JP5421948B2 - Water treatment system - Google Patents

Description

  The present invention relates to a water treatment system in which an appropriate amount of chemicals such as a flocculant, an adsorbent, an oxidizing agent, a reducing agent, an acid agent, and an alkaline agent is injected into a raw water supply, and then the raw raw water is processed by a main body water treatment device.

  If a removal target that is difficult to remove with the main body water treatment apparatus alone is included in the raw feed water due to water quality fluctuations such as rainfall, the removal target is mixed into the treated water. In order to prevent this, the quality of the raw feed water or treated water is measured, and the flocculant, adsorbent, oxidizing agent, reducing agent, acid is removed to remove the removal target contained in the raw feed water based on the measured value. A water treatment system is known that selects the optimal chemical from chemicals such as chemicals and alkaline agents and injects the appropriate amount into the raw feed water, and then processes the raw feed water into which the chemical is injected by the main body water treatment device. .

  A conventional water treatment system shown in FIG. 2 is known. This water treatment system 101 measures the supply raw water with the supply raw water quality meter 111, and the calculated value obtained by sequentially processing the measured value with the calculator 121 is a predetermined set value set in the calculator 121. Is exceeded, the chemical injection pump 132 is controlled to inject an appropriate amount of chemical stored in the chemical storage tank 131 into the raw feed water, and then this raw feed water is processed by the main body water treatment device 141 (described below). Patent Document 1).

  Since this water treatment system 101 measures the feed raw water, when the quality of the feed raw water fluctuates, it is possible to easily determine when to start the injection of chemicals and when to stop the injection. However, since the measured value of the feed water is used, it is necessary to perform the predetermined set value and the injection calculation formula set in the calculator 121 for each water treatment plant or treatment plant having different water quality. There is a problem that it depends heavily, and it is still difficult to secure workers, and it is expected that it will become even more difficult in the future. In addition, when an excessive amount of chemicals is injected into a substance that can be removed by the main body water treatment apparatus 141 alone, the main body water treatment apparatus 141 alone is difficult to remove, although the main body water treatment apparatus 141 alone is difficult to remove. When the processing unit 141 is judged to be capable of processing alone and chemicals are not injected or the amount of injection is insufficient, the operator setting the operator varies, resulting in variations or deterioration in the quality of the treated water, and waste of chemicals. There were problems such as. Furthermore, the measurement accuracy is deteriorated due to contamination of the feed raw water quality meter 111 due to the removal target or pollutant, causing deviation or no injection at the start of chemical injection, and is performed by the arithmetic unit 121 to inject an appropriate amount of chemical. There is a problem that an error occurs in the injection amount calculation, and in order to prevent this problem, it is necessary to frequently perform maintenance of the feed raw water quality meter 111, and there is also a problem that it takes cost and labor.

  Further, another conventional water treatment system shown in FIG. 3 is known. This water treatment system 201 measures the treated water with the treated water quality meter 211, and the calculated value obtained by sequentially processing the measured value with the calculator 121 is a predetermined set value set in the calculator 121. If it exceeds the limit, the chemical injection pump 132 is controlled to inject an appropriate amount of the chemical stored in the chemical storage tank 131 into the supply raw water, or the injection of the chemical injected into the supply raw water is stopped or the injection amount of the chemical is changed. Then, after that, the supplied raw water is treated by the main body water treatment device 141 (see Patent Document 2 below).

  Since this water treatment system 201 measures treated water, it is suitable for starting the injection of appropriate chemicals when the quality of the raw feed water deteriorates and the main body water treatment device alone cannot treat the removal target. . However, after the quality of the raw feed water is stabilized, there is a problem that it is difficult to make a judgment when stopping the injection of the chemical injected into the raw feed water or reducing the injection amount of the chemical. Furthermore, since an appropriate amount of chemicals is injected into the supply raw water using the measurement value obtained by measuring the treated water treated by the main body water treatment device 141, the quality of the supply raw water is improved during the treatment by the main body water treatment device 141. When changed, there was a problem that treated water with incomplete treatment was mixed into the treated water side.

  Further, another conventional water treatment system shown in FIG. 4 is known. This water treatment system 301 measures the feed raw water with the feed raw water quality meter 111 and measures the treated water with the treated water quality meter 211, and the computation obtained by sequentially processing both measured values with the computing unit 121. When the value exceeds a predetermined set value set in the calculator 121, the chemical injection pump 132 is controlled and stored in the chemical storage tank 131, and the optimal chemical is selected from the chemicals and injected into the supply raw water. After that, this raw raw water is treated by the main body water treatment device 141 (see Patent Document 3 below).

