Water treatment device and water treatment method

Abstract

To provide a water treatment apparatus and a water treatment method that are capable of reducing the manpower required when starting up the apparatus and automatically starting up the apparatus and recovering nitrification activity in the water treatment in which to-be-treated water containing ammonia nitrogen is nitrified by biological treatment.SOLUTION: Provided is a water treatment apparatus 1 for nitrifying to-be-treated water containing ammoniacal nitrogen by biological treatment, comprising: a biological treatment tank 10 in which the to-be-treated water is mixed with autotrophic bacteria; supply means for continuously supplying to-be-treated water to the biological treatment tank 10; an ammoniacal nitrogen meter 14 for measuring the ammoniacal nitrogen concentration of the biological treatment water; and a control unit 12 for automatically controlling the flow rate of the to-be-treated water flowing into the biological treatment tank 10 so that the ammoniacal nitrogen concentration of the to-be-treated water remains below a set value.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a water treatment device and a water treatment method for nitrifying water containing ammonia nitrogen through biological treatment. [Background technology]

[0002] Conventionally, hydrofluoric acid, ammonia, nitric acid, etc. have been used in the manufacturing process of semiconductors such as integrated circuits (ICs), etc. For this reason, wastewater containing fluorine (hydrofluoric acid), nitrogen (ammonia, nitric acid), etc. is discharged as waste liquid from the process.

[0003] Fluorine in wastewater is generally removed physicochemically, for example, by adding calcium to form calcium fluoride. In order to sufficiently remove fluorine from wastewater, it is desirable to create conditions in which a significant amount of calcium ions remain. In general, the target fluorine concentration in fluoride-removed water is set to about 10 mg / L or less, and in this case, it is desirable to set the residual calcium concentration in the fluoride-removed water to about 100 to 1000 mg / L.

[0004] On the other hand, biological denitrification is generally used to remove nitrogen. This biological denitrification is a method of removing nitrogen by utilizing nitrate respiration in an anoxic state by denitrifying bacteria, which are facultative anaerobic bacteria. In this biological denitrification process, wastewater is first nitrified to convert the ammonia nitrogen in the wastewater into nitrite nitrogen or nitrate nitrogen, and then a hydrogen donor such as methanol is added to create an anoxic state to perform the denitrification process.

[0005] By combining the above-mentioned fluorine removal and nitrogen removal, fluorine and nitrogen are removed from wastewater. Since wastewater containing a large amount of fluorine has an adverse effect on biological treatment using bacteria, biological denitrification treatment is carried out after removing the fluorine from the wastewater. Therefore, wastewater that is the target of biological denitrification treatment often contains a large amount of calcium (see Patent Document 1).

[0006] In the nitrification of biological denitrification, for example, the activated sludge method, the biofilm method (for example, the fixed bed method or the fluidized bed method), and the granular method are used. In general, the activated sludge method is a low-load treatment (for example, 0.1 to 0.3 kg-N / (m 3 d)) is used, and in the biofilm method and granular method, high load treatment (e.g. 0.5 to 1.0 kg-N / (m 3 d)) is carried out (see Patent Document 1).

[0007] In such nitrification equipment, when initially starting up the equipment or restarting it after shutting down, it is common to sample treated water from the nitrification tank once or several times a day and measure the ammoniacal nitrogen concentration by manual analysis. When it is determined that the ammoniacal nitrogen concentration has dropped sufficiently, the load is adjusted to increase the nitrification activity.

[0008] However, this method requires a long period of time before start-up, and during the start-up period, manual analysis and load adjustment are required. In Patent Document 2, a means for measuring the ammoniacal nitrogen concentration of the nitrification treatment water in the nitrification tank is installed, and the measured ammoniacal nitrogen concentration is compared with a preset ammoniacal nitrogen concentration (1 to 10 mg / L), and if the measured value is below the set value, the nitrogen load in the nitrification tank is adjusted so that the measured value is equal to or higher than the set value, thereby maintaining a high growth rate of nitrifying bacteria and solving such problems.

[0009] However, in reality, if the load is increased while the ammonia nitrogen concentration is kept high at 1 mg / L or more, the ammonia nitrogen concentration in the treated water of the nitrification tank may increase without decreasing, making stable treatment impossible, especially in high-load treatment. The reason for this is that when the nitrification activity of the nitrification tank has not yet increased to a level sufficient to treat the ammonia nitrogen volume load, by increasing the load, the nitrification activity gradually cannot keep up, the ammonia nitrogen concentration becomes temporarily or constantly high, and the associated increase in free ammonia leads to greater inhibition of nitrification.

[0010] As in Patent Document 2, if the ammonia nitrogen concentration of the treated water in the nitrification tank is adjusted to be kept at a predetermined concentration or higher, if the nitrification activity cannot keep up with the increased load, the ammonia nitrogen concentration of the treated water will gradually increase and the nitrification activity will further decrease. In this case, it will be necessary to repeat the same operation to increase the nitrification activity again, and it will take a very long time to start up. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Patent No. 4865211 [Patent Document 2] Japanese Patent Application Publication No. 08-126897 Summary of the Invention [Problem to be solved by the invention]

[0012] An object of the present invention is to provide a water treatment apparatus and a water treatment method which, in a water treatment process in which water to be treated containing ammonia nitrogen is nitrified by biological treatment, can reduce the manpower required for starting up the apparatus and can automatically start up the apparatus and restore nitrification activity. [Means for solving the problem]

[0013] The present invention relates to a method for treating water containing ammonia nitrogen by biological treatment. Under aerobic conditions A water treatment device for nitrification, comprising: mixing the water to be treated with autotrophic bacteria; and nitrification a supply means for continuously supplying the water to be treated to the biological treatment tank; nitrification and a control means for automatically controlling the flow rate of the treated water flowing into the biological treatment tank so that the ammonia nitrogen concentration of the biological treatment water is maintained at or below a set value.

