JP2000312896A - Waste water treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste water treatment apparatus easy in maintenance. SOLUTION: A waste water treatment apparatus is equipped with an aeration tank 1, a conduit 16 guiding water to be treated to the aeration tank 1, an oxygen enriched gas supply pipe 7, an ejector 6 for ejecting the oxygen enriched gas supplied through the oxygen enriched gas supply pipe 7 into the aeration tank 1 along with water to be treated supplied through the conduit 16, a dissolved oxygen concn. detector 15 detecting the concn. of dissolved oxygen in water to be treated in the conduit 16 and a control part 14 controlling the supply and stop of oxygen enriched gas to the ejector 6 on the basis of the concn. of dissolved oxygen detected by the detector 15. In this case, the dissolved oxygen concn. detector 15 is arranged so that the detection terminal thereof is exposed to the longitudinal flow of water to be treated in the conduit 16 when water to be treated is allowed to flow though the conduit 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for biologically treating wastewater such as food factory wastewater.

[0002]

2. Description of the Related Art A conventional wastewater treatment apparatus for treating industrial wastewater is shown in FIG. The wastewater treatment apparatus shown here is an activated sludge treatment apparatus, and has a schematic configuration including an aeration tank 1 for biologically treating organic matter in the water to be treated in the presence of oxygen, and a sedimentation tank 2 for separating sludge and treated water. Have been. In order to use this apparatus, water to be treated is introduced into the aeration tank 1 and oxygen is introduced into the water to be treated in the aeration tank 1 by blowing air into the aeration tank 1 through a diffuser 4 using a blower 3. Supply.

[0003]

However, in the above apparatus, when the load increases due to an increase in the concentration of organic substances in the water to be treated, the amount of oxygen supplied into the aeration tank 1 may be insufficient. An apparatus capable of increasing the amount of aeration by newly providing an aeration unit in the tank 1 or increasing the number of blowers has been proposed. As shown in FIG. 8, as a device provided with a new aeration unit, there is a device using an ejector. The apparatus shown here includes a circulating pump 5 for once pumping the water to be treated in the aeration tank 1 through a pipe 20, a pipe 16 for supplying the pumped water to the aeration tank 1, and a treatment pipe supplied through the pipe 16. An ejector 6 for ejecting water into the aeration tank 1 is provided. The suction force generated when the returned treated water is ejected from the ejector 6 into the aeration tank 1, through an pipe 7 connected to the ejector 6. 1 is supplied with air (outside air). In addition, there is also used one capable of forcibly sending air to the ejector 6 through the pipe 7 using a blower.

Further, as shown in FIGS. 9 and 10, an apparatus capable of supplying an oxygen-enriched gas such as pure oxygen to the ejector 6 instead of air is also used. The device shown in FIG. 9 comprises an oxygen-enriched gas supply 8 and tubes 27, 16
, The oxygen-enriched gas can be sent to the ejector 6.

In the apparatus shown in FIG. 10, a dissolved oxygen detector 15 for detecting the dissolved oxygen concentration in the aeration tank 1 and an oxygen-enriched gas supply source 8 based on the dissolved oxygen concentration detected by the detector 15 are provided. A control unit 24 for opening and closing the flow control valve 13 to adjust the supply amount of the oxygen-enriched gas. When the dissolved oxygen concentration detected by the detector 15 becomes less than a predetermined value, the control valve 13 is opened. The enriched gas is supplied into the aeration tank 1 so that the concentration of dissolved oxygen in the water to be treated in the aeration tank 1 can be maintained at a certain level or more. However, the above-described device has a problem in that maintenance of the dissolved oxygen concentration detector 15 requires a great deal of labor. Further, there is a problem that the cost required for the oxygen-enriched gas increases, and there has been a demand for improvement in the utilization efficiency of the oxygen-enriched gas. The present invention has been made in view of the above circumstances, and has the following objects. (1) To provide a wastewater treatment device that is easy to maintain. (2) To provide a wastewater treatment device capable of improving the utilization efficiency of oxygen-enriched gas.

