Water treatment apparatus and water treatment method

Abstract

To provide a water treatment apparatus and a water treatment method which can progress nitrification and denitrification sufficiently in 1 cycle and optimize treatment efficiency in a water treatment where a nitrogen component in water to be treated is subjected to intermittent aeration treatment.SOLUTION: To solve the problem in a water treatment for removing a nitrogen component in water to be treated by intermittent aeration operation, presented herein are: a water treatment apparatus and a water treatment method using the apparatus thereof for controlling an operation concerning a discharge mechanism of a treatment tank and / or a time to input water to be treated to the treatment tank in a processing time in a predetermined 1 cycle and on the basis of the measured results of a nitrate nitrogen concentration or an ammonia nitrogen concentration, wherein an operation relating to agitation during aeration and terminated aeration is set to 1 cycle. According to the present invention, especially sufficient progressing of nitrification, discharge of an untreated nitrogen component to the outside of the treatment tank and continuous treatment while untreated nitrogen components are remaining are suppressed, and the optimization of treatment efficiency concerning intermittent aeration treatment is enabled.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a water treatment device and a water treatment method, and more particularly to a water treatment device and a water treatment method involved in a nitrification / denitrification process of nitrogen components in water to be treated. [Background technology]

[0002] Various treatment methods for wastewater treatment are known, and the treatment method is selected according to the components to be removed from the wastewater. For example, a nitrification / denitrification process is one of the treatment methods when the wastewater contains nitrogen components as the components to be removed.

[0003] An example of such a nitrification / denitrification process is a biological nitrification / denitrification process that uses activated sludge to reduce nitrogen components in the treated water to nitrogen gas. This biological nitrification / denitrification process using activated sludge is known as a process that includes a nitrification process in which ammonia nitrogen is nitrified to nitrate nitrogen and nitrite nitrogen by nitrifying bacteria under aerobic conditions, and a denitrification process in which nitrate nitrogen and nitrite nitrogen are reduced to nitrogen gas by denitrifying bacteria under anaerobic conditions.

[0004] One known biological nitrification / denitrification process is the intermittent aeration process, in which the nitrogen-containing water being treated is aerated and then stopped, forming one cycle of a nitrification process under aerobic conditions and a denitrification process under anaerobic conditions.

[0005] For example, Patent Document 1 describes a nitrification / denitrification process for nitrogen-containing water to be treated that uses intermittent aeration. Patent Document 1 also describes that the pH in a reaction tank where intermittent aeration is performed is measured over time, and when the difference between the maximum and minimum pH values ​​in one cycle of the intermittent aeration process falls below a predetermined value, the amount of water to be treated to the reaction tank is reduced. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2008-36558 A Summary of the Invention [Problem to be solved by the invention]

[0007] It is known that the water treatment device used for the intermittent aeration treatment as described in Patent Document 1 can perform treatment within one tank and can easily be made compact. For this reason, water treatment using the intermittent aeration treatment is widely used to treat water containing nitrogen components.

[0008] In addition, water treatment using intermittent aeration involves two stages of treatment, a nitrification process under aerobic conditions and a denitrification process under anaerobic conditions, performed by aeration and then stopping aeration in one tank, and so operational management of the treatment processes is important. For this reason, it is necessary to grasp the treatment status related to the progress of the nitrification and denitrification processes and to control them to maintain stable operation.

[0009] In Patent Document 1, pH is used as an index to grasp the treatment state in the intermittent aeration treatment. However, when pH is used as an index, the treatment state of the water to be treated is indirectly evaluated, so it cannot be said that the operation control in the intermittent aeration treatment is sufficiently optimized.

[0010] In addition, in the intermittent aeration process, the processes related to nitrification and denitrification are not switched instantly, and in addition to nitrification and denitrification, organic matter decomposition also occurs. The inventors measured the nitrate nitrogen concentration and ammonia nitrogen concentration in the intermittent aeration process and visualized the behavior of nitrogen during the intermittent aeration process, and found that the process related to organic matter decomposition becomes dominant (has a fast processing speed) over the process related to nitrification, and thus the process may continue without sufficient nitrification progressing within one cycle. Therefore, in order to improve the treatment efficiency of the water to be treated in the intermittent aeration process, it is necessary not only to directly grasp the treatment state of the water to be treated, but also to appropriately select and control the operation contents to be controlled so that sufficient nitrification and denitrification processes can be performed within one cycle.

[0011] The object of the present invention is to provide a water treatment apparatus and a water treatment method that can sufficiently advance nitrification and denitrification within one cycle and optimize treatment efficiency in water treatment that involves intermittent aeration of nitrogen components in the water to be treated. [Means for solving the problem]

[0012] As a result of extensive research into the above-mentioned problems, the present inventors have found that in an intermittent aeration process in which aeration and stirring with aeration stopped are repeated, the nitrate nitrogen concentration and / or ammoniacal nitrogen concentration are measured during one predetermined treatment cycle, and specific operation details are controlled based on the measurement results, thereby allowing nitrification and denitrification to proceed sufficiently within one cycle and optimizing treatment efficiency, and have completed the present invention. That is, the present invention provides the following water treatment device and water treatment method.

