Chemical injection device and chemical injection method

Abstract

To provide a chemical injection control device and a chemical injection control method capable of grasping a status of algae in treated water more quickly and accurately than before, select appropriate chemicals on the spot, and control their injection in water purification treatment.SOLUTION: A chemical injection device 10 is used to inject chemicals in a water purification system 1 that separates treated water 2 into solid-liquid to obtain treated water 7. The chemical injection device 10 consists of an optional filter 12 that filters the treated water, a first measuring means 14 capable of measuring a first photosynthetic dye concentration, a second measuring means 16 capable of measuring a second photosynthetic dye concentration, a chemical injection means 20 that injects chemicals, and a control part 40 which controls the injection rate of the chemicals injected by the chemical injection means 20 based on at least two measurements of the photosynthetic dye concentration which are capable of being measured by the first measuring means 14 and the second measuring means 16. The invention also provides a method for injecting chemicals into a water treatment system.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a chemical injection device and a chemical injection method, and more particularly to a chemical injection device and a chemical injection method for injecting chemicals into a water purification system that separates water to be treated into solid and liquid to obtain treated water. [Background technology]

[0002] Conventionally, in water purification treatment using surface water, groundwater, or the like as raw water, treated water is obtained by removing insoluble components from the raw water using solid-liquid separation techniques such as coagulation sedimentation and sand filtration.

[0003] When surface water such as river water, dam water, or lake water is used as raw water, various factors can cause problems with water purification. Non-Patent Document 1 discloses that algae that often increase in raw water have caused problems such as coagulation inhibition, unpleasant odors and tastes, coloring problems, filter blockages (increased resistance), and turbidity leakage of filtered water.

[0004] In response to these water purification problems, various countermeasures have been implemented, and the following countermeasures have been adopted as countermeasures involving the injection of chemicals into the water purification process, as shown in Non-Patent Document 2.

[0005] In other words, measures to combat coagulation inhibition include powdered activated carbon treatment, improving coagulation treatment through pre-chlorination, stopping pre-chlorination, strengthening coagulation treatment and injecting coagulation aids, and reducing the pH value during coagulation.

[0006] To address unpleasant odors and tastes, measures have been implemented such as powdered activated carbon treatment, stopping pre-chlorination, strengthening coagulation treatment and injecting coagulation aids, and reducing the pH value during coagulation.

[0007] To address filter blockage problems, measures have been implemented such as improving the coagulation process through pre-chlorination, strengthening the coagulation process and injecting coagulation aids, and reducing the pH value during coagulation.

[0008] Countermeasures against turbidity leakage in filtered water caused by picoplankton include powdered activated carbon treatment, improving coagulation treatment by pre-chlorination, stopping pre-chlorination, strengthening coagulation treatment and injecting coagulation aids, measures to reduce pH during coagulation, and two-stage coagulation treatment.

[0009] The degree of impact of algae on water purification problems varies depending on the type of algae. For example, coagulation inhibition is caused by all algae, while unpleasant odors and tastes are often caused by cyanobacteria. Also, picoplankton (phytoplankton measuring 0.2-2.0 μm) is believed to be the cause of filtered water turbidity leakage, which means that the size of the algae is a factor.

[0010] Patent Document 1 discloses a water purification process that involves pressure microfiltration after coagulation and sedimentation, in which the flow rate, pressure, water temperature, pH, turbidity, and chlorophyll a of the raw water are measured, and the dosage of deodorant and the stirring strength are controlled according to the measurement results. This allows for a reduction in the amount of coagulant used compared to conventional standard water purification processes.

[0011] Furthermore, Non-Patent Document 3 discloses a method for detecting algae using a microscope, which makes it possible to detect the type and size of algae.

[0012] Furthermore, Non-Patent Document 4 discloses a method for detecting algae using a fluorescent sensor, which allows rapid measurement of the concentrations of multiple photosynthetic pigments, such as chlorophyll and phycocyanin. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-260047 [Non-patent literature]

[0014] [Non-Patent Document 1] Sato Atsuhisa and Magara Yasuki, eds., "Algae Damage in Water Supply Systems - Seeking Safe and High-Quality Tap Water" May 15, 1996, 1st Edition, 1st Printing, pp. 1-12, Gihodo Publishing Co., Ltd. [Non-patent document 2] "Guide to Water Purification Treatment to Prevent Biological Damage," March 2006, Japan Water Works Association, pp. 126-139 [Non-patent document 3] Japan Water Works Association, Public Interest Incorporated Association, 2000 Edition, IV. Microorganisms, V. Biology, First Edition, First Printing, March 1, 2021, pp. 276-285, 412-417 [Non-patent document 4] Xylem Japan Co., Ltd. "ProDSS Multi Water Quality Sensor" catalog, April 21, 2022, downloadable online<URL:https: / / www.xylem-analytics.jp / media / pdfs / prodss-brochure-jpn.pdf> Summary of the Invention [Problem to be solved by the invention]

[0015] According to the water purification treatment of Patent Document 1, although the concentration of algae in general can be estimated by measuring chlorophyll a, it is not possible to estimate the type of algae. As mentioned above, the symptoms of water purification problems vary depending on the type of algae, so it is difficult to take appropriate measures against water purification problems caused by algae by measuring chlorophyll a alone.

[0016] Furthermore, the algae detection method using a microscope in Non-Patent Document 3 requires the sample to be examined under a microscope, which makes it impossible to detect algae on-site, and is time-consuming and labor-intensive.

[0017] According to the multi-water quality sensor in Non-Patent Document 4, it is possible to rapidly measure the concentrations of multiple photosynthetic pigments, but this multi-water quality sensor is thought to be applicable to lakes, rivers, etc., and is not intended for on-site use in water treatment.

[0018] Furthermore, although turbidity leakage in filtered water is caused by picoplankton, the picoplankton concentration in the treated water cannot be determined simply by measuring the photosynthetic pigments in the treated water.

[0019] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a chemical injection control device and a chemical injection control method that can grasp the state of algae in the water to be treated more quickly and accurately than conventional methods during water purification treatment, and can select appropriate chemicals on the spot and control their injection. [Means for solving the problem]

[0020] The inventors have conducted extensive research to achieve the above-mentioned objectives and have found that by measuring the photosynthetic pigment concentrations in the unfiltered and filtered water to be treated, it is possible to grasp the status of algae in general that cause coagulation inhibition in the water to be treated, and of picoplankton that cause turbidity leakage in the filtered water, and that by measuring the concentrations of two photosynthetic pigments in the water to be treated, it is possible to grasp the status of algae in general that cause coagulation inhibition in the water to be treated, and of cyanobacteria that cause unpleasant odors and tastes.

[0021] The researchers then discovered that by measuring on-site at least two of the four categories of photosynthetic pigment concentration (2 categories x 2 categories of unfiltered / filtered water), it is possible to quickly and comprehensively grasp the condition of the algae that cause problems with the purification of the water being treated, and that by selecting and injecting chemicals appropriate to the condition of the algae, it is possible to quickly improve the quality of the treated water, thereby completing the present invention.

[0022] That is, the object is to provide a chemical injection device for injecting chemicals into a water purification system that separates water to be treated into solid and liquid to obtain treated water, It has been found that this can be achieved by a chemical injection device for injecting chemicals into a water purification system, comprising: a filter for filtering water to be treated; a first measuring means capable of measuring the concentration of at least one first photosynthetic pigment in the unfiltered water to be treated and in the water to be treated after filtration by the filter; a second measuring means capable of measuring the concentration of at least one second photosynthetic pigment in the unfiltered water to be treated and in the water to be treated after filtration by the filter; a chemical injection means for injecting chemicals into the water purification system; and a control unit for controlling the injection rate of the chemical injected by the chemical injection means based on at least two measured values ​​of the photosynthetic pigment concentrations measurable by the first measuring means and the second measuring means.

[0023] A preferred embodiment of the method for treating wastewater generated in water purification according to the present invention is as follows. (1) The solid-liquid separation of the water to be treated is achieved by subjecting the water to coagulation and sedimentation treatment in the coagulation and sedimentation section to separate it into a sediment and a liquid portion, and then filtering the resulting liquid portion in the filtration section to obtain treated water. (2) The photosynthetic pigment concentration that can be measured by the first measuring means is the pigment concentration of chlorophyll a. (3) The photosynthetic pigment concentration that can be measured by the second measurement means is the pigment concentration of phycocyanin. (4) The apparatus has a filter for filtering the water to be treated, and the first measuring means is capable of measuring the chlorophyll a pigment concentration in the unfiltered water to be treated and the chlorophyll a pigment concentration in the water to be treated after filtration by the filter. The second measuring means is capable of measuring the phycocyanin pigment concentration in the unfiltered water to be treated and the phycocyanin pigment concentration in the water to be treated after filtration. The control unit controls the amount of chemical to be injected by the chemical injection means based on at least two measured values ​​of a total of four pigment concentrations that can be measured by the first measuring means and the second measuring means. (5) The chemical injection means is one or more selected from the group consisting of a powdered coal injection means into the water to be treated, a sodium hypochlorite injection means into the coagulation and sedimentation section, a sodium hypochlorite injection means into the liquid section, an inorganic coagulant injection means into the coagulation and sedimentation section, an inorganic coagulant injection means into the liquid section, and a polymer coagulant injection means into the coagulation and sedimentation section. (6) The pore size of the filter is 1 μm or more and 10 μm or less. (7) The first measuring means and the second measuring means detect the fluorescence.

[0024] The above object is also to provide a chemical injection method for injecting a chemical into a water purification system in which water to be treated is subjected to a coagulation and sedimentation treatment in a coagulation and sedimentation unit to separate it into a precipitate and a liquid portion, and the obtained liquid portion is filtered in a filtration unit to obtain treated water, This can also be achieved by a chemical injection method comprising: a filtration step of arbitrarily filtering the water to be treated; a measurement step of measuring at least two photosynthetic pigment concentrations, namely, the concentration of a first photosynthetic pigment in the filtered water to be treated, the concentration of a first photosynthetic pigment in the unfiltered water to be treated, the concentration of a second photosynthetic pigment in the filtered water to be treated, and the concentration of a second photosynthetic pigment in the unfiltered water to be treated; an injection rate determination step of determining an injection rate of a chemical based on the measured values ​​of the at least two photosynthetic pigment concentrations measured in the measurement step; and an injection step of injecting the chemical into the water purification system at the injection rate determined in the injection rate determination step.

[0025] Furthermore, the above object is to provide a chemical injection device for injecting chemicals into a water purification system that separates water to be treated into solid and liquid to obtain treated water, This can also be achieved by a chemical injection device comprising: a phycocyanin measurement means capable of measuring the pigment concentration of phycocyanin in unfiltered treated water; a chemical injection means for injecting a chemical into the water purification system; and a control unit for controlling the injection rate of the chemical injected by the chemical injection means based only on the measured value of the pigment concentration of phycocyanin in the unfiltered treated water measured by the phycocyanin measurement means. [Effects of the Invention]

[0026] According to the present invention, the type of algae in the water to be treated can be quickly determined on the spot using at least two measured values ​​of photosynthetic pigment concentration that can be measured by the first measuring means and the second measuring means, and the control unit can control the injection of chemicals on the spot based on the determined status of the type of algae in the water to be treated.

[0027] Furthermore, when the chemical injection device is equipped with a filter, the injection of chemicals can be controlled on the spot based on the type and / or size of algae in the treated water using at least two of the four total measured values: two measured values ​​of photosynthetic pigment concentration that can be measured by the first measuring means and the second measuring means in unfiltered treated water, and two measured values ​​of photosynthetic pigment concentration that can be measured by the first measuring means and the second measuring means in treated water after filtration through a filter.