[0006]

SUMMARY OF THE INVENTION A wastewater treatment apparatus according to the present invention comprises an aeration tank for biologically treating organic substances in the water to be treated in the presence of oxygen, and a treated water for guiding the water in the aeration tank. A conduit, an oxygen-enriched gas supply pipe for supplying the oxygen-enriched gas,
An ejector for ejecting the oxygen-enriched gas supplied through the supply pipe together with the water to be treated guided through the water treatment pipe into the aeration tank, and detecting a dissolved oxygen concentration in the water to be treated in the water treatment pipe; A dissolved oxygen concentration detector, and a control unit that controls supply and stop of the oxygen-enriched gas to the ejector based on the dissolved oxygen concentration detected by the detector. The detection end is provided so as to be exposed to the flow of the water to be treated in the longitudinal direction of the conduit when the water flows into the water to be treated. Further, the wastewater treatment device of the present invention
An aeration tank for biologically treating organic matter in the water to be treated in the presence of oxygen, a treated water conduit for guiding the treated water in the aeration tank, and a portion of the treated water in the treated water conduit. A branch pipe,
An oxygen-enriched gas supply pipe for supplying the oxygen-enriched gas, an ejector for ejecting the oxygen-enriched gas supplied through the supply pipe together with the water to be treated guided through the water to be treated pipe into the aeration tank; A dissolved oxygen concentration detector that detects a dissolved oxygen concentration in the water to be treated in the pipe, and a control unit that controls supply and stop of the oxygen-enriched gas to the ejector based on the dissolved oxygen concentration detected by the detector Wherein the dissolved oxygen concentration detector is installed such that when the water to be treated flows into the branch pipe, the detection end is exposed to the flow of the water to be treated in the longitudinal direction of the branch pipe. It can also be. It is preferable that one end of an outside air introduction pipe for introducing outside air into the supply pipe is connected to the oxygen-enriched gas supply pipe, and that the other end of the outside air introduction pipe is open to the atmosphere.

[0007]

1 and 2 show a first embodiment of a waste water treatment apparatus according to the present invention. The waste water treatment apparatus shown in FIG. Tank 1 for biological treatment, and sedimentation tank 2 for separating sludge resulting from biological treatment in the aeration tank 1 from treated water.
A circulating pump 5 for pumping the water to be treated in the aeration tank 1 through a water pipe 20, a treated water conduit 16 for guiding the treated water pumped by the circulation pump 5, an oxygen-enriched gas supply source 8, An oxygen-enriched gas supply pipe 7 for supplying the oxygen-enriched gas supplied from the oxygen-enriched gas supply source 8 and an oxygen-enriched gas supplied through the oxygen-enriched gas supply pipe 7
An ejector 6 for jetting into the aeration tank 1 together with the water to be treated guided through the water to be treated 16,
A dissolved oxygen concentration detector 15 for detecting the dissolved oxygen concentration in the water to be treated in the treatment water 6, and the supply and stop of the oxygen-enriched gas to the ejector 6 are controlled based on the dissolved oxygen concentration detected by the detector 15. The control unit 14 is provided.

An aeration tube 4 connected to a blower 3 is provided in the aeration tank 1, and air can be sent into the aeration tank 1 through the aeration tube 4 using the blower 3. The oxygen-enriched gas supply source 8 includes a liquefied oxygen-enriched gas storage container 9 and an evaporator 10 for vaporizing the liquefied oxygen-enriched gas taken out of the container 9. As the oxygen-enriched gas, oxygen-enriched air whose oxygen concentration has been increased by a conventionally known adsorption method or the like, or pure oxygen can be used. Reference numeral 11 denotes an on-off valve, reference numeral 12 denotes a pressure reducing valve, and reference numeral 13 denotes a flow control valve for controlling the flow of the oxygen-enriched gas.

In the wastewater treatment apparatus according to the present embodiment, the dissolved oxygen concentration detector 15 is capable of outputting a detection signal corresponding to the dissolved oxygen concentration in the water to be treated to the control unit 14. An electrochemical detector provided with an electrode and an oxygen permeable membrane separating the electrode and the water to be treated can be used. The dissolved oxygen concentration detector 15 is configured such that when the detection end 15a having the oxygen permeable membrane flows the water to be treated into the conduit for the water to be treated, the longitudinal direction of the water to be treated (the direction indicated by the arrow in FIG. 2). To the treated water conduit 16 so that the detection end 15a is located at the boundary of the treated water circulation space 16a inside the conduit indicated by the broken line in the drawing or at the detection end 15a. The concentration of dissolved oxygen in the water to be treated in the water conduit 16 can be detected.

