JP2000000566A - Intensive water treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an economical intensive water treatment method capable of obtaining sufficient treated water quality in performing intensive treatment for the intensive treatment of purified water or the reutilization of sewage or waste water, capable of keeping a high filter flux by low power energy and not requiring a wide arranging area. SOLUTION: In an intensive water treatment method, ozone is added to raw water and dead end filtering is performed by a pressure system using an ozone-resistant membrane. Further, a flocculant and ozone may be added to raw water to perform dead end filtering by the pressure system using the ozone-resistant membrane and, at this time, the membrane may be washed by air bubbling.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to advanced treatment of purified water,
The present invention relates to an advanced treatment method for sewage such as human waste and domestic wastewater and industrial wastewater.

[0002]

2. Description of the Related Art As a typical treatment method of conventional water purification treatment, coagulation sedimentation-sand filtration-chlorine disinfection, coagulation sedimentation-sand filtration-activated carbon-chlorine disinfection or coagulation sedimentation-sand filtration-ozone-activated carbon-chlorine disinfection, etc. Is being done. Also, as a typical treatment method for the discharge and reuse of sewage such as human waste and domestic wastewater or industrial wastewater, first sedimentation basin-aeration-final sedimentation basin-chlorination and first sedimentation basin-aeration-final sedimentation basin -Coagulation sedimentation-Sand filtration-Chlorination, etc. have been performed.

On the other hand, water sources such as water storage dams have been developed as a measure against drought due to increased demand for domestic water, disorderly deforestation, abnormal weather, etc. In recent years, the quality of water sources has deteriorated. However, it is becoming impossible to obtain good drinking water by the conventional methods, which is a serious problem. Sewage such as human waste and domestic wastewater or organic wastewater from factories is discharged after removing various suspended substances and organic components contained in the wastewater by the method described above.
In recent years, however, attention has been paid to environmental issues, and such effluents have been required to be treated with even higher water quality. In addition, it has been proposed to reuse sewage and wastewater as water resources for effective use of water.For example, various uses such as park fountains and scenic views, hydrophilic water, miscellaneous water, industrial water, etc. are considered. And especially landscapes,
It has begun to be actually used as hydrophilic water.

Various types of membrane filtration using ultrafiltration membranes or microfiltration membranes have been proposed for the purpose of such advanced water purification treatment and sewage treatment. The problem is a decrease in filtration flux due to clogging,
Preventing membrane clogging is a major issue. Therefore, in the membrane filtration method, cross-flow filtration (tangent filtration) is generally used for the purpose of preventing membrane clogging.
Further, Japanese Patent Application Laid-Open No. 4-108518 proposes that tangential filtration is performed by adding an oxidizing gas such as ozone to raw water to prevent clogging of the membrane.

[0005]

In the membrane filtration method, one of two methods, a cross flow filtration method and a dead end filtration method, is employed. In the cross-flow filtration method, it is general to supply a membrane with an amount of water about twice the amount of filtered water,
About half of the water supplied to the membrane is returned to the raw water. Therefore, a large amount of pump power is required for the amount of drainage, and the economic efficiency is inferior.

On the other hand, in the dead-end filtration method, since the raw water supplied to the membrane is entirely filtered and the raw water supply amount and the filtrate amount are the same, the power energy of the pump with respect to the filtrate amount is lower than in the cross-flow filtration method. , Membrane clogging is likely to occur, the filtration flux is lower than that of cross-flow filtration, the membrane area required to obtain a predetermined amount of filtered water increases, the cost of the membrane increases, and the installation area increases. ,
After all it is not economical.

[0007] The present invention is to solve such problems, and it is an object of the present invention to obtain sufficient treated water quality in performing advanced treatment of purified water and advanced treatment of sewage. It is an object of the present invention to provide an economical advanced water treatment method that can maintain a high filtration flux with low power energy and does not require a large installation area.

