JP2015098003A - Aeration agitation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aeration agitation system that stabilizes quality of treated water by controlling operation according to load change of water to be treated and achieves energy saving.SOLUTION: An aeration agitation system includes: a reaction tank 2 where circulating water to be treated is nitrified or denitrified; a vertical shaft type mechanical aeration agitator 11 that has a vertical shaft extending in the vertical direction and rotating around an axis and aerates and agitates the water to be treated in the reaction tank by rotating an impeller around the vertical shaft; a measurement unit 12 for measuring an amount of nitrogen in the water to be treated in the reaction tank 2; and a control unit 16 for controlling operation of the vertical shaft type mechanical aeration agitator 11 based on the amount of nitrogen measured by the measurement unit 12. The amount of oxygen to be supplied to the water to be treated is controlled based on the measured amount of nitrogen in the reaction tank 2.

Description

  The present invention relates to an aeration and stirring system for aeration or stirring of water to be treated in a reaction tank.

  2. Description of the Related Art Conventionally, in an oxidation ditch that nitrifies and denitrifies treated water such as sewage in a circulation channel, a vertical mechanical aeration apparatus has been employed (see, for example, Patent Document 1). This vertical mechanical aeration apparatus is connected to the vertical axis extending in the vertical direction, the impeller (stirring blade) attached to the lower end of the vertical axis, and the upper end of the vertical axis, and the rotational force is applied to the vertical axis. And a drive device for transmission. When the impeller rotates at a standard position near the gas-liquid interface, the water to be treated is scattered on the water surface, oxygen is supplied into the treated water, and the water to be treated is aerated. Moreover, the water to be treated can be efficiently stirred by lowering the impeller into water and rotating it.

Japanese Patent Laid-Open No. 2004-290797

  As a conventional operation method of the vertical type mechanical aeration apparatus, there are a continuous operation method, an intermittent operation method (or an intermittent aeration operation method), a control operation method based on the amount of dissolved oxygen, and the like. In the continuous operation type, continuous operation is performed by rotating the impeller at a constant rotational speed. In the intermittent operation method, the impeller is rotated as necessary, and the impeller is stopped when it is not necessary. In the intermittent aeration operation method, the impeller is rotated at a high speed to supply oxygen, the impeller is rotated at a low speed to slowly stir the water to be treated, and the rotation speed of the impeller is alternately switched between a high speed and a low speed. In the continuous operation method, the intermittent operation method, and the intermittent aeration operation method, the amount of oxygen supplied to the treated water could not be adjusted according to the load fluctuation of the treated water flowing in.

  In the control operation method based on the amount of dissolved oxygen, the dissolved oxygen concentration in the water to be treated, which is the control target, is set, and when the measured dissolved oxygen concentration is higher than the set value, the impeller rotation is reduced to reduce the oxygen concentration. When the supply amount was decreased and the measured dissolved oxygen amount was lower than the set value, the rotation speed of the impeller was increased. In such a control operation method based on the amount of dissolved oxygen, even when the degree of contamination of the water to be treated is low and oxygen supply is unnecessary, the operation is performed so as to keep the dissolved oxygen concentration in the reaction tank constant. There was room for reduction.

  An object of the present invention is to provide an aeration and agitation system that can control the operation in response to a load fluctuation of inflowing water to stabilize the quality of the water to be treated and can save energy.

  The aeration and agitation system of the present invention comprises a reaction tank for nitrifying or denitrifying the water to be circulated, and a reaction by rotating an impeller provided on the vertical axis having a vertical axis extending in the vertical direction and rotating about an axis. Vertical axis mechanical aeration stirrer for aeration and agitation of the water to be treated in the tank, measuring unit for measuring the nitrogen amount of the water to be treated in the reaction tank, and the vertical axis based on the nitrogen amount measured in the measuring part And a control unit for controlling the operation of the mold mechanical aeration stirrer.

  According to this aeration and agitation system, the nitrogen amount of the water to be treated in the reaction tank is measured by the measurement unit, and the control unit controls the operation of the vertical mechanical aeration agitator based on the measured nitrogen amount. Thereby, according to the load of to-be-processed water which flows into a reaction tank, the rotation speed of an impeller can be controlled and the amount of oxygen supplied to to-be-processed water can be increased or decreased. Therefore, the aeration and agitation system can stabilize the water quality of the treated water by adjusting the oxygen supply amount as necessary, and can suppress the rotation of the impeller when oxygen supply is unnecessary. Consumption can be suppressed.

