JP2007105664A - Aeration equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize optimization of aeration control at a low cost in aeration equipment for aerating a large aeration tank requiring a plurality of blowers. <P>SOLUTION: The aeration equipment 100 comprises the aeration tank 10, a measuring instrument 30 for measuring the dissolved oxygen concentration of sewage in the aeration tank 10, a plurality of on-off control blowers 42, 44, 46 for supplying air into the aeration tank 10, an inverter controlled blower 48 for supplying air into the aeration tank 10, and a controller 70. The controller 70 controls the number of the on-off control blowers 42, 44, 46 to be operated, and the revolution number of the inverter controlled blower 48 based on the dissolved oxygen concentration measured by the measuring instrument 30 so that the dissolved oxygen concentration of the sewage 20 in the aeration tank 10 is adjusted to a target dissolved oxygen concentration. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an aeration facility for aeration of sewage in an aeration tank.

  As a method for treating sewage containing organic matter, there is an activated sludge treatment method. Sewage containing organic matter is retained in the aeration tank and aerated (aeration), whereby microorganisms such as aerobic bacteria and protozoa are propagated to generate activated sludge. Activated sludge is composed of flocs composed of bacteria and gelatin-like adhesive substances produced thereby, and protozoa that live around them. Such activated sludge captures organic matter in the sewage and promotes its oxidation, whereby the organic matter in the sewage is decomposed.

  In such an activated sludge treatment method, it is important to manage the dissolved oxygen (DO) concentration in the aeration tank in order to optimally maintain the activated state of microorganisms constituting the activated sludge. For this purpose, the dissolved oxygen concentration in the aeration tank is measured, and the supply of air (oxygen) to the aeration tank is controlled based on the measured value.

Patent Documents 1 and 2 describe that the sewage in the aeration tank is aerated with an inverter-controlled blower.
JP-A-10-151477 Japanese Patent Laid-Open No. 06-126293

  When the aeration tank is enlarged, it becomes difficult to supply air to the aeration tank with one blower, and a plurality of blowers can be used. In such a large aeration facility, it is conceivable that all blowers are inverter-controlled blowers as described in Patent Documents 1 and 2. However, in such a method, it is necessary to control the rotation speed of all the blowers, and the cost of the equipment also increases. On the other hand, it is also conceivable to control the amount of air supplied to the aeration tank by controlling all the blowers to be on-off control type blowers and controlling the number to be operated. However, with such a method, it is difficult to finely adjust the amount of air supplied to the aeration tank, and it is difficult to optimally maintain the activated state of the activated sludge.

  The present invention has been made on the basis of recognition of the above-described problems. For example, in a facility for aeration of a large aeration tank that requires a plurality of blowers, optimization of aeration control is realized at low cost. For the purpose.

  The aeration equipment according to the present invention is configured as equipment for aeration of sewage, and includes an aeration tank, a measuring instrument for measuring dissolved oxygen concentration in the sewage in the aeration tank, and a plurality of on / off devices for supplying air into the aeration tank. A control type blower, an inverter control type blower for supplying air into the aeration tank, and a controller are provided. The controller is configured to operate the plurality of on-off control blowers so that the dissolved oxygen concentration of the sewage in the aeration tank becomes a target dissolved oxygen concentration based on the dissolved oxygen concentration measured by the measuring device. And the rotation speed of the inverter-controlled blower.

  According to a preferred embodiment of the present invention, the controller operates the plurality of on / off control blowers when a time during which the inverter control blower is continuously operated at the maximum rotation speed exceeds a specified time. It is preferable that the number of the plurality of on / off control type blowers be decreased when the number of times increases and the time during which the inverter control type blowers are continuously operated at the minimum rotation speed exceeds a specified time.

  ADVANTAGE OF THE INVENTION According to this invention, the optimization of aeration control is realizable at low cost, for example in the facility which aerates a large aeration tank which requires a plurality of blowers.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a diagram schematically showing an aeration facility according to a preferred embodiment of the present invention. The aeration equipment 100 according to a preferred embodiment of the present invention includes an aeration tank 10 in which sewage 20 is temporarily retained. For example, waste water (sewage) from the production facility is supplied to the aeration tank 10 through the port 12 from the factory facility. This sewage contains organic matter. The water aerated in the aeration tank 10 (aerated water) is typically discharged through a port 14 to a settling tank (not shown). The aerated water includes activated sludge generated in the aeration tank 10, and this activated sludge is precipitated in the settling tank. The supernatant water of the sedimentation tank can be discharged to the sewer as purified water.

