Well water treatment method, well water treatment device and program

Abstract

The present invention provides a well water treatment method, a water treatment device, and a program that can appropriately inject a chlorine-based chemical required to treat well water containing iron, ammonia, and microorganisms. [Solution] A method for treating well water containing iron, ammonia, and microorganisms by injecting a chlorine-based chemical into the well water. The chlorine-based chemical is stored in a storage tank, and the effective chlorine concentration of the chlorine-based chemical is estimated based on the temperature of the chlorine-based chemical stored in the storage tank. The amount of chlorine-based chemical to be injected is determined based on the estimated effective chlorine concentration of the chlorine-based chemical so that the effective chlorine concentration of the well water into which the chlorine-based chemical has been injected is 0.2 to 3.0 mg / L.

Description

[Technical Field]

[0001] The present invention relates to a method for treating well water containing iron, ammonia, and microorganisms. ,well This invention relates to a water treatment device and a program. [Background technology]

[0002] Conventionally, as a method for treating raw water containing divalent iron and ammonia, a technology has been proposed in which a chlorine-based oxidizing agent is added within a range that satisfies 0.83 × MFe ≦ MCl < 0.83 × MFe + 6.23 × MN, where MFe (mg / L) is the concentration of divalent iron in the raw water, MN (mg / L) is the concentration of ammonia nitrogen in the raw water, and MCl (mg / L) is the amount of chlorine injected from the chlorine-based oxidizing agent (Patent Document 1).

[0003] Furthermore, a technology has been proposed in which, when a chemical solution such as sodium hypochlorite is stored in a tank, the degree of deterioration of the chemical solution is calculated based on the temperature of the chemical solution stored in the tank, and if the degree of deterioration reaches a certain level or more, a warning is issued to replace the chemical (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2024-054580 [Patent Document 2] Japanese Patent Publication No. 2020-011175 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, the amount of chlorine-based oxidizing agent added is controlled so that the free chlorine concentration is 0.1 mg / L or less, but there is a problem in that sterilization using free chlorine cannot be performed when microorganisms are present in the raw water. Furthermore, when the raw water is well water, the concentrations of iron, ammonia, and microorganisms remain approximately constant, while the chlorine-based agent decomposes more rapidly at higher temperatures. When the chlorine-based agent is stored for a long period of time, the available chlorine in the chlorine-based agent is released as chlorine gas. Even when the amount of chlorine-based oxidizing agent added is determined based on the divalent iron and ammonia nitrogen concentrations in the raw water, the available chlorine concentration in the chlorine-based oxidizing agent decreases, resulting in an insufficient amount of chlorine, which may prevent the iron and microorganisms from being properly removed from the well water.

[0006] On the other hand, in the case of issuing a warning to replace the chemical when the degree of chemical degradation reaches a certain value or more, as in Patent Document 2, the degraded chemical will be used at the same amount until the chemical degradation reaches a certain value, which may result in insufficient removal of iron and microorganisms from well water. Also, a configuration in which the chemical is replaced when the degree of chemical degradation reaches a certain value or more poses environmental problems, such as the disposal of the degraded chemical.

[0007] Furthermore, in the invention described in Patent Document 2, when the amount of chemical injected is increased in accordance with the deterioration of the chemical, the amount of chloric acid generated by the decomposition of sodium hypochlorite also increases as the amount of chemical increases, and there is a risk that the chloric acid concentration will exceed the standard (0.4 mg / L or less) set by the Water Supply Act.The objective of the invention is to reduce this risk, which is contrary to the technical idea of ​​controlling the amount of chemical injected so that the reduced chloric acid concentration becomes a concentration suitable for sterilization.

[0008] The present invention relates to a well water treatment method and a well water treatment device that can appropriately inject chlorine-based chemicals necessary for treating well water containing iron, ammonia, and microorganisms. Place The purpose of this website is to provide information and programs. [Means for solving the problem]

