JP6737583B2 - Water treatment device, ultrapure water production device and water treatment method - Google Patents

Description

The present invention relates to a water treatment device, an ultrapure water production device, and a water treatment method.

Generally, an ultrapure water production system for producing ultrapure water from raw water such as city water, well water, groundwater, and industrial water is often composed of a pretreatment device, a primary pure water system, and a secondary pure water system. .. Among them, the pretreatment device is composed of, for example, a coagulation-sedimentation device, a pressure flotation device, a filtration device, etc., and removes suspended matter in the raw water. The primary pure water system is configured by combining, for example, a degassing device, a reverse osmosis membrane device, an ion exchange device, an ultraviolet oxidation device, etc., and organic substances, ionic components, dissolved gases, etc. in pretreatment water treated by the pretreatment device. Are removed to produce primary pure water. The secondary pure water system is composed of, for example, an ultraviolet oxidation device, a mixed-bed ion exchange device, an ultrafiltration device, and the like, and treats trace impurities in the primary pure water produced by the primary pure water system. Produce high-purity ultrapure water.

In recent years, ultrapure water has been extremely required to improve its purity, and accordingly, removal of total organic carbon (TOC) components is required. Of the TOC components in ultrapure water, urea is particularly difficult to remove because it has a small molecular weight and is difficult to ionize. Therefore, the content of urea in the TOC component increases as the TOC component in the ultrapure water decreases. Therefore, in order to highly reduce the TOC in the ultrapure water, it is required to remove urea as much as possible from the water supplied to the ultrapure water production apparatus.

As a method of removing urea, Patent Document 1 discloses a method of decomposing urea by biological treatment, in which urea or a urea derivative and/or an ammoniacal nitrogen source is added to raw water, and then biological treatment is performed. ing.

However, in the method of performing biological treatment by adding urea, it may be difficult to control the amount of urea added, and thus urea may remain. Further, if an ammoniacal nitrogen source is added, this ammoniacal nitrogen may not be removed, which may lead to deterioration of the film or resin arranged on the downstream side of the ultrapure water production system. Further, it may not be suitable for producing ultrapure water because, for example, a device for removing ammoniacal nitrogen needs to be arranged on the downstream side.

International publication 2011/135942

The present invention has been made to solve the above problems, and an object of the present invention is to provide a water treatment apparatus and a water treatment method capable of easily and highly removing urea in water.
It is another object of the present invention to provide an ultrapure water production apparatus capable of easily obtaining highly pure ultrapure water having an extremely low TOC concentration by highly removing urea.

The water treatment apparatus of the present invention is a water treatment apparatus for biologically treating raw water, which comprises a water-insoluble polymer having an amino group immobilized and a water-insoluble polymer having the amino group immobilized, which is brought into contact with the raw water. A bioactive carbon that treats the raw water contacted with a volatile polymer.

In the water treatment device of the present invention, the amino group is preferably a quaternary ammonium group.

In the water treatment apparatus of the present invention, the water-insoluble polymer having the amino group immobilized thereon and the bioactive carbon are mixed beds in which the water-insoluble polymer having the amino group immobilized therein and the bioactive carbon are mixed. Alternatively, it is preferably a double bed in which the water-insoluble polymer having the amino group immobilized thereon is laminated on the upstream side of the biological activated carbon.

In the water treatment device of the present invention, the ratio of the water-insoluble polymer having the amino group immobilized thereto and the bioactive carbon is represented by the water-insoluble polymer having the amino group immobilized/the bioactive carbon. The volume ratio is preferably 1/99 to 99/1.

In the water treatment device of the present invention, the pH of the raw water is preferably 4-9.

In the water treatment device of the present invention, the water-insoluble polymer having the amino group immobilized thereon is preferably an ion exchange fiber or an ion exchange resin having the amino group as an ion exchange group.