  The water treatment system 301 can easily determine when to start and stop chemical injection. However, since it takes a certain amount of time to process the raw feed water and treat it with the main body water treatment device 141, a time lag occurs when trying to measure the same target with the feed raw water quality meter 111 and the treated water quality meter 211. In addition, when an object to be removed that cannot be removed by the main body water treatment device 141 is mixed into the raw feed water, there is a problem that treated water with incomplete treatment enters the treated water side. In addition, when an abnormality occurs in the feed raw water quality meter 111, there is a problem that the judgment when stopping the chemical injection is wrong. Furthermore, the measurement accuracy deteriorates due to contamination of the feed raw water quality meter 111 due to the removal target or pollutant, causing deviation or no injection when starting chemical injection, and injection performed by the calculator 121 to inject an appropriate amount of chemical. There is a problem that an error occurs in the amount calculation, and in order to prevent this problem, it is necessary to frequently perform maintenance of the feed raw water quality meter 111, and there is a problem that costs and labor are required. In addition, water quality meters, especially water quality meters on the supply raw water side, are expensive and need to be installed on both the supply raw water side and the treated water side for control. At the same time, since the number of water quality meters increases, the maintenance becomes complicated, and there is a problem that costs and labor are required.

  Furthermore, as another conventional water treatment system, a part of the raw water supplied with chemicals is measured by a small water treatment device different from the main body water treatment device, and the measured values are sequentially processed by an arithmetic unit. When the calculated value exceeds the set value set in the calculator, the chemical injection pump is controlled to inject an appropriate amount of chemical stored in the chemical storage tank into the raw water supply, or the chemical injection pump Is controlled to stop the injection of chemicals injected into the raw raw water or change the injection amount of the chemicals, and then treat the supplied raw water with the main body water treatment device (Patent Document 4 below) reference).

  This water treatment system optimally controls the injection rate of chemicals with a short time lag, changes the quality of the raw feed water while it is being treated by the main body water treatment device, and incompletely treated water enters the treated water side. This is intended to solve the problems that occur. Since the quality of the treated water is measured, it is suitable for starting an appropriate chemical injection when the quality of the treated water deteriorates. However, since the treated water into which the chemical is injected is measured, it is difficult to judge when the injection of the chemical injected into the supply raw water is stopped or the injection amount of the chemical is changed after the quality of the raw water is stabilized There was a defect. Furthermore, since the treated water obtained by treating the raw water supplied with chemicals with a small water treatment device is measured, there is a problem that the amount of chemicals used increases.

JP2007-98236 JP-A-10-165934 JP 07-299472 A JP 05-146608

  The present invention has been made to solve the above-described drawbacks, and the object of the present invention is that the computing unit is a measured value measured by the water quality meter and a predetermined set value set in the computing unit. Based on the above, when the chemical injection pump is controlled to inject the chemical into the supply raw water, or to stop the injection of the chemical injected into the supply raw water, or to change the injection amount of the chemical, the predetermined setting value set in the calculator Can be set without depending on the experience of the operator, even if the operator who sets the setting value etc. in the calculator is different, the variation in the quality of the treated water can be eliminated, and the waste of chemicals can be prevented, To provide a water treatment system capable of obtaining reliable and good treated water quality.

  Another purpose is that, after the quality of the raw feed water is stabilized, the computing unit controls the chemical injection pump based on the measured value of the treated water and the predetermined set value, and is injected into the raw feed water. It is to provide a water treatment system that can stop the injection or change the injection amount of the chemical, and can reduce the usage of the chemical injected into the raw feed water.

  Another purpose is that the computing unit can control the chemical injection pump based on the measured value of the treated water and the set value, etc., and inject the chemical into the raw water supply in a timely manner, and the processing is incomplete. It is providing the water treatment system which can prevent that a treated water mixes into the treated water side.

  Another object is to provide a water treatment system that prevents deterioration in measurement accuracy due to contamination of water quality instruments, reduces the frequency of maintenance, and can reduce costs and labor.

  Another object of the present invention is to provide a water treatment system capable of omitting an expensive supply raw water quality meter as a water quality meter for control and suppressing initial capital investment.