[0009] The present invention provides the following (1) to ( 6 The gist of the present invention is a method for treating well water described in any one of the following: (1) A method for treating well water containing iron, ammonia, and microorganisms by injecting a chlorine-based agent into the well water, wherein the chlorine-based agent is stored in a storage tank, and the effective chlorine concentration of the chlorine-based agent is estimated based on the temperature of the chlorine-based agent stored in the storage tank. The amount of the chlorine-based agent to be injected is determined based on the effective chlorine concentration of the chlorine-based agent and a constant determined in advance according to the ammonia concentration, iron concentration, and microorganism concentration contained in the well water, so that the free chlorine concentration of the well water into which the chlorine-based agent has been injected is 0.2 to 3.0 mg / L. (2) The predetermined constant is estimated Divide by the available chlorine concentration of the chlorine-based agent Based on the calculated values , the injection amount of the chlorine-based agent decision The method for treating well water described in (1) above, wherein the constant is a value obtained by measuring the ammonia concentration of the well water in advance, and multiplying the amount of chlorine required to decompose the ammonia at the measured ammonia concentration in the well water by a margin factor of 1 to 2 that takes into account the amount of chlorine required to remove iron contained in the well water and to kill microorganisms. (3) A method for treating well water according to (1) above, in which the amount of chlorine-based chemicals to be injected is determined based on the available chlorine concentration of the chlorine-based chemicals so that the free chlorine concentration of the well water to which the chlorine-based chemicals have been injected is 0.5 to 1.5 mg / L. (4) A method for treating well water described in (1) above, in which the effective chlorine concentration of the chlorine-based agent is estimated based on the temperature of the chlorine-based agent in the storage tank as well as the elapsed time since the chlorine-based agent was received in the storage tank. (5) A method for treating well water according to (1) above, in which the effective chlorine concentration of the chlorine-based agent is estimated based on the integrated value of the temperature since the start of receiving the chlorine-based agent. ( 6) A well water treatment method as described in (1) above, which comprises an agent injection tank in which the chlorine-based agent is injected into the well water, a treatment tank for removing impurities from the well water sent from the agent injection tank, and a storage tank for storing the well water that has passed through the treatment tank, and a chlorine meter for measuring the free chlorine concentration is installed in the agent injection tank and / or the treatment tank, and the free chlorine concentration of the well water is measured using the chlorine meter. The present invention also provides the following ( 7 The gist of the present invention is a water treatment device described in ( 7 ) A well water treatment device that treats well water containing iron, ammonia, and microorganisms by injecting a chlorine-based agent, the well water treatment device comprising: a storage tank for storing the chlorine-based agent; an estimation means for estimating the available chlorine concentration of the chlorine-based agent based on the temperature of the chlorine-based agent stored in the storage tank; and a control means for controlling the injection amount of the chlorine-based agent based on the estimated available chlorine concentration of the chlorine-based agent so that the free chlorine concentration of the well water into which the chlorine-based agent has been injected is 0.2 to 3.0 mg / L. Furthermore, the present invention provides the following ( 8 The gist of the program is as follows: ( 8 ) A program executed by a well water treatment device that treats well water containing iron, ammonia, and microorganisms by injecting a chlorine-based agent, the program causing the well water treatment device to execute an estimation function that estimates the effective chlorine concentration of the chlorine-based agent based on the temperature of the chlorine-based agent stored in a storage tank, and a control function that controls the injection amount of the chlorine-based agent based on the estimated effective chlorine concentration of the chlorine-based agent so that the effective chlorine concentration of the well water into which the chlorine-based agent has been injected is 0.2 to 3.0 mg / L. [Effects of the Invention]

[0010] According to the present invention, it is possible to appropriately inject the chlorine-based chemicals required to treat well water containing iron, ammonia, and microorganisms. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram showing the configuration of a well water treatment system according to an embodiment of the present invention. [Figure 2] 1 is a graph illustrating the relationship between the injection amount of a chlorine-based chemical and the total residual chlorine concentration, the combined residual chlorine concentration, and the free residual chlorine concentration. [Figure 3] FIG. 2 is a diagram showing an example of an operation screen of the well water treatment device according to the present embodiment. [Figure 4] 10 is a diagram showing an example of an effective chlorine concentration setting screen of the well water treatment device according to the present embodiment. FIG. [Figure 5] 10 is a flowchart showing an initial setting process according to the embodiment. [Figure 6] 1 is a flowchart showing the treatment of well water according to the present embodiment. [Figure 7] 1 is a graph showing the transition of the free chlorine concentration in well water in this example. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention relates to a method for treating well water, a well water treatment device, a well water treatment system, and a program for treating well water, and is described below with reference to the accompanying drawings. While the present invention relates to a method for treating well water, and is described below with reference to the accompanying drawings, the present invention is not limited to a method for treating well water in the manufacture of semiconductor wafers. The present invention can be used for various purposes other than drinking water, such as other industrial water applications.

[0013] Fig. 1 is a configuration diagram of a well water treatment system 1 according to this embodiment. As shown in Fig. 1, the well water treatment system 1 according to this embodiment includes a pump 11, a raw water tank 12, a chemical injection tank 13, a treatment tank 141, a filtration membrane 142, a storage tank 15, an activated carbon tower 161, a reverse osmosis membrane 162, an ion exchange resin 163, and an ultrafiltration membrane 164. In this embodiment, the treatment tank 141 and the filtration membrane 142 are collectively referred to as a treatment unit 14, and the activated carbon tower 161, the reverse osmosis membrane 162, the ion exchange resin 163, and the ultrafiltration membrane 164 are collectively referred to as an advanced treatment unit 16.

[0014] The well water treatment system 1 according to this embodiment also includes a well water treatment device 2 for treating well water. In the well water treatment system 1 according to this embodiment, the water source 10, pump 11, raw water tank 12, chemical injection tank 13, treatment tank 141, filtration membrane 142, storage tank 15, activated carbon tower 161, reverse osmosis membrane 162, ion exchange resin 163, and ultrafiltration membrane 164 are connected by water pipes (not shown).

[0015] Water source 10 is a supply source of well water to be treated by well water treatment system 1 according to this embodiment. Well water according to this embodiment contains iron (mainly divalent iron), ammonia, and microorganisms. It may also contain metal ions other than divalent iron, such as manganese and calcium, as well as organic and inorganic substances other than microorganisms. The content (concentration) of iron, ammonia, and microorganisms in the well water supplied from water source 10 can be considered to remain almost constant throughout the year. In this embodiment, well water is pumped up from water source 10 by pump 11 and temporarily stored in raw water tank 12.

