Water quality assessment system

Abstract

The purpose of the present invention is to provide a water quality assessment system with which it is possible to assess water quality with a simple configuration overall.　The aforementioned problem is solved by a water quality assessment system comprising a chlorine supply means, a chlorine concentration measurement means, and an assessment means, the chlorine supply means being capable of supplying chlorine to an assessment target, the chlorine concentration measurement means being capable of measuring the free chlorine concentration of the assessment target to which the chlorine is supplied by the chlorine supply means, and the assessment means is capable of assessing the water quality of the assessment target by collating the free chlorine concentration measured by the chlorine concentration measurement means with an index chlorine concentration.

Description

Water quality determination system

[0001] The present invention relates to a water quality determination system for determining water quality, and more particularly to a nitrification reaction determination system and a nitrification reaction determination method for determining the state of the nitrification reaction of a determination target subjected to biological treatment.

[0002] Knowing the water quality of treated water is very important for the quality control of treated water.

[0003] For example, in the treatment of nitrogen compounds in domestic wastewater discharged from drainage facilities such as washrooms, toilets, bathrooms, laundry rooms, and kitchens, biological treatment using nitrification and denitrification reactions is utilized. Through biological treatment, nitrogen compounds are released into the atmosphere as nitrogen gas via nitric acid. However, when a large amount of nitrogen compounds are contained in the wastewater or the concentration of nitrogen compounds in the wastewater is high, if the denitrification reaction proceeds while the nitrification reaction is insufficient, the water quality, odor, and chromaticity of the treated water cannot be ensured, and in particular, it may cause problems such as giving discomfort to users in circulating water treatment. Therefore, knowing the end of the nitrification reaction is an important factor in water treatment technology in order to maintain the quality of treated water.

[0004] In order to allow the treated water with sufficient progress of the nitrification reaction to proceed to the denitrification reaction, a device that measures the concentration of nitrogen oxides or ammonia in the treated water in the nitrification tank and adjusts the aeration air volume in the nitrification tank so as to achieve a concentration within a predetermined range is known (for example, see Patent Document 1).

[0005] Japanese Patent Application Laid-Open No. 2001-259689

[0006] Chapter 4 introduction to Water Treatment,[online],[Searched on October 20, 2024],Internet,<URL:https: / / dec.alaska.gov / media / 11475 / chapter-4-intro-to-water-treatment.pdf>

[0007] However, the apparatus described in Patent Document 1 has the problem of being complex overall because it is necessary to install a concentration meter to measure the nitrogen oxide concentration or ammonia concentration of the treated water in the nitrification tank.

[0008] Therefore, the problem that the present invention aims to solve is to provide a water quality determination system that can determine the water quality of treated water with a simple configuration. More specifically, the problem that the present invention aims to solve is to provide a nitrification reaction determination system and a nitrification reaction determination method that can determine the state of the nitrification reaction in treated water with a simple configuration.

[0009] While diligently conducting research to solve the above-mentioned problems, the inventors conceived the idea that the water quality of treated water could be determined based on the degree of chlorine reaction in nitrogen compounds. Based on this idea, the inventors, after repeated trial and error, succeeded in creating a water quality determination system, a nitrification reaction determination system, and a nitrification reaction determination method, which solve the problems of the present invention, with chlorine supply means, chlorine concentration measurement means, and determination means as basic elements. The present invention is completed based on the first-of-its-kind idea and successful examples made by the inventors.

