JP4082556B2 - Nitrogen removal equipment in membrane separation type oxidation ditch - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is a nitrogen removal device in a membrane separation type oxidation ditch, in particular, sewage such as sewage containing nitrogen is biologically treated using an oxidation ditch in which a membrane separation device is installed while washing the submerged membrane. The present invention relates to a nitrogen removing apparatus in a membrane separation type oxidation ditch in which nitrogen is biologically removed by the action of nitrifying bacteria and denitrifying bacteria in sludge.
[0002]
[Prior art]
Conventionally, in order to treat sewage flowing into small- and medium-sized sewage treatment plants, sewage flows into an activated sludge aeration tank, and this is aerated and stirred to perform biological treatment, especially the oxidation ditch method. Is often adopted.
In addition, the recently developed membrane separation activated sludge method using a submerged membrane immerses a membrane separator in a reaction tank and discharges treated water with a suction pump. Thus, a high-pressure pump is not used, the running cost is low, and treated water that is clearer than the oxidation ditch method can be obtained.
[0003]
[Problems to be solved by the invention]
However, when an immersion membrane is provided, in order to prevent sludge from adhering to the membrane surface, it is necessary to clean the membrane surface by blowing air from an air diffuser provided below the immersion membrane. Since air filtration cannot be performed with a submerged membrane when the working air is stopped, the air is usually diffused almost continuously.
For this reason, when an immersion membrane is used in a single tank type reaction vessel such as an oxidation ditch, aeration is always performed with cleaning air, and it is difficult to create an anaerobic state in the same tank. There is a problem that it is difficult to remove nitrogen by a conventional treatment method using a single tank that removes nitrogen in wastewater by a combination of nitrification under anaerobic conditions and denitrification under anaerobic conditions.
[0004]
In view of the problem of the nitrogen removal method in the conventional membrane separation type, the present invention uses a membrane separation type oxidation ditch and generates an aerobic state and an anaerobic state in the circulation channel, and this aerobic state An object of the present invention is to provide a nitrogen removal apparatus in a membrane separation type oxidation ditch in which nitrification and denitrification can be performed in the oxidation ditch by a combination of an anaerobic state.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the nitrogen removing apparatus in the membrane separation type oxidation ditch according to the present invention is an oxidation ditch having a short circulation channel in which the circulation channel is temporally switched between an aerobic state and an anaerobic state . The water flow adjusting wall disposed in the center of the tank, the membrane separation device installed in the water flow adjusting wall, the aeration pipe for cleaning the membrane of the membrane separation device, and the water flow while stirring and aeration of the sewage in the circulation channel It consists of an aeration stirrer arranged to generate, and the water flow control wall opens and closes the sludge mixture intake at a part of the bottom, and the upper part opens and closes in synchronization with anaerobic operation and aerobic operation by the aeration stirrer A discharge port for the sludge mixed liquid is provided , and the discharge port is closed during anaerobic operation, and the discharge port is opened during an aerobic operation .
[0006]
The nitrogen removing device in the membrane separation type oxidation ditch of the present invention has a membrane separation device immersed in the central part of the tank, and the membrane is washed by air diffused from an air diffuser provided at the bottom of the membrane separation device, thereby adjusting the water flow. The sludge mixed liquid is taken in from the inlet provided at a part of the bottom of the wall, the outlet with opening / closing device for discharging is provided at a part of the upper part, and the aeration stirrer provided outside the water flow adjusting wall is preferred for anaerobic operation. Since the air operation is repeated alternately, by closing the discharge port during anaerobic operation and performing only agitation using an aeration stirrer, even if the inside of the water flow adjusting wall is in an aerobic state, oxidation is performed. The entire channel of the ditch can be anaerobic, and during aerobic operation, by opening the outlet, it is diffused for membrane cleaning, and in the sludge mixture while rising in the membrane separator. Oxygen dissolved in water It flows out from the discharge outlet provided at the upper part of the adjustment wall to the water channel part of the oxidation ditch together with the sludge mixture, and the aeration stirrer performs aeration operation to make up for the lack of oxygen. Since aeration oxygen is combined and the water channel is short, the whole water channel becomes aerobic, and the oxygen dissolved by the membrane cleaning air is adjusted to flow into the oxidation ditch water channel, By changing the conditions of aerobic / anaerobic over time, nitrification / denitrification can be promoted and nitrogen in the sewage can be removed.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a nitrogen removing device in a membrane separation type oxidation ditch of the present invention will be described based on the drawings.