The ultrapure water production system of the present invention is characterized by including a primary pure water system and a secondary pure water system on the downstream side of the water treatment system of the present invention.

The water treatment method of the present invention comprises a step of bringing raw water into contact with a water-insoluble polymer having an amino group immobilized, and a step of producing the raw water brought into contact with the water-insoluble polymer having an amino group immobilized. And a step of treating with activated carbon.

According to the water treatment device and the water treatment method of the present invention, urea in water can be easily and highly removed.
According to the ultrapure water production system of the present invention, since urea is highly removed, highly pure ultrapure water having an extremely low TOC concentration can be easily obtained.

It is a block diagram showing roughly the water treatment equipment concerning a 1st embodiment. It is a block diagram showing roughly the water treatment equipment concerning a 2nd embodiment. It is a block diagram showing roughly the water treatment equipment concerning a 3rd embodiment. 1 is a block diagram schematically showing an embodiment of an ultrapure water production system of the present invention. It is a graph showing the relationship between the number of treatment days and the urea removal rate in Examples and Comparative Examples.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Water treatment device)
FIG. 1 is a block diagram schematically showing a water treatment device 1 of this embodiment. The water treatment device 1 includes a storage tank 10 that stores and supplies the raw water W, and a biological treatment device 20 that performs biological treatment. The biological treatment apparatus 20 is filled with a mixed bed in which a water-insoluble polymer having amino groups immobilized (amino group-immobilized polymer) (AP) and biological activated carbon (BAC) are mixed. The raw water W stored in the storage tank 10 is processed by the biological treatment device 20, and then supplied to, for example, a primary pure water system to produce pure water or ultrapure water.

The biological activated carbon is one in which microorganisms are carried on activated carbon, and biological treatment is performed. In general, organic matter is decomposed by oxygen (breathing) of microorganisms (biological cells) that perform biological treatment in the process of oxygen respiration, nitric acid respiration, fermentation, etc., and is gasified or taken into the body of microorganisms and removed as sludge. Further, by biological treatment, it is possible to remove nitrogen (nitrification denitrification method) and phosphorus (biological phosphorus removal method). Water treatment by such microorganisms is generally called biological treatment.

The biological activated carbon is prepared, for example, as follows. Carbon sources, phosphorus, trace metals, and inorganic salts, which are nutrient sources for microorganisms, are added to sludge containing microorganisms. If necessary, oxygen is blown in to perform aerobic treatment. Thereby, the microorganism can be cultured. Activated carbon is immersed in this activated sludge in which microorganisms have been cultured. As a result, the microorganisms are carried in the pores of the activated carbon to produce biological activated carbon. Usually, when water containing a TOC component is passed through this bioactive carbon, the TOC component in the water is removed by biological treatment of the microorganisms carried on the bioactive carbon by the above-mentioned action. In such a biological treatment, in order to maintain the activity of the microorganism, the nutrient source of the microorganism is added to the water supply as needed.

At this time, by adding ammonia nitrogen as a nutrient source to the activated sludge, it is possible to obtain a nitrifying bacteria sludge in which the nitrifying bacteria group (ammonia oxidizing bacteria group) is predominant. It is considered that this is because microorganisms other than the nitrifying bacteria group are difficult to grow in the presence of ammonia nitrogen, while the nitrifying bacteria group having ammonia resistance grows. Regarding the substance and amount of the additive other than urea or ammoniacal nitrogen, the substance and amount usually used for nitrifying bacteria culture may be used.

For example, by immersing activated carbon in the nitrifying bacteria sludge obtained above, biological activated carbon carrying a nitrifying bacteria group can be obtained. Since the nitrifying bacteria group metabolize urea, urea in water is removed by performing biological treatment with biological activated carbon supporting nitrifying bacteria.

The biological activated carbon used in the biological treatment apparatus 20 may be obtained by immersing the activated carbon in activated sludge, or the activated carbon not immersed in the activated carbon may be obtained by immersing the activated carbon in activated sludge. However, it is not limited to these methods.