The control unit 14 opens and closes the control valve 13 of the oxygen-enriched gas supply source 8 based on the detection signal output from the dissolved oxygen concentration detector 15, whereby the oxygen-enriched gas is supplied to the ejector 6. Supply and stop can be controlled.

The oxygen-enriched gas supply pipe 7 has an outside air introduction pipe 1
7 is connected to one end. The outside air introduction pipe 17 introduces outside air into the oxygen-enriched gas supply pipe 7 and supplies the outside air to the supply pipe 7.
To the ejector 6 through the other end 1
7b is open to the atmosphere. The outside air introduction pipe 17 is provided with a check valve 17 a for preventing a gas flow from one end side to the other end side in the pipe 17.

Next, an example of a method of using the above device will be described. First, the control unit 14 previously supplies the oxygen-enriched gas to the ejector 6 by opening the control valve 13 when the dissolved oxygen concentration in the water to be treated in the water pipe 16 falls below the lower limit of the predetermined range. The control valve 13 is closed so that the supply of the oxygen-enriched gas is stopped when the concentration of dissolved oxygen in the water to be treated exceeds the upper limit of the predetermined range. The upper limit is preferably 4 to 7 mg / L, and the lower limit is preferably 3 to 6 mg / L.

Next, the water to be treated is introduced into the aeration tank 1, the circulating pump 5 is operated, and the water to be treated in the aeration tank 1 collected through the water intake pipe 20 is supplied to the treatment water conduit 16.
And ejected into the aeration tank 1 by the ejector 6. The flow rate of the water to be treated flowing in the water to be treated conduit 16 in the longitudinal direction of the conduit is preferably 0.8 m / sec or more. The pressure in the oxygen-enriched gas supply pipe 7 decreases with the ejection of the water to be treated from the ejector 6.

The dissolved oxygen concentration detector 15 has a detection end 15a.
Is installed so as to be exposed to the to-be-treated water flowing in the to-be-treated water conduit 16, so that when the sludge adheres to the detection end 15a, the sludge is immediately washed away by the to-be-treated water. For this reason, the sludge in the water to be treated hardly adheres to the detection end 15a.

The dissolved oxygen concentration detector 15 detects the concentration of dissolved oxygen in the water to be treated flowing through the treated water conduit 16. When the detected dissolved oxygen concentration is less than the lower limit of the predetermined range, the control valve 13 opens the control valve 13 and the oxygen-enriched gas is supplied from the oxygen-enriched gas supply source 8 to the ejector 6 at a predetermined flow rate. Supplied to It is preferable that the flow rate of the oxygen-enriched gas when the control valve 13 is in the open state is set so that the pressure in the water pipe 16 to be treated becomes about atmospheric pressure or less. The oxygen-enriched gas supplied to the ejector 6 is ejected from the ejector 6 together with the water to be treated introduced into the ejector 6 from the conduit 16. Thereby, oxygen is supplied to the water to be treated in the aeration tank 1, and the concentration of dissolved oxygen in the water to be treated is increased.

When the pressure in the oxygen-enriched gas supply pipe 7 is lower than the atmospheric pressure, the outside air is sucked into the oxygen-enriched gas supply pipe 7 through the outside air introduction pipe 17 whose other end 17b is open to the atmosphere. This outside air is ejected by the ejector 6 together with the oxygen-enriched gas.
Introduced within. When the pressure in the oxygen-enriched gas supply pipe 7 has reached the atmospheric pressure, introduction of outside air from the outside air introduction pipe 17 to the supply pipe 7 does not occur.

When the dissolved oxygen concentration in the water to be treated in the treated water conduit 16 exceeds the upper limit of the predetermined range, the control valve 13 is closed by the control unit 14 and the oxygen-enriched gas is supplied to the ejector 6. Supply stops. When the supply of the oxygen-enriched gas is stopped, the pressure in the oxygen-enriched gas supply pipe 7 becomes negative due to the ejection of the water to be treated from the ejector 6, and the outside air introduction pipe 17
The amount of outside air introduced into the oxygen-enriched gas supply pipe 7 through the gas supply port immediately increases until the internal pressure of the supply pipe 7 becomes approximately atmospheric pressure.

As described above, the oxygen-enriched gas and / or the outside air are supplied to the ejector 6 in an amount corresponding to the suction force generated when the water to be treated is jetted. Therefore, the total flow rate of the gas supplied to the ejector 6 becomes substantially constant regardless of whether the oxygen-enriched gas is supplied or not, and the ratio of the gas amount introduced into the ejector 6 to the liquid amount (hereinafter referred to as gas-liquid ratio) ) Is kept almost constant.