[0008]
FIG. 1 shows a reference example in which nitrogen is removed from sewage using an oxidation ditch having a long channel length.
In this reference example, a water flow adjusting wall 3 serving as a partition wall is disposed at the center of the oxidation ditch water tank 1, whereby two long water channels whose ends are connected in the oxidation ditch water tank 1 are parallel to each other. In this way, the circulating water channels 11 and 12 are formed, and in the water flow adjusting wall 3, one united immersion type membrane separation device 2 is connected or a plurality of units are connected as in the illustrated reference example. Installed.
A suction pump 21 is connected to the membrane separation apparatus 2 outside the oxidation ditch water tank 1, and the treated water that has been treated by filtering the sludge mixed solution in the membrane separation apparatus 2 is drained.
The membrane separation device 2 is not provided with the suction pump 21 and is provided with a treatment water tank (not shown), and the membrane separation is performed by gravity filtration due to the water level difference formed between the membrane separation device 2 and the treatment water tank. A method of sucking and draining the treated water in the apparatus 2 can also be used.
[0009]
A membrane cleaning air diffuser 5 is disposed at a lower position of the membrane separator 2, and the membrane cleaning air is always discharged from the air diffuser 5 to the membrane surface of the membrane separator 2. Remove adhering sludge.
[0010]
The two long water channels connected in the end portion formed in the oxidation ditch water tank 1 are connected at the end portions to form the circulation water channels 11 and 12, but a part of them becomes an aerobic zone. Make the rest into an anaerobic zone.
The aerobic zone and the anaerobic zone are mainly determined by the position where the aerator 4 is provided. In the present reference example, the aerator 4 is provided so that the downstream side of the water channel 11 provided by the supply of oxygen and water flow is The aerobic zone is generally formed, and the downstream side of the water channel 12 that follows is generally an anaerobic zone.
In addition, the aerator 4 is not particularly limited, but any aerator suitable for the screw type and other oxidation ditch methods as illustrated can be applied.
When the amount of air for membrane cleaning discharged from the air diffuser 5 below the membrane separation device 2 is large and all of the necessary oxygen can be supplied by the air for membrane cleaning, the aerator is supplied. It is also possible to use a stirrer instead.
[0011]
The water flow adjusting wall 3 disposed to form a circulation channel in the center of the oxidation ditch water tank 1 is disposed so as to surround the periphery of the membrane separation device 2 and to a position higher than the water surface of the circulation channel. A circulation channel is formed outside the water flow adjusting wall 3, and a sludge mixed liquid C intake port 30 is formed at the bottom of the water flow adjusting wall 3, near the upper water surface, and in the vicinity of the aerator 4. A sludge mixed liquid outlet, for example, a slit 31 is provided at a position, preferably upstream of the aerobic zone.
As a result, a part of the sludge mixed solution is taken into the bottom of the water flow adjusting wall 3 from the inside of the circulation channel, filtered by the membrane separation device 2, and only the treated water is discharged outside the oxidation ditch water tank 1 by the suction pump 21. The sludge mixed liquid in a state where sludge is mixed and a part of the air supplied through the air diffuser is dissolved and aerated is discharged from the slit 31 into the aerobic zone in the circulation channel. In this reference example, the slit 31 is disposed in the vicinity of the aerator 4 upstream of the aerobic zone, but the intake 30 for the sludge mixture C is at the bottom of the circulation channel, Any aerobic zone or anaerobic zone may be used as long as it is at the bottom of the adjustment wall 3.