[0014] It is preferable that the water treatment device further comprises a means for measuring the ammoniacal nitrogen concentration of the treated water, and the control means controls the flow rate of the treated water flowing into the biological treatment tank based on the ammoniacal nitrogen concentration of the treated water so that the ammoniacal nitrogen concentration of the biological treatment water is maintained below a set value.

[0015] It is preferable that the water treatment device further includes a filtering means for filtering the biologically treated water, and the biologically treated water ammonia nitrogen concentration measuring means measures the ammonia nitrogen concentration of the biologically treated water filtered by the filtering means.

[0016] In the water treatment device, when the biological treatment water ammonia nitrogen concentration measuring means and the treated water ammonia nitrogen concentration measuring means are provided, the treated water ammonia nitrogen concentration measuring means is preferably a coulometric titration type ammonia nitrogen meter.

[0017] In the water treatment device, it is preferable that the supply means includes a pump, and the control unit controls an inverter of the pump to control the flow rate of the water to be treated flowing into the biological treatment tank.

[0018] The water treatment device further includes a treated water tank for storing the treated water, and a valve whose opening can be adjusted to branch the flow path of the treated water from the treated water tank to the biological treatment tank and the treated water tank, upstream of the biological treatment tank, and it is preferable that the control unit controls the flow rate of the treated water flowing into the biological treatment tank by controlling the pump inverter and the opening of the valve.

[0019] In the water treatment device, the set value is preferably an ammoniacal nitrogen concentration of 1 mg / L or less.

[0020] In the water treatment device, it is preferable that the control unit controls the amount of nutrients added to the biological treatment tank based on the amount of ammoniacal nitrogen load.

[0021] In the water treatment device, the water to be treated preferably contains 100 mg / L or more of calcium.

[0022] The present invention relates to a method for treating water containing ammonia nitrogen by biological treatment. Under aerobic conditions A water treatment method for nitrification, comprising mixing the water to be treated with autotrophic bacteria, and nitrification The water to be treated is continuously supplied to a biological treatment tank for purifying the water. nitrification and automatically controlling the flow rate of the water to be treated flowing into the biological treatment tank so that the ammonia nitrogen concentration of the biologically treated water obtained by the above process is kept at or below a set value.

[0023] In the water treatment method, it is preferable to control the flow rate of the water to be treated flowing into the biological treatment tank based on the ammoniacal nitrogen concentration of the water to be treated so that the ammoniacal nitrogen concentration of the biological treatment water is maintained below a set value.

[0024] In the water treatment method, it is preferable to filter the biologically treated water and measure the ammoniacal nitrogen concentration of the filtered biologically treated water.

[0025] In the water treatment method, it is preferable to measure the ammonia nitrogen concentration of the biological treatment water, and the ammonia nitrogen concentration of the water to be treated when measuring the ammonia nitrogen concentration of the water to be treated, using a coulometric titration type ammonia nitrogen meter.

[0026] In the water treatment method, it is preferable to control the flow rate of the water to be treated flowing into the biological treatment tank by controlling an inverter of a pump.

[0027] In the water treatment method, it is preferable to further provide a treated water tank for storing the treated water upstream of the biological treatment tank, and a valve whose opening can be adjusted to branch the flow path of the treated water to the biological treatment tank and the treated water tank, and to control the flow rate of the treated water flowing into the biological treatment tank by controlling the pump inverter and the opening of the valve.

[0028] In the water treatment method, the set value is preferably an ammoniacal nitrogen concentration of 1 mg / L or less.

[0029] In the water treatment method, it is preferable to control the amount of nutrients added to the biological treatment tank based on the amount of ammoniacal nitrogen loaded.

[0030] In the water treatment method, the water to be treated preferably contains 100 mg / L or more of calcium. Effect of the Invention

[0031] The present invention provides a water treatment apparatus and a water treatment method that can reduce the manpower required for starting up the apparatus and automatically start up the apparatus and restore nitrification activity in a water treatment process in which water to be treated that contains ammonia nitrogen is nitrified by biological treatment. [Brief description of the drawings]

[0032] [Figure 1] 1 is a schematic diagram illustrating an example of a water treatment device according to an embodiment of the present invention. [Diagram 2] FIG. 4 is a schematic configuration diagram showing another example of a water treatment device according to an embodiment of the present invention. [Diagram 3] FIG. 4 is a schematic configuration diagram showing another example of a water treatment device according to an embodiment of the present invention. [Figure 4] FIG. 4 is a schematic configuration diagram showing another example of a water treatment device according to an embodiment of the present invention. [Diagram 5] 4 is a flowchart showing an example of a control flow by the control device 12. [Figure 6]1 is a graph showing the change in ammoniacal nitrogen volumetric loading amount [kg-N / (m3-tank volume·d)] and ammoniacal nitrogen concentration [mg / L] of biologically treated water versus the number of days elapsed in a comparative example. [Figure 7] 1 is a graph showing the change in ammonia nitrogen volumetric loading amount [kg-N / (m3-tank volume·d)] and ammonia nitrogen concentration [mg / L] of biologically treated water versus the number of days elapsed in an example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes an embodiment of the present invention. The embodiment is merely an example of implementing the present invention, and the present invention is not limited to the embodiment.

[0034] [Water treatment device and water treatment method] An example of a water treatment apparatus according to an embodiment of the present invention is outlined in FIG. 1, and its configuration will be described.

[0035] The water treatment device 1 shown in Fig. 1 is a water treatment device that nitrifies water to be treated that contains ammonia nitrogen through biological treatment using an activated sludge method, a biofilm method, a granule method, or the like. The water treatment device 1 includes a biological treatment tank (nitrification tank) 10 in which the water to be treated is mixed with autotrophic bacteria, a pump 16 as a supply means for continuously supplying the water to be treated to the biological treatment tank 10, an ammonia nitrogen concentration meter 14 as a biological treatment water ammonia nitrogen concentration measuring means for measuring the ammonia nitrogen concentration of the biological treatment water obtained by the biological treatment, and a control device 12 as a control means for automatically controlling the flow rate of the water to be treated flowing into the biological treatment tank 10 so as to maintain the ammonia nitrogen concentration of the biological treatment water at or below a set value.

