JPH09187768A - Treatment method of sewage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To utilize treated water as amenity water for the public utilities by carrying out the final treatment of the sewage disposal with a foregoing reverse osmosis film module having a raw water contact film surface composed of a cross-linked polymer of a piperazineamino compound and a following reverse osmosis film module having a raw water contact film surface composed of a cross-linked aromatic polyamide. SOLUTION: Sewage is treated in a rough filter device 1, a biological treatment device 2 and a pretreatment device 3, and stored in a raw water tank 4. Then the raw water is fed into a foregoing reverse osmosis film separation module 61 by a foregoing water feed pump 51, and solution and organic matters are concentrated therein. Non-permeated water in which salt and the like are concentrated is discharged out of a discharge pipe 61. If necessary, the pH adjustment is carried out for the foregoing permeated water, and then the water is fed into a reverse osmosis film separation module 62, and the following permeation treatment is carried out. A raw water contact surface of the foregoing reverse osmosis separation module 61 is formed from a cross-linked polymer composed of a piperazineamino compound, while the raw water contact surface of the following reverse osmosis film separation module 62 is formed from a cross-linked aromatic polyamide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating sewage, in which sewage is treated by a membrane separation method.

[0002]

In the treatment of sewage in cities, the sewage is roughly filtered, then biologically treated by the activated sludge method, and the treated water is discharged into a river. That is, the coarsely filtered sewage is introduced into the aeration tank, the organic matter in the sewage is adsorbed and decomposed by the floating microorganisms in an aerobic state to grow the microorganisms, and further, the microorganism mixture liquid (ML) in the aeration tank is finally added. The wastewater is led to a sedimentation tank, the microorganisms are separated by sedimentation, and the sedimentation microorganisms are returned to the sewage inflow section of the aeration tank as return sludge for circulation processing, and excess sludge in the sedimentation tank is extracted at appropriate times. Recently, for environmental problems and effective use of water resources, it has been considered to reuse the treated water as hydrophilic water for public facilities such as parks without discharging it. For this effective use, it is necessary to remove nutrient salts such as nitrogen and phosphorus from the treated water at a high removal rate.

[0003]

Conventionally, it has been known as a so-called biological nitrification denitrification method that activated sludge treatment is repeated in an anaerobic / aerobic state to remove nitrogen as well as organic substances. Further, as a so-called biological nitrifying denitrifying phosphorus removing method, it is possible to remove nitrogen and phosphorus at the same time as organic matter by repeating the activated sludge treatment sequentially in a completely anaerobic state, anoxic state and aerobic state. Are known. However, it is difficult for these methods to remove nitrogen and phosphorus compounds to the extent that the final treated water can be effectively reused.

In order to remove the nitrogen and phosphorus compounds, it has been proposed to carry out a final high-order treatment with a reverse osmosis membrane module. Since the amount of treated water in this treatment is large, it is appropriate to use a reverse osmosis membrane module having a large permeation flux.
A cross-linked aromatic polyamide-based reverse osmosis membrane module has attracted attention as a module. However, according to the test results of the inventors of the present invention, when the above-mentioned final high-order treatment is carried out with this crosslinked aromatic polyamide-based reverse osmosis membrane module, the permeation flux is lowered relatively early and a predetermined value I found it difficult to maintain the processing speed. It is presumed that the cause of the decrease in the early permeation flux is a result of the surfactant contained in the treated water being remarkably adsorbed on the surface of the crosslinked aromatic polyamide membrane and the hydrophilicity of the membrane surface being lowered.

An object of the present invention is to treat sewage in a high-level final treatment of sewage with a high and stable permeation flux, and at a high removal rate of nutrient salts such as nitrogen and phosphorus. It is possible to remove the wastewater and use the treated water as hydrophilic water for public facilities.

