatant in a settling tank 10, and the supernatant is sent to a neutralization tank 9. On the other hand, the settled sludge is transferred to a sludge treatment step (not shown), and is incinerated after dehydration treatment.

[0004] In the neutralization tank 9, an alkaline agent 8 such as sodium hydroxide or potassium hydroxide is added to neutralize the solution to a pH of 6 to 8, so that unagglomerated particles contained in the supernatant are removed. The inorganic coagulant is precipitated as a hydroxide. The neutralized treated water 26 is transferred to the circulation tank 14 and supplied from the circulation tank 14 to the membrane filtration device 17 to be separated into solid and liquid. The membrane filtered water 18 obtained here is transferred to an activated carbon adsorption tower 20 filled with activated carbon, and adsorbs and removes COD components and chromaticity components. The treated water is discharged out of the system as discharge water 21.

[0005]

The above-mentioned conventional membrane separation type high-load denitrification process has the following problems.

In the neutralization tank 9, the precipitated hydroxide is supplied to the membrane filtration device 17, so that the load on the membrane filtration device 17 increases and the membrane is easily clogged.

[0007] Since a large amount of organic substances such as the hardly decomposable COD component and the chromaticity component remain in the sewage supplied to the membrane filtration device 17, the membrane derived from the organic substance in the membrane filtration device 17. The fouling phenomenon described above is observed, and there is a drawback that clogging occurs in a relatively short time. In order to eliminate the clogging, chemical cleaning with acid or alkali must be frequently performed. Therefore, there is a problem that the cost and labor for the chemical cleaning operation are increased, leading to an increase in cost.

When the COD of the effluent water obtained by treatment in the activated carbon adsorption tower 20 exceeds the effluent water quality standard, which is usually 10 to 15 mg / L or less, the activated carbon must be regenerated and the frequency of regeneration is reduced. In many cases, maintenance is complicated and the processing cost is expensive.

The present invention has been completed as a result of intensive studies in order to overcome the above-mentioned problems. The present invention improves the quality of treated water by efficiently using ozone, and increases the cost of membrane cleaning. It is an object of the present invention to provide a wastewater treatment method for reducing wastewater and a treatment apparatus to which the method can be efficiently applied.

[0010]

According to the present invention, waste water is subjected to a biological nitrification denitrification treatment comprising a denitrification tank and a nitrification tank, followed by a solid-liquid separation treatment. A coagulant is added to the separated liquid to cause a reaction under acidic conditions, an alkali agent is added to perform a neutralization treatment, and the neutralized liquid is subjected to sedimentation separation in a sedimentation separation tank. In a method for treating sewage in which a supernatant liquid obtained is subjected to a solid-liquid separation treatment by a membrane filtration device, an ozone injection treatment is performed between a sedimentation separation tank and a circulation tank or a membrane supply tank to the membrane filtration device. It is a method of treating sewage which is a feature.

In the present invention, an ozone contact tank may be further provided after the membrane filtration device, the filtered water from the membrane filtration device may be supplied to the ozone contact tank, and ozone may be re-injected into the ozone contact tank. And a wastewater treatment method.

[0012] The present invention is also a method for treating wastewater, wherein the membrane used in the membrane filtration device is a microfiltration membrane or an ultrafiltration membrane.

The present invention is also a carrier-based nitrification tank in which the nitrification tank in the biological nitrification denitrification treatment contains a microorganism-immobilized carrier, and fluidizes the carrier with aerated air to perform the nitrification treatment. This is a method for treating wastewater.

In this configuration, the carrier for immobilizing microorganisms is charged into the nitrification tank, and the carrier is held in the nitrification tank.
Microorganisms including nitrifying bacteria adhere to the surface of the microorganism-immobilized carrier.
It grows and exhibits a purifying function. As a result, even when the amount and biota of suspended sludge fluctuate due to the change in water quality of sewage, nitrifying bacteria are stably retained in the nitrification tank, and a stable biological treatment effect, particularly a nitrification treatment effect, is obtained. . Fluidizing the microorganism-immobilized carrier with aerated air can increase the chance of contact between microorganisms attached to and growing on the carrier and pollutants such as ammonia and oxygen, so that the microorganism-immobilized carrier is used in a fixed bed. Unlike the above, there is no problem that solid matter is trapped in the gap between the carriers to cause water flow resistance.

Further, in the present invention, the microorganism-immobilized carrier comprises a plastic such as polyethylene or polypropylene as a main component, a specific gravity of 1.00 to 1.10, and a particle size of 1.0 to 15. 2.0 m.

Further, according to the present invention, an ozone injection amount is controlled by an ozone detector installed at a membrane filtration outlet of a membrane filtration device such that a residual ozone concentration in the membrane filtration water is within a range of 0.01 to 10 mg / L. Is a method for treating wastewater.

Further, in the present invention, the ozone injection amount is adjusted by continuously measuring the residual ozone concentration of the membrane filtration water by an ozone detector installed at a membrane filtration outlet of the membrane filtration device. The residual ozone concentration is 0.01 to 10 mg /
L, within the range of L, based on the measured value of the residual ozone concentration, feedback control of the ozone injection amount, the wastewater treatment method characterized by adjusting the residual ozone concentration within the range is there.

Further, the present invention is a method for treating sewage, wherein ozone is directly injected in-line into a pipe connecting the sedimentation separation tank with a circulation tank or a membrane supply tank of a membrane filtration device.

Furthermore, the present invention is a method for treating wastewater, which comprises injecting ozone into a circulation tank or a membrane supply tank of a membrane filtration device.

