JPH10113659A - Purifying method of water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove org. matters and sludge component in water to a high level so that the method can be used for refining and recycling of city water, sewage, industrial water and process water or for pretreatment to produce ultrapure water by combining a process to remove sludge by membrane filtration and a process to accelerate oxidation reaction with ozone by a catalyst. SOLUTION: For example, a vinylidene polymer resin hollow fiber precision filter membrane is prepared and is attached to a filtering tank 3 of an evaluating device which is composed of a raw water tank 1, a pressurizing pump 2, a filtering tank 3, a tower packed with a catalyst which accelerates ozone oxidation reaction, and a product tank 6. Then a secondary treated sewage water as the supply source water is supplied in the raw water tank 1, while ozone gas is injected by an ozone gas generating device 4 through the middle of the piping between the pressurizlng pump 2 and the filtering tank 3 including a filter membrane. All of the raw water mixed with the ozone gas is filtered through the precision filter membrane in the filtering tank 3, the filtered water is supplied to the tower 5 to be treated, and the treated water is stored in the product water tank 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a water supply system, a sewer system,
The present invention relates to a water purification method used for purification, recycling, and pretreatment of ultrapure water production for industrial water and process water.

[0002]

2. Description of the Related Art Water purification is carried out by coagulation sedimentation, sand filtration, chlorine injection, ozone instead of chlorine injection in the above-mentioned treatment, turbidity of suspended substances by a membrane, etc. Has been done. In some cases, a catalyst is added for the purpose of accelerating the ozone oxidation reaction.

Further, a water purification treatment using a combination of membrane and ozone oxidation is introduced in Japanese Patent Application Laid-Open No. Hei 7-265671. However, the purification process has the following disadvantages. (1) Coagulation sedimentation, sand filtration, chlorine injection, off-flavor, THM
The quality of the product water is inferior, such as the generation of water, and changes in turbidity are also easily affected by the quality of the raw water. It is necessary to finely adjust the amount of coagulant and chlorine to be added and injected. Hard to say.

(2) A water treatment method using a membrane such as an ultrafiltration membrane or a microfiltration membrane for removing turbid components is being applied to a relatively small-scale water purification plant (simple water supply). Although the amount of water taken per area is small, it is less economical than the above-mentioned water purification treatment by coagulation sedimentation, sand filtration and chlorine injection, and the water quality itself is superior to the treated water quality of (1),
It is hard to say that the water quality is satisfactory enough.

(3) The above is a part of the cause of THM generation by coagulation sedimentation, sand filtration and chlorine injection, and generation of off-flavor.
Although so-called advanced treatment is applied to a plurality of large-scale water treatment plants, in which organic substances are decomposed by ozone oxidation without THM generation by chlorine injection, removal of suspended components still depends on coagulation sedimentation and sand filtration. Therefore, it is not an excellent method from the viewpoint of turbidity removal, and there are also low molecular weight organic compounds decomposed by ozone treatment. In order to remove the low-molecular-weight organic matter, it is necessary to add an activated carbon treatment step at a later stage. In the activated carbon treatment step, it is necessary to periodically update the activated carbon, which causes an increase in running costs. In addition, a low-molecular organic compound can be removed over a long period of time by the so-called microbial activated carbon treatment method, in which microorganisms live on the activated carbon surface and decompose low-molecular organic substances by the microorganisms. However, it is difficult to say that this is a completed processing technology because there is no clear point about it, and it is practically management (processing) of progress.

(4) Further, in order to improve the efficiency of decomposing organic substances in the above-mentioned ozone treatment, a method of further decomposing organic substances by performing ozone treatment in the presence of a catalyst for accelerating the ozone oxidation reaction is particularly described. Kaihei 2-17
No. 4934, 4-256495, and 5-220489, however, the effect of the catalyst is impaired when the surface of the catalyst is covered with an organic substance or other turbid components, and the catalyst cannot be used for a long time.