[0016] The well water temporarily stored in the raw water tank 12 is sent to the chemical injection tank 13. In the chemical injection tank 13, the well water treatment device 2 according to this embodiment injects a chlorine-based chemical such as sodium hypochlorite into the well water in the chemical injection tank 13 to remove iron and microorganisms.

[0017] Sodium hypochlorite is an oxidizing agent that can oxidize the ferrous iron contained in well water to ferric iron, precipitating insoluble iron(III) hydroxide. In this way, by injecting chlorine-based chemicals into well water containing iron (ferrous iron), the iron contained in the well water can be precipitated and removed. Furthermore, the chlorine and hypochlorous acid contained in sodium hypochlorite destroy the cell membranes of microorganisms in the well water and oxidize enzymes to stop their metabolism, thereby sterilizing the microorganisms. Sodium hypochlorite also reacts with ammonia contained in well water to produce chloramines, which remain in the well water because they are water-soluble.

[0018] In this embodiment, sodium hypochlorite is exemplified as the chlorine-based agent, but the chlorine-based agent is not particularly limited as long as it is an oxidizing agent containing a chlorine atom in the molecule, and for example, hypochlorous acid, sodium hypochlorite, calcium hypochlorite, etc. The chlorine-based agent may be used alone or in combination of two or more types.

[0019] In this embodiment, chemical injection tank 13 is provided with chlorine meter 131, which measures the free chlorine concentration of the well water in chemical injection tank 13 (i.e., the well water immediately after a chlorine-based chemical has been injected). The measurement result of the free chlorine concentration measured by chlorine meter 131 is transmitted to well water treatment device 2.

[0020] FIG. 2 is a graph illustrating the relationship between the injection amount of a chlorine-based agent and the total chlorine concentration, combined chlorine concentration, and free chlorine concentration. As shown in FIG. 2, when the injection amount of a chlorine-based agent is increased, initially, the ammonia and chlorine contained in the well water combine to form combined chlorine (chloramine), increasing the combined chlorine concentration. However, when the injection amount of a chlorine-based agent is further increased, the chloramine is decomposed by hypochlorous acid, decreasing the combined chlorine concentration. Furthermore, when chloramine is decomposed, the hypochlorous acid that had been combined with ammonia is liberated, increasing the free chlorine concentration. In this embodiment, since free chlorine is used to sterilize microorganisms contained in the well water, the injection amount of a chlorine-based agent is set so that the free chlorine concentration of the well water into which the chlorine-based agent has been injected is 0.2 to 3.0 mg / L, preferably 0.3 to 2.5 mg / L, more preferably 0.5 to 2.5 mg / L, and even more preferably 0.5 to 1.5 mg / L. A method for controlling the injection amount of a chlorine-based agent will be described later.

[0021] In the treatment tank 141, a pH adjuster (NaOH, H2SO4) and a flocculant (polymer flocculant, iron salt) are added to the well water to which chlorine-based chemicals have been added. This allows the iron (ferrous iron) and microorganisms contained in the well water to be more easily precipitated and separated.

[0022] The polymer flocculant is not particularly limited, and examples that can be used include cationic polymer flocculants such as polymethacryloyloxyethyltrimethylammonium chloride, acrylamide-acryloyloxyethyltrimethylammonium chloride copolymer, polyvinylamidine, etc., amphoteric polymer flocculants such as acrylamide-acrylic acid-acryloyloxyethyltrimethylammonium chloride copolymer, nonionic polymer flocculants such as polyacrylamide, and anionic polymer flocculants such as acrylamide-sodium acrylate copolymer.

[0023] 1, a chlorine meter 143 is also provided in the treatment tank 141. The chlorine meter 143 measures the free chlorine concentration of the well water in the treatment tank 141 and transmits the measurement result of the measured free chlorine concentration to the well water treatment device 2. In this embodiment, the injection amount of the chlorine-based chemical to be injected into the well water in the chemical injection tank 13 can be controlled based on the free chlorine concentration of the well water measured by the chlorine meter 143.

[0024] The filtration membrane 142 primarily removes microorganisms contained in well water. Specifically, the filtration membrane 142 has pores of 0.1 to 10 μm, allowing well water to pass through while preventing microorganisms such as E. coli from passing through. Microorganisms that cannot pass through the membrane are sterilized by continued contact with the well water containing chlorine and hypochlorous acid. In this embodiment, to efficiently sterilize microorganisms, the free chlorine concentration of the well water is adjusted to 0.2 to 3.0 mg / L, preferably 0.3 to 2.5 mg / L, more preferably 0.5 to 2.0 mg / L, and even more preferably 0.5 to 1.5 mg / L. This allows microorganisms contained in the well water that cannot pass through the filtration membrane 142 to be efficiently sterilized by hypochlorous acid and removed from the well water.

[0025] The well water filtered by the filtration membrane 142 is stored in the storage tank 15. The well water stored in the storage tank 15 can be used as general industrial water because iron and microorganisms have been appropriately removed from the well water. In the following description, the well water treated by the treatment unit 14 of the treatment tank 141 and the filtration membrane 142 will be referred to as industrial water. The industrial water can be used directly in the production of semiconductor wafers, or, as shown in FIG. 1, can be further treated in an advanced treatment unit 16 including an activated carbon tower 161, a reverse osmosis membrane 162, an ion exchange resin 163, and an ultrafiltration membrane 164. In this embodiment, the industrial water treated by the treatment unit 14 is used only for the initial cleaning of semiconductor wafers in the production of semiconductor wafers, and water treated by the advanced treatment unit 16 is used for grinding and polishing of semiconductor wafers.