In the above-mentioned waste water treatment apparatus, when the dissolved oxygen concentration detector 15 flows the water to be treated into the conduit 16 for treated water, the detection end 15a changes the flow in the conduit 16 for the treated water. Because it is installed to be exposed, the detection end 15a
Is exposed to the water to be treated flowing at a higher flow rate (for example, a flow rate ten and several times higher) than when the dissolved oxygen concentration detector 15 is installed in the aeration tank 1. Therefore, the detection end 15
The sludge in the water to be treated hardly adheres to a. Therefore, it is possible to reduce the frequency of cleaning of the dissolved oxygen concentration detector 15 and replacement of parts, thereby facilitating maintenance. Further, the accuracy of the detector 15 can be improved.

Further, since the water to be treated flowing in the conduit 16 is always mixed in the pipe 16, non-uniformity of the dissolved oxygen concentration hardly occurs. Further, since the water to be treated in the aeration tank 1 flows into the conduit 16 sequentially, the concentration of dissolved oxygen in the water to be treated in the aeration tank 1 can be immediately detected. Therefore, the concentration of dissolved oxygen in the water to be treated in the aeration tank 1 can be accurately detected.

By the way, generally in an ejector,
It is known that when gas is supplied in an amount corresponding to the suction force generated when a liquid is ejected, that is, when the gas supply amount is the same as that in natural suction, the gas dissolution efficiency is highest. . In the above wastewater treatment apparatus, the outside air introduction pipe 17 whose other end 17b is open to the atmosphere is connected to the oxygen-enriched gas supply pipe 7.
When the pressure of the oxygen-enriched gas in the treated water conduit 16 is lower than the atmospheric pressure, the outside air is introduced into the supply pipe 7 through the outside air introduction pipe 17, and the total amount of gas supplied to the ejector 6 is The flow rate is a value corresponding to the suction force generated when the water to be treated is jetted. For this reason, the gas-liquid ratio in the ejector 6 is set to substantially the same value as in the case of natural suction, and the gas dissolving efficiency in the water to be treated in the aeration tank 1 can be maximized. Therefore, the utilization efficiency of oxygen can be improved, and the amount of oxygen used can be reduced. Also, when the supply of oxygen-enriched gas decreases, the flow rate of outside air increases immediately,
It is possible to prevent a temporary decrease in the total flow rate of the gas supplied to the ejector 6, keep this total flow rate constant, and maintain a high oxygen utilization efficiency.

FIG. 3 shows a second embodiment of the waste water treatment apparatus according to the present invention. The waste water treatment apparatus shown in FIG. Is connected to the aeration tank 1, and a dissolved oxygen concentration detector 15 is attached to the branch pipe 18, which is different from the wastewater treatment apparatus of the first embodiment. The branch pipe 18 is provided with an on-off valve 18a on the side of the water pipe 16 to be treated, that is, on the upstream side of the position where the dissolved oxygen concentration detector 15 is attached.
Is provided. In the wastewater treatment apparatus of the present embodiment, the dissolved oxygen concentration detector 15
The detection end 15a is attached to the branch pipe 18 such that the detection end 15a is exposed to the flow of the water to be treated in the longitudinal direction of the branch pipe.

When the wastewater treatment apparatus of the present embodiment is used, a part of the water to be treated flowing through the treated water conduit 16 flows into the branch pipe 18 and is sent into the aeration tank 1 through the branch pipe 18. To be able to The flow rate of the water to be treated flowing through the branch pipe 18 is preferably set to 0.8 m / sec or more.

At this time, the dissolved oxygen concentration detector 15 detects the concentration of dissolved oxygen in the water to be treated flowing through the branch pipe 18. In the apparatus of the present embodiment, similarly to the apparatus of the first embodiment, since the detection end 15a of the dissolved oxygen concentration detector 15 is exposed to the water to be treated flowing at a high flow rate, the sludge of the detection end 15a Adhesion hardly occurs. Further, since the outside air introduction pipe 17 is provided, the gas-liquid ratio in the ejector 6 can be set to substantially the same value as in the case of natural intake, and the oxygen utilization efficiency can be improved. Therefore, similarly to the apparatus of the first embodiment, maintenance can be facilitated, dissolved oxygen concentration detection accuracy can be improved, and oxygen consumption can be reduced.

