JPH09117647A - Operation of air diffusion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an air diffusion hole from being clogged when operating an air diffusion device arranged below a submerged membrane cartridge. SOLUTION: This air diffusion device supplies the required quantity of an air for the aeration treatment of a liquid to be treated and also the quantity of an air for generating the adequate speed of the ascending current of a mixture of air and liquid for cleaning the membrane surface of a membrane cartridge 2 and an adequate air ejection speed for preventing the clogging of an air diffusion hole 5a from occurring at the time of an operation to filter the membrane cartridge. When stopping the operation to filter the membrane cartridge 2, at least, the adequate quantity of an aeration air for preventing the clogging of the air diffusion hole 5a from occurring is supplied. Even when stopping the operation to filter the membrane cartridge 2, the aeration process is not discontinued, so that the clogging of the air diffusion hole 5a is prevented from occurring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating an air diffuser, and more particularly to an immersion type for filtering a liquid to be treated in a domestic wastewater treatment facility such as a small combined treatment septic tank or an industrial wastewater treatment facility utilizing an activated sludge method. The present invention relates to a method of operating an air diffuser arranged below a membrane cartridge.

[0002]

2. Description of the Related Art Conventionally, in a domestic wastewater treatment facility such as a small combined treatment septic tank or an industrial wastewater treatment facility utilizing an activated sludge method, for example, a membrane separation device as shown in FIGS. It is dipped in and installed.

In the membrane separation device, flat plate-shaped membrane cartridges 2 are arranged in parallel inside a box-shaped membrane case 1 having an opening at the top and bottom, and a box-like air diffusion case 3 having an opening at the top and bottom is also provided. Is provided with an air diffuser pipe 5 as an air diffuser communicating with an air supply means such as a blower 4 outside the tank, and the membrane case 1 and the air diffuser case 3 are vertically separable from each other. There is.

In the membrane cartridge 2, as shown in FIG. 2, the organic filter membranes 7, 7 are arranged on the surface of the filter plate 6, and the filter plate 6 is provided.
A permeated water channel 8 is provided between the filter membrane 7 and the filtration membrane 7, and a suction tube 9 and a water collection pipe 10 that communicate with the permeated water channel 8 are provided. A suction means (not shown) such as a water collecting header pipe or a suction pump is provided so as to communicate with the water collecting pipe 10.

When performing filtration operation of such a membrane separation device, suction pressure is applied to the permeate flow passage 8 through the water collection pipe 10 and the suction tube 9 by the suction means, or the treated material above the membrane cartridge 2 is treated. By setting the head of the liquid as the filtration driving pressure, the suspended matter 11 such as activated sludge and fine particles is captured by the filtration membrane 7, and the permeated water 12 that permeates the filtration membrane 7 and flows into the permeated water channel 8 is sucked. It is taken out of the treatment tank through the tube 9 and the water collection pipe 10.

At this time, aeration air is supplied from the blower 4 to the liquid to be treated through the air diffusion holes 5a of the air diffusion pipe 5, and
The entire membrane surface of the membrane cartridge 2 is uniformly rubbed by the gas-liquid mixed upflow 14 generated by the bubbles 13 of the aerated air, thereby preventing the cake layer from being deposited on the surface of the filtration membrane 7.

[0007]

As described above, the air diffuser arranged in the membrane separator supplies aeration air to the liquid to be treated, and particularly in the case of activated sludge treatment, the aeration air is used. Its main purpose is to supply oxygen to microorganisms. For this reason, aeration is reduced or stopped when the amount of the liquid to be treated flowing into the treatment tank is small, and in other cases, aeration may be stopped in order to save aeration power.

However, in such an air diffuser,
When air is continuously ejected, the diffusion holes are prevented from being blocked, but when the aeration is reduced or stopped, activated sludge and fine particles in the liquid to be treated flow back into the pipe and the diffusion holes are easily blocked. When a part of the diffuser holes is closed, the air supplied from the air supply means into the diffuser pipe is ejected from the open diffuser holes, and the bubbles of the aerated air and the upflow of gas-liquid mixture caused by the bubbles are generated. The flow is biased, resulting in
Activated sludge or the like accumulates on the membrane surface of the membrane cartridge at a position where the flow is not supplied, resulting in clogging between membranes.

For this reason, various measures have been taken to prevent the clogging of the air diffuser, but there is still no satisfactory means, and in order to recover the blocked air diffuser, a membrane with an air diffusing tube disposed at the bottom is used. At present, it takes a lot of time and effort to take out the entire separation device from the processing tank.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an operating method of an air diffusing device in which clogging of air diffusing holes is less likely to occur.

[0011]

In order to solve the above-mentioned problems, an operating method of an air diffuser of the present invention is arranged below a submerged membrane cartridge for filtering a liquid to be treated and aerated to the liquid to be treated. A method of operating an air diffuser for supplying air, wherein during a filtration operation of a membrane cartridge, an amount of air required for treating a liquid to be treated, a gas-liquid mixing upflow velocity required for cleaning a membrane surface of the membrane cartridge, Aeration air is supplied in an amount that gives an air ejection speed that does not cause clogging of the air diffusion holes, and at least when supplying filtration air to the membrane cartridge, an amount of aeration air that gives an air ejection speed that does not cause clogging of the air diffusion holes is supplied. It is the one.

