JP2012217944A - Method and apparatus for treating clean water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating clean water capable of simply and stably obtaining clean water by which the concentration of manganese is reduced further than usual from city raw water and an apparatus for treating clean water.SOLUTION: In the method for treating clean water, treated water obtained by water conduction treatment of the city raw water into a catalytic manganese oxidation reactor is filtrated by a membrane the pore size of which is 0.01 μm or larger and 0.08 μm or smaller to obtain clean water. In the method for treating clean water, coagulation treated water obtained by coagulation treatment of treated water obtained by conduction treatment of the city raw water into the catalytic manganese oxidation reactor is filtrated by the membrane the pore size of which is 0.01 μm or larger and 0.08 μm or smaller to obtain clean water. The apparatus for treating clean water includes a membrane filtration device having the catalytic manganese oxidation reactor in which the city raw water is subjected to water conduction treatment to obtain treated water and the membrane the pore size of which is 0.01 μm or larger and 0.08 μm or smaller by which the treated water is filtrated to obtain clean water. The apparatus for treating clean water includes a membrane filtration device having the catalytic manganese oxidation reactor in which the city raw water is subjected to water conduction treatment to obtain treated water, the coagulation treatment device by which the treated water is subjected to coagulation treatment to obtain the coagulation treated water, and the membrane the pore size of which is 0.01 μm or larger and 0.08 μm or smaller by which the coagulation treated water is filtrated to obtain clean water.

Description

  The present invention relates to a water purification method and water purification apparatus for raw water.

Manganese may be contained in groundwater or river water that is raw water supply. Manganese in natural water exists mainly as soluble divalent manganese ions (Mn ²⁺ ), but when manganese ions are oxidized, they become black-brown oxides and exhibit high chromaticity even in trace amounts. Or cause so-called black water. As such a method for water purification treatment of manganese-containing water, a contact filtration manganese removal method has been conventionally known (Non-Patent Document 1).

This manganese removal by contact filtration is a method in which chlorine is continuously added to raw water containing soluble manganese, and water is passed downward through a filtration tower packed with manganese dioxide, so-called “manganese sand”. It is a method to do. The divalent manganese ions are oxidized by manganese dioxide hydrate adhering to the filter medium as a catalyst, and are removed by binding to the manganese sand surface as manganese dioxide hydrate.
Since this contact filtration removal manganese method is a method of oxidizing and precipitating manganese in raw water and removing it with a packed bed of manganese sand together with turbidity components, in order to ensure the removal rate of manganese and turbidity components, the filtration rate must be increased. It must be about 150m / day. For this reason, a relatively large water tank is required, and when the raw water turbidity rises, such as during rainfall, it must be frequently washed to prevent clogging of the packed bed and maintain the filtered water quality.
In recent years, as a countermeasure against pathogenic microorganisms such as Cryptosporidium, the turbidity of filtered water has to be kept below 0.1 degree, and it is difficult to manage the operation such as slow start, slow down and introduction of waste water process. It has become to.

Therefore, in recent years, while adding chlorine to raw water containing manganese, water is passed through the packed bed of manganese dioxide catalyst particles in an upward flow, and the packed bed passing water is filtered through a ceramic MF membrane. A water purification method for separating oxidized and insolubilized manganese particles has been devised (Patent Document 1).
In this method, the packed bed is always in a fluidized state because water flows at a relatively high filtration rate in an upward flow. Oxidized insolubilized manganese particles and turbidity components pass through the packed bed as they are. Does not occur.
Moreover, since the MF membrane is used in the final stage, the operation management is easy, and the turbidity management and pathogenic microorganisms are almost complete barriers.