Further, the present invention is characterized in that an ozone dissolving tank is installed between the sedimentation separation tank and the circulation tank or the membrane supply tank of the membrane filtration device, and ozone is injected into the ozone dissolving tank. It is a method of treating sewage.

[0021] Further, the present invention provides a biological nitrification denitrification process comprising a denitrification tank and a nitrification tank, and then performs a solid-liquid separation treatment on the wastewater. On the other hand, a coagulant was added and reacted under acidic conditions, an alkali agent was added to perform a neutralization treatment, and the neutralized liquid was subjected to sedimentation separation in a sedimentation separation tank, and then the obtained supernatant was obtained. In a method for treating wastewater in which a liquid is subjected to a solid-liquid separation treatment by a membrane filtration device, an ozone injection device for injecting ozone in the middle of a sedimentation separation tank and a circulation tank or a membrane supply tank to the membrane filtration device, and a membrane filtration device An ozone detector installed at the membrane filtration outlet for measuring the residual ozone concentration in the membrane filtration water, and measuring the residual ozone concentration in the membrane filtration water with the ozone detector, and operating the ozone injection equipment based on the measured value. And then inject ozone Adjust a sewage treatment apparatus, which comprises deploying a control means for the residual ozone concentration in the membrane filtration water within a predetermined range.

Further, the present invention is the sewage treatment apparatus characterized in that an ozone contact tank is further provided after the membrane filtration apparatus in order to further ozone-treat the filtered water from the membrane filtration apparatus.

Further, in the present invention, the nitrification tank in the biological nitrification and denitrification treatment is a carrier-utilization nitrification tank in which a microorganism-immobilized carrier is present and which is flown by aerated air to nitrify sewage. A wastewater treatment apparatus characterized by the following.

[0024]

FIG. 1 shows an example of a sewage treatment apparatus according to the present invention.

As shown in FIG. 1, the method and apparatus for treating wastewater according to the present invention include a biological nitrification denitrification treatment apparatus comprising a denitrification tank 2 and a nitrification tank 3, a solid-liquid separation apparatus 4,
It comprises a coagulation tank 7, a neutralization tank 9, a sedimentation separation tank 10, a circulation tank 14, a membrane filtration device 17, an ozone generator 13, an exhausted ozone gas treatment facility 16, an ozone detector 19, and an activated carbon adsorption tower 20. First, the sewage 1 flows into the denitrification tank 2 without dilution or diluted at an appropriate dilution ratio, and circulates between the denitrification tank 2 and the nitrification tank 3 to anaerobically nitrify and denitrify. Is done. The sewage that has been subjected to nitrification and denitrification is subjected to solid-liquid separation by a solid-liquid separation device 4.
The biologically treated water 5, which is a separated liquid obtained by the above, is transferred to the flocculation tank 7. In the coagulation tank 7, an inorganic coagulant 6 such as aluminum sulfate, ferric chloride or polyiron is added to the biologically treated water 5, and under the acidic condition of pH 3 to 5, the SS containing phosphate ions and COD is added. Aggregate the fractions. The coagulation liquid is sent to a neutralization tank 9, where an alkaline agent 8 such as sodium hydroxide or potassium hydroxide is added to neutralize the pH to 6 to 8, and the inorganic coagulation is performed. The agent is precipitated as a hydroxide. Further, the sedimentation sludge is separated into the supernatant liquid 11 and the sedimentation sludge in the sedimentation separation tank 10, and the sedimentation sludge is transferred to a sludge treatment step (not shown), dehydrated and discharged out of the system as a dewatered cake. Processing such as incineration or methane fermentation / composting is performed. On the other hand, the supernatant 11 contains an ozone generator 13.
Ozone 12 is directly injected in-line, and the water to be treated in which ozone is dissolved is sent to the circulation tank 14. The water to be treated is supplied from the circulation tank 14 to the membrane filtration device 17 to be separated into solid and liquid. Membrane filtration water 1 that has passed through membrane filtration device 17
8 is transferred to an activated carbon adsorption tower 20 filled with activated carbon,
Contaminants are removed by adsorption. Thereafter, the treated water from which the pollutants have been removed is discharged out of the system as discharge water 21.

In the process in which the membrane filtered water 18 is fed into the activated carbon adsorption tower 20, the ozone concentration remaining in the membrane filtered water is detected by the ozone detector 19, and based on the measured value of the ozone concentration, the ozone generator 13 is detected. Is controlled. Further, the exhausted ozone gas 15 discharged from the circulation tank 14 is processed by the exhausted ozone gas processing equipment 16.
The circulating water from the membrane filtration device 17 is returned to the circulation tank 14 through a circulation line. Furthermore, the same applies to the following embodiments, but the ozone detector 19 may be a dissolved ozone concentration detector.

In this embodiment, the concentration of residual ozone in the membrane filtered water is constantly measured by the ozone detector 19, and the ozone generation is controlled so that the residual ozone concentration is in the range of 0.01 to 10 mg / L. The amount of ozone injected directly in-line from the device 13 is adjusted by the applied voltage of the ozone generator, the opening and closing operation of the valve, and the like. For example, C
The control unit such as a PU (central processing unit) calculates the residual ozone concentration in the membrane filtration water, and performs feedback control of the ozone injection amount injected in-line.

Another embodiment of the sewage treatment apparatus according to the present invention is shown in FIG.

As shown in FIG. 2, in this embodiment,
The microorganism-immobilized carrier 22 is contained in the nitrification tank 3, and the ozone 12 from the ozone generator 13 is not injected into the water to be treated fed into the circulation tank 14,
And an ozone oxidation reaction is performed in the circulation tank 14. Otherwise, it is the same as the embodiment of FIG.

