JP2007319816A - Water treatment apparatus and water treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water treatment apparatus and a water treatment method which can reduce the amount of chlorine used in treatment of ammonia contained in raw water. <P>SOLUTION: In the water treatment apparatus and the water treatment method, a part of the raw water is separated to biologically oxidize ammonia in the raw water in the treatment of ammonia contained in the raw water, chlorine oxidation treatment and ultraviolet irradiation treatment are carried out after adding the biologically treated water to the residual raw water, and the usage of chlorine can be reduced by controlling a ratio of the amount of the separated water according to the concentration of ammonia nitrogen in the raw water. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a water treatment apparatus and a water treatment method for treating ammonia contained in raw water in water purification, environmental purification, industrial water treatment, sewage treatment, wastewater treatment, and the like.

  When ammonia is present in drinking raw water or waste water, the treatment method includes oxidation treatment with a chlorinating agent (chlorine oxidation treatment), biological oxidation treatment, stripping treatment, and the like. Also known is a method in which an oxidizing agent such as hydrogen peroxide is added to waste water and irradiated with ultraviolet rays to oxidize ammonia to nitric acid (see, for example, Patent Document 1).

Among them, chlorination treatment represented by the following formula using sodium hypochlorite or the like is often used, but in order to completely decompose and decompose ammonia into nitrogen, ammonia and Chlorine having a concentration ratio with chlorine of about 1:10 is necessary.
2NH ₃ + 3NaOCl → N ₂ + 3HCl + 3NaOH

Further, it is known that when ammonia and chlorine are reacted at a concentration ratio of about 1: 5, chloramine (monochloramine: NH ₂ Cl and dichloramine: NHCl ₂ ) is generated.
NH ₃ + NaOCl → NH ₂ Cl + NaOH
NH ₃ + 2NaOCl → NHCl ₂ + 2NaOH

  In contrast, in biological oxidation treatment, ammonia in raw water is oxidized to nitric acid or nitrous acid by living organisms. For example, Non-Patent Document 1 describes that, in the production of drinking water using groundwater (deep well) as raw water, iron removal and manganese removal filtration (chlorine + flocculant) is performed after biological oxidation treatment.

JP-A-7-155773 Waterworks design guideline 2000

  As described above, in order to completely oxidize ammonia with chlorine, a large amount of chlorine, which is about 10 times that of ammonia in concentration ratio, is required, and the amount of residual chlorine in the treated water increases. On the other hand, when the amount of chlorine used for the chlorination treatment was reduced, chloramine was produced, and ammonia could not be completely decomposed.

  In addition, when biological oxidation treatment is performed on raw water containing ammonia, the amount of nitric acid and nitrous acid contained in the biological treatment water increases when the concentration of ammonia in the raw water is high (for example, 10 mg / L or more), and the water quality standard value Is likely to exceed.

  The present invention is a water treatment apparatus and a water treatment method capable of reducing the amount of chlorine used in the treatment of ammonia contained in raw water.

  The present invention is a water treatment apparatus for treating ammonia contained in raw water, the ammonia concentration measuring means for measuring the ammonia nitrogen concentration of the raw water, branching the raw water, and depending on the ammonia nitrogen concentration in the raw water Water amount adjusting means for adjusting the branching water amount ratio, biological oxidation treatment means for biological oxidation treatment of the branched raw water, biological oxidation treated biological treatment water, and the remaining raw water A chlorinating agent adding means for adding a chlorinating agent to the mixed water, and an ultraviolet irradiation means for irradiating the chlorinated water with the chlorinating agent added thereto.

  In the water treatment apparatus, when the ammonia nitrogen concentration in the raw water is 5.0 mg / L or more and less than 10 mg / L by the water amount adjusting means, the amount of water for performing the biological oxidation treatment is 50 When the concentration of ammonia nitrogen in the raw water is 10 mg / L or more and 15 mg / L or less, the amount of water for performing the biological oxidation treatment may be adjusted to 30 to 50% by volume of the total treated water. preferable.

  Further, the water treatment apparatus preferably further includes a filtering means for filtering the ultraviolet treated water irradiated with the ultraviolet light, and a flocculant adding means for adding a flocculant to the treated water upstream of the filtering means. .

  Further, the present invention is a water treatment method for treating ammonia contained in raw water, wherein the raw water is branched, and a water amount adjusting step of adjusting the branching water amount ratio according to the ammonia nitrogen concentration in the raw water; A biological oxidation treatment step of subjecting one of the branched raw water to a biological oxidation treatment, a mixing step of mixing the biologically treated water subjected to the biological oxidation treatment, and the rest of the raw water, and chlorine in the mixed mixed water A chlorinating agent adding step of adding an agent, and an ultraviolet irradiation step of irradiating the chlorinated water to which the chlorinating agent is added with ultraviolet rays.