In order to achieve the above object, a water treatment system according to the present invention includes a chemical injection control water treatment device that treats a part of raw feed water to obtain treated water, and a treatment treated by the chemical injection control water treatment device A treated water quality meter for measuring water, a measured value measured by the treated water quality meter, a calculated value obtained by processing the measured value based on a predetermined method, and a predetermined value for the calculated value set value of the basis of the arithmetic to change the appropriate amount injected or chemicals that are injected are in the supply raw water to stop or injection of chemicals to the feed raw water from the chemical reservoir to selected chemicals to control the dosing pump The same as the water treatment device for chemical injection to treat the raw material water into which the appropriate amount of chemical is injected by the calculator or the injection of the injected chemical is stopped or the injection amount of the chemical is changed to be treated water of It is characterized in further comprising a body water treatment device management method.

  The water treatment system according to the present invention is characterized in that the chemical treatment water treatment device and the main body water treatment device are either a membrane filtration device, a sand filtration device, or a fiber filtration device. .

  In the water treatment system according to the present invention, the chemical treatment water treatment apparatus and the main body water treatment apparatus include a pretreatment device.

  According to the water treatment system of the present invention having the above-described configuration, the arithmetic unit controls the chemical injection pump based on the measured value of the treated water processed by the chemical injection control water treatment device and the predetermined set value. The appropriate amount of the selected medicine is injected from the stored chemical storage tank into the supply raw water, or the injection of the chemical injected into the supply raw water is stopped or the injection amount of the chemical is changed. The set value or the like becomes the set value or the like for the treated water, and the operator can set the set value or the like of the treated water without depending on experience. Therefore, it is possible to eliminate variations in the quality of the treated water treated by the main body water treatment device even if the operator who sets the setting value etc. in the computing unit is different, preventing waste of chemicals and ensuring a reliable and good treated water quality. Can be obtained.

  Furthermore, in the water treatment system of the present invention, the computing unit controls the chemical injection pump based on the measured value of the treated water obtained by treating a part of the supply raw water before chemical injection with the chemical treatment control water treatment device, Stops the injection of chemicals injected into the raw water or changes the amount of chemicals to be injected. After the water quality of the raw water has stabilized, the injection of chemicals can be stopped or the injection amount of chemicals can be easily changed. The amount of chemicals used can be reduced.

  Furthermore, in the water treatment system of the present invention, the computing unit controls the chemical injection pump based on the measured value obtained by measuring the treated water treated by the chemical treatment control water treatment device, and the selected chemical is stored. Inject appropriate amount from the chemical storage tank into the supply raw water, or stop the injection of chemicals injected into the supply raw water or change the injection amount of chemicals, so the time lag is shorter than using the treated water treated by the main body water treatment device. Therefore, when the quality of the raw feed water is deteriorated, the chemical can be injected in a timely manner, and the treated water incompletely treated can be prevented from being mixed into the treated water side.

  Furthermore, the water treatment system of the present invention measures the treated water treated by the water treatment device for chemical injection control, so that the measurement accuracy is prevented from deteriorating due to dirt on the water quality instrument, and the measurement instrument is only intended to remove dirt. Maintenance is not required, and maintenance costs can be reduced.

  Furthermore, the control water quality meter is only a treated water quality meter that measures the treated water treated by the chemical injection control water treatment device, and does not require a particularly expensive feed raw water quality meter installed on the feed raw water side, The initial capital investment cost can be kept low.

Schematic explanatory diagram of a water treatment system according to the present invention Schematic explanatory diagram of conventional 1 water treatment system Schematic explanatory diagram of conventional 2 water treatment system Schematic explanatory diagram of conventional 3 water treatment system

  Hereinafter, with reference to the drawings, a water treatment system according to an embodiment of the present invention will be described by way of example.

  FIG. 1 is a schematic explanatory diagram of a water treatment system according to the present invention. The water treatment system 1 according to the present invention includes a chemical treatment control water treatment device 10, a treated water quality meter 20, a calculator 30, and a main body water treatment device 40.