[0006]

Means for Solving the Problems The method for treating sewage according to the present invention comprises a reverse osmosis membrane module of the preceding stage having a membrane surface in contact with raw water made of a crosslinked polymer of a piperazine amino compound, and a membrane in contact with raw water. The reverse osmosis membrane module of the latter stage whose surface is formed of a crosslinked aromatic polyamide is a constitution characterized by performing the final high-order treatment in the sewage treatment. , The permeation flux is 0.1
0m ³ / m ² · [kgf / cm ² ] · day or more, pH 6.5, 0.05% concentration of saline as raw water at 25 ℃, operating pressure 7.5kgf / cm ² after 30 minutes of operation Salt inhibition rate at 90
% Or more, and the average surface roughness of the film surface is 55
It is preferable to use those having a thickness of at least nm.

In the present invention, the reverse osmosis membrane module of the latter stage is used.
The reason why the cross-linked aromatic polyamide reverse osmosis membrane module is used for the resin is that the permeation flux is large and the solute removal rate for nitrogen and phosphorus compounds is large. The cross-linked aromatic polyamide film is a monomer composed of a monomeric aromatic polyamine reactant having at least two amine functional groups and a polyfunctional acyl halide or a mixture thereof on a porous substrate. Made by interfacially polymerizing an aromatic amine-reactive reactant (which has an average of at least about 2.2 acyl halide groups per molecule of this amine-reactive reactant) with an aromatic amine-reactive reactant in the presence of an amine salt. Composite membranes (e.g., Japanese Patent No. 1948993) are preferably used, and monomeric aromatic polyamine reactants having at least two amine functional groups include, for example, m-phenylenediamine as a polyfunctional compound. For example, trimenyl chloride is used as the monomeric aromatic amine reactive reactant comprising an acyl halide. It is also possible to use a reverse osmosis membrane module using a cross-linked aromatic polyamide-based membrane other than this.

In the present invention, the reverse osmosis membrane module of the preceding stage is used.
The reason why the membrane surface formed of a cross-linked polymer of piperazine amino compound is used for the polymer is that the decrease of the permeation flux due to contact with the surfactant is extremely low, and it prevents the passage of the surfactant while Guarantee a sufficient amount of liquid supplied to the crosslinked aromatic polyamide-based reverse osmosis membrane module and block the reverse osmosis membrane module in the subsequent stage from the surfactant to remove nitrogen and phosphorus under high permeation flux. This is for removing with a high removal rate, and as the piperazine amino compound, 2-methylpiperazine,
2,5-dimethylpiperazine, homopiperazine and the like can be mentioned (for example, Japanese Examined Patent Publication No. 61-27083).

In order to secure the above high permeation flux, the reverse osmosis membrane module in the latter stage has a permeation flux of 0.10 m ³ / m 2.
²・ [kgf / cm ² ] ・ day or more is used, and in order to secure a high removal rate for the above-mentioned nitrogen and phosphorus, pH
6.5, saline solution with a concentration of 0.05% as raw water at 25 ° C,
A salt inhibition rate of 90% or more after 30 minutes of operation at an operating pressure of 7.5 kgf / cm ² is used. In the latter-stage reverse osmosis membrane module, in order to increase the surface area of the membrane and substantially increase the membrane area, the average surface roughness Ra of the membrane surface is increased.
Is preferably 55 nm or more.

The average roughness Ra is defined by the following equation and can be measured by an atomic force microscope, a frictional force microscope, a tunnel microscope, a scanning electron microscope, a transmission electron microscope or the like.

[Equation 1] Where a and b are the lengths of two sides of the specified surface (rectangle), S is the area of the specified surface, f (x, y) is the height within the specified surface, and Zo is the specified surface given by the following equation. Is the average height.