[0008]

Means for Solving the Problems As a result of diligent studies on membrane filtration, the present inventors have found that when filtration is performed using an ozone-resistant membrane in the presence of ozone, a high filtration flow rate equivalent to cross-flow filtration is obtained even in dead-end filtration. The present inventors have found that a bundle can be obtained, and that a high filtration flux equivalent to that of cross-flow filtration can be obtained even in dead-end filtration by performing air bubbling as a washing operation of the membrane, thereby completing the present invention.

That is, the present invention provides (1) an advanced water treatment method for water purification treatment and sewage treatment, in which ozone is added to raw water and dead-end is performed by pressurization using an ozone-resistant film. An advanced water treatment method characterized by performing filtration, (2) a water treatment method according to the above (1), wherein a coagulant is added prior to adding ozone;
(3) The water treatment method according to the above (1) or (2), wherein the membrane is washed by air bubbling after performing dead end filtration or before performing dead end filtration.

The details of the present invention will be described below. As shown in FIG. 1, an example of a specific process of the advanced treatment method for purified water, sewage, and wastewater according to the present invention is as follows.
After ozone (O ₃ ) is added to raw water 1 consisting of lake water, stored water or secondary sewage water or industrial wastewater, and ozone treatment 2 is performed to ozone decompose suspended substances and organic substances in the raw water 1, Dead-end filtration is performed by a pressure method using an ozone-resistant film. Alternatively, as shown in FIG. 2, a coagulant is added 2 to raw water 1 consisting of river water, underflow water, lake water, storage water or secondary sewage water or industrial wastewater, and suspended substances contained in raw water 1 are removed. After coagulation, ozone (O ₃ ) is added, and an ozone treatment 3 for ozonolysis of suspended substances and organic substances in the raw water 1 is performed, followed by dead-end filtration by a pressure method using an ozone-resistant membrane. It is.

Conventionally, raw water consisting of river water, underground water, lake water, reservoir water or secondary sewage water or industrial wastewater is simply filtered by a membrane filtration method to obtain suspended substances contained in the raw water and membranes to be used. Organic substances having a size larger than the pore diameter are blocked by the membrane, so-called concentration polarization and a cake phase are generated, and at the same time, the organic substances in the raw water clog the membrane, or as a result of being adsorbed to the network inside the membrane, The filtration flux of the resulting membrane is reduced from a fraction to several tens of minutes compared to the filtration flux of the clarified water, which increases the membrane filtration cost and reduces the economic practicality. Was.

[0012] However decomposition is filtered in the presence of an oxidizing agent such as ozone (O ₃₎ to the raw water in the membrane filtration method, an organic substance adhering or clogging the membrane using an oxidizing agent such as ozone (O ₃₎ It is possible to obtain a very high filtration flux while filtering. That is, ozone (O ₃₎ filtration membrane in the presence, in order to attack repeatedly organics adhering to the membrane by ozone (O ₃₎ which passes through the membrane, will be performing filtration while continuously self-cleaning, the As a result, a filtration method capable of obtaining a high filtration flux is obtained. Furthermore, the cross-flow filtration is usually used in the membrane filtration, but the combined use of ozone or the use of ozone and air bubbling can provide a high filtration flux similar to that of the cross-flow even in the dead-end filtration, and the power energy Cost can be reduced.

The amount of ozone to be added to the raw water is preferably such that ozone remains in the filtered water in an amount of 0.05 ppm or more. Further, it is preferable that the ozone-resistant film is formed of a fluororesin film. The details of each unit process will be described below. [Ozone treatment] In the ozone treatment 2, ozone (O ₃ ) to be added may be ozone alone or ozonized air.
Ozone (O ₃ ) may be introduced through an air diffuser or the like provided at an appropriate position in the raw water storage tank.

[0014] As another configuration for adding ozone (O ₃₎ in water, to the middle of the tube to induce ozone resistance film raw water may be added ozone (O ₃₎ in the ejector system or line-mixing system Alternatively, ozone may be added from below the ozone resistant film. By adding ozone (O ₃ ), microorganisms, such as viruses, bacteria, molds, and protozoa, which live in the raw water 1 can be sterilized and removed. Furthermore, suspended substances and organic matter in the raw water 1 can be removed. Organic substances adhering to or clogged with an ozone-resistant film to be described later can be filtered while decomposing with ozonolysis, and an extremely high filtration flux can be obtained.