  Here, the measurement unit measures the ammonia nitrogen amount and the nitrate nitrogen amount as the nitrogen amount, and the control unit determines whether the impeller is in the aeration operation when the ammonia nitrogen amount is equal to or more than the first determination threshold value. While increasing the rotation speed, the rotation speed of the impeller may be decreased when the ammonia nitrogen amount is less than the first determination threshold and the nitrate nitrogen amount is greater than or equal to the second determination threshold. As a result, when the ammonia nitrogen amount is equal to or greater than the first determination threshold, the rotation speed of the impeller can be increased to increase the oxygen supply amount and promote nitrification. When nitrification of ammonia is promoted, ammonia in the water to be treated decreases and nitric acid increases. Further, the aeration and agitation system reduces the impeller rotational speed and reduces the oxygen supply amount when the ammonia nitrogen amount is less than the first determination threshold value and the nitrate nitrogen amount is not less than the second determination threshold value. Can be reduced. In accordance with the decrease in ammonia and the increase in nitric acid in the water to be treated, the denitrification can be promoted by decreasing the oxygen supply amount, and nitric acid can be changed to nitrogen gas. Accordingly, in the aeration and stirring system, the operation can be controlled according to the amount of ammoniacal nitrogen in the treated water to stabilize the quality of the treated water and to save energy.

  In addition, the measurement unit measures the ammonia nitrogen amount as the nitrogen amount, and the control unit increases the rotation speed of the impeller when the ammonia nitrogen amount is equal to or higher than the first determination threshold in the aeration operation. When the ammoniacal nitrogen amount is less than the first determination threshold, the rotation speed of the impeller may be decreased. As a result, when the ammonia nitrogen amount increases, the rotation speed of the impeller is increased to increase the oxygen supply amount, and when the ammonia nitrogen amount decreases, the rotation speed of the impeller is decreased to supply oxygen. The amount can be reduced.

  Here, the measurement unit measures the ammonia nitrogen amount as the nitrogen amount, and the control unit rotates the impeller at the first rotation speed when the ammonia nitrogen amount is equal to or higher than the upper limit in the aeration operation, When the amount of ammonia nitrogen is less than the upper limit value and greater than or equal to the lower limit value, the impeller is rotated at a second rotation speed less than the first rotation speed, and when the amount of ammonia nitrogen is less than the lower limit value, The rotation may be performed at a third rotation number that is less than the second rotation number. Thus, the oxygen supply amount can be controlled by changing the number of revolutions of the impeller in three stages according to the ammoniacal nitrogen amount.

  Further, the measurement unit measures the amount of ammonia nitrogen as the amount of nitrogen, and the control unit performs an aeration operation when the amount of ammonia nitrogen is equal to or higher than the lower limit, and the amount of ammonia nitrogen is less than the lower limit. In some cases, the aeration operation may be terminated and the oxygen-free operation may be executed. Accordingly, the oxygen supply amount can be controlled according to the ammonia nitrogen amount, and the control can be simplified.

  ADVANTAGE OF THE INVENTION According to this invention, the aeration stirring system which can aim at energy saving while controlling operation according to the load fluctuation | variation of the inflowing to-be-processed water, stabilizing the quality of treated water can be provided.

It is a schematic plan view which shows the oxidation ditch to which the aeration stirring system of one Embodiment of this invention was applied. It is a side view which shows the impeller of the vertical axis | shaft type mechanical aeration stirrer in FIG. It is a flowchart which shows the control procedure of the aeration stirring system which concerns on 1st Example. It is a flowchart which shows the control procedure of the aeration stirring system which concerns on 2nd Example. It is a flowchart which shows the control procedure of the aeration stirring system which concerns on 3rd Example. It is a flowchart which shows the control procedure of the aeration stirring system which concerns on 4th Example. It is a table | surface which shows the driving | running state according to the amount of ammonia nitrogen and the amount of nitrate nitrogen at the time of aeration operation | movement of the aeration stirring system which concerns on 4th Example. It is a flowchart which shows the control procedure of the aeration stirring system which concerns on 5th Example. It is a table | surface which shows the driving | running state according to the amount of ammonia nitrogen and the amount of nitrate nitrogen at the time of aeration operation | movement of the aeration stirring system which concerns on 5th Example. It is a schematic plan view which shows the oxidation ditch to which the aeration stirring system of one Embodiment of this invention was applied.

  Hereinafter, an embodiment of an oxidation ditch to which an aeration stirring system according to the present invention is applied will be described in detail with reference to the drawings.

  An oxidation ditch 1 shown in FIG. 1 is employed as a water treatment facility such as a small-scale sewage treatment plant. The oxidation ditch 1 includes a reaction tank 2 having an oval shape in plan view, and a partition wall 3 extending in the longitudinal direction is disposed at the center of the reaction tank 2. A region around the partition wall 3 is an endless circulation channel 4. To-be-treated water such as sewage is introduced into the circulation channel 4 through the inlet 2a, and treated water treated in the circulation channel 4 is led out from the circulation channel 4 through the outlet 2b.