(5) Further, a water treatment technique for removing turbid components while preventing fouling derived from organic substances on the film surface by performing ozone oxidation treatment and removing turbid components by the membrane is disclosed in Japanese Patent Application Laid-Open No. HEI 9-163568. Although it is disclosed in Japanese Patent Application Laid-Open No. 7-265671, it is necessary to add an activated carbon treatment step at a later stage in order to remove the decomposed low molecular weight organic substances in the same manner as in the above (3).

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing higher quality water by a simpler system, eliminating the disadvantages present in each of the above water treatment methods. And

[0009]

Means for Solving the Problems The present invention is as follows. 1) A method for purifying water using ozone oxidation, wherein turbidity by membrane filtration and promotion of ozone oxidation reaction by a catalyst are combined. 2) After mixing ozone gas into the water to be treated, turbidity is removed by membrane filtration, and the filtered water is passed through a catalyst that promotes an ozone oxidation reaction. Purification method.

3) The ozone gas is mixed into the water to be treated, the water is passed through a catalyst for accelerating the ozone oxidation reaction, and then the turbidity is removed by membrane filtration.
The method for purifying water according to the above. 4) Purification of water according to 1) above, wherein the water to be treated is made turbid by membrane filtration, ozone gas is mixed into the filtered water, and the water is passed through a catalyst that promotes an ozone oxidation reaction. Method.

5) After the ozone gas is mixed into the water to be treated, turbidity is removed by membrane filtration.
The method for purifying water according to 1), wherein ozone gas is mixed and water is passed through a catalyst that promotes an ozone oxidation reaction. 6) After the ozone gas is mixed into the water to be treated, water is passed through a catalyst that promotes the ozone oxidation reaction, the ozone gas is further mixed into the treated water, and turbidity is removed by membrane filtration. The method for purifying water according to the above 1).

A method for purifying water constituted by any one of the above-mentioned flows 1) to 6). Here, 2) ~
The flow of 6) will be described in further detail below. The flow of 2) is a flow suitable for the case of water having a large amount of turbid components and organic substances. First, ozone gas is injected to convert high molecular organic compounds such as humic acid and fulvic acid into low molecules. It decomposes, kills protozoa, kills bacteria, and inactivates viruses. Adhesive substances that cover the surface of the turbid component and / or aggregate the turbid component (high molecular organic compounds, protozoa / bacteria) by reducing the molecular weight of organic substances, killing protozoa, and sterilizing bacteria By removing the metabolites, etc.), fouling on the surface of the filtration membrane is slight, and filtered water can be collected at a high level.

Next, by passing the filtered water in which ozone is dissolved through a catalyst that promotes the ozone oxidation reaction, the low-molecular-weight organic compound is further decomposed into low-molecular-weight organic substances. High quality water is obtained. Here, since the water from which the turbid components have been removed is passed through the catalyst by the filtration membrane, the activity of the catalyst is maintained for a long period of time without contamination of the surface of the catalyst.

The flow of 3) is a flow suitable for raw water having a relatively small amount of turbid components and a large amount of organic matter. First, by injecting ozone gas, high flow such as humic acid and fulvic acid can be obtained. It decomposes molecular organic compounds into low molecules, kills protozoa, kills bacteria, and inactivates viruses. Further, by passing water through a catalyst that promotes an ozone oxidation reaction, an oxidative decomposition reaction of organic substances is promoted, and water containing only an extremely low molecular weight organic compound and a turbid component is obtained. This water is passed through a filtration membrane to remove turbid components.

The flow of 4) is a flow suitable for raw water having a small content of turbid components and organic substances,
The turbid components are removed by the filtration membrane, and the ozone gas is injected into the filtered water to decompose organic substances in the filtered water from high molecular weight compounds to low molecular weight compounds. Furthermore, by passing water through a catalyst that promotes the ozone oxidation reaction, the low-molecular-weight organic substance is further converted to a low-molecular-weight organic compound.