Japanese Patent No. 3705590

Supervision of Ministry of Health and Welfare “Water Supply Facility Design Guidelines 2000” Japan Waterworks Association, 5.6 Rapid Filtration Tank, and 5.17 Iron and Manganese Removal Equipment

The current tap water quality standard for manganese is 0.05 mg / L or less. However, in the water service enterprise, from the viewpoint of facility management including black water countermeasures, it is about 1/5 to 1/10 of the tap water quality standard. In many cases, 005 to 0.01 mg / L is set as the target treated water quality.
However, with respect to manganese, the target value of the water quality management target setting item is set to 0.01 mg / L or less together with the water quality standard, and the detection limit has been improved due to recent advances in analytical instruments, and a more advanced facility maintenance management system has been established. From the standpoint of consumers who want safe, secure and delicious water, there are some enterprises whose target treated water quality is less than 1/10 of the water quality management target setting item and less than 0.001 mg / L. This tendency is seen in relatively large water treatment plants with a large water supply population.
The combination of the upflow type manganese contact tower and the MF membrane is an excellent water purification system from the viewpoint of high-speed treatment, turbidity component removal, and pathogenic microorganism removal. However, although the target treated water quality of 0.005 to 0.01 mg / L, which has been widely used in the past, is satisfactory, there is a problem that it cannot be stably achieved when a value less than that is targeted.

  The present invention has been made in view of such problems, and its purpose is to provide a water purification treatment method and a water purification treatment apparatus capable of easily and stably obtaining purified water having a manganese concentration further reduced from conventional tap water. There is to do.

The present invention is as follows.
1) A water purification treatment method for obtaining purified water by filtering treated water obtained by passing raw water from a tap water through a manganese catalytic oxidation reactor through a membrane having a pore size of 0.01 μm or more and 0.08 μm or less.
2) Purified water is obtained by filtering the agglomerated treated water obtained by aggregating the treated water obtained by passing the raw water from the tap water through a manganese catalytic oxidation reactor through a membrane having a pore size of 0.01 μm or more and 0.08 μm or less. Processing method.
3) Manganese catalytic oxidation reactor for obtaining treated water by passing raw water through water, and a membrane having a membrane with a pore diameter of 0.01 μm or more and 0.08 μm or less for filtering the treated water to obtain purified water Water purification equipment including filtration equipment.
4) Manganese contact oxidation reactor for obtaining treated water by passing raw water through water, a coagulation treatment device for coagulating the treated water to obtain agglomerated treated water, and filtering the agglomerated treated water A water purification apparatus comprising a membrane filtration device having a membrane having a pore diameter of 0.01 μm or more and 0.08 μm or less for obtaining purified water.

In the present invention, it is an important technical idea that a membrane having a pore diameter of 0.01 μm or more and 0.08 μm or less has not been conventionally found.
The present inventor has found that the reason why the concentration cannot be stably achieved in the conventional method is that fine manganese particles are peeled off from the surface of the filter medium of the manganese catalytic oxidation reactor. Although the size and concentration of fine manganese particles are affected by the raw water quality, filtration rate, water flow direction (downflow, upward flow), filter media type, etc., the particle size has two distributions. One is a manganese particle larger than 0.08 μm, and the other is a manganese particle smaller than 0.01 μm for the first time, and the present invention has been recalled.
If a membrane having a pore size of 0.08 μm or less can be used, the manganese concentration can be further reduced as compared with the conventional case, but if the pore size is smaller than 0.01 μm, the water permeability of the membrane is extremely lowered in most cases. From the viewpoint of reducing filtration pressure and power cost, a membrane having a pore size of 0.01 μm or more was practical and adopted.

The present inventor also agglomerated fine manganese particles smaller than 0.01 μm by using agglomeration treatment together, and as a result of earnestly searching for the pore size of the membrane that can separate these agglomerated particles, Although it is not satisfactory with a membrane having a pore diameter of 0.1 μm, it has been found that it can be achieved even when the target treated water quality is less than 0.001 mg / L by using a membrane with a pore diameter of 0.08 μm or less. It was.
In the present invention, as described above, if the membrane has a pore diameter of 0.01 μm or more and 0.08 μm or less, it can be used without agglomeration treatment to achieve a manganese concentration lower than the conventional one. The combined use is preferable from the viewpoint of reduction.