[0010] In other words, according to each aspect of the present invention, the following embodiments are provided: [1-1] A water quality determination system comprising: a chlorine supply means; a chlorine concentration measuring means; and a determination means, wherein the chlorine supply means is capable of supplying chlorine to a target for determination; the chlorine concentration measuring means is capable of measuring the free chlorine concentration of the target for determination to which chlorine has been supplied by the chlorine supply means; and the determination means is capable of determining the water quality of the target for determination by comparing the free chlorine concentration measured by the chlorine concentration measuring means with an indicator chlorine concentration. [1-2] A nitrification reaction determination system comprising the water quality determination system of item [1-1] and a biological treatment tank, wherein the biological treatment tank is capable of accommodating a target to be subjected to biological treatment, the chlorine supply means is capable of supplying chlorine to the target to be subjected to biological treatment in the biological treatment tank, the chlorine concentration measuring means is capable of measuring the free chlorine concentration of the target to be subjected to chlorine supplied by the chlorine supply means, and the determination means is capable of determining the state of the nitrification reaction of the target to be subjected to biological treatment in the biological treatment tank by comparing the free chlorine concentration measured by the chlorine concentration measuring means with an index chlorine concentration. [1-3] The nitrification reaction determination system according to item [1-2], wherein the determination means determines that the nitrification reaction has been completed when the free chlorine concentration measured by the chlorine concentration measuring means matches the index chlorine concentration, and determines that the nitrification reaction has not been completed when the free chlorine concentration measured by the chlorine concentration measuring means does not match the index chlorine concentration. [1-4] The nitrification reaction determination system according to item [1-2] or [1-3], wherein the chlorine supply means is performed by electrolyzing chloride ions contained in water. [1-5] A nitrification reaction determination method comprising the steps of: supplying chlorine to a target subject to biological treatment and measuring the free chlorine concentration of the target subject to which chlorine has been supplied; and comparing the measured free chlorine concentration with an indicator chlorine concentration to determine the state of the nitrification reaction of the target subject to biological treatment.[2-1] A nitrification reaction determination system comprising: a chlorine supply means; a chlorine concentration measuring means; a determination means; and a biological treatment tank, wherein the biological treatment tank is capable of accommodating a target to be subjected to biological treatment; the chlorine supply means is capable of supplying chlorine to the target subjected to biological treatment in the biological treatment tank; the chlorine concentration measuring means is capable of measuring the free chlorine concentration of the target to be subjected to biological treatment supplied by the chlorine supply means; the determination means is capable of determining the state of the nitrification reaction of the target subjected to biological treatment in the biological treatment tank by comparing the free chlorine concentration measured by the chlorine concentration measuring means with an index chlorine concentration; and the determination means determines that the nitrification reaction has been completed when the free chlorine concentration measured by the chlorine concentration measuring means matches the index chlorine concentration, and determines that the nitrification reaction has not been completed when the free chlorine concentration measured by the chlorine concentration measuring means does not match the index chlorine concentration. [2-2] The nitrification reaction determination system according to item [2-1], wherein the chlorine supply means is performed by electrolyzing chloride ions contained in water. [2-3] A nitrification reaction determination method comprising the steps of: supplying chlorine to a target subject to biological treatment and measuring the free chlorine concentration of the target subject to treatment to which chlorine has been supplied; and comparing the measured free chlorine concentration with an index chlorine concentration to determine the state of the nitrification reaction of the target subject to biological treatment, wherein the nitrification reaction is determined to be completed when the free chlorine concentration measured in the step of measuring the free chlorine concentration matches the index chlorine concentration, and the nitrification reaction is determined not to be completed when the free chlorine concentration measured in the step of measuring the free chlorine concentration does not match the index chlorine concentration.

[0011] According to the present invention, chlorine can be supplied to the object to be evaluated, and the water quality can be determined based on the subsequent free chlorine concentration. Furthermore, according to the present invention, a chlorine supply means and residual chlorine concentration meter commonly provided in wastewater treatment systems can be used, resulting in an overall simple configuration. In addition, according to the present invention, chlorine can be supplied to the object to be evaluated subjected to biological treatment in a biological treatment tank, and the state of the nitrification reaction can be determined based on the subsequent free chlorine concentration. As a result, according to the present invention, the biological treatment can be controlled based on the state of the nitrification reaction.

[0012] Figure 1 is a graph showing the relationship between the amount of chlorine injected into water and the free chlorine concentration. Figure 2 is a graph showing the relationship between the amount of chlorine injected into ammonia nitrogen and the free chlorine concentration, ii) the relationship between the amount of chlorine injected into nitrite nitrogen and the free chlorine concentration, and iii) the relationship between the amount of chlorine injected into nitrate nitrogen and the free chlorine concentration. Figure 3 is a schematic diagram showing one embodiment of the nitrification reaction determination system. Figure 4 is a block diagram showing the functional configuration of the determination means 40. Figure 5 is a flowchart diagram showing the case when the nitrification reaction determination system 1 performs the determination process. Figure 6 is a flowchart diagram showing the case when the nitrification reaction determination system 1 performs the determination process and controls the biological treatment tank 10. Figure 7 is a schematic diagram showing another embodiment of the nitrification reaction determination system. Figure 8 is a flowchart diagram showing the case when the nitrification reaction determination system 1 performs the determination process. Figure 9 is a schematic diagram showing another embodiment of the nitrification reaction determination system.

[0013] The details of each aspect of the present invention will be described below, but the present invention can take various forms insofar as it achieves its objective.

[0014] In this specification, unless otherwise specified, each term is used in the sense commonly used by those skilled in the art, such as in the field of water treatment, and should not be interpreted as having an unduly restrictive meaning. Furthermore, since the assumptions and theories made herein are based on the inventors' prior knowledge and experience, the present invention is not limited solely to such assumptions and theories.