  The chemical injection control water treatment device 10 is a small water treatment device capable of filtering the raw feed water by the same treatment method as the main body water treatment device 40 described later. Therefore, if the supply raw water is the same, the quality of the treated water treated by the chemical injection control water treatment device 10 and the quality of the treated water treated by the main body water treatment device 40 are the same. In the present embodiment, since the main body water treatment device 40 is a single UF membrane filtration device, the chemical treatment water treatment device 10 is also a single UF membrane filtration device. If the main body water treatment device 40 is a sand filtration single device, the chemical injection control water treatment device 10 is also a sand filtration single device. If the main body water treatment device 40 is a sand filtration device having a pretreatment device, chemical injection is performed. The control water treatment device 10 is also a sand filtration device having a pretreatment device. The chemical injection control water treatment apparatus 10 introduces and processes a part of the supply raw water before the chemical for removing the removal target is injected, and the entire amount of the treated water flows into the treated water quality meter 20 described later. It is like that. The supplied raw water is a name of raw water supplied to the water treatment system 1 of the present invention. Accordingly, in addition to raw water such as rain water, treated water that has been subjected to pretreatment such as precipitation in a water storage tank is also supplied raw water when introduced into the water treatment system 1. In addition, when the water treatment apparatus and the water treatment system 1 of the present invention are connected, the treated water treated by the preceding water treatment apparatus changes its name as the feed raw water when it is introduced into the subsequent water treatment system 1. . The treated water refers to treated water treated by the water treatment system 1, that is, treated water treated by the chemical injection control processing apparatus 10 or the main body processing apparatus 40.

  The treated water quality meter 20 is a meter that measures the quality of treated water treated by the chemical treatment control water treatment device 10 and is constituted by one or a plurality of meters. The monitoring measurement items for monitoring whether or not the supply raw water contains removal targets that cannot be treated by the main body water treatment device 40 are turbidity, chromaticity, ultraviolet absorbance, electrical conductivity, oxidation-reduction potential, and pH value. STR (Abbreviation of Suction Time Ratio, meaning suction time ratio), fine particles, and the like. Therefore, the treated water quality meter 20 is usually composed of a plurality of meters so that the above-mentioned monitoring measurement items can be measured. However, when the removal target contained in the feed raw water is limited and only one instrument that can measure the monitoring measurement item for specifying the removal object is required, the treated water quality meter 20 is composed of a single instrument. The treated water quality meter 20 continuously measures the inflowed treated water and sends measured values to the computing unit at regular intervals.

  The computing unit 30 sequentially processes the measurement values sent from the treated water / water quality meter 20 and converts them into computed values, and determines whether or not a predetermined set value set in advance in the computing unit 30 is deviated. It is supposed to be. As a result, when the calculated value for a certain monitoring measurement item A is outside the range of the predetermined set value, the medicine C optimal for removing the removal target B specified by the monitoring measurement item A is stored. The chemical storage tank 31C is selected, and the chemical injection pump 32 is supplied with an injection amount of the chemical C that can be removed from the removal target B based on the injection calculation formula set in advance in the calculator 30 and the flow rate of the supply raw water. Is controlled and injected into the raw water supply. Further, when the medicine D is injected from the medicine storage tank 31D in which the specific medicine D is stored and the calculated value is within a predetermined set value range, the medicine injection pump 32 is controlled. Thus, the injection of the chemical D into the raw water supply is stopped. Furthermore, when the medicine E is injected from the medicine storage tank 31E in which the specific medicine E is stored, the calculated value is out of the predetermined set value, but the difference from the predetermined set value is In the case where the change has been made since the previous measurement, the injection amount of the medicine E injected is changed based on the injection calculation formula. In addition, the chemical | medical agent stored in the chemical | medical agent storage tank 31 is a chemical | medical agent for removing the removal object specified by the above-mentioned monitoring measurement item, flocculant, powder activated carbon, sodium hypochlorite, ozone, sodium bisulfite, Since chemicals such as acid agents such as sodium thiosulfate and sulfuric acid and alkaline agents such as caustic soda are stored in separate chemical storage tanks 31, the chemical storage tanks 31 are usually composed of a plurality. However, when the treated water quality meter 20 is composed of a single meter, the removal target specified by the monitoring measurement item measured by the meter is a specific single number, and the chemical for removing the removal target may be a single number, The chemical storage tank 31 is composed of a single unit. As the flocculant, inorganic flocculants such as aluminum sulfate, polyaluminum chloride, ferric chloride, polysilica iron, and organic flocculants such as anionic polymer flocculants, cationic polymer flocculants, and nonionic polymer flocculants are used. Any of the flocculants may be used, and these flocculants may be used alone or in combination.