  In the water treatment method, when the concentration of ammonia nitrogen in the raw water is 5.0 mg / L or more and less than 10 mg / L in the water amount adjusting step, the amount of water for performing the biological oxidation treatment is 50 When the concentration of ammonia nitrogen in the raw water is 10 mg / L or more and 15 mg / L or less, it is preferable to adjust the amount of water for performing the biological oxidation treatment to 30 to 50% by volume of the total treated water. .

  The water treatment method preferably further includes a filtration step of filtering the ultraviolet treated water irradiated with the ultraviolet rays, and a flocculant addition step of adding a flocculant to the treated water upstream of the filtration step. .

  In the present invention, in the treatment of ammonia contained in the raw water, a part of the raw water is branched to biologically oxidize the ammonia in the raw water, and after the biologically treated water and the remaining raw water are combined, chlorination treatment and ultraviolet irradiation It is possible to provide a water treatment apparatus and a water treatment method capable of reducing the amount of chlorine to be used by performing the treatment and adjusting the ratio of the branched water amount according to the ammonia nitrogen concentration in the raw water.

  Hereinafter, embodiments of the present invention will be described.

When the present inventors biologically treat raw water containing ammonia, the amount of nitric acid and nitrous acid contained in the biologically treated water increases if the ammonia in the raw water has a high concentration (for example, 10 mg / L or more). Since the whole amount cannot be biologically treated, we conducted a biological treatment by bypassing a part of the raw water, and examined the method of chlorination after mixing the biologically treated water and the remaining raw water (blend treatment) . However, even with such a blending process, depending on the ammonia concentration in the raw water, the ratio of the amount of water to be chlorinated increases, and the addition of a large amount of chlorine increases chloride ions (Cl ⁻ ) and evaporation residues. In some cases, the water quality standards may be exceeded.

When ammonia in raw water is treated by chlorine oxidation, chloramines (monochloramine: NH ₂ Cl and dichloramine: NHCl ₂ ) are generated when the amount of chlorine used is reduced. Therefore, if the chloramine is decomposed by any method, ammonia can be completely decomposed while reducing the amount of chlorine to be used.

  Therefore, the present inventors further studied, and when branching (bypassing) part of the raw water, after adjusting the ratio of the amount of water branched according to the ammonia nitrogen concentration in the raw water, After biological treatment, the biological treated water and the remaining raw water are mixed, and then the amount of chlorine added is reduced by reducing the amount of chlorine added and chlorinated. It was found that ammonia can be almost completely decomposed.

  An example of the water treatment apparatus according to the embodiment of the present invention is shown in FIG. A water treatment apparatus 1 according to this embodiment includes a biological filtration apparatus 10 that is a biological oxidation treatment means, an ammonia concentration measuring instrument 11 that is an ammonia concentration measurement means, a biological filtration washing water tank 12, a mixing tank 14, and a chlorine agent. A chlorinating agent adding device 16 as an adding unit, a coagulant adding device 18 as a coagulant adding unit, an ultraviolet irradiation device 20 as an ultraviolet irradiating unit, a coagulating filtration device 22 as a filtering unit, and a coagulation filtration washing water tank 24. And comprising.

  In the water treatment apparatus 1, one end of the raw water inflow pipe 26 is connected to the upper part of the biological filtration apparatus 10, and the other end is connected to a raw water source 30 such as a deep well through a valve 76 and a pumping pump 28. Yes. Further, the raw water inflow pipe 26 is branched and connected to the upper part of the mixing tank 14 through a valve 74. The raw water inflow pipe 26 and the valve 74 function as water amount adjusting means. An ammonia concentration measuring device 11 is connected to the raw water inflow pipe 26. One end of the biologically treated water outflow pipe 32 is connected to the lower part of the biological filtration apparatus 10 via a valve 66, and the other end is connected to the upper part of the biological filtration washing water tank 12. One end of a biologically treated water outflow pipe 34 is connected to the upper part of the biological filtration washing water tank 12, and the other end is connected to the upper part of the mixing tank 14. A chlorine agent storage tank 38 is connected to the upper part of the mixing tank 14 via a chlorine agent injection pump 36, and a flocculant storage tank 42 is connected via a flocculant injection pump 40. The mixing tank 14 is provided with a stirrer 44 as a stirring means. The lower part of the mixing tank 14 is connected to the inlet of the ultraviolet irradiation device 20 through a pump 48 by a chlorinated water outflow pipe 46, and the outlet of the ultraviolet irradiation device 20 is connected to the upper part of the coagulation filtration device 22 through an ultraviolet treated water outflow pipe 50. Has been. The lower part of the coagulation filtration apparatus 22 is connected to the upper part of the coagulation filtration washing water tank 24 via the valve 78 by the coagulation filtration water outflow pipe 52, and the upper part of the coagulation filtration washing water tank 24 is connected to a treated water tank (not shown) or the like. ing. One end of the aeration air pipe 54 is connected to the lower part of the biological filtration device 10, and the other end is connected to the blower 58 via a valve 56. One end of a backwash pipe 60 is connected to the lower part of the biological filtration washing water tank 12 via a backwash pump 62 and a valve 64, and the other end is connected to the lower part of the biological filtration apparatus 10. One end of a backwash pipe 68 is connected to the lower part of the coagulation filtration washing water tank 24 via a backwash pump 70 and a valve 72, and the other end is connected to the lower part of the coagulation filtration device 22. A second chlorine agent storage tank 80 is connected to the ultraviolet treated water outflow pipe 50 via a second chlorine agent injection pump 82.