Another embodiment of the sewage treatment apparatus according to the present invention is shown in FIG.

In the embodiment shown in FIG. 3, an alkali agent 8 is injected in-line into the coagulation liquid from the coagulation tank 7 and introduced into the sedimentation tank 10. In addition, sedimentation separation tank 1
An ozone dissolving tank 23 is provided between 0 and the circulation tank 14, and ozone 12 from the ozone generator 13 is injected into the ozone dissolving tank 23. Otherwise, it is the same as the embodiment shown in FIG. That is, the steps up to the settling tank 10 are performed in the same manner as described with reference to FIG.
Is supplied to the ozone dissolving tank 23. Further, ozone 12 is injected from the ozone generator 13 into the ozone dissolving tank 23, and the treated water in which ozone is dissolved is sent to the circulation tank 14. The circulation tank 14 supplies the ozone-dissolved treated water to the membrane filtration device 17. The membrane filtered water 18 that has passed through the membrane filtration device 17 is transferred to an activated carbon adsorption tower 20 filled with activated carbon, and the treated water is discharged out of the system as effluent water 21. In the process of feeding the membrane filtered water 18 into the activated carbon adsorption tower 20, the ozone concentration remaining in the membrane filtered water is detected by the ozone detector 19, and based on the measured value of the ozone concentration, the ozone generator 13 sends the ozone dissolving tank 23 The amount of ozone supplied to is controlled. In addition, the ozone dissolving tank 2
The exhausted ozone gas 24 discharged from 3 and the exhausted ozone gas 15 from the circulation tank 14 are processed in an exhausted ozone gas treatment facility 16. The circulating water from the membrane filtration device 17 is returned to the circulation tank 14 through a circulation line.

Next, the solid-liquid separation device 4 according to the present invention will be described. The purpose of the solid-liquid separator 4 is to separate the activated sludge from the biologically nitrified and denitrified sewage and maintain the MLSS concentration in the system in the denitrification tank 2 and the nitrification tank 3 at a high level. As a device used in the solid-liquid separation device 4, any device having a solid-liquid separation function such as membrane filtration, gravity sedimentation, centrifugal separation, filter cloth filtration may be used without any problem. Alternatively, there is no problem whether the apparatus is of a device installation type. For example, in the case of the immersion type in a tank, it may be installed in the nitrification tank 3 and the film surface is washed by aerated air, which is convenient. When using a membrane filtration device,
The membrane used is a membrane capable of removing turbid components and the like, and a microfiltration membrane or an ultrafiltration membrane is used.
Further, the type of the membrane module may be any type such as a hollow fiber shape, a spiral shape, a tubular shape, and a flat membrane shape. Further, the filtration method of the membrane module includes a total filtration method and a cross-flow filtration method, and any filtration method may be used. In addition, there are an external pressure type and an internal pressure type as a water passing method to the membrane filtration device, and there is no problem in either water passing method.

Next, the microorganism-immobilized carrier 22 used in the nitrification tank 3 will be described. Microorganism-immobilized carrier 22
As the material, a material mainly composed of a plastic stable to a biochemical reaction such as polyethylene and polypropylene is used. The specific gravity of the microorganism-immobilized carrier is 1.00 to 1.
10, a diameter of 1.0 to 15.0 mm is used. When the specific gravity of the microorganism-immobilized carrier is less than 1.00, the specific gravity of the sewage is lower than that of the wastewater, so that the microorganism-immobilized carrier easily floats to form a floating layer, and is difficult to be fluidized by aerated air. As a result, the efficiency of contact between the microorganism-immobilized carrier and the liquid in the nitrification tank and oxygen decreases, and the treatment efficiency decreases. On the other hand, when the specific gravity exceeds 1.10, the sedimentation speed of the microorganism-immobilized carrier becomes large, so that it is easy to deposit in the nitrification tank, and it is difficult to fluidize the carrier.
The contact efficiency between the microorganism-immobilized carrier and the liquid in the nitrification tank and oxygen is deteriorated, and the treatment efficiency is reduced. Therefore, the specific gravity of the microorganism-immobilized carrier is preferably in the above range. When the particle diameter of the microorganism-immobilized carrier is less than 1.0 mm, the mesh width of the separation screen for the microorganism-immobilized carrier is less than 1.0 mm, and impurities such as impurities contained in the sewage introduced into the nitrification tank are removed. This is not preferable because clogging of the screen is likely to occur. In the case of the microorganism-immobilized carrier, the specific surface area (surface area /
A larger volume is economically preferable, but when the particle size of the carrier exceeds 15.0 mm, there is a disadvantage that the specific surface area of the carrier is reduced. Since the volume of the material of the microorganism-immobilized carrier, that is, the weight of the carrier is proportional to the production cost, an increase in the weight means an increase in the production cost of the carrier, which is not economical. Therefore, the particle size of the microorganism-immobilized carrier is preferably set within the above range. Also,
As the shape of the microorganism-immobilized carrier, various shapes such as a columnar shape and a spherical shape can be used, but the effective portion of the biofilm that adheres to and grows on the microorganism-immobilized carrier is generally 0.1%.
mm. Therefore, the microorganism-immobilized hedge is preferably in a shape having a large specific surface area, and is preferably formed in a hollow cylindrical shape because the specific surface area can be increased. Further, there is no problem even if a screen having openings larger than the particle diameter of the microorganism-immobilized carrier is provided as a means for separating the microorganism-immobilized carrier and the nitrification treatment solution in the nitrification tank 3.