[0026] 1, a chlorine meter 151 is provided in the storage tank 15. The chlorine meter 151 measures the free chlorine concentration of the well water in the storage tank 15 and transmits the measurement result of the measured free chlorine concentration to the well water treatment device 2.

[0027] Specifically, treatment unit 14 removes iron, microorganisms, and the like contained in well water, but industrial water contains chloramine (ammonia), free chlorine, and other microparticles (organic and inorganic) that could not be removed by treatment unit 14. Therefore, in this embodiment, industrial water is first supplied to activated carbon tower 161. In activated carbon tower 161, the free chlorine and microparticles contained in the industrial water are captured and reduced by the fine pores of the activated carbon.

[0028] Furthermore, in this embodiment, a reducing agent such as sodium bisulfite or sodium thiosulfate is added to the industrial water that has passed through the activated carbon tower 161 to reduce chlorine that has bound to ammonia as chloramines, followed by a coagulation process in which a coagulant such as aluminum sulfate or iron chloride is added to coagulate and precipitate remaining ammonia ions. The industrial water from which most of the ammonia has been removed then passes through a reverse osmosis membrane 162, which removes inorganic salt ions, heavy metal ions, organic matter, and the like that remain in the industrial water. Depending on the application, the industrial water (pure water) that has passed through the reverse osmosis membrane 162 can be used.

[0029] Furthermore, to increase the purity of the water, in this embodiment, the industrial water that has passed through the reverse osmosis membrane 162 is passed through the ion exchange resin 163. This allows residual metal ions and ionic components such as ammonia that could not be removed by the reverse osmosis membrane 162 to be adsorbed onto the ion exchange resin 163 and removed. The industrial water that has been treated with the ion exchange resin 163 can be used as ion-exchanged water.

[0030] Furthermore, in this embodiment, the industrial water that has passed through the ion exchange resin 163 is sent to an ultrafiltration membrane 164. The ultrafiltration membrane 164 has pores with a pore size of approximately 1 nm to 0.1 μm, and can separate fine suspended solids, bacteria, viruses, proteins, enzymes, colloids, etc. In this embodiment, the industrial water that has passed through the ultrafiltration membrane 164 can be used as ultrapure water.

[0031] In this embodiment, the ultrafiltration membrane 164 is installed after the reverse osmosis membrane 162. However, the ultrafiltration membrane 164 can also be installed before the reverse osmosis membrane 162. However, installing the ultrafiltration membrane 164 after the reverse osmosis membrane 162 is preferable due to the following advantages. Because the reverse osmosis membrane 162 can also remove ions, the load on the ion exchange resin 163 can be reduced (improving economic efficiency). Furthermore, installing the ultrafiltration membrane 164 last can remove dust particles (fine particles) that could not be removed by the ion exchange resin 163, thereby producing water with higher purity. Furthermore, installing the ultrafiltration membrane 164 last can avoid the risk of contamination during maintenance and the risk of impurities eluting from components of the reverse osmosis membrane 162 (brine seal, inner connectors, etc.). Furthermore, because the ultrafiltration membrane 164 has a smaller filtration area and is less easy to clean than the reverse osmosis membrane 162, installing the ultrafiltration membrane 164 after the reverse osmosis membrane 162 can prevent clogging of the ultrafiltration membrane 164. Furthermore, since the reverse osmosis membrane 162 requires more water for filtration than the ultrafiltration membrane 164, if it is installed after the ultrafiltration membrane 164, the size of the ion exchange resin 163 to be installed before the reverse osmosis membrane 162 must also be increased, which creates the problem of increased initial costs.

[0032] In this embodiment, a chlorine-based chemical such as sodium hypochlorite is stored in storage tank 21, and the chlorine-based chemical is injected from storage tank 21 into chemical injection tank 13 under the control of well water treatment device 2. Specifically, well water treatment device 2 can control the amount of chlorine-based chemical injected into chemical injection tank 13 by controlling the operation of chemical injection pump 22, which injects the chlorine-based chemical from storage tank 21 into chemical injection tank 13. In this embodiment, well water treatment device 2 has an operation screen shown in Figure 3, and an operator can operate this operation screen to make settings for controlling the injection amount of chlorine-based chemical.

[0033] Here, some of the chlorine contained in the chlorine-based chemical stored in storage tank 21 decomposes during storage and is released to the outside as chlorine gas, etc. For example, even if the available chlorine concentration of the chlorine-based chemical is 13.6% at the time of receipt, it may decrease over time to an available chlorine concentration lower than 13.6%. In particular, the decomposition of such chlorine-based chemicals tends to be accelerated as the temperature of the chemical increases, so it is important to appropriately estimate the available chlorine concentration of the chlorine-based chemical stored in storage tank 21.