[0012]
The operation of the present invention will be described below. Nitrogen components contained in the sewage A flowing into the oxidation ditch water tank 1 are in an ammonia state and an organic state. In order to remove nitrogen, the aeration zone in the oxidation ditch water tank 1 is first aerated in an aerobic zone. It is oxidised to nitrate by the action of nitrifying bacteria. Sewage that has passed through the aerobic zone is guided to the anaerobic zone.
[0013]
Next, because the anaerobic zone is in an anaerobic state, denitrifying bacteria use the organic matter in the sewage as an energy source, while reducing nitrate nitrogen to nitrogen molecules, so that nitrogen gas is released into the atmosphere. Dissipate.
In this case, in the oxidation ditch water tank 1 having a long water channel length, dissolved oxygen contained in the sludge mixed solution C is consumed by respiration of microorganisms while flowing through the water channel. The dissolved oxygen contained in the sludge mixed liquid C that is vaporized and discharged from the slit 31 to the vicinity of the aerator 4 is mixed with the dissolved oxygen supplied by the aerator 4, but disappears while flowing through the aerobic zone. .
Therefore, the sewage A that has flowed in passes through the aerobic zone with a lot of dissolved oxygen and the anaerobic zone without the dissolved oxygen during one round of the circulation channel from the aerator 4 and repeats this. Even if air is constantly diffused from the trachea 5, both nitrification and denitrification can proceed in the same oxidation ditch water tank 1.
[0014]
2 to 3 show an embodiment of the present invention . In this embodiment, the circulation channel is relatively short, and even in the case of the oxidation ditch water tank 10 having a short channel length, by switching the circulation channel between an aerobic state and an anaerobic state in time, Similarly to the case of the long oxidation ditch water tank 1, nitrogen is removed from the sewage using the same oxidation ditch water tank 1.
[0015]
A water flow adjusting wall 3 is disposed in the center of the oxidation ditch water tank 1, thereby forming circulation water channels 11 and 12 in which two water channels are parallel to each other in the tank. Similarly to the example, the immersion type membrane separation apparatus 2 connected with the suction pump 21 is installed, and the sludge mixed solution is filtered by the membrane separation apparatus 2 to drain the treated water.
A membrane cleaning air diffuser 5 is disposed at a lower position of the membrane separator 2, and the membrane cleaning air is always discharged from the air diffuser 5 to the membrane surface of the membrane separator 2. Remove adhering sludge.
[0016]
The water flow adjusting wall 3 is disposed so as to surround the periphery of the membrane separation device 2 and to a position higher than the water surface of the circulating water channel. A circulating water channel is formed outside the water flow adjusting wall 3, and the water flow adjusting wall is provided. 3 is provided with an intake port 30 for taking the sludge mixed liquid C in the circulation channel into the water flow adjusting wall 3, and a sludge mixed liquid discharge port that can be opened and closed near the upper water surface, for example, an opening / closing device. Each incorporated slit 32 is provided.
The sludge mixed-solution inlet 30 can be provided at an arbitrary position as long as it is located at some distance from the slit 32 with an opening / closing device.
Further, an aeration stirrer 4 is provided in the water channel 11, and is configured to supply oxygen and a water flow into the water channel. The aeration stirrer 4 is not particularly limited, but any aeration stirrer suitable for the screw type and other oxidation ditch methods as illustrated can be applied.
[0017]
The slit 32 formed near the water surface near the upper part of the water flow adjusting wall 3 and toward the aeration stirrer 4 side is not particularly limited, and the mechanism for opening and closing is a front and rear of a lid-like plate that closes the slit, or A mechanism that slides left and right, a mechanism that automatically opens and closes by rotating a grid-like plate such as a louver, and the like can be employed. The opening / closing device incorporated in the slit 32 is configured to automatically perform the opening / closing operation in conjunction with the operation of the aeration stirrer 4.