Next, the ozone dissolving tank 23 of the present invention will be described. The purpose of the ozone dissolving tank 23 is to dissolve ozone in the membrane supply water in order to keep the filtration speed of the membrane filtration device 17 high. The ozone 12 is injected from the ozone generator 13 into the ozone dissolving tank 23. At that time, the amount of residual ozone remaining in the membrane filtration water 18 obtained by the membrane filtration device 17 depends on the filtration rate of the membrane filtration device 17. In order to maintain a high level, the content is set to 0.01 to 10 mg / L, preferably 0.1 to 3 mg / L. When the residual ozone concentration in the membrane filtration water is higher than 10 mg / L, even if an ozone-resistant membrane material is used as the filtration membrane of the membrane filtration device 17, membrane degradation may occur in the long term due to reaction with ozone. There is. However, considering the replacement time of the membrane module, up to 10 mg / L is permissible. Further, when the residual ozone concentration exceeds 10 mg / L, there is a problem that the amount of by-products also increases. From the above, the residual ozone concentration in the membrane filtration water is 0.01 to 10 mg / L,
Desirably, it is good to be 0.1 to 3 mg / L. Also,
The device type of the ozone dissolving tank 23 can be any type such as a U-tube type, a diffuser type, an injector type, an ejector type, and a downward injection type injection. Further, the exhausted ozone gas discharged from the ozone dissolving tank 23 or the circulation tank 14 is introduced into the exhausted ozone gas processing equipment 16 and processed. The type of the exhaust ozone gas treatment equipment 16 may be any type such as an activated carbon type, a pyrolysis type, and a catalytic type.

Next, the membrane filtration device 17 according to the present invention will be described. This membrane filtration device performs membrane filtration in a state in which ozone is dissolved in the membrane supply water, so that membrane filtration is always performed in a state where pretreatment with ozone is performed, thereby preventing membrane clogging due to biological fouling. It is possible,
And a high permeation flux can be obtained. The membrane used is a membrane capable of removing turbid components and bacteria, and a microfiltration membrane or an ultrafiltration membrane is used. In the case of a microfiltration membrane, one having a nominal pore size of 0.01 to 0.5 μm is used, and in the case of an ultrafiltration membrane, the molecular weight cut-off is 1,0.
Those having a molecular weight of 00 to 200,000 daltons are used. As the type of the membrane module, a hollow fiber shape, a spiral shape, a tubular shape, or a flat membrane shape is used. It is desirable to use an ozone-resistant material for the film material and the potting portion in order to come into contact with high-concentration ozone. As the film material, an ozone-resistant organic resin such as a vinylidene fluoride polymer resin or an inorganic material such as a ceramic can be used. Further, the filtration method of the membrane module includes a total filtration method and a cross-flow filtration method, and any filtration method may be used. In addition, there are an external pressure type and an internal pressure type as a water flow system for the membrane filtration, and there is no problem with either water flow system.

Next, ozone injection control in the present invention will be described. In the present embodiment, a method of measuring the concentration of residual ozone in the membrane filtered water with the ozone detector 19 and operating the ozone generator 13 to control the ozone injection amount can be used. Ozone 1 generated by the ozone generator 13
2 is supplied directly to the piping by in-line injection or supplied to the circulation tank 14 or the ozone dissolving tank 23. The voltage applied to the ozone generator and valves provided on each supply pipe (not shown)
It can be adjusted by adjusting the opening degree. In the ozone concentration injection control, the ozone concentration of the membrane supply water may be set as a control target value. However, in this case, even if the membrane filtration is performed for a short time, ozone may be consumed by the reaction between the clogging substance on the membrane surface and the ozone, and it is necessary to consider this in advance. Therefore, it is preferable that the residual ozone concentration in the membrane filtration water be the control target value.

The ozone injection rate is determined by feedback based on the residual ozone concentration in the membrane filtered water.
When the required amount of ozone in the supernatant obtained in the sedimentation tank 10 fluctuates, the residual ozone concentration in the membrane filtered water is measured by a dissolved ozone concentration detector, and the ozone inflow rate is feedback-controlled. You can also. Of course, the ozone detector 19 may detect using the CPU (central processing unit).

In the present invention, in addition to the above embodiment,
An embodiment is also possible in which an ozone contact tank is further provided after the membrane filtration device 17, filtered water from the membrane filtration device is supplied to the ozone contact tank, and ozone is re-injected into the ozone contact tank for treatment. Hereinafter, this aspect will be described.

In the embodiment shown in FIG. 4, the wastewater treatment apparatus according to the present invention is a biological nitrification denitrification treatment apparatus comprising a denitrification tank 2 and a nitrification tank 3, a solid-liquid separation apparatus 4,
Coagulation tank 7, neutralization tank 9, sedimentation separation tank 10, circulation tank 14, membrane filtration device 17, ozone contact tank 30, ozone generator 13,
It comprises an exhausted ozone gas treatment facility 16, an ozone detector 19, and an activated carbon adsorption tower 20. That is, it differs from the embodiment of FIG. 1 in that an ozone contact tank 30 is added.