The amount of nitrifying bacteria supported on the biological activated carbon can be expressed using the urea removal rate as an index. As the bioactive carbon, one that can reduce urea to preferably 0.02 μg/L or less, more preferably 0.005 μg/L or less is suitable.

The activated carbon used as the biological activated carbon is not particularly limited, and examples thereof include those produced by using coal, coconut shell, charcoal and the like as raw materials. The shape of the activated carbon is also not particularly limited, and, for example, fibrous, honeycomb, cylindrical, crushed, granular, powdery, pelletized, or the like can be used. Among them, granular or crushed activated carbon is preferable because it easily supports microorganisms. When using granular or crushed activated carbon, the particle size is preferably 0.35 to 2.0 mm, more preferably 0.42 to 1.7 mm. The particle size of activated carbon can be measured, for example, by a JIS standard sieve.

The amino group-immobilized polymer is a water-insoluble polymer in which an amino group is immobilized. In the amino group-immobilized polymer of the present invention, the amino group means a primary to tertiary amino group and a quaternary ammonium group, and further includes a group in which these are ionized to form an ammonium ion. The polymer used as the amino group-immobilized polymer is not particularly limited as long as it can immobilize the amino group and is a water-insoluble polymer. Examples of the polymer include styrene/divinylbenzene copolymer, polyvinyl alcohol, cellulose such as acetate, acrylic such as polymethacrylonitrile and polyacrylonitrile, vinyl chloride such as polyvinyl chloride and polyvinylidene chloride, nylon and the like. Various urethane polymers such as polyamide and polyurethane can be used. The form of the polymer is not particularly limited, and various forms such as a resin form, a fiber form, a film form and a block form can be used. The amino group-immobilized polymer may be used alone or in combination of two or more.

The amino group may be a primary to tertiary amino group or a quaternary ammonium group. The amino group-immobilized polymer may have one or more amino groups. Here, a primary to tertiary amino groups, respectively, _-NR, -NR 2, a group represented by -NR _3, 4 quaternary ammonium groups is a group represented by ^-N + _{R 4} (In the formula, R is a substituted or unsubstituted alkyl group which may be the same or different.).

The quaternary ammonium group is particularly excellent in terms of improving the urea removal ability by nitrifying bacteria, and then the tertiary amino group, the secondary amino group, and the primary amino group are in this order. A method for immobilizing an amino group in an amino group-immobilized polymer includes, for example, one in which an amino group is bonded to a polymer skeleton, and specifically, an amino group is present at a carbon atom or the like constituting the main chain or branch of the polymer. Those linked are preferred. In order to further improve the urea removal performance, it is more preferable that an amino group is bonded to a carbon atom forming a branch.

Examples of R in the primary to tertiary amino group or quaternary ammonium group include alkyl groups such as methyl group, ethyl group and butyl group, and hydroxyalkyl groups such as hydroxymethyl group, hydroxyethyl group and hydroxybutyl group.

Specifically, as the polymer for fixing the amino group, it is preferable to use an ion exchange fiber or an ion exchange resin having the amino group as an ion exchange group. Since these have a large surface area inside, the contact area with the water to be treated can be increased. Also, the amount of amino groups per unit volume is large. By these, the removal efficiency of urea can be improved. Furthermore, since the amount of eluate is small, it does not adversely affect the quality of treated water. Therefore, it is preferably used for the purpose of highly removing impurities such as production of ultrapure water.

The amount of the amino group contained in the amino group-immobilized polymer is preferably 0.01 mol/L to 10 mol/L, and is 0.5 mol/L to 5 mol in terms of a molar amount per unit volume of the amino group-immobilized polymer. /L is more preferable. When the amount of the amino group is 0.01 mol/L or more, the flora of the nitrifying bacteria group can be favorably maintained and the urea removing ability can be improved. When the amount of the amino group is 10 mol/L or less, the stability of the amino group-immobilized polymer is excellent.