[0013] In order to solve the above problems, the water treatment device of the present invention is a water treatment device that removes nitrogen components from the water to be treated by intermittent aeration operation, and is characterized in that one cycle is an operation involving aeration and stirring while aeration is stopped, and the operation relating to the discharge mechanism of the treatment tank is controlled based on the measurement results of the nitrate nitrogen concentration or ammonia nitrogen concentration during a predetermined treatment time of one cycle. Conventionally, in water treatment devices using intermittent aeration treatment, fluctuations in the water level occur after aeration begins, and a portion of the treated water is discharged outside the treatment tank. However, the present inventors have discovered that at this time, ammoniacal nitrogen that has not been sufficiently nitrified is discharged. On the other hand, according to the water treatment device of the present invention, by using the measurement results of the nitrate nitrogen concentration or ammonia nitrogen concentration, the behavior of nitrogen in the water to be treated can be directly grasped, and further, based on these measurement results, the discharge of the water to be treated (treated water) from the treatment tank can be controlled, thereby preventing the discharge of insufficiently treated water (treated water) from the treatment tank during aeration, thereby optimizing the treatment efficiency related to the intermittent aeration treatment.

[0014] In order to solve the above problems, the water treatment device of the present invention is a water treatment device that removes nitrogen components in the water to be treated by intermittent aeration operation, and is characterized in that one cycle is an operation involving aeration and stirring while aeration is stopped, and the time involved in introducing the water to be treated into the treatment tank is controlled based on the measurement results of the nitrate nitrogen concentration or ammonia nitrogen concentration during a predetermined treatment time of one cycle. Conventionally, in water treatment equipment using intermittent aeration treatment, water to be treated is introduced after aeration (nitrification process) and then the next process (denitrification process) begins. However, the inventors have discovered that of the nitrification and organic matter decomposition that proceed during aeration, organic matter decomposition is dominant (has a faster treatment rate), and nitrification continues even after aeration is stopped; and that if water to be treated is introduced when nitrification has not progressed sufficiently, the nitrification process will stop and ammoniacal nitrogen will remain in the treatment tank. On the other hand, according to the water treatment device of the present invention, the measurement results of the nitrate nitrogen concentration or ammonia nitrogen concentration are used to directly grasp the behavior of nitrogen in the water to be treated, and further, based on these measurement results, the time related to the introduction of the water to be treated (the timing of introducing the water to be treated) is controlled, thereby allowing nitrification to proceed sufficiently and preventing the treatment from continuing with untreated nitrogen components (ammonia nitrogen) remaining in the treatment tank, thereby optimizing the treatment efficiency related to the intermittent aeration treatment.

[0015] In order to solve the above problems, the water treatment device of the present invention is a water treatment device that removes nitrogen components in the water to be treated by intermittent aeration operation, and is characterized in that one cycle is an operation related to aeration and stirring while aeration is stopped, and during a predetermined treatment time of one cycle, the operation related to the discharge mechanism of the treatment tank and the time related to the introduction of the water to be treated into the treatment tank are controlled based on the measurement results of the nitrate nitrogen concentration or the ammonia nitrogen concentration. According to the water treatment device of the present invention, the measurement results of the nitrate nitrogen concentration are used to directly grasp the behavior of nitrogen in the water to be treated, and based on these measurement results, the time related to the discharge of the water to be treated (treated water) from the treatment tank and the introduction of the water to be treated (the timing of introducing the water to be treated) are controlled, thereby preventing insufficiently treated water (treated water) from being discharged out of the treatment tank during aeration, and preventing treatment from continuing with untreated nitrogen components (ammoniacal nitrogen) remaining in the treatment tank, thereby optimizing the treatment efficiency related to the intermittent aeration treatment.

[0016] Moreover, one embodiment of the water treatment device of the present invention is characterized in that the measurement results of the nitrate nitrogen concentration and the ammoniacal nitrogen concentration are used for control. This feature allows the behavior of nitrate nitrogen and ammonia nitrogen in the water to be treated to be directly understood, and the treatment state of the water to be treated can be accurately evaluated. In addition, by understanding the behavior of two types of nitrogen together and controlling based on this, the treatment efficiency of nitrification and denitrification in one cycle can be improved, and the progress of the treatment can be easily understood, enabling more accurate optimization as an intermittent aeration operation.

[0017] The water treatment method of the present invention for solving the above problems is a water treatment method for removing nitrogen components in the water to be treated by intermittent aeration operation, in which an operation relating to aeration and stirring while aeration is stopped is defined as one cycle, and the method is characterized in that it includes a control step for controlling the operation relating to the discharge mechanism of the treatment tank based on the measurement results of the nitrate nitrogen concentration or the ammonia nitrogen concentration during a predetermined treatment time of one cycle. According to the water treatment method of the present invention, by using the measurement results of nitrate nitrogen concentration or ammonia nitrogen concentration, the behavior of nitrogen in the water to be treated can be directly understood, and further, based on these measurement results, the discharge of the water to be treated (treated water) from the treatment tank can be controlled, thereby preventing the discharge of insufficiently treated water (treated water) from the treatment tank during aeration, thereby optimizing the treatment efficiency related to the intermittent aeration treatment.

[0018] The water treatment method of the present invention for solving the above problems is a water treatment method for removing nitrogen components in the water to be treated by intermittent aeration operation, in which an operation involving aeration and stirring while aeration is stopped is defined as one cycle, and the method is characterized in that it includes a control step for controlling the time involved in introducing the water to be treated into the treatment tank based on the measurement results of the nitrate nitrogen concentration or the ammonia nitrogen concentration during a predetermined treatment time of one cycle. According to the water treatment method of the present invention, the measurement results of the nitrate nitrogen concentration or ammonia nitrogen concentration are used to directly grasp the behavior of nitrogen in the water to be treated, and further, based on these measurement results, the time related to the introduction of the water to be treated (the timing of introducing the water to be treated) is controlled, thereby allowing nitrification to proceed sufficiently and preventing the treatment from continuing with untreated nitrogen components (ammonia nitrogen) remaining in the treatment tank, thereby optimizing the treatment efficiency related to the intermittent aeration treatment. Effect of the Invention