First, the sewage 1 flows into the denitrification tank 2 without dilution or after being diluted to an appropriate dilution ratio.
It is circulated between the denitrification tank 2 and the nitrification tank 3 to perform anaerobic nitrification denitrification. The sewage that has been subjected to nitrification and denitrification is subjected to solid-liquid separation by a solid-liquid separator 4, and the biologically treated water 5 is collected in a coagulation
Is transferred to In the coagulation tank 7, an inorganic coagulant 6 such as aluminum sulfate, ferric chloride, or polyiron is added to the biologically treated water 5 to form an SS containing phosphate ions and COD under acidic conditions of pH 3 to 5. Aggregate the fractions. The coagulation liquid is sent to a neutralization tank 9, where an alkaline agent 8 such as sodium hydroxide or potassium hydroxide is added to neutralize the pH to 6 to 8, and the inorganic coagulation is performed. The agent is precipitated as a hydroxide. Further, the sediment sludge and the supernatant liquid 11 are separated in the sedimentation separation tank 10,
The settled sludge is transferred to a sludge treatment step (not shown), dewatered and discharged as a dewatered cake outside the system, and then subjected to further incineration treatment or methane fermentation / composting. On the other hand, the supernatant 11 contains the ozone generator 1
Ozone 12 is directly injected in-line from 3, and the water to be treated in which ozone is dissolved is sent to the circulation tank 14. This water to be treated is supplied from the circulation tank 14 to the membrane filtration device 17,
The membrane filtered water 18 that has passed through the membrane filtration device 17 is sent to the ozone contact tank 30. A required amount of ozone 31 is supplied from the ozone generator 13 to the ozone contact tank 30, and the membrane filtered water 18 and the ozone 31 are in contact with each other. Membrane filtered water 18
In the process of being sent from the membrane filtration device 17 to the ozone contact tank 30, the residual ozone concentration in the membrane filtration water is detected by the ozone detector 19, and based on the measured value of the ozone concentration, direct in-line injection is performed from the ozone generator 13. Ozone 1
2 is controlled. The ozone-treated water 33 that has sufficiently contacted the ozone in the ozone contact tank 30 is transferred to the activated carbon adsorption tower 20 filled with activated carbon, and the treated water is discharged out of the system as discharge water 21. Further, the exhausted ozone gas 15 discharged from the circulation tank 14 and the exhausted ozone gas 32 discharged from the ozone contact tank 30 are processed by the exhausted ozone gas processing equipment 16. The circulating water from the membrane filtration device 17 is returned to the circulation tank 14 through a circulation line. Although the same applies to the following embodiments, the ozone detector 19 may be a dissolved ozone concentration detector.

In the present embodiment, the concentration of residual ozone in the membrane filtered water is constantly measured by the ozone detector 19, and the ozone generation is controlled so that the residual ozone concentration is in the range of 0.01 to 10 mg / L. The amount of ozone injected directly in-line from the device 13 is adjusted by the applied voltage of the ozone generator, the opening and closing operation of the valve, and the like. For example, C
The residual ozone concentration in the membrane filtration water is calculated by control means such as a PU (central processing unit), and the amount of ozone injected in-line is feedback-controlled.

Another embodiment of the sewage treatment apparatus according to the present invention is shown in FIG.

As shown in FIG. 5, in the method and apparatus for treating wastewater in this embodiment, a microorganism-immobilized carrier 22 is provided in the nitrification tank 3 as in the embodiment shown in FIG. Further, the ozone 12 from the ozone generator 13 is
The ozone oxidation reaction is performed in the circulation tank 14 instead of being injected into the water to be treated sent to the circulation tank 14 as in the embodiment. Otherwise, it is the same as the embodiment of FIG.

The solid-liquid separation device 4 and the membrane filtration device 17 according to the present invention are as already described in the example of FIG.

Next, the injection control of ozone in the present invention will be described. In the present embodiment, a method is used in which the ozone detector 19 measures the residual ozone concentration in the membrane filtered water, and controls the ozone injection amount by operating the ozone generator 13. The ozone 12 generated by the ozone generator 13 is directly in-line injected into a pipe or supplied to the circulation tank 14, and the ozone gas 31 generated by the ozone generator 13
Is supplied to the ozone contact tank 30, and the amount thereof can be adjusted by adjusting the applied voltage of the ozone generator and the opening of valves (not shown) provided in each supply pipe. In the ozone concentration injection control, the ozone concentration of the membrane supply water may be set as the control target value. In this case, even if the ozone is reacted with the clogging substance on the membrane surface even in a short time in membrane filtration, the ozone is consumed. Therefore, it is necessary to consider this in advance. Therefore, it is preferable to set the residual ozone concentration in the membrane filtration water as the control target value.

The ozone injection rate is determined by feedback based on the residual ozone concentration in the membrane filtered water.
When the required amount of ozone in the supernatant obtained in the sedimentation tank 10 fluctuates, the residual ozone concentration in the membrane filtered water is measured by the dissolved ozone concentration detector, and the ozone injection rate is feedback-controlled. You can also. Of course, the ozone detector 19 may use a CPU (Central Processing Unit) provided with a calculation unit and the like.

Next, the embodiment ozone contact tank 30 shown in FIGS. 4 and 5 will be described. In these embodiments, an ozone contact tank 30 is further provided downstream of the membrane filtration device 17. By providing the ozone contact tank 30 at the subsequent stage of such a membrane filtration device, the amount of ozone injected into the ozone contact tank can be adjusted according to the residual ozone concentration in the membrane filtration water, and the ozone treatment of organic substances can be performed. It is possible to do enough. The purpose of the ozone contact tank 30 provided at the latter stage of the membrane filtration device 17 is to secure a contact time necessary for an ozone reaction with an organic substance, to re-inject ozone, and to replenish ozone required for an ozone reaction. The object of the present invention is to prevent the intermittent operation of the ozone generator or waste of generated ozone by switching the ozone injection line to only the ozone contact tank at the subsequent stage at the time of physical cleaning of the film. Also,
The device type of the ozone contact tank 30 can be any type such as a U-tube type, a diffuser type, an injector type, and a downward injection type injection. However, since ozone is dissolved in the membrane filtered water into which ozone has been injected, it is not necessary to dissolve high-concentration ozone. The device type is preferably a diffuser type capable of ensuring a sufficient contact time.
Since the exhausted ozone gas is also generated in the ozone contact tank 30, the exhausted ozone gas is introduced into the exhausted ozone gas treatment equipment 16 and is treated. The type of the exhaust ozone gas treatment equipment 16 may be any type such as an activated carbon type, a pyrolysis type, and a catalytic type.

