JP2003117581A - Waste water treating method and waste water treating equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste water treating method and waste water treating equipment which permit agitation with saved energy in an OD process, facilitate DO control by separately installing a diffuser and permit the removal of nitrogen and phosphorus as well. SOLUTION: The waste water treating method is a method of biologically subjecting waste water to a cleaning treatment by passing the waste water to a going around flow passage, in which an agitator having a body to make oscillating and rotating motion is disposed midway in the flow passage, by which air is fed and the waste water is rounded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called oxidation-ditch method (hereinafter referred to as OD method) for purifying wastewater such as sewer and industrial wastewater, and an apparatus therefor.

[0002]

2. Description of the Related Art As a sewage treatment facility, a lagoon type called OD method is known. It is equipped with a stirrer and an air diffuser that cause a flow in a water tank like a looped water channel.The stirrer and the air diffuser may be separate, and the oxygen in the air is dissolved by the inclusion of the stirrer. There is also a surface aeration type.

As the agitator used here, surface aeration type ones include a vertical axis type aerator and a horizontal axis drum type surface aeration device. The vertical axis type aerator performs surface aeration by bringing out a piece of stirrer from half the water and splashing water when it is rotated and air contact by turbulent stirring at the center of the shaft. The horizontal drum type is a drum-shaped one that has a ring with protrusions that rotate to rotate it up, scratching the water in front and splashing it up, and hitting the water surface in the rear to dissolve air by raising splashes. It is a thing. As the submerged stirrer, there are a horizontal axis type large propeller stirrer and a vertical axis type paddle stirrer. In the case of the submerged stirrer, a stirring operation and an air diffuser for supplying air are distinguished.

[0004]

However, in the case of the surface aeration type, in order to control the amount of oxygen to be dissolved in order to deal with the cases such as nitrogen removal and phosphorus removal, there is no choice but to control the rotation speed. In such cases, the number of rotations often has to be reduced, which weakens the water flow at the same time as the amount of oxygen, and a stirrer that generates water flow and supplies oxygen at the same time removes nitrogen. It is difficult to deal with removing phosphorus. Furthermore, there is a problem in that the power required to engulf the oxygen in the air is required, and the power consumption is large.

On the other hand, the equipment that divides air diffusion and water flow generation in the OD method can easily deal with nitrogen removal and phosphorus removal. Since the amount of air diffused can be adjusted independently, there is no adverse effect such as a decrease in the stirring ability of the water tank. The agitator that can be used in such a situation is either a horizontal axis type large propeller or a vertical axis type paddle agitator. They are,
Although it operates with relatively low power, it has a short water flow distance, lacks the ability to crush the bubbles supplied from the air diffuser, and lacks the ability to carry it, and does not help reduce aeration power. There wasn't.

According to the present invention, in the OD method capable of removing nitrogen and phosphorus, a system for easily controlling the DO in the tank is constructed by separating the air diffuser and the agitator, and running with an energy-saving agitator. OD that can reduce costs
The purpose is to provide the law.

[0007]

Means for Solving the Problems The inventors of the present invention have made earnest studies to solve the above problems, and as a result, by using a stirring device having a body that performs a swinging rotary motion that repeats an inversion motion, The present invention has been achieved by finding that both generation of air and aeration can be achieved at the same time.

That is, the first aspect of the present invention is a method of biologically purifying waste water through a circulating flow path,
A gist of a wastewater treatment method is characterized in that an agitation device having a body that performs an oscillating rotary motion is provided in the middle of a flow path, and thereby air is supplied and wastewater is circulated. Further, a second aspect of the present invention is a wastewater treatment device comprising a circulating flow path for biologically purifying wastewater, which is provided with a stirring device having a body for swinging and rotating motion in the middle of the flow path. The gist is a wastewater treatment device characterized by the above.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The size and shape of the processing apparatus in the present invention are not particularly limited as long as the waste water can circulate in the circulating flow path. The depth is also not particularly limited. OD
The method is a water treatment method in which the flow path has a track-like shape as shown in FIG. 4, and the raw water goes through the aerobic zone and anoxic zone while the raw water circulates through the flow path to nitrify and denitrify. First, step by step, the raw water and the returned sludge 9 flow into the anoxic zone 15 and are sent from the agitator 12 to the agitator 11.
The water flow scraped out by the water flows toward the aerobic zone 16 side. In the aerobic zone 16, the bubbles supplied by the air diffuser 13 are broken by the stirring vortex of the stirrer 11 to become finer and dissolve in water. The dissolved oxygen oxidizes organic matter and ammoniacal nitrogen to become carbon dioxide and nitrate nitrogen. In the anoxic zone 17, the remaining organic components reduce the generated nitrate nitrogen to nitrogen gas, and at the same time, the organic components are oxidized to carbon dioxide gas. At this stage, it is considered that the organic content is almost gone. If there is no organic content, it is possible that internal respiration causes autolysis to reduce nitrate nitrogen to nitrogen gas. Further, the remaining ammoniacal nitrogen is oxidized to nitrate nitrogen in the aerobic zone 18, and a part thereof is sent to the settling tank as the treated mixed water 10 containing activated sludge. The remaining residue is mixed with the raw water and the returned sludge in the anoxic zone 15, and the nitrate nitrogen generated in the aerobic zone 18 is denitrified with the organic content of the raw water.