[0019] According to the present invention, it is possible to provide a water treatment apparatus and a water treatment method that can sufficiently advance nitrification and denitrification within one cycle and optimize treatment efficiency in water treatment that involves intermittent aeration of nitrogen components in the water to be treated. [Brief description of the drawings]

[0020] [Figure 1] 1 is a schematic explanatory diagram showing a water treatment device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing the behavior of nitrogen in intermittent aeration treatment using a water treatment device that is a comparative example of the present invention, and the operation of the water treatment device. [Diagram 3] FIG. 2 is a schematic diagram showing an example of the measurement results (nitrogen behavior) by a measurement unit and control by a control unit in intermittent aeration treatment using the water treatment device of an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The water treatment device and the water treatment method of the present invention are used for treating water containing nitrogen components. In particular, the water treatment device and the water treatment method of the present invention are used for an intermittent aeration process, which is one of the biological nitrification and denitrification processes, in which the water containing nitrogen components is treated by performing aeration and a process related to stirring while aeration is stopped once each, as one cycle.

[0022] The water to be treated W in the present invention is not particularly limited as long as it contains organic matter and nitrogen components to be treated. Specific examples of such water to be treated include wastewater such as industrial wastewater and domestic wastewater. In particular, examples of the water to be treated W that contains ammonia nitrogen or nitrate nitrogen as nitrogen components include sewage and human waste.

[0023] Hereinafter, embodiments of the water treatment device and the water treatment method according to the present invention will be described in detail with reference to the drawings. The water treatment method according to the present invention is replaced with the following description of the structure and operation of the water treatment device. Furthermore, the structure of the water treatment device described in the embodiments is merely an example for explaining the water treatment device according to the present invention, and is not limited thereto.

[0024] [Implementation] (Water treatment equipment) FIG. 1 is a schematic diagram of a water treatment device 10 according to an embodiment of the present invention. 1, a water treatment device 10 according to this embodiment includes a treatment tank 1, an aeration device 2, an agitation device 3, a measurement unit 4 for grasping the nitrogen behavior in the treatment tank 1, and a control unit 7. A water feed adjustment unit 5 for adjusting the time related to the feeding of the water W to be treated is provided on a line L1 for feeding the water W to be treated into the treatment tank 1, and a discharge mechanism 6 for adjusting the discharge of the water W1 to be treated is provided on a line L2 for discharging the water W1 (or a part of the water W to be treated) from the treatment tank 1. In FIG. 1, the dashed arrows indicate connections that are controllable or inputtable.

[0025] In the water treatment device 10 of this embodiment, the water to be treated W containing nitrogen components that has been introduced into the treatment tank 1 is subjected to intermittent aeration treatment. As shown in Fig. 1, a treatment tank 1 is equipped with an aeration device 2 and an agitation device 3. In addition, activated sludge containing microbial cells such as nitrifying bacteria and denitrifying bacteria is placed in the treatment tank 1. In this treatment tank 1, an intermittent aeration operation is performed in which aeration by the aeration device 2 and agitation by the agitation device 3 are (apparently) repeated alternately, whereby the nitrogen components in the water to be treated W are treated. More specifically, by operating the aeration device 2 in the treatment tank 1, an aerobic (oxidizing) atmosphere is formed, and an oxidation reaction in which ammonia nitrogen is oxidized to nitrate nitrogen by nitrifying bacteria proceeds. It is preferable to also operate the agitation device 3 at this time. On the other hand, by stopping the aeration device 2 while the agitation device 3 is operating in the treatment tank 1, an anaerobic (reducing) atmosphere is formed, and a reduction reaction in which nitrate nitrogen is reduced to nitrogen gas by denitrifying bacteria proceeds. The treated water W1 treated in the treatment tank 1 is discharged to the outside of the system via a line L2. Nitrogen gas generated in the treatment tank 1 is discharged to the outside of the system via a line L3.

[0026] The aeration device 2 is for forming an aerobic atmosphere in the treatment tank 1. The aeration device 2 in this embodiment may be any device capable of supplying a necessary amount of gas such as air or oxygen into the treatment tank 1, and the specific structure is not particularly limited. As an example of the aeration device 2, as shown in FIG. 1, an aeration device in which an air diffuser 21 and a blower B are connected may be used. Here, examples of the air diffuser 21 include an air diffuser having a plurality of nozzles, a tubular member made of a porous material, and an air diffuser made of a tubular member or a plate-shaped member having a number of holes or slits. In addition, the blower B may be any device capable of compressing and sending gas, and examples of the blower include a blower and a compressor. As a result, gas is supplied into the treatment tank 1, the treatment tank 1 is made under an aerobic atmosphere, and the nitrification process (oxidation reaction) by the nitrifying bacteria can proceed.

[0027] The agitator 3 is for forming an anaerobic atmosphere in the treatment tank 1 by agitating the treatment tank 1 when the aeration device 2 is stopped. It is preferable that the agitator 3 is driven at all times during the treatment cycle, but it may be driven alternately with the aeration device 2. The agitation device 3 in this embodiment is not particularly limited in its specific structure as long as it can agitate the water W to be treated in the treatment tank 1 with the necessary strength. As an example of the agitation device 3, as shown in Fig. 1, there is one including an agitation blade 31, an agitation shaft 32 attached to the agitation blade 31, and a drive mechanism 33 for rotating the agitation blade 31. This allows the treatment tank 1 to be agitated, and the treatment tank 1 to be placed under an anaerobic atmosphere, allowing the denitrification step (reduction reaction) by the denitrifying bacteria to proceed. It should be noted that a structure other than the stirring blade may be used as the stirring device 3. Also, stirring may be performed by a drive mechanism other than rotation.