[0048]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a wastewater treatment method and treatment apparatus according to the present invention will be described below. The following examples do not limit the present invention.

(Example 1) In the conventional method shown in FIG.
In the experimental device based on (100 L / day),
In the part of the filtration device 25, the molecular weight cut off is 20,000 daltons.
Polyacrylonitrile polymer ultrafiltration membrane (total area
0.2m²Flat membrane, set flux 0.5m ³/ M²/
), And a molecular weight cutoff of 1
3,000 dalton polyacrylonitrile polymer limit
External filtration membrane (total area 0.1m²Hollow fiber membrane, setting flack
1.0m³/ M²/ Day) to apply human waste and cleansing
An experiment on the treatment of a mixed solution of tank sludge was performed.

Starting from the operation up to the ultrafiltration flat membrane 25 in the conventional method shown in FIG. 6, after the acclimatization period of about one month and the biological treatment process is stabilized, The operation experiment up to the ultrafiltration hollow fiber membrane 17 was started. 550m of polyiron in coagulant 7 in iron conversion
g / L and adjusted to pH 4.5 using sodium hydroxide. In the neutralization tank 9, the treatment was performed by adjusting the pH to 7.2 using sodium hydroxide. The water quality data for each of the main steps in this experiment were as shown in Table 1.

[0051]

[Table 1]

Here, the sewage 1 is a mixed liquid after removing night soil and sludge from a septic tank with a fine screen having an opening of about 1 mm. However, three weeks after the start of the flow of water through the ultrafiltration hollow fiber membrane 17, the transmembrane pressure of the membrane becomes 150k.
Since the pressure exceeded Pa, the flow of water through the membrane was interrupted, and the membrane was subjected to chemical cleaning with a sodium hypochlorite and citric acid solution. Although a series of experiments was started again using the ultrafiltration hollow fiber membrane 17 after the chemical cleaning, the transmembrane pressure exceeded 150 kPa three weeks after water flow was resumed.

Therefore, the experimental apparatus was modified to a flow as shown in FIG. Here, a polyacrylonitrile polymer type ultrafiltration membrane having a cut-off molecular weight of 20,000 daltons (flat membrane setting flux having a total area of 0.2 m ² , 0.5 m ³ / m ² / ) Is applied to the membrane filtration device 17 and a nominal pore size of 0.
1 μm vinylidene fluoride polymer resin microfiltration membrane (hollow fiber membrane with a total area of 0.03 m ² , set flux 3.3 m
³ / m ² / day). Starting from the operation up to the solid-liquid separation device 4, after a period of acclimatization of about one month, the biological treatment process is stabilized, and thereafter, the operation experiment up to the coagulation sedimentation device and the microfiltration hollow fiber membrane 17 is performed. Started. In the coagulation tank 7, 500 mg / L of polyiron was added in terms of iron,
The pH was adjusted to 5.0. In the neutralization tank 9, the pH was adjusted to 7.0 with sodium hydroxide for treatment. Ozone 12 was injected into the supernatant 11 obtained in the settling tank by an ejector method so that the residual ozone concentration in the membrane filtration water was 0.1 to 3 mg / L, and membrane filtration was performed. . As a result of a series of water-passing experiments, the transmembrane pressure in the microfiltration hollow fiber membrane 17 exceeded 100 kPa 8 months after the start of water passage, and by using the method and apparatus of the present invention. It has been found that the frequency of chemical cleaning of the microfiltration hollow fiber membrane 17 can be greatly reduced. In addition, the water quality data of each main process during this experimental period is as shown in Table 2.

[0054]

[Table 2]

Although there was no significant difference in the water quality of the sewage compared with the water quality data (Table 1) in the experiment using the conventional method and apparatus, the membrane filtration using the method and apparatus of the present invention was not performed. The COD and chromaticity of the water are lower than the COD and chromaticity of the membrane filtration water using the conventional method and apparatus, and the COD component and color contained in the biologically treated water by the method and apparatus of the present invention. It was found that the degree component was well treated.

(Embodiment 2) In the conventional method shown in FIG.
In the experimental device based on (100 L / day),
In the part of the filtration device 25, the molecular weight cut off is 20,000 daltons.
Polyacrylonitrile polymer microfiltration membrane (total area
0.2m²Flat membrane, set flux 0.5m ³/ M²/
), And a molecular weight cutoff of 1
3,000 dalton polyacrylonitrile polymer limit
External filtration membrane (total area 0.1m²Hollow fiber membrane, setting flack
1.0m³/ M²/ Day) to apply human waste and cleansing
An experiment on the treatment of a mixed solution of tank sludge was performed.

Starting from the operation up to the ultrafiltration flat membrane 25 in the conventional method shown in FIG. 6, after the acclimatization period of about one month, and the biological treatment process is stabilized, The operation experiment up to the ultrafiltration hollow fiber membrane 17 was started. In the coagulation tank 7, the poly iron is 650m in iron conversion
g / L, and the pH was adjusted to 4.3 using sodium hydroxide. In the neutralization tank 9, the pH was adjusted to 7.0 with sodium hydroxide for treatment. The water quality data for each of the main steps in this experiment were as shown in Table 3.