[0036] In the water treatment device 1, a treated water supply pipe 18 is connected to a treated water inlet 26 of the biological treatment tank 10 via a pump 16. A treated water pipe 20 is connected to a treated water outlet 28 of the biological treatment tank 10. An ammonia nitrogen concentration meter 14 is installed in the treated water pipe 20. An aeration device 22 that supplies oxygen-containing gas such as air is installed at the inner bottom of the biological treatment tank 10. A screen 24 is installed to surround the treated water outlet 28 of the biological treatment tank 10, making it possible to prevent sludge and the like from flowing into the treated water.

[0037] The control device 12 is connected to an ammoniacal nitrogen concentration meter 14 and a pump 16 by wired or wireless electrical connections or the like.

[0038] The water treatment method and the operation of the water treatment device 1 according to this embodiment will be described.

[0039] The water to be treated that contains ammonia nitrogen is supplied by a pump 16 through a water to be treated supply pipe 18 and a water to be treated inlet 26 to the biological treatment tank 10. In the biological treatment tank 10, the water to be treated is mixed with autotrophic bacteria, and the ammonia nitrogen contained in the water to be treated is nitrified by biological treatment (nitrification treatment) while an oxygen-containing gas such as air is supplied and diffused by an aeration device 22 (nitrification step). The biologically treated water that has been subjected to nitrification treatment is discharged as treated water from a treated water outlet 28 through a treated water pipe 20. The treated water discharged from the treated water pipe 20 may be sent to a downstream anaerobic tank (denitrification tank) not shown.

[0040] The nitrification process is a process in which ammonia nitrogen is oxidized to at least one of nitrite nitrogen and nitrate nitrogen by autotrophic bacteria under aerobic conditions.

[0041] In the start-up stage of nitrification treatment, after the load is increased, the ammonia nitrogen concentration of the treated water increases once, but then the nitrification activity catches up and decreases. At this time, as the ammonia nitrogen concentration of the treated water increases, the free ammonia concentration also increases. Even at extremely low concentrations, free ammonia can cause nitrification inhibition, and depending on the degree of increase in free ammonia, the nitrification activity may decrease and the load may not be able to be stably taken.

[0042] In the water treatment device 1, the water to be treated that contains ammoniacal nitrogen is continuously supplied to the biological treatment tank 10 by a pump 16 (water to be treated supply step), and nitrification is carried out in the biological treatment tank 10 (nitrification step). For example, the ammoniacal nitrogen concentration of the biological treatment water is measured by an ammoniacal nitrogen concentration meter 14 in the treated water piping 20 (biological treatment water ammoniacal nitrogen concentration measurement step), and the measured ammoniacal nitrogen concentration of the biological treatment water is compared with a preset ammoniacal nitrogen concentration, and the flow rate of the water to be treated flowing into the biological treatment tank 10 is automatically controlled by a control device 12 so that the measured ammoniacal nitrogen concentration of the biological treatment water is kept below the set value (flow rate control step).

[0043] The ammonia nitrogen concentration in the biological treatment water is automatically measured by the ammonia nitrogen concentration meter 14, and the load is increased or decreased according to the measured ammonia nitrogen concentration, thereby preventing excessive free ammonia from remaining, and reducing the manpower required to increase nitrification activity while maintaining stable treated water quality. When starting up the nitrification device, the manpower required for water quality analysis and load adjustment is reduced, and even when starting up to a high load, the ammonia nitrogen concentration of the treated water in the biological treatment tank 10 is maintained at a stable value, and the load is adjusted so that the nitrification activity does not decrease, allowing the nitrification device to be started up automatically and the nitrification activity to be restored, and stable nitrification can be performed.

[0044] The control device 12 automatically controls the flow rate of the water to be treated flowing into the biological treatment tank 10 based on the measurement result of the ammoniacal nitrogen concentration meter 14. The control device 12 automatically controls the flow rate of the water to be treated so that the measurement result of the ammoniacal nitrogen concentration becomes equal to or less than the set ammoniacal nitrogen concentration value. The flow rate control may be any commonly used flow rate adjustment method, and is not particularly limited. Examples of the flow rate control method include inverter control of the pump 16 and adjustment of the opening of a valve provided in the water to be treated supply pipe 18.

[0045] The control device 12 is composed of, for example, a microcomputer and electronic circuits, which are composed of a calculation means such as a CPU that operates a program, and storage means such as a ROM and RAM that store the program and the calculation results. The control device 12 has a function of automatically controlling the flow rate of the water to be treated flowing into the biological treatment tank 10, for example by automatically controlling the inverter of the pump 16 and adjusting the opening of a valve provided in the water to be treated supply pipe 18, so that the ammonia nitrogen concentration of the biological treatment water measured by the ammonia nitrogen concentration meter 14 is kept below a set value.

[0046] The ammoniacal nitrogen concentration meter 14 is required to be able to measure the ammoniacal nitrogen in the biological treatment water, i.e., the water inside the biological treatment tank 10 or the treated water, and the water intake or measurement part needs to be installed in the treated water piping 20 or the biological treatment tank 10.

[0047] The ammonia nitrogen concentration meter is not particularly limited as long as it can be measured online, but it is particularly preferable that it is a coulometric titration type ammonia nitrogen meter. The coulometric titration type ammonia nitrogen meter is a measurement by a coulometric titration method that applies coulometry, and in principle, it is not necessary to create a calibration curve, and bromine, which has high selectivity and reactivity with ammonia, can be used as a titrant. The electrode part is not easily soiled, and even if scale such as Ca accumulates, the measuring part does not need to be installed in the biological treatment tank 10, and it is relatively easy to clean with acid. For the above reasons, by using a coulometric titration type ammonia nitrogen meter, it is possible to reduce the number of people required for maintenance.