  The aeration equipment 100 further includes a measuring device (DO concentration meter) 30 for measuring the dissolved oxygen concentration of the sewage 20 in the aeration tank 10 and a plurality of on / off control type blowers 42 and 44 for supplying air into the aeration tank 10. 46, at least one inverter-controlled blower 48, and a controller 70 that controls the concentration of dissolved oxygen in the sewage 20 by controlling the blowers 42, 44, 44, 46.

  The sewage 20 in the aeration tank 10 is aerated by sending air to the air diffuser (aerator) 80 by the blowers 42, 44, 46 and 48. The dissolved oxygen concentration in the sewage 20 in the aeration layer 10 is increased by aeration.

  The controller 70 sets the dissolved oxygen concentration of the sewage 20 in the aeration tank 10 to the target dissolved oxygen concentration (hereinafter, target DO value) based on the dissolved oxygen concentration (hereinafter, measured DO value) measured by the measuring device 30. In this manner, the number of operating the plurality of on / off control blowers 42, 44, 46 and the rotation speed of at least one inverter control blower 48 are controlled. According to such control, it is possible to finely adjust the dissolved oxygen concentration in the sewage 20 without using all the blowers as inverter-controlled blowers. Therefore, aeration control (dissolved oxygen concentration control) can be optimized at low cost.

  The operation (on / off operation) of the on / off control type blowers 42, 44, 46 can be performed by the main controller 60 instructing the on / off controllers (switches) 52, 54, 56 to be turned on or off. The rotation speed of the inverter-controlled blower 48 can be determined by the main controller 60 instructing the rotation speed (frequency) to the inverter 58 that controls the rotation speed of the inverter-controlled blower 48. Here, the main controller 60 controls the on / off controllers 52, 54, and 56 (the blowers 42, 44, and 46 so that the dissolved oxygen concentration of the sewage 20 in the aeration tank 10 becomes the target DO value based on the measured DO value. And the inverter 58 (the rotation speed of the blower 48). Here, typically, priorities are determined for the on / off controlled blowers 42, 44, and 46, and the blowers to be operated according to the number of blowers to be operated and the priorities among the on / off controlled blowers 42, 44, and 46. Is determined.

  FIG. 2 is a diagram schematically showing aeration control (dissolved oxygen concentration control) by the controller 70 in the aeration equipment 100 shown in FIG. The horizontal axis in FIG. 2 indicates time, and the vertical axis indicates the amount of air supplied to the aeration tank 10 by the blower. In FIG. 2, "1" is the first blower (on / off control type) 42, "2" is the second blower (on / off control type) 44, "3" is the third blower (on / off control type) 46, "4" "" Indicates that the fourth blower (inverter control type) 48 is operating. For example, in FIG. 2, in a section marked with “1 + 4”, the first blower (on / off control type) 42 operates and the fourth blower (inverter control type) 48 rotates at the rotation speed designated by the main controller 60. (Output) indicates that it is operating.

  In FIG. 2, a section with “oxygen deficiency” indicates a section where the measured DO value is smaller than the target DO value (that is, a section where the air supply amount should be increased). In FIG. 2, a section with “appropriate” indicates a section where the measured DO value matches the target DO value (that is, a section where the air supply amount should be maintained). In FIG. 2, a section with “oxygen excess” indicates a section where the measured DO value is larger than the target DO value (that is, a section where the air supply amount should be reduced).

  In the example shown in FIG. 2, first, the fourth blower (inverter control type) 48 is activated, and the rotational speed is gradually increased to the maximum rotational speed (section A). If the time for which the fourth blower (inverter control type) 48 is continuously operated at the maximum rotational speed exceeds the specified time T (that is, the fourth blower (inverter control type) 48 alone is insufficient in the air supply amount). ), The first blower (on / off control type) 42 is activated (section B).