[0028] The location of the agitator 3 is not particularly limited. As shown in Fig. 1, the agitator blade may be provided from the upper side of the treatment tank 1, or the agitator blade may be provided on the side wall side of the treatment tank 1 or on the bottom side of the treatment tank 1.

[0029] The measuring unit 4 is for grasping the nitrogen behavior in the treatment tank 1, and may be any unit capable of acquiring information related to the concentration fluctuations (information related to the change in concentration over time) of nitrate nitrogen or ammonia nitrogen in the treatment tank 1. It is preferable that the measuring unit 4 acquires information related to at least the concentration fluctuations (information related to the change in concentration over time) of nitrate nitrogen in the treatment tank 1. This makes it possible to accurately grasp the nitrogen behavior, particularly associated with nitrification, in the intermittent aeration treatment in the treatment tank 1, and to acquire parameters necessary for control in the control unit 7 described below.

[0030] 1, it is more preferable that the measuring unit 4 in this embodiment is provided with two types of sensors (a first sensor 4a and a second sensor 4b) so as to be able to measure both the nitrate nitrogen concentration and the ammoniacal nitrogen concentration in the water to be treated W. This makes it easier to grasp the progress of the intermittent aeration treatment, and improves the accuracy of calculations relating to the optimization conditions for the intermittent aeration operation in the control unit 7 described later.

[0031] The measurement unit 4 may be provided with the first sensor 4a and the second sensor 4b as known measuring instruments, respectively, as a nitrate nitrogen concentration meter and an ammonia nitrogen concentration meter, and the nitrate nitrogen concentration measurement by the first sensor 4a and the ammonia nitrogen concentration measurement by the second sensor 4b may be performed independently, or the nitrate nitrogen concentration and the ammonia nitrogen concentration values ​​may be obtained by using either a nitrate nitrogen concentration meter or an ammonia nitrogen concentration meter as the first sensor 4a and using a total nitrogen concentration meter as the second sensor 4b. Note that known measuring instruments capable of measuring the nitrate nitrogen concentration and the ammonia nitrogen concentration include measuring instruments equipped with ion electrodes. Moreover, it is preferable that the measurement unit 4 is capable of continuous measurement and automatic data transmission, which increases the accuracy of calculations in the control unit 7 (described later) and makes it easier to input data to the control unit 7.

[0032] The untreated water input adjusting unit 5 is for adjusting the time for inputting the untreated water W into the treatment tank 1. The untreated water input adjustment unit 5 in this embodiment may be any unit capable of adjusting the time at which the untreated water W is input from the line L1 (the timing at which the untreated water W is input) by the control unit 7 described later. The untreated water input adjustment unit 5 may also adjust the input amount of the untreated water W input into the treatment tank 1 in conjunction with the timing at which the untreated water W is input into the treatment tank 1. Examples of the treated water input adjustment section 5 include, for example, a flow control valve or valve, as shown in Figure 1, which can adjust the timing and amount of treated water W input by opening and closing operation and opening time, and a treated water transfer device equipped with inverter control.

[0033] The discharge mechanism 6 is for adjusting the discharge of treated water W1 discharged from the treatment tank 1 to the outside of the system via line L2. Here, "treated water W1" refers to the general solution discharged from the treatment tank 1 to the outside of the system, and includes untreated water W to be treated, in addition to water that has completely undergone intermittent aeration treatment. Furthermore, "adjustment of the discharge of treated water W1" refers to adjustment of the timing at which treated water W1 is discharged to the outside of the treatment tank 1, and / or adjustment of the discharge amount of treated water W1. The discharge mechanism 6 in this embodiment may be any mechanism capable of adjusting the discharge of the treated water W1 from the line L2 by the control unit 7 described later. Examples of the discharge mechanism 6 include a flow control valve or a valve, etc., that can be opened or closed to adjust the timing and amount of discharge of the treated water W1, provided on the line L2, as shown in Fig. 1, or an overflow weir provided on the treatment tank 1 side and a means (such as a movable weir or an overflow valve) for adjusting the outflow from the overflow weir to the line L2 side.

[0034] The control unit 7 is for controlling the intermittent aeration operation in the treatment tank 1. As shown in Figure 1, the control unit 7 in this embodiment is controllably connected to the treated water input adjustment unit 5 and discharge mechanism 6 that are the objects to be controlled, and is also connected so that the measurement results of the measurement unit 4 can be input.

[0035] The control unit 7 may be any unit capable of controlling or acquiring information about each component connected as a control target. As the control unit 7 in this embodiment, for example, as shown in FIG. 1, there is a unit including an information acquisition unit 71, a calculation unit 72, and an operation control unit 73.

[0036] The information acquiring section 71 acquires information relating to the measurement results in the measuring section 4. Further, the calculation unit 72 performs calculations related to the control of the intermittent aeration operation, such as the time for feeding the water to be treated W by the water to be treated feeding adjustment unit 5 related to the intermittent aeration operation and the time for discharging the treated water W1 by the discharge mechanism 6, based on the information acquired by the information acquisition unit 71. The calculations will be described later. Furthermore, the operation control unit 73 transmits a control signal based on the calculation result of the calculation unit 72 to each component connected as a controlled object.

[0037] The information acquisition unit 71, the calculation unit 72, and the operation control unit 73 constituting the control unit 7 may include manual operation by an operator, but it is preferable to use a computing device that has a data input / output function for acquiring information and executes a program for performing calculations related to control and transmitting control signals using a processor such as a CPU to enable automatic control. This makes it easy to optimize the intermittent aeration operation of the water treatment device 10.