[0015] "Comprise, contain, include" means that elements other than those explicitly included can be added (synonymous with "at least include"), but it also encompasses "consist of" and "essentially constitute of". In other words, "comprise" can mean that it includes the explicitly included elements and any one or more of those elements, consists of the explicitly included elements, or essentially constitutes the explicitly included elements. "Have" is synonymous with "comprise". Elements include limitations such as parts, means, components, processes, conditions, and parameters. "And / or" means any one of the multiple related items listed, or any combination of two or more or all of them.

[0016] [Summary of the Invention] The water quality determination system of the present invention comprises a chlorine supply means, a chlorine concentration measuring means, and a determination means as basic elements. The water quality determination system supplies chlorine to the object to be determined by the chlorine supply means, measures the free chlorine concentration of the object to be determined to which chlorine has been supplied by the chlorine supply means by the chlorine concentration measuring means, and determines the water quality of the object to be determined by comparing the measured free chlorine concentration with an indicator chlorine concentration using the determination means.

[0017] Generally, the relationship between the amount of chlorine injected and the free chlorine concentration is known to vary depending on the water quality (components contained) (see, for example, Non-Patent Document 1). Non-Patent Document 1 describes discontinuous point chlorination and explains the reaction of chlorine in water. For example, as shown in Figure 1, in the case of water, the free chlorine concentration increases in proportion to the amount of chlorine injected. On the other hand, in the case of water containing ammonia components, the injected chlorine is consumed, so the free chlorine concentration tends to decrease. Therefore, it is conceivable that the free chlorine concentration will differ when chlorine is injected into a sample containing ammonia components, etc., compared to when chlorine is injected into a sample that does not contain ammonia components, etc. Therefore, we have developed a system that can supply chlorine to a sample and determine the water quality based on the subsequent free chlorine concentration, utilizing this principle.

[0018] The water quality determination system of the present invention, with its simple configuration of a chlorine supply means, a chlorine concentration measuring means, and a determination means, can determine the water quality of a target under various treatment environments. For example, the water quality determination system of the present invention can be used to determine the state of the nitrification reaction of treated water in biological treatment. It can also be applied to water quality testing of treated water in filtration treatment that does not require biological treatment, and to determining the residual chlorine concentration of treated water in a treated water storage tank.

[0019] [Nitrification Reaction Determination System of the First Embodiment] One specific embodiment of the water quality determination system is a nitrification reaction determination system equipped with a biological treatment tank. The nitrification reaction determination system comprises a biological treatment tank, a chlorine supply means, a chlorine concentration measuring means, and a determination means as basic elements. The nitrification reaction determination system can determine the state of the nitrification reaction of the target to be determined by supplying chlorine from the chlorine supply means to the target to be determined subjected to biological treatment in the biological treatment tank, measuring the free chlorine concentration of the target to be determined to which chlorine has been supplied, and comparing the measured free chlorine concentration with an indicator chlorine concentration.

[0020] In this biological treatment tank, the ammonia nitrogen in the water is oxidized to nitrite nitrogen and nitrate nitrogen by so-called "nitrifying bacteria" such as nitrite bacteria or nitrate bacteria under aerobic conditions (nitrification reaction). When this treated water is subjected to an anaerobic environment and oxygen is removed, the oxygen contained in these ions is utilized by microorganisms, and nitrogen gas is produced (denitrification reaction).

[0021] As mentioned above, in the case of plain water without other components, the free chlorine concentration increases in proportion to the amount of chlorine injected (see Figure 1). Based on this phenomenon, it is conceivable that the free chlorine concentration will differ when chlorine is injected into a sample subjected to biological treatment in a biological treatment tank when the nitrification reaction is insufficient (contains ammonia components) compared to when the nitrification reaction is sufficient (does not contain ammonia components). In other words, the behavior of the free chlorine concentration in relation to the amount of chlorine injected differs depending on the progress of the nitrification reaction of the sample. By utilizing this principle, chlorine can be supplied to a sample subjected to biological treatment, and the state of the nitrification reaction can be determined based on the subsequent free chlorine concentration.