  The oxidation ditch 1 includes a vertical axis mechanical aeration stirrer 11 that aerates and stirs water to be treated in the reaction tank 2, and the vertical axis mechanical aeration stirrer 11 is disposed at the center in the longitudinal direction of the reaction tank 2. Has been. As shown in FIG. 2, the vertical mechanical aeration stirrer 11 has a vertical axis 21 that extends in the vertical direction and rotates about an axis, and an impeller 22 is provided at the lower end of the vertical axis 21. . The vertical axis type mechanical aeration stirrer 11 includes an impeller rotating electric motor as a driving source for rotating the impeller 22, a driving force transmission device that decelerates and transmits the rotational driving force of the impeller rotating electric motor, and a vertical axis 21. And an elevating device that is supported rotatably and is capable of elevating. This lifting device has a cylinder as a drive source for lifting and lowering the vertical axis 21.

  A plurality of blade-like impellers 22 (eight in this embodiment) are attached radially from the outer peripheral surface of the vertical axis 21. Each impeller 22 includes a cone-shaped plate 22a on an impeller facing surface as a side surface and a bent portion 22b on an upper portion thereof, so that water to be treated can be easily stirred during rotation. During aerobic operation, the number of revolutions of the impeller 22 is increased to generate appropriate splashes, and air is supplied to the water to be treated for aeration. At the time of anaerobic operation, the impeller 22 is lowered to reduce the rotational speed, and the water to be treated is stirred.

  In the oxidation ditch 1, two vertical mechanical aeration stirrers 11 are provided, and each vertical mechanical aeration stirrer 11 is formed across the partition wall 3 of the reaction tank 2 and arranged upstream of the circulation channel 4. Has been. The amount of water to be treated in the reaction tank 2 is adjusted so that the impeller 22 is immersed, and circulates in the reaction tank 2 in the counterclockwise direction in the drawing according to the rotation of the impeller 22 driven by the impeller rotating motor.

  In the oxidation ditch 1, an aerobic state is formed by rotating near the water surface of the impeller 22, and an anaerobic state is formed by slowly lowering the impeller 22 and rotating it slowly.

  The aeration and stirring system of the oxidation ditch 1 includes the reaction tank 2 described above, a vertical axis mechanical aeration and stirring machine 11, and an oxygen supply system 10 that controls the supply of oxygen into the reaction tank 2. The oxygen supply system 10 includes a nitrogen monitor (measurement unit) 12 that measures the amount of nitrogen in the water to be treated in the reaction tank 2, and a vertical axis mechanical aeration stirrer 11 based on the measurement result measured by the nitrogen monitor 12. And a control panel 13 for controlling the operation.

  The nitrogen monitor 12 measures an ammonia nitrogen amount (ammonia nitrogen concentration) and a nitrate nitrogen amount (nitrate nitrogen concentration) as nitrogen amounts in the water to be treated in the reaction tank 2. Since the amount of nitrogen in the reaction tank 2 is substantially uniform, the nitrogen monitor 12 may be disposed at any position in the reaction tank 2. A detection signal detected by the nitrogen monitor 12 is transmitted to the control panel 13.

  The control panel (control unit) 13 includes a CPU that performs arithmetic processing, a ROM and a RAM that serve as the storage unit 17, an input signal circuit, an output signal circuit, a power supply circuit, and the like. In the control panel 13, an operating condition setting unit 14, a determination unit 15, and a control unit 16 are constructed by executing a program stored in the storage unit 17. A nitrogen monitor 12 and a vertical axis mechanical aeration stirrer 11 are electrically connected to the control panel 13.

  The operating condition setting unit 14 sets the operating conditions of the aeration and agitation system based on, for example, an input operation by the operator. The operating conditions include one cycle time, aeration time, ammonia nitrogen amount target value, aeration operation start time, and the like. As other operating conditions, an upper limit value of the ammonia nitrogen amount, a lower limit value of the ammonia nitrogen amount, an upper limit value of the nitrate nitrogen amount, a lower limit value of the nitrate nitrogen amount, and the like may be set. One cycle time is a period of one cycle that is repeatedly executed, and is a total time of an aeration time and an oxygen-free operation time. For example, when 1 cycle time is set to 4 hours, the operation of 6 cycles a day will be performed, and an aeration operation and an oxygen-free operation will be performed 6 times alternately.

  The determination unit 15 compares the measurement value obtained by the nitrogen monitor 12 with a target value (determination threshold) to determine whether or not the amount of nitrogen in the water to be treated in the reaction tank 2 is equal to or greater than the target value. Further, the determination unit 15 determines whether or not the operation time is less than the set aeration time, and determines whether or not the operation time is less than one set cycle time.