As the ion-exchange resin, a gel-type ion-exchange resin, a porous-type ion-exchange resin in which macropores having a pore size of 100 to 1000 angstrom are formed in the gel-type ion-exchange resin, and a high-porosity high-pore structure having finer pores than the porous-type ion-exchange resin Examples include porous ion exchange resins. Since the amount of amino groups per unit volume can be increased, a porous type or high porous type ion exchange resin is more preferable.

Further, as the ion exchange resin, a styrene/divinylbenzene copolymer or an acrylic polymer is used as a resin skeleton, and a trimethylammonium group (-N ⁺ (CH ₃ ) ₃ ) and a dimethylhydroxyethylammonium group (-N ⁺ (CH ₃ ) ₂ (C ₂ H ₅ OH)) and other strongly basic anion exchange resins having a quaternary ammonium group as an ion exchange group, and primary to tertiary amino groups such as methylamino group and dimethylamino group, and —NH A weakly basic anion exchange resin having a polyamine type ion exchange group represented by —(C ₂ H ₄ NH) _n H and the like can be mentioned. As the ion exchange fiber, a basic anion exchange fiber in which the above-mentioned primary to tertiary amino groups or quaternary ammonium groups are bonded to polyvinyl alcohol fiber can be used.

When a weakly basic anion exchange resin or a strongly basic anion exchange resin is used as the amino group-immobilized polymer, the water content thereof is preferably 35 to 65% by mass, and 40 to 50% by mass. More preferable. This facilitates retention of microorganisms when used in a mixture with biological activated carbon.

As the weakly basic anion exchange resin, for example, DIAION series (WA20, WA21J etc.) manufactured by Mitsubishi Chemical Co., Levatit series manufactured by LANXESS, Duolite series manufactured by DOW, etc. can be used. As the strongly basic anion exchange resin, for example, DIAION series (SA10A, SA20A) manufactured by Mitsubishi Chemical Co., Levatit series manufactured by LANXESS, Duolite series manufactured by DOW can be used.

As the weak base ion exchange fiber, for example, EF-SA-WA manufactured by Nichibi Co., Ltd., and as the strong base ion exchange fiber, IEF-SA manufactured by Nichibi Co., etc. can be used.

The ion exchange resins and ion exchange fibers that can be used are not limited to the types described above. When an ion exchange resin is used, the ion exchange resin may be a new ion exchange resin or a used ion exchange resin, for example, an ion exchange resin that has been used for a long time in a pure water producing apparatus.

As the amino group-immobilized polymer, a strong basic anion exchange resin having a quaternary ammonium group as an ion exchange group is preferable.

The method for obtaining a mixed bed of the amino group-immobilized polymer and the bioactive carbon is not particularly limited, and the bioactive carbon and the amino group-immobilized polymer prepared above are housed in a container and then mixed by passing water in an upward flow. It can be prepared by a method or a method of mixing with a mixer or the like. Further, it can be prepared by a method of supporting microorganisms in a mixed bed in which activated carbon and an amino group-immobilized polymer are mixed, using activated sludge. The nitrifying bacteria are dominated by adding an ammoniacal nitrogen source as a nutrient source to the microorganism as described above, which may be performed before mixing the bioactive carbon with the amino group-immobilized polymer. It may be performed after mixing the amino group-immobilized polymer and the bioactive carbon. Further, bioactive carbon in which nitrifying bacteria group is predominantly used may be used in advance, or the nitrifying bacteria group may be predominantly made after preparing a mixed bed.

The ratio of the amino group-immobilized polymer and the bioactive carbon is, for example, the volume ratio represented by the amino group-immobilized polymer/bioactive carbon, and the effect of the present invention can be obtained in the range of 1/99 to 99/1. From the viewpoint of further increasing the urea removal rate, 1/9 to 9/1 is more preferable, and 3/7 to 7/3 is even more preferable.