[0048] The ammoniacal nitrogen load in the biological treatment tank 10 is determined by the ammoniacal nitrogen concentration in the water to be treated, the flow rate of the water to be treated flowing into the biological treatment tank 10, and the volume of the biological treatment tank 10. Since the ammoniacal nitrogen concentration in the water to be treated varies daily depending on the operating conditions of the factory, etc., it is preferable to also measure the ammoniacal nitrogen concentration in the water to be treated in order to more accurately adjust the ammoniacal nitrogen load in the biological treatment tank 10. An example of a water treatment device with such a configuration is shown in Figure 2.

[0049] A water treatment device 2 shown in FIG. 2 is an example of a nitrification treatment device that controls the flow rate of the water to be treated based on the values ​​of the ammonia nitrogen concentrations of the water to be treated and the biologically treated water.

[0050] The water treatment device 2 includes, in addition to the configuration of the water treatment device 1 in FIG. 1, a treatment target water tank 30 upstream of the biological treatment tank 10 for storing treatment target water.

[0051] In the water treatment device 2, a treated water pipe 32 is connected to a treated water inlet 34 of the treated water tank 30. A treated water outlet 36 of the treated water tank 30 and a treated water inlet 26 of the biological treatment tank 10 are connected by a treated water supply pipe 18 via a pump 16. A treated water pipe 20 is connected to a treated water outlet 28 of the biological treatment tank 10. An ammonia nitrogen concentration meter 14 is installed in the treated water tank 30 and the treated water pipe 20. An aeration device 22 that supplies oxygen-containing gas such as air is installed at the inner bottom of the biological treatment tank 10. A screen 24 is installed so as to surround the treated water outlet 28 of the biological treatment tank 10, so that the outflow of sludge and the like into the treated water can be suppressed. The ammonia nitrogen concentration meter 14 functions as a treated water ammonia nitrogen concentration measuring means for measuring the ammonia nitrogen concentration of the treated water, and a biological treatment water ammonia nitrogen concentration measuring means for measuring the ammonia nitrogen concentration of the biological treatment water.

[0052] The control device 12 is connected to an ammoniacal nitrogen concentration meter 14 and a pump 16 by wired or wireless electrical connections or the like.

[0053] The water to be treated that contains ammonia nitrogen is sent through the water to be treated piping 32 to the water to be treated tank 30 from the water to be treated inlet 34, and is stored therein, and then supplied from the water to be treated outlet 36 to the biological treatment tank 10 from the water to be treated inlet 26 by the pump 16 through the water to be treated supply piping 18. In the biological treatment tank 10, the water to be treated is mixed with autotrophic bacteria, and while an oxygen-containing gas such as air is supplied and diffused by the aeration device 22, the ammonia nitrogen contained in the water to be treated is nitrified by biological treatment (nitrification treatment) (nitrification step). The biologically treated water that has been subjected to nitrification treatment is discharged as treated water from the treated water outlet 28 through the treated water piping 20. The treated water discharged from the treated water piping 20 may be sent to a downstream anaerobic tank (denitrification tank) not shown.

[0054] In the water treatment device 2, the water to be treated containing ammonia nitrogen is continuously supplied to the biological treatment tank 10 by the pump 16 (water to be treated supply step), and nitrification is performed in the biological treatment tank 10 (nitrification step). For example, the ammonia nitrogen concentration of the water to be treated is measured by the ammonia nitrogen concentration meter 14 in the water to be treated tank 30 (ammonia nitrogen concentration measurement step of the water to be treated), and the ammonia nitrogen concentration of the biological treatment water is measured by the ammonia nitrogen concentration meter 14 in the treated water pipe 20 (ammonia nitrogen concentration measurement step of the biological treatment water), and based on the measured ammonia nitrogen concentration of the water to be treated, the flow rate of the water to be treated flowing into the biological treatment tank 10 is automatically controlled by the control device 12 so that the measured ammonia nitrogen concentration of the biological treatment water is kept below a set value (flow rate control step). The ammonia nitrogen concentration of the water to be treated may be measured in the water to be treated tank 30 that stores the water to be treated, or may be measured in the water to be treated supply pipe 18. The ammonia nitrogen concentration of the biological treatment water may be measured in the biological treatment tank 10, or may be measured in the treated water pipe 20.

[0055] The ammoniacal nitrogen concentration meter for measuring the ammoniacal nitrogen concentration of the water to be treated is not particularly limited as long as it is capable of online measurement, but is particularly preferably a coulometric titration type ammoniacal nitrogen meter. The ammoniacal nitrogen concentration meter for measuring the ammoniacal nitrogen concentration of the water to be treated may be shared with an ammoniacal nitrogen concentration meter for measuring the ammoniacal nitrogen concentration of the biological treatment water, or may be separate. In addition, the ammoniacal nitrogen concentration meter for measuring the ammoniacal nitrogen concentration of the water to be treated may be a different type of ammoniacal nitrogen concentration meter from the ammoniacal nitrogen concentration meter for measuring the ammoniacal nitrogen concentration of the biological treatment water.

[0056] As a method of flow rate control by the control device 12, in order to precisely control the load on the biological treatment tank 10, it is preferable to control both the inverter control of the pump 16 and the opening adjustment of the valve provided in the treated water supply pipe 18. An example of a water treatment device having such a configuration is shown in Figure 3.

[0057] A water treatment device 3 shown in FIG. 3 is an example of a nitrification treatment device that controls the flow rate of water to be treated by controlling the opening and closing of pumps and valves.

[0058] In addition to the configuration of the water treatment device 1 in Figure 1, the water treatment device 3 further includes a treated water tank 30 for storing the treated water, located upstream of the biological treatment tank 10, a valve 38 whose opening can be adjusted to branch the flow path of the treated water from the treated water tank 30 to the biological treatment tank 10 and the treated water tank 30, and a flow meter 40 as a treated water flow rate measuring means for measuring the flow rate of the treated water in the biological treatment tank 10.