[0038] (Control of intermittent aeration operation in water treatment equipment) Hereinafter, when using the water treatment device 10 of this embodiment to perform intermittent aeration treatment on water W containing nitrogen components, the water W to be treated, an example of suitable intermittent aeration operation control according to the nitrogen behavior in the water W to be treated will be described. Note that the explanations regarding each operation control are merely examples of the embodiment, and are not limited thereto.

[0039] Here, in the intermittent aeration operation of the present invention, a combination of aeration and stirring under aeration stop is defined as one cycle, and the order of aeration and stirring within the combination is not particularly limited. In this embodiment, for convenience of explanation of the calculation processing, one cycle is shown in which aeration is performed by the aeration device 2, then the aeration device 2 is stopped and stirring is performed by the stirring device 3, but this is not limited to this, and one cycle may be one in which stirring is performed by the stirring device 3 first and then aeration is performed by the aeration device 2. In addition, the time required for one cycle is determined in advance before the treatment, but it is not limited to a fixed value and may be determined each time the treatment is performed. For example, as a result of control related to the optimization of the intermittent aeration treatment using the water treatment device 10 in this embodiment, the time required for one cycle may be determined or changed.

[0040] First, a case where intermittent aeration operation is performed without control by the control unit 7 in the water treatment device 10 of this embodiment will be described as a comparative example for this embodiment. Here, of the configurations shown as the water treatment device 10 of this embodiment, one having a treatment tank 1, an aeration device 2, and an agitation device 3, and monitoring of nitrogen concentration by a measurement unit 4, is used as a water treatment device related to a control example.

[0041] FIG. 2 is a schematic diagram showing the behavior of nitrogen in intermittent aeration treatment using a water treatment device that is a comparative example of the present invention, and the operation of the water treatment device. More specifically, Fig. 2 shows the time-dependent changes in ammonia nitrogen concentration, nitrate nitrogen concentration, and dissolved oxygen concentration (DO) when the water to be treated W input into the water treatment device of the control example is subjected to a nitrification process (oxidation reaction) by driving the aeration device 2, and then to a denitrification process (reduction reaction) by driving the agitator 3. Fig. 2 also shows three cycles of treatment carried out continuously. Note that the dissolved oxygen concentration (DO) in Fig. 2 was measured to monitor the properties (treatment state) of the water to be treated W, and ORP may be measured instead. The two thin lines shown in FIG. 2 indicate the ammoniacal nitrogen concentration in the first cycle, the lower thin line indicates the ammoniacal nitrogen concentration at the end of the nitrification process, and the upper thin line indicates the ammoniacal nitrogen concentration at the end of the cycle.

[0042] As shown in FIG. 2, when the water to be treated W is aerated and the nitrification process is started, the ammoniacal nitrogen concentration decreases, and the DO and nitrate nitrogen concentrations increase. At this time, within a certain time from the start of aeration, the denitrification process, which is accompanied by organic matter decomposition, proceeds together with the nitrification process (corresponding to "nitrification + organic matter decomposition (parallel denitrification)" in FIG. 2). At the same time, as the aeration starts, the water level in the treatment tank 1 rises, and while the nitrification process and the denitrification process proceed simultaneously, a part of the water to be treated W is discharged outside the system as treated water W1 (treated water outflow section (white arrow) in FIG. 2). As shown in FIG. 2, the treated water W1 discharged in the treated water outflow section is discharged in a state in which nitrification has not progressed sufficiently, and a large amount of ammoniacal nitrogen remains. In this embodiment, "parallel denitrification" refers to a state in which the nitrified ammoniacal nitrogen is immediately denitrified. This occurs in a short period of time from the start of aeration until the transition to an aerobic state.

[0043] Then, while aeration by the aeration device 2 continues, the nitrification process and organic matter decomposition progress with an increase in DO (or ORP) (corresponding to "nitrification + organic matter decomposition" in Figure 2). At this time, organic matter decomposition, which has a fast processing rate (reaction rate), finishes first, and nitrification, which has a slow processing rate, continues even if the aeration device 2 is stopped (the ammonia nitrogen concentration continues to decrease).

[0044] After the aeration device 2 is stopped, the agitator 3 is operated, and new water to be treated W is added to the treatment tank 1 when the water level in the treatment tank 1 becomes stable. At that point, the nitrification process stops and the process moves to the denitrification process. However, as shown in Figure 2, because the treatment speed of the nitrification process is slow, the water to be treated W is added before the nitrification process reaches its peak. As a result, the process moves to the next process (denitrification process) with ammonia nitrogen remaining in the treatment tank 1 (nitrification is not completed). This results in a large amount of ammonia nitrogen to be treated in the next cycle.

[0045] After the new water to be treated W is added, the denitrification process (corresponding to "denitrification + organic matter decomposition" in Figure 2) begins using the organic matter in the added water to be treated W, and the ammoniacal nitrogen concentration in the water to be treated W in the treatment tank 1 increases and the organic matter concentration decreases, resulting in a neutral state (corresponding to "neutral time" in Figure 2) in which nitrification hardly progresses, and one cycle of intermittent aeration treatment is completed.

[0046] As can be seen from the relationship between the thin line (ammoniacal nitrogen concentration in the first cycle) in FIG. 2 and the ammoniacal nitrogen concentration at the end of the nitrification step in each cycle and at the end of one cycle, repeating this treatment cycle leads to a gradual increase (accumulation) of the ammoniacal nitrogen remaining in the treatment tank 1, resulting in a decrease in the treatment efficiency in the intermittent aeration treatment.