[0034] Therefore, in this embodiment, for example, an operator measures the transition of the effective chlorine concentration of the chlorine-based chemical for each temperature in advance, and stores in the well water treatment device 2 a table of the effective chlorine concentration of the chlorine-based chemical for each temperature and number of days of the chlorine-based chemical in the storage tank 21. As a result, by referring to this table, the well water treatment device 2 can determine the effective chlorine concentration of the chlorine-based chemical based on the temperature of the chlorine-based chemical in the storage tank 21 and the number of days since the chlorine-based chemical was received, as shown in Figure 4. Note that Figure 4 is a diagram showing an example of an effective chlorine concentration setting screen.

[0035] In the well water treatment device 2, the "temperature" may be, for example, the average temperature for one day, the average temperature for a longer period (e.g., one week), or the temperature at a specific time of day (e.g., noon). Alternatively, a thermometer for measuring the temperature of the chlorine-based chemical in the storage tank 21 may be provided in the storage tank 21 to measure the temperature, or the temperature may be obtained from a weather database via the Internet. Alternatively, an operator may manually measure the temperature of the chlorine-based chemical in the storage tank 21 as needed. In particular, when the storage tank 21 is installed outdoors, the temperature of the chlorine-based chemical changes depending on whether the storage tank 21 is installed in the shade or in the sun. Therefore, it is preferable to provide a thermometer in the storage tank 21 and determine the average temperature for one day based on the data from the thermometer.

[0036] Furthermore, the number of days since the chlorine-based chemical was received in the storage tank 21 can be calculated by, for example, having an operator set the date (receiving date) on which the chlorine-based chemical began to be stored in the storage tank 21 as shown in FIG. 3 , so that the well water treatment device 2 calculates the number of days since the chlorine-based chemical was received. While the present embodiment illustrates a configuration in which the effective chlorine concentration of the chlorine-based chemical is estimated by setting the number of days since the chlorine-based chemical was received, the present invention is not limited to this configuration. For example, the effective chlorine concentration can be estimated by setting a time (hour) or a week. Furthermore, because the chlorine concentration of the chemical in the storage tank 21 is too high, it is not possible to directly measure the chlorine concentration of the chemical in the storage tank 21 using a chlorine meter. Therefore, in this embodiment, a chlorine meter is not installed in the storage tank 21, and the effective chlorine concentration of the chemical in the storage tank 21 is estimated based on the number of days since the chlorine-based chemical was received.

[0037] The well water treatment device 2 then determines the amount of chlorine-based chemical to be injected into the chemical injection tank 13 based on the estimated available chlorine concentration of the chlorine-based chemical. Specifically, the well water treatment device 2 determines the amount of chlorine-based chemical to be injected based on the following formulas (1) and (2) shown in FIG. 3. In this embodiment, an operator first measures the ammonia concentration of the well water in advance (for example, the operator manually measures the ammonia concentration at the beginning of system operation or once every few months). The operator then sets the measured ammonia concentration in the well water treatment device 2, and the well water treatment device 2 calculates the required chlorine concentration (mg / L) required to decompose the ammonia based on the input ammonia concentration, as shown in the following formula (1). Required chlorine concentration (mg / L) = ammonia concentration (mg / L) × 5.9 …(1) In the above formula (1), the coefficient "5.9" is a constant that indicates the mass ratio of chlorine required to decompose ammonia.

[0038] Furthermore, the well water treatment device 2 adds the amount (concentration) of chlorine required to remove iron and kill microorganisms in the well water to the required chlorine concentration (mg / L) required to decompose the ammonia contained in the well water, and determines the amount of chlorine-based chemical to be injected to obtain the total amount (concentration) of chlorine in the well water. Specifically, the well water treatment device 2 determines the amount of chlorine-based chemical to be injected into the well water by multiplying the required chlorine concentration (mg / L) required to decompose the ammonia contained in the well water by a margin rate to obtain the amount of chlorine required to remove iron and kill microorganisms in the well water, based on the following formula (2) shown in Figure 3. Injection rate of chlorine-based chemicals (ml / min) = Required chlorine concentration (mg / L) ÷ Available chlorine concentration (%) × Flow rate (m 3 / min) ÷ specific gravity × margin rate …(2)

[0039] Here, in the above formula (2), the effective chlorine concentration is the effective chlorine concentration of the chlorine-based chemical stored in the storage tank 21. As described above, the effective chlorine concentration of the chlorine-based chemical in the storage tank 21 decreases over time, so in this embodiment, the effective chlorine concentration of the chlorine-based chemical is estimated based on the temperature of the chlorine-based chemical in the storage tank 21 and the number of days since it was received. Specifically, in this embodiment, the temperature of the chlorine-based chemical in the storage tank 21 and the number of days since it was received are set on the effective chlorine concentration setting screen of FIG. 4, and the well water treatment device 2 can acquire the effective chlorine concentration of the chlorine-based chemical according to the temperature of the chlorine-based chemical in the storage tank 21 and the number of days since it was received.