[0059] In the water treatment device 3, a treated water pipe 32 is connected to a treated water inlet 34 of the treated water tank 30. A treated water outlet 36 of the treated water tank 30 and a treated water inlet 26 of the biological treatment tank 10 are connected by a treated water supply pipe 18 via a pump 16, a valve 38, and a flow meter 40. A treated water pipe 20 is connected to a treated water outlet 28 of the biological treatment tank 10. A circulation pipe 42 branched from the treated water supply pipe 18 by a valve 38 is connected to the treated water pipe 32. An ammonia nitrogen concentration meter 14 is installed in the treated water tank 30 and the biological treatment tank 10. An aeration device 22 that supplies oxygen-containing gas such as air is installed at the inner bottom of the biological treatment tank 10. A screen 24 is installed to surround the treated water outlet 28 of the biological treatment tank 10, so that the outflow of sludge and the like into the treated water can be suppressed. The ammoniacal nitrogen concentration meter 14 functions as a treated water ammoniacal nitrogen concentration measuring means for measuring the ammoniacal nitrogen concentration of the treated water, and as a biologically treated water ammoniacal nitrogen concentration measuring means for measuring the ammoniacal nitrogen concentration of the biologically treated water.

[0060] The control device 12 is connected to the ammoniacal nitrogen concentration meter 14, the pump 16, the valve 38, and the flow meter 40 by wired or wireless electrical connections, etc.

[0061] The water to be treated that contains ammonia nitrogen is sent through the water to be treated piping 32 to the water to be treated tank 30 from the water to be treated inlet 34, and is stored therein, and then supplied from the water to be treated outlet 36 to the biological treatment tank 10 from the water to be treated inlet 26 by the pump 16 through the water to be treated supply piping 18. In the biological treatment tank 10, the water to be treated is mixed with autotrophic bacteria, and while an oxygen-containing gas such as air is supplied and diffused by the aeration device 22, the ammonia nitrogen contained in the water to be treated is nitrified by biological treatment (nitrification treatment) (nitrification step). The biologically treated water that has been subjected to nitrification treatment is discharged as treated water from the treated water outlet 28 through the treated water piping 20. The treated water discharged from the treated water piping 20 may be sent to a downstream anaerobic tank (denitrification tank) not shown.

[0062] In the water treatment device 3, the water to be treated containing ammonia nitrogen is continuously supplied to the biological treatment tank 10 by the pump 16 (water to be treated supply step), and nitrification is performed in the biological treatment tank 10 (nitrification step). For example, the ammonia nitrogen concentration of the water to be treated is measured by the ammonia nitrogen concentration meter 14 in the water to be treated tank 30 (ammonia nitrogen concentration measurement step of the water to be treated), and the ammonia nitrogen concentration of the biological treatment water is measured by the ammonia nitrogen concentration meter 14 in the biological treatment tank 10 (ammonia nitrogen concentration measurement step of the biological treatment water), and the flow rate of the water to be treated flowing into the biological treatment tank 10 is controlled by the control device 12 based on the measured ammonia nitrogen concentration of the water to be treated so that the measured ammonia nitrogen concentration of the biological treatment water is kept below a set value (flow rate control step). The ammonia nitrogen concentration of the water to be treated may be measured in the water to be treated tank 30 that stores the water to be treated, or may be measured in the water to be treated supply pipe 18. The ammonia nitrogen concentration of the biological treatment water may be measured in the biological treatment tank 10, or may be measured in the treated water pipe 20.

[0063] The control device 12 controls the flow rate of the water to be treated flowing into the biological treatment tank 10 by controlling the inverter of the pump 16 and the opening of the valve 38 .

[0064] The ammonia nitrogen concentration is measured by measuring the ammonia nitrogen concentration in the water to be treated or the biologically treated water, but it may also be measured by measuring the ammonia nitrogen concentration in the biologically treated water, which is the filtrate obtained by solid-liquid separation using a filtration device. By measuring the ammonia nitrogen concentration in the biologically treated water obtained by solid-liquid separation using a filtration device, it is possible to accurately measure even low concentrations. By removing SS components and the like from the biologically treated water by filtration, it is possible to reduce the frequency of maintenance of the ammonia nitrogen concentration meter. An example of a water treatment device with such a configuration is shown in Figure 4.

[0065] A water treatment device 4 shown in FIG. 4 is an outline of an example of a nitrification treatment device that uses a filtration device and a carrier.

[0066] The water treatment device 4 includes a filtration device 44 as a filtering means for filtering the biologically treated water, in addition to the configuration of the water treatment device 1 in FIG.

[0067] In the water treatment device 4, a treated water supply pipe 18 is connected to a treated water inlet 26 of the biological treatment tank 10 via a pump 16. A treated water pipe 20 is connected to a treated water outlet 28 of the biological treatment tank 10. A filtered treated water pipe 48 branched from the treated water pipe 20 is connected to an inlet of a filtration device 44, and a filtered treated water pipe 50 is connected to an outlet of the filtration device 44. An ammonia nitrogen concentration meter 14 is installed in the filtered treated water pipe 50. A carrier 46 carrying microorganisms is accommodated inside the biological treatment tank 10, and an aeration device 22 for supplying oxygen-containing gas such as air is installed at the bottom of the tank. A screen 24 is installed to surround the treated water outlet 28 of the biological treatment tank 10, so that the outflow of the carrier 46, sludge, etc. into the treated water can be suppressed.

[0068] The control device 12 is connected to an ammoniacal nitrogen concentration meter 14 and a pump 16 by wired or wireless electrical connections or the like.

[0069] The water to be treated that contains ammonia nitrogen is supplied by a pump 16 through a water to be treated supply pipe 18 and from a water to be treated inlet 26 to a biological treatment tank 10. In the biological treatment tank 10, the water to be treated is mixed with a carrier 46 carrying microorganisms, and while an oxygen-containing gas such as air is supplied and diffused by an aeration device 22, the ammonia nitrogen contained in the water to be treated is nitrified by biological treatment (nitrification treatment) (nitrification step). The biologically treated water that has been subjected to nitrification treatment is discharged as treated water from a treated water outlet 28 through a treated water pipe 20. The treated water discharged from the treated water pipe 20 may be sent to a downstream anaerobic tank (denitrification tank) not shown.