The flow 5) is a flow suitable for raw water having a large amount of turbid components and very large amounts of organic matter. First, an ozone gas is injected to obtain a high flow such as humic acid or fulvic acid. It decomposes molecular organic compounds into low molecules, kills protozoa, kills bacteria, and inactivates viruses. Adhesive substances (high molecular weight organic compounds, protozoa, etc.) that covered the surface of the turbid component and / or aggregated the turbid component due to the reduction of the molecular weight of the organic material, the death of the protozoa, and the sterilization of bacteria By removing the metabolites of bacteria, fouling on the surface of the filtration membrane is minimal, and filtered water can be collected at a high level. Furthermore, by injecting ozone gas, the dissolved ozone consumed in the above sterilization, decomposition, etc. is replenished, and furthermore, by passing water through a catalyst that promotes ozone oxidation, an extremely small amount of organic compounds remaining without being decomposed can be obtained. Organic acids, polyhydric alcohols and / or peroxides thereof,
Oxidizes and decomposes to carbon dioxide.

The flow of 6) is a flow suitable for raw water quality when there are few turbid components and very much organic matter,
First, by injecting ozone gas, high-molecular organic compounds such as humic acid and fulvic acid are decomposed into low molecules, and at the same time, protozoa are killed, bacteria are killed, and viruses are inactivated. At this time, the effect of ozone oxidation is enhanced by passing water through a catalyst that promotes ozone oxidation. After that, by injecting ozone gas further, the component of the supply water supplied to the filtration membrane becomes only a turbid component, and by supplying to the filtration membrane, fouling on the surface of the filtration membrane can be prevented, and high level It becomes possible to collect the filtered water at the same time.

Here, except for the flow of 4), the filtration membrane used is preferably made of a material having ozone resistance. Furthermore, even in the case of 4), in order to completely prevent the contact of the ozone-containing water with the ozone-containing water, ozone is adsorbed in the middle or converted into oxygen so that there is no problem even if the ozone-containing water flows back to the filtration membrane. It is preferable to provide such a treatment layer, and in terms of simplification of the system, application of a filtration membrane having ozone resistance is preferable.

The filtration membrane in the present invention is not particularly limited as long as it is a filtration membrane capable of removing turbid components, for example, a microfiltration membrane or an ultrafiltration membrane. Is preferably formed. More specifically, the pore diameter of the membrane is preferably 1 μm or less, more preferably 0.1 μm, made of ceramic, sintered metal, ethylene tetrafluoride polymer resin, perfluoroalkyl vinyl ether polymer resin, vinylidene fluoride polymer resin, or the like. 01-0.45
μm microfiltration membrane or fractional molecular weight 1000-20
10,000 dalton ultrafiltration membrane, hollow fiber, spiral,
It is formed into a tubular or flat membrane, assembled into a filtration membrane module, and used.

The catalyst used in the present invention is not particularly limited as long as it promotes the oxidation / decomposition reaction of organic substances by ozone injected into raw water, but examples thereof include JP-A-2-174934 and JP-A-2-174934. 4-256495, 5-220
489, 6-114387, titanium, silicon, aluminum, zirconium, tungsten,
Iron, zinc, tin, magnesium, manganese, nickel,
Cobalt, calcium, cerium, strontium, iridium, indium, ruthenium, barium, rhodium, copper, oxides such as silver, halides and sulfides, platinum, palladium and or its oxides, and gold alone, compound, and And / or it can be used as a mixture.

The catalyst used in the present invention may be a powder, but it can be used more easily by being formed into a pellet, a pipe, a thin plate, or a honeycomb. Become. Further, the efficiency of the reaction may be further improved by irradiating sunlight or ultraviolet rays during the passage of water into the reaction promoting catalyst.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail by way of examples.

[0023]

Embodiment 1 An outer diameter of 2.0 mm and an inner diameter of 1.0 mm were prepared by the method disclosed in JP-A-3-215535.
1 mm, porosity 66%, ratio of average pore diameter of outer surface to average pore diameter of membrane cross section 1.75, average pore diameter of inner surface from average pore diameter of outer surface, inner surface and membrane cross section calculated by electron micrograph And the average pore diameter of the membrane cross section is 0.85, the average pore diameter by the air flow method is 0.25 μm, the maximum pore diameter by the bubble point method is 0.35 μm, and the ratio of the maximum pore diameter to the average pore diameter is 1. 4 and the water permeability is 240
A vinylidene fluoride polymer resin hollow fiber microfiltration membrane having 0 liter / m 2 · hr · 100 KPa (25 ° C.), a breaking strength of 15 MPa and a breaking elongation of 280% was prepared.

