JPH07196B2 - How to operate an endless waterway - Google Patents

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 a waterway by adjusting the installation angle of an aeration device installed in an endless waterway.

[0002]

2. Description of the Related Art In the treatment of sewage sewage, industrial waste sewage, and other sewage containing organic matter, an aeration device is installed in an aeration tank that forms a so-called endless channel such as an oval circulation channel or a double circular channel. A method has been proposed in which sewage is mixed with agitation while continuously supplying oxygen in the air to the sewage in the tank to aerate, that is, aerobically fermenting treatment is performed.

Conventionally, sewage treatment has been popularized mainly in the standard activated sludge method in big cities, but nowadays it is shifting to local small and medium cities. Since there are few engineers in rural areas, there is a need for a treatment method that is simple, that provides stable treated water quality, and that can cope with fluctuations in the amount of inflowing wastewater that is affected by the tourist season. Circular in this situation,
Or, an oxidation ditch having an oval endless water channel meets the above needs and is steadily spreading to rural areas. In general, not only the oxidation ditch method but also the activated sludge method performs aerobic fermentation processing, and thus it is necessary to supply air by an aeration device and a stirring flow rate for contacting the activated sludge with waste water. This stirring flow rate is usually required to have a bottom flow rate of 10 cm / sec or higher, and if the flow rate is lower than this, activated sludge will be deposited. Also,
If there is a flow velocity difference between the inside and outside of the water channel, the activated sludge concentrates on the slower flow velocity side to form an activated sludge gradient, which does not form a complete mixing system. As a result, sufficient water treatment cannot be expected.

[0004]

The installation angle of the aeration device in the endless water channel is determined from a comprehensive point of view based on the flow velocity characteristics and power characteristics of the aeration device. However, since the horizontal axis aerator is large and both shaft ends are fixed to both ends of the water channel, it is difficult to change the installation angle once installed. However, in actual operation, even if the flow velocity characteristic changes due to the flow rate of sewage supplied to the endless water channel, the water quality, and the amount of activated sludge in the aeration tank changing momentarily, the stirring and aeration characteristics are Since it does not change according to the flow velocity characteristic and is constant, sludge is accumulated and compacted at the bottom of the water channel, and there is a drawback that good wastewater treatment cannot be performed.

The present invention constantly detects the mixing and stirring condition in the water channel, adjusts the installation angle of the aeration device in accordance with the detection information, always uniformly mixes and stirs the water channel, and performs the optimum wastewater treatment. It is an object of the present invention to provide a method for operating an endless water channel that enables the above.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object, and is an endless water channel operating method for treating water by installing an aerator in the endless water channel. The flow velocity sensors installed on the inner and outer circumferences of the inside detect the flow velocity on the inner and outer sides of the endless water channel, and the ratio of the detected flow velocity on the inner and outer sides of the endless water channel is within the specified range. If it is out of the range, the installation angle of the aeration device is adjusted to automatically control so that the ratio of the flow velocities on the inner peripheral side and the outer peripheral side of the endless water channel is within a predetermined range.

[0007]

In the oval or circular endless water channel, streamlines gather at the outer peripheral portion, so the flow velocity at the inner peripheral portion is slow and the outer peripheral portion is fast. In order to realize this homogenization of the inner and outer circumferences in energy-saving operation, the flow velocity sensors installed on the inner and outer circumferences of the endless water channel detect the flow velocity on the inner and outer circumferences of the endless water channel. If the ratio of the flow velocities on the inner circumference side and the outer circumference side is out of the predetermined range, the installation angle of the aeration device is adjusted so that the ratio of the flow velocities on the inner circumference side and the outer circumference side of the endless water channel falls within the predetermined range. Therefore, the endless water channel is always mixed and stirred uniformly so that the wastewater treatment is performed under the optimum conditions.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the illustrated embodiments. FIG. 1 shows an embodiment using a double circular aeration tank having 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 circumference 12.
Are arranged concentrically, and a circulating type endless water channel 13 having a required width and depth is formed between the inner and outer peripheral walls 11, 12. Reference numeral 2 denotes a self-priming screw type aerator, which is composed of a hollow shaft 23 directly connected to the motor 22 and a screw 24 provided at the tip of the shaft 23, as shown in FIG. Along with raising it, air is sucked through the hollow shaft by using the negative pressure of the screw tip that is generated along with it, and it is supplied as fine bubbles into the dirty water, and the bubbles are efficiently dissolved in the water. Is. Aeration device 2 is endless water channel 1
The motor and the hollow shaft are covered with a cover, and the motor and the like are mounted on the frame via the mounting angle adjuster 25 through the cover.

Further, in the endless water channel 13, the mixing and stirring detecting sensors 3, 3 are attached at least on the inner peripheral side and the outer peripheral side thereof. As the mixing and stirring detection sensor 3, a sludge concentration meter, a DO meter, or the like can be used in addition to the velocity meter.

Next, description will be made on the basis of the experimental equipment and measurement positions shown in FIG. This experimental equipment is a double circular oxidation ditch with a processing capacity of about 600 cubic meters per day, and the installation angle of the aerator is perpendicular to the radial direction is 0 °. I changed the angle. The measurement of the mixed stirring state (flow velocity and activated sludge concentration) was carried out at a total of 16 points a to d provided from the inner peripheral side to the outer peripheral side in the cross sections A to D.