A biological treatment apparatus 20 is configured by filling a mixed bed of biological activated carbon and an amino group-immobilized polymer into, for example, a water treatment tower provided with a water supply pipe for supplying water to be treated and a discharge pipe for discharging treated water. You can

As the raw water W to be treated, ground water, river water, city water, other industrial water, or recovered water obtained by collecting used ultrapure water from a semiconductor factory, a liquid crystal factory, or the like is used. When the recovered water is used, it is preferable that the recovered water is subjected to an ion exchange treatment or a neutralization treatment to adjust the pH to, for example, the range described below. The water to be treated may be the raw water W treated with a pretreatment system or an apparatus similar thereto. The pretreatment system is composed of, for example, a coagulating sedimentation device, a pressure flotation device, a filtration device, etc., and removes suspended matter in the raw water.

The urea concentration in the raw water W (water to be treated) is preferably 5 to 200 μg/L, and particularly preferably 5 to 100 μg/L. Further, the dissolved oxygen concentration (DO) of the raw water W is preferably 5 to 8 mg/L in order to dominate the nitrifying bacteria group and increase the urea removal rate.

The raw water W is supplied to the biological treatment apparatus 20 where urea is removed. The method of passing water to the biological treatment apparatus stage 20 is not particularly limited and may be either an upward flow method or a downward flow method. The upflow method is preferable in that clogging by bacteria is unlikely to occur.

Water flow rate into the biological treatment apparatus 20 may preferably be about SV5~50hr ^-1, SV5~20hr ^-1 it is more preferred. From the viewpoint of improving the activity of microorganisms, the water temperature of the water to be treated supplied to the biological treatment apparatus 20 is preferably around room temperature, for example, 10 to 35°C, and more preferably about 20 to 35°C. Therefore, it is preferable to provide a heat exchanger before the biological treatment apparatus 20 as needed.

The pH of the water to be treated supplied to the biological treatment device 20 is preferably neutral to weakly alkaline, for example, pH 4 to 9, and preferably pH 5 to 8, from the viewpoint of predominantly nitrifying bacteria among microorganisms. Is more preferable.

In the water treatment device 1 of this embodiment, the reason why urea in water is reduced by the amino group-immobilized polymer and the bioactive carbon is presumed as follows.

Conventionally, when biological treatment is performed with a nitrifying bacteria group, an ammoniacal nitrogen source has been added to the feed water in order to maintain the flora of the nitrifying bacteria group that decomposes urea and to sterilize other bacteria. In the biological treatment apparatus 20, it is considered that the ammoniacal nitrogen contained in the amino group of the amino group-immobilized polymer acts in the same manner as the ammoniacal nitrogen added to water. That is, by continuously passing the water contacted with the amino group-immobilized polymer through the biological activated carbon, by the action of the ammonia nitrogen contained in the amino group-immobilized polymer, the flora of the nitrifying bacteria group is maintained. It is considered that the nitrifying bacteria group is dominated and urea is removed.

Therefore, the amino group-immobilized polymer and the bioactive carbon do not necessarily need to be mixed as in the biological treatment apparatus 20, and if the raw water W contacted with the amino group-immobilized polymer is treated by the bioactive carbon, the water treatment apparatus is used. The same effect as when 1 is used can be obtained. As an example of such a water treatment device having a configuration other than the water treatment device 1, a water treatment device 2 having a multiple bed in which an amino group-immobilized polymer and bioactive carbon are laminated as shown in FIG. 2 and shown in FIG. Such a water treatment device 3 having a single bed of an amino group-immobilized polymer and a single bed of bioactive carbon can be mentioned.

The water treatment device 2 includes a biological treatment device 21 having a laminated structure in which an amino group-immobilized polymer and biological activated carbon are laminated in this order from the upstream side. The water treatment device 3 is equipped with a device 22 having an amino group-immobilized polymer and a biological activated carbon device 23 in this order. For example, the same effects as those of the water treatment device 1 can be obtained for the water treatment devices 2 and 3.