[0022] The inventors investigated the relationship between the amount of chlorine injected and the free chlorine concentration in more detail and found that the relationship between the amount of chlorine injected into ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen and the free chlorine concentration is as shown in Figures 2i) to iii). When ammonia nitrogen is present in the water, the behavior of the free chlorine concentration in relation to the amount of chlorine injected is as shown in Figure 2i). When nitrite nitrogen is present in the water, the behavior of the free chlorine concentration in relation to the amount of chlorine injected is as shown in Figure 2ii). Furthermore, when nitrate nitrogen is present in the water, the behavior of the free chlorine concentration in relation to the amount of chlorine injected is as shown in Figure 2iii). In other words, when nitrate nitrogen is present in the water, the free chlorine concentration in relation to the amount of chlorine injected is almost identical to the actual amount of chlorine injected. Therefore, when the behavior of the free chlorine concentration in relation to the amount of chlorine injected matches the actual amount of chlorine injected, as shown in Figure 2iii), it indicates that the nitrification reaction being evaluated has proceeded sufficiently. As described above, the present invention can determine the progress of the nitrification reaction in biological treatment by utilizing the fact that the behavior of the free chlorine concentration in relation to the amount of chlorine injected differs depending on the components contained in the water.

[0023] The nitrification reaction determination system according to the first embodiment includes a biological treatment tank, a chlorine supply means, a chlorine concentration measuring means, and a determination means.

[0024] The first embodiment of the nitrification reaction determination system will be specifically explained with reference to Figure 3. The nitrification reaction determination system 1 includes a biological treatment tank 10, a chlorine supply means 20, a chlorine concentration measuring means 30, and a determination means 40. This nitrification reaction determination system 1 includes a storage tank 50 in which the determination target (hereinafter also referred to as "biologically treated water") 15 subjected to biological treatment in the biological treatment tank 10 is contained via a water supply pipe L2. The storage tank 50 is equipped with a chlorine supply means 20 for supplying chlorine to the biologically treated water 15, and a chlorine concentration measuring means 30 for measuring the free chlorine concentration of the determination target (hereinafter also referred to as "chlorine-supplied treated water") 16 to which chlorine has been supplied by the chlorine supply means 20.

[0025] This nitrification reaction determination system 1 has a structure that biologically treats the water to be treated 14 received from outside the system in a biological treatment tank 10, stores the resulting biologically treated water 15 in a storage tank 50, determines the progress of the nitrification reaction in the stored biologically treated water 15 using a determination means 40, and discharges the treated water outside the system.

[0026] The biological treatment tank 10 is capable of accommodating the water to be treated 14, which is supplied from outside the system via a water supply pipe L1. The water to be treated 14 includes, but is not limited to, wastewater such as domestic wastewater discharged from washrooms, toilets, kitchens, bathrooms, laundry rooms, etc., as well as urban wastewater, commercial facility wastewater, agricultural wastewater, industrial wastewater, sewage, rainwater, surface water, seawater, and tap water. Specific examples of wastewater include human waste, bath water, kitchen wastewater, and laundry wastewater.

[0027] The biological treatment tank 10 purifies the water to be treated 14 by subjecting it to biological treatment, for example, nitrification and denitrification reaction treatment by microorganisms. The microorganisms can be aerobic, anaerobic, or a combination of both.

[0028] The biological treatment tank 10 may contain aerobic and / or anaerobic microorganisms in a mixed state, or it may have both an aerobic and an anaerobic area, or it may be multiple tanks with separate aerobic and anaerobic tanks. If the biological treatment tank 10 has multiple tanks, for example, a partition such as a permeable membrane that allows water to pass through but not microorganisms can be provided to create a structure of two or more tanks. In the example in Figure 3, the biological treatment tank 10 contains aerobic and anaerobic microorganisms in a mixed state and has both an aerobic and an anaerobic area.

[0029] The biological treatment tank 10 is equipped with a membrane filtration unit 12 and a blower 13. The blower 13 is not limited to any blower that can supply air to the water to be treated 14 in the biological treatment tank 10 and does not cause the mixed microorganisms to settle. It is not limited to a blower, but may also be an agitator or a pump.

[0030] When air is supplied by the blower 13, the nitrification reaction of the water to be treated 14 takes place in the biological treatment tank 10. When the supply of air by the blower 13 is stopped, the denitrification reaction of the water to be treated 14 takes place in the biological treatment tank 10.

[0031] The membrane filtration unit 12 filters the biologically treated water 15. Examples of the membrane filtration unit 12 include MF (microfiltration membrane), UF (ultrafiltration membrane), NF (nanofiltration membrane), ceramic filters, and metal membranes.

[0032] The biological treatment tank 10 and the storage tank 50 are connected by a water supply pipe L2 equipped with a pump 17.

[0033] The storage tank 50 is capable of accommodating the biologically treated water 15 that has been filtered in the biological treatment tank 10 by the membrane filtration unit 12 and then sent out via the water supply pipe L2 by the pump 17.