[0028] Therefore, in water purification treatment, the state of algae in the water to be treated can be grasped more quickly and accurately than before, and an appropriate chemical can be selected on the spot and its injection can be controlled. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a schematic diagram illustrating a chemical injection device 10 of the present invention. [Figure 2] 4 is a flowchart illustrating a first example of control by the control unit 40 of the chemical injection device 10 of the present invention. [Figure 3] 10 is a flowchart illustrating a second example of control by the control unit 40 of the chemical injection device 10 of the present invention. [Figure 4] 10 is a flowchart illustrating a third example of control by the control unit 40 of the chemical injection device 10 of the present invention. [Figure 5] 10 is a flowchart illustrating a fourth example of control by the control unit 40 of the chemical injection device 10 of the present invention. [Figure 6] 10 is a flowchart illustrating a fifth example of control by the control unit 40 of the chemical injection device 10 of the present invention. [Figure 7] 1 is a schematic diagram illustrating a chemical injection device 50 of the present invention. [Figure 8] 4 is a flowchart illustrating an example of control by a control unit 42 of a chemical injection device 50 of the present invention. [Figure 9] 1 is a flowchart illustrating a chemical injection method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0030] <Chemical injection device> The chemical injection device of the present invention is a chemical injection device for performing solid-liquid separation of water to be treated and injecting chemicals into a water purification system. Prior to describing the chemical injection device, the water purification system will first be described. FIG. 1 is a schematic diagram illustrating a chemical injection device 10 of the present invention. As shown in the figure, in the water purification system 1, solid-liquid separation of water to be treated 2 is performed by, for example, rapid filtration. Note that the solid-liquid separation of water to be treated 2 is not limited to rapid filtration, and may also be, for example, direct filtration or slow filtration.

[0031] Specifically, solid-liquid separation of the water to be treated 2 by the rapid filtration method is carried out by subjecting the water to be treated 2 to coagulation and sedimentation treatment in the coagulation and sedimentation section 3 to separate it into a precipitate 4 and a liquid part 5, and then filtering the obtained liquid part 5 in the filtration section 6 to obtain treated water.

[0032] Raw water for a water supply is used as the water to be treated 2. Examples of raw water for a water supply include river water, groundwater, dam lake water, lake water, subsurface water, and groundwater, but the present invention is particularly suitable for river water, dam lake water, and lake water, which may cause water purification problems due to algae.

[0033] The coagulation and sedimentation section 3 includes, for example, a coagulation tank to which a coagulant is added and which mixes and stirs the added coagulant with the raw water to coagulate the turbid matter in the raw water, and a settling tank to settle the flocs obtained by coagulation in the coagulation tank. The sediment 4 that has settled to the bottom of the settling tank is periodically scraped up and discharged using a clarifier or the like, and the liquid portion 5 is sent to the filtration section 6.

[0034] The filtration section 6 is, for example, a rapid sand filter having a sand layer. When the liquid section 5 passes through this sand layer, small flocs that did not settle in the liquid section 5 are removed, and treated water 7 is obtained.

[0035] As shown in FIG. 1, a chemical injection device 10 of the present invention includes a filter 12, a first measuring means 14, a second measuring means 16, a chemical injection means 20, and a control unit 40.

[0036] In the present invention, the filter 12 is an optional component and is used to filter the water to be treated 2. The pore size of the filter 12 may be any size that can filter out picoplankton (phytoplankton of 0.2 to 2.0 μm) from algae in general, but for example, the pore size of the filter 12 is 1 μm or more and 20 μm or less, preferably 1 μm or more and 10 μm or less, and particularly preferably 2 μm or more and 7 μm or less.

[0037] By filtering the treated water 2 with a filter 12 and measuring the filtered treated water 2' with the first measuring means and / or the second measuring means described below, it becomes possible to determine the concentration of picoplankton present in the treated water from the concentration of photosynthetic pigments in the filtered treated water.

[0038] The first measuring means 14 is a means capable of measuring the concentration of at least one first photosynthetic pigment in the unfiltered water to be treated 2 and the water to be treated 2 after filtration by the filter 12. The first photosynthetic pigment can be selected from pigments contained in photosynthetic organisms, such as chlorophyll, carotenoids, and phycobilins.

[0039] Examples of chlorophyll include chlorophyll a, chlorophyll b, chlorophyll c1, c2, c3, chlorophyll d, chlorophyll f, and bacteriochlorophyll a to g.

[0040] Examples of carotenoids include β-carotene, violaxanthin, anthraxanthin, and zeaxanthin.

[0041] Examples of phycobilins include phycocyanin, allophycocyanin, phycoerythrin, and phycoerythrocyanin.

[0042] The first measurement means 14 may be any means capable of measuring the concentration of the first photosynthetic pigment, and examples thereof include a means for measuring by fluorometry, which detects the fluorescence emitted by a sample when irradiated with excitation light, and a means for measuring by absorptiometry (i.e., a method for measuring the degree of light absorption (absorbance) by a target substance when the sample reflects light irradiated thereon).

[0043] In the present invention, the first measuring means 14 is preferably a means for measuring by the former fluorometry, since the fluorometry method has excellent sensitivity and can measure photosynthetic pigments such as chlorophyll a at low concentrations.

[0044] Among the various photosynthetic pigments mentioned above, the photosynthetic pigment concentration that can be measured by the first measurement means 14 is preferably the pigment concentration of chlorophyll a, which is a photosynthetic pigment contained in algae and plants in general, and from the viewpoint that measuring this concentration makes it possible to estimate the concentration of all algae. When measuring chlorophyll a, for example, the irradiated light wavelength (excitation wavelength) is in the range of 455 to 485 nm, and the received light wavelength (fluorescence wavelength) is in the range of 640 to 750 nm, and from the viewpoint of sensitivity, it is preferably in the range of 665 to 705 nm.

[0045] When the first measuring means 14 is used to measure the concentration of a photosynthetic pigment other than chlorophyll a, the wavelength of the irradiated light and the wavelength of the received light may be appropriately set to match that photosynthetic pigment.

[0046] The second measuring means 16 is a means capable of measuring the concentration of at least one second photosynthetic pigment in the unfiltered treated water 2 and the treated water 2' after filtration by the filter 12. Assuming that the second photosynthetic pigment is a photosynthetic pigment different from the first photosynthetic pigment, it can be selected from pigments contained in photosynthetic organisms, such as chlorophyll, carotenoids, and phycobilins, similar to the first photosynthetic pigment described above.

[0047] The photosynthetic pigment concentration that can be measured by the second measurement means 16 is preferably the pigment concentration of phycocyanin, which is a photosynthetic pigment found only in cyanobacteria among the various photosynthetic pigments mentioned above, and measuring this concentration makes it possible to estimate the concentration of cyanobacteria that cause unpleasant odors and tastes. When measuring phycocyanin, for example, the irradiated light wavelength (excitation wavelength) is in the range of 570 to 630 nm, and the received light wavelength (fluorescence wavelength) is in the range of 650 to 750 nm, preferably 665 to 705 nm from the viewpoint of sensitivity.

[0048] When measuring the concentration of a photosynthetic pigment other than phycocyanin using the second measurement means 16, the wavelength of the irradiated light and the wavelength of the received light may be appropriately set to match the photosynthetic pigment.

[0049] If both the first measurement means 14 and the second measurement means 16 are means for measuring by fluorometry, one fluorescence spectrophotometer can be used as the first measurement means 14 and the second measurement means 16.

[0050] Similarly, if the first measurement means 14 and the second measurement means 16 are both means for measurement by absorptiometry, one absorptiometer can be used as the first measurement means 14 and the second measurement means 16.

[0051] The first measuring means 14 and the second measuring means 16 are controlled by a control unit 40, which will be described later.

[0052] The chemical injection means 20 is a means for injecting chemicals into the above-mentioned water purification system 1. The chemicals are injected into appropriate locations in the water purification system 1 depending on the type of chemical.

[0053] Examples of chemicals include, but are not limited to, powdered activated carbon, sodium hypochlorite (chlorine), inorganic flocculants, polymer flocculants, and flocculation aids.

[0054] Among these, examples of inorganic flocculants include aluminum sulfate (sulfate band) and polyaluminum chloride. Examples of polymer flocculants used in water purification treatment applications include polyacrylamide-based polymer flocculants and polyacrylic acid ester-based polymer flocculants. Examples of flocculation aids include flocculation aids and pH adjusters. Examples of flocculation aids include activated silicic acid, sodium alginate, red clay, bentonite, etc. pH adjusters are added for the purpose of lowering the pH value of raw water (water to be treated 2) that has risen due to the carbon dioxide assimilation action of algae, and therefore include acids such as sulfuric acid and carbon dioxide (carbon dioxide gas).

[0055] Among these, it is preferable that the chemical injection means 20 is one or more selected from the group consisting of a powdered coal injection means 22 into the water to be treated 2, a sodium hypochlorite (NaClO) injection means 24 into the coagulation and sedimentation section 3, a sodium hypochlorite (NaClO) injection means 24 into the liquid section 5, an inorganic coagulant injection means 26 into the coagulation and sedimentation section 3, an inorganic coagulant injection means 26 into the liquid section 5, and a polymer coagulant injection means 28 into the coagulation and sedimentation section 3.

[0056] In the chemical injection device 10 shown in FIG. 1, the chemical injection means 20 comprises a powdered coal injection means 22, a sodium hypochlorite (NaClO) injection means 24, an inorganic flocculant injection means 26, and a polymer flocculant injection means 28, but it is not essential that the chemical injection means of the present invention comprises all of these, and if necessary, it may also comprise a flocculation aid injection means such as a flocculation aid injection means or a pH adjuster injection means.

[0057] In the chemical injection device 10 of the present invention, the injection of chemicals from each chemical injection means 22, 24, 26, 28 into the treated water 2, the coagulation and sedimentation section 3, and the liquid section 5 is performed by signals from the control section 40, for example, by controlling the operation of the chemical transport pumps (not shown) of each chemical injection means 22, 24, 26, 28 and the opening and closing of valves (not shown) in the piping.

[0058] The control unit 40 is a computer equipped with a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), etc. The control unit 40 loads a program stored in the ROM onto the RAM and causes the CPU to execute the corresponding process. Note that the program is not limited to being stored in the ROM, and may be stored in an NVRAM (Non-Volatile Random Access Memory).

[0059] The control unit 40 controls the injection rate of the chemical injected by the chemical injection means 20 based on at least two measured values ​​of the photosynthetic pigment concentration that can be measured by the first measurement means 14 and the second measurement means 16.

[0060] The control by the control unit 40 will be described below with reference to FIGS. (First Example of Control by the Control Unit 40 of the Chemical Injection Device 10 of the Present Invention) FIG. 2 is a flowchart illustrating a first example of control by the control unit 40 of the chemical injection device 10 of the present invention.

[0061] In this example, only the first measurement means 14 is used, and the second measurement means 16 is not used. Furthermore, as the chemical injection means 20, only the inorganic flocculant injection means 26 to the coagulation-sedimentation section 3 and the inorganic flocculant injection means 26 to the liquid section 5 are used. Furthermore, in this example, the first measurement means 14 measures the pigment concentration of chlorophyll a by detecting fluorescence.

[0062] First, in step S201, the first measurement means 14 measures the chlorophyll-a concentrations of the unfiltered water to be treated 2 and the water to be treated 2' after filtration by the filter 12. Specifically, when the control unit 40 is powered on and started up, the control unit 40 sends a signal to the first measurement means 14. In response to this signal, excitation light with an excitation wavelength in the range of 455 to 485 nm is irradiated onto the unfiltered water to be treated 2 and the water to be treated 2' after filtration by the filter 12 in the first measurement means 14.