[Equation 2]

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a sewage treatment facility used in the present invention. In FIG. 1, reference numeral 1 is a coarse filtration device, which removes coarse suspended matter and oils and fats that interfere with subsequent treatment facilities, and screens, sand basins,
An oil and fat separation tank, a pH adjusting tank, etc. are provided. 2 is a biological treatment apparatus. Reference numeral 3 is a pretreatment device, which is provided to remove suspended matter and protect the reverse osmosis membrane module after it from suspended matter. For example, a sand filter device or a microfiltration device is used. 4 is a raw water tank, 51 is a pre-stage liquid feed pump, 61 is a pre-stage reverse osmosis membrane module whose membrane surface in contact with raw water is a cross-linked polymer of piperazine amino compound, and 611 is a pre-stage non-permeate discharge Reference numeral 612 denotes a front-stage permeated water outflow pipe.

7 is an intermediate tank such as a pipe header
Reference numeral 52 is a rear-stage liquid feed pump, 62 is a rear-stage reverse osmosis membrane module whose membrane surface in contact with raw water is formed of a crosslinked aromatic polyamide, 622 is a rear-stage permeated water outflow pipe, and 620 is a rear-stage non-permeate. Water pipes are respectively shown. A part of the rear-stage non-permeate water is returned to the raw water tank 4 by the return pipe 620 ′, and the rest is discharged from the rear-stage non-permeate discharge pipe 621. It is taken out as water from the outflow pipe 622. Reference numeral 8 denotes an alkaline liquid tank provided as necessary, and 9 denotes a pump for injecting the alkaline liquid into the permeate side of the pre-stage reverse osmosis membrane separation module 61.

In order to treat sewage according to the present invention using the above facility, the sewage is treated by the rough filtration device 1, the biological treatment device 2 and the pretreatment device 3, which is once stored in the raw water tank 4 and the pre-stage liquid transfer. The pump 51 supplies the pre-stage reverse osmosis membrane separation module 61 at a predetermined pressure, and the non-permeated water concentrated such as salt is discharged from the pre-stage non-permeate water discharge pipe 611 by blocking the passage of salts and organic substances in the raw water. Then, permeated water from which salts and the like have been removed is generated on the permeate side at a predetermined removal rate.

The pre-stage permeated water of the pre-stage reverse osmosis membrane separation module 61 is temporarily stored in the intermediate tank 7, and if necessary, an alkali solution, for example, sodium hydroxide, potassium hydroxide, or the like is injected by the pump 9 to obtain the permeated water. Adjust the pH of the permeate,
The pH-adjusted permeated water is supplied to the rear-stage reverse osmosis membrane separation module 62 at a predetermined pressure by the liquid feed pump 52, and a part of the rear-stage non-permeated water in which salt is concentrated is returned to the front-stage line side. The remaining non-permeated water in the second stage is discharged into the non-permeated water in the second stage 6
Eject from 21. Rear-stage reverse osmosis membrane separation module 6
The second-stage permeated water further desalted by 2 will be used as water for hydrophilic water and the like. In the above, all the non-permeated water of the rear-stage reverse osmosis membrane separation module 62 can be discharged, and the return amount to the front-stage line can be made zero.

As shown in FIG. 2, the operation pressure of not only the pre-stage reverse osmosis membrane separation module 61 but also the post-stage reverse osmosis membrane separation module 62 is reduced as shown in FIG. In this case, since the pre-stage reverse osmosis membrane separation module 61 is also pressurized on its permeation side, the permeation side also has a pressure-resistant structure capable of coping with this pressing force. In FIG. 2, the same reference numerals as those in FIG. 1 indicate the same components. The above-mentioned reverse osmosis membrane separation modules at the front and rear stages include a spiral type, a hollow fiber type, a tuber type, and a frame type. And plate type can be used. In the above, several module units are connected in series or in parallel to the reverse osmosis membrane separation module, the supply side of these unit groups are collectively connected to the raw water supply pipe, and the permeate side is collectively connected. Those connected to the permeate outflow pipe can also be used.