[0034] The storage tank 50 is equipped with a chlorine supply means 20 for supplying chlorine to the biologically treated water 15, and a chlorine concentration measuring means 30 for measuring the free chlorine concentration of the chlorine-supplied treated water 16.

[0035] The chlorine supply means 20 is configured to supply chlorine to the biologically treated water 15. In the example shown in Figure 3, the chlorine supply means 20 is configured to supply chlorine to the biologically treated water 15 in the storage tank 50.

[0036] The chlorine supplied from the chlorine supply means 20 is not particularly limited as long as it contains chloride ions, and examples include hypochlorous acid and hypochlorite ions, chlorous acid and chlorite ions, chloric acid and chlorate ions, perchloric acid and perchlorate ions, as well as chloride ions produced by the electrolysis of chloride ions.

[0037] The chlorine supply means 20 is not particularly limited in terms of the method of supplying chlorine, as long as it has a structure that supplies chlorine to the biologically treated water 15. For example, the chlorine supply means 20 may be equipped with a chlorine discharge function such as a motor or pump, thereby supplying chlorine in the form of solid, powder, granules, liquid, suspension, foam, mist, preferably liquid or mist chlorine, to the biologically treated water 15. Alternatively, for example, the chlorine supply means 20 may be structured to supply chlorine to the biologically treated water 15 by electrolyzing water containing chloride ions.

[0038] The chlorine concentration measuring means 30 is configured to measure the free chlorine concentration of the chlorine-supplied treated water 16. Preferably, the chlorine concentration measuring means 30 is a sensor that transmits the measured free chlorine concentration (hereinafter also referred to as "measured chlorine concentration") as an electrical signal to the determination means 40. The chlorine concentration measuring means 30 may also be a device having a detection probe such as an electrode. In the example of Figure 3, the chlorine concentration measuring means 30 is configured to measure the free chlorine concentration of the chlorine-supplied treated water 16 in the storage tank 50.

[0039] The measurement of free chlorine concentration by the chlorine concentration measuring means 30 may be performed continuously or intermittently.

[0040] The determination means 40 is configured to continuously or intermittently receive the measured chlorine concentration as an input value, compare the measured chlorine concentration with an indicator chlorine concentration, and determine the state of the nitrification reaction of the biologically treated water 15.

[0041] As the index chlorine concentration, there is the free chlorine concentration based on nitrate nitrogen with respect to the chlorine injection amount, which has been acquired in advance (known) and shown in iii) of FIG. 2. If the nitrification reaction has ended, the supplied chlorine is not consumed, so the index chlorine concentration and the measured chlorine concentration match. Therefore, one index chlorine concentration is sufficient, but since the chlorine concentration at the time of supply can vary depending on the external environment such as temperature, two or more index chlorine concentrations may be set.

[0042] For example, when the index chlorine concentration is one and is the free chlorine concentration based on nitrate nitrogen with respect to the chlorine injection amount shown in iii) of FIG. 2, the determination means 40 determines that the nitrification reaction has ended when the measured chlorine concentration matches the index chlorine concentration, and determines that the nitrification reaction has not ended when the measured chlorine concentration does not match the index chlorine concentration.

[0043] FIG. 4 is a block diagram showing the functional configuration of the determination means 40. As illustrated in FIG. 4, the determination means 40 includes a CPU 410 and a storage unit 440.

[0044] The determination means 40 has a CPU (Central Processing Unit) 410 as a control unit that comprehensively controls the operation of the determination means 40.

[0045] The CPU 410 is based on an OS (Operating System) program and executes middleware and applications. The CPU 410 is connected to a storage unit 440, a display unit 420, an input unit 430, etc. via a bus. Also, a communication unit may be connected.

[0046] The storage unit 440 includes a ROM (Read Only Memory), a RAM (Random Access Memory), a hard disk drive, etc. Various programs are stored in the ROM, and the CPU 410 executes various processes according to these programs, thereby realizing each function of the determination means 40. The RAM is used as a work memory that is temporarily stored when the CPU 410 executes a process based on a program. The hard disk drive has an index chlorine concentration, etc. Note that the storage unit 440 may be configured to be stored on cloud computing or edge computing.

[0047] The display unit 420 displays, for example, the measured chlorine concentration, the end of the nitrification reaction, etc. on various screens, and can be, for example, a liquid crystal display. The input unit 430 automatically or manually inputs, for example, the measured chlorine concentration from the chlorine concentration measuring means 30, and can be, for example, a keyboard or a mouse.