  The control unit 16 controls the vertical axis mechanical aeration stirrer 11 based on the determination result by the determination unit 15. The control unit 16 outputs a control signal to the vertical mechanical aeration stirrer 11 to increase or decrease the rotational speed of the impeller 22. Moreover, a control signal is output to the vertical mechanical aeration stirrer 11 and the impeller 22 is raised or lowered to switch between the aeration operation and the oxygen-free operation.

  The storage unit 17 stores information related to the operation condition set by the operation condition setting unit 14. Further, the storage unit 17 stores a measurement value obtained by the nitrogen monitor 12.

  Next, a control procedure (operation example) of the aeration and stirring system will be described with reference to FIGS.

(First embodiment)
FIG. 3 is a flowchart showing a control procedure of the aeration and agitation system according to the first embodiment. First, the operating condition setting unit 14 sets operating conditions for the aeration and agitation system. The operation condition setting unit 14 sets, for example, 1 cycle time as 6 hours, aeration time as 3 hours, and aeration operation start time as 6 o'clock. The target value of the amount of ammonia nitrogen is determined according to the required water quality standard.

  After the operating conditions are set, the aeration and stirring system starts one cycle operation (step S1), starts the aeration operation (step S2), and starts measuring the operation time. The control unit 16 transmits a control signal to the vertical mechanical aeration stirrer 11 to place the impeller 22 near the water surface and rotate it at a predetermined rotational speed. Thereby, oxygen is supplied into to-be-processed water and the inside of the reaction tank 2 is made into an aerobic state.

  Next, the determination unit 15 determines whether or not the operation time is less than the aeration time (step S3). If it is determined that the operation time is less than the aeration time (step S3: YES), the process proceeds to step S6. If the operation time reaches the aeration time (step S3: NO), the process proceeds to step S4.

  In step S6, the amount of nitrogen in the water to be treated is measured (step S6). Based on the data measured by the nitrogen monitor 12, the control panel 13 calculates the amount of ammoniacal nitrogen (measured value) in the water to be treated, and proceeds to step S7.

  In step S7, the determination unit 15 determines whether or not the measured value of the ammonia nitrogen amount exceeds the target value. When it is determined that the measured value of the ammonia nitrogen amount exceeds the target value (step S7: YES), the process proceeds to step S8, and when the measured value of the ammonia nitrogen amount is less than the target value (step S7: If NO, the process proceeds to step S9.

  In step S8, the control unit 16 transmits a control signal to the vertical axis mechanical aeration stirrer 11 to increase the rotation speed of the impeller 22 and increase the amount of oxygen supplied to the water to be treated. In step S <b> 9, the control unit 16 transmits a control signal to the vertical mechanical aeration stirrer 11 to reduce the rotation speed of the impeller 22 and reduce the amount of oxygen supplied to the water to be treated. After executing the processes of steps S8 and S9, the process returns to step S2 again, and the aeration operation is continued.

  The control panel 13 repeats the processes from step S6 to S9 until it is determined in step S3 that the operation time has reached the aeration time. That is, in a state where the measured value of the ammonia nitrogen amount exceeds the target value, the rotation speed of the impeller 22 is increased and the supply amount of oxygen is continuously increased. If the measured value of the ammonia nitrogen amount falls below the target value, the rotational speed of the impeller 22 is reduced and the oxygen supply amount is also reduced.

  In step S3, when the operation time reaches the set aeration time (step S3: NO), the process proceeds to step S4 to perform intermittent aeration operation. Here, the control part 16 transmits a control signal to the vertical axis type mechanical aeration stirrer 11 to lower the impeller 22 and submerge it in water, and at the same time reduce the rotational speed to execute the oxygen-free operation.

  In subsequent step S5, the determination unit 15 determines whether or not the operation time is less than the set one cycle time. If it is determined that the operation time is less than one cycle time (step S5: YES), the process returns to step S4 and the intermittent aeration operation is continued. When the operation time reaches one cycle time (step S5: NO), the one-cycle operation is terminated, the process proceeds to step S1 again, the operation of the next cycle is started, and the aeration operation is started (step S2). .

  In such an aeration and agitation system, the amount of ammonia nitrogen in the water to be treated in the reaction tank 2 is measured by the nitrogen monitor 12, and the control unit 16 uses the vertical mechanical aeration agitator based on the measured amount of ammonia nitrogen. 11 operation is controlled. Thereby, the number of oxygen supplied to the water to be treated can be increased or decreased by controlling the rotation speed of the impeller 22 according to the load (contamination degree or flow rate) of the water to be treated flowing into the reaction tank 2. it can. When the amount of ammonia nitrogen is large and the load of water to be treated is large, the amount of oxygen supplied can be increased to stabilize the water quality. On the other hand, when the amount of ammonia nitrogen is small and the load of water to be treated is small, supply of useless oxygen can be reduced, rotation of the impeller 22 can be suppressed, and energy consumption can be suppressed.