Here, in the case of activated sludge treatment, the amount of air required for treating the liquid to be treated means the amount of air that can supply at least oxygen required for the activated sludge by stirring and mixing the activated sludge mixed liquid. In other cases, it means the amount of air required for well-known processing such as stirring and mixing at least the liquid to be treated to release the gas in the liquid to be released into the atmosphere.

According to the above operating method, the aeration air amount is changed without stopping the air diffuser during the filtration operation of the membrane cartridge and during the filtration operation stop,
It is possible to prevent the diffusion holes from being blocked when the filtration operation is stopped.

[0014]

Embodiments of the present invention will be described below. Since the method for operating the air diffuser of the present invention is carried out in the membrane separation device described with reference to FIGS. 1 and 2, illustration and detailed description thereof will be omitted, and the reference numerals shown in FIGS. Explain by quoting.

The membrane separation device is installed inside the activated sludge treatment tank to separate fine particles such as activated sludge. The membrane cartridge 2 is arranged inside the membrane case 1 and arranged below the membrane case 1. Inside the air diffuser case 3, an air diffuser 5 as an air diffuser communicating with an air supply means such as a blower 4 is provided. The membrane cartridge 2 is equipped with a microfiltration membrane 7 having a pore diameter of 1 μm or less suitable for separating fine particles such as activated sludge, and 50 to 150 pieces are arranged inside the membrane case 1 as one set. The air diffuser 5 corresponds to one set of the membrane cartridges 3 and has ten to several tens of air diffuser holes 5a.

The operation method of the air diffuser will be described below. Inside the activated sludge treatment tank, while subjecting the liquid to be treated to activated sludge, the membrane cartridge 2 is filtered to separate fine particles such as activated sludge.

At that time, the blower 4 is operated to operate the air diffuser 5
Thereby, the activated sludge mixed solution in the tank is agitated and mixed to give an amount of air capable of supplying oxygen required for the activated sludge, and an upflow velocity of gas-liquid mixture necessary for cleaning the membrane surface of the membrane cartridge 2 is given, and Aeration air is supplied in an amount that provides an air ejection speed that does not cause clogging of the diffuser holes 5a.

When the inflow of the liquid to be treated into the activated sludge treatment tank becomes small, the filtration operation of the membrane cartridge 2 is stopped. At that time, the operation of the blower 4 is adjusted to give an air jet speed from the air diffusing pipe 5 so that at least the air diffusing holes 5a are not clogged, and if necessary, the activated sludge mixed liquid in the tank is further stirred and mixed. Aerated air is supplied in an amount sufficient to supply the oxygen required for activated sludge.

According to the above-described operating method, even when the filtration operation of the membrane cartridge 2 is stopped, the required amount of aeration air is supplied without stopping the air diffuser, and the clogging of the air diffuser hole 5a is prevented. It

The amount of aeration air may be changed by changing the operating number of air supply means such as the blower 4, or by changing the flow rate by an inverter or the like using one air supply means. The ratio of the amount of aerated air at the time of filtration operation and at the time of filtration operation stop is
Although it cannot be uniquely determined because it is related to the amount of oxygen necessary for the microorganisms constituting the activated sludge, it is usually 1 or less when the filtration operation is stopped and 2 when the filtration operation is stopped. The minimum aeration amount of air is 3 in order to prevent clogging of diffuser holes.
It is determined from the viewpoint that it cannot be less than m / sec. The amount of aerated air at the time of filtration operation is determined by one factor being the amount of aerated air that makes the gas-liquid mixing upward flow velocity for cleaning the membrane surface 0.5 m / sec or more.

For example, in a domestic wastewater treatment facility equipped with a treatment tank for treating domestic wastewater of 200 people, 150 membrane cartridges are installed inside the treatment tank, and an air diffuser is used to aerate the amount of aerated air during filtration operation. Is 2.0 m ³ / min, and the amount of aerated air when the filtration operation is stopped is 0.75 m ³ / min.

In the above description, the activated sludge treatment has been described, but in other cases, the liquid to be treated is agitated and mixed with aerated air so that the gas in the liquid to be treated is released into the atmosphere. If so, the amount of air required for such treatment may be supplied.

[0023]

As described above, according to the present invention, when the air diffuser disposed below the submerged membrane cartridge is operated, the air diffuser is used during the filtration operation of the membrane cartridge and when the filtration operation is stopped. Since the amount of aeration air is changed without stopping, the clogging of the air diffuser can be prevented even when the filtration operation is stopped.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an overall configuration of a conventional membrane separation device in which a method for operating an air diffuser of the present invention is implemented.

FIG. 2 is an explanatory view showing a membrane cartridge that constitutes a part of the membrane separation device shown in FIG.

[Explanation of symbols]

 2 Immersion type membrane cartridge 4 Blower 5 Air diffuser 5a Air diffuser

Claims (1)

[Claims] 1. A method of operating an air diffuser which is disposed below an immersion type membrane cartridge for filtering a liquid to be treated and which supplies aeration air to the liquid to be treated, wherein during the filtration operation of the membrane cartridge, the liquid to be treated is treated. Aeration air is supplied in an amount that provides an amount of air necessary for treating the liquid, an ascending flow rate of gas-liquid mixture necessary for cleaning the membrane surface of the membrane cartridge, and an air ejection rate that does not cause clogging of diffuser holes. The method for operating an air diffusing apparatus, characterized in that at the time of stopping the filtering operation, the aeration air is supplied in an amount that provides an air ejection speed that does not cause clogging of air diffuser holes.