[0063] Then, in the first measurement means 14, the fluorescence emitted by the water to be treated 2, 2' (and substances such as algae in the water to be treated 2, 2') that absorbed the excitation light is dispersed into a fluorescence wavelength range of 640 to 750 nm. The control unit 40 substitutes the fluorescence intensity in the fluorescence wavelength range of 640 to 750 nm into a previously prepared relational equation between fluorescence intensity and chlorophyll-a concentration to determine the chlorophyll-a concentration in the water to be treated 2, 2'. After measurement, the water to be treated 2, 2' supplied to the first measurement means 14 may be mixed with the water to be treated 2 in the water purification system 1 or may be discharged (step S201).

[0064] Next, in step S202, the control unit 40 determines whether the chlorophyll-a concentration in the unfiltered water to be treated 2 is less than a threshold value. The chlorophyll-a concentration in the unfiltered water to be treated 2 is an index of the total algae concentration in the water to be treated 2, and in step S202, the threshold value can be selected, for example, from a range of 0.01 to 5 mg / L, and is preferably from a range of 0.1 to 1 mg / L. If the chlorophyll-a concentration in the unfiltered water to be treated 2 is less than the threshold value (YES), the process proceeds to step S203; if it is equal to or greater than the threshold value (NO), the process proceeds to step S206 (all steps S202).

[0065] In step S203, the control unit 40 determines whether the chlorophyll-a concentration in the water to be treated 2' after filtration by the filter 12 is less than a threshold value. The chlorophyll-a concentration in the water to be treated 2' after filtration is an index of the picoplankton concentration in the water to be treated 2 that can lead to turbidity leakage of the filtered water. In step S203, the threshold value can be selected, for example, from a range of 0.01 to 0.5 mg / L, and is preferably from a range of 0.05 to 0.2 mg / L. If the chlorophyll-a concentration in the water to be treated 2' after filtration is less than the threshold value (YES), the process proceeds to step S204. If the chlorophyll-a concentration is equal to or greater than the threshold value (NO), the process proceeds to step S205 (all steps S203).

[0066] In step S204, if the amount of inorganic flocculant injected from the inorganic flocculant injection means 26 to the coagulation-sedimentation section 3 is being increased, the control section 40 sends a signal to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 stops the increase and reduces the amount of inorganic flocculant injected into the coagulation-sedimentation section 3. The base injection rate of the inorganic flocculant to the coagulation-sedimentation section 3 when this increase is stopped is, for example, in the range of 10 to 50 mg / L, and preferably in the range of 15 to 35 mg / L.

[0067] Furthermore, if the inorganic flocculant injection means 26 is injecting inorganic flocculant into the liquid section 5, a signal is sent to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 stops injecting the inorganic flocculant into the liquid section 5 (step S204).

[0068] In step S205, which is the next step from step S203, if the control unit 40 is increasing the amount of inorganic flocculant injected from the inorganic flocculant injection means 26 into the coagulation-sedimentation unit 3, it sends a signal to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 stops the increase and reduces the amount of inorganic flocculant injected into the coagulation-sedimentation unit 3. The base injection rate of the inorganic flocculant into the coagulation-sedimentation unit 3 when this increase is stopped is preferably the same as the injection rate in step S204.

[0069] Furthermore, if inorganic flocculant injection means 26 is not injecting inorganic flocculant into liquid section 5, control section 40 sends a signal to inorganic flocculant injection means 26, and based on this signal, inorganic flocculant injection means 26 starts injecting inorganic flocculant into liquid section 5. The injection rate of inorganic flocculant into liquid section 5 is, for example, in the range of 0.1 to 5 mg / L, and preferably in the range of 0.5 to 3 mg / L. Furthermore, if inorganic flocculant injection means 26 is injecting inorganic flocculant into liquid section 5, control section 40 does not send any particular signal, and inorganic flocculant injection means 26 continues injecting inorganic flocculant into liquid section 5 (the above is step S205).

[0070] In step S206, which follows step S202, the control unit 40 determines whether the chlorophyll-a concentration in the water to be treated 2' after filtration by the filter 12 is less than a threshold value. The threshold value in step S206 is preferably the same as the threshold value in step S203. If the chlorophyll-a concentration in the water to be treated 2' after filtration is less than the threshold value (YES), the process proceeds to step S207; if it is equal to or greater than the threshold value (NO), the process proceeds to step S208 (step S206).

[0071] In step S207, the control unit 40 sends a signal to the inorganic coagulant injection means 26, and based on this signal, the inorganic coagulant injection means 26 adjusts to increase the injection rate of inorganic coagulant from the inorganic coagulant injection means 26 to the coagulation and sedimentation section 3 in accordance with a predetermined relationship between the chlorophyll a concentration in the unfiltered treated water 2 and the optimal injection rate of inorganic coagulant to the coagulation and sedimentation section 3.

[0072] Here, the relationship between the predetermined chlorophyll-a concentration in the unfiltered water to be treated 2 and the optimum injection rate of the inorganic coagulant into the coagulation-sedimentation section 3 will be described.

[0073] Of the photosynthetic pigments, chlorophyll a is contained in all algae, so the chlorophyll a concentration is correlated with the algae body concentration of all algae, and there is a correlation between the algae body concentration of all algae and the amount of inorganic coagulant required.Therefore, by obtaining a relational equation between the chlorophyll a concentration and the optimal inorganic coagulant injection rate into the coagulation and sedimentation section 3 in advance, and substituting the determined chlorophyll a concentration value in the unfiltered treated water 2 measured using the first measurement means 14 into the above relational equation, the optimal inorganic coagulant injection rate into the coagulation and sedimentation section 3 can be calculated.

[0074] In addition, if the injection rate of inorganic coagulant from inorganic coagulant injection means 26 to coagulation settling section 3 has already been increased via step S207 and the process returns to step S207, the increased injection rate of inorganic coagulant may be reduced when the optimal injection rate is recalculated according to the relational expression. Therefore, in FIG. 2, when the previous PACl injection amount (i.e., the injection amount of inorganic coagulant to coagulation settling section 3) is increased according to the relational expression, this also includes the case where the previous PACl injection amount is reduced according to the relational expression. Hereinafter, in FIGS. 2 to 6 and 8, the same applies when the injection rate of each chemical follows the relational expression.

[0075] Also, in step S207, if the inorganic flocculant injection means 26 is injecting inorganic flocculant into the liquid section 5, the control unit 40 sends a signal to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 stops injecting the inorganic flocculant into the liquid section 5 (this concludes step S207).

[0076] In step S208, which is the next step from step S206, the control unit 40 sends a signal to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 increases or decreases the injection rate of the inorganic flocculant from the inorganic flocculant injection means 26 to the coagulation sedimentation unit 3 in accordance with a predetermined relational expression between the chlorophyll-a concentration in the unfiltered water to be treated 2 and the optimal injection rate of the inorganic flocculant to the coagulation sedimentation unit 3. It is preferable to use the same relational expression as that of step S207 as this relational expression.

[0077] Furthermore, in step S208, if the inorganic flocculant injection means 26 is not injecting inorganic flocculant into the liquid section 5, the control unit 40 sends a signal to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 starts injecting the inorganic flocculant into the liquid section 5. The injection rate of the inorganic flocculant into the liquid section 5 is preferably the same as the injection rate in step S205. Furthermore, if the inorganic flocculant injection means 26 is injecting inorganic flocculant into the liquid section 5, the control unit 40 does not send any particular signal, and the inorganic flocculant injection means 26 continues injecting the inorganic flocculant into the liquid section 5 (this concludes step S208).

[0078] In this example, after steps S204, S205, S207, and S208 are completed, the chemical injection device 10 returns to step S201 and repeats the same control while the water purification treatment is being performed by the coagulation treatment system 1, but in some cases, the control may end after steps S204, S205, S207, and S208 are completed. The same applies to the controls in Figures 3 to 6 and 8.

[0079] In this example, the control by the control unit 40 is performed when the concentration of cyanobacteria in the treated water 2 is not a problem, but the concentration of total algae and the concentration of picoplankton are. When the concentration of total algae exceeds a threshold, the injection rate of inorganic flocculant into the coagulation and settling unit 3 is increased to resolve the problem of poor coagulation. When the picoplankton concentration exceeds a threshold, a small amount of inorganic flocculant is injected into the liquid unit 5 to resolve the problem of turbidity leakage in the filtered water. Furthermore, because injection of inorganic flocculant into the liquid unit 5 leads to an increase in the resistance in the filtration unit 6, the problem of poor coagulation caused by total algae that does not cause turbidity leakage in the filtered water is addressed by injecting inorganic flocculant into the coagulation and settling unit 3 (i.e., no inorganic flocculant is injected into the liquid unit 5 at this time). Only when the picoplankton concentration exceeds the threshold, a pinpoint injection of a small amount of inorganic flocculant into the liquid unit 5 is performed.

[0080] (Second Example of Control by Control Unit 40 of Chemical Injection Device 10 of the Present Invention) FIG. 3 is a flowchart illustrating a second example of control by the control unit 40 of the chemical injection device 10 of the present invention.

[0081] In this example, both the first measuring means 14 and the second measuring means 16 are used. Also, as the chemical injection means 20, an inorganic coagulant injection means 26 to the coagulation-sedimentation section 3, a powdered coal injection means 22 to the water to be treated 2, and a sodium hypochlorite (NaClO) injection means 24 to the coagulation-sedimentation section 3 are used.

[0082] First, in step S211, the first measurement means 14 measures the chlorophyll-a concentration of the unfiltered water to be treated 2, and the second measurement means 16 measures the phycocyanin concentration of the unfiltered water to be treated 2. Specifically, when the control unit 40 is powered on and started up, the control unit 40 sends a signal to the first measurement means 14 and the second measurement means 16. The measurement of the chlorophyll-a concentration by the first measurement means 14 is the same as step S201 in the first example, so a description thereof will be omitted.

[0083] In response to a signal from the control unit 40, the second measuring means 16 irradiates the unfiltered water 2 to be treated in the second measuring means 16 with excitation light having an excitation wavelength in the range of 570 to 630 nm.

[0084] Then, in the second measurement means 16, the fluorescence emitted by the water to be treated 2 (and substances such as algae in the water to be treated 2) that have absorbed the excitation light is dispersed into a range of fluorescence wavelengths from 650 to 750 nm. The control unit 40 substitutes the fluorescence intensity in the range of fluorescence wavelengths from 650 to 750 nm into a previously prepared relational equation between fluorescence intensity and phycocyanin concentration to determine the phycocyanin concentration in the water to be treated 2. Note that the water to be treated 2 supplied to the second measurement means 16 may also be mixed with the water to be treated 2 in the water purification system 1 after measurement, or may be discharged (step S211).

[0085] Next, in step S212, the control unit 40 determines whether the chlorophyll-a concentration in the unfiltered water to be treated 2 is less than a threshold value. In step S212, the threshold value can be selected, for example, from the range of 0.01 to 5 mg / L, and is preferably in the range of 0.1 to 1 mg / L. If the chlorophyll-a concentration in the unfiltered water to be treated 2 is less than the threshold value (YES), the process proceeds to step S213; if it is equal to or greater than the threshold value (NO), the process proceeds to step S214 (all, step S212).

[0086] In step S213, when sodium hypochlorite (NaClO) is being injected from the sodium hypochlorite (NaClO) injection means 24 into the coagulation and sedimentation unit 3, the control unit 40 sends a signal to the sodium hypochlorite (NaClO) injection means 24, and based on this signal, the sodium hypochlorite (NaClO) injection means 24 stops its injection.

[0087] In addition, when the powdered coal injection means 22 is injecting powdered activated carbon into the water to be treated 2, the control unit 40 sends a signal to the powdered coal injection means 22, and based on this signal, the powdered coal injection means 22 stops injecting powdered activated carbon into the water to be treated 2.