Further, in the wastewater treatment apparatus of the present embodiment,
An effect is obtained that maintenance work such as replacement or cleaning of the dissolved oxygen concentration detector 15 can be further facilitated. This is because when performing maintenance work such as replacement or cleaning of the dissolved oxygen concentration detector 15, the on-off valve 18 a is closed to stop the flow of the water to be treated into the branch pipe 18. This is because it is possible to prevent troubles such as leakage of the water to be treated at the time of detachment or attachment to the apparatus.

FIG. 4 shows a third embodiment of the wastewater treatment apparatus according to the present invention. This wastewater treatment apparatus is different from the wastewater treatment apparatus in that the oxygen-enriched gas supply pipe 27 is connected to the water pipe 16 to be treated. It is different from the wastewater treatment device of the first embodiment. The oxygen-enriched gas supply pipe 27 is connected to the treated water conduit 16 on the ejector 6 side, that is, downstream of the detector 15 mounting position. In this device, the oxygen-enriched gas is supplied to the ejector 6 from the supply pipe 27 via the conduit 16. In the above device,
As in the apparatus of the first embodiment, maintenance can be facilitated, dissolved oxygen concentration detection accuracy can be improved, and oxygen consumption can be reduced.

In each of the above embodiments, the control valve 13 is opened to supply the oxygen-enriched gas to the ejector 6 when the concentration of dissolved oxygen in the water to be treated falls below the lower limit of the predetermined range. When the control value exceeds the upper limit of the predetermined range, the control valve 13 is closed, and the supply of the oxygen-enriched gas is stopped. In the present invention,
The following usage method can also be adopted. That is, the control unit 14 controls the opening degree of the control valve 13 in accordance with the dissolved oxygen concentration in the water to be treated detected by the dissolved oxygen concentration detector 15, and controls the oxygen enrichment from the oxygen-enriched gas supply source 8. The gas supply amount may be set to change steplessly in accordance with the concentration of dissolved oxygen in the water to be treated. An example of such control is a PID based on a detection signal from the detector 15.
Control and the like.

As described above, by setting the control unit 14 so that the supply amount of the oxygen-enriched gas is steplessly set to an amount corresponding to the dissolved oxygen concentration in the water to be treated, the supply amount of the oxygen-enriched gas is rapidly increased. Changes can be prevented. For this reason, the amount of gas supplied to the ejector 6 is accurately maintained at a predetermined value,
As compared with the ON-OFF control, the gas-liquid ratio in the ejector 6 can be more accurately kept constant.

FIG. 5 shows a fourth embodiment of the waste water treatment apparatus according to the present invention.
7 is different from the wastewater treatment apparatus of the first embodiment in that an air flow control valve 19 connected to the control unit 14 is provided. In this device, the control unit 14 is configured to be able to adjust the opening degrees of the control valves 13 and 19 in accordance with the concentration of dissolved oxygen in the water to be treated detected by the detector 15. The supply amounts of the oxygen-enriched gas and air can be set to arbitrary values according to the dissolved oxygen concentration in the water.

This device can be used, for example, in the following manner. That is, the concentration of dissolved oxygen in the water to be treated in the aeration tank 1 is reduced by opening and closing the control valve 13 in accordance with the concentration of dissolved oxygen in the water to be treated in the conduit 16 to be treated. While maintaining the predetermined range, the control valve 19 is adjusted according to the flow rate of the oxygen-enriched gas, and the ejector 6 is controlled.
So that the total flow rate of the gas supplied to the gas is constant.

In the above-described apparatus, as in the apparatus of the first embodiment, maintenance can be facilitated, the accuracy of dissolved oxygen concentration detection can be improved, and the amount of oxygen used can be reduced. Further, in the above device, since the outside air flow rate is adjusted by the control valve 19, the flow rate of the outside air supplied from the outside air introduction pipe 17 can be accurately set. For this reason, the total flow rate of the gas supplied to the ejector 6 can be more accurately maintained at a predetermined value, and the gas-liquid ratio in the ejector 6 can be made constant with high accuracy. Therefore, the utilization efficiency of oxygen in the aeration tank 1 can be further improved, and the amount of oxygen used can be further reduced.

