JPH04349993A - Operation of endless water channel - Google Patents

Abstract

PURPOSE:To adjust the installation angle of an aeration device installed in an endless water channel and thereby mix dirty water in the channel uniformly. CONSTITUTION:An aeration device 2 is installed in an endless water channel 13. In addition, a detection sensor 3 is installed in the water channel 13, and a mixed stirring state in the water channel is detected using the detection sensor 3. The installation angle of the aeration device is adjusted based on the detection information to mix the dirty water uniformly in the water channel.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operating method for uniformly mixing sewage in an endless waterway by adjusting the installation angle of an aeration device installed in the waterway.

0002

[Prior Art] When treating sewage containing organic matter such as sewage sewage and industrial waste sewage, an aeration system is installed in an aeration tank that has a so-called endless waterway, such as an oblong circulation waterway or a double circular waterway. A method has been proposed in which the sewage is mixed and stirred while continuously supplying oxygen from the air to the sewage in this tank to carry out aeration, that is, an aerobic fermentation process.

Conventionally, the standard activated sludge method has been widely used for sewage treatment in large cities, but today it is shifting to small and medium-sized cities in rural areas. Since there are few engineers in rural areas, the treatment method is simple, stable treated water quality can be changed,
In addition, a treatment method that can respond to fluctuations in the amount of inflowing sewage affected by tourist seasons, etc. is desired. Under these circumstances, the oxidation ditch method, which has a circular, or oval, endless waterway, meets the above needs.
It is steadily spreading to rural areas. In general, not only the oxidation ditch method but also the activated sludge method performs aerobic nitrification, so it requires an aerator to supply air and a stirring flow rate to bring dirty sludge into contact with wastewater. This stirring flow rate is usually
A bottom flow velocity of 10 cm/sec or more is required,
If the flow rate is lower than this, activated sludge will accumulate. In addition, if there is a difference in flow velocity between the inner and outer circumferences of the waterway, activated sludge will concentrate on the side with a slower flow velocity and an activated sludge gradient will be formed, which will not result in a complete mixing system, and in extreme cases, due to the viscosity, activated sludge will accumulate, and sufficient water treatment cannot be expected.

0004

[Problems to be Solved by the Invention] The installation angle of the aeration device in an endless waterway is determined from a comprehensive viewpoint based on the flow velocity characteristics, power characteristics, etc. of the aeration device. However, since the horizontal shaft aeration device is large and has both shaft ends fixed to both ends of the waterway, it is difficult to change the installation angle once it is installed. However, in actual operation, even if the flow rate of sewage supplied to the endless waterway, the water quality, and the amount of activated sludge in the aeration tank change from moment to moment, and the volume characteristics change, the stirring and aeration characteristics correspond to the flow rate characteristics. Since the sludge remains constant without changing, it has the disadvantage that sludge accumulates at the bottom of the waterway and is compacted, resulting in poor sewage treatment.

[0005] The present invention constantly detects the mixing and agitation situation in the waterway, adjusts the installation angle of the aeration device in accordance with the detected information, and constantly mixes and stirs the waterway uniformly to perform optimal wastewater treatment. With the goal.

[0006]

[Means for Solving the Problems] The present invention has been made to achieve the above object, and includes a detection sensor installed in an endless waterway in equipment for water treatment by installing an aeration device in an endless waterway. detecting the mixing and stirring situation in the waterway, and adjusting the installation angle of the aeration device based on this detection information,
The gist is that the wastewater in the waterway is mixed uniformly.

[0007]

[Operation] In an elliptical or circular endless waterway, streamlines gather at the outer periphery, so the flow velocity is slow at the inner periphery and faster at the outer periphery. In order to achieve this uniformity of the inner and outer peripheries with more energy-saving operation, sensors for mixing and agitation detection such as flow meters, sludge concentration meters, and DO meters are installed at at least two locations on the inner and outer peripheries of the waterway, and the aeration equipment uses the signal information from these sensors to detect mixing and stirring. The operation is performed by adjusting the bottom flow velocity ratio of the inner and outer peripheries, sludge concentration ratio, DO ratio, etc. so that mixing and agitation can be performed uniformly by adjusting the installation angle of the sludge as appropriate.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on the illustrated embodiments. What is shown in FIG. 1 is an embodiment using a double circular aeration tank with a circular endless water channel. In the figure, 1 is a double circular aeration tank, which has a small diameter circumferential wall 11 and a large diameter outer periphery 12.
are arranged concentrically, and a circulation waterway 13 having a required width and depth is formed between the inner and outer peripheral walls 11 and 12. Reference numeral 2 denotes a self-priming screw type aeration device, which is composed of a hollow shaft 23 directly connected to a motor 22 and a screw 24 installed at the tip of this shaft 23, as shown in detail in FIG. At the same time, the negative pressure generated at the tip of the screw is used to suck air through a hollow shaft and supply it as fine bubbles into the wastewater, so that the bubbles are efficiently dissolved in the water. It is. The aeration device 2 is installed on a mounting frame 21 disposed across the upper part of the water channel 13, the motor and hollow shaft are covered with a cover, and the motor etc. are mounted on the frame through this cover with an angle adjuster 25. Attach via.

Further, mixing and stirring detection sensors 3, 3 are installed in the water channel 13 at least on its inner and outer circumferential sides, respectively. The mixing and stirring detection sensor 3 includes a current meter,
Sludge concentration meters, DO meters, etc. are used, and sometimes two or more of these are used.