(Second embodiment)
FIG. 4 is a flowchart showing a control procedure of the aeration and agitation system according to the second embodiment. The same description as in the first embodiment is omitted. The difference between the second embodiment and the first embodiment is the processing after performing step S6 in the aeration operation. In the second embodiment, operating conditions different from those in the first embodiment are set.

  The operating condition setting unit 14 sets a lower limit value of the ammonia nitrogen amount and an upper limit value of the ammonia nitrogen amount as target values for the ammonia nitrogen amount. Further, the operation condition setting unit 14 sets the maximum value of oxygen supply amount during the aeration operation (operation with 100% oxygen supply amount) and the minimum value of oxygen supply amount.

  The control panel 13 of the aeration and agitation system calculates the amount of ammonia nitrogen (measured value) in the water to be treated (step S6), and proceeds to step S11. In step S11, the determination unit 15 determines whether or not the measured value of the ammonia nitrogen amount is larger than the set lower limit value. When it is determined that the measured value of the ammonia nitrogen amount is larger than the lower limit value (step S11: YES), the process proceeds to step S12, and when the measured value of the ammonia nitrogen amount is less than the lower limit value (step S11: NO) ) Proceeds to step S13.

  In step S13, the control unit 16 transmits a control signal to the vertical mechanical aeration stirrer 11, sets the rotation speed of the impeller 22 to the impeller rotation speed lower limit value, and executes the oxygen supply stop operation. After the process of step S13 is executed, the process returns to step S2 again and the aeration operation is continued.

  In step S12, the determination unit 15 determines whether or not the measured value of the ammonia nitrogen amount is larger than the set upper limit value. When it is determined that the measured value of the ammonia nitrogen amount is larger than the upper limit value (step S12: YES), the process proceeds to step S15, and when the measured value of the ammonia nitrogen amount is determined to be less than the upper limit value (step S12). In S12: NO), the process proceeds to step S14.

  In Step S15, the control unit 16 transmits a control signal to the vertical mechanical aeration stirrer 11, sets the rotation speed of the impeller 22 to the upper limit value of the impeller rotation speed, and executes the oxygen supply amount 100% operation. Thereby, the process in an aerobic state can be accelerated | stimulated by making the oxygen supply amount to to-be-processed water into the maximum value. After the process of step S15 is executed, the process returns to step S2 again and the aeration operation is continued.

  In step S14, the control unit 16 transmits a control signal to the vertical mechanical aeration stirrer 11, sets the rotation speed of the impeller 22 to a value half the impeller rotation speed upper limit value, and performs the oxygen supply amount 50 operation. Run. Thereby, the process in an aerobic state can be performed by setting the oxygen supply amount to the water to be treated to 50% of the maximum value. After the process of step S14 is executed, the process returns to step S2 again and the aeration operation is continued.

  In such aeration and agitation system, in the aeration operation, when the ammonia nitrogen amount is larger than the set upper limit value, the impeller 22 is rotated at the impeller rotation speed upper limit value (first rotation speed), and the ammonia nitrogen amount is increased. Is lower than the set upper limit value and larger than the lower limit value, the impeller 22 is rotated at 50% of the impeller rotational speed upper limit value (second rotational speed), and the lower limit value in which the amount of ammoniacal nitrogen is set. If it is less, the impeller 22 can be rotated at the impeller rotational speed lower limit (second rotational speed). Thereby, according to the ammonia nitrogen amount in to-be-processed water, oxygen supply amount can be switched to three steps and oxygen supply amount can be controlled. As a result, it is possible to stabilize the quality of the treated water by controlling the operation in response to the load fluctuation of the treated water flowing in, and to save energy.

(Third embodiment)
FIG. 5 is a flowchart showing a control procedure of the aeration and agitation system according to the third embodiment. The same description as in the first embodiment is omitted. The third embodiment is different from the first embodiment in the processing after executing step S6 in the aeration operation. In the third embodiment, operating conditions different from those in the first embodiment are set.

  The operating condition setting unit 14 sets a lower limit value of the ammonia nitrogen amount as the target value of the ammonia nitrogen amount. The operating condition setting unit 14 sets the maximum aeration time within one cycle.

  The control panel 13 of the aeration and agitation system calculates the amount of ammonia nitrogen (measured value) in the water to be treated (step S6), and proceeds to step S11. In step S11, the determination unit 15 determines whether or not the measured value of the ammonia nitrogen amount is larger than the set lower limit value. When it is determined that the measured value of the ammonia nitrogen amount is larger than the lower limit value (step S11: YES), the process returns to step S2 and the aeration operation is continued, and the measured value of the ammonia nitrogen amount is less than the lower limit value In (Step S11: NO), it progresses to Step S16.