  Next, the operation of the water treatment apparatus 1 and the water treatment method according to this embodiment will be described. Raw water (treated water) such as deep well water is pumped by a pumping pump 28 from a raw water source 30 such as a deep well. The ammonia nitrogen concentration of the raw water is measured by the ammonia concentration measuring device 11 in the raw water inflow pipe 26. The raw water is partially branched at the raw water inflow pipe 26, and the amount of branching is adjusted by the valve 74 in accordance with the ammonia nitrogen concentration of the raw water, and then a predetermined amount of the branched raw water is supplied to the biological filtration device 10. The remaining raw water is sent to the mixing tank 14 (water amount adjusting step). Here, the branching water amount ratio may be controlled by operating the valve 74 by a control unit (control means) (not shown). Then, the raw water sent to the biological filtration device 10 is subjected to biological oxidation treatment in a downward flow while being aerated, and ammonia in the raw water is oxidized to nitrous acid or nitric acid (biological oxidation treatment step). And the biologically treated water is sent to the mixing tank 14 via the biological filtration washing water tank 12 and mixed with the remaining raw water (mixing step). The biologically treated water may be used for backwashing the biological filtration device 10 as partly backwashed water.

  In the present embodiment, the branching water amount ratio is controlled according to the ammonia nitrogen concentration in the raw water. Ammonia is oxidized to nitrous acid or nitric acid by biological oxidation treatment, but when used as drinking water from the viewpoint of health effects etc., these substances may have a nitrogen concentration of 10 mg / L or less, which is a tap water quality standard value. desired. Naturally, the lower the nitrogen concentration, the lower the risk to health. However, from the balance with economic efficiency, for example, water purification treatment with a target of less than 80%, preferably less than 50% of tap water quality standards. Is implemented. In this embodiment, depending on the ammonia nitrogen concentration in the raw water, the ratio of the biological treatment amount to the total treated water amount is such that the concentration of nitrous acid or nitrate nitrogen in the final treated water is less than 8.0 mg / L, preferably It is desirable to change it to be less than 5.0 mg / L. The amount of treated water for biological treatment changes due to fluctuations in the concentration of ammonia nitrogen in the raw water, but the unit for reducing the amount of biological treatment water when the ammonia nitrogen concentration increases and the amount of water increasing when the ammonia nitrogen concentration decreases. The ammonia nitrogen concentration per unit volume time does not change greatly. Therefore, the quality of the biologically treated water is relatively stable.

  Specifically, when the ammonia nitrogen concentration in the raw water is less than 10 mg / L, preferably 5.0 mg / L or more and less than 10 mg / L, the amount of water for biological treatment is 50 to 80% by volume of the total treated water. When the ammonia nitrogen concentration in the raw water is 10 mg / L or more, preferably 10 mg / L or more and 15 mg / L or less, the amount of water to be biologically treated is the total treated water. It is desirable that the range be 30 to 50% by volume, preferably 30 to 40% by volume. If the treatment is performed outside the above range when the ammonia nitrogen concentration in the raw water is 10 mg / L or more, the amount of nitric acid and nitrous acid contained in the biologically treated water increases, and the possibility of exceeding the water quality standard value is high.

  The ammonia concentration measuring device 11 is not particularly limited as long as it can measure the ammonia nitrogen concentration in the raw water, and examples thereof include a conductivity meter, an ion electrode, and a gas absorption absorption photometer. .

  In the biological oxidation treatment in the biological filtration apparatus 10, ammonia is oxidized to nitrous acid using dissolved oxygen by the nitrite bacteria, and a part or all of the nitrous acid is oxidized to nitric acid by the nitrite bacteria. Examples of bacteria that oxidize ammonia to nitrous acid include nitrite bacteria such as Nitrosoconas sp. And Nitrosococus sp. Examples of bacteria that oxidize nitrous acid to nitric acid include nitrifying bacteria such as Nitrobacter sp.