[0015] That is, ozone (O ₃₎ filtration membrane in the presence, in order to attack repeatedly organics adhering to the membrane by ozone (O ₃₎ which passes through the membrane, to performing filtration while continuously self-cleaning As a result, a high filtration flux can be obtained. In addition, the concentration of ozone remaining in the filtered water is generally preferably 0.05 ppm or more in order to increase the filtration speed when filtering with an ozone-resistant membrane. On the other hand, the concentration of ozone added to raw water for sterilizing microorganisms and removing odorous substances is generally 0.5 ppm depending on the quality of raw water.
That is all.

On the other hand, if the ozone concentration is too high, the economic efficiency is reduced.
It is preferably about 0 ppm, more preferably 0.1 to 30 pp
It is preferable to add ozone (O ₃ ) at a concentration of m. Raw water 1
The contact time with the ozone (O ₃ ) need not be particularly considered as long as the organic matter and the ozone water adhering to the surface of the film structure are continuously supplied. Usually, a contact time of 1 second to 30 minutes is common. [Addition of flocculant] In membrane filtration, the pore size of
In the region F), the pore diameter becomes large, so that suspended substances (SS), bacteria, and the like in the raw water 1 enter the membrane. Therefore, in the case of raw water that is high in suspended solids and bacteria, a large amount of ozone injection is required to obtain a high filtration flux. For the purpose of reducing the amount of added ozone, it is preferable to use a coagulant such as polyaluminum chloride (PAC), bansulfate, ferrous chloride, and ferric chloride before adding ozone.

The coagulant may be added to a storage tank such as a tank for storing the raw water 1, or may be added to the raw water 1 by a line mixing method in the middle of a pipe for guiding the ozone addition. good. The amount of the coagulant added must be such that the suspended substances contained in the raw water 1 can be coagulated, and generally 1 to 100 mg is added to 1 liter of the raw water 1, more preferably 2 to 5 per liter
What is necessary is just to add 0 mg. [Film Filtration Treatment with Ozone-Resistant Membrane] The ozone-resistant membrane is not particularly limited as long as it is a filter membrane that is not deteriorated by ozone (O ₃ ). For example, an inorganic membrane such as an ozone-resistant ceramic, a polyvinylidene fluoride (PVDF) membrane And an organic film such as a fluororesin film such as a polytetrafluoroethylene (PTFE) film, an ethylene-tetrafluoroethylene copolymer (ETFE) film, and a polyfluoroacrylate (PFA) film. It is particularly preferable to use a polyvinylidene fluoride (PVDF) film.

The ozone resistant membrane is preferably a hollow fiber membrane. The pore size provided in such an ozone-resistant membrane is determined by ultrafiltration (UF) membrane to microfiltration (M
F) The pore size range of the membrane may be used, but it is preferred to use a microfiltration (MF) membrane because the filtration flow rate of the membrane is basically high. For example, the pore size of the membrane is preferably 0.001 to 1 μm, and more preferably 0.05 to 1 μm.

The filtration is performed by dead-end filtration. To obtain a high filtration flux equivalent to that of the cross-flow filtration, it is preferable to leave 0.05 ppm or more of ozone in the filtered water. In air bubbling, after filtration for a certain period of time, filtration is stopped, gas is supplied to the membrane surface, and the membrane is washed by vibrating the membrane surface. Organic substances originally adsorbed on the membrane surface are decomposed by ozone and become non-adsorbent, and in the presence of ozone, non-adsorbable substances (organic and inorganic substances) that block the pores of the membrane are effectively eliminated by air bubbling. Great cleaning effect can be obtained.

Air bubbling may be used in combination with backwashing, or in the order of filtration-air bubbling-backwashing, or filtration-backflow washing-air bubbling, filtration- (simultaneous backwashing with air bubbling). May be. Air bubbling is preferably performed for 1 second to 6 minutes. If the time is less than 1 second, the effect is small, and no filtration is performed during air bubbling.