The sewage to be treated by the present invention contains a large amount of surfactants for draining soap and detergent. Thus, in a reverse osmosis membrane module in which the surface layer of the membrane is formed of a crosslinked polymer of a piperazine amino compound,
Even when contacted with the surfactant, the adsorption of the surfactant on the membrane surface was hardly observed, and the permeation flux was slightly reduced. This surfactant has a relatively high molecular weight and is substantially almost completely blocked by the preceding reverse osmosis membrane module. Therefore, by the almost complete blocking of the surfactant by the former reverse osmosis membrane module, the low permeation of the latter reverse osmosis membrane module in which the surface layer of the membrane was formed by the crosslinked aromatic polyamide under the contact with the surfactant was achieved. The latter reverse osmosis membrane module can effectively exhibit its original high salt removal rate for nitrogen and phosphorus without exhibiting flux, and as a hydrophilic water with a small nitrogen and phosphorus content. It is possible to obtain usable permeate of high water quality.

[0017]

【Example】

[Example] The reverse osmosis membrane module in the former stage had pH 6.
5. Using salt water with a concentration of 0.15% as raw water at 25 ° C and operating pressure of 10 kgf / cm ² , the salt inhibition rate after 30 minutes of operation was 9
A spiral type reverse osmosis membrane module manufactured by Nitto Denko Co., Ltd., which is 0% and the membrane is a piperazine polyamide type, was used. This reverse osmosis membrane module membrane (composite membrane) comprises 0.25% by weight of polyvinyl alcohol, 0.25% by weight of piperazine and 0.5% by weight of sodium hydroxide on a porous substrate made of polysulfone. After being uniformly applied with a stock solution containing the above, it was immersed in a 1% by weight solution of trimesic acid chloride in n-hexane at a temperature of 25 ° C. for 1 minute and then pulled up to volatilize n-hexane, and then at a temperature of 110 ° C. It was heat treated for 10 minutes and contributed to the crosslinking reaction inside the undiluted coating layer between the ultrathin film of the crosslinked polymer of polyvinyl alcohol and the piperazine amino compound and the ultrathin film and the polysulfone porous substrate. It is composed of an unreacted water-insoluble polyvinyl alcohol intermediate layer and a polysulfone porous substrate.

The reverse osmosis membrane module in the latter stage has a pH of 6.
5, salt water having a concentration of 0.05% was used as raw water at 25 ° C. and an operating pressure of 7.5 kgf / cm ^{2, and} after 30 minutes of operation, the salt rejection rate was 99.5% and the pure permeation flux was 0. 13m ³ / m ²・ [kgf /
cm ² ] · day, the membrane was a cross-linked aromatic polyamide system, and a spiral reverse osmosis membrane module manufactured by Nitto Denko Corporation having an average surface roughness of 80 nm was used. The membrane of this reverse osmosis membrane module has a structure in which m is formed on a porous substrate made of polysulfone.
2.0% by weight of phenylenediamine, 0.15% by weight of sodium lauryl sulfate, 2.0% of triethylamine
Wt%, camphor-sulfonic acid 4.0 wt%, isopropyl alcohol 20 wt% of the stock solution was contacted, the hexane solution containing 0.15 wt% of trimesic acid chloride was added to the stock solution layer thus formed. Contact
After that, the reaction product skin layer having a surface average roughness of 80 nm was formed by holding it in a hot air dryer at 120 ° C. for 3 minutes.

In FIG. 1 (the alkaline liquid tank 8 and the pump 9 are omitted), the adjusted raw water containing the detergent at a high concentration with a nitrous acid concentration of 50 ppm, an ammoniacal nitrogen concentration of 50 ppm and a phosphorus concentration of 50 ppm is stored in the raw water tank 4. Save
The liquid feed pressure of the front stage liquid feed pump 51 is 10 kgf / cm ² , the liquid feed pressure of the rear stage liquid feed pump 52 is 7.5 kgf / cm ² , and the initial permeation flux of the rear stage reverse osmosis membrane module 62 is 1.0 m. ³ / m ²
[Kgf / cm ² ] ・ Driving for a day,
It continued for 0 hours. The water quality of the permeate of the latter-stage reverse osmosis membrane module 62 is as shown in Table 1, and the state of the permeate flow rate decreasing with time was as shown in FIG.