  Next, the chlorine agent is injected from the chlorine agent storage tank 38 into the mixed water mixed in the mixing tank 14 by the chlorine agent injection pump 36, and the raw water is subjected to chlorine oxidation treatment while being stirred by the stirrer 44 (chlorine agent). Addition step). The reaction time for the chlorine oxidation treatment may be about 3 to 10 minutes. In addition, in the mixing tank 14, the flocculant is added from the flocculant storage tank 42 by the flocculant injection pump 40 together with the addition of the chlorine agent (flocculating agent addition step). In addition to the decomposition of ammonia, the chlorine of the chlorinating agent sterilizes and oxidizes the metal, and the agglomerating agent agglomerates the insoluble metal, clay components, and organic matter including biological debris. In addition, depending on the quality of the target treated water (for example, other than for drinking water use), the flocculant addition step and the aggregation filtration step described later may be omitted. The flocculant may be added after the ultraviolet irradiation step.

  As the chlorinating agent, chlorine gas, sodium hypochlorite, liquefied chlorine, chloramine, chlorine dioxide and the like can be used, but sodium hypochlorite and liquefied chlorine are preferably used, and sodium hypochlorite is used. It is more preferable. The chlorine injection rate in the chlorine agent addition process using sodium hypochlorite or the like may be adjusted so that the residual chlorine concentration is 0.1 mg / L to 1.0 mg / L at the exit of the ultraviolet irradiation device 20. preferable.

  As the flocculant, inorganic flocculants such as aluminum salts and iron salts can be used. Specific examples include a polyaluminum chloride flocculant (PAC) and an iron-silica inorganic polymer flocculant (PSI) in which iron and polymerized silicic acid (silica) which is an inorganic anionic polymer are combined. The amount of the flocculant added is, for example, in the range of 5 mg / L to 30 mg / L in the case of PAC.

  Further, when the flocculant is added, the mixed water and the flocculant are rapidly mixed by the stirrer 44, whereby more reliable aggregation is achieved. The rapid stirring speed is, for example, in the range of 100 to 500 (1 / sec).

Next, the chlorinated water subjected to the chlorination treatment in the mixing tank 14 is sent to the ultraviolet irradiation device 20 by the pump 48, and an ultraviolet irradiation process is performed (ultraviolet irradiation process). In the ultraviolet irradiation step, the chlorinated water is irradiated with ultraviolet rays, and chloramines (monochloramine: NH ₂ Cl and dichloramine: NHCl ₂ ) generated by the chlorination treatment are decomposed.

  The wavelength of the ultraviolet rays to be irradiated is not particularly limited as long as it includes a wavelength at which chloramine is easily decomposed. It is known that monochloramine is decomposed mainly by irradiating ultraviolet rays around 250 nm and dichloramine is irradiated by ultraviolet rays around 220 nm or 290 nm (for example, Otsuki et al. Collection ", September 1990, p.900-901). Therefore, one or both of ultraviolet light near 250 nm and ultraviolet light near 220 nm or 290 nm may be irradiated depending on the production ratio of monochloramine and dichloramine.

  As the ultraviolet lamp, for example, a mercury lamp, an amalgam lamp, a xenon lamp or the like can be used. Mercury lamps are classified into low pressure, medium pressure, and high pressure depending on the mercury vapor sealing pressure in the lamp, and the wavelength distribution of ultraviolet rays is different, and therefore the mercury lamp may be selected according to the target wavelength.

Dose of ultraviolet rays irradiated by the ultraviolet irradiation device 20, as long as it can decompose chloramine is not particularly ^limited, is preferably in the range of ^{10mJ / cm 2 ~200mJ / cm 2} , 50mJ / cm 2 More preferably, it is in the range of ˜100 mJ / cm ² .

  The ultraviolet-treated water that has been subjected to the ultraviolet irradiation treatment passes through the ultraviolet-treated water outflow pipe 50 and is sent to the aggregation filtration device 22. As described above, the insoluble metal, clay component, and organic matter including biological debris are agglomerated by the action of the aggregating agent. It becomes water (aggregated filtered water) (filtration step). The treated water is discharged to the treated water tank or the like via the aggregation filtration washing water tank 24. When the treated water is used for drinking water, a granular activated carbon filtration treatment or the like is generally performed thereafter. Further, the treated water may be used for backwashing the coagulation filtration device 22 as partly backwash water.

  In addition, even if a chlorine agent is added from the second chlorine agent storage tank 80 by the second chlorine agent injection pump 82 connected to the ultraviolet treated water outflow pipe 50 before feeding from the ultraviolet irradiation device 20 to the aggregation filtration device 22. Good. Thereby, when undecomposed ammonia remains in treated water, ammonia can be decomposed reliably. The second chlorine agent injection pump 82 and the second chlorine agent storage tank 80 may also be used as the chlorine agent injection pump 36 and the chlorine agent storage 38. Further, the injection of the chlorine agent by the second chlorine agent injection pump 82 is not limited to the position of the ultraviolet treated water outflow pipe 50 but may be performed at the position of the coagulated filtrate water outflow pipe 52.