[0088] Furthermore, when the control unit 40 is increasing the amount of inorganic flocculant injected from the inorganic flocculant injection means 26 into the coagulation-sedimentation unit 3, it sends a signal to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 stops the increase and reduces the amount of inorganic flocculant injected into the coagulation-sedimentation unit 3. Note that the base injection rate of the inorganic flocculant into the coagulation-sedimentation unit 3 when this increase is stopped is, for example, in the range of 10 to 50 mg / L, and preferably in the range of 15 to 35 mg / L (step S213).

[0089] In step S214, which follows step S212, it is determined whether the phycocyanin concentration in the unfiltered water to be treated 2 is less than a threshold value. The phycocyanin concentration in the unfiltered water to be treated 2 is an index of the concentration of cyanobacteria in the water to be treated 2, and in step S214, the threshold value can be selected, for example, from the range of 0.01 to 5 mg / L, preferably from the range of 0.1 to 1 mg / L. If the phycocyanin concentration in the unfiltered water to be treated 2 is less than the threshold value (YES), the process proceeds to step S215; if it is equal to or greater than the threshold value (NO), the process proceeds to step S216 (all steps S214).

[0090] In step S215, the control unit 40 sends a signal to the sodium hypochlorite (NaClO) injection means 24, and based on this signal, the sodium hypochlorite (NaClO) injection means 24 injects sodium hypochlorite (NaClO) from the sodium hypochlorite (NaClO) injection means 24 into the coagulation and sedimentation unit 3 in accordance with a predetermined relationship between the chlorophyll-a concentration in the unfiltered treated water 2 and the optimal injection rate of sodium hypochlorite (NaClO) into the coagulation and sedimentation unit 3.

[0091] Here, the relationship between the predetermined chlorophyll-a concentration in the unfiltered water to be treated 2 and the optimum injection rate of sodium hypochlorite (NaClO) into the coagulation-sedimentation section 3 will be described.

[0092] As already mentioned, the chlorophyll a concentration is correlated with the algae body concentration of algae in general, and there is also a correlation between the algae body concentration of algae in general and the amount of sodium hypochlorite (NaClO) required. Therefore, by obtaining a relational expression between the chlorophyll a concentration and the optimal sodium hypochlorite (NaClO) injection rate into the coagulation and sedimentation section 3 in advance, and then substituting the determined chlorophyll a concentration in the unfiltered treated water 2 measured by the first measuring means 14 into the above relational expression, the optimal sodium hypochlorite (NaClO) injection rate into the coagulation and sedimentation section 3 can be calculated.

[0093] In step S215, the control unit 40 sends a signal to the powdered coal injection means 22, and based on this signal, the powdered coal injection means 22 injects powdered activated carbon from the powdered coal injection means 22 into the coagulation and sedimentation unit 3 in accordance with a predetermined relationship between the phycocyanin concentration in the unfiltered water to be treated 2 and the optimal injection rate of powdered activated carbon into the water to be treated 2.

[0094] Here, the relationship between the predetermined phycocyanin concentration in the unfiltered water to be treated 2 and the optimum injection rate of powdered activated carbon into the water to be treated 2 will be explained.

[0095] The phycocyanin concentration is correlated with the concentration of cyanobacteria, and there is also a correlation between the concentration of cyanobacteria and the amount of powdered activated carbon required for the water to be treated 2. Therefore, by obtaining a relational expression between the phycocyanin concentration and the optimum powdered activated carbon injection rate for the water to be treated 2 in advance, and then measuring the phycocyanin concentration in the unfiltered water to be treated 2 using the second measuring means 14 and substituting the determined value for this in the relational expression, the optimum injection rate of powdered activated carbon for the water to be treated 2 can be calculated.

[0096] Furthermore, in step S215, the control unit 40 sends a signal to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 increases the injection rate of the inorganic flocculant from the inorganic flocculant injection means 26 to the coagulation sedimentation unit 3 in accordance with a relational expression between the chlorophyll-a concentration in the unfiltered treated water 2, which has been determined in advance, and the optimal injection rate of the inorganic flocculant to the coagulation sedimentation unit 3. The explanation of the relational expression has already been given in step S207 of the first example, so the explanation will be omitted here (this concludes step S215).

[0097] In step S216, which is the next step from step S214, if the control unit 40 is injecting sodium hypochlorite (NaClO) from the sodium hypochlorite (NaClO) injection means 24 into the coagulation and sedimentation unit 3, it sends a signal to the sodium hypochlorite (NaClO) injection means 24, and based on this signal, the sodium hypochlorite (NaClO) injection means 24 stops its injection.

[0098] Furthermore, in step S216, the control unit 40 sends a signal to the powdered coal injection means 22, and based on this signal, the powdered coal injection means 22 increases the injection rate of powdered activated carbon from the powdered coal injection means 22 to the coagulation and sedimentation unit 3 in accordance with a predetermined relational expression between the phycocyanin concentration in the unfiltered water to be treated 2 and the optimal injection rate of powdered activated carbon to the water to be treated 2. Note that the powdered coal injection rate in step 216 is greater than the powdered coal injection rate in step S215, and therefore the relational expression here can be a relational expression obtained by adding or multiplying a predetermined coefficient to the relational expression in step S215.

[0099] Furthermore, in step S216, the control unit 40 sends a signal to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 increases or decreases the injection rate of the inorganic flocculant from the inorganic flocculant injection means 26 to the coagulation sedimentation unit 3 in accordance with a predetermined relational expression between the chlorophyll-a concentration in the unfiltered treated water 2 and the optimal injection rate of the inorganic flocculant to the coagulation sedimentation unit 3. It is preferable to use the same relational expression as in step S215 (this concludes step S216).

[0100] The control by the control unit 40 in this example shows control in a case where the concentration of algae cells of total algae and the concentration of algae cells of cyanobacteria are problematic, and the concentration of picoplankton is not a problem in the treated water 2. In this example, when the concentration of algae cells of total algae becomes high, poor coagulation is addressed by injecting chlorine (so-called pre-chlorination) into the coagulation-sedimentation unit 3, increasing the amount of inorganic coagulant in the coagulation-sedimentation unit 3, and adding a small amount of powdered activated carbon to the coagulation-sedimentation unit 3, but when the concentration of algae cells of cyanobacteria, which causes an unpleasant odor or taste, also becomes high at the same time, the addressing is done by stopping pre-chlorination, increasing the amount of powdered activated carbon, and increasing the amount of inorganic coagulant.

[0101] This control is intended to remove unpleasant odor and taste substances present in the cyanobacteria by coagulation and sedimentation without allowing them to flow out of the algae when the concentration of total algae and the concentration of cyanobacteria increase simultaneously.

[0102] (Third Example of Control by Control Unit 40 of Chemical Injection Device 10 of the Present Invention) FIG. 4 is a flowchart illustrating a third example of control by the control unit 40 of the chemical injection device 10 of the present invention.

[0103] In this example, both the first measuring means 14 and the second measuring means 16 are used. Also, as the chemical injection means 20, an inorganic flocculant injection means 26 into the coagulation settling section 3, an inorganic flocculant injection means 26 into the liquid section 5, and a powdered coal injection means 22 into the water to be treated 2 are used.

[0104] First, in step S221, the first measurement means 14 measures the chlorophyll-a concentrations of the unfiltered water to be treated 2 and the water to be treated 2' after filtration with the filter 12, respectively, and the second measurement means 16 measures the phycocyanin concentrations of the unfiltered water to be treated 2 and the water to be treated 2' after filtration with the filter 12, respectively. Specifically, when the control unit 40 is powered on and started up, the control unit 40 sends signals to the first measurement means 14 and the second measurement means 16, and the control unit determines the chlorophyll-a concentration and the phycocyanin concentration based on the measurement results of the first measurement means 14 and the second measurement means 16. Note that the measurement of the chlorophyll-a concentration by the first measurement means 14 is the same as step S201 in the first example, and the measurement of the phycocyanin concentration by the second measurement means 16 is the same as step S211 in the second example, so description thereof will be omitted here (step S221).

[0105] Next, in step S222, the control unit 40 determines whether the chlorophyll-a concentration in the unfiltered water to be treated 2 is less than a threshold value. In step S222, the threshold value can be selected, for example, from the range of 0.01 to 5 mg / L, and is preferably in the range of 0.1 to 1 mg / L. If the chlorophyll-a concentration in the unfiltered water to be treated 2 is less than the threshold value (YES), the process proceeds to step S223; if it is equal to or greater than the threshold value (NO), the process proceeds to step S224 (all steps S222).

[0106] In step S223, if the powdered coal injection means 22 is injecting powdered activated carbon into the water to be treated 2, the control unit 40 sends a signal to the powdered coal injection means 22, and based on this signal, the powdered coal injection means 22 stops injecting powdered activated carbon into the water to be treated 2.

[0107] Furthermore, when the control unit 40 is increasing the amount of inorganic flocculant injected from the inorganic flocculant injection means 26 into the coagulation-sedimentation unit 3, it sends a signal to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 stops the increase and reduces the amount of inorganic flocculant injected into the coagulation-sedimentation unit 3. The base injection rate of the inorganic flocculant into the coagulation-sedimentation unit 3 when this increase is stopped is, for example, in the range of 0.1 to 5 mg / L, and preferably in the range of 0.5 to 3 mg / L.

[0108] Furthermore, if the inorganic flocculant injection means 26 is injecting inorganic flocculant into the liquid section 5, a signal is sent to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 stops injecting the inorganic flocculant into the liquid section 5 (step S223).

[0109] In step S224, which follows step S222, the control unit 40 determines whether the phycocyanin concentration in the unfiltered water to be treated 2 is less than the threshold value. In step S224, the threshold value can be selected, for example, from the range of 0.001 to 5 mg / L, preferably from the range of 0.1 to 1 mg / L. If the phycocyanin concentration in the unfiltered water to be treated 2 is less than the threshold value (YES), the process proceeds to step S225, and if it is equal to or greater than the threshold value (NO), the process proceeds to step S228 (all, step S224).

[0110] In step S225, the control unit 40 determines whether the chlorophyll-a concentration in the filtered water to be treated 2' is less than a threshold value. In step S225, the threshold value for the chlorophyll-a concentration in the filtered water to be treated 2' can be selected, for example, from the range of 0.01 to 0.5 mg / L, and is preferably in the range of 0.05 to 0.2 mg / L. If the chlorophyll-a concentration in the filtered water to be treated 2' is less than the threshold value (YES), the process proceeds to step S226; if it is equal to or greater than the threshold value (NO), the process proceeds to step S227 (all steps S225).

[0111] In step S226, if the powdered coal injection means 22 is injecting powdered activated carbon into the water to be treated 2, the control unit 40 sends a signal to the powdered coal injection means 22, and based on this signal, the powdered coal injection means 22 stops injecting powdered activated carbon into the water to be treated 2.

[0112] In addition, the control unit 40 sends a signal to the inorganic coagulant injection means 26, and based on this signal, the inorganic coagulant injection means 26 increases the injection rate of inorganic coagulant from the inorganic coagulant injection means 26 to the coagulation and sedimentation section 3 in accordance with a predetermined relationship between the chlorophyll a concentration in the unfiltered treated water 2 and the optimal injection rate of inorganic coagulant to the coagulation and sedimentation section 3.

[0113] Furthermore, if the inorganic flocculant injection means 26 is injecting inorganic flocculant into the liquid section 5, a signal is sent to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 stops injecting the inorganic flocculant into the liquid section 5 (step S226).

[0114] In step S227, which is the next step from step S225, the control unit 40 sends a signal to the powdered coal injection means 22 if the powdered coal injection means 22 is injecting powdered activated carbon into the water to be treated 2, and based on this signal, the powdered coal injection means 22 stops injecting powdered activated carbon into the water to be treated 2.