As described above, since the membrane filtration method using an ozone-resistant membrane has a high filtration flux and high efficiency even in dead-end filtration, the equipment cost of the entire process can be reduced. Can be reduced.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the advanced water treatment method according to the present invention will be specifically described with reference to the drawings. An example of the process of the advanced treatment method for purified water, sewage, and wastewater according to the present invention is as follows.
As shown in FIG. 1, after performing ozone treatment 2 for adding ozone to raw water 1 to ozone decompose suspended substances and organic substances in the raw water 1, dead-end filtration treatment 3 using an ozone-resistant membrane is performed. . Alternatively, as shown in FIG. 2, after performing 4 to add a flocculant to 1 in raw water, and performing ozone treatment 2 to add ozone to ozone decompose suspended substances and organic substances,
A dead end filtration process 3 using an ozone resistant film is performed. FIGS. 1 and 2 show only a basic process. If necessary, a treatment such as an activated carbon treatment or a reverse osmosis membrane treatment may be performed after the membrane filtration treatment using an ozone-resistant membrane.

Hereinafter, embodiments of the present invention will be described in detail.

[0024]

Example 1 Raw water 1 has a turbidity of 3 to 4 degrees and COD
Using river surface water with a (chemical oxygen demand) value of 2 mg / L and a water temperature of 12 ° C., as shown in FIG. 1, raw water 1 → ozone treatment 2 → dead end filtration treatment 3 using an ozone resistant membrane was sequentially performed. Then, an activated carbon treatment was performed at a later stage.

In the dead end filtration process 3 using an ozone resistant membrane, a 0.1 μm pore diameter PVD is used as the ozone resistant membrane.
A microfiltration (MF) membrane made of F (polyvinylidene fluoride) was used. This PVDF hollow fiber module having a pore diameter of 0.1 μm is an external pressure type module in which 1,800 yarns having an inner diameter of 0.7 mmφ and an outer diameter of 1.25 mmφ are bundled and housed in a 3-inch diameter PVC (polyvinyl chloride) casing. When the membrane area is 7.0 m ² and the clarified water flux is 1.8 m ^{3 /} h,
The module filtration pressure is 0.5 kgf / cm ² .

The raw water 1 is supplied to a raw water tank and supplied to the PVDF hollow fiber module by a pump at an amount of 1.5 m ³ per hour. An ejector type ozone addition port is provided between the outlet of the pump and the module, and adds ozone (O ₃ ) using air as a raw material. When ozone is added, an air layer is formed in the module by dead-end filtration. Therefore, a buffer tank was provided between the ejector and the module for the purpose of removing excess air. The ozone concentration immediately before the module entrance was 2 ppm, and the residual ozone concentration in the filtered water at this time was 0.2 ppm. The activated carbon treatment tank used was designed so that the LV was 250 m / day and the SV was 10 / Hr.

In the dead end filtration, constant flow filtration is performed.
1.5 m / h of drainage flux from VDF hollow fiber module
^{At the same time} , the raw water was supplied to the raw water tank at a filtration flow rate of 1.5 m ³ per hour. The operating condition is 10 filtration.
After that, the operation of performing backflow cleaning for 15 seconds was repeated, and air of 2 Nm ^{3 /} h was supplied from the lower part of the module every 12 hours to perform air bubbling for 120 seconds. As a result, the level of the filtration flux can be maintained at the initial value of 1.5 m ^{3 /} h for 3 months, during which the pressure rise is 0.0
It was 3 kg / cm ² .

As a result of analyzing the water discharged from the activated carbon treatment tank,
The COD (Chemical Oxygen Demand) value was 0.4 mg / L, the turbidity was 0.02 degrees, Escherichia coli and general bacteria were not detected, and the other items sufficiently satisfied the criteria for drinking water.

[0029]

[Comparative Example 1] In Example 1, the raw water tank
Raw water supply to the VDF hollow fiber module is 3 m ^{3 /} h
And then, taken out drainage flux per hour 1.5 m ^3, except that the return circulation water per hour 1.5 m ³ as a concentrate circulating water in the raw water tank was conducted in the same manner as in Example 1.