  As described above, with the water treatment apparatus and the water treatment method according to the present embodiment, the amount of chlorine to be used is reduced and ammonia is almost completely decomposed (the concentration of ammonia nitrogen in the treated water is, for example, 0. 05 mg / L or less).

  An example of the water treatment apparatus according to another embodiment of the present invention is shown in FIG. In addition to the configuration of the water treatment device 1, the water treatment device 3 according to this embodiment is a pH adjustment device 84 (pH adjustment agent injection pump 88, pH adjustment agent storage tank 90) that is a pH adjustment means for adjusting the pH of raw water. ) And a pH measuring device 86.

  In the water treatment apparatus 3, a pH adjusting agent storage tank 90 is connected to the upper part of the mixing tank 14 as a pH adding apparatus 84 via a pH adjusting agent injection pump 88. The mixing tank 14 is provided with a pH measuring device 86. That is, the mixing tank 14 includes pH adjusting means for adjusting the pH of the raw water to a range of 7.5 to 8.6.

  In the water treatment device 3, before the chlorinating agent adding step, the pH adjusting agent is injected from the pH adjusting agent storage tank 90 into the mixed water in the mixing tank 14 by the pH adjusting agent injection pump 88 and stirred by the stirrer 44. The pH of the raw water is adjusted to a range of 7.5 to 8.6 (pH adjusting step). At this time, the pH of the mixed water is preferably measured by the pH measuring device 86, and the injection amount by the pH adjusting agent injection pump 88 is preferably controlled by a control unit (not shown) or the like based on the measured value. In the present embodiment, after the pH adjustment step, as described above, the chlorine agent addition step, the flocculant addition step as necessary, the ultraviolet irradiation step, and the aggregation filtration step as necessary are performed.

  When chloramine is produced by reacting chlorine with ammonia, the production ratio of monochloramine and dichloramine varies depending on the pH at the time of reaction. Dichloramine is slightly produced at around pH 7.0, and slightly dichloramine is produced at around pH 7.5. At pH 8.0 or higher, almost all monochloramine is produced. Therefore, by adjusting the pH of the mixed water containing ammonia in the range of 7.5 to 8.6, the amount of added chlorine is reduced to perform the chlorine oxidation reaction, and the monochloramine that is easily decomposed is easily decomposed. By decomposing with ultraviolet rays having a wavelength, ammonia can be almost completely decomposed while further reducing the amount of chlorine used.

  In the method according to this embodiment, the pH of the mixed water is adjusted to a range of 7.5 to 8.6, and a predetermined amount of chlorinating agent is added according to the ammonia nitrogen concentration of the mixed water. The ammonium ion is converted to monochloramine by chlorine. If the pH is less than 8.0, dichloramine is slightly produced. Moreover, when pH exceeds 8.6, there exists a problem that it will exceed the water quality reference value as drinking water. Therefore, the pH is preferably in the range of 8.0 to 8.5.

  Examples of the pH adjuster include known alkalis such as sodium hydroxide, sodium carbonate, sodium hydrogen carbonate, potassium hydroxide, potassium carbonate, and calcium hydroxide when the mixed water is acidic, but sodium hydroxide is preferable. . The alkali is preferably added in the form of an aqueous solution in order to make it uniform quickly. When the mixed water is alkaline, known acids such as sulfuric acid, hydrochloric acid, phosphoric acid and the like can be mentioned, but sulfuric acid is preferred. Moreover, in order to avoid a rapid neutralization reaction, it is preferable to add an alkali or an acid as an aqueous solution of 5% to 30%, preferably 10% to 20%. In the case where the pH of the mixed water is in the range of 7.5 to 8.6, it is not necessary to add a pH adjuster here. When the raw water is deep well water, the pH is usually about 6.5 to 7.0, and an alkaline aqueous solution such as an aqueous sodium hydroxide solution is used as a pH adjuster.

  Also in the chlorinating agent addition step, the pH of the chlorinated water is measured by the pH measuring device 86, and the pH adjusting agent is injected by the pH adjusting agent injection pump 88 by the control unit or the like as necessary based on the measured value. The pH of the mixed water may be adjusted to be in the range of 7.5 to 8.6, preferably in the range of 8.0 to 8.5.

  As the wavelength of the ultraviolet rays irradiated in the ultraviolet irradiation step, those having a wavelength around 250 nm at which monochloramine is easily decomposed are preferable. As the ultraviolet lamp at this time, a low-pressure mercury lamp whose main emission wavelength is around 250 nm is preferable. The low-pressure mercury lamp has features such as low lamp power consumption and long lamp life.

  As described above, with the water treatment apparatus and the water treatment method according to the present embodiment, ammonia can be decomposed almost completely while further reducing the amount of chlorine to be used.