In the water treatment device of each embodiment described above, when the water treatment is carried out for a long period of time by this, the bioactive carbon and the amino group-immobilized polymer, the bioactive carbons or the amino group-immobilized polymer adhere to each other. In this case, backwashing with water is carried out, but for example, with an agent such as an acid or alkali, such as an ion exchange device using an ion exchange resin or ion exchange fiber. No need to play.

According to the water treatment device of the embodiment described above, urea in water can be highly removed without adding a chemical such as an ammoniacal nitrogen source. Further, in the method of treating water added with an ammoniacal nitrogen source with biological activated carbon, it takes a long time to start up from the start of water passage to the biological activated carbon until the removal rate of urea becomes stable. According to the water treatment device, the startup period can be shortened.

(Ultrapure water production system)
Next, an ultrapure water production system equipped with the water treatment system of the above embodiment will be described. FIG. 4 is a block diagram schematically showing the ultrapure water production system 4 of the embodiment. The ultrapure water production system 4 includes a primary pure water system 41 and a secondary pure water system 42 on the downstream side of the water treatment device 1 (the water treatment device 2 or the water treatment device 3 may be used).

The primary pure water system 41 is configured by combining, for example, an ion exchange device, a reverse osmosis membrane device, a degassing device, an ultraviolet oxidation device, and a regenerative mixed bed type ion exchange device. In the primary pure water system 41, impurity ions are removed from the treated water from which urea has been removed by the water treatment apparatus 1 of the above-described embodiment by a combination of an anion exchange apparatus and a cation exchange apparatus as an ion exchange apparatus, and reverse osmosis is performed. The membrane device removes inorganic ions, organic substances, fine particles and the like. Further, dissolved gases such as dissolved oxygen and dissolved carbonic acid are removed by the deaerator. After the remaining organic substances are decomposed and removed by the ultraviolet oxidation device, a small amount of ionic components are removed by the regenerative mixed bed ion exchange device to produce primary pure water. For example, the primary pure water has a TOC concentration of 10 μg C/L or less and a specific resistance of 17 MΩ·cm or more.

The secondary pure water system 42 is a device that removes a trace amount of organic substances and trace particulates in the primary pure water, and combines an ultraviolet oxidation device, a membrane degassing device, a non-regeneration type mixed bed ion exchange device, and an ultrafiltration device. Consists of The ultrapure water thus obtained has a TOC concentration of 5 μg C/L or less, a specific resistance of 17.5 MΩ·cm or more, and a urea concentration of 5 μg/L or less.

According to the ultrapure water production system of the embodiment described above, urea in water can be highly removed without adding a chemical such as an ammoniacal nitrogen source to the water to be treated, so the TOC concentration is extremely low. Ultrapure water can be easily obtained. In addition, on the upstream side of the primary pure water system 41, the start-up period of the biological treatment device can be shortened as compared with a method of adding an ammonia nitrogen source to the water to be treated and then treating with biological activated carbon. Therefore, it is possible to efficiently produce ultrapure water without wasting raw water.

(Example 1)
Urea (2 mg/L) and ammonia (50 mg/L) were added to the activated sludge, and the mixture was allowed to stand for 30 days to acclimate the nitrifying bacteria sludge. When the urea removing ability of the obtained nitrifying bacteria sludge was measured using urea-containing water, urea could be removed up to 0.02 mg/L.

300 mL of activated carbon (Dia Hope M006, manufactured by Calgon Carbon Japan Co., Ltd., granular activated carbon, particle size 0.425 to 1.7 mm) was immersed in this nitrifying bacteria sludge for 7 days and then taken out to obtain biological activated carbon. A mixed bed was prepared by mixing 300 mL of this bioactive carbon with 100 mL of a strongly basic anion exchange resin (Diaion SA10A, manufactured by Mitsubishi Chemical Corporation, amino group amount 1.3 mol/L or more). The mixing ratio is 1/3, which is the volume ratio of strong basic anion exchange resin/bioactive carbon.