The ratio of the aerobic zone to the anaerobic zone is related to the amount of air in the diffusers 13 and 14. If the amount of air becomes too large and the DO becomes high, it will take time until the dissolved oxygen is used up, and most of the organic matter will be decomposed and the anoxic zone will become smaller, as well as the organic matter used for denitrification will also disappear. It is possible that it will end up. Therefore, controlling DO is very important.
For that reason, it is easier to control the stirring and the supply of air separately.

The present invention is characterized in that it is provided with an agitating device having a body that performs an oscillating rotary motion in the flow path. Examples of the stirring device used in the present invention for generating a water flow by oscillating rotary motion of the body include a stirring device having a rotationally symmetrical body, for example, a cylindrical body or a shape called an Oroid. In particular, an oroid shaped body is preferably used. Inverting rocking motion is similar to the movement of a boat's turret or fish's tail fin. By inverting it, energy consumption is kept to a minimum. The body of the stirrer also draws a figure of eight and moves in reverse, so less energy is required. When the body moves in the shape of a figure eight, the body, which is an oroid body, rolls and scrapes water forward.

FIG. 1 shows an example of a stirring device 6 having an oroidal body. In FIG. 1, 1 is an Oroidal body, 2 is a drive shaft, 3 is an arm, 4 is a drive device, and the body 1 is suspended from two arms 3. Reference numeral 5 denotes two dissimilar axis lines that rotate the body (hereinafter referred to as the cervical axis). Two arms 3 that are rotatable around the cervical axis 5 via a universal joint and whose rotational positions are offset by 90 degrees When the body 1 is agitated and the body 1 is agitated, the body 1 makes one revolution around one neck 5 when the drive shaft 2 makes one revolution. Next, when the drive shaft 2 makes one rotation, the body 1 makes one rotation around the opposite neck axis 5.

The arm 3 moves from the right side to the left side in accordance with the rotation of each drive shaft 2, but the energy required here is only a half rotation because the energy accompanying the movement of the center of gravity of the object is utilized. Good and very energy efficient agitation is possible.

As shown in FIGS. 2 and 3, the flow of water generated from the agitator having a body which performs a reverse swing motion has a direction as shown in FIG. 2, and the agitator is installed horizontally and the body is located under the body. In the standard installation shown, the direction changes depending on the number of revolutions, but the movement of water sucks up the water from the lower rear part of the stirrer, and flows upward from the horizontal by about 5 to 20 degrees (solid line 7). If you rotate it in the opposite direction, it goes to the opposite extension line,
Water is sucked in from the upper rear, causing a downward flow of 5 to 20 degrees from horizontal (broken line 8). If the stirrer is installed upside down, the water on the top of the stirrer can be made to flow downward (solid line 7), and in reverse, it can be made to flow upward (broken line 8).
If this feature is used well, it is possible to suck up and send out things that tend to sink, or to suck up floating things and run down.

In the present invention, the number of stirrers having a body that performs a reverse swing motion is not particularly limited and may be provided as needed. The installation location, especially the depth, is appropriately determined according to the purpose, and the orientation and angle of the stirrer are also appropriately determined.

The present invention describes a method and an apparatus for the OD method, which is preferably for removing nitrogen and phosphorus, but when these advanced treatments are not intended, it is possible to dissolve oxygen by the surface aeration method. It has the advantages that it can be stirred at the same time, both operations can be performed with very little energy, and that no blower is required. Surface aeration is possible by exposing the body to 1/3 or more of the water surface.