Comparative Example 1 Only the spiral type reverse osmosis membrane module manufactured by Nitto Denko Co., Ltd., which was used as the preceding stage reverse osmosis membrane module in the example, was operated at an operating pressure of 10 kgf / cm ² , and The same adjusted raw water was treated. The initial permeation flux was 1.7 m ³ / m ² · [kgf / cm ² ] · day. The water quality of the permeated water in this comparative example is as shown in Table 1, and the state of the permeated water flow rate decreasing with time was as shown in FIG.

Comparative Example 2 Only the spiral type reverse osmosis membrane module manufactured by Nitto Denko Co., Ltd., which was used as the latter-stage reverse osmosis membrane module in the example, was operated at an operating pressure of 10 kgf / cm ² and The same adjusted raw water was treated. The initial flux was 0.8 m ³ / m ² · [kgf / cm ² ] · day. The water quality of the permeated water in this comparative example is as shown in Table 1, and the state of the permeated water flow rate decreasing with time was as shown in FIG.

[0022]

[Table 1]

As is clear from Table 1, according to the method for treating sewage according to the present invention, even if the sewage contains a large amount of a surfactant, it is possible to treat the nitrogen and phosphorus compounds in extremely small amounts, and Since the permeation flux can be made sufficiently large, the treated water can be effectively used as water.

[0024]

According to the sewage treatment method of the present invention,
By substantially blocking the surfactant, the crosslinkable aromatic polyamide reverse osmosis membrane module can effectively exhibit the original excellent removal rate and permeation flux for nitrogen and phosphorus compounds, and the surfactant can be effectively added to sewage. Even if it is contained in a large amount, it can be treated with extremely small amounts of nitrogen and phosphorus, and its permeation flux can be made sufficiently large, so the treated water can be effectively used as hydrophilic water and by returning it to a water source. it can.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of a sewage treatment facility used in the present invention.

FIG. 2 is an explanatory diagram showing another example of the sewage treatment facility used in the present invention.

FIG. 3 is a chart showing permeation flux characteristics over time of an example according to the present invention and a comparative example.

[Explanation of symbols]

 1 Coarse Filtration Device 2 Biological Treatment Device 3 Pretreatment Device 4 Raw Water Tank 51 Pre-stage Liquid Delivery Pump 52 Post-stage Liquid Delivery Pump 61 Pre-stage Reverse Osmosis Membrane Module 62 Post-stage Reverse Osmosis Membrane Module 7 Intermediate Tank

[Procedure amendment]

[Submission date] April 5, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

In the present invention, the reason why the crosslinked aromatic polyamide reverse osmosis membrane module is used for the reverse osmosis membrane module in the latter stage is that the permeation flux is large and the solute removal rate for nitrogen and phosphorus compounds is large. Is. The cross-linked aromatic polyamide film is a monomer composed of a monomeric aromatic polyamine reactant having at least two amine functional groups and a polyfunctional acyl halide or a mixture thereof on a porous substrate. Made by interfacially polymerizing an aromatic amine-reactive reactant (which has an average of at least about 2.2 acyl halide groups per molecule of this amine-reactive reactant) with an aromatic amine-reactive reactant in the presence of an amine salt. Composite membranes (e.g., Japanese Patent No. 1948993) are preferably used, and monomeric aromatic polyamine reactants having at least two amine functional groups include, for example, m-phenylenediamine as a polyfunctional compound. Monomeric aromatic amine-reactive reactants consisting of acyl halides include, for example, trimesoyl acrylate.
Loride is used. It is also possible to use a reverse osmosis membrane module using a cross-linked aromatic polyamide-based membrane other than this.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction contents]