  The main body water treatment device 40 is a single UF membrane filtration device. However, the main body water treatment device 40 can be changed according to the supply raw water or the treatment target water quality. Therefore, it may be a membrane filtration single device using either MF membrane or NF membrane or RO membrane, either UF membrane or MF membrane or NF membrane or RO membrane having a pretreatment device. A membrane filtration device using a membrane may be used. Furthermore, it may be a clarification or coarse filtration sand filtration single device instead of a membrane filtration device, or a clarification or coarse filtration sand filtration device having a pretreatment device. The pretreatment device refers to a coagulation single device, a normal precipitation single device, a coagulation sedimentation device, a sand filtration device, a fiber filtration device, and the like.

  Next, in the water treatment system 1 having the above-described configuration, a flow for injecting an appropriate amount of chemical into the supply raw water or stopping injection of the chemical injected into the supply raw water or changing the injection amount of the chemical will be described.

  A part of the supply raw water into which the chemical for removing the removal target has not been injected flows into the supply raw water branch 52 that branches off at the branch point 51 from the supply raw water main pipe 50 and is installed in the supply raw water branch 52. It passes through the chemical injection control water treatment apparatus 10 and is treated to become treated water. The treated water passes through the treated water quality meter 20 installed in the treated water pipe 53 that follows the chemical treatment control water treatment apparatus 10, whereby the monitored measurement items of the treated water are continuously measured. Since the treated water pipe 53 following the treated water quality meter 20 is connected to the supply raw water main pipe 50 at the junction 54 on the main body water treatment device side from the branch point 51, the treated water passing through the treated water quality meter 20 is At the junction 54, the water flows into the supply raw water main pipe 50 and merges with the supply raw water. The treated water that has passed through the treated water quality meter 20 may be returned to a raw water tank (not shown) or treated as waste water.

  The measured values of each monitoring measurement item continuously measured by the treated water quality meter 20 are sent to the computing unit 30 at regular intervals that can be arbitrarily set. The computing unit 30 processes the measured values of each monitoring measurement item based on a predetermined method, converts them into computed values, compares them with the prescribed set values set in advance in the computing unit 30, and sets the set values. It is determined whether it is within the range.

  As a result, when the calculated value is within the set value range and the chemical is not injected into the supply raw water to be processed by the main body water treatment device 40, the chemical from the chemical storage 31 is not injected into the supply raw water. Supply raw water into which no chemical is injected is treated by the main body water treatment device 40 to become treated water.

  When the calculated value is within the set value range, but when a specific medicine is injected from the medicine storage tank 31 by the control of the medicine injection pump 32, the medicine injection pump 32 is controlled and the medicine storage tank 31. The supply of raw chemical water in which the injection of the injected chemicals is stopped and the injection of the chemicals is stopped is processed by the main body water treatment device 40 to become treated water.

  Conversely, if the calculated value is outside the set value range and no chemical has been injected into the raw feed water, the optimal chemical for removing the target to be removed specified by the monitoring measurement item outside the range is not available. The stored chemical storage tank 31 is selected, and an appropriate amount based on the injection calculation formula set in advance in the calculator 30 is supplied at the connection point 55 on the main body water treatment apparatus side from the junction 54 to the raw water main pipe 50 The raw material water is injected into the raw raw water through the chemical introduction pipe 56 connected to the main raw water treatment device 40 and becomes the treated water.

  The calculated value is outside the set value range, and the chemical for removing the removal target specified by the monitoring measurement item outside the range has been previously injected into the supply raw water from the chemical storage tank 31 under the control of the injection pump 32. In this case, an appropriate amount is calculated based on the injection calculation formula set in advance in the arithmetic unit 30, and it is compared with the injection amount that has been previously injected. The amount of chemical injected into the supply raw water through the chemical introduction pipe 56 connected to the supply raw water main pipe 50 is changed, and the supply raw water having the changed chemical injection amount is supplied to the main body water treatment device 40. To be treated.

  As described above, the chemical injection pump 32 is calculated based on the measured value of the treated water measured by the treated water quality meter 20 and the predetermined set value and injection calculation formula set in advance in the calculator 30. Since the selected chemical is injected into the supply raw water from the chemical storage tank 31 where the selected chemical is stored, the injection of the chemical injected into the supply raw water is stopped or the injection amount of the chemical is changed. The predetermined set value and the injection calculation formula to be set can be the set value and injection calculation formula for the treated water, and can be set without depending on the experience of the operator. Therefore, it is possible to eliminate variations in the quality of the treated water even if the operator who sets the predetermined set value and the injection calculation formula in the computing unit 30 is different, thereby preventing the waste of chemicals and obtaining a reliable and good treated water quality. Is possible.