Specifically, in tap raw water, organic substances that cause membrane contamination may exist with a wide molecular weight distribution, but the influence is relatively large. It is.
The pore diameter of the membrane used in the present invention is 0.01 μm or more and 0.08 μm or less, which is in the same range as the size of the high molecular organic substance, which causes membrane clogging.
In the present invention, since the high molecular organic substance can be removed by agglomeration treatment, it is better to use agglomeration treatment together from the viewpoint of reducing film contamination.

  In the present invention, the pore size of the membrane means a pore size generally used in the field of water treatment, and is provided by, for example, a membrane manufacturer. Moreover, there is no restriction | limiting in particular as a shape of a film | membrane, A hollow fiber, a flat film, etc. are mentioned.

In the present invention, a manganese contact oxidation reactor, an agglomeration treatment device, and a membrane filtration device, if necessary, are appropriately connected in this order to pipes, valves, pumps, etc. Accordingly, the flocculated water is configured to be sequentially transferred.
The processing flow may be automatic control, batch processing, or a combination thereof.

  The present invention can obtain easy operation controllability and safety that are not inferior to conventional methods, and can obtain tap water that is clearer than conventional water purification treatment.

Hereinafter, the present invention will be described in detail.
In the present invention, the raw water supply is surface water, lake water, underground water, well water, spring water, etc., the manganese concentration is at least 0.001 mg / L or more, and the upper limit is usually about 2 to 3 mg / L. Means something.

In the present invention, raw tap water is subjected to water treatment in a manganese catalytic oxidation reactor to obtain treated water from which manganese ions have been removed.
The present invention is not particularly limited to the manganese catalytic oxidation reactor and the type of filter medium used therefor. As the filter medium, manganese sand to which amorphous manganese dioxide is attached is of course applicable, and a special filter medium to which manganese dioxide having a β-type crystal structure is attached may be used. Moreover, there is no limitation in particular also in the kind of base material of a filter medium, Any of sand, a chamonet, and a ceramic may be sufficient.

  The manganese catalytic oxidation reactor used in the present invention is not essentially restricted in the direction of water flow (downflow, upflow, etc.). When the water flow rate is not fast in the downward flow, the production of fine manganese particles tends to be less, so the manganese concentration of the treated water in the reactor tends to be lower than that in the upward flow. When the water speed increases, the production of fine manganese particles tends to increase, so that the manganese concentration tends to increase from the above.

In the present invention, a case will be described in which treated water obtained by passing water through a manganese catalytic oxidation reactor is filtered through a membrane having a pore diameter of 0.01 μm or more and 0.08 μm or less without agglomeration treatment.
The treated water is filtered with a membrane having a pore size of 0.01 μm or more and 0.08 μm or less, and purified water having a manganese concentration reduced as compared with the prior art can be obtained.
In the present invention, the filtration treatment using the membrane is hereinafter referred to as a membrane filtration treatment, and the device for performing the filtration treatment using the membrane is referred to as a membrane filtration device.

Next, in the present invention, a case where the treated water obtained by passing water through the manganese catalytic oxidation reactor is subjected to agglomeration treatment will be described.
In the present invention, the agglomerated water means water obtained by agglomeration treatment of treated water that has been subjected to water treatment using a manganese catalytic oxidation reactor. The agglomeration treatment is a treatment in which a flocculant is added to the treated water to produce agglomeration floc. The agglomerated water may contain agglomerated floc or may have agglomerated floc removed.
The agglomeration treatment for obtaining the agglomerated water may be performed by using an agglomeration apparatus, a membrane filtration apparatus provided with the membrane of the present invention, or both.
The agglomerated water is filtered through a membrane having a pore size of 0.01 μm or more and 0.08 μm or less, and purified water having a manganese concentration of less than 0.001 mg / L can be stably obtained.