[0040] In the above formula (2), the margin ratio is a value greater than 1 and indicates how many times the amount of chlorine required to decompose ammonia is required to remove iron from well water and sterilize microorganisms. It is preferable to set the margin ratio so that the free chlorine concentration in the well water is 0.2 to 3.0 mg / L, preferably 0.3 to 2.5 mg / L, more preferably 0.5 to 2.0 mg / L, and even more preferably 0.5 to 1.5 mg / L, after the chlorine contained in the chlorine-based chemical has been consumed to remove iron. The margin ratio can be determined by an operator collecting well water in advance and actually measuring how many times the amount of chlorine required to decompose ammonia that must be added to actually achieve the free chlorine concentration in the well water within the above range. Alternatively, the margin ratio can be set in advance by calculation. For example, the amount of divalent iron (Fe) in well water can be calculated. 2+ If the concentration of iron (Fe) in well water is 1 mg / L, the amount of chlorine required to remove ferrous iron is 1.27 mg / L. Therefore, the amount of chlorine required to decompose ammonia is 15 mg / L, and the amount of iron (Fe) in well water is 1.27 mg / L. 2+ If the ammonia concentration is 5 mg / L and the free chlorine concentration in the well water is 1.0 mg / L, the margin can be calculated as (15 + 1.27 x 5 + 1) / 15 = 1.49. In this way, if the amount of iron or microorganisms in the well water is high compared to the amount of ammonia contained in the well water, the margin should be increased in accordance with that ratio.

[0041] When well water containing ammonia, organic matter, and metals is treated with a chlorine-based agent containing hypochlorous acid, the ammonia reacts with the hypochlorous acid, generating combined chlorine (chloramines) during the ammonia decomposition reaction. When the amount of hypochlorous acid added is small, as shown in Figure 2, the ammonia primarily reacts, generating combined chlorine, and insufficient free chlorine is obtained to react with the metals. Therefore, in this embodiment, when treating well water containing ammonia, organic matter, and metals, the amount of chlorine added is determined so that the amount of chlorine contained in the well water into which the chlorine-based agent has been added is greater than the required amount of chlorine, based on the amount of chlorine required to decompose the ammonia contained in the well water, as shown in Equations (1) and (2) above, in order to obtain sufficient free chlorine. The greater the amount of chlorine added, the higher the free chlorine concentration, and the higher the ammonia concentration in the well water, the lower the free chlorine concentration. Therefore, by determining the amount of chlorine-based chemicals to be injected based on the amount of chlorine required to decompose the ammonia contained in well water, the free chlorine concentration of well water to which chlorine-based chemicals have been injected can be suitably adjusted to 0.2 to 3.0 mg / L, even if the well water has a higher ammonia concentration than other components.

[0042] Furthermore, in well water treatment system 1 according to this embodiment, chemical injection tank 13, treatment tank 141, and storage tank 15 are provided with chlorine meters 131, 143, and 151, and the free chlorine concentrations of the well water in chemical injection tank 13, treatment tank 141, and storage tank 15 measured by chlorine meters 131, 143, and 151 are transmitted to well water treatment device 2. Based on the free chlorine concentrations of the well water in chemical injection tank 13, treatment tank 141, and storage tank 15, well water treatment device 2 can adjust the injection amount of chlorine-based chemicals so that the free chlorine concentration of the well water is 0.2 to 3.0 mg / L, preferably 0.3 to 2.5 mg / L, more preferably 0.5 to 2.0 mg / L, and even more preferably 0.5 to 1.5 mg / L. For example, if the free chlorine concentration in the well water is likely to fall below 0.5 mg / L, the well water treatment device 2 increases the amount of chlorine-based chemicals injected by changing the margin rate preset by the operator to a larger value, thereby increasing the free chlorine concentration in the well water. In this embodiment, by providing chlorine meters 131, 143 in the chemical injection tank 13 and the treatment tank 141, the free chlorine concentration in the well water can be grasped in a short time span (almost in real time) compared to, for example, providing chlorine meter 151 only in the storage tank 15, and thus the amount of chlorine-based chemicals injected can be more appropriately controlled.

[0043] Next, the flow of well water treatment according to this embodiment will be described with reference to Figures 5 and 6. Here, Figure 5 is a flowchart showing the initial setting process according to this embodiment, and Figure 6 is a flowchart showing the chemical injection control process according to this embodiment. In this embodiment, the initial setting process shown in Figure 5 is first performed, and the chemical injection control shown in Figure 6 is performed based on the initially set contents. The initial setting process shown in Figure 5 is performed when the well water treatment system 1 according to this embodiment starts operating, or at regular intervals thereafter (for example, every few months).

[0044] First, the initial setting process shown in Fig. 5 will be described. As shown in Fig. 5, in step S101, the ammonia concentration of the well water before treatment is set. The ammonia concentration of the well water before treatment can be obtained by an operator by measuring it using a known method. The operator can then set the measured ammonia concentration of the well water through the screen shown in Fig. 4. Note that since the quality of well water is almost constant, the ammonia concentration of the well water can be measured once and not measured for a certain period of time.

[0045] In step S102, the required chlorine concentration for decomposing the ammonia contained in the well water is calculated. Specifically, the well water treatment device 2 calculates the chlorine concentration required to decompose the ammonia contained in the well water based on the ammonia concentration of the well water set in step S101. Here, since 5.9 mg / L of chlorine is required to decompose 1 mg / L of ammonia, in this embodiment, the required chlorine concentration is calculated by multiplying the ammonia concentration of the well water by a coefficient of 5.9.