[0047] The inventors visualized the nitrogen behavior during intermittent aeration treatment as shown in Fig. 2, and found that after the start of aeration, water level fluctuations occurred and part of the water W to be treated was discharged outside the treatment tank 1, but at this time, ammoniacal nitrogen that was not sufficiently nitrified was discharged, and that of the nitrification and organic matter decomposition that proceed during aeration, organic matter decomposition was dominant (had a faster treatment speed), and nitrification continued even after aeration was stopped, and that if the water W to be treated was added in a state in which nitrification had not progressed sufficiently (was not completed), the nitrification process stopped and ammoniacal nitrogen remained in the treatment tank 1. In other words, the inventors concluded that in the water treatment device serving as the control example, treatment continued without sufficient nitrification and denitrification (especially nitrification) progressing within one cycle.

[0048] Furthermore, the intermittent aeration treatment (operation of the water treatment device 10) using the water treatment device 10 of this embodiment is based on the conclusions (knowledge) obtained from the above-mentioned comparison example, and appropriate selection and operation control are made regarding the operational contents to be controlled, thereby optimizing the treatment efficiency. More specifically, the water treatment device 10 of this embodiment directly grasps the nitrogen behavior in the water to be treated W by using the measurement results of the nitrate nitrogen concentration and / or ammonia nitrogen concentration by the measurement unit 4, and based on these measurement results, controls the control unit 7 to control the time for discharging the water to be treated (treated water) from the treatment tank 1 and / or the time for introducing the water to be treated (the timing for introducing the water to be treated).

[0049] FIG. 3 is a schematic diagram showing an example of the measurement results (nitrogen behavior) by the measurement unit 4 and the control by the control unit 7 in the intermittent aeration treatment using the water treatment device 10 of this embodiment. More specifically, Fig. 3 shows the time-dependent changes in ammoniacal nitrogen concentration, nitrate nitrogen concentration, and dissolved oxygen concentration (DO) when the control unit 7 controls the operation of the water to be treated input adjustment unit 5 and the discharge mechanism 6 in carrying out a nitrification process (oxidation reaction) by driving the aeration device 2 and then a denitrification process (reduction reaction) by driving the agitator 3 on water to be treated W fed into the treatment tank 1 of the water treatment device 10. As in Fig. 2, Fig. 3 also includes "nitrification + organic matter decomposition (parallel with denitrification)", "nitrification + organic matter decomposition", "denitrification + organic matter decomposition", and "neutral time" in one cycle. Fig. 3 shows three cycles of treatment carried out continuously. Note that the dissolved oxygen concentration (DO) in Fig. 3 was measured to monitor the properties (treatment state) of the water W to be treated, and the ORP may be measured instead.

[0050] The information acquisition unit 71 of the control unit 7 in the water treatment device 10 of this embodiment acquires information on the change over time of the nitrate nitrogen concentration or the ammoniacal nitrogen concentration in each process via the measurement unit 4. In particular, when acquiring information on the change over time of the nitrate nitrogen concentration, it is preferable to acquire information on the concentration fluctuation (rise or peak) of nitrate nitrogen, which allows the treatment state of the water W to be treated during the nitrification process or denitrification process, with high accuracy. This improves the accuracy of the operation control in the water treatment device 10, making it easier to optimize the treatment efficiency. In addition, the information on the change over time of the ammoniacal nitrogen concentration can also be used for monitoring whether nitrification is proceeding sufficiently.

[0051] In addition, the information acquired by the information acquisition unit 71 is not limited to either one of information based on the change over time in the nitrate nitrogen concentration or the ammoniacal nitrogen concentration, but may be information based on the change over time in both the nitrate nitrogen concentration and the ammoniacal nitrogen concentration. In the water treatment device 10 of this embodiment, it is preferable that the information acquisition unit 71 and the calculation unit 72 perform calculation processing using the values ​​of the ammoniacal nitrogen concentration and the nitrate nitrogen concentration. This makes it possible to obtain a more detailed understanding of the nitrogen behavior in the water W to be treated and optimize the intermittent aeration operation.

[0052] As shown in FIG. 3, the information acquisition unit 71 in this embodiment acquires information regarding the change over time in the nitrate nitrogen concentration and information regarding the change over time in the ammonia nitrogen concentration, and this information is input to the calculation unit 72.

[0053] Based on the information input from the information acquisition unit 71, the calculation unit 72 calculates the time for discharging the treated water W1 from the treatment tank 1 and / or the time for introducing the treated water W into the treatment tank 1 (the timing for introducing the treated water).

[0054] First, calculation of the time for discharging the treated water W1 from the treatment tank 1 will be illustrated. For example, the time when the nitrification process is deemed to have progressed to a certain extent after the start of aeration (the onset of nitrification) may be set as the time to discharge the treated water W1. More specifically, the onset of nitrification may be set as the time when the nitrate nitrogen concentration increases to a certain extent, such as when the nitrate nitrogen concentration reaches a specified value during aeration or when the difference in concentration fluctuation of the nitrate nitrogen concentration exceeds a predetermined value, or the onset of nitrification may be set as the time when the nitrate nitrogen concentration and the ammonia nitrogen concentration intersect during aeration. The time calculated here is used as a parameter for adjusting the discharge of the treated water W1 in the discharge mechanism 6.

[0055] Also, calculation of the time required for introducing the water W to be treated into the treatment tank 1 will be illustrated. For example, the time when the nitrification process is deemed to have progressed sufficiently after aeration is stopped (peak of nitrification) can be set as the time to add the water to be treated W. More specifically, the time when the nitrate nitrogen concentration reaches a maximum value or the ammonia nitrogen concentration falls to a predetermined value or below (detection limit) after aeration is stopped can be set as the peak of nitrification. The time calculated here is used as a parameter for adjusting the amount of water W fed to be treated in the water-to-be-treated input adjusting unit 5.