[0018]
As described above, in the oxidation ditch water tank 10 having a short water channel length, the aerobic time zone and the anaerobic time zone are alternately repeated in the circulation water channel in order to remove nitrogen contained in the sewage A. Like that.
Moreover, since it is preferable to maintain the circulating water flow in the oxidation ditch water tank 10 even in the anaerobic time zone, the aeration stirrer 4 uses an apparatus capable of anaerobic stirring, or a facility configured with a stirrer and a diffuser. You can also.
[0019]
The operation of the above embodiment will be described below. Nitrogen components contained in the sewage A flowing into the oxidation ditch water tank 10 are in an ammonia state and an organic state. In order to remove nitrogen, the oxidation ditch water tank 10 is first aerated by being aerated. When sewage flows down through the circulation channel, it is oxidized to nitrate by the action of nitrifying bacteria, and the sewage treated in this aerobic time zone is then anaerobic, and denitrifying bacteria remove organic matter in the sewage. While being used as an energy source, nitrate nitrogen is reduced to nitrogen molecules, which are then diffused into the atmosphere as nitrogen gas.
[0020]
The treatment in the aerobic time zone in the oxidation ditch water tank 10 is to clean the membrane surface of the membrane separation device 2 by aeration from the diffusion tube, and to operate the aeration stirrer with the opening / closing device incorporated in the slit 32. The operation is performed in such a manner that the sewage in which oxygen is dissolved by this aeration is discharged into the circulation channel through the released slit 32. Thereby, sufficient oxygen can be supplied into the water channel by driving the aeration stirrer and aeration from the aeration tube, and an aerobic state can be obtained.
When sewage flows down through the aerobic circulation channel, it is oxidized to nitrate by the action of nitrifying bacteria.
[0021]
However, when nitrification and denitrification are performed in the oxidation ditch water tank 10 having a short channel length, it is necessary to alternately repeat the aerobic time zone and the anaerobic time zone because dissolved oxygen does not disappear while flowing through the water channel.
The two conditions of aerobic and anaerobic can be created by the operation of the aeration stirrer 4, but the anaerobic operation time zone is opened and closed to prevent the anaerobic condition from being hindered by the dissolved oxygen supplied by the membrane cleaning. The operation is performed by closing the slit 32 with the device.
In addition, in order to continue the membrane filtration by operating the membrane separation device 2 even in the anaerobic time zone, an amount of the sludge mixed solution C corresponding to the treated water B filtered by the membrane is the inlet of the sludge mixed solution. 30 flows into the interior of the water flow adjusting wall 3. Although the membrane cleaning is continued even during the anaerobic time zone, the dissolved oxygen concentration inside the water flow adjusting wall 3 gradually increases due to the aeration for cleaning, but the slit 32 is closed, so the oxidation ditch water tank Ten waterway portions can be kept in an anaerobic state.
[0022]
After performing anaerobic operation for a predetermined time using a control timer or the like in this way, the aerobic operation is started to start aeration, and the opening / closing device of the slit 32 is activated to open the slit.
The sludge mixed liquid C inside the water flow adjusting wall 3 rises together with the membrane cleaning air, a part is discharged from the slit 32 to the external water channel, and the rest is a part free of bubbles inside the water flow adjusting wall 3. It descends to form an upper and lower circulating water stream. The dissolved oxygen contained in the sludge mixed liquid C discharged from the slit 32 to the circulation channel is mixed with the dissolved oxygen supplied by the aeration stirrer 4 and effectively used for respiration of microorganisms and oxidative decomposition of organic matter.
[0023]
As described above, even in the oxidation ditch water tank 10 having a short water channel, which is difficult to form two aerobic and anaerobic zones, the aerobic time zone and anaerobic are not adversely affected by the aeration for cleaning. By repeating the time zone alternately, nitrification and denitrification can be advanced, and nitrogen in the sewage can be gasified and removed.