  Moreover, the measured value of the treated water treated with the chemical treatment control water treatment apparatus 10 which is the same treatment method as the main body water treatment apparatus 40 and the predetermined set value of the supply raw water not injected with the chemical for removing the removal target Since the injection of the chemical is determined based on the injection arithmetic expression, it is possible to easily determine the existence of the removal target that cannot be removed by the main body water treatment device 40 alone, and selection of an appropriate chemical for removing the removal target. And can be easily combined.

  Further, the computing unit 30 makes a judgment based on the measured value of the treated water obtained by treating the raw water supplied with no chemical for removing the removal target with the chemical injection control water treatment device 10, the predetermined set value, and the injection arithmetic expression. Therefore, it is possible to stop the injection or change the injection amount of the chemical injected into the supply raw water after the quality of the water of the supply raw water becomes stable, and thus it is possible to reduce the amount of the chemical used. Further, since the measured value obtained by measuring the treated water obtained by treating a part of the supply raw water into which the chemical is not injected with the chemical treatment control water treatment apparatus 10 is used, the amount of chemical used can be reduced.

  Furthermore, the chemical injection pump 32 is controlled based on the measured values obtained by treating a part of the raw feed water with the chemical treatment control water treatment device 10, the predetermined set value, and the calculation injection formula. Therefore, the time lag is shorter than measuring the treated water of the main body water treatment device 40, and it becomes possible to inject the drug in a timely manner when the quality of the feed water is deteriorated.

  Furthermore, since the control water quality meter is only the treated water quality meter 20, it is possible to prevent the measurement accuracy from deteriorating due to the contamination of the meter and to eliminate the need for maintenance for the purpose of removing the contamination. Further, since it is not necessary to install an expensive supply raw water quality meter as a control water quality meter, the initial capital investment cost can be kept low.

  In this embodiment (FIG. 1), the treated water quality meter 20 is composed of a single meter, and there is only one type of removal target specified by the treated water quality meter 20, and the chemicals that remove the removal target are The case where there is one kind and therefore the chemical storage tank 31 is also constituted by a single number has been described. However, in some cases, a plurality of removal targets may be specified by the treated water quality meter 20 configured by a single meter, and in this case, the chemical storage tank 31 is configured by a plurality. On the contrary, even if the treated water / water quality meter 20 is composed of a plurality, the specified removal target may be one type, and in this case, the chemical storage tank may be composed of a single type. Therefore, whether the treated water quality meter 20 and the chemical storage tank 31 are each constituted by a single or plural may be appropriately determined by variously examining use conditions and the like.

DESCRIPTION OF SYMBOLS 1 Water treatment system 10 Water treatment apparatus for chemical injection control 20 Treated water quality meter 30 Calculator 31 Chemical storage tank 32 Chemical injection pump 40 Main body water treatment device 50 Supply raw water main pipe 51 Branch point 52 Supply raw water branch pipe 53 Process water pipe 54 Junction point 55 Connection point 56 Chemical injection pipe

Claims (5)

A water treatment device for chemical injection control that treats a part of the raw feed water into treated water;
A treated water quality meter for measuring treated water treated by the chemical injection control water treatment device;
The treated water quality values measured at the meter, the measurement value based on a predetermined method defined processing to the converted calculated value, and based on a predetermined set value for said calculated value, chemical injection pumps A calculator that controls the injection of an appropriate amount of the selected chemical from the chemical storage tank into the supply raw water or stops the injection of the chemical injected into the supply raw water or changes the injection amount of the chemical;
The same treatment method as the chemical treatment control water treatment device which treats the supply raw water in which a suitable amount of chemical is injected by the arithmetic unit or the injection of the injected chemical is stopped or the injection amount of the chemical is changed to be treated water A water treatment system comprising: a main body water treatment device.   The water treatment system according to claim 1, wherein the chemical injection control water treatment device and the main body water treatment device are membrane filtration devices.   The water treatment system according to claim 1, wherein the chemical injection control water treatment device and the main body water treatment device are sand filtration devices.   The water treatment system according to claim 1, wherein the chemical injection control water treatment device and the main body water treatment device are fiber filtration devices.   The water treatment system according to any one of claims 1 to 4, wherein the chemical treatment control water treatment device and the main body water treatment device include a pretreatment device.

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