JP2020138185A - Biological treatment apparatus - Google Patents

Abstract

To provide a biological treatment apparatus which is highly effective in cleaning a screen by gas.SOLUTION: A biological treatment apparatus 1 includes a biological treatment tank 10 which houses a carrier 12 holding microorganisms and performs anaerobic biological treatment of treated water, an agitator 20 which agitates the carrier 12, a flat screen 22 which is obliquely provided in the biological treatment tank 10 and separates the treated water having undergone the biological treatment and the carrier 12, and a first diffuser pipe 24 and a second diffuser pipe 26 for jetting gas from a lower part of the screen 22 to the screen 22. The first diffuser pipe 24 and the second diffuser pipe 26 are arranged, displaced vertically and horizontally from one another.SELECTED DRAWING: Figure 1

Description

The present invention relates to a technique for a biological treatment apparatus that anaerobically treats water to be treated.

For the treatment of wastewater containing organic matter and nitrogen (organic nitrogen, ammonia nitrogen, nitrate nitrogen and / or nitrite nitrogen), aerobic microorganisms and facultative anaerobes that perform denitrification reaction are used. Biological treatment using sex microorganisms is applied. In addition to the standard activated sludge method, there is a carrier method (fixed bed or fluidized bed) in which organisms are retained at a high concentration using a microbial retention carrier. The carrier method enables higher-load operation than the activated sludge method, and does not require the return of solid-liquid separated sludge in the sedimentation basin, so maintenance is easy. In particular, the method using a fluid carrier does not require backwashing, so that stable operation is possible, but a screen for separating the carrier and treated water is required.

Examples of the screen include a cylindrical screen as in Patent Document 1, a flat screen as in Patent Document 2, and the like.

Japanese Unexamined Patent Publication No. 2010-75837 Japanese Unexamined Patent Publication No. 7-47390

By the way, if SS or the like contained in the water to be treated adheres to the screen, the screen may become dirty and clogged. Therefore, it is necessary to clean the screen by blowing a gas such as air onto the screen from below the screen. However, in a biological treatment tank that anaerobically treats water to be treated, it is necessary to keep the inside of the tank in an anaerobic atmosphere, so the amount of gas (air amount) used for cleaning the screen installed in the tank is limited. , It was difficult to clean the screen thoroughly.

Therefore, an object of the present invention is to provide a biological treatment apparatus having a high effect of cleaning a screen with a gas.

The biological treatment apparatus according to the embodiment of the present invention includes a biological treatment tank that accommodates a carrier holding microorganisms and anaerobically performs biological treatment of water to be treated, a stirring means for stirring the carrier, and the biological treatment tank. A flat screen that is provided so as to be inclined inside and separates the treated water subjected to the biological treatment and the carrier, and an air diffuser means for ejecting gas from below the screen onto the screen are provided. The air diffuser means includes a first air diffuser and a second air diffuser, and the first air diffuser and the second air diffuser are arranged so as to be displaced from each other in the horizontal direction. To do.

In the biological treatment apparatus, the second air-dissipating means is farther in horizontal distance from the lower end of the screen than the first air-dissipating means, and is displaced in the direction perpendicular to the first air-dissipating means. It is preferably arranged.

According to the present invention, it is possible to provide a biological treatment apparatus having a high effect of cleaning a screen with a gas.

It is a schematic diagram which shows an example of the structure of the biological processing apparatus of this embodiment. It is a schematic diagram for demonstrating the cleaning effect of the screen by the air diffuser in this embodiment. It is a schematic diagram for demonstrating the cleaning effect of the screen by the air diffuser when the baffle is installed in this embodiment. It is a schematic diagram for demonstrating the installation state of a screen, a 1st air diffuser and a 2nd air diffuser.

Hereinafter, embodiments of the present invention will be described. It should be noted that the present embodiment is an example of carrying out the present invention, and the present invention is not limited to the present embodiment.

FIG. 1 is a schematic view showing an example of the configuration of the biological treatment apparatus of the present embodiment. The biological treatment apparatus 1 shown in FIG. 1 includes a biological treatment tank 10. A wastewater inflow line 14 is installed at the inlet 10a of the biological treatment tank 10, and a treated water discharge line 16 is installed at the outlet 10b of the biological treatment tank 10.

The carrier 12 holding the microorganism is housed in the biological treatment tank 10 shown in FIG. 1, and the biological treatment of the water to be treated is anaerobically performed while flowing the carrier 12 in the tank. The carrier 12 is a carrier or the like to which microorganisms such as anaerobic microorganisms are attached, for example, as a biological membrane. The biofilm is, for example, a membrane-like structure in which microorganisms and products such as exopolysaccharides produced by the microorganisms are aggregated.