  The control panel 13 determines whether or not the operation time is less than the maximum aeration time during the aeration operation (step S3). When the operation time is less than the maximum aeration time and the measured value of the ammonia nitrogen amount is greater than the set lower limit value, the processes of steps S2, S3, S6, and S11 are repeated, and the aeration operation is continued. .

  When it is determined that the operation time has reached the aeration time (step S3: NO) and when the measured value of the ammonia nitrogen amount is smaller than the lower limit (step S11: NO), the process proceeds to step S16 and the aeration operation is terminated. Then perform anaerobic operation. Here, the control unit 16 transmits a control signal to the vertical mechanical aeration stirrer 11 to lower the impeller 22 and lower the rotation speed of the impeller 22. Thereby, an anaerobic state is formed in the reaction tank 2.

  After step S16, the process proceeds to step S5, where it is determined whether the operation time is shorter than one cycle time, and whether the operation time has reached one cycle time. If the operation time has not reached one cycle time (step S5: YES), the oxygen-free operation is continued. When the operation time has reached one cycle time (step S5: NO), the oxygen-free operation is terminated and the operation of one cycle is terminated, and the operation returns to step S1 again to start the operation of the next cycle. The impeller 22 is raised near the water surface, and the rotation speed of the impeller 22 is increased to start the aeration operation (step S2).

  In such aeration and agitation system, the aeration operation is continued when the amount of ammoniacal nitrogen is larger than the lower limit value during the aeration operation, and the aeration operation is terminated when the amount of ammoniacal nitrogen is smaller than the lower limit value and the oxygen-free operation is performed. Can be switched. Thus, when the ammonia nitrogen amount falls below the lower limit value, the operation is switched to the oxygen-free operation before the set maximum aeration time elapses, so that wasteful oxygen supply can be suppressed to save energy.

(Fourth embodiment)
FIG. 6 is a flowchart showing a control procedure of the aeration and agitation system according to the fourth embodiment. The same description as in the first embodiment is omitted. The fourth embodiment is different from the first embodiment in the processing after step S6 is executed in the aeration operation. In the fourth embodiment, operating conditions different from those in the first embodiment are set. In the fourth embodiment, the supply amount of oxygen can be changed based on the amount of ammonia nitrogen (NH ₄ —N) and the amount of nitrate nitrogen (NO ₃ —N).

  The operating condition setting unit 14 sets the lower limit value of the ammonia nitrogen amount and the upper limit value of the ammonia nitrogen amount as the target value of the ammonia nitrogen amount, and sets the nitrate nitrogen amount as the target value of the nitrate nitrogen amount. Set the upper limit.

  The control panel 13 of the aeration and agitation system calculates the amount of ammonia nitrogen (measured value) and the amount of nitrate nitrogen (measured value) in the water to be treated (step S6), and proceeds to step S21. In step S21, the determination unit 15 determines whether or not the measured value of the ammonia nitrogen amount is larger than the set upper limit value. When it is determined that the measured value of the ammonia nitrogen amount is larger than the upper limit value (step S21: YES), the process proceeds to step S24, and when the measured value of the ammonia nitrogen amount is less than the upper limit value (step S21: NO) ) Proceeds to step S22.

  In step S <b> 24, the control unit 16 transmits a control signal to the vertical axis mechanical aeration stirrer 11 to increase the rotation speed of the impeller 22. After the process of step S24 is executed, the process returns to step S2 again and the aeration operation is continued.

  In step S22, the determination unit 15 determines whether or not the measured value of the ammonia nitrogen amount is greater than the set lower limit value. When it is determined that the measured value of the ammonia nitrogen amount is larger than the lower limit value (step S22: YES), the process proceeds to step S23, and the measured value of the ammonia nitrogen amount is determined to be less than the lower limit value. In (Step S22: NO), the process proceeds to Step S25.

  In step S23, the determination part 15 determines whether the measured value of nitrate nitrogen amount is larger than the set upper limit value. When it is determined that the measured value of the nitrate nitrogen amount is larger than the upper limit value (step S23: YES), the process proceeds to step S25, and when the measured value of the nitrate nitrogen amount is less than the upper limit value (step S23: NO) returns to step S2 without changing the rotation speed of the impeller 22, and continues the aeration operation.

  In step S <b> 25, the control unit 16 transmits a control signal to the vertical mechanical aeration stirrer 11 to reduce the rotation speed of the impeller 22. After the process of step S25 is performed, it returns to step S2 again and aeration operation is continued.