[0115] Furthermore, the control unit 40 sends a signal to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 increases the injection rate of the inorganic flocculant from the inorganic flocculant injection means 26 to the coagulation sedimentation unit 3 in accordance with a predetermined relational expression between the chlorophyll-a concentration in the unfiltered water to be treated 2 and the optimal injection rate of the inorganic flocculant to the coagulation sedimentation unit 3. This relational expression is preferably the same as the relational expression in step S226.

[0116] Furthermore, if inorganic flocculant injection means 26 is not injecting inorganic flocculant into liquid portion 5, control unit 40 sends a signal to inorganic flocculant injection means 26, and based on this signal, inorganic flocculant injection means 26 starts injecting inorganic flocculant into liquid portion 5. The injection rate of inorganic flocculant into liquid portion 5 is, for example, in the range of 0.1 to 5 mg / L, and preferably in the range of 0.5 to 3 mg / L. Also, if inorganic flocculant injection means 26 is injecting inorganic flocculant into liquid portion 5, control unit 40 does not send any particular signal, and inorganic flocculant injection means 26 continues injecting inorganic flocculant into liquid portion 5 (step S227).

[0117] In step S228, which follows step S224, the control unit 40 determines whether the chlorophyll-a concentration in the filtered water to be treated 2' is less than a threshold value. In step S228, the threshold value for the chlorophyll-a concentration in the filtered water to be treated 2' is preferably the same value as in step S225. If the chlorophyll-a concentration in the filtered water to be treated 2' is less than the threshold value (YES), the control unit 40 proceeds to step S229; if the chlorophyll-a concentration is equal to or greater than the threshold value (NO), the control unit 40 proceeds to step S230 (step S228).

[0118] In step S229, the control unit 40 sends a signal to the powdered coal injection means 22, and based on this signal, the powdered coal injection means 22 injects powdered activated carbon from the powdered coal injection means 22 into the coagulation and sedimentation unit 3 in accordance with a predetermined relationship between the phycocyanin concentration in the unfiltered water to be treated 2 and the optimal injection rate of powdered activated carbon into the water to be treated 2. This relationship has already been explained in step S215 of the second example, so its explanation will be omitted here.

[0119] Furthermore, the control unit 40 sends a signal to the inorganic coagulant injection means 26, and based on this signal, the inorganic coagulant injection means 26 increases the injection rate of the inorganic coagulant from the inorganic coagulant injection means 26 to the coagulation sedimentation unit 3 in accordance with a predetermined relational expression between the chlorophyll-a concentration in the unfiltered water to be treated 2 and the optimal injection rate of the inorganic coagulant to the coagulation sedimentation unit 3. Note that the inorganic coagulant injection rate in step S229 is greater than the inorganic coagulant injection rate in step S226, and therefore the relational expression here can be a relational expression obtained by adding or multiplying a predetermined coefficient to the relational expression in step S226.

[0120] Furthermore, when the inorganic flocculant injection means 26 is injecting inorganic flocculant into the liquid section 5, the control unit 40 sends a signal to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 stops injecting the inorganic flocculant into the liquid section 5 (this concludes step S229).

[0121] In step S230, which follows step S228, the control unit 40 determines whether the phycocyanin concentration in the filtered water 2' is below a threshold. The phycocyanin concentration in the filtered water 2' is an indicator of the algae concentration of cyanobacteria (picoplankton) in the water. In step S230, the threshold value for the phycocyanin concentration in the filtered water 2' can be selected, for example, from a range of 0.01 to 0.5 mg / L, preferably from a range of 0.05 to 0.2 mg / L. If the phycocyanin concentration in the filtered water 2' is below the threshold (YES), the process proceeds to step S231. If the phycocyanin concentration is equal to or greater than the threshold (NO), the process proceeds to step S232 (all steps S230).

[0122] In step S231, the control unit 40 sends a signal to the powdered coal injection means 22, and based on this signal, the powdered coal injection means 22 injects powdered activated carbon from the powdered coal injection means 22 into the coagulation and sedimentation unit 3 in accordance with a predetermined relationship between the phycocyanin concentration in the unfiltered water to be treated 2 and the optimal injection rate of powdered activated carbon into the water to be treated 2. This relationship is preferably the same as the relationship in step S229.

[0123] Furthermore, the control unit 40 sends a signal to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 increases the injection rate of the inorganic flocculant from the inorganic flocculant injection means 26 to the coagulation sedimentation unit 3 in accordance with a predetermined relational expression between the chlorophyll-a concentration in the unfiltered water to be treated 2 and the optimal injection rate of the inorganic flocculant to the coagulation sedimentation unit 3. This relational expression is preferably the same as the relational expression in step S226.

[0124] Furthermore, if inorganic flocculant injection means 26 is not injecting inorganic flocculant into liquid portion 5, control unit 40 sends a signal to inorganic flocculant injection means 26, and based on this signal, inorganic flocculant injection means 26 starts injecting inorganic flocculant into liquid portion 5. The injection rate of inorganic flocculant into liquid portion 5 is, for example, in the range of 0.1 to 5 mg / L, and preferably in the range of 0.5 to 3 mg / L. Also, if inorganic flocculant injection means 26 is injecting inorganic flocculant into liquid portion 5, inorganic flocculant injection means 26 continues injecting inorganic flocculant into liquid portion 5 as is, but the injection rate range is in the above range (step S231).

[0125] In step S232, which follows step S230, the control unit 40 sends a signal to the powdered coal injection means 22, and based on this signal, the powdered coal injection means 22 increases the injection rate of powdered activated carbon from the powdered coal injection means 22 to the coagulation and sedimentation unit 3 in accordance with a predetermined relationship between the phycocyanin concentration in the unfiltered water to be treated 2 and the optimal injection rate of powdered activated carbon to the water to be treated 2. This relationship is preferably the same as the relationship in step S231.

[0126] Furthermore, the control unit 40 sends a signal to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 increases the injection rate of the inorganic flocculant from the inorganic flocculant injection means 26 to the coagulation sedimentation unit 3 in accordance with a predetermined relational expression between the chlorophyll-a concentration in the unfiltered water to be treated 2 and the optimal injection rate of the inorganic flocculant to the coagulation sedimentation unit 3. This relational expression is preferably the same as the relational expression in step S226.

[0127] Furthermore, if inorganic flocculant injection means 26 is not injecting inorganic flocculant into liquid portion 5, control unit 40 sends a signal to inorganic flocculant injection means 26, and based on this signal, inorganic flocculant injection means 26 starts injecting inorganic flocculant into liquid portion 5. The injection rate of inorganic flocculant into liquid portion 5 is higher than the injection rate of inorganic flocculant into liquid portion 5 in step S231, and is, for example, in the range of 0.5 to 8 mg / L, preferably in the range of 1 to 5 mg / L. Also, if inorganic flocculant injection means 26 is injecting inorganic flocculant into liquid portion 5, inorganic flocculant injection means 26 continues injecting inorganic flocculant into liquid portion 5 as is, but the injection amount range is in the above range (above, step S232).

[0128] The control by the control unit 40 in this example illustrates control when the total algal cell concentration, cyanobacterial cell concentration, total algal picoplankton concentration, and cyanobacterial picoplankton concentration are problematic. In this example, when the total algal cell concentration increases, the amount of inorganic flocculant injected into the coagulation and settling unit 3 is increased to address poor coagulation. When the cyanobacterial cell concentration increases, powdered activated carbon is injected to address unpleasant odors and tastes. Furthermore, when the total algal picoplankton concentration increases, the amount of inorganic flocculant injected into the liquid unit 5 is increased to remove all algal picoplankton in the filtration unit 6, addressing turbidity leakage in the filtered water. Furthermore, when the cyanobacterial picoplankton concentration increases in addition to the total algal picoplankton concentration, the amount of inorganic flocculant injected into the liquid unit 5 is further increased to address turbidity leakage in the filtered water.

[0129] (Fourth Example of Control by Control Unit 40 of Chemical Injection Device 10 of the Present Invention) FIG. 5 is a flowchart illustrating a fourth example of control by the control unit 40 of the chemical injection device 10 of the present invention.

[0130] In this example, both the first measuring means 14 and the second measuring means 16 are used. Also, as the chemical injection means 20, inorganic coagulant injection means 26 to the coagulation settling section 3, inorganic coagulant injection means 26 to the liquid section 5, powdered coal injection means 22 to the water to be treated 2, and sodium hypochlorite (NaClO) injection means 24 to the coagulation settling section 3 are used.

[0131] First, in step S241, the first measuring means 14 measures the chlorophyll-a concentrations of the unfiltered water to be treated 2 and the water to be treated 2' after filtration by the filter 12, and the second measuring means 16 measures the phycocyanin concentrations of the unfiltered water to be treated 2 and the water to be treated 2' after filtration by the filter 12. For details, please refer to step S221, etc., and the description thereof will be omitted here (step S241).

[0132] Next, in step S242, the control unit 40 determines whether the chlorophyll-a concentration in the unfiltered water to be treated 2 is less than a threshold value. In step S242, the threshold value can be selected, for example, from the range of 0.01 to 5 mg / L, and is preferably in the range of 0.1 to 1 mg / L. If the chlorophyll-a concentration in the unfiltered water to be treated 2 is less than the threshold value (YES), the process proceeds to step S243; if it is equal to or greater than the threshold value (NO), the process proceeds to step S244 (all steps S242).

[0133] In step S243, if the powdered coal injection means 22 is injecting powdered activated carbon into the water to be treated 2, the control unit 40 sends a signal to the powdered coal injection means 22, and based on this signal, the powdered coal injection means 22 stops injecting powdered activated carbon into the water to be treated 2.

[0134] Furthermore, when the amount of inorganic flocculant injected from the inorganic flocculant injection means 26 into the coagulation-sedimentation section 3 is being increased, the control section 40 sends a signal to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 stops the increase and reduces the amount of inorganic flocculant injected into the coagulation-sedimentation section 3. The base injection rate of inorganic flocculant into the coagulation-sedimentation section 3 when this increase is stopped is, for example, in the range of 10 to 50 mg / L, and preferably in the range of 15 to 35 mg / L.

[0135] Furthermore, if the inorganic flocculant injection means 26 is injecting inorganic flocculant into the liquid section 5, a signal is sent to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 stops injecting the inorganic flocculant into the liquid section 5 (step S243).

[0136] In step S244, which follows step S242, the control unit 40 determines whether the phycocyanin concentration in the unfiltered water to be treated 2 is less than the threshold value. In step S244, the threshold value can be selected, for example, from the range of 0.01 to 5 mg / L, preferably from the range of 0.1 to 1 mg / L. If the phycocyanin concentration in the unfiltered water to be treated 2 is less than the threshold value (YES), the process proceeds to step S245, and if it is equal to or greater than the threshold value (NO), the process proceeds to step S248 (all, step S244).

[0137] In step S245, the control unit 40 determines whether the chlorophyll-a concentration in the filtered water to be treated 2' is less than a threshold value. In step S245, the threshold value for the chlorophyll-a concentration in the filtered water to be treated 2' can be selected, for example, from the range of 0.01 to 0.5 mg / L, and is preferably in the range of 0.05 to 0.2 mg / L. If the chlorophyll-a concentration in the filtered water to be treated 2' is less than the threshold value (YES), the process proceeds to step S246; if it is equal to or greater than the threshold value (NO), the process proceeds to step S247 (all steps S245).

[0138] In step S246, the control unit 40 sends a signal to the sodium hypochlorite (NaClO) injection means 24 to the coagulation and sedimentation unit 3, and based on this signal, the sodium hypochlorite (NaClO) injection means 24 injects sodium hypochlorite (NaClO) from sodium hypochlorite (NaClO) into the coagulation and sedimentation unit 3 in accordance with a predetermined relationship between the chlorophyll-a concentration in the unfiltered treated water 2 and the optimal injection rate of sodium hypochlorite (NaClO) to the coagulation and sedimentation unit 3.