In addition, by adjusting the oxygen dissolved by the membrane cleaning air to flow into the water channel of the oxidation ditch, the aerobic / anaerobic conditions are divided into zones or changed over time, so that Nitrification and denitrification, which was difficult with the single tank membrane separation activated sludge method as in the method, can be carried out efficiently.
In addition, even in an oxidation ditch water tank with a short channel length, membrane filtration can be continued without stopping the membrane cleaning during anaerobic times, so there is no need to increase the required number of separation membranes and the equipment cost can be reduced. can do.
Furthermore, since oxygen dissolved by the membrane cleaning air can also be used for respiration of microorganisms and oxidative decomposition of organic substances, an increase in running cost can be suppressed without wasting dissolved oxygen.
[0024]
【The invention's effect】
According to the nitrogen removing device in the membrane separation type oxidation ditch of the present invention, the membrane is immersed in the central part of the tank, and the membrane is washed by the air diffused from the air diffuser provided at the bottom of the membrane separating device. The sludge mixed liquid is taken in from the intake port provided at a part of the bottom of the water flow adjustment wall, the discharge port with a switch for discharge is provided at a part of the upper part, and the aeration stirrer provided outside the water flow adjustment wall is operated anaerobically. Since the aerobic operation is repeated alternately, by closing the discharge port during anaerobic operation and performing only agitation using an aeration stirrer, even if the inside of the water flow adjustment wall is in an aerobic state, The entire channel of the oxidation ditch can be anaerobic, and during aerobic operation, by opening the outlet, it is diffused for membrane cleaning and mixed with sludge while rising in the membrane separator. Oxygen dissolved in liquid , It flows out from the discharge outlet provided on the upper part of the water flow control wall to the water channel part of the oxidation ditch together with the sludge mixture, and the aeration stirrer performs aeration operation to make up for the shortage of oxygen, so cleaning Since the water for aeration and aeration are combined and the water channel is short, the entire water channel is in an aerobic state, and the oxygen dissolved by the membrane cleaning air is adjusted to flow into the water channel of the oxidation ditch. Therefore, nitrification / denitrification can be promoted and nitrogen in wastewater can be removed by changing the aerobic / anaerobic conditions over time.
[Brief description of the drawings]
FIG. 1 is a schematic plan view of an oxidation ditch water tank having a long channel length, showing a reference example of a nitrogen removal method in a membrane separation type oxidation ditch.
FIG. 2 is a schematic plan view of an oxidation ditch water tank having a short channel length, showing an embodiment of a nitrogen removal method in the membrane separation type oxidation ditch of the present invention.
3 is an elevational sectional view of FIG. 2. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Oxidation ditch water tank 10 Oxidation ditch water tank 11 Water channel 12 Water channel 2 Membrane separation device 3 Water flow control wall 4 Aeration machine 5 Aeration pipe 21 Suction pump 30 Sludge mixed liquid inlet 31 Sludge mixed liquid outlet (slit)
32 Sludge mixture discharge port that can be opened and closed (Slit with switchgear)
A Wastewater B Treated water C Sludge mixture

Claims (1)

In the oxidation ditch having a short circulation channel that switches the circulation channel between an aerobic state and an anaerobic state in time, a water flow adjusting wall disposed in the center of the tank, and installed in the water flow adjusting wall The membrane separation device and the membrane cleaning air diffuser pipe and the aeration stirrer arranged to generate the water flow while agitating and agitating the sewage in the circulating water channel, the water flow adjusting wall is part of the bottom In the upper part, an inlet for the sludge mixed liquid is provided, and an upper part is provided with an outlet for the sludge mixed liquid that is opened and closed in synchronization with anaerobic operation and aerobic operation by an aeration stirrer . The apparatus for removing nitrogen in a membrane separation type oxidation ditch, wherein the exhaust port is opened during aerobic operation .

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