The wastewater treatment apparatus shown in FIG. 6 shows a fifth embodiment of the wastewater treatment apparatus of the present invention. In the apparatus shown here, a three-way valve 21 is provided in the oxygen-enriched gas supply pipe 7,
The third embodiment is different from the wastewater treatment apparatus of the first embodiment in that the outside air introduction pipe 17 is connected to the three-way valve 21 and the control unit 14 is connected to the three-way valve 21. In the apparatus shown here, only one of the oxygen-enriched gas from the oxygen-enriched gas supply source 8 and the outside air from the outside air introduction pipe 17 is supplied to the ejector 6 through the oxygen-enriched gas supply pipe 7. It is configured to be introduced into.

The above device can be used in the following manner, for example. That is, when the dissolved oxygen concentration of the water to be treated in the water pipe 16 falls below the lower limit of the predetermined range, no outside air is introduced from the outside air introduction pipe 17 and only the oxygen-enriched gas is supplied to the ejector 6. The control unit 14 is set so that Further, the control unit 14 is controlled so that the supply of oxygen-enriched gas does not occur when the dissolved oxygen concentration in the water to be treated exceeds the upper limit of the predetermined range, and only the outside air is introduced into the supply pipe 7 through the outside air introduction pipe 17. Set to. It is preferable that the gas flow rate during the supply of the oxygen-enriched gas is set so that the inside of the supply pipe 7 is substantially at atmospheric pressure.

In the above device, when the dissolved oxygen concentration detected by the detector 15 is less than the lower limit of the predetermined range, the outside air is not introduced from the outside air introducing pipe 17 and only the oxygen-enriched gas is discharged from the ejector 6. Supplied to If the dissolved oxygen concentration exceeds the upper limit of the predetermined range, the supply of the oxygen-enriched gas is stopped and only the outside air is introduced into the ejector 6 through the outside air introduction pipe 17. In the above device, the first
As in the case of the apparatus of the embodiment, maintenance can be facilitated, dissolved oxygen concentration detection accuracy can be improved, and oxygen consumption can be reduced.

[0035]

EXAMPLES Example 1 Wastewater from a food factory (average BOD: 1)
000 mg / L) was treated as follows using a wastewater treatment device similar to that shown in FIGS. 1 and 2. Aeration tank 1
As is used as the capacitor 200 meters ^3, the ejector 6
Was installed at the bottom of the aeration tank 1, and the water to be treated and the oxygen-enriched gas were supplied into the aeration tank 1 through the ejector 6. Pure oxygen was used as the oxygen-enriched gas. That is, when the dissolved oxygen concentration in the water to be treated falls below 5 mg / L, the control valve 13 is opened and the oxygen-enriched gas is supplied to the ejector 6 through the supply pipe 7 and the dissolved oxygen concentration is reduced. When the pressure exceeds 6 mg / L, the control valve 13 is closed so that the supply of the oxygen-enriched gas from the oxygen-enriched gas supply source 8 is stopped.
The water is introduced into the aeration tank 1 at 50 m ³ / d, the circulating pump 5 is operated, and the water to be treated in the aeration tank 1 collected through the water intake pipe 20 is supplied to the ejector 6 through the treated water conduit 16. 6 and spouted into the aeration tank 1. The flow rate of the to-be-treated water flowing through the intake pipe 20 and the to-be-treated water conduit 16 was set to 0.8 m / sec. The above treatment test was performed for three months.

Example 2 The same waste water as used in Example 1 was treated using a waste water treatment apparatus shown in FIG. The flow rate of the water to be treated flowing through the branch pipe 18 was set to 1 m / sec. Other conditions were the same as in Example 1.

(Comparative Example) The same waste water as used in Example 1 was treated using the conventional apparatus shown in FIG. The dissolved oxygen concentration detector 15 was installed such that the detection end was always immersed in the water to be treated in the aeration tank 1. Other conditions were the same as in Example 1.

As a result of the above-mentioned treatment tests, it was found that the amount of oxygen used was approximately 50% when the devices of Examples 1 and 2 were used as compared with the case where the device of the comparative example was used. In the treatment tests using the devices of Examples 1 and 2, the dissolved oxygen concentration of the water to be treated in the aeration tank 1 was approximately 4.0 throughout the test period.
It was confirmed that it was kept within the range of 5 mg / L or more. After the test was completed, the detection end of the dissolved oxygen concentration detector was visually observed.
The sludge did not adhere to the detection end of the apparatus of the comparative example, whereas the sludge did not adhere to the detection end.