The membrane filtration device used in the present invention is not particularly limited to the type and shape of the membrane module, but an immersion type membrane filtration device is preferred. In a conventional apparatus using a casing-type membrane module, turbid components and manganese dioxide particles are likely to accumulate on the membrane surface, and when the concentration of turbid components in tap raw water rises due to rain, etc., the flow path of the membrane is blocked. It may occur and the membrane filtration device may not be operated.
The submerged membrane filtration device has a shape that can hold a high concentration of SS component, and since it can operate stably even if the concentration of turbid components in raw tap water is increased, it performs coagulation treatment. More preferred in some cases.
The submerged membrane filtration device can retain high-concentration flocs generated by the agglomeration treatment, and even if the concentration of fine manganese particles increases rapidly due to fluctuations in the manganese concentration of raw tap water, they are taken into the flocs This is advantageous because it can be handled. For example, incorporation of fine manganese particles into agglomeration floc can cope with leakage of fine manganese particles from an aggregating treatment apparatus provided as necessary. In addition, the submerged membrane filtration apparatus is more preferable because aggregation of the fine manganese particles themselves is promoted in the apparatus.

The present invention is not particularly limited to the membrane material used for the membrane filtration treatment as long as the pore diameter is satisfied, and inorganic membranes and organic membranes can be used. Molecular membranes are preferred.
In the said patent document 1, although the ceramic membrane is used as a membrane of a membrane filtration apparatus, the surface of a ceramic membrane has a positive charge, and it is easy to adsorb | suck the organic substance in the tap water which has a negative charge, and membrane contamination Since this tends to occur, there is a difficulty in maintenance. On the contrary, the organic polymer film has an advantage that the film surface has a negative charge, film contamination hardly occurs, and maintenance is easy.
Such an organic polymer film is not limited to any material, but it is more preferable that the film surface is a hydrophobic film because it is less susceptible to film contamination by the flocculant. Examples of the organic polymer include polyethylene, polyvinylidene fluoride, polyvinyl chloride, polysulfone, polyether sulfone, and polytetrafluoroethylene.

  The injection rate of the flocculant in the flocculation treatment of the present invention varies depending on the properties of the raw water of the tap water and the type of the flocculant, and therefore needs to be evaluated in the field or in advance experiments. In some cases, approximately 30 mg / L or less is preferable, and even when the organic matter concentration is high and a large injection rate is required, approximately 30 to 60 mg / L is preferable. Also, it does not matter if the pH during the agglomeration treatment is adjusted by injecting acid such as sulfuric acid.

  The flocculant is charged by the flocculant charging device provided in the flocculant treatment device when the flocculant treatment device is used. It is charged by a flocculant charging device provided in piping between the devices. The aggregation treatment device and the membrane filtration device can be appropriately equipped with a stirring device. In addition, the aggregation processing apparatus may include a device (for example, a centrifugal device, a screen device, or the like) that separates the aggregation floc. Moreover, the membrane filtration apparatus may be equipped with an air diffuser for cleaning the membrane.

  Examples of the present invention will be described below. In addition, this invention is not restrict | limited at all by this Example.

Example 1 and Comparative Example 1
A tap water (raw water) having a manganese (Mn) concentration of 0.021 mg / L is passed through a manganese contact oxidation reactor (Mn tower) having manganese sand as a filter medium at a linear velocity (LV) of 1400 m / day (through water treatment ( Membrane filtrate was obtained from the treated water (upstream Mn treatment) (removed Mn tower treated water) with a membrane having a pore size of 0.1 μm, 0.08 μm, 0.03 μm, or 0.01 μm.
The membrane is made of polyvinylidene fluoride (PVDF). An ICP (inductively coupled plasma emission analyzer) was used for the measurement of the manganese concentration of raw water, removed Mn tower treated water, agglomerated treated water described later, and membrane filtered water (lower limit of quantification 0.001 mg / L). The pore diameter of the membrane is shown in the column of Mn concentration of membrane filtrate in Table 1.
In addition, since the manganese concentration of raw water and manganese removal tower treated water was measured by filtration through a 0.1 μm membrane filter, the maximum size of manganese particles was less than 0.1 μm, and an ICP (inductively coupled plasma emission spectrometer) was used. ).
Table 1 shows the type of the filter medium of the Mn tower, the above-described treatment flow, the Mn tower LV, the PACl injection rate, the manganese concentration of each water, and the manganese concentration of the membrane filtration water.
Example 2 and Comparative Example 2
In Example 1 and Comparative Example 1, purified water was obtained in the same manner as Example 1 and Comparative Example 1 except that the raw water concentration was changed.
Examples 3-4, Comparative Examples 3-4
In Example 1 and Comparative Example 1, purified water was obtained in the same manner as in Example 1 and Comparative Example 1 except that the treatment flow (upward flow into downward flow), the Mn tower LV, and the raw water concentration were changed.