Next, a description will be given based on the experimental equipment and measurement positions shown in FIG. This experimental equipment is a double circular oxidation ditch with a processing capacity of approximately 600 cubic meters per day, and the aeration equipment is installed at an angle of 0° perpendicular to the radial direction, and thereafter the installation angle is gradually increased toward the inner circumference. The angle was changed to . The mixing and agitation state (flow rate and activated sludge concentration) was measured using a total of 20 measurement ports a to d provided on each of the cross sections A to D, and the power was provided by a mechanical measuring plate of the aeration device.

<Results> (1) The average flow velocity of the entire lower part becomes faster as the installation angle θ of the aeration device is increased and it is directed toward the inner circumference, reaching a maximum when θ = 31° and reaching a plateau at θ = 45°. (Figure 4)
. (2) The flow velocity distribution at the bottom of the aeration tank is slow on the inner circumference side and faster on the outer circumference side (Figure 5). (3) The inner balance of the average flow velocity at the bottom becomes more uniform as θ increases, and when θ=45°, the inner/outer ratio (a:d
) was 1:1.4, which was the closest to complete mixing (Figure 5). (4) The activated sludge concentration in the aeration tank is almost uniform when θ = 31°, but when θ = 6°, the average value in the tank is 810.
With respect to mg/l, sludge is deposited at a high level of 8000 mg/l or more on the inner peripheral side, and the sludge is below the average value on the outer peripheral side, so complete mixing is not achieved. (5) Power increased as θ increased. θ=4
At 5°, the shaft power was 3.73Kw, which exceeded the motor's rated value of 3.7Kw (Figure 7).

[0012] The operating method for an aeration system for an endless waterway having the above characteristics is as follows: (1) Adjust the installation angle so that the power of the aeration system is within the rated value of the motor. (2) Thoroughly mix the inside of the aeration tank to ensure stable water treatment. (3) Operating conditions should be such that running costs are low. However, in actual operation, when low-concentration activated sludge is used at the beginning of service, the flow velocity at the bottom is generally high, making it difficult for sludge to accumulate, and the residence time of sewage is long, making water treatment stable. Rather than simply installing the aeration device at the optimal installation angle to create a complete mixing system with an equal flow velocity ratio between the inner and outer circumferences, the installation angle is determined with due consideration given to running costs. On the other hand, if the amount of sewage generated and the concentration of activated sludge increase over time after the start of service, the flow velocity at the bottom of the aeration tank will eventually decrease and sludge will accumulate, so at this point the installation angle should be changed again. It is necessary to stir up the sludge and create a complete mixing system. In the present invention, as shown in Fig. 5, mixing and stirring detection sensors (for example, flow rate sensors) are attached to the inner and outer positions of the aeration tank, and in combination with an angle-adjustable aeration device, complete mixing can be achieved at all times. The installation angle of the aeration device is adjusted to reduce running costs. In other words, the installation angle of the aeration device varies somewhat depending on the scale of the aeration tank, but it is generally in the range of 0°≦θ≦45°, and preferably the installation angle is such that the bottom flow velocity ratio of the inner and outer circumferences is approximately 1:2. A completely mixed system can be achieved.

[0013] In this way, by measuring the flow rate in the aeration tank in real time and feeding it back to the aerator, good water treatment and low running costs are achieved. In addition, from the perspective of automating operation, this system is close to unmanned treatment plants. In the present invention, as in the above embodiment,
Although we have specified the combined operation using two flow velocity sensors on the inner and outer circumferences, it is also possible to simply operate the aeration system in conjunction with one flow velocity sensor installed at the representative measurement position, and the mixability in the aeration tank can be used as information. From this point of view, the system can be implemented even if a sludge concentration sensor or a DO concentration sensor is used instead of the flow rate sensor. In addition, as an application field, it is also applicable to an elliptical endless waterway, where the bottom flow velocity is slow at the inner periphery and faster at the outer periphery at the corner part, and the same tendency exists. The flowchart in FIG. 8 shows a method of operating an aerator according to the present invention, and FIG. 9 is an explanatory diagram of an electrical block diagram showing a method for adjusting the installation angle of the aerator using two flow rate sensors. .

[0014]

[Effects of the Invention] According to the present invention, a mixing/agitation detection sensor is provided in the waterway, and the installation angle of the aerator is adjusted and operated based on the signal information, so that the mixing of wastewater in the waterway is prevented. It has the advantage that agitation can be performed completely with low power and sewage treatment can be performed reliably without sludge being accumulated and consolidated on the bottom of the channel.

[Brief explanation of drawings]

FIG. 1 is a plan view showing a method of operating an endless waterway according to the present invention.

FIG. 2 is an explanatory diagram of an aeration device.

FIG. 3 is an explanatory diagram of the experimental equipment of the present invention.

FIG. 4 is a graph showing the relationship between the installation angle of the aeration device and the total bottom average flow velocity.

FIG. 5 is a bottom flow velocity distribution diagram.

FIG. 6 is a sludge concentration distribution map.

FIG. 7 is a diagram showing the relationship between the aeration device installation angle and power.

FIG. 8 is a flowchart of the aerator operation according to the present invention.

FIG. 9 is an electrical block diagram that adjusts the installation angle of the aeration device based on detection signals from two flow rate sensors.

[Explanation of symbols]

1 Aeration tank with endless waterway 13 Waterway 2 Aeration device 3 Detection sensor

Claims (1)

[Claims] Claim 1: In a facility that performs water treatment by installing an aeration device in an endless waterway, a detection sensor installed in the waterway detects the mixing and stirring situation in the waterway, and based on this detection information, the A method for operating an endless waterway, characterized in that the installation angle of an aeration device is adjusted to uniformly mix wastewater within the waterway.