The above membrane has a length of 300 mm, and the both ends of the five hollow fiber membranes are U-shaped as shown in FIG. 7 on end plates to which ten stainless steel pipes are welded and fixed. And fixed. This was mounted in a filtration tank of an evaluation device, as shown in FIG. 1, which was constituted by a raw water tank, a pressure pump, a filtration tank, a packed tower filled with an oxidation reaction promoting catalyst, and a product water tank. The packed tower was filled with a titanium-zirconium oxide / platinum pellet catalyst. Secondary treated sewage water was used as feed water.

The raw water is supplied to the raw water tank,
gO ₃ / liter as a concentration, pressure pump - was injected ozone gas from the middle piping between the filtration tank containing filtration membranes. The entire amount of the raw water mixed with the supplied ozone gas was filtered by a microfiltration membrane, and the filtered water was supplied to a packed tower and held in a product water tank.

Next, (a) raw water, (b)
Water supplied to the microfiltration membrane, (c) water supplied to the packed tower,
(D) Water in the product water tank was sampled, and the dissolved ozone concentration, chromaticity, turbidity, and viable cell count of each sample water were measured. Here, the dissolved ozone concentration, chromaticity, turbidity, and viable cell count were measured by the measurement methods described in the water purification test method (supervised by the Ministry of Health and Welfare, Health Service Bureau, Water Environment Department, issued by Japan Water Works Association). The results are shown in Table 1.

[0027]

Example 2 Sample water was collected from each part under the same conditions as in Example 1 except that the flow of the evaluation apparatus was as shown in FIG. The dissolved ozone concentration, chromaticity, turbidity, and viable cell count of each sample water were measured in the same manner as in Example 1. Table 1 shows the results.

[0028]

Example 3 Sample water was sampled from each part under the same conditions as in Example 1 except that the flow of the evaluation apparatus was as shown in FIG. The dissolved ozone concentration, chromaticity, turbidity, and viable cell count of each sample water were measured in the same manner as in Example 1. Table 1 shows the results.

[0029]

EXAMPLE 4 The flow of the evaluation apparatus was as shown in FIG. 4, and ozone gas was injected between the raw water tank and the pressurizing pump and between the filtration water on the filtration tank side and the packed tower so as to be 5 mg O ₃ / liter. Under the same conditions as in Example 1, sample water was collected from each site. Dissolved ozone concentration, chromaticity, turbidity,
The number of viable bacteria was measured in the same manner as in Example 1. Table 1 shows the results.

[0030]

EXAMPLE 5 The flow of the evaluation apparatus was as shown in FIG. 5, and ozone gas was injected into the pressure pump-to-packing tower and the packing tower-to the side into the filtration tank so that the amount became 5 mg O ₃ / liter. Under the same conditions as in Example 1, sample water was collected from each site. The dissolved ozone concentration, chromaticity, turbidity, and viable cell count of each sample water were measured in the same manner as in Example 1. Table 1 shows the results.

[0031]

Example 6 Sample water was collected from each site under the same conditions as in Example 1 except that the oxidation reaction promoting catalyst packed in the packed tower was changed to titanium-silicon oxide / palladium. The dissolved ozone concentration, chromaticity, turbidity, and viable cell count of each sample water were measured in the same manner as in Example 1. Table 2 shows the results.

[0032]

Example 7 Sample water was sampled from each part under the same conditions as in Example 1 except that the oxidation reaction promoting catalyst filled in the packed tower was changed to iron-copper oxide. The dissolved ozone concentration, chromaticity, turbidity, and viable cell count of each sample water were measured in the same manner as in Example 1. Table 2 shows the results.

[0033]

Example 8 The same vinylidene fluoride polymer resin hollow fiber microfiltration membrane as used in Example 1, JP-A-7-26567
No. 1 discloses a silicone rubber having excellent ozone resistance (weight average molecular weight of base polymer before curing: 2)
Japanese Patent Application Laid-Open No. Hei 7-265, which is composed of a module case made of rigid polyvinyl chloride (JIS-A hardness: 45) according to the method of measuring JIS K6301 after curing.
A microfiltration membrane module having the structure shown in FIG.