[0139] In addition, the control unit 40 sends a signal to the powdered coal injection means 22, and based on this signal, the powdered coal injection means 22 injects powdered activated carbon from the powdered coal injection means 22 into the coagulation and sedimentation unit 3 in accordance with a relationship between a predetermined chlorophyll a concentration in the unfiltered treated water 2 and the optimal injection rate of powdered activated carbon into the treated water 2.

[0140] Furthermore, the control unit 40 sends a signal to the inorganic coagulant injection means 26, and based on this signal, the inorganic coagulant injection means 26 increases the injection rate of inorganic coagulant from the inorganic coagulant injection means 26 to the coagulation and sedimentation section 3 in accordance with a predetermined relationship between the chlorophyll a concentration in the unfiltered treated water 2 and the optimal injection rate of inorganic coagulant to the coagulation and sedimentation section 3.

[0141] Furthermore, if the inorganic flocculant injection means 26 is injecting inorganic flocculant into the liquid section 5, a signal is sent to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 stops injecting the inorganic flocculant into the liquid section 5 (step S246).

[0142] In step S247, which is the next step from step S245, the control unit 40 sends a signal to the sodium hypochlorite (NaClO) injection means 24 to the coagulation and sedimentation unit 3, and based on this signal, the sodium hypochlorite (NaClO) injection means 24 injects sodium hypochlorite (NaClO) from sodium hypochlorite (NaClO) into the coagulation and sedimentation unit 3 in accordance with a predetermined relationship between the chlorophyll-a concentration in the unfiltered treated water 2 and the optimal injection rate of sodium hypochlorite (NaClO) to the coagulation and sedimentation unit 3.

[0143] Furthermore, the control unit 40 sends a signal to the powdered coal injection means 22, and based on this signal, the powdered coal injection means 22 injects powdered activated carbon from the powdered coal injection means 22 into the coagulation and sedimentation unit 3 in accordance with a predetermined relational expression between the chlorophyll-a concentration in the unfiltered water to be treated 2 and the optimal injection rate of powdered activated carbon into the water to be treated 2. It is preferable to use the same relational expression as in step S246.

[0144] Furthermore, the control unit 40 sends a signal to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 increases the injection rate of the inorganic flocculant from the inorganic flocculant injection means 26 to the coagulation sedimentation unit 3 in accordance with a predetermined relational expression between the chlorophyll-a concentration in the unfiltered water to be treated 2 and the optimal injection rate of the inorganic flocculant to the coagulation sedimentation unit 3. It is preferable to use the same relational expression as in step S246.

[0145] Furthermore, if inorganic flocculant injection means 26 is not injecting inorganic flocculant into liquid section 5, control section 40 sends a signal to inorganic flocculant injection means 26, and based on this signal, inorganic flocculant injection means 26 starts injecting inorganic flocculant into liquid section 5. The injection rate of inorganic flocculant into liquid section 5 is, for example, in the range of 0.1 to 5 mg / L, preferably in the range of 0.5 to 3 mg / L. Furthermore, if inorganic flocculant injection means 26 is injecting inorganic flocculant into liquid section 5, control section 40 does not send any particular signal, and inorganic flocculant injection means 26 continues injecting inorganic flocculant into liquid section 5 (step S247).

[0146] In step S248, which follows step S244, the control unit 40 determines whether the chlorophyll-a concentration in the filtered water to be treated 2' is less than a threshold value. In step S248, the threshold value for the chlorophyll-a concentration in the filtered water to be treated 2' is preferably the same value as in step S245. If the chlorophyll-a concentration in the filtered water to be treated 2' is less than the threshold value (YES), the control unit 40 proceeds to step S249; if the chlorophyll-a concentration is equal to or greater than the threshold value (NO), the control unit 40 proceeds to step S250 (step S248).

[0147] In step S249, if the sodium hypochlorite (NaClO) injection means 24 is injecting sodium hypochlorite (NaClO) into the coagulation and sedimentation unit 3, the control unit 40 sends a signal to the sodium hypochlorite (NaClO) injection means 24, and based on this signal, the sodium hypochlorite (NaClO) injection means 24 stops injecting sodium hypochlorite (NaClO) into the coagulation and sedimentation unit 3.

[0148] Furthermore, the control unit 40 sends a signal to the pulverized coal injection means 22, and based on this signal, the pulverized coal injection means 22 injects powdered activated carbon from the pulverized coal injection means 22 into the coagulation and sedimentation unit 3 in accordance with a predetermined relational expression between the chlorophyll-a concentration in the unfiltered water to be treated 2 and the optimal injection rate of powdered activated carbon into the water to be treated 2. Note that the pulverized coal injection rate in step S249 is greater than the pulverized coal injection rate in step S247, and therefore the relational expression here can be an expression obtained by adding or multiplying a predetermined coefficient to the relational expression in step S247.

[0149] Furthermore, the control unit 40 sends a signal to the inorganic coagulant injection means 26, and based on this signal, the inorganic coagulant injection means 26 increases the injection rate of the inorganic coagulant from the inorganic coagulant injection means 26 to the coagulation sedimentation unit 3 in accordance with a predetermined relational expression between the chlorophyll-a concentration in the unfiltered treated water 2 and the optimal injection rate of the inorganic coagulant to the coagulation sedimentation unit 3. Note that the inorganic coagulant injection rate in step S249 is greater than the inorganic coagulant injection rate in step S247, and therefore the relational expression here can be a relational expression obtained by adding or multiplying a predetermined coefficient to the relational expression in step S247.

[0150] Furthermore, if the inorganic flocculant injection means 26 is injecting inorganic flocculant into the liquid section 5, a signal is sent to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 stops injecting the inorganic flocculant into the liquid section 5 (step S249).

[0151] In step S250, which follows step S248, the control unit 40 determines whether the phycocyanin concentration in the filtered water to be treated 2' is less than a threshold value. In step S250, the threshold value for the phycocyanin concentration in the filtered water to be treated 2' can be selected, for example, from the range of 0.01 to 5 mg / L, and is preferably in the range of 0.1 to 1 mg / L. If the phycocyanin concentration in the filtered water to be treated 2' is less than the threshold value (YES), the control unit 40 proceeds to step S251. If the phycocyanin concentration is equal to or greater than the threshold value (NO), the control unit 40 proceeds to step S252 (all steps S250).

[0152] In step S251, if the sodium hypochlorite (NaClO) injection means 24 is injecting sodium hypochlorite (NaClO) into the coagulation and sedimentation unit 3, the control unit 40 sends a signal to the sodium hypochlorite (NaClO) injection means 24, and based on this signal, the sodium hypochlorite (NaClO) injection means 24 stops injecting sodium hypochlorite (NaClO) into the coagulation and sedimentation unit 3.

[0153] Furthermore, the control unit 40 sends a signal to the powdered coal injection means 22, and based on this signal, the powdered coal injection means 22 injects powdered activated carbon from the powdered coal injection means 22 into the coagulation and sedimentation unit 3 in accordance with a predetermined relationship between the chlorophyll-a concentration in the unfiltered water to be treated 2 and the optimal injection rate of powdered activated carbon into the water to be treated 2. Note that the powdered coal injection rate in step S251 is preferably the same as the powdered coal injection rate in step S249.

[0154] Furthermore, the control unit 40 sends a signal to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 increases the injection rate of the inorganic flocculant from the inorganic flocculant injection means 26 to the coagulation sedimentation unit 3 in accordance with a predetermined relational expression between the chlorophyll-a concentration in the unfiltered treated water 2 and the optimal injection rate of the inorganic flocculant to the coagulation sedimentation unit 3. Note that the inorganic flocculant injection rate in step S251 is preferably the same as the inorganic flocculant injection rate in step S249.

[0155] Furthermore, if inorganic flocculant injection means 26 is not injecting inorganic flocculant into liquid portion 5, control unit 40 sends a signal to inorganic flocculant injection means 26, and based on this signal, inorganic flocculant injection means 26 starts injecting inorganic flocculant into liquid portion 5. The injection rate of inorganic flocculant into liquid portion 5 is, for example, in the range of 0.1 to 5 mg / L, and preferably in the range of 0.5 to 3 mg / L. Also, if inorganic flocculant injection means 26 is injecting inorganic flocculant into liquid portion 5, inorganic flocculant injection means 26 continues injecting inorganic flocculant into liquid portion 5 as is, but the injection amount range is within the above range (step S251).

[0156] In step S252, which is the next step from step S250, if the sodium hypochlorite (NaClO) injection means 24 is injecting sodium hypochlorite (NaClO) into the coagulation and sedimentation unit 3, the control unit 40 sends a signal to the sodium hypochlorite (NaClO) injection means 24, and based on this signal, the sodium hypochlorite (NaClO) injection means 24 stops injecting sodium hypochlorite (NaClO) into the coagulation and sedimentation unit 3.

[0157] Furthermore, the control unit 40 sends a signal to the powdered coal injection means 22, and based on this signal, the powdered coal injection means 22 injects powdered activated carbon from the powdered coal injection means 22 into the coagulation and sedimentation unit 3 in accordance with a predetermined relationship between the chlorophyll-a concentration in the unfiltered water to be treated 2 and the optimal injection rate of powdered activated carbon into the water to be treated 2. Note that the powdered coal injection rate in step S252 is preferably the same as the powdered coal injection rate in step S249.

[0158] Furthermore, the control unit 40 sends a signal to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 increases the injection rate of the inorganic flocculant from the inorganic flocculant injection means 26 to the coagulation sedimentation unit 3 in accordance with a predetermined relational expression between the chlorophyll-a concentration in the unfiltered treated water 2 and the optimal injection rate of the inorganic flocculant to the coagulation sedimentation unit 3. Note that the inorganic flocculant injection rate in step S252 is preferably the same as the inorganic flocculant injection rate in step S249.

[0159] Furthermore, if inorganic flocculant injection means 26 is not injecting inorganic flocculant into liquid portion 5, control unit 40 sends a signal to inorganic flocculant injection means 26, and based on this signal, inorganic flocculant injection means 26 starts injecting inorganic flocculant into liquid portion 5. The injection rate of inorganic flocculant into liquid portion 5 is higher than the injection rate of inorganic flocculant in step S251, and is, for example, in the range of 0.5 to 8 mg / L, preferably in the range of 1 to 5 mg / L. Also, if inorganic flocculant injection means 26 is injecting inorganic flocculant into liquid portion 5, inorganic flocculant injection means 26 continues injecting inorganic flocculant into liquid portion 5 as is, but the injection amount range is within the above range (above, step S252).

[0160] The control by the control unit 40 in this example illustrates control when the total algal cell concentration, the cyanobacterial cell concentration, the total algal picoplankton concentration, and the cyanobacterial picoplankton concentration are problematic. In this example, when the total algal cell concentration increases, poor coagulation is addressed by increasing the amount of inorganic coagulant injected into the coagulation-sedimentation unit 3, injecting powdered activated carbon into the water being treated 2, and injecting sodium hypochlorite (also called pre-chlorination) into the coagulation-sedimentation unit 3. Furthermore, when the cyanobacterial cell concentration increases, the pre-chlorination is stopped and the amount of powdered activated carbon injected into the water being treated 2 is further increased to address the occurrence of unpleasant odors and tastes. Furthermore, when the total algal picoplankton concentration and the cyanobacterial picoplankton concentration increase, the amount of inorganic coagulant injected into the liquid section 5 is gradually increased to coagulate the picoplankton, which are then removed in the filtration section 6 to address turbidity leakage in the filtered water.