Example 5, Comparative Example 5
Raw water with a Mn concentration of 0.020 mg / L was flowed upward into a Mn tower having manganese sand as a filter medium, and the treated Mn tower treated water treated with Mn with an upward flow of LV 1400 m / day was injected with 30 mg / L of PACl. The agglomerated water obtained by aggregating at a rate was subjected to membrane filtration with a membrane having a pore size of 0.1 μm, 0.08 μm, 0.03 μm, or 0.01 μm to obtain membrane filtered water.
The measurement of the type of membrane and the manganese concentration of raw water, Mn removal tower treated water, agglomerated treated water, and membrane filtered water was the same as in Example 1, and the results are shown in Table 1. Further, the manganese concentration of the flocculated water was measured by removing the flocculated floc with a 0.1 μm membrane filter.

Example 6 and Comparative Example 6
In Example 5 and Comparative Example 5, purified water was obtained in the same manner as Example 5 and Comparative Example 5 except that the raw water concentration was changed.
Example 7 and Comparative Example 7
In Example 5 and Comparative Example 5, purified water was obtained in the same manner as Example 5 and Comparative Example 5 except that the filter medium and raw water concentration were changed. As the filter medium, a special filter medium to which manganese oxide having a β-type crystal structure was attached was used.
Example 8 and Comparative Example 8
In Example 6 and Comparative Example 6, purified water was obtained in the same manner as in Example 6 and Comparative Example 6 except that the treatment flow (upward flow into downward flow) and the Mn tower LV were changed.
The above results are shown in Table 1 below.

  From Table 1, when a membrane having a pore size of 0.01 μm or more and 0.08 μm or less is used, purified water having a manganese concentration of less than 0.005 mg / L can be obtained regardless of the presence or absence of the agglomeration treatment. It can be seen that purified water having a manganese concentration of less than 0.001 mg / L can be stably obtained by carrying out the agglomeration treatment even when a 08 μm membrane is used.

Claims (6)

  A water purification method for obtaining purified water by filtering treated water obtained by passing raw water from a tap water through a manganese catalytic oxidation reactor through a membrane having a pore size of 0.01 μm or more and 0.08 μm or less.   A purified water treatment method for obtaining purified water by filtering the agglomerated treated water obtained by aggregating treated water obtained by passing raw water through a manganese contact oxidation reactor through a membrane having a pore size of 0.01 μm or more and 0.08 μm or less .   The water purification method according to claim 1 or 2, wherein the membrane is an organic polymer membrane.   Manganese contact oxidation reactor for obtaining treated water by passing raw water through water, and a membrane filtration device having a membrane having a pore diameter of 0.01 μm or more and 0.08 μm or less for filtering the treated water to obtain purified water Including water purification equipment.   A manganese contact oxidation reactor for obtaining treated water by passing raw water through water, a coagulation treatment device for obtaining coagulated treated water by coagulating the treated water, and filtering the coagulated treated water to obtain purified water A water purification apparatus comprising a membrane filtration apparatus having a membrane having a pore diameter of 0.01 μm or more and 0.08 μm or less for obtaining.   The water purification apparatus according to claim 4 or 5, wherein the membrane is an organic polymer membrane.