[0056] The operation control unit 73 transmits a control signal based on the calculation result of the calculation unit 72 to each controlled object (the treated water input adjustment unit 5 and the discharge mechanism 6). The control contents based on the control signal sent from the operation control unit 73 will be exemplified below.

[0057] The control over the discharge mechanism 6 may, for example, be to close the discharge mechanism 6 when aeration begins, and to open the discharge mechanism 6 at the time when the treated water W1 is discharged from the treatment tank 1 (at the start of nitrification). As a result, the treated water W is not discharged outside the system when aeration begins, and by opening the discharge mechanism 6 when the ammonia nitrogen concentration in the treated water W has decreased, it is possible to prevent the treated water W (treated water W1) that is not sufficiently treated from being discharged outside the treatment tank 1 during aeration, thereby optimizing the treatment efficiency related to the intermittent aeration process.

[0058] In addition, the control over the treated water input adjustment unit 5 may, for example, be controlled to open the treated water input adjustment unit 5 at the time when the treated water W is input to the treatment tank 1 (peak of nitrification), without being linked to the start and stop of aeration by the aeration device 2. As a result, by opening the treated water input adjustment section 5 at the timing when nitrification has progressed sufficiently, it is possible to prevent the treatment from continuing with untreated nitrogen components (ammoniacal nitrogen) remaining in the treatment tank 1 when transitioning from the nitrification process to the denitrification process, and to optimize the treatment efficiency of the intermittent aeration treatment.

[0059] As described above, in the description of the control by the control unit 7 based on FIG. 3, the measurement unit 4 has acquired measurement values ​​of both the nitrate nitrogen concentration and the ammonia nitrogen concentration, but the present invention is not limited to this. For example, the measurement unit 4 may measure either the nitrate nitrogen concentration or the ammonia nitrogen concentration, and an estimate of the other concentration that is not measured may be obtained by calculation or the like, and the control unit 7 may control based on the obtained measured value and estimate. More specifically, when the ammonia nitrogen concentration is measured, a calculation may be performed to obtain an estimate of the nitrate nitrogen concentration on the assumption that all ammonia nitrogen is converted to nitrate nitrogen by aeration, or a calculation may be performed to obtain an estimate by multiplying the ammonia nitrogen concentration by a correction coefficient related to the conversion. As another example, the measurement unit 4 measures either the nitrate nitrogen concentration or the ammoniacal nitrogen concentration, and the peak of nitrification is regarded as the point at which the nitrate nitrogen concentration reaches its maximum value or the ammoniacal nitrogen concentration reaches its minimum value (bottom value), and the onset of nitrification is regarded as the point at which the nitrate nitrogen concentration begins to be detected after the start of aeration or the point at which the ammoniacal nitrogen concentration is sufficiently reduced. In this way, in addition to obtaining information regarding the change over time of the concentration measured by the measurement unit 4, an estimate is made regarding the change over time of the concentration that is not measured, and control is performed in the control unit 7.

[0060] In this embodiment, the control by the control unit 7 uses the values ​​of the nitrate nitrogen concentration and ammonia nitrogen concentration in the intermittent aeration treatment to accurately grasp the nitrogen behavior and evaluate the treatment state of the water to be treated W, and then performs a predetermined operation control, and it is preferable to adjust other elements related to the intermittent aeration operation in addition to the timing of feeding the water to be treated W and the timing of discharging the treated water W1. For example, the amount of water to be treated W fed and the amount of water to be treated W1 discharged may be adjusted by adjusting the opening time of the water to be treated feeding adjustment unit 5 and the discharge mechanism 6.

[0061] In addition to the above-mentioned configuration, the water treatment device 10 in this embodiment may have a means for improving the treatment efficiency of the intermittent aeration treatment. Specifically, for example, a hydrogen donor adding section 8 may be provided in a water treatment device 10 as shown in Fig. 1. Here, the hydrogen donor adding section 8 is for adding a hydrogen donor to the water W to be treated in the treatment tank 1. In the reduction reaction in the denitrification process described above, hydrogen is required to proceed with the reaction. Normally, the BOD (organic matter) components in the water W to be treated function as the hydrogen donor, but there may be a shortage depending on the water quality and treatment status of the water W to be treated. For this reason, a hydrogen donor adding section 8 is provided and a hydrogen donor is added to the water W to be treated as necessary, thereby making it possible to efficiently proceed with the denitrification process.

[0062] There is no particular limitation on the structure of the hydrogen donor adding unit 8. For example, as shown in Fig. 1, in addition to a storage unit 81 for storing the hydrogen donor and a pipe 82 for adding the hydrogen donor to the treatment tank 1, an adjustment mechanism (not shown) may be provided on the pipe 82 for adjusting the amount of hydrogen donor added. In this case, examples of the adjustment mechanism include a flow rate adjustment valve and a pump. As the hydrogen donor, an easily decomposable organic matter may be used. Examples of such organic matter include alcohol, organic acids such as acetic acid, and waste liquid containing sugar. In particular, it is preferable to use methanol as the hydrogen donor, which also acts as a carbon source and an energy source for denitrifying bacteria. Furthermore, by using methanol as the hydrogen donor, it becomes easy to estimate (calculate) the effect on the denitrification process (reduction reaction) according to the added amount. The above-mentioned control unit 7 may control the added amount of the hydrogen donor added to the water W to be treated in the hydrogen donor adding unit 8. This makes it easy to perform optimization related to improving the treatment efficiency in the water treatment device 10 with higher accuracy.