  The water treatment apparatus and the water treatment method according to the present embodiment are used for water treatment facilities, sewage treatment facilities, industrial wastewater treatment facilities, industrial water treatment facilities, etc. It can be used for the treatment of water, river water, lake water, coagulation sediment supernatant water, various process intermediate water, various recovered water, various waste water, and the like.

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

<Example 1>
A water flow experiment using a pilot plant shown in FIG. 1 was conducted at a water treatment facility using a deep well as raw water. The operating conditions in this example are shown in Table 1. In addition, Table 2 shows the quality of treated water at each step in the treatment flow of this example. The ratio of biological treated water to the total treated water amount was 50% by volume. The amount of chlorine added in Example 1 is 25 mg / L so that the monochloramine concentration, which is bound chlorine, is 4.0 mg / L in the mixing tank 14, and the free chlorine concentration in the aggregated filtered water is 0 in front of the aggregation filtration device 22. It was set to 3.0 mg / L so as to be 6 mg / L, and combined to 28 mg / L. The ammonia nitrogen concentration was measured using a HA ion electrode 50250 (manufactured by HACH), and the residual chlorine concentration and chloride ion concentration were measured using a polarographic method using a reagentless free chlorine meter CLF-111 (manufactured by Toa DKK Corporation). The evaporation residue was measured by the evaporation drying method.

<Example 2>
A water flow experiment using a pilot plant shown in FIG. 2 was conducted at a water treatment facility using deep wells as raw water. The operating conditions were the same as in Example 1 except that the pH of the mixed water obtained by mixing the biologically treated water and raw water was adjusted to 8.0 ± 0.1 by adding a 20% aqueous sodium hydroxide solution (Table 1). 1). Table 3 shows the quality of treated water in each step in the treatment flow of this example. The amount of chlorine added in Example 2 is 22 mg / L so that the monochloramine concentration, which is bound chlorine, is 4.0 mg / L in the mixing tank 14, and the free chlorine concentration in the coagulated filtration water is 0 before the coagulation filtration device 22. 2.0 mg / L so as to be 6 mg / L. By adjusting the pH of the mixed water to 8.0, the total amount of chlorine added could be 24 mg / L.

<Comparative Example 1>
A water flow experiment using a conventional pilot plant shown in FIG. 3 was conducted at a water treatment facility using deep wells as raw water. In the conventional apparatus shown in FIG. 3, raw water is pumped up from a raw water source 30 by a pumping pump 28, and after a chlorine agent and a flocculant are added to the line, the raw water is sent to a coagulation filtration device 22 through a line mixer 92. Aggregate is separated into solid and liquid by manganese sand and becomes aggregated filtrate. The agglomerated filtered water is discharged to the treated water tank or the like via the agglomerated filtration washing water tank 24. The treated water is partially used as backwash water for backwashing the coagulation filtration device 22. The operating conditions in this comparative example are shown in Table 1. In addition, Table 4 shows the quality of treated water in each step in the treatment flow of this comparative example. The amount of chlorine added in Comparative Example 1 was 87 mg / L so that the free chlorine concentration in the coagulated filtrate was 0.6 mg / L.

<Comparative example 2>
The treatment was performed in the same manner as in Comparative Example 1 except that the amount of chlorine added was 80 mg / L. Table 5 shows the quality of treated water in each step in the treatment flow of Comparative Example 2.

  In Examples 1 and 2 and Comparative Examples 1 and 2, the treatment is performed only up to the coagulation filtration. However, when used for drinking water, etc., it is common to perform a granular activated carbon filtration treatment or the like thereafter. In that case, in order to receive application of a tap water quality standard value, for example, an evaporation residue needs to be 500 mg / L or less. In other words, it is difficult to use drinking water in the conventional processing flows as in Comparative Examples 1 and 2, but it is understood that drinking water can be used in the methods of Examples 1 and 2. In Tables 2 to 5, the concentration of the evaporation residue of the coagulated filtered water is higher than that of the raw water because it is derived from sodium hypochlorite added for the oxidation of ammonia, iron, manganese, etc. It is.

  Further, in Examples 1 and 2 and Comparative Examples 1 and 2, the diameter of the coagulation filtration device, that is, the filtration rate is different. In the methods of Examples 1 and 2, part of iron and manganese is removed by biological filtration, This is because the load of suspended substances on the coagulation filtration device is reduced, so that stable operation is possible even at a higher filtration rate. By the way, the nitric acid / nitrite nitrogen concentration of treated water in Examples 1 and 2 was 9.0 mg / kg multiplied by 50% of the treated water volume ratio because the ammonia nitrification rate in the biological filtration apparatus was 100%. L × 0.5 = 4.5 mg / L. This is less than 50% of the tap water quality standard value of 10 mg / L, and can be regarded as good water quality.