The reverse osmosis membrane module in the latter stage has a pH of 6.
5, salt water having a concentration of 0.05% as raw water at 25 ° C. and an operating pressure of 7.5 kgf / cm ² had a salt rejection of 99.5% and a pure water permeation flux of 0 after 30 minutes of operation. .13m ³ /
A spiral-type reverse osmosis membrane module manufactured by Nitto Denko Corp. having a m ² · [kgf / cm ² ] · day, a membrane made of a cross-linked aromatic polyamide, and an average surface roughness of 80 nm was used. The membrane of this reverse osmosis membrane module has 2.0 m-phenylenediamine on a porous substrate made of polysulfone.
% By weight, sodium lauryl sulfate 0.15% by weight, triethylamine 2.0% by weight, camphorsulfonic acid 4.0% by weight, isopropyl alcohol 20% by weight
The contained stock solution is brought into contact with the stock solution layer thus formed,
A hexane solution containing 0.15% by weight of trimesic acid chloride was brought into contact with the hexane solution, followed by 3 hours with a hot air dryer at 120 ° C.
The reaction product skin layer having a surface average roughness of 80 nm was formed by holding for a minute.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction contents]

In FIG. 1 (the alkaline liquid tank 8 and the pump 9 are omitted), the adjusted raw water containing the detergent at a high concentration with a nitrous acid concentration of 50 ppm, an ammoniacal nitrogen concentration of 50 ppm and a phosphorus concentration of 50 ppm is stored in the raw water tank 4. Save
The liquid feeding pressure of the former-stage liquid feeding pump 51 is 10 kgf / cm ² ,
The liquid feeding pressure of the latter-stage liquid feeding pump 52 is 7.5 kgf / cm ²
The initial permeation flux of the latter-stage reverse osmosis membrane module 62 is 1.0 m ³ / m ² · day (0.133 m ³ / m ² ·
[Kgf / cm ² ] · day), and the operation was continued for 200 hours. The water quality of the permeate of the latter-stage reverse osmosis membrane module 62 is as shown in Table 1, and the state of the permeate flow rate decreasing with time was as shown in FIG.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction contents]

[Comparative Example 1] Only the spiral type reverse osmosis membrane module manufactured by Nitto Denko Co., Ltd., which was used as the previous stage reverse osmosis membrane module in the example, was operated at an operating pressure of 10 kgf / cm ² to obtain the same adjusted raw water as the example. Processed. The initial flux was 1.7 m ³ / m ² · day . The water quality of the permeated water in this comparative example is as shown in Table 1, and the state of the permeated water flow rate decreasing with time was as shown in FIG.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction contents]

Comparative Example 2 Only the spiral type reverse osmosis membrane module manufactured by Nitto Denko Co., Ltd., which was used as the latter-stage reverse osmosis membrane module in the example, was operated at an operating pressure of 10 kgf / cm ² , and the same adjusted raw water as the example was supplied. Processed. The initial flux was 0.8 m ³ / m ² · day . The water quality of the permeated water in this comparative example is as shown in Table 1, and the state of the permeated water flow rate decreasing with time was as shown in FIG.

Claims (3)

[Claims] 1. A reverse osmosis membrane module of the preceding stage, wherein the membrane surface in contact with raw water is formed of a cross-linked polymer of piperazine amino compound.
And a latter-stage reverse osmosis membrane module in which the membrane surface in contact with raw water is formed of a crosslinked aromatic polyamide, the final high-order treatment in the sewage treatment is performed. 2. The reverse osmosis membrane module of the latter stage has a permeation flux of 0.10 m ³ / m ² · [kgf / cm ² ] · day or more and a pH of 6.
5. The method for treating sewage according to claim 1, wherein the salt inhibition rate after 30 minutes of operation at 25 ° C. and an operating pressure of 7.5 kgf / cm ² is 90% or more using saline solution having a concentration of 0.05% as raw water. . 3. The method for treating sewage according to claim 1 or 2, wherein the average surface roughness of the membrane surface of the reverse osmosis membrane module at the latter stage is 55 nm or more.