The biological treatment device 1 shown in FIG. 1 includes a stirring device 20 that stirs the carrier 12 in the biological treatment tank 10. The stirring device 20 shown in FIG. 1 includes a stirring blade connected to a motor, and the stirring blade is rotated by driving the motor to stir the carrier 12. The stirring device 20 used in the present embodiment is not limited to the above configuration as long as it has a device configuration capable of stirring the carrier 12 in the biological treatment tank 10.

The biological treatment apparatus 1 shown in FIG. 1 includes a screen 22 for separating the treated water subjected to the biological treatment and the carrier 12. The screen 22 is flat and is provided so as to be inclined in the biological treatment tank 10. The screen 22 is preferably provided near the outlet 10b of the biological treatment tank 10 to which the treated water discharge line 16 is connected, for example.

The biological treatment apparatus 1 shown in FIG. 1 includes a first air diffuser 24 and a second air diffuser 26 provided below the screen 22. The first air diffuser 24 and the second air diffuser 26 may be arranged so as to be displaced from each other in the horizontal direction, but are preferably arranged so as to be displaced from each other in the vertical direction. The top and bottom of FIG. 1 are in the vertical direction, and the left and right are in the horizontal direction. The same applies to other drawings.

Further, the first air diffuser 24 and the second air diffuser 26 extend, for example, along the width direction (depth direction in FIG. 1) of the screen 22, and each of them is provided with a plurality of spouts. A gas supply device (for example, a blower or the like) (not shown) is connected to the first air diffuser 24 and the second air diffuser 26, and gas is supplied from the gas supply device to each air diffuser.

The biological treatment apparatus 1 shown in FIG. 1 preferably includes a hydrogen donor supply pipe 28.

An example of the operation of the biological processing apparatus 1 shown in FIG. 1 will be described.

The water to be treated according to the present embodiment is, for example, wastewater discharged from a food manufacturing factory, an electronic industry factory, a pulp manufacturing factory, a chemical factory, or the like.

The water to be treated is introduced into the biological treatment tank 10 from the wastewater inflow line 14. In the biological treatment tank 10, the carrier 12 and the water to be treated are agitated by the stirring device 20, and the microorganisms retained in the carrier 12 anaerobically perform the biological treatment of the water to be treated. In the biological treatment tank 10, for example, when denitrification treatment for reducing nitrate nitrogen or nitrite nitrogen contained in the water to be treated to nitrogen gas is performed, the hydrogen donor supply pipe 28 is required. A hydrogen donor such as alcohol is supplied to the biological treatment tank 10. The treated water biologically treated in the biological treatment tank 10 is separated from the carrier 12 by the screen 22, and is discharged from the treated water discharge line 16 to the outside of the system.

If such a process is continued, SS or the like adheres to the surface of the screen 22 and clogging occurs. Therefore, gas is discharged from the ejection ports of the first air diffuser pipe 24 and the second air diffuser pipe 26 to the screen 22. The screen 22 is cleaned by ejecting. Gas ejection by the first air diffuser 24 and the second air diffuser 26 may be performed continuously or intermittently.

FIG. 2 is a schematic diagram for explaining the cleaning effect of the screen by the air diffuser in the present embodiment. The dashed arrow shown in FIG. 2 represents the flow of gas ejected from the first air diffuser 24 and the second air diffuser 26. As shown in FIG. 2, the gas ejected from the spout of the first air diffuser 24 installed below the screen 22 comes into contact with the inclined screen 22 and rises along the surface of the screen 22, but the gas accompanies it. A part of the screen 22 passes through the screen 22. Therefore, it is difficult to bring a sufficient amount of gas into contact with the entire surface of the screen 22 using only the first air diffuser 24, so that the entire surface of the screen 22 cannot be effectively cleaned. However, in the present embodiment, as shown in FIG. 2, the screen 22 is difficult to clean with the first air diffuser 24 due to the second air diffuser 26 provided so as to be laterally displaced from the first air diffuser 24. Since the gas can be ejected toward the region of No. 1, it is possible to clean the region that is difficult to clean with the first air diffuser 24. Therefore, the cleaning effect of the screen 22 by the first air diffuser 24 and the second air diffuser 26 displaced from each other in the horizontal direction is higher than the cleaning effect of the screen 22 by the first air diffuser 24 alone.