<Example 3>
In a drinking water facility using deep wells as raw water, a water flow experiment was conducted using the pilot plant shown in FIG. The concentration of ammonia nitrogen in the well water was 8.4 to 12.6 mg / L, and the maximum change in time was 1.2 mg / L. When the ratio of the biologically treated water in the total treated water amount was changed from 59% to 39% by volume so that the nitrite nitrogen concentration or nitrate nitrogen concentration in the coagulated filtrate was less than 5.0 mg / L, The nitrification rate in biological treatment (the rate at which ammonia changed to nitrous acid or nitric acid) was always almost 100%. That is, when the ammonia nitrogen concentration in the raw water is 8.4 mg / L, the biological treatment water amount ratio is 59% by volume, and the nitrous acid or nitrate nitrogen concentration in the final coagulated filtrate is 8.4 mg / L × 59. % = 4.96 mg / L, and when the concentration of ammonia nitrogen in the raw water is 12.6 mg / L, the biological treatment water volume ratio is 39% by volume, and the concentration of nitrous acid or nitrate nitrogen in the final coagulation filtered water is 12.6 mg / L × 39% = 4.91 mg / L. This is less than 50% of the standard value of tap water quality of 10 mg / L, and can be regarded as good water quality. The amount of chlorine added in Example 3 was 17 mg / L so that when the concentration of ammonia nitrogen in the raw water was 8.4 mg / L, the concentration of monochloramine that is bound chlorine in the mixing tank 14 was 4.0 mg / L. In front of the flocculation filtration device 22, the free chlorine concentration in the flocculation filtration water was set to 2.0 mg / L so that the total concentration was 19 mg / L. When the concentration of ammonia nitrogen in the raw water is 12.6 mg / L, the mixing tank 14 is set to 82 mg / L so that the concentration of monochloramine, which is bound chlorine, is 4.0 mg / L. It was set to 3.0 mg / L so that the free chlorine concentration in filtered water was 0.6 mg / L, and the total was 85 mg / L. The total amount of chlorine added was 104 mg / L. The pH of the mixed water was 7.8 when the ammonia nitrogen concentration in the raw water was 8.4 mg / L, and 7.2 when the ammonia nitrogen concentration in the raw water was 12.6 mg / L. .

<Comparative Example 3>
The treatment was performed in the same manner as in Example 3 except that the biological treatment water amount ratio was fixed at 39% by volume and the biological treatment water amount was not adjusted according to the ammonia nitrogen concentration in the raw water. When the concentration of ammonia nitrogen in the raw water is 8.4 mg / L, the concentration of nitrous acid or nitrate nitrogen in the final coagulated filtered water is 8.4 mg / L × 39% = 3.28 mg / L. When the ammonia nitrogen concentration was 12.6 mg / L, the concentration of nitrous acid or nitrate nitrogen in the final aggregated filtered water was 12.6 mg / L × 39% = 4.91 mg / L. However, the chlorine addition amount in Comparative Example 3 was 27 mg / L in the mixing tank 14 when the ammonia nitrogen concentration in the raw water was 8.4 mg / L, and 2.0 mg / L in front of the coagulation filtration device 22. The total amount was 29 mg / L. When the concentration of ammonia nitrogen in the raw water was 12.6 mg / L, it was 82 mg / L in the mixing tank 14 and 3.0 mg / L in front of the coagulation filtration device 22, so that the total was 85 mg / L. The total amount of chlorine added was 114 mg / L, which was increased compared to Example 3. The pH of the mixed water was 7.9 when the ammonia nitrogen concentration in the raw water was 8.4 mg / L, and 7.2 when the ammonia nitrogen concentration in the raw water was 12.6 mg / L. .

<Comparative example 4>
The treatment was performed in the same manner as in Example 3 except that the biological treatment water amount ratio was fixed at 59% by volume and the biological treatment water amount was not adjusted according to the ammonia nitrogen concentration in the raw water. When the concentration of ammonia nitrogen in the raw water is 8.4 mg / L, the concentration of nitrous acid or nitrate nitrogen in the final coagulated filtered water is 8.4 mg / L × 59% = 4.96 mg / L. When the concentration of ammonia nitrogen was 12.6 mg / L, the concentration of nitrous acid or nitrate nitrogen in the final aggregated filtered water was 12.6 mg / L × 59% = 7.43 mg / L. This exceeded 50% of the tap water quality standard value of 10 mg / L. In addition, the amount of chlorine added in Comparative Example 4 was 17 mg / L in the mixing tank 14 when the ammonia nitrogen concentration in the raw water was 8.4 mg / L, and 2.0 mg / L in front of the coagulation filtration device 22. The total amount was 19 mg / L. When the concentration of ammonia nitrogen in the raw water was 12.6 mg / L, it was 55 mg / L in the mixing tank 14 and 2.0 mg / L in front of the coagulation filtration device 22, so that the total was 57 mg / L. The total amount of chlorine added was 76 mg / L. The pH of the mixed water was 7.8 when the ammonia nitrogen concentration in the raw water was 8.4 mg / L, and 7.0 when the ammonia nitrogen concentration in the raw water was 12.6 mg / L. .