This stirrer adjusts the height, angle, etc. of the stirrer according to the size of the specific gravity, and by devising the installation method, one kind of energy-saving stirrer with an actual power of 0.5 kW to 1.0 kW is used for deposits and suspended matter It is possible to stir so as not to accumulate in the tank. Depending on the application, a stirrer of 0.5 kW to 1.0 kW can stir 250 to 1000 m ³ . This is a power input of 0.5 to 6 W / m ³ , and the existing 6 to
Greater energy savings than a 30 W / m ³ stirrer. In addition, a liquid having a high viscosity of 50 kPa · sec can be agitated in the same manner as in the case of fresh water due to the waves generated from the agitator.

Since the stirrer operates with energy saving of 0.5 to 6 W / m ³ , it is possible to stir by the power of a solar cell or a fuel cell using methane gas. When using a solar cell, inexpensive late-night power can be used at night, and it is possible to reduce the running costs of various processing facilities and production facilities.

[0019]

EXAMPLES Hereinafter, specific examples of the present invention will be shown by examples. Example 1 An example in which surface aeration was performed by a stirrer having a body for rocking motion when the water depth is shallow or when nitrogen treatment is not intended is shown. The mixed liquid 9 of the raw water and the returned sludge is rotated clockwise by the water flow sent forward by the stirrer 12 and the water flow sucked from the rear by the stirrer 11 by floating the bodies of the stirrers 11 and 12 shown in FIG. Flow to. In the raw water mixed sludge 9, organic substances are oxidized and decomposed into carbon dioxide gas and water in the aerobic zone 16 created by the agitator 11 and the aerobic zone 18 created by the agitator 12. As a result, the raw water of BOD 200 mg / L was treated to 10 mg / L or less. As a result of measuring the sludge concentration at points A to D, 34
It was between 0 and 3600 mg / L and was well stirred.

Example 2 For a nitrogen treatment or a deep water tank, an OD method as shown in FIG. 4 can be considered. FIG. 4 shows an OD method using an energy-saving stirrer and an air diffuser (when the water depth is deep or when appropriate nitrogen treatment is required). As a result, BOD 200mg
/ L is 10 mg / L or less, and nitrogen is 10 mg / L.
Below 3 mg / L, phosphorus was also processed up to 1.5 mg / L. For phosphorus, PA in the treated water sludge mixture
By injecting 30 ppm of C, it was processed to 1 mg / L or less. This is a method in which an air diffuser is installed in the lower part of the stirrer to divide the work of supplying air and stirring sludge. In the nitrification step in the nitrogen treatment, oxygen is newly required for nitrifying ammoniacal nitrogen into oxidized nitrogen in addition to the oxidation of only organic substances, and the required oxygen amount increases. In this method, the vortex generated from the stirrer and the entrained flow are used to increase the oxygen dissolution efficiency of the air supplied from the diffuser, and to reduce the amount of air from the blower. DO by reducing the amount of air
The anaerobic zone can be easily constructed because the stirring and air supply are divided. Further, since the stirrer is submerged in water, the effective water depth can be made large, and it can be applied to a deep water tank.

[0021]

According to the present invention, in the OD method capable of dealing with nitrogen removal and phosphorus removal, a system for easily controlling DO in the tank is constructed by separating the air diffuser and the agitator.
Since an energy-saving stirrer of 0.5 to 6 W / m ³ is used, it is possible to stir with the power of a solar cell or a fuel cell that uses methane gas, and since cheap nighttime electric power can be used at night, various processing facilities and production facilities are available. It is possible to reduce the running cost.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a stirrer having an oroidal body used in the present invention.

FIG. 2 is a diagram showing streamlines due to stirring.

FIG. 3 is a diagram showing streamlines due to stirring.

FIG. 4 is a plan view and a cross-sectional view showing an example of the wastewater treatment equipment of the present invention.

FIG. 5 is a plan view and a cross-sectional view showing another example of the wastewater treatment equipment of the present invention.

[Explanation of symbols]

1 Oroidal body 2 drive shaft Three arms 4 drive 5 cervical axis 6 Stirrer 7 Streamline in forward rotation 8 Streamline in reverse 9 Raw water and returned sludge 10 Treated mixed water 11 stirrer 12 Stirrer 13 Air diffuser 14 Air diffuser 15 anoxic zone 16 aerobic zone 17 Anoxic zone 18 aerobic zone

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Claims (2)

[Claims] 1. A method for biologically purifying wastewater through a circulating flow path, comprising a stirrer having a body for swinging and rotating motion in the middle of the flow path, whereby air is supplied and wastewater is discharged. A wastewater treatment method characterized by circulating. 2. A wastewater treatment device comprising a circulating flow path for biologically purifying wastewater, characterized by comprising an agitator having a body for rocking and rotating motion in the middle of the flow path. Wastewater treatment equipment.