[0048] An example of the method for determining the nitrification reaction by the nitrification reaction determination system 1 will be described using the flowchart shown in FIG. 5. In the example of FIG. 5, the index chlorine concentration is set to the free chlorine concentration based on the nitrate nitrogen with respect to the chlorine injection amount shown in iii) of FIG. 2.

[0049] As illustrated in Figure 5, the water to be treated 14 in the biological treatment tank 10 is subjected to biological treatment (S101). Next, the biologically treated water 15 that has been subjected to biological treatment in the biological treatment tank 10 is sent to the storage tank 50 (S102). Chlorine is supplied to the biologically treated water 15 in the storage tank 50 by the chlorine supply means 20 (S103). The free chlorine concentration of the chlorine-supplied treated water 16 by the chlorine supply means 20 is measured by the chlorine concentration measuring means 30 (S104). In the determination means 40, the chlorine concentration measured by the chlorine concentration measuring means 30 is compared with the index chlorine concentration (S105). Then, in the determination means 40, if the measured chlorine concentration matches the free chlorine concentration of nitrate nitrogen relative to the amount of chlorine injected, as shown in the index chlorine concentration (iii in Figure 2), it is determined that the nitrification reaction of the biologically treated water 15 has been completed (S106A). On the other hand, if the measured chlorine concentration does not match the free chlorine concentration of nitrate nitrogen relative to the chlorine injection amount shown in the indicator chlorine concentration (iii in Figure 2), it is determined that the nitrification reaction of the biologically treated water 15 has not been completed (S106B).

[0050] The determination means 40 can also be configured to control the biological treatment in the biological treatment tank 10. Specifically, in addition to determining the state of the nitrification reaction of the biologically treated water 15, the determination means 40 is configured to control the biological treatment of the biologically treated water 15 based on the determined state of biological treatment of the biologically treated water 15.

[0051] For example, the determination means 40 may control the oxygen supply state in the biological treatment tank 10 by adjusting the on / off status, air supply volume, and air supply time of the blower 13 in the biological treatment tank 10 based on the state of biological treatment. In addition to turning the air supply of the blower 13 on and off, the air supply volume and supply time may be controlled immediately or with a delay.

[0052] An example of a method for determining the nitrification reaction that also incorporates the control function of biological processing by the nitrification reaction determination system 1 will be explained using the flowchart shown in Figure 6.

[0053] As illustrated in Figure 6, the water to be treated 14 in the biological treatment tank 10 is subjected to biological treatment (S101). Next, the biologically treated water 15 that has been subjected to biological treatment in the biological treatment tank 10 is sent to the storage tank 50 (S102). Chlorine is supplied to the biologically treated water 15 in the storage tank 50 by the chlorine supply means 20 (S103). The free chlorine concentration of the chlorine-supplied treated water 16 by the chlorine supply means 20 is measured by the chlorine concentration measuring means 30 (S104). In the determination means 40, the chlorine concentration measured by the chlorine concentration measuring means 30 is compared with the index chlorine concentration (S105). Specifically, if the measured chlorine concentration matches the free chlorine concentration of nitrate nitrogen relative to the chlorine injection amount shown in iii) of Figure 2, it is determined that the nitrification reaction of the biologically treated water 15 has been completed, and the air supply from the blower 13 in the biological treatment tank 10 is stopped, or the biological treatment is stopped (S106C). On the other hand, if the measured chlorine concentration does not match the free chlorine concentration of nitrate nitrogen relative to the chlorine injection amount shown in iii) of Figure 2, it is determined that the nitrification reaction of the biologically treated water 15 has not been completed, and the air supply from the blower 13 in the biological treatment tank 10 is maintained, or the biological treatment is continued (S106D).

[0054] The nitrification reaction determination system may include other components in addition to the biological treatment tank, chlorine supply means, chlorine concentration measuring means, and determination means. Examples of other components include the water supply pipe L and storage tank 50 illustrated in Figure 3.

[0055] The water supply pipe L is configured to be able to supply treated water such as the water to be treated 14, the biologically treated water 15, and the chlorine-supplied treated water 16. The material, diameter, length, etc., of the water supply pipe L are not particularly limited as long as they can carry each type of treated water.

[0056] According to the nitrification reaction determination system of the first embodiment, chlorine is supplied to the biologically treated water 15 subjected to biological treatment in the biological treatment tank 10, and the state of the nitrification reaction can be determined based on the subsequent free chlorine concentration. Based on the state of the nitrification reaction, the biological treatment can also be controlled. Furthermore, a chlorine supply means and residual chlorine concentration meter for chlorine disinfection, which are generally provided in wastewater treatment systems, can be used, and as a result, the overall configuration can be simplified.