Thus, when ammonia was chlorinated as in Examples 1 to 3, the amount of chlorine added could be significantly reduced (1/3 to 1/2). In addition, since the amount of chlorine used can be reduced, in the case of drinking water use, it is possible to improve water quality items such as Cl ⁻ concentration (reference value less than 200 mg / L) and evaporation residue (reference value less than 500 mg / L). It was.

It is a figure which shows schematic structure of an example of the water treatment apparatus which concerns on embodiment of this invention. It is a figure which shows schematic structure of the other example of the water treatment apparatus which concerns on embodiment of this invention. It is a figure which shows schematic structure of the conventional water treatment apparatus.

Explanation of symbols

1,3 Water treatment device, 10 Biological filtration device, 11 Ammonia concentration measuring device, 12 Biological filtration washing water tank, 14 Mixing tank, 16 Chlorine agent addition device, 18 Coagulant addition device, 20 Ultraviolet irradiation device, 22 Coagulation filtration device, 24 Coagulation filtration washing water tank, 26 Raw water inflow pipe, 28 Pumping pump, 30 Raw water source, 32 Biologically treated water outflow pipe, 34 Biologically treated water outflow pipe, 36 Chlorine injection pump, 38 Chlorine storage tank, 40 Coagulant injection pump, 42 flocculant storage tank, 44 stirrer, 46 chlorinated water outflow pipe, 48 pump, 50 UV treated water outflow pipe, 52 coagulated filtered water outflow pipe, 54 aeration air pipe, 56, 64, 66, 72, 74, 76, 78 Valve, 58 Blower, 60, 68 Backwash piping, 62, 70 Backwash pump, 80 Second chlorine agent storage tank, 82 Second chlorine agent injection pump, 84 pH adjuster, 86 pH measurement Device, 88 pH adjusting agent injection pump, 90 pH adjusting agent storage tank, 92 line mixer.

Claims (6)

A water treatment apparatus for treating ammonia contained in raw water,
Ammonia concentration measuring means for measuring ammonia nitrogen concentration of raw water;
A water amount adjusting means for branching the raw water and adjusting the ratio of the branched water amount according to the ammonia nitrogen concentration in the raw water;
Biological oxidation treatment means for biological oxidation treatment of the branched raw water,
A mixing vessel for mixing the biologically oxidized biologically treated water and the remaining raw water;
A chlorinating agent adding means for adding a chlorinating agent to the mixed mixed water;
Ultraviolet irradiation means for irradiating ultraviolet rays to chlorinated water to which the chlorinating agent is added;
A water treatment apparatus comprising: The water treatment device according to claim 1,
When the concentration of ammonia nitrogen in the raw water is 5.0 mg / L or more and less than 10 mg / L by the water amount adjusting means, the amount of water for performing the biological oxidation treatment is 50 to 80% by volume of the total treated water. When the ammonia nitrogen concentration in the water is 10 mg / L or more and 15 mg / L or less, the amount of water for performing the biological oxidation treatment is adjusted to 30 to 50% by volume of the total treated water. The water treatment device according to claim 1 or 2,
Filtration means for filtering the ultraviolet-treated water irradiated with the ultraviolet rays;
A flocculant addition means for adding a flocculant to the treated water upstream of the filtration means;
The water treatment apparatus further comprising: A water treatment method for treating ammonia contained in raw water,
Branching the raw water, adjusting the water amount ratio to branch according to the ammonia nitrogen concentration in the raw water,
A biological oxidation treatment step of subjecting the branched raw water to a biological oxidation treatment;
A mixing step of mixing the biologically oxidized biologically treated water and the remaining raw water;
A chlorinating agent adding step of adding a chlorinating agent to the mixed mixed water;
An ultraviolet irradiation step of irradiating the chlorinated water to which the chlorinating agent is added with ultraviolet rays;
A water treatment method comprising: The water treatment method according to claim 4,
In the water amount adjusting step, when the ammonia nitrogen concentration in the raw water is 5.0 mg / L or more and less than 10 mg / L, the amount of water for performing the biological oxidation treatment is 50 to 80% by volume of the total treated water. When the ammonia nitrogen concentration in the water is 10 mg / L or more and 15 mg / L or less, the amount of water for performing the biological oxidation treatment is adjusted to 30 to 50% by volume of the total treated water. The water treatment device according to claim 4 or 5,
A filtration step of filtering the ultraviolet-treated water irradiated with the ultraviolet rays;
A flocculant addition step of adding a flocculant to the treated water upstream of the filtration step;
The water treatment apparatus characterized by further including.

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