[0046] In step S103, the margin rate is set. The margin rate can be set by an operator operating the operation screen shown in FIG. 3, which is displayed on the well water treatment device 2. The margin rate is a numerical value greater than 1 and can be changed depending on the amount of iron and microorganisms contained in the well water. An appropriate margin rate can be set by actually measuring the free chlorine concentration of well water into which a chlorine-based chemical has been injected and adjusting the margin rate so that the free chlorine concentration in the well water is 0.2 to 3.0 mg / L.

[0047] Next, the chemical injection control process shown in Figure 6 will be described. In step S201, the date of receipt of the chlorine-based chemical is set. For example, an operator can set the date of receipt of the chlorine-based chemical into the storage tank 21 via the operation screen shown in Figure 3. This allows the well water treatment device 2 to obtain the number of days since the chlorine-based chemical was stored in the storage tank 21.

[0048] In step S202, the temperature of the chlorine-based chemical in the storage tank 21 is set. For example, the operator can set the average temperature of yesterday or today as the storage temperature of the chlorine-based chemical through the available chlorine concentration setting screen shown in Figure 5. Also, a thermometer can be installed in the storage tank 21, and the average temperature can be set as the storage temperature of the chlorine-based chemical based on temperature data obtained from the thermometer installed in the well water treatment device 2.

[0049] In step S203, the well water treatment device 2 calculates the effective chlorine concentration. In this embodiment, the transition of the effective chlorine concentration of the chlorine-based agent is measured in advance for each temperature, and a table of the effective chlorine concentration of the chlorine-based agent for each temperature and storage time (number of days) of the chlorine-based agent is stored. By referring to this table, the well water treatment device 2 can calculate the effective chlorine concentration of the chlorine-based agent based on the temperature of the chlorine-based agent in the storage tank 21 acquired in step S202 and the elapsed time (number of days) since the chlorine-based agent was received acquired in step S201, as shown in FIG.

[0050] In step S204, the well water treatment device 2 calculates the amount of chlorine-based chemical to be injected into the well water. Specifically, the well water treatment device 2 can calculate the amount of chlorine-based chemical to be injected using the above formula (2) based on the chlorine concentration required to completely decompose the ammonia contained in the well water set on the initial setting screen shown in Fig. 5, the available chlorine concentration of the chlorine-based chemical stored in the storage tank 21 calculated in step S203, the flow rate measured by the flow meter, the specific gravity of the chlorine-based chemical (for example, 1.22 if the chlorine-based chemical is sodium hypochlorite), and the margin rate set on the initial setting screen shown in Fig. 5.

[0051] In step S205, well water treatment device 2 performs control to inject a chlorine-based chemical into the well water. Specifically, well water treatment device 2 controls the operation of chemical injection pump 22, causing chemical injection pump 22 to inject the chlorine-based chemical in the injection amount calculated in step S204.

[0052] In step S206, the free chlorine concentration of the chlorine-based chemical is obtained by the well water treatment device 2. Specifically, in this embodiment, chlorine meters 131, 143, 151 are provided in the chemical injection tank 13, the treatment tank 141, and the storage tank 15, and the well water treatment device 2 can obtain the measured values ​​of the free chlorine concentration in the chemical injection tank 13, the treatment tank 141, and the storage tank 15 from the chlorine meters 131, 143, 151.

[0053] In step S207, the well water treatment device 2 adjusts the margin rate based on the free chlorine concentrations in the chemical injection tank 13 and the treatment tank 141 obtained in step S206. Specifically, when the free chlorine concentration in the well water is likely to fall below 0.5 mg / L, the well water treatment device 2 increases the amount of chlorine chemicals injected by changing the margin rate preset by the operator to a larger value, thereby increasing the free chlorine concentration in the well water.

[0054] In step S208, the well water treatment device 2 determines whether a certain period of time (for example, one day) has passed. For example, if the certain period of time has not passed (step S208==No), the process returns to step S204, and the injection amount of the chlorine-based chemical is calculated again based on the margin rate adjusted in step S207 (step S204), and the chlorine-based chemical is injected in the calculated injection amount (step S205). On the other hand, if the certain period of time has passed, the well water treatment shown in FIG. 6 is terminated, and the process returns to step S201 again. [Example]

[0055] In this example, we measured the free chlorine concentration of well water over time using the well water treatment system 1 according to this embodiment, and verified whether it was possible to maintain the free chlorine concentration within a target range of 0.5 to 1.5 mg / L by controlling the amount of chlorine chemicals injected. Figure 7 is a graph showing the free chlorine concentration over time in well water according to this example. In this example, the amount of chlorine chemicals injected was not controlled based on the measurement results of the chlorine meters 131, 143, and 151. Instead, the screens shown in Figures 3 and 4 of the well water treatment device 2 were used to estimate the available chlorine concentration based on the temperature and number of days the chlorine chemicals were stored in the storage tank 21, and the estimated available chlorine concentration was used to determine the amount of chlorine chemicals to be injected into the well water. The graph shown in Figure 7 also shows the free chlorine concentration over time in well water over approximately three months.

[0056] As shown in Figure 7, in the well water treatment system 1 of this embodiment, the available chlorine concentration is estimated based on the temperature and number of days of storage of the chlorine-based chemical stored in the storage tank 21, and the estimated available chlorine concentration is used to determine the amount of chlorine-based chemical to be injected into the well water.As shown in Figure 7, by doing so, the free chlorine concentration of the well water could be controlled within the range of 0.5 to 1.5 mg / L over a period of three months.