[0161] (Fifth Example of Control by Control Unit 40 of Chemical Injection Device 10 of the Present Invention) FIG. 6 is a flowchart illustrating a fifth example of control by the control unit 40 of the chemical injection device 10 of the present invention.

[0162] In this example, both the first measuring means 14 and the second measuring means 16 are used. Also, as the chemical injection means 20, an inorganic flocculant injection means 26 to the coagulation-sedimentation section 3 and a polymer flocculant injection means 28 to the coagulation-sedimentation section 3 are used.

[0163] First, in step S261, the first measurement means 14 measures the chlorophyll-a concentration of the unfiltered water to be treated 2, and the second measurement means 16 measures the phycocyanin concentration of the unfiltered water to be treated 2. For details, please refer to step S221, etc., and the description thereof will be omitted here (step S261).

[0164] Next, in step S262, the control unit 40 determines whether the chlorophyll-a concentration in the unfiltered water to be treated 2 is less than a threshold value. In step S262, the threshold value can be selected, for example, from the range of 0.01 to 5 mg / L, and is preferably in the range of 0.1 to 1 mg / L. If the chlorophyll-a concentration in the unfiltered water to be treated 2 is less than the threshold value (YES), the process proceeds to step S263; if it is equal to or greater than the threshold value (NO), the process proceeds to step S264 (step S262).

[0165] In step S263, if the amount of inorganic flocculant injected from the inorganic flocculant injection means 26 to the coagulation-sedimentation section 3 is being increased, the control section 40 sends a signal to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 stops the increase and reduces the amount of inorganic flocculant injected into the coagulation-sedimentation section 3. The base injection rate of inorganic flocculant to the coagulation-sedimentation section 3 when this increase is stopped is, for example, in the range of 10 to 50 mg / L, and preferably in the range of 15 to 35 mg / L.

[0166] In addition, when the polymer flocculant injection means 28 is injecting polymer flocculant into the coagulation and sedimentation section 3, the control unit 40 sends a signal to the polymer flocculant injection means 28, and based on this signal, the polymer flocculant injection means 28 stops injecting polymer flocculant into the coagulation and sedimentation section 3 (step S263).

[0167] In step S264, which follows step S262, the control unit 40 determines whether the phycocyanin concentration in the unfiltered water to be treated 2 is less than the threshold value. In step S264, the threshold value can be selected, for example, from the range of 0.01 to 5 mg / L, preferably from the range of 0.1 to 1 mg / L. If the phycocyanin concentration in the unfiltered water to be treated 2 is less than the threshold value (YES), the process proceeds to step S265, and if it is equal to or greater than the threshold value (NO), the process proceeds to step S266 (all, step S264).

[0168] In step S265, the control unit 40 sends a signal to the inorganic coagulant injection means 26, and based on this signal, the inorganic coagulant injection means 26 increases the injection rate of inorganic coagulant from the inorganic coagulant injection means 26 to the coagulation and sedimentation section 3 from the base injection rate in accordance with a predetermined relationship between the chlorophyll a concentration in the unfiltered treated water 2 and the optimal injection rate of inorganic coagulant to the coagulation and sedimentation section 3.

[0169] Furthermore, the control unit 40 sends a signal to the polymer flocculant injection means 28, and based on this signal, the polymer flocculant injection means 28 injects polymer flocculant from the polymer flocculant injection means 28 into the coagulation and sedimentation section 3 in accordance with a relationship between a predetermined chlorophyll a concentration in the unfiltered treated water 2 and the optimal injection rate of polymer flocculant into the coagulation and sedimentation section 3.

[0170] As already mentioned, the chlorophyll a concentration is correlated with the algae body concentration of algae in general, and there is also a correlation between the algae body concentration of algae in general and the amount of polymer flocculant required. Therefore, by obtaining a relational equation between the chlorophyll a concentration and the polymer flocculant injection rate into the coagulation and sedimentation section 3 in advance, and substituting the chlorophyll a concentration value in the unfiltered treated water 2 measured and determined by the first measurement means 14 into the above relational equation, the optimal injection rate of polymer flocculant into the coagulation and sedimentation section 3 can be calculated (step S265).

[0171] In step S266, which is the next step from step S264, the control unit 40 sends a signal to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 increases the injection rate of the inorganic flocculant from the inorganic flocculant injection means 26 to the coagulation-sedimentation unit 3 from the base injection rate. Note that the inorganic flocculant injection rate in step 266 is greater than the inorganic flocculant injection rate in step S265, and therefore the relational expression here can be a relational expression obtained by adding or multiplying a predetermined coefficient to the relational expression in step S265.

[0172] Furthermore, the control unit 40 sends a signal to the polymer flocculant injection means 28, and based on this signal, the polymer flocculant injection means 28 injects polymer flocculant into the coagulation and sedimentation section 3 from the polymer flocculant injection means 28 in accordance with a relational expression between the chlorophyll-a concentration in the unfiltered water to be treated 2, which has been determined in advance, and the optimal injection rate of polymer flocculant into the coagulation and sedimentation section 3. It is preferable to use the same relational expression as that used in step S265 (step S266).

[0173] The control by the control unit 40 in this example shows control in a case where the picoplankton concentration is not an issue, but the total algae cell concentration and the cyanobacteria cell concentration are issues. In this example, when the total algae cell concentration increases, poor coagulation is addressed by increasing the amount of inorganic coagulant injected into the coagulation and sedimentation unit 3 and injecting a polymer coagulant into the coagulation and sedimentation unit 3. Furthermore, when the cyanobacteria cell concentration increases, the generation of unpleasant odors and tastes is addressed by further increasing the amount of inorganic coagulant injected into the coagulation and sedimentation unit 3.

[0174] The above describes a chemical injection device having a control unit that controls the injection rate of the chemical injected by the chemical injection means based on at least two measured values ​​of the photosynthetic pigment concentrations measurable by the first measurement means and the second measurement means. However, the invention of a chemical injection device 50 in which the photosynthetic pigment measurement means is only a phycocyanin measurement means and the control unit controls the injection rate of the chemical injected by the chemical injection means based only on the measured value of the phycocyanin pigment concentration will be described below with reference to FIG. 7.

[0175] Figure 7 is a schematic diagram for explaining a chemical injection device 50 of the present invention. In Figure 7, the same components as those in Figure 1 are given the same reference numerals, and their description will be omitted here.

[0176] As shown in the figure, a chemical injection device 50 of the present invention is also a chemical injection device for injecting chemicals into a water purification system 1 that separates water 2 to be treated into solid and liquid to obtain treated water.

[0177] The chemical injection device 50 of the present invention has a phycocyanin measurement means 52, a chemical injection means 20, and a control unit 42.

[0178] The phycocyanin measurement means 52 is a measurement means capable of measuring the pigment concentration of phycocyanin in the unfiltered water 2. Examples of the phycocyanin measurement means 52 include a means for measurement by fluorometry and absorptiometry, but the former fluorometry is preferred. In this case, a known spectrofluorometer can be used as the phycocyanin measurement means 52. The phycocyanin measurement means 52 is controlled by the control unit 42, which will be described later.

[0179] Chemical injection means 20 is a means for injecting chemicals in water purification system 1, and can be any of the chemical injection means exemplified in the description of chemical injection device 10 in Figure 1. Chemical injection device 50 of the present invention employs, as chemical injection means 20, powdered coal injection means 22 into water to be treated 2, sodium hypochlorite (NaClO) injection means 24 into coagulation-sedimentation section 3, and inorganic coagulant injection means 26 into coagulation-sedimentation section 3.

[0180] The control unit 42 controls the injection rate of the chemical injected by the chemical injection means 20 based only on the measured value of the phycocyanin pigment concentration of the unfiltered treated water 2 measured by the phycocyanin measurement means 52. Like the control unit 40, the control unit 42 is also a computer.

[0181] The control by the control unit 42 will be described below with reference to FIG.

[0182] (First Example of Control by Control Unit 42 of Chemical Injection Device 50 of the Present Invention) FIG. 8 is a flowchart illustrating a first example of control by control unit 42 of chemical injection device 50 of the present invention.

[0183] First, in step S271, the phycocyanin measurement means 52 measures the phycocyanin concentration of the unfiltered water to be treated 2. For detailed descriptions, refer to step S221 and the like, and the description thereof will be omitted here (step S271).

[0184] Next, in step S272, the control unit 42 determines whether the phycocyanin concentration in the unfiltered water to be treated 2 is less than a threshold value. In step S272, the threshold value can be selected, for example, from the range of 0.01 to 5 mg / L, and is preferably in the range of 0.1 to 1 mg / L. If the phycocyanin concentration in the unfiltered water to be treated 2 is less than the threshold value (YES), the process proceeds to step S273; if it is equal to or greater than the threshold value (NO), the process proceeds to step S274 (all, step S272).

[0185] In step S273, if the sodium hypochlorite (NaClO) injecting means 24 is not injecting sodium hypochlorite (NaClO) into the coagulating and settling unit 3, the control unit 42 sends a signal to the sodium hypochlorite (NaClO) injecting means 24, and based on this signal, the sodium hypochlorite (NaClO) injecting means 24 starts injecting sodium hypochlorite (NaClO) into the coagulating and settling unit 3. The injection rate of sodium hypochlorite (NaClO) into the coagulating and settling unit 3 is, for example, in the range of 0.1 to 5 mg / L, and preferably in the range of 0.2 to 2.0 mg / L. Furthermore, if the sodium hypochlorite (NaClO) injecting means 24 is injecting sodium hypochlorite (NaClO) into the coagulating and settling unit 3, the control unit 42 does not send any particular signal, and the sodium hypochlorite (NaClO) injecting means 24 continues injecting sodium hypochlorite (NaClO) into the coagulating and settling unit 3.

[0186] In addition, when the powdered coal injection means 22 is injecting powdered activated carbon into the water to be treated 2, the control unit 42 sends a signal to the powdered coal injection means 22, and based on this signal, the powdered coal injection means 22 stops injecting powdered activated carbon into the water to be treated 2.

[0187] Furthermore, when the control unit 42 is increasing the amount of inorganic flocculant injected from the inorganic flocculant injection means 26 into the coagulation-sedimentation unit 3, it sends a signal to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 stops the increase and reduces the amount of inorganic flocculant injected into the coagulation-sedimentation unit 3. Note that the base injection rate of the inorganic flocculant into the coagulation-sedimentation unit 3 when this increase is stopped is, for example, in the range of 10 to 50 mg / L, and preferably in the range of 15 to 35 mg / L (step S273).

[0188] In step S274, which is the next step from step S272, if the sodium hypochlorite (NaClO) injection means 24 is injecting sodium hypochlorite (NaClO) into the coagulation and sedimentation unit 3, the control unit 42 sends a signal to the sodium hypochlorite (NaClO) injection means 24, and based on this signal, the sodium hypochlorite (NaClO) injection means 24 stops injecting sodium hypochlorite (NaClO) into the coagulation and sedimentation unit 3.

[0189] In addition, the control unit 42 sends a signal to the powdered coal injection means 22, and based on this signal, the powdered coal injection means 22 injects powdered activated carbon from the powdered coal injection means 22 into the coagulation and sedimentation unit 3 in accordance with a predetermined relationship between the phycocyanin concentration in the unfiltered water to be treated 2 and the optimal injection rate of powdered activated carbon into the water to be treated 2.

[0190] Furthermore, the control unit 42 sends a signal to the inorganic flocculant injection means 26, and based on this signal, the inorganic flocculant injection means 26 increases the injection rate of the inorganic flocculant from the inorganic flocculant injection means 26 to the coagulation-sedimentation unit 3 from the base injection rate in accordance with a predetermined relational expression between the phycocyanin concentration in the unfiltered water 2 and the optimal injection rate of the inorganic flocculant to the coagulation-sedimentation unit 3 (step S274).