  FIG. 7 is a table showing the operation status during the aeration operation of the aeration and agitation system according to the fourth example, and shows the increase and decrease of the oxygen supply amount according to the ammonia nitrogen amount and the nitrate nitrogen amount. When the ammonia nitrogen amount is larger than the upper limit value, the rotation speed of the impeller 22 is increased and the oxygen supply amount is increased regardless of the nitrate nitrogen amount. When the ammonia nitrogen amount is less than the lower limit value, the rotation speed of the impeller 22 is decreased and the oxygen supply amount is decreased regardless of the nitrate nitrogen amount.

  When the ammonia nitrogen amount is less than the upper limit value and greater than the lower limit value, and when the nitrate nitrogen amount is greater than the upper limit value, the rotation speed of the impeller 22 is decreased and the oxygen supply amount is decreased. .

  When the ammonia nitrogen amount is less than the upper limit value and greater than the lower limit value, and when the nitrate nitrogen amount is less than the upper limit value, the rotation speed of the impeller 22 is not changed and the oxygen supply amount is maintained. Aeration operation is continued.

  In such an aeration and stirring system, the amount of ammonia nitrogen and the amount of nitrate nitrogen are measured, and in the aeration operation, when the amount of ammonia nitrogen is larger than the set upper limit (first determination threshold), the impeller 22 The rotational speed of the impeller 22 can be decreased when the rotational speed is increased and the ammonia nitrogen amount is less than the upper limit value and the nitrate nitrogen amount is greater than the set upper limit value (second determination threshold). . Thereby, when the ammonia nitrogen amount is larger than the upper limit value, the oxygen supply amount can be increased to promote nitrification. When nitrification of ammonia is promoted, ammonia in the water to be treated decreases and nitric acid increases. When the amount of ammonia nitrogen is less than the upper limit and the amount of nitrate nitrogen is greater than or equal to the upper limit, the aeration and agitation system can reduce the rotation speed of the impeller and reduce the oxygen supply amount. In accordance with the decrease in ammonia in the treated water and the increase in nitric acid, the oxygen supply amount can be decreased to promote denitrification, and nitric acid can be changed to nitrogen gas. Accordingly, in the aeration and stirring system, the operation can be controlled according to the amount of ammoniacal nitrogen in the treated water to stabilize the quality of the treated water and to save energy.

(Fifth embodiment)
FIG. 8 is a flowchart showing a control procedure of the aeration and agitation system according to the fifth embodiment. The same description as in the first and fourth embodiments is omitted. The fifth embodiment is different from the fourth embodiment in the processing after executing steps S21 to S23 in the aeration operation.

  The operation condition setting unit 14 sets the rotation speed of the impeller 22 during the aeration operation in three stages of high speed operation, medium speed operation, and low speed operation. The rotational speed of the impeller 22 in the high speed operation, the medium speed operation, and the low speed operation can be set based on past operation data and test results, for example. The oxygen supply amount in the high speed operation is larger than the oxygen supply amount in the medium speed operation, and the oxygen supply amount in the medium speed operation is larger than the oxygen supply amount in the low speed operation.

  When the control panel 13 of the aeration and agitation system determines that the measured value of the ammonia nitrogen amount is larger than the upper limit value (step S21: YES), the process proceeds to step S27, where the measured value of the ammonia nitrogen amount is the upper limit value. If it is less (step S21: NO), the process proceeds to step S22.

  In step S27, the control unit 16 transmits a control signal to the vertical axis mechanical aeration stirrer 11 to cause the impeller 22 to operate at high speed. After the process of step S27 is executed, the process returns to step S2 again and the aeration operation is continued.

  In step S22, the determination unit 15 determines whether or not the measured value of the ammonia nitrogen amount is greater than the set lower limit value. When it is determined that the measured value of the ammonia nitrogen amount is larger than the lower limit value (step S22: YES), the process proceeds to step S23, and the measured value of the ammonia nitrogen amount is determined to be less than the lower limit value. In (Step S22: NO), it progresses to Step S29.

  In step S23, the determination part 15 determines whether the measured value of nitrate nitrogen amount is larger than the set upper limit value. When it is determined that the measured value of the nitrate nitrogen amount is larger than the upper limit value (step S23: YES), the process proceeds to step S29, and when the measured value of the nitrate nitrogen amount is less than the upper limit value (step S23: If NO, the process proceeds to step S28.

  In step S28, the control unit 16 transmits a control signal to the vertical axis mechanical aeration stirrer 11 to cause the impeller 22 to operate at a medium speed. In step S29, the control unit 16 transmits a control signal to the vertical axis mechanical aeration stirrer 11 to cause the impeller 22 to operate at a low speed. After the processes of steps S28 and S29 are executed, the process returns to step S2 again and the aeration operation is continued.