[0070] In the water treatment device 4, the water to be treated containing ammonia nitrogen is continuously supplied to the biological treatment tank 10 by the pump 16 (water to be treated supply step), and nitrification is carried out in the biological treatment tank 10 (nitrification step). A part of the biological treatment water that has been nitrified is sent as filtered water to the filtration device 44 through the filtered water to be treated pipe 48, and is filtered in the filtration device 44 (filtration step). The filtered biological treatment water is discharged as filtered water through the filtered water pipe 50. For example, the ammonia nitrogen concentration of the biological treatment water after filtration is measured by the ammonia nitrogen concentration meter 14 in the filtered water pipe 50 (biological treatment water ammonia nitrogen concentration measurement step), and the flow rate of the water to be treated flowing into the biological treatment tank 10 is automatically controlled by the control device 12 so that the measured ammonia nitrogen concentration of the biological treatment water is kept below a set value (flow rate control step). The ammonia nitrogen concentration of the biologically treated water after filtration may be measured in the filtered water piping 50, or may be measured in a filtered water storage tank that stores the filtered water.

[0071] (Specific example of control method by the control device) The control device 12 automatically controls the flow rate of the water to be treated so that the measurement result of the ammoniacal nitrogen concentration becomes equal to or less than the set ammoniacal nitrogen concentration value. A specific example of a control method by the control device 12 is shown below.

[0072] For example, two set values ​​of a large and a small ammonia nitrogen concentration are set in advance, the ammonia nitrogen concentration of the biological treatment water is measured, and if the measurement result is equal to or less than the smaller set value, the flow rate of the water to be treated is increased, if the measurement result of the ammonia nitrogen concentration is between the large and small set values, the flow rate of the water to be treated is maintained, and if the measurement result of the ammonia nitrogen concentration is equal to or more than the larger set value, the flow rate of the water to be treated is decreased. Figure 5 shows an example of a control flow by such a control device 12.

[0073] For example, two large and small set values ​​of ammonia nitrogen concentration (set value 1: the larger set value, set value 2: the smaller set value) and a maximum flow rate of the water to be treated are determined in advance, and the ammonia nitrogen concentration of the biological treatment water is measured by the ammonia nitrogen concentration meter 14 (S10). If the measurement result of the ammonia nitrogen concentration is equal to or greater than the larger set value (set value 1), the control device 12 reduces the flow rate of the water to be treated (S12). If the measurement result of the ammonia nitrogen concentration is less than the larger set value (set value 1) and the flow rate of the water to be treated is equal to or greater than the set maximum flow rate, the control device 12 maintains the flow rate of the water to be treated (S14). If the flow rate of the water to be treated is less than the set maximum flow rate and the measurement result of the ammonia nitrogen concentration is less than the larger set value (set value 1) and exceeds the smaller set value (set value 2), the control device 12 maintains the flow rate of the water to be treated (S14). If the measurement result of the ammonia nitrogen concentration is equal to or less than the smaller set value (set value 2) and a specified time or more has passed since the previous flow rate increase, the control device 12 increases the flow rate of the water to be treated (S16), and if a specified time or more has not passed since the previous flow rate increase, the control device 12 maintains the flow rate of the water to be treated (S14). By repeating this control even after the predetermined flow rate is reached, it is possible to maintain stable treatment.

[0074] This keeps the ammoniacal nitrogen concentration in the biological treatment tank 10 at or below the set value. Alternatively, two or more ammoniacal nitrogen concentrations may be set, and the rate of increase or decrease in the flow rate of the water to be treated may be changed depending on the value of the ammoniacal nitrogen concentration in the biological treatment tank 10. The increase or decrease in the flow rate of the water to be treated may also be determined by comparing with the result of a previous measurement of the ammoniacal nitrogen concentration. The measurement frequency of the ammoniacal nitrogen concentration can be set at will, but it is preferable to perform the measurement at least once within the retention time.

[0075] In general, the maximum set value is in the range of 1 to 10 mg / L of ammoniacal nitrogen concentration, and is preferably 1 mg / L or less. When controlling with two set values ​​of ammoniacal nitrogen concentration, large and small, set value 1 (the larger set value) may be, for example, in the range of 1 to 10 mg / L, and set value 2 (the smaller set value) may be, for example, in the range of 0.3 to 1 mg / L.

[0076] In controlling the load on the biological treatment tank 10 to be increased, there is no particular limit to the rate of increase per time, but from the standpoint of microbial growth and the like, it is preferable to adjust the rate to within the range of about 0.05 to 20%.

[0077] When the flow rate of the water to be treated is increased, it may take some time for the ammonia nitrogen concentration in the biological treatment water to increase. Therefore, it is better to increase the flow rate of the water to be treated again at an interval from the previous increase in the flow rate, for example, by waiting a specified time of 30 minutes or more.

[0078] The increase in the flow rate of the water to be treated may be adjusted according to the load condition of the biological treatment tank 10. For example, 3 d)), the rate of increase in the flow rate of the water to be treated is increased, and a high load (for example, 0.5 to 1.0 kg-N / (m 3 In the case of d), the rate of increase in the flow rate of the water to be treated may be decreased.

[0079] The increase in the flow rate of the water to be treated may also be adjusted based on the measured value of the ammoniacal nitrogen concentration in the biologically treated water.

[0080] In the control for lowering the load, the flow rate to be reduced each time is not particularly limited, but it is preferable to adjust the flow rate to be equal to or lower than the flow rate before the last time the flow rate was increased.

[0081] In addition, since it is important to maintain the ammoniacal nitrogen concentration in the biologically treated water at or below a set value, it is preferable to perform the control to reduce the flow rate with as little interval as possible.