The obtained mixed bed was packed in a column having an inner diameter of 25 mm, and water obtained by removing chlorine from Atsugi-shi city water as treatment target water and adding urea (dissolved oxygen concentration 5-6 mg/L, pH=6-7, urea Water having a concentration of 10 to 20 μg/L was passed at SV=10 h ⁻¹ .

The urea concentration in the treated water obtained from the column was measured, and the time course of the urea removal rate was examined with the start of water passage as 0 day. The results are shown by the solid line in the graph of FIG. The urea removal rate was calculated by the following formula. The water temperature was allowed to flow without adjustment. The water temperature during the water flow test was 24 to 26°C. The same applies to the water temperature of each Example and Comparative Example described below.
Urea removal rate={(1-urea concentration in treated water)/urea concentration in treated water}×100(%)

Also, in Example 1, the strongly basic anion exchange resin after use was taken out of the column after passing water for 350 days and the exchange capacity was measured, and it was 95% of the initial exchange capacity. From this, it was confirmed that the ion exchange resin did not serve as a supply source of ammonium ions. Further, since the ammonium group is not reduced, it can be predicted that a high urea removal rate will be continuously maintained even when water is further passed.

(Comparative Example 1)
The column was filled with the bioactive carbon produced in the same manner as in Example 1 except that the strongly basic anion exchange resin was not mixed, and the same water to be treated as in Example 1 had ammonia at a concentration of 0.5 mg/L. Then, water was passed through the column under the same conditions as in Example 1. Similar to Example 1, the change with time of the urea removal rate was examined. The results are shown in a broken line in the graph of FIG.

(Example 2)
A mixed bed was prepared in the same manner as in Example 1 except that the amount of activated carbon used was 300 mL and the volume ratio of strong basic anion exchange resin/biological activated carbon was 1/1. Using this mixed bed, the urea removal rate was measured under the same conditions as in Example 1. In this example, the urea removal rate exceeded 85% after 30 days of passing water and reached 100% after 50 days.

(Example 3)
A mixed bed was produced in the same manner as in Example 1 except that the amount of activated carbon used was 300 mL and the volume ratio represented by strong basic anion exchange resin/biological activated carbon was 1/8. Using this mixed bed, the urea removal rate was measured under the same conditions as in Example 1. In this example, the urea removal rate exceeded 80% after 30 days of water passage and reached 90% after 50 days, and thereafter the urea removal rate remained stable.

(Example 4)
A mixed bed was prepared in the same manner as in Example 1 except that the amount of the activated carbon used was 300 mL and the volume ratio represented by the strongly basic anion exchange resin/biological activated carbon was 1/99. Using this mixed bed, the urea removal rate was measured under the same conditions as in Example 1. In this example, the urea removal rate exceeded 75% after 30 days of water passage and reached 88% after 50 days, and thereafter the urea removal rate remained stable.

(Example 5)
Similar to Example 1 except that a weakly basic anion exchange resin (Diaion WA30, manufactured by Mitsubishi Chemical Corporation, amino group amount 1.5 mol/L or more) was used instead of the strongly basic anion exchange resin. Then, a mixed bed was prepared. Using this mixed bed, the urea removal rate was measured under the same conditions as in Example 1. In this example, the urea removal rate exceeded 95% after 30 days of water passage and became 99% after 50 days, and thereafter the urea removal rate remained stable.