  Further, when the time during which the fourth blower (inverter control type) 48 is continuously operated at the maximum rotation speed in the section B exceeds the specified time T (that is, when the air supply amount is still insufficient), the second blower ( On-off control formula) 44 is activated (section C).

  Further, if the time during which the fourth blower (inverter control type) 48 is continuously operated at the maximum rotation speed exceeds the specified time T in the section C (that is, when the air supply amount is still insufficient), the third blower ( On-off control formula) 46 is activated (section D).

  In this way, the controller 70 causes the first to third blowers (on / off control type) 42 each time the time during which the fourth blower (inverter control type) 48 is continuously operated at the maximum rotational speed exceeds the specified time T. , 44 and 46, the number of blowers to be operated is increased.

  In the example shown in FIG. 2, in the initial section of section D, the measured DO value matches the target DO value (“proper”), and then the measured DO value is larger than the target DO value ( "Oxygen excess"). Therefore, the rotation speed of the fourth blower (inverter control type) 48 is reduced to the minimum rotation speed.

  If the time during which the fourth blower (inverter control type) 48 is continuously operated at the minimum rotation speed exceeds the specified time T in the section D (that is, when the air supply amount is excessive), the third blower (on / off control type) 46 is stopped (section E).

  In this way, the controller 70 causes the first to third blowers (on / off control type) 42 each time the time when the fourth blower (inverter control type) 48 is continuously operated at the minimum rotational speed exceeds the specified time T. , 44 and 46, the number of blowers to be operated is reduced.

  As described above, hunting of the control amount (dissolved oxygen concentration) is prevented by changing (increasing or decreasing) the number of operations of the first to third blowers (on / off control type) 42, 44, 46 after the specified time T has elapsed. be able to.

  In the example shown in FIG. 2, in the section E, in a state where the first blower (on / off control type) 42 and the second blower (on / off control type) 44 are operated, the measured DO value and the target DO value are matched. The rotational speed of the 4 blower (inverter control type) 48 is controlled.

  When the third blower (on / off control type) 46 is stopped, the rotation speed of the fourth blower (inverter control type) 48 may be increased in synchronization therewith. Similarly, when the first blower (on / off control type) 42 and the second blower (on / off control type) 44 are stopped, the rotation speed of the fourth blower (inverter control type) 48 may be increased in synchronism therewith. .

  The specified time T can be determined in consideration of the time constant of the feedback control system in the aeration equipment 100. The time constant can be evaluated as a delay time of a change in dissolved oxygen concentration with respect to on / off of the on / off controlled blowers 42, 44, 46 and a delay time of a change in dissolved oxygen concentration with respect to rotation speed control of the inverter controlled blower 48.

  When two or more inverter-controlled blowers are provided, the fine adjustment range of the air supply amount is widened.

It is a figure which shows typically the aeration equipment of suitable embodiment of this invention. It is a figure which shows typically aeration control (dissolved oxygen concentration control) in the aeration equipment 100 shown in FIG.

Explanation of symbols

10 Aeration tank 20 Sewage 30 Measuring instrument 42, 44, 46 On-off control blower 48 Inverter-controlled blower 52, 54, 56 On-off controller (switch)
58 Inverter 60 Main controller 70 Controller 80 Air diffuser (aerator)

Claims (2)

An aeration facility for aeration of sewage,
An aeration tank;
A measuring instrument for measuring the dissolved oxygen concentration of sewage in the aeration tank;
A plurality of on-off control type blowers for supplying air into the aeration tank;
An inverter-controlled blower for supplying air into the aeration tank;
Based on the dissolved oxygen concentration measured by the measuring device, the number of the plurality of on / off control blowers to be operated and the inverter control formula so that the dissolved oxygen concentration of the sewage in the aeration tank becomes the target dissolved oxygen concentration. A controller for controlling the rotational speed of the blower;
An aeration facility characterized by comprising:   The controller increases the number of the plurality of on / off control type blowers to be operated when the time during which the inverter control type blower is continuously operated at the maximum rotational speed exceeds a predetermined time, The aeration equipment according to claim 1, wherein the number of operating the plurality of on / off control blowers is reduced when the time of continuous operation at the minimum number of rotations exceeds a specified time.

Images