[0082] The amount of nutrients added to the biological treatment tank 10 and the denitrification tank downstream of the biological treatment tank 10 may be adjusted in accordance with the control of the flow rate of the water to be treated. For example, the control device 12 may automatically control the amount of nutrients added to the biological treatment tank 10 and the denitrification tank downstream of the biological treatment tank 10 in accordance with the set ammonia nitrogen load. The control device 12 may automatically control the amount of nutrients added to the biological treatment tank 10 and the denitrification tank by controlling, for example, a pump, a valve, or the like provided in a nutrient supply pipe that supplies nutrients to the biological treatment tank 10 and the denitrification tank as a nutrient supply means. The control device 12 may also automatically control the amount of hydrogen donor added to the denitrification tank by controlling a pump, a valve, or the like provided in a hydrogen supply pipe that supplies a hydrogen donor to the denitrification tank.

[0083] Examples of nutrients include essential nutrients such as nitrogen (N) and phosphorus (P), as well as trace elements such as sulfur (S), potassium (K), sodium (Na), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), and molybdenum (Mo). Examples of hydrogen donors include, but are not limited to, one or more selected from alcohols such as methanol, ethanol, and isopropyl alcohol, organic acids such as acetic acid, hydrogen gas, acetone, glucose, ethyl methyl ketone, and tetramethylammonium hydroxide (TMAH). All hydrogen donors known in the art can be used.

[0084] The biological treatment tank 10 is not limited to one that performs only nitrification, and may perform both nitrification and denitrification. There are no particular limitations on the type of biological treatment tank 10, but it is preferable to use a biofilm system that retains as many nitrifying bacteria as possible in the tank and does not require a settling tank.

[0085] In the biofilm method, nitrifying bacteria attached to the carrier and nitrifying bacteria floating in the bulk water perform nitrification, but if a large amount of ammonia nitrogen remains in the tank, the toxicity of free ammonia causes an increase in the number of nitrifying bacteria to detach from the carrier. The nitrifying bacteria that have detached from the carrier are more likely to die from the toxicity of free ammonia than those on the biofilm. For this reason, in the biofilm method, it is best to keep the ammonia concentration in the tank low. Also, in the case of new carriers that do not have nitrifying bacteria attached, the bacteria are likely to detach from the carrier in the early stages of cultivation, so it is particularly preferable to keep the ammonia concentration in the tank low.

[0086] The carrier on which the microorganism is supported is not particularly limited as long as it is a carrier that has been conventionally used under aerobic conditions. Examples of the carrier include plastic carriers, sponge-like carriers, gel-like carriers, etc., and sponge-like carriers are preferred because they have a good balance between cost and durability.

[0087] It is preferable to install a separating means such as a screen 24 in the biological treatment tank 10 and separate the carriers and the like before carrying out treatment.

[0088] In the biological treatment process, from the viewpoint of growing microorganisms, the pH in the biological treatment tank 10 is preferably adjusted to a range of, for example, pH 6 to 8, and more preferably adjusted to a range of pH 6.8 to 7.2 in order to suppress inhibition by free ammonia.

[0089] Biological treatment is preferably carried out under aerobic conditions. For example, it is preferable to install an aeration device 22 in the biological treatment tank 10 and supply oxygen so that the dissolved oxygen concentration in the biological treatment tank 10 is, for example, 0.5 mg / L or more, preferably 1 mg / L or more.

[0090] The water temperature in the biological treatment tank 10 may be maintained in the range of 15 to 40°C, for example.

[0091] The water to be treated may be, for example, nitrogen-containing wastewater discharged from a semiconductor manufacturing process, etc. When the water to be treated contains calcium of 100 mg / L or more, preferably in the range of 100 to 1000 mg / L, the water treatment method and water treatment device according to the present embodiment can be suitably applied. EXAMPLES

[0092] EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0093] <Example 1> Using a water treatment device (nitrification treatment device) that uses the carrier shown in Figure 4, the target ammonia nitrogen load was reduced to 0.8 kg-N / (m 3 d) A continuous water flow test was carried out using simulated wastewater under the following test conditions.

[0094] The water treatment equipment was filled with new carriers so that the filling rate was 40% of the biological treatment tank (bulk volume / tank volume), seed sludge was added so that the MLSS was 3000 mg / L, and 0.4 kg-N / (m 3 After the reactor was started up to the tank volume·d, the biologically treated water was filtered through a filtration device, and the ammoniacal nitrogen concentration of the biologically treated water was measured using an ammoniacal nitrogen concentration meter, and control was started using the control device. A coulometric ammoniacal nitrogen meter (manufactured by Central Scientific) was used as the ammoniacal nitrogen concentration meter.

[0095] The ammonia nitrogen concentration of the treated water was measured every 30 minutes, and the control device was used to control the concentration so that it was within the set range of ammonia nitrogen concentration. When the load was increased, the flow rate of the water being treated was increased once every two hours, and when the load was decreased, the flow rate of the water being treated was decreased on the spot.

[0096] [Test conditions] Biological treatment tank volume: 9.8L Microorganism retention carrier: Hydrophobic polyurethane sponge carrier Carrier filling rate: 40% (bulk volume / tank volume) Temperature: 25℃ pH: 7.0~7.5 Test water: Well water to which ammonium chloride was added in an amount equivalent to an ammonium nitrogen concentration of 150 mg / L, and sodium carbonate, phosphoric acid and trace element solutions were also added to prepare simulated wastewater.