[0063] It should be noted that the structure of the water treatment device 10 of this embodiment is not limited to that shown in FIG. For example, the water treatment device 10 may be provided with either one of the water input adjustment unit 5 and the discharge mechanism 6, and either one may be controlled by the control unit 7. This allows for simplification of the device, and also makes it possible to optimize the treatment efficiency of the intermittent aeration treatment according to the respective control contents.

[0064] As described above, the water treatment device of this embodiment and the water treatment method using this water treatment device relate to water treatment that removes nitrogen components in the water to be treated by intermittent aeration operation, in which an operation relating to aeration and stirring while aeration is stopped is considered as one cycle, and during a predetermined treatment time of one cycle, the operation relating to the discharge mechanism of the treatment tank and / or the time relating to the introduction of the water to be treated into the treatment tank are controlled based on the measurement results of the nitrate nitrogen concentration and / or the ammonia nitrogen concentration. According to this embodiment, by using the measurement results of the nitrate nitrogen concentration and / or ammonia nitrogen concentration, the behavior of nitrogen in the water to be treated can be directly grasped, and further, based on these measurement results, the time for discharging the water to be treated (treated water) from the treatment tank and / or the time for introducing the water to be treated (the timing for introducing the water to be treated) can be controlled, thereby preventing the water to be treated (treated water) that is not sufficiently treated from being discharged out of the treatment tank during aeration, and preventing the treatment from continuing with untreated nitrogen components (ammonia nitrogen) remaining in the treatment tank, thereby optimizing the treatment efficiency related to the intermittent aeration treatment.

[0065] The above-described embodiment shows an example of a water treatment device and a water treatment method. The water treatment device and the water treatment method according to the present invention are not limited to the above-described embodiment, and the water treatment device and the water treatment method according to the above-described embodiment may be modified without departing from the gist of the present invention.

[0066] The water treatment device of this embodiment is not limited to a device that performs treatment in one tank (single tank) as long as it performs intermittent aeration operation by repeating aeration and stirring while aeration is stopped. For example, it may perform intermittent aeration operation based on the control of this embodiment for multiple tanks. This makes it possible to increase the amount of water to be treated that can be treated within a given time, thereby improving the treatment efficiency.

[0067] In addition, the water treatment device and the water treatment method of this embodiment perform control using the measurement results of the nitrate nitrogen concentration and / or the ammonia nitrogen concentration, but when it is difficult to continuously measure each nitrogen concentration, the measurement results of DO or ORP may be used as an auxiliary. For example, in the operation control of the discharge mechanism 6, the point at which the DO or ORP reaches 30 to 50% of its peak value is regarded as the start of nitrification, and in the operation control of the water input adjustment unit 5, the point at which the DO or ORP falls 20 to 40% from its peak value is regarded as the peak of nitrification. [Industrial Applicability]

[0068] The water treatment apparatus and method of the present invention are preferably used for treating water containing nitrogen components, particularly in a nitrification / denitrification process in which nitrogen components in the water are removed by intermittent aeration. [Explanation of symbols]

[0069] 10 water treatment device, 1 treatment tank, 2 aeration device, 21 aeration body, 3 agitation device, 31 agitation blade, 32 agitation shaft, 33 drive mechanism, 4 measurement unit, 4a first sensor, 4b second sensor, 5 treated water input adjustment unit, 6 discharge mechanism, 7 control unit, 71 information acquisition unit, 72 calculation unit, 73 operation control unit, 8 hydrogen donor addition unit, 81 storage unit, 82 piping, B blower, L1 to L3 lines, W treated water, W1 treated water

Claims

1. A water treatment device that removes nitrogen components from water to be treated by intermittent aeration operation, A water treatment device characterized in that one cycle is an operation related to aeration and stirring while aeration is stopped, and the operation related to the discharge mechanism of the treatment tank is controlled based on the measurement results of nitrate nitrogen concentration or ammonia nitrogen concentration during a predetermined treatment time of one cycle.

2. A water treatment device that removes nitrogen components from water to be treated by intermittent aeration operation, A water treatment device characterized in that one cycle is an operation involving aeration and stirring while aeration is stopped, and that during a predetermined treatment time for one cycle, the time for feeding the water to be treated into the treatment tank is controlled based on the measurement results of nitrate nitrogen concentration or ammonia nitrogen concentration.

3. A water treatment device that removes nitrogen components from water to be treated by intermittent aeration operation, A water treatment device characterized in that one cycle is an operation related to aeration and stirring while aeration is stopped, and during a predetermined treatment time of one cycle, the device controls the operation related to the discharge mechanism of the treatment tank and the time related to the introduction of the water to be treated into the treatment tank based on the measurement results of nitrate nitrogen concentration or ammonia nitrogen concentration.

4. 4. The water treatment device according to claim 1, wherein the control is performed using results of measurements of nitrate nitrogen concentration and ammonia nitrogen concentration.

5. A water treatment method for removing nitrogen components from water to be treated by intermittent aeration operation, comprising: A water treatment method comprising a control step of controlling the operation of a discharge mechanism of a treatment tank based on the measurement results of nitrate nitrogen concentration or ammonia nitrogen concentration during a predetermined treatment time of one cycle, the control step being performed by defining an operation related to aeration and stirring with aeration stopped as one cycle.

6. A water treatment method for removing nitrogen components from water to be treated by intermittent aeration operation, comprising: A water treatment method comprising a control step of controlling the time for feeding the water to be treated into the treatment tank based on the measurement results of the nitrate nitrogen concentration or the ammonia nitrogen concentration during a predetermined treatment time of one cycle, the cycle consisting of one period of aeration and one period of stirring while the aeration is stopped.

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