As a result, the filtration flux level could be maintained at the initial value of 1.5 m ³ / h for 3 months, and the pressure increase during that time was 0.03 kg / cm ² , but the power energy of the pump was Twice as much as Example 1 was required.

[0031]

Example 2 Raw water 1 has a turbidity of 10 degrees, a COD (chemical oxygen demand) of 13 to 20 mg / liter, and a BOD
(Biological oxygen demand) value is 20-30mg / l,
The sewage secondary treatment water whose water temperature was 25 ° C was used. The dead-end filtration was performed in the same manner as in Example 1 except that no activated carbon treatment tank was provided after the dead-end filtration. However, the ozone concentration immediately before the entrance of the module was 10 mg / liter, the filtrate flux of the constant flow filtration was taken out at 1.3 m ³ , and the raw water tank was supplied with 1.3 m ³ of raw water 1 per hour of the filtrate flux.

The operating conditions are as follows: after performing filtration for 10 minutes, 2N / hour
Air bubbling was performed for 60 seconds by supplying m ³ air from the lower part of the module, and then backwashing was performed for 15 seconds. As a result, the level of the filtration flux was 1.3 hours / hour of the initial value.
m ³ could be maintained for 5 months, during which the pressure rise was 0.04 Kg · cm ² . The water quality of the obtained filtrate was 0.05 degrees in turbidity, the COD value was 12 mg / liter, and the BOD value was 1 mg / liter, which was sufficient water quality for landscape water and hydrophilic water.

[0033]

Example 3 The same operation as in Example 2 was performed except that air bubbling was not performed. As a result, 1
After ² months, the pressure rise was 0.2 kg / cm ^2, which was larger than that in Example ^{2 in} which air bubbling was performed, but operation with less power energy was possible.

[0034]

Example 4 In Example 2, after adding polyaluminum chloride (PAC) to the raw water by a line mixing method at a rate of 10 mg / liter relative to the raw water in terms of aluminum oxide, the ozone concentration at the module entrance was 5 mg.
The dead-end filtration was performed in the same manner as in Example 2 except that ozone was added so that the volume became 1 / liter. As a result, the level of the filtration flux can be maintained at the initial value of 1.3 m ^{3 /} h for 5 months, during which the pressure rise is 0.04 kg · c.
m ² .

That is, a high filtration flux could be obtained with a small amount of ozone by adding a coagulant.

[0036]

According to the present invention, it is possible to obtain excellent treated water quality in advanced treatment of purified water and sewage, and to maintain high filtration flux with low power energy.

[Brief description of the drawings]

FIG. 1 is a flowchart showing one embodiment of an advanced treatment method for purified water, sewage, and wastewater according to the present invention.

FIG. 2 is a flowchart showing another embodiment of the advanced treatment method for purified water, sewage, and drainage according to the present invention.

[Explanation of symbols]

 1. Raw water 2. Ozone treatment 3. Dead end filtration treatment using an ozone resistant membrane 4. Coagulant addition

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C02F 1/78 ZAB C02F 1/78 ZAB 9/00 502 9/00 502R 502P 502G 504 504E F-term (Reference) 4D006 GA07 HA19 HA95 KA03 KA43 KA64 KA72 KB12 KB13 KB30 KC03 KC13 KD08 KD19 KD21 KE03Q KE24Q KE28Q MA01 MA22 MA33 MC28 MC29X MC30 PA01 PA02 PB04 PB08 PC54 4D050 AA02 AA15 AB04 AB03 AB07 CA06

Claims (3)

[Claims] 1. An advanced water treatment method for water purification treatment and sewage treatment, wherein ozone is added to raw water and dead-end filtration is performed by a pressurization method using an ozone-resistant membrane. Advanced water treatment methods. 2. The advanced water treatment method according to claim 1, wherein a coagulant is added before adding ozone. 3. The membrane is washed by air bubbling after performing dead-end filtration or before performing dead-end filtration.
Advanced water treatment method as described.