[0097] [Test Results] <Comparative Example> The load was set to be increased when the ammonia nitrogen concentration in the biologically treated water fell below 1 mg / L, and water flow was started. The ammonia nitrogen volume load [kg-N / (m 3 The change in the ammonia nitrogen concentration [mg / L] of the biological treatment water is shown in Figure 6. On the 10th day after the start of water supply, the ammonia nitrogen concentration was about 0.7 kg-N / (m 3 -tank volume·d), but thereafter, the ammonia nitrogen concentration of the biological treatment water did not fall below 1 mg / L, and on the 13th day the ammonia nitrogen concentration of the biological treatment water rose and the treatment performance did not stabilize. Furthermore, from the 14th day, the load was reduced once until the ammonia nitrogen concentration of the biological treatment water fell below 1 mg / L, and then the load was increased again under the same conditions, but the ammonia nitrogen concentration of the biological treatment water increased and the treatment performance did not stabilize. The flow rate of the water to be treated was reduced until the load was such that the ammonia nitrogen concentration of the biological treatment water fell below 1 mg / L, but ultimately the load was reduced to approximately 0.1 kg-N / (m 3 -The load was reduced to the tank volume x d.

[0098] <Example> When the ammonia nitrogen concentration of the biological treatment water was 0.5 mg / L (set value 2) or less, the flow rate of the water to be treated was increased, when the ammonia nitrogen concentration of the biological treatment water was less than 0.5 mg / L (set value 2) and exceeded 1.0 mg / L (set value 1), the flow rate of the water to be treated was maintained, and when the ammonia nitrogen concentration of the biological treatment water was 1.0 mg / L (set value 1) or more, the flow rate of the water to be treated was decreased, and water flow was started. The ammonia nitrogen volume load [kg-N / (m 3The change in the ammonia nitrogen concentration [mg / L] of the biological treatment water is shown in Figure 7. After 15 days of water supply, the concentration was about 0.8 kg-N / (m 3 Although the load reached the tank volume·d, the treatment performance remained stable.

[0099] Based on this, it was confirmed that when starting up a nitrification treatment device, the ammonia nitrogen concentration in the biological treatment tank or in the biological treatment water is measured, the flow rate of the water to be treated flowing into the biological treatment tank is controlled so that the ammonia nitrogen concentration is maintained below a set value, and the ammonia nitrogen volume load is adjusted, thereby making it possible to obtain more stable treated water quality even in high-load treatment.

[0100] In this way, it was found that the water treatment equipment and water treatment method of the embodiment can reduce the manpower required for starting up the equipment in water treatment in which the water to be treated containing ammonia nitrogen is nitrified by biological treatment, and can automatically start up the equipment and restore nitrification activity. [Explanation of symbols]

[0101] 1,2,3,4 Water treatment device, 10 Biological treatment tank, 12 Control device, 14 Ammonia nitrogen concentration meter, 16 Pump, 18 Treated water supply piping, 20 Treated water piping, 22 Aeration device, 24 Screen, 26,34 Treated water inlet, 28 Treated water outlet, 30 Treated water tank, 32 Treated water piping, 36 Treated water outlet, 38 Valve, 40 Flow meter, 42 Circulation piping, 44 Filtration device, 46 Carrier, 48 Filtered treated water piping, 50 Filtered treated water piping.

Claims

1. A water treatment device that nitrifies water to be treated that contains ammonia nitrogen under aerobic conditions by biological treatment, a biological treatment tank in which the water to be treated is mixed with autotrophic bacteria to nitrify the water; A supply means for continuously supplying the water to be treated to the biological treatment tank; A biological treatment water ammonia nitrogen concentration measuring means for measuring the ammonia nitrogen concentration of the biological treatment water obtained by the nitrification; A control means for automatically controlling the flow rate of the water to be treated flowing into the biological treatment tank so as to maintain the ammonia nitrogen concentration of the biological treatment water at a set value or less; A water treatment device comprising:

2. The water treatment device according to claim 1, The method further includes a means for measuring the ammonia nitrogen concentration of the water to be treated, The control means controls the flow rate of the water to be treated flowing into the biological treatment tank based on the ammonia nitrogen concentration of the water to be treated so as to maintain the ammonia nitrogen concentration of the biological treatment water below a set value.

3. The water treatment device according to claim 1 or 2, Further comprising a filtering means for filtering the biologically treated water, The water treatment device, wherein the biological treatment water ammonia nitrogen concentration measuring means measures the ammonia nitrogen concentration of the biological treatment water filtered by the filtering means.

4. The water treatment device according to any one of claims 1 to 3, The water treatment device is characterized in that, when the biological treatment water ammonia nitrogen concentration measuring means and the treatment water ammonia nitrogen concentration measuring means are provided, the treatment water ammonia nitrogen concentration measuring means is a coulometric titration type ammonia nitrogen meter.

5. The water treatment device according to any one of claims 1 to 4, The supply means includes a pump, The water treatment device, wherein the control unit controls an inverter of the pump to thereby control the flow rate of the water to be treated flowing into the biological treatment tank.

6. The water treatment device according to claim 5, A treated water tank for storing the treated water in a stage preceding the biological treatment tank; A valve capable of adjusting the opening degree, which can branch the flow path of the water to be treated from the water tank to the biological treatment tank and the water tank to be treated; Further equipped with The water treatment device, wherein the control unit controls the flow rate of the water to be treated flowing into the biological treatment tank by controlling an inverter of the pump and an opening degree of the valve.

7. The water treatment device according to any one of claims 1 to 6, The water treatment device according to claim 1, wherein the set value is an ammoniacal nitrogen concentration of 1 mg / L or less.

8. The water treatment device according to any one of claims 1 to 7, The water treatment device according to claim 1, wherein the control unit controls an amount of nutrients to be added to the biological treatment tank based on an amount of ammoniacal nitrogen load.

9. The water treatment device according to any one of claims 1 to 8, 13. A water treatment device, comprising: a water treatment apparatus for treating a water containing calcium of 100 mg / L or more;

10. A water treatment method for nitrifying water containing ammonia nitrogen under aerobic conditions by biological treatment, comprising: A water treatment method comprising the steps of continuously supplying the treated water to a biological treatment tank for mixing the treated water with autotrophic bacteria for nitrification, and automatically controlling the flow rate of the treated water flowing into the biological treatment tank so that the ammonia nitrogen concentration of the biological treatment water obtained by the nitrification is kept below a set value.

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