[0057] As described above, in the well water treatment system 1 according to this embodiment, a chlorine-based chemical is stored in the storage tank 21, the available chlorine concentration of the chlorine-based chemical is estimated based on the temperature of the chlorine-based chemical stored in the storage tank 21, and the amount of chlorine-based chemical to be injected is determined based on the estimated available chlorine concentration of the chlorine-based chemical so that the free chlorine concentration of the well water into which the chlorine-based chemical has been injected is 0.2 to 3.0 mg / L. This allows the free chlorine concentration of the well water into which the chlorine-based chemical has been injected to be controlled within the range of 0.2 to 3.0 mg / L, even if the stored chlorine-based chemical deteriorates and the available chlorine concentration of the chlorine-based chemical decreases, and as a result, iron and microorganisms contained in the well water can be appropriately removed.

[0058] Although the preferred embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the above-described embodiments. Various modifications and improvements can be made to the above-described embodiments, and such modifications and improvements are also included in the technical scope of the present invention.

[0059] For example, in the above-described embodiment, the configuration in which the effective chlorine concentration of the chlorine-based chemical in the storage tank 21 is estimated based on the current temperature or average temperature of the chlorine-based chemical in the storage tank 21 is exemplified, but the present invention is not limited to this configuration, and the effective chlorine concentration of the chlorine-based chemical in the storage tank 21 may be estimated based on the integrated value of the temperature of the chlorine-based chemical in the storage tank 21 periodically measured after the chlorine-based chemical is received in the storage tank 21. [Explanation of symbols]

[0060] 1. Well water treatment system 10…Water source 11...Pump 12...Raw water tank 13...Chemical injection tank 131...Chlorine meter 14...Processing section 141... Treatment tank 143...Chlorine meter 142...filtration membrane 15...Storage tank 151...Chlorine meter 16...Advanced processing section 161...Activated carbon tower 162...Reverse osmosis membrane 163...Ion exchange resin 164...Ultrafiltration membrane 2...Well water treatment equipment 21...Storage tank 22...Drug infusion pump

Claims

1. A method for treating well water, which treats well water containing iron, ammonia, and microorganisms by injecting a chlorine-based agent, comprising: The chlorine-based agent is stored in a storage tank; Estimating the effective chlorine concentration of the chlorine-based agent based on the temperature of the chlorine-based agent stored in the storage tank; A well water treatment method in which the amount of chlorine-based chemical to be injected is determined based on the estimated available chlorine concentration of the chlorine-based chemical so that the free chlorine concentration of the well water into which the chlorine-based chemical has been injected is 0.2 to 3.0 mg / L.

2. The injection amount of the chlorine-based agent is determined based on a numerical value obtained by dividing a predetermined constant by the estimated available chlorine concentration of the chlorine-based agent; The method for treating well water described in claim 1, wherein the ammonia concentration of the well water is measured in advance, and the constant is a value obtained by multiplying the amount of chlorine required to decompose the ammonia at the measured ammonia concentration in the well water by a margin factor that is greater than 1 and takes into account the amount of chlorine required to remove iron contained in the well water and to kill microorganisms.

3. The well water treatment method according to claim 1, wherein the amount of chlorine-based agent to be injected is determined based on the effective chlorine concentration of the chlorine-based agent so that the free chlorine concentration of the well water into which the chlorine-based agent has been injected is 0.5 to 1.5 mg / L.

4. The well water treatment method of claim 1, wherein the effective chlorine concentration of the chlorine-based agent is estimated based on the temperature of the chlorine-based agent in the storage tank as well as the elapsed time since the chlorine-based agent was received in the storage tank.

5. 2. The well water treatment method according to claim 1, wherein the available chlorine concentration of the chlorine-based agent is estimated based on an integrated value of the temperature since the chlorine-based agent was received.

6. a chemical injection tank in which the chlorine-based chemical is injected into the well water; a treatment tank for removing impurities from the well water sent from the chemical injection tank; a storage tank in which the well water that has passed through the treatment tank is stored, The well water treatment method according to claim 1, wherein a chlorine meter for measuring the free chlorine concentration is installed in the chemical injection tank and / or the treatment tank, and the free chlorine concentration of the well water is measured using the chlorine meter.

7. A well water treatment device that treats well water containing iron, ammonia, and microorganisms by injecting a chlorine-based agent, a storage tank for storing the chlorine-based agent; an estimation means for estimating the effective chlorine concentration of the chlorine-based chemical based on the temperature of the chlorine-based chemical stored in the storage tank; A well water treatment device having a control means for controlling the injection amount of the chlorine-based agent based on the estimated effective chlorine concentration of the chlorine-based agent so that the free chlorine concentration of the well water into which the chlorine-based agent has been injected is 0.2 to 3.0 mg / L.

8. A program executed by a well water treatment device that treats well water containing iron, ammonia, and microorganisms by injecting a chlorine-based agent, A prediction function for predicting the effective chlorine concentration of the chlorine-based chemical based on the temperature of the chlorine-based chemical stored in the storage tank; A control function of controlling the injection amount of the chlorine-based agent based on the estimated effective chlorine concentration of the chlorine-based agent so that the effective chlorine concentration of the well water into which the chlorine-based agent has been injected is 0.2 to 3.0 mg / L.

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