  FIG. 9 is a table showing the operation status during the aeration operation of the aeration and agitation system according to the fifth embodiment, and shows the operation status of the impeller according to the ammonia nitrogen amount and the nitrate nitrogen amount. When the ammonia nitrogen amount is larger than the upper limit value, the impeller 22 is set to operate at a high speed and increase the oxygen supply amount regardless of the nitrate nitrogen amount. When the ammonia nitrogen amount is less than the lower limit value, the impeller 22 is operated at a low speed regardless of the nitrate nitrogen amount, and the oxygen supply amount is set to be small.

  When the ammonia nitrogen amount is less than the upper limit value and greater than the lower limit value, and when the nitrate nitrogen amount is greater than the upper limit value, the impeller 22 is operated at a low speed and the oxygen supply amount is set to be small. The

  When the amount of ammonia nitrogen is less than the upper limit value and greater than the lower limit value, and when the amount of nitrate nitrogen is less than the upper limit value, the impeller 22 is operated at a medium speed and the oxygen supply amount becomes moderate. Is set as follows.

  Even in the aeration and agitation system according to the fifth embodiment, the operation of the vertical mechanical aeration and agitator 11 is controlled according to the load of the water to be treated to stabilize the water quality and suppress the wasteful oxygen supply. Energy can be reduced.

  The present invention is not limited to the above-described embodiments, and various modifications as described below are possible without departing from the gist of the present invention.

  In the above embodiment, for example, the speed of the impeller 22 is set in three stages of high speed operation, medium speed operation, and low speed operation, but the speed may be set in four or more stages. Further, in the above embodiment, the oxygen supply amount is changed by changing the speed of the impeller 22, but the oxygen supply amount is changed by changing the number of the vertical axis type mechanical aeration stirrers 11 to be operated. It may be. For example, when the oxygen supply amount is increased, two vertical mechanical aeration stirrers 11 are operated, and when the oxygen supply amount is decreased, one vertical mechanical aeration stirrer 11 is operated. May be.

  Further, the vertical axis mechanical aeration stirrer 11 may be arranged at any position in the reaction tank 2. For example, as shown in FIG. 10, the present invention may be applied to an oxidation ditch 1 </ b> B in which a longitudinal mechanical aeration stirrer 11 is provided at an end portion in the longitudinal direction of the reaction tank 2.

  DESCRIPTION OF SYMBOLS 1,1B ... oxidation ditch, 2 ... reaction tank, 11 ... vertical axis | shaft type mechanical aeration stirrer, 12 ... nitrogen monitor (measurement part), 16 ... control part, 22 ... impeller.

Claims (5)

A reaction tank that nitrifies or denitrifies the water to be circulated;
A vertical axis type mechanical aeration stirrer that has a vertical axis that extends in the vertical direction and rotates around an axis and rotates the impeller provided on the vertical axis to aerate and agitate the water to be treated in the reaction tank;
A measurement unit for measuring the nitrogen amount of the water to be treated in the reaction vessel;
And a control unit that controls the operation of the vertical mechanical aeration stirrer based on the nitrogen amount measured by the measurement unit. The measurement unit measures an ammonia nitrogen amount and a nitrate nitrogen amount as the nitrogen amount,
In the aeration operation, the controller increases the rotation speed of the impeller and the ammonia nitrogen amount is less than the first determination threshold when the ammonia nitrogen amount is equal to or greater than the first determination threshold. 2. The aeration and agitation system according to claim 1, wherein when the amount of nitrate nitrogen is equal to or greater than a second determination threshold value, the rotational speed of the impeller is decreased. The measurement unit measures an ammoniacal nitrogen amount as the nitrogen amount,
In the aeration operation, the controller increases the rotation speed of the impeller and the ammonia nitrogen amount is less than the first determination threshold when the ammonia nitrogen amount is equal to or greater than the first determination threshold. The aeration and agitation system according to claim 1, wherein in some cases, the rotational speed of the impeller is decreased. The measurement unit measures an ammoniacal nitrogen amount as the nitrogen amount,
In the aeration operation, the controller rotates the impeller at a first rotational speed when the ammonia nitrogen amount is equal to or higher than the upper limit value, and the ammonia nitrogen amount is less than the upper limit value and equal to or higher than the lower limit value. The impeller is rotated at a second rotational speed less than the first rotational speed, and when the ammoniacal nitrogen amount is less than a lower limit value, the impeller is rotated at a third rotational speed that is smaller than the second rotational speed. The aeration and stirring system according to claim 1, wherein the aeration and stirring system is rotated at a rotational speed. The measurement unit measures an ammoniacal nitrogen amount as the nitrogen amount,
The controller performs the aeration operation when the ammonia nitrogen amount is equal to or higher than the lower limit value, and ends the aeration operation when the ammonia nitrogen amount is less than the lower limit value, and performs the oxygen-free operation. The aeration and stirring system according to claim 1, wherein the aeration and stirring system is executed.

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