Next, the above-mentioned membrane module was installed after the pressurizing pump in an evaluation device as shown in the flow of FIG. 6, which was composed of a raw water tank, a pressurizing pump, a packed tower, and a drainage tank. The raw water to be supplied was river water having a turbidity of 2 to 10, and the packed tower was filled with a short pipe-shaped catalyst of iron-copper oxide. Ozone gas was injected from two pipes between the pressure pump and the membrane module and between the membrane module and the packed tower. In addition, the ozone concentration is 3mgO
_{At 3} / liter, ozone-containing air was injected by aeration so that the ozone concentration was 5 mg O ₃ / liter.

Further, every 10 minutes of the filtration operation, backwashing was performed for 15 seconds. Here, (a) raw water, (b) water supplied to the microfiltration membrane, (c) water supplied to the packed tower, and (d) water in the filtrate tank at the outlet of the packed tower were measured every 50 hours. Water is sampled three times, and the dissolved ozone concentration, chromaticity, turbidity,
The number of viable bacteria was measured in the same manner as in Example 1. Table 3 shows the results.

FIG. 8 shows that the water permeability of the membrane module during the evaluation was changed, and the water permeability when the pressure was kept constant is set to 100 at the start of the evaluation.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

[Table 3]

[0040]

According to the present invention, it is possible to remove organic matter and turbid components in water at a high level, and to purify and recycle water supply, sewerage, industrial water / process water, and pretreatment of ultrapure water production. Applicable.

[Brief description of the drawings]

FIG. 1 is a diagram of a flow used in Examples 1, 6, and 7.

FIG. 2 is a diagram of a flow used in Example 2.

FIG. 3 is a flow chart used in Example 3.

FIG. 4 is a flow chart used in Example 4.

FIG. 5 is a diagram of a flow used in Example 5.

FIG. 6 is a diagram of a flow used in Example 8.

FIG. 7 is a diagram of a simple filtration membrane cartridge used in Examples 1 to 7.

FIG. 8 is a graph showing the change over time in the water permeability retention rate of the membrane module used in Example 8.

[Explanation of symbols]

 Reference Signs List 1 Raw water tank 2 Pressure pump 3 Filtration tank including filtration membrane 4 Ozone gas generator 5 Packing tower filled with ozone oxidation reaction promoting catalyst 6 Product water tank 7 Filtration membrane module 8 Drain nozzle (a) Raw water sampling port (b) ) Sampling port of supply water to filtration membrane (c) Sampling port of supply water to catalyst packed tower (d) Sampling port of product water

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C02F 9/00 504 C02F 9/00 504B 504E

Claims (6)

[Claims] 1. A method for purifying water using ozone oxidation, wherein turbidity by membrane filtration and promotion of ozone oxidation reaction by a catalyst are combined. 2. After mixing ozone gas into the water to be treated,
2. The method according to claim 1, wherein turbidity is removed by membrane filtration, and the filtered water is passed through a catalyst that promotes an ozone oxidation reaction.
The method for purifying water according to the above. 3. An ozone gas is mixed into the water to be treated, and the water is passed through a catalyst that promotes an ozone oxidation reaction.
The method for purifying water according to claim 1, wherein turbidity is removed by membrane filtration. 4. The method according to claim 1, wherein the water to be treated is made turbid by membrane filtration, ozone gas is mixed into the filtered water, and the water is passed to a catalyst that promotes an ozone oxidation reaction.
The method for purifying water according to the above. 5. After mixing ozone gas into the water to be treated,
The water purification method according to claim 1, wherein turbidity is removed by membrane filtration, and the filtered water is further mixed with ozone gas and passed through a catalyst that promotes an ozone oxidation reaction. 6. After mixing ozone gas into the water to be treated,
Water is passed through a catalyst that promotes the ozone oxidation reaction, and the treated water is further mixed with ozone gas.
The water purification method according to claim 1, wherein turbidity is removed.