[0058]

[Table 3]

Here, the sewage 1 is a mixed solution obtained by removing human waste and sludge from the septic tank with a fine screen having an opening of about 1 mm. However, three weeks after the start of water flow through the ultrafiltration hollow fiber membrane 17, the transmembrane pressure of the membrane becomes 150 kP.
Since a exceeded a, the flow of water through the membrane was interrupted, and the membrane was subjected to chemical cleaning with a sodium hypochlorite and citric acid solution. Ultrafiltration hollow fiber membrane 1 after chemical cleaning
7, a series of experiments was started again, but the transmembrane pressure exceeded 150 kPa three weeks after water flow was resumed.

Therefore, the experimental apparatus was modified to a flow as shown in FIG. Here, the microorganism-immobilized carrier 2
2 as a hollow cylindrical polypropylene carrier (specific gravity: 1.
04, particle size: inner diameter 3 mm × outer diameter 4 mm × length 5 mm) was filled in the nitrification tank 3 at an apparent volume ratio of 30%. Further, the molecular weight cut-off of 20,000 is provided in the portion of the solid-liquid separation device 4.
Dalton polyacrylonitrile polymer ultrafiltration membrane (flat membrane with a total area of 0.2 m ² , set flux 0.5 m ³
/ M ² / day), and a microfiltration membrane made of a vinylidene fluoride polymer resin having a nominal pore diameter of 0.1 μm (a hollow fiber membrane having a total area of 0.03 m ² , a set flux of 3 μm) was applied to the membrane filtration device 17. 3 m ³ / m ² / day). Starting from the operation up to the solid-liquid separation device 4, after a period of acclimatization of about one month, the biological treatment process is stabilized, and thereafter, the operation experiment up to the coagulation sedimentation device and the microfiltration hollow fiber membrane 17 is performed. Started. 520 mg / L of polyiron in the coagulation tank 7 in terms of iron
And adjusted to pH 4.8. In the neutralization tank 9, the pH was adjusted to 6.8 with sodium hydroxide for treatment. The convection time in the circulation tank 14 of the diffuser type is set to 6 minutes, and the residual ozone concentration in the membrane filtration water is 0.1 to
Ozone was injected into the circulation tank 14 so as to be 3 mg / L, and a membrane filtration treatment was performed. The obtained membrane filtered water 18 was supplied to a diffuser type ozone contact tank 30, and 5 mg / L ozone was injected into the ozone contact tank 30 for treatment. As a result of a series of water-passing experiments, the transmembrane pressure in the microfiltration hollow fiber membrane 17 exceeded 100 kPa 8 months after the start of water passage, and by using the method and apparatus of the present invention. It has been found that the frequency of chemical cleaning of the microfiltration hollow fiber membrane 17 can be greatly reduced. During this experiment,
The water quality data for each main process is as shown in Table 4.

[0061]

[Table 4]

Although there was no significant difference in the water quality of the sewage compared with the water quality data (Table 3) obtained by experiments using the conventional method and apparatus, the ozone treatment using the method and apparatus of the present invention was not performed. The COD and chromaticity of the water are lower than the COD and chromaticity of the membrane filtered water using the conventional method and apparatus.
It was found that the COD component and the chromaticity component contained in the biologically treated water were satisfactorily treated.

[0063]

As described above, according to the present invention, the wastewater is subjected to the biological nitrification denitrification treatment, then to the solid-liquid separation treatment, and then to the separated liquid of the solid-liquid separation device. After performing the coagulant addition treatment, a neutralization treatment is performed for sedimentation separation, and further, in a sewage treatment method and a treatment apparatus for performing solid-liquid separation treatment with a membrane, clogging of the membrane can be significantly reduced. The labor required for chemical cleaning to cope with clogging of the membrane and the cost of chemicals for cleaning can be reduced, and the service life of the membrane can be prolonged and the cost of replacing the membrane can be reduced.

Further, by controlling the injection of ozone, the amount of injected ozone can be minimized, and the consumption of ozone can be suppressed. Furthermore, a high quality of treated water can be obtained, the load on the activated carbon adsorption tower at the subsequent stage can be reduced, the frequency of replacement or regeneration of activated carbon can be reduced, and maintenance can be facilitated.

In the cleaning step of the membrane filtration device, ozone from the ozone generator is supplied to the ozone contact tank, so that there is no need for intermittent operation and waste of generated ozone can be eliminated.

[Brief description of the drawings]

FIG. 1 is a diagram showing a processing flow of an embodiment of the present invention.

FIG. 2 is a diagram showing a processing flow of another embodiment of the present invention.

FIG. 3 is a diagram showing a processing flow of another embodiment of the present invention.

FIG. 4 is a diagram showing a processing flow of another embodiment of the present invention.

FIG. 5 is a diagram showing a processing flow of another embodiment of the present invention.