[0039]

As described above, in the wastewater treatment apparatus according to the present invention, when the dissolved oxygen concentration detector flows the to-be-treated water into the to-be-treated water conduit, the dissolved oxygen concentration detector is used. Since the detection end is installed so as to be exposed to the flow of the water to be treated, sludge in the water to be treated hardly adheres to the detection end. Therefore, maintenance of the dissolved oxygen concentration detector can be facilitated, and the detection accuracy can be increased. In addition, by providing an outside air introduction pipe to the oxygen-enriched gas supply pipe, an amount of oxygen-enriched gas and / or outside air is supplied to the ejector in accordance with the pressure in the supply pipe, and the gas-liquid ratio in the ejector is set to the value of natural intake. By making the value approximately the same as that at the time, the utilization efficiency of oxygen can be improved and the amount of oxygen used can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of a wastewater treatment device of the present invention.

FIG. 2 is an enlarged view of a main part of the wastewater treatment device shown in FIG.

FIG. 3 is a schematic configuration diagram showing a second embodiment of the wastewater treatment device of the present invention.

FIG. 4 is a schematic configuration diagram showing a third embodiment of the wastewater treatment device of the present invention.

FIG. 5 is a schematic configuration diagram showing a fourth embodiment of the wastewater treatment device of the present invention.

FIG. 6 is a schematic configuration diagram showing a fifth embodiment of the wastewater treatment apparatus of the present invention.

FIG. 7 is a schematic configuration diagram illustrating an example of a conventional wastewater treatment device.

FIG. 8 is a schematic configuration diagram showing another example of a conventional wastewater treatment device.

FIG. 9 is a schematic configuration diagram showing still another example of a conventional wastewater treatment device.

FIG. 10 is a schematic configuration diagram showing still another example of a conventional wastewater treatment device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Aeration tank, 6 ... Ejector, 7 ... Oxygen-enriched gas supply pipe, 8 ... Oxygen-enriched gas supply source, 13 ... Control valve, 15
... dissolved oxygen concentration detector, 15a ... detection end, 16 ... treated water conduit, 17 ... outside air introduction pipe, 17b ... other end, 18
... Branch pipes

Claims (3)

[Claims] 1. An aeration tank for biologically treating organic matter in treated water in the presence of oxygen, a treated water conduit for introducing treated water in the aeration tank, and an oxygen-rich gas for supplying an oxygen-enriched gas. Gas supply pipe, an ejector for ejecting the oxygen-enriched gas supplied through the supply pipe into the aeration tank together with the water to be treated guided through the water to be treated pipe, and an ejector for supplying the oxygen-enriched gas into the aeration tank. A dissolved oxygen concentration detector that detects a dissolved oxygen concentration, and a control unit that controls supply and stop of the oxygen-enriched gas to the ejector based on the dissolved oxygen concentration detected by the detector. Is a wastewater treatment apparatus characterized in that the detection end is installed so as to be exposed to the flow of the water to be treated in the longitudinal direction of the pipe when the water to be treated flows into the water pipe. 2. An aeration tank for biologically treating organic matter in the water to be treated in the presence of oxygen, a treated water conduit for guiding the treated water in the aeration tank, and a treated water in the treated water conduit. A branch pipe for guiding a part of the oxygen-enriched gas, an oxygen-enriched gas supply pipe for supplying the oxygen-enriched gas, and aeration of the oxygen-enriched gas supplied through the supply pipe together with the water to be treated introduced through the water-treatment pipe. An ejector that jets into the tank, a dissolved oxygen concentration detector that detects the concentration of dissolved oxygen in the water to be treated in the branch pipe, and a supply of oxygen-enriched gas to the ejector based on the dissolved oxygen concentration detected by the detector The dissolved oxygen concentration detector is installed such that the detection end is exposed to the flow of the water to be treated in the longitudinal direction of the branch pipe when the water to be treated flows into the branch pipe. Wastewater treatment equipment characterized by being carried out 3. The wastewater treatment apparatus according to claim 1, wherein one end of an outside air introduction pipe for introducing outside air into the supply pipe is connected to the oxygen-enriched gas supply pipe, and the other end of the outside air introduction pipe. A wastewater treatment apparatus, wherein the wastewater treatment apparatus is open to the atmosphere.