[0057] [Nitrification reaction determination system of the second embodiment] The nitrification reaction determination system of the second embodiment includes a biological treatment tank, a chlorine supply means, a chlorine concentration measuring means, and a determination means.

[0058] The nitrification reaction determination system of the second embodiment will be specifically explained with reference to Figure 7. In Figure 7, components common to the nitrification reaction determination system of Figure 3 are denoted by the same reference numerals. Furthermore, in the following, as a general rule, the differences between the nitrification reaction determination system of the second embodiment and the nitrification reaction determination system of the first embodiment will be explained, and the parts that overlap with the nitrification reaction determination system of the first embodiment will be omitted from the explanation.

[0059] This nitrification reaction determination system 1 has a structure that, in the water supply pipe L2 from receiving the water to be treated 14 from outside the system, biologically treating it in the biological treatment tank 10, to sending the resulting biologically treated water 15 to the storage tank 50, determines the progress of the nitrification reaction in the biologically treated water 15 using a determination means 40, and then sends the treated water to the storage tank 50.

[0060] The chlorine supply means 20 is configured to supply chlorine to the biologically treated water 15 in the water supply pipe L2. The chlorine concentration measuring means 30 is configured to measure the free chlorine concentration of the chlorine-supplied treated water 16 in the water supply pipe L2.

[0061] The determination means 40 is configured to continuously or intermittently receive the measured chlorine concentration of the chlorine-supplied treated water 16 in the water supply pipe L2 as an input value, compare the measured chlorine concentration with an indicator chlorine concentration, and determine the state of the nitrification reaction of the biologically treated water 15. This nitrification reaction determination system 1 may be configured to include a circulation means (not shown) that returns treated water, which the determination means 40 has determined to have not completed the nitrification reaction, to the biological treatment tank 10.

[0062] The storage tank 50 is capable of accommodating the chlorine-supplied treated water 16, whose nitrification reaction progress has been determined by the determination means 40.

[0063] An example of a method for determining the nitrification reaction using the nitrification reaction determination system 1 will be explained using the flowchart shown in Figure 8.

[0064] As illustrated in Figure 8, the water to be treated 14 in the biological treatment tank 10 is subjected to biological treatment (S201). Next, the biologically treated water 15 that has been subjected to biological treatment in the biological treatment tank 10 is sent to the water supply pipe L2 (S202). Chlorine is supplied to the biologically treated water 15 in the water supply pipe L2 by the chlorine supply means 20 (S203). The free chlorine concentration of the chlorine-supplied treated water 16 supplied by the chlorine supply means 20 is measured by the chlorine concentration measuring means 30 (S204). In the determination means 40, the chlorine concentration measured by the chlorine concentration measuring means 30 is compared with the index chlorine concentration (S205). Specifically, if the measured chlorine concentration matches the index chlorine concentration, it is determined that the nitrification reaction of the biologically treated water 15 has been completed (S206A). The chlorine-supplied treated water 16, which has been determined to have completed the nitrification reaction, is sent to the storage tank 50 (S207). On the other hand, if the measured chlorine concentration does not match the indicator chlorine concentration, it is determined that the nitrification reaction of the biologically treated water 15 has not been completed (S206B). The chlorine-supplied treated water 16, which has been determined to have not been completed, is returned to the biological treatment tank 10, for example, by a circulation means, and subjected to biological treatment again.

[0065] According to the nitrification reaction determination system 1 of the second embodiment, the risk of sending / storing treated water with insufficient nitrification reaction to the storage tank 50 can be reduced.

[0066] [Third embodiment of nitrification reaction determination system] The third embodiment of the nitrification reaction determination system includes a biological treatment tank, a chlorine supply means, a chlorine concentration measuring means, and a determination means.

[0067] The nitrification reaction determination system of the third embodiment will be specifically explained with reference to Figure 9. In Figure 9, components common to the nitrification reaction determination system of Figure 3 are denoted by the same reference numerals. Furthermore, in the following, as a general rule, the differences between the nitrification reaction determination system of the third embodiment and the nitrification reaction determination system of the first embodiment will be explained, and the parts that overlap with the nitrification reaction determination system of the first embodiment will be omitted from the explanation.

[0068] This nitrification reaction determination system 1 has a structure that, in the water supply pipe L3 from which the stored biologically treated water 15 is sent out of the system, determines the progress of the nitrification reaction in the biologically treated water 15 using a determination means 40 and sends out the treated water.