FIG. 6 is a diagram showing a processing flow of a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sewage, 2 ... Denitrification tank, 3 ... Nitrification tank, 4 ... Solid-liquid separation apparatus, 5 ... Biologically treated water, 6 ... Coagulant, 7 ... Coagulant tank, 8 ... Alkaline agent, 9 ... Neutralization tank, 10 ... settling separation tank, 11 ... supernatant, 12 ... ozone, 13 ... ozone generator, 14 ... circulation tank, 15 ... waste ozone gas, 16 ... waste ozone gas treatment equipment, 17 ... membrane filtration device, 18 ... membrane filtration water, 19: ozone detector, 20: activated carbon adsorption tower, 21: discharge water, 22: carrier for immobilizing microorganisms, 23: ozone dissolving tank, 24: ozone exhaust gas, 25: membrane filtration device, 26: neutralized water, 30 ... Ozone contact tank, 31 ... ozone, 32 ... exhausted ozone gas, 33
... Ozonated water

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C02F 9/00 504 C02F 9/00 504A 504D 1/44 1/44 K 1/52 1/52 E 3 / 10 ZAB 3/10 ZABA 3/34 101 3/34 101D (72) Inventor Kenichiro Mizuno 1-1-2 Marunouchi, Chiyoda-ku, Tokyo F-term in Nippon Kokan Co., Ltd. 4D003 AA12 AB02 BA02 CA02 CA03 CA08 CA10 EA14 EA30 4D006 GA06 GA07 HA01 HA21 HA41 HA61 HA95 KA12 KB12 KB13 KB14 KB22 KB23 KC16 KD16 KD21 KD24 KE11Q MA01 MA02 MA03 MA04 MC03 MC29 MC39 PA01 PB08 PB24 PC63 4D040 BB05 BB22 BB24 BB25 BB24 BB25 BB24 BB25 BB24 BB25 BB24 BB25 BB24 DA04 DA13 DA16 EA13 EA17 EA32 FA01 FA02 FA12 FA15 FA17 FA22 FA24 FA26 FA28

Claims (13)

[Claims] The present invention relates to a method for performing a biological nitrification denitrification treatment comprising a denitrification tank and a nitrification tank, and then performing a solid-liquid separation treatment on the wastewater. Add a flocculant,
After reacting under acidic conditions, neutralization treatment is performed by adding an alkali agent, and the neutralized liquid is subjected to sedimentation separation in a sedimentation separation tank, and the supernatant obtained by the sedimentation separation In a wastewater treatment method comprising performing solid-liquid separation treatment with a membrane filtration device, wherein an ozone injection treatment is performed between the sedimentation separation tank and a circulation tank or a membrane supply tank to the membrane filtration device. A method for treating sewage, which is performed. 2. The treatment of sewage water according to claim 1, wherein the membrane filtration water from the membrane filtration device is introduced into an ozone contact tank, and ozone is re-injected into the ozone contact tank for treatment. Method. 3. The method for treating sewage according to claim 1, wherein the membrane used for the membrane filtration device is a microfiltration membrane or an ultrafiltration membrane. 4. The nitrification tank in the biological nitrification and denitrification treatment is a carrier-based nitrification tank in which a microorganism-immobilized carrier is present, and the carrier is fluidized by aerated air to perform nitrification treatment. The method for treating sewage according to claim 1, 2, or 3. 5. The microorganism-immobilized carrier mainly comprises a plastic such as polyethylene or polypropylene, and has a specific gravity of 1.00 to 1.10 and a particle size of 1.0 to 15.0 mm. 2. The method according to claim 1, wherein
The method for treating sewage according to any one of claims 4 to 4. 6. An ozone injection amount is adjusted by an ozone detector installed at a membrane filtration outlet of the membrane filtration device so that a residual ozone concentration in the membrane filtration water is in a range of 0.01 to 10 mg / L. The method for treating sewage according to any one of claims 1 to 5, characterized in that: 7. The adjustment of the ozone injection amount is performed by continuously measuring the residual ozone concentration of the membrane filtration water with an ozone detector installed at the membrane filtration outlet of the membrane filtration device, The ozone injection amount is feedback-controlled so that is within the range of 0.01 to 10 mg / L,
The method according to claim 6, wherein the residual ozone concentration is adjusted within the range. 8. The method according to claim 1, wherein ozone is directly injected in-line into a pipe connecting the sedimentation separation tank and a circulation tank or a membrane supply tank to the membrane filtration device. The method for treating sewage according to item 1. 9. The method for treating sewage according to claim 1, wherein ozone is injected into a circulation tank or a membrane supply tank of the membrane filtration device. 10. An ozone dissolving tank is provided between the sedimentation separation tank and a circulation tank or a membrane supply tank for the membrane filtration device, and ozone is injected into the ozone dissolving tank. The method for treating sewage according to any one of claims 1 to 7. 11. The wastewater is subjected to a biological nitrification denitrification treatment comprising a denitrification tank and a nitrification tank, followed by a solid-liquid separation treatment, and a coagulant for the separated liquid from the solid-liquid separation device. And neutralized by adding an alkali agent to the reaction solution.The supernatant obtained by sedimentation and separation of the neutralized solution is solidified by a membrane filtration device. In a sewage treatment apparatus for performing a liquid separation process, an ozone injection facility for injecting ozone between the settled separation amount and a circulation tank or a membrane supply tank to the membrane filtration device, and a membrane filtration outlet of the membrane filtration device An ozone detector for measuring the residual ozone concentration in the filtered membrane filtered water, and measuring the residual ozone concentration in the membrane filtered water with the ozone detector, and operating the ozone injecting equipment based on the measured value. Adjust the above Sewage treatment apparatus of the residual ozone concentration present in the filtered water from the filtration apparatus characterized in that deploying a control means for controlling to within a predetermined range. 12. The sewage treatment apparatus according to claim 11, wherein an ozone contact tank is further provided after the membrane filter to further ozone-treat the filtered water from the membrane filter. . 13. The nitrification tank in the biological nitrification and denitrification treatment is a carrier-based nitrification tank that contains a microorganism-immobilized carrier, fluidizes it with aerated air, and nitrifies wastewater. The sewage treatment apparatus according to claim 11 or 12, wherein the wastewater is treated.