<Results> (1) The average flow velocity at the bottom becomes faster as the installation angle θ of the aerator is increased and it is directed toward the inner circumference side. When θ = 31 °, the average flow velocity reaches its maximum, reaching θ = 45 ° and reaching a peak condition. (Fig. 4). (2) The bottom flow velocity distribution in the aeration tank is slower on the inner side and faster on the outer side (Fig. 5). (3) The inner peripheral side balance of the bottom average flow velocity becomes uniform as θ increases, and when θ = 45 °, the internal / external ratio (a:
The ratio d) was 1: 1.4, which was the closest to perfect mixing (Fig. 5). (4) The concentration of activated sludge in the aeration tank is almost uniform when θ = 31 °, but when θ = 6 °, the average value in the tank is 810.
The inner peripheral side is as high as 8,000 mg / liter or higher with respect to mg / liter, sludge is accumulated on the inner peripheral side, and the outer peripheral side is below the average value and is not completely mixed. (5) The power increased as θ increased. θ = 4
At 5 °, the shaft power was 3.73 KW, which was above the motor rated value of 3.7 KW (Fig. 7).

The order of operating method of the aerator of the endless water channel having the above characteristics is as follows: (1) The installation angle is adjusted so that the power of the aerator is within the rated value of the motor. (2) Completely mix the inside of the aeration tank for stable water treatment. (3) The operating conditions should be such that the running cost is low. However, in actual operation, when the low-concentration activated sludge at the start of service is used, the bottom flow velocity is generally high, sludge is hard to accumulate, and the retention time of wastewater is long and the water treatment is stable. It is more preferable not to simply install the aerator at an optimal installation angle in order to create a complete mixing system in which the flow rate ratios of the inner and outer circumferences are equal, but to set the installation angle with due consideration given to the running cost. On the other hand, if the amount of generated wastewater and the concentration of activated sludge increase with time from the start of service, the bottom flow velocity will eventually decrease in the aeration tank and sludge will accumulate, so at this point the installation angle must be changed again. It is necessary to roll up the sludge to make a completely mixed system. In the present embodiment, as shown in FIG. 5, sensors for mixing and stirring (specifically, flow velocity sensors) are attached to the inner and outer peripheral sides in the aeration tank, and combined with an aerator capable of adjusting the angle, it is always perfect. The installation angle of the aeration device is adjusted so that the mixing can be performed and the running cost is low. That is, although the installation angle of the aeration device is somewhat different depending on the scale of the aeration tank, it is generally in the range of 0 ° ≦ θ ≦ 45 °, and preferably the installation angle at which the bottom flow velocity ratio of the inner and outer circumferences approximates 1: 2. A completely mixed system can be obtained with.

As described above, by measuring the flow velocity in the aeration tank in real time and feeding it back as the installation angle of the aeration device, it is possible to perform good water treatment, reduce the running cost, and reduce the aeration device. Driving can be automated. Further, as an application field, even in an oval endless water channel, the bottom flow velocity at the corner portion is slow at the inner circumference and fast at the outer circumference, and the same tendency is exhibited, so that the present invention can be applied. The flow of FIG.
The chart shows the operation method of the aerator, and the flow velocity sensor A installed on the inner peripheral side of the endless water channel and the flow velocity sensor B installed on the outer peripheral side show the flow velocity on the inner peripheral side and the outer peripheral side of the endless water channel. If the ratio of the flow velocities on the inner circumference side and the outer circumference side of the detected endless water channel deviates from the predetermined range (specifically, within 1: 2), the installation angles of the two aeration devices are adjusted. Then, it is automatically controlled so that the ratio of the flow velocities on the inner circumference side and the outer circumference side of the endless water channel is within a predetermined range. Further, the electric block diagram of FIG. 9 is an explanatory diagram showing a method of calculating the flow velocity distribution and sludge accumulation by the two detection sensors 3 and 3 and adjusting the installation angle of the aeration device based on the calculation.

[0014]

According to the present invention, the installation angle of the aeration device can be adjusted so that the ratio of the flow velocities on the inner peripheral side and the outer peripheral side of the endless water channel is within a predetermined range. As a result, it is possible to always mix and stir the inside of the endless water channel uniformly and perform the wastewater treatment under optimum conditions.

[Brief description of drawings]

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

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

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

FIG. 4 is a graph showing the relationship between the installation angle of the aeration device and the average flow velocity at all bottoms.

FIG. 5 is a bottom flow velocity distribution map.

FIG. 6 is a sludge concentration distribution map.

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

FIG. 8 is a flowchart showing the method of operating the aeration apparatus according to the present invention.

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

[Explanation of symbols]

 1 Aeration tank with endless water channel 13 Endless water channel 2 Aeration device 3 Detection sensor

Claims (1)

[Claims] 1. A method of operating an endless waterway in which an aerator is installed in the endless waterway to perform water treatment, wherein in the endless waterway, a flow velocity sensor is installed on the inner and outer circumference sides of the endless waterway. When the flow velocities on the circumference side and the outer circumference side are detected and the ratio of the flow velocities on the inner circumference side and the outer circumference side of the detected endless water channel deviates from a predetermined range, the installation angle of the aeration device is adjusted to A method for operating an endless water channel, which is characterized by automatically controlling so that the ratio of the flow velocities on the inner peripheral side and the outer peripheral side falls within a predetermined range.