[0069] The storage tank 50 is capable of containing the biologically treated water 15 that has been filtered by the membrane filtration unit 12 in the biological treatment tank 10 and then sent out via the water supply pipe L2 by the pump 17. The biologically treated water 15 contained in the storage tank 50 is sent out to the water supply pipe L3 by the pump 17.

[0070] The chlorine supply means 20 is configured to supply chlorine to the biologically treated water 15 in the water supply pipe L3. The chlorine concentration measuring means 30 is configured to measure the free chlorine concentration of the chlorine-supplied treated water 16 in the water supply pipe L3.

[0071] The determination means 40 is configured to continuously or intermittently receive the measured chlorine concentration of the chlorine-supplied treated water 16 in the water supply pipe L3 as an input value, compare the measured chlorine concentration with an indicator chlorine concentration, and determine the state of the nitrification reaction of the biologically treated water 15.

[0072] According to the nitrification reaction determination system 1 of the third embodiment, after confirming that the nitrification reaction has been completed, the biologically treated water subjected to biological treatment can be sent to the user as purified water 18.

[0073] [Another Embodiment of the Invention] Another embodiment of the present invention is a method for determining a nitrification reaction, which is realized by a nitrification reaction determination system according to one embodiment of the present invention. The method for determining a nitrification reaction includes, for example, the steps of supplying chlorine to a target subject to biological treatment and measuring the free chlorine concentration of the target subject to which chlorine has been supplied, and comparing the measured free chlorine concentration with an indicator chlorine concentration to determine the state of the nitrification reaction of the target subject to biological treatment.

[0074] One embodiment of the present invention is a water quality determination system that can determine the quality of the target water with an overall simple configuration, and can therefore be used for determining various targets such as the progress of nitrification reactions in biological treatment, the water quality in filtration treatment, and the residual chlorine concentration in treated water storage tanks.

[0075] 1. Nitrification reaction determination system 10. Biological treatment tank 12. Membrane filtration unit 13. Blower 14. Water to be treated 15. Biologically treated water 16. Chlorine-supplied treated water 17. Pump 18. Clean water 20. Chlorine supply means 30. Chlorine concentration measuring means 40. Determination means 410. CPU 420. Display unit 430. Input unit 440. Memory unit L. Water supply pipe P. Pump Cross-reference of related applications

[0076] This application claims priority to Japanese Patent Application No. 2024-186501, filed on 23 October 2024, the entirety of which is incorporated herein by reference. Furthermore, the entirety of all documents referenced in the detailed description of the invention of this application, including Patent Document 1 and Non-Patent Document 1, is incorporated herein by reference.

Claims

1. A water quality determination system comprising a chlorine supply means, a chlorine concentration measuring means, and a determination means, wherein the chlorine supply means is capable of supplying chlorine to a target for determination, the chlorine concentration measuring means is capable of measuring the free chlorine concentration of the target for determination to which chlorine has been supplied by the chlorine supply means, and the determination means is capable of determining the water quality of the target by comparing the free chlorine concentration measured by the chlorine concentration measuring means with an indicator chlorine concentration.

2. A nitrification reaction determination system comprising the water quality determination system described in claim 1 and a biological treatment tank, wherein the biological treatment tank is capable of accommodating a target to be subjected to biological treatment, the chlorine supply means is capable of supplying chlorine to the target subjected to biological treatment in the biological treatment tank, the chlorine concentration measuring means is capable of measuring the free chlorine concentration of the target to be subjected to chlorine supply by the chlorine supply means, and the determination means is capable of determining the state of the nitrification reaction of the target subjected to biological treatment in the biological treatment tank by comparing the free chlorine concentration measured by the chlorine concentration measuring means with an indicator chlorine concentration.

3. The nitrification reaction determination system according to claim 2, wherein the determination means determines that the nitrification reaction has been completed when the free chlorine concentration measured by the chlorine concentration measuring means matches the index chlorine concentration, and determines that the nitrification reaction has not been completed when the free chlorine concentration measured by the chlorine concentration measuring means does not match the index chlorine concentration.

4. The nitrification reaction determination system according to claim 2 or 3, wherein the chlorine supply means is performed by electrolyzing chloride ions contained in water.

5. A method for determining a nitrification reaction, comprising the steps of: supplying chlorine to a target subject to biological treatment and measuring the free chlorine concentration of the target subject to chlorine supply; and comparing the measured free chlorine concentration with an indicator chlorine concentration to determine the state of the nitrification reaction of the target subject to biological treatment.

Images