The screen 22 may be a flat screen, and examples thereof include a flat wedge wire screen, a flat wire mesh, and punching metal on a normal surface. In particular, a flat wedge wire screen is preferable because it has strength and is less likely to be clogged.

The slit width and aperture ratio of the screen 22 are not particularly limited, and may be appropriately set according to the size of the carrier 12 used, the water flow rate, the strength of the material constituting the screen 22, and the like.

FIG. 4 is a schematic view for explaining the installation state of the screen, the first air diffuser, and the second air diffuser. The tilt angle of the screen 22 (θ1 shown in FIG. 4) may be more than 0 ° to less than 90 ° with respect to the vertical direction, but is preferably 5 ° to 15 ° with respect to the vertical direction. .. As shown in FIG. 4, the inclination angle of the screen 22 is an angle θ1 formed by the primary side surface 22a of the screen 22 and the vertical direction H1. The larger the tilt angle of the screen 22, the larger the amount of gas passing through the screen 22, and a higher cleaning effect can be obtained, but there is a trade-off relationship that the amount of gas for cleaning the entire surface of the screen 22 increases. Become. Therefore, in consideration of the balance between the cleaning effect and the amount of gas for cleaning, the inclination angle of the screen 22 is more preferably in the range of 5 to 7 ° with respect to the vertical direction.

In the present embodiment, the first air diffuser 24 and the second air diffuser 26 are separate pipes, but the first air diffuser 24 and the second air diffuser 26 may be connected to form one pipe. The spouts provided in the first air diffuser 24 and the second air diffuser 26 may be installed at any position in each air diffuser, but in terms of suppressing blockage of the spout due to the accumulation of SS in the water to be treated. , It is preferable to arrange it in the lower part of the air diffuser, and it is preferable to arrange it in the upper part of the air diffuser from the viewpoint of increasing the contact efficiency between the gas and the screen 22.

FIG. 3 is a schematic view for explaining the cleaning effect of the screen by the air diffuser when the baffle is installed in the present embodiment. As shown in FIG. 3, the biological treatment apparatus 1 of the present embodiment includes a baffle 30 arranged at a predetermined distance from the screen 22, and a first air diffuser 24 and a first air diffuser 24 and the baffle 30 are provided between the screen 22 and the baffle 30. It is preferable that a flow path 30a through which the gas ejected from the second air diffuser 26, which is arranged so as to be displaced from each other in the vertical and horizontal directions with respect to the first air diffuser 24, is formed. As a result, the gas ejected from the first air diffuser 24 and the second air diffuser 26 is likely to rise along the surface of the screen 22, and the cleaning effect of the screen 22 is further enhanced.

The first air diffuser 24 and the second air diffuser 26 may be arranged below the lower end of the screen 22, as shown in FIGS. 1 and 2, and further, a horizontal distance from the lower end of the screen 22 (FIG. 4). The second air diffuser 26 whose horizontal direction L (distance shown in the horizontal direction L) is located farther than the first air diffuser 24 may be arranged above and below the first air diffuser 24, or as shown in FIG. , The first air diffuser 24 is arranged at a position lower than the lower end of the screen 22 and at a position where gas can be ejected to the lower end of the screen 22, and the horizontal distance from the lower end of the screen 22 is from the first air diffuser 24. The second air diffuser 26 at a distant position may be arranged at a position higher than the lower end of the screen 22 and below a position where the gas ejected from the first air diffuser 24 does not come into contact with the screen 22. In addition to the first air diffuser 24 and the second air diffuser 26, a third air diffuser that is vertically and horizontally displaced from at least one of these air diffusers may be provided. Further, it may be provided with a larger air diffuser.

In the present embodiment, as an air diffuser means for ejecting gas to the screen 22, an air diffuser tube (first air diffuser tube 24 and second air diffuser tube 26) has been described as an example, but the present invention is not limited to this, and for example, It may be a diffuser or the like. However, as the air diffuser, an air diffuser having a low oxygen dissolution efficiency in the water to be treated is preferable because it is easy to maintain an anaerobic atmosphere in the biological treatment tank 10.

Although the description in the figure is omitted, the biological treatment apparatus 1 of the present embodiment is installed vertically (or substantially vertically) in the biological treatment tank 10, includes a draft tube having an open top and bottom, and agitates in the draft tube. It is preferable to install a stirring blade of the device. The rotation of the stirring blade in the draft tube, for example, forms a downward flow inside the draft tube and an upward flow outside the draft tube, increasing the fluidity of the carrier 12.