[0191] The above control by the control unit 42 in this example shows control in a case where the algal body concentration of all algae and the picoplankton concentration are not a problem, but the algal body concentration of cyanobacteria is a problem.

[0192] It has been known in the past that, because cyanobacteria have a large impact on water purification problems, chemical injections should be adjusted with a focus on cyanobacteria among other algae, but in Non-Patent Document 3, detection of cyanobacteria was performed using a microscope, which was time-consuming and labor-intensive, as it was not possible to detect cyanobacteria on-site. There was also the ambiguity of visual inspection.

[0193] According to the chemical injection device 50 of this example, by measuring the photosynthetic pigment phycocyanin as an indicator of cyanobacteria using a phycocyanin measurement means, it is possible to monitor cyanobacteria in the water to be treated (raw water) on-site and in real time, and reflect this in chemical injection. In other words, the chemical injection device of the present invention can quickly measure the amount of cyanobacteria that particularly significantly cause water purification problems on-site, without being limited to the total amount of algae. Therefore, when the overall amount of algae is not an issue, the amount of chemical injection can be controlled more efficiently and effectively than if chemical injection were controlled based on the overall amount of algae.

[0194] Specifically, in this example, when the concentration of cyanobacteria cells becomes high, the injection of sodium hypochlorite (NaClO) into the coagulation and sedimentation unit 3 is stopped, powdered activated carbon is injected into the water to be treated 2, and an inorganic coagulant is injected into the coagulation and sedimentation unit 3. This prevents off-odor and taste substances present in the cyanobacteria cells from flowing out of the cells, and removes them by coagulation and sedimentation. Note that any off-odor and taste substances that do flow out are controlled so that they are adsorbed onto the powdered activated carbon and removed by coagulation and sedimentation.

[0195] To facilitate understanding of the invention, the chemical injection device 50 of the present invention is specified as having only a configuration including a phycocyanin measurement means, but it may also have multiple photosynthetic pigment concentration measurement means, as in the chemical injection device 10. For example, an embodiment of the chemical injection device of the present invention also includes a case in which only the phycocyanin concentration of unfiltered treated water is measured using the chemical injection device 10, and the injection rate of the chemical injected by the chemical injection means is controlled by the control unit based only on the measured value of the phycocyanin pigment concentration of this unfiltered treated water.

[0196] <Chemical injection method> The chemical injection method of the present invention will be described below using the chemical injection device 10 of Figure 1 as an example. Figure 9 is a flowchart illustrating the chemical injection method of the present invention.

[0197] The chemical injection method of the present invention is a chemical injection method for injecting chemicals into a water purification system 1 in which treated water 2 is subjected to coagulation and sedimentation treatment in a coagulation and sedimentation section 3 to separate it into a sediment 4 and a liquid part 5, and the resulting liquid part 5 is filtered in a filtration section 6 to obtain treated water 7.

[0198] The water purification system 1 has already been explained in the section entitled "Chemical Injection Device" above, and so its explanation will be omitted here.

[0199] As shown in the figure, the chemical injection method of the present invention includes an optional filtering step (S100), a measuring step (S110), a chemical injection rate determining step (S120), and a chemical injection step (S130).

[0200] [Optional filtration step (S100)] In this step, the water to be treated 2 is optionally filtered. Filtration can be performed using a filter 12. The filter 12 has also been explained above in the section on chemical dosing device, and its description will be omitted here. Although this step is optional, for example, if only the first photosynthetic pigment concentration of the unfiltered water to be treated 2 and the second photosynthetic pigment concentration of the unfiltered water to be treated 2 are measured in the measurement step (S110) described below, and only these measured values ​​are used in the subsequent steps, then the filter 12 is not necessary.

[0201] The unfiltered water to be treated 2 and optionally the water to be treated 2' after filtration by the filter 12 are subjected to the next measurement step (S110) (this concludes the measurement step (S100)).

[0202] [Measurement process (S110)] In this process, at least two types of photosynthetic pigment concentrations are measured: the first photosynthetic pigment concentration in the filtered treated water 2', the first photosynthetic pigment concentration in the unfiltered treated water 2, the second photosynthetic pigment concentration in the filtered treated water 2', and the second photosynthetic pigment concentration in the unfiltered treated water 2.

[0203] The first photosynthetic pigment and the second photosynthetic pigment can be selected from pigments found in photosynthetic organisms, such as chlorophyll, carotenoids, and phycobilins, with the proviso that the second photosynthetic pigment is different from the first photosynthetic pigment.

[0204] The concentration of the first photosynthetic pigment can be measured, for example, by first measurement means 14, and the concentration of the second photosynthetic pigment can be measured, for example, by second measurement means 16. The first measurement means 14 and the second measurement means 16 have already been explained in the section entitled <Chemical Injection Device> above, and therefore will not be described here (this concludes the measurement process (S110)).

[0205] [Chemical injection rate determination step (S120)] In this step, the injection rate of the chemical is determined based on the measured values ​​of the concentrations of at least two types of photosynthetic pigments measured in the measuring step (S110).

[0206] Examples of chemicals to be injected include, but are not limited to, powdered activated carbon, sodium hypochlorite (chlorine), inorganic flocculants, polymer flocculants, and flocculation aids.

[0207] The chemical injection rate may be determined, for example, by adding a predetermined amount or stopping the addition when the photosynthetic pigment concentration (e.g., unfiltered chlorophyll a concentration) measured in the measurement step (S110) exceeds a threshold value, or by substituting the measured photosynthetic pigment concentration value into a predetermined relationship between the photosynthetic pigment concentration and the required amount of chemical to determine the chemical injection amount when the photosynthetic pigment concentration measured in the measurement step (S110) exceeds the threshold value.

[0208] The chemical injection rate can be determined by reference to, for example, the first to fifth examples of control by the control unit 40 of the chemical injection device 10 of the present invention in the above <Chemical Injection Device>. Note that in these first to fifth examples of control by the control unit 40, the chemical injection rate is determined using the control unit 40, but use of the control unit 40 is not essential.

[0209] For example, the combination of chemicals to be injected, the chemical thresholds, the relational expressions to be used, etc. may be compiled into a manual, and the chemical injection rates may be determined manually according to this manual based on the measured values ​​of the concentrations of at least two types of photosynthetic pigments measured in the measurement step (S110). After the chemical injection amounts have been determined, the process proceeds to the chemical injection step (the chemical injection rate determination step (S120)).

[0210] [Chemical injection process (S130)] In this step, the chemical is injected into the water purification system 1 at the injection rate determined in the injection rate determination step (S120).

[0211] Depending on the selected chemical, the destination of the chemical to be injected can be selected from the water to be treated 2, the coagulation and sedimentation section 3, and the liquid section 5, for example.

[0212] As shown in FIG. 1, depending on the selected chemical, for example, powdered coal injection means 22, polymer coagulant injection means 28, inorganic coagulant injection means 26, and sodium hypochlorite (NaClO) injection means 24 can be selected, but are not limited to these.

[0213] If the chemical is in liquid form, the injection means 20 may be configured to include a chemical storage tank, piping connecting the storage tank to the destination of the chemical, a pump installed in the piping, and an on-off valve in the piping. If the chemical is in powder form, such as powdered activated carbon, the injection means may be configured to include a hopper capable of storing the chemical, piping connecting the hopper to the destination of the chemical, and an on-off metering valve installed below the hopper. The specific configuration of the injection means 20 is not limited to this example.

[0214] The injection of chemicals from the injection means 20 may be controlled by the control unit 40, as described above in the <Chemical injection device>, but it is also possible for a person to operate the injection means 20 and inject chemicals into the water purification treatment system 1 according to the amount of chemical to be injected determined in the chemical injection rate determination step (S120).

[0215] According to this method, the type of algae in the water being treated can be quickly determined on the spot using at least two measured values ​​of the first photosynthetic pigment concentration and the second photosynthetic pigment concentration, and the injection of chemicals can be controlled on the spot based on the determined status of the type of algae in the water being treated.

[0216] Furthermore, if a filtration process for filtering the water to be treated is provided, the injection of chemicals can be controlled on-site based on the type and / or size of algae in the water to be treated using at least two of the four measured values: the concentration of the first photosynthetic pigment in the filtered water to be treated, the concentration of the first photosynthetic pigment in the unfiltered water to be treated, the concentration of the second photosynthetic pigment in the filtered water to be treated, and the concentration of the second photosynthetic pigment in the unfiltered water to be treated.

[0217] Therefore, in water purification treatment, the state of algae in the water to be treated can be grasped more quickly and accurately than before, and an appropriate chemical can be selected on the spot and its injection can be controlled.

Claims

1. A chemical injection device for injecting chemicals into a water purification system that separates water to be treated into solid and liquid to obtain treated water, an optional filter for filtering the water to be treated; a first measuring means capable of measuring the concentration of at least one first photosynthetic pigment in the unfiltered water to be treated and the water to be treated after filtration with the filter; a second measuring means capable of measuring the concentration of at least one second photosynthetic pigment in the unfiltered water to be treated and the water to be treated after filtration with the filter; A chemical injection means for injecting chemicals into the water purification system; a control unit that controls the injection rate of the chemical injected by the chemical injection means based on at least two measured values ​​of the photosynthetic pigment concentrations that can be measured by the first measurement means and the second measurement means; and The first measuring means can measure the chlorophyll a pigment concentration of the unfiltered treated water and the chlorophyll a pigment concentration of the treated water after filtration by the filter, and the second measuring means can measure the phycocyanin pigment concentration of the unfiltered treated water and the phycocyanin pigment concentration of the treated water after filtration, The control unit controls the amount of the chemical injected by the chemical injection means based on at least two measured values ​​of the total of four dye concentrations that can be measured by the first measurement means and the second measurement means. A chemical injection device characterized by:

2. The chemical injection device according to claim 1, characterized in that the solid-liquid separation of the water to be treated is carried out by subjecting the water to a coagulation and sedimentation treatment in a coagulation and sedimentation section to separate it into a precipitate and a liquid portion, and then filtering the obtained liquid portion in a filtration section to obtain treated water.

3. The chemical injection device according to claim 2, characterized in that the chemical injection means is one or more selected from the group consisting of powdered coal injection means into the water to be treated, sodium hypochlorite injection means into the coagulation and sedimentation section, sodium hypochlorite injection means into the liquid section, inorganic coagulant injection means into the coagulation and sedimentation section, inorganic coagulant injection means into the liquid section, and polymer coagulant injection means into the coagulation and sedimentation section.

4. 2. The chemical injection device according to claim 1, wherein the pore size of the filter is 1 μm or more and 10 μm or less.

5. 2. The chemical injection device according to claim 1, wherein the first measuring means and the second measuring means detect fluorescence.

6. A chemical injection method for injecting a chemical into a water purification system, in which water to be treated is subjected to coagulation and sedimentation treatment in a coagulation and sedimentation unit to separate it into a sediment and a liquid portion, and the obtained liquid portion is filtered in a filtration unit to obtain treated water, a filtration step of arbitrarily filtering the water to be treated; a measuring step of measuring the concentration of a first photosynthetic pigment in the filtered water to be treated, the concentration of a first photosynthetic pigment in the unfiltered water to be treated, the concentration of a second photosynthetic pigment in the filtered water to be treated, and the concentration of a second photosynthetic pigment in the unfiltered water to be treated; an injection rate determination step of determining an injection rate of a chemical based on the measured values ​​of at least two types of photosynthetic pigment concentrations among the measured values ​​measured in the measurement step; an injection step of injecting a chemical into the water purification system at the injection rate determined in the injection rate determination step; and The first photosynthetic pigment concentration is a pigment concentration of chlorophyll a, and the second photosynthetic pigment concentration is a pigment concentration of phycocyanin. A chemical injection method characterized by:

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