(Example 6)
The same strong basic anion exchange resin and biological activated carbon as in Example 1 were used, the amount of biological activated carbon used was 300 mL, and the mixing ratio was strong basic anion exchange resin/biological activated carbon (volume ratio). A mixed bed was produced in the same manner as in Example 1 except that the mixing time was 3/1. Using this mixed bed, the urea removal rate was measured under the same conditions as in Example 1. In this example, the transition of the urea decomposition rate was similar to that in Example 1 (solid line in FIG. 5).

(Example 7)
The strong basic anion exchange resin and the bioactive carbon similar to those in Example 1 were not mixed, but the bioactive carbon was laminated on the strong basic anion exchange resin (the strong basic anion was added to the water to be treated). A double bed was produced in the same manner as in Example 1 except that the exchange resin was on the upstream side and the biological activated carbon was on the downstream side. The urea removal rate was measured under the same conditions as in Example 1 except that the water to be treated was passed through the multiple beds in an upward flow. In this example, the transition of the urea decomposition rate was similar to that in Example 1 (solid line in FIG. 5).

(Comparative example 2)
100 mL of the same strongly basic anion exchange resin as in Example 1 was immersed in nitrifying bacteria sludge for 7 days, then taken out and packed in a column, and the removal rate of urea was measured under the same conditions as in Example 1. It was In this example, the urea removal rate exceeded 30% after 30 days of water passage and reached 45% after 50 days, and thereafter, the urea removal rate remained stable.

From the results of each example and comparative example, it is understood that the water treatment device of the embodiment can highly remove urea in water without adding a chemical agent such as an ammoniacal nitrogen source. Further, from FIG. 5, according to the water treatment device of the embodiment, the urea removal rate is stable from the start of water passage to the biological activated carbon as compared with the method of treating the water added with the ammoniacal nitrogen source with the biological activated carbon. It can be seen that the startup period up to can be shortened.

1, 2, 3... Water treatment device, 4... Ultrapure water production device, 10... Storage tank, 20, 21... Biological treatment device, 22... Device provided with amino group-immobilized polymer, 23... Biological activated carbon device, 41... Primary pure water system, 42... Secondary pure water system.

Claims (9)

A water treatment device for biologically treating raw water containing urea ,
A water-insoluble polymer having an amino group immobilized, which is contacted with raw water,
Wherein the amino group into contact with the water-insoluble polymer that is immobilized for processing the resulting et the treated water, and a biological activated carbon which nitrifying bacteria group for decomposing the urea is carried And water treatment equipment. The water treatment device according to claim 1, wherein the amino group is a quaternary ammonium group. The water-insoluble polymer having the amino group immobilized thereon and the bioactive carbon,
A mixed bed in which the water-insoluble polymer having the amino group immobilized and the biological activated carbon are mixed, or a composite bed in which the water-insoluble polymer having the amino group immobilized is laminated on the upstream side of the biological activated carbon. It is a floor, The water treatment equipment of Claim 1 or 2 characterized by the above-mentioned. The ratio of the water-insoluble polymer having the amino group immobilized thereto and the bioactive carbon is 1/99 to 99 in terms of a volume ratio expressed by the water-insoluble polymer having the amino group immobilized/the bioactive carbon. It is /1, The water treatment apparatus of any one of Claims 1 thru|or 3 characterized by the above-mentioned. The water-insoluble polymer having the amino group immobilized thereon is an ion exchange fiber or an ion exchange resin having the amino group as an ion exchange group, according to any one of claims 1 to 4. The described water treatment device. An ultrapure water production system comprising a primary deionized water system and a secondary deionized water system on the downstream side of the water treatment device according to any one of claims 1 to 5. Contacting raw water containing urea with a water-insoluble polymer having an amino group immobilized thereon,
A step in which the amino group is contacted to the water-insoluble polymer that is immobilized resulting et treated water, treated with biological activated carbon which nitrifying bacteria group is carried, to decompose the urea,
A water treatment method comprising: The water treatment method according to claim 7, wherein the raw water has a pH of 4-9. The water treatment method according to claim 7, wherein the raw water has a pH of 5-8.

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