The carrier 12 is not particularly limited, and examples thereof include a plastic carrier, a sponge-like carrier, and a gel-like carrier. The gel-like carrier is preferable in that it can be subjected to a high load treatment as compared with a plastic carrier and a sponge-like carrier because the floating by nitrogen gas in the denitrification treatment is suppressed and the fluidity by stirring is high. .. The gel-like carrier is not particularly limited, and examples thereof include a water-absorbent polymer gel-like carrier containing polyvinyl alcohol, polyethylene glycol, polyurethane and the like.

The shape of the carrier 12 is not particularly limited, but a spherical or cubic shape (cube shape), a rectangular parallelepiped shape, a cylindrical shape, or the like having a diameter of about 1 mm to 10 mm is preferable. In particular, a spherical or cylindrical gel-like carrier having a diameter of about 3 to 8 mm is preferable.

The specific gravity of the carrier 12 is preferably greater than 1.0 in that it is easy to form a flowing state in the biological treatment tank, and the true specific density is 1.1 or more, or the apparent specific gravity is 1.01 or more. Is preferable.

The amount of the carrier 12 charged into the biological treatment tank 10 is preferably in the range of 10 to 70% with respect to the volume of the biological treatment tank 10. If the input amount of the carrier 12 is less than 10% with respect to the volume of the biological treatment tank 10, the reaction rate of the biological treatment may decrease, and if it exceeds 70%, the carrier 12 becomes difficult to flow, and in long-term operation. Raw water may short-pass and the quality of treated water may deteriorate due to clogging due to sludge.

The stirring of the carrier 12 in the biological treatment tank 10 is not limited to that by the stirring device 20, and for example, the water to be treated in the biological treatment tank 10 is taken out of the tank and returned from the bottom of the tank by an upward flow. It may be a circulation device or the like. The carrier 12 in the biological treatment tank 10 is agitated by the water to be treated returned in the upward flow by the circulation device. In general, a method of stirring the carrier with a stirrer is called a complete mixing method, and a method of returning water to be treated by an upward flow by a circulation device is called an upward flow method.

In the present embodiment, the pH of the water to be treated is preferably in the range of 6.0 to 8.0, more preferably in the range of 7.0 to 8.0, in terms of the reaction rate of the biological treatment. The pH of the water to be treated is adjusted, for example, by supplying the pH adjuster from the pH adjuster supply line (not shown) to the raw water tank (not shown) storing the water to be treated.

The pH adjusting agent is not particularly limited, such as an acid agent such as hydrochloric acid and an alkaline agent such as sodium hydroxide. Further, the pH adjusting agent may be, for example, sodium bicarbonate having a buffering action, a phosphate buffer solution or the like.

In the present embodiment, when the water to be treated is biologically treated, it is preferable to add a nutrient to, for example, untreated water from the viewpoint of maintaining good decomposition activity of anaerobic microorganisms. The nutritional supplement is not particularly limited, and examples thereof include a carbon source, a nitrogen source, and other inorganic salts (Ni, Co, Fe, etc.).

In the present embodiment, it is preferable to adjust the temperature of the water in the biological treatment tank 10 so as to be 20 ° C. or higher. Generally, below 20 ° C., the reaction rate of biological treatment tends to decrease. The method for adjusting the temperature of the water temperature in the biological treatment tank 10 is not particularly limited. For example, a heating device such as a heater is installed in the biological treatment tank 10 and the heat of the heater or the like causes the inside of the biological treatment tank 10 to be heated. Examples include a method of adjusting the water temperature.

1 Biological treatment equipment, 10 Biological treatment tanks, 10a inlet, 10b outlet, 12 carriers, 14 drainage inflow line, 16 treated water discharge line, 20 stirrer, 22 screen, 22a primary side surface, 24 first air diffuser, 26th 2 air diffuser pipe, 28 hydrogen donor supply pipe, 30 baffle, 30a flow path.

Claims (2)

A biological treatment tank that houses a carrier that retains microorganisms and anaerobically treats the water to be treated.
A stirring means for stirring the carrier and
A flat screen that is inclinedly provided in the biological treatment tank and separates the treated water subjected to the biological treatment and the carrier.
An air diffuser for ejecting gas from below the screen onto the screen is provided.
The air diffuser means includes a first air diffuser and a second air diffuser, and the first air diffuser and the second air diffuser are arranged so as to be displaced from each other in the horizontal direction. Biological processing equipment. The second air-dissipating means is arranged so that the horizontal distance from the lower end of the screen is farther than that of the first air-dissipating means and the positions of the second air-dissipating means are displaced from each other in the direction perpendicular to the first air-dissipating means. The biological treatment apparatus according to claim 1.