JPH06320154A - Removal of scum in oxidation ditch - Google Patents

Abstract

PURPOSE:To remove scum on the surface of the water by involving scum in water and bringing the scum into contact with activated sludge to adsorb the same. CONSTITUTION:A screw-shaped aerator 3 or stirrer 4 fitted with a draft tube is arranged in an aeration tank 1 of an oxidation ditch method. The scum floating on the surface of the water is guided to the upper part of the aerator 3 or stirrer 4 by the surface stream in the aeration tank 1 and sucked from the upper end of the draft tube to be involved in water and brought into contact with activated sludge in water to be adsorbed and removed. By this constitution, the scum in an oxidation ditch can be efficiently removed by small energy and the deterioration of appearance accompanied by the stagnation of scum is prevented and the generation of an offensive smell/harmful inset is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention removes scum on the water surface by sucking foamed scum generated on the water surface with a screw type aerator equipped with a draft tube, winding the scum in water, contacting it with activated sludge and adsorbing it. The present invention relates to a method for removing scum in an oxidation ditch.

[0002]

2. Description of the Related Art Oxidation ditch method is used in small-scale sewage treatment plants. This oxidation ditch has a high concentration of activated sludge and a long retention time of the sludge, so that actinomycetes grow and foam in the activated sludge, and scum easily forms. However, in the conventional oxidation ditch, even if scum is generated, the scum also overflows together with the sludge mixture and is guided to the sedimentation pond, where it is removed by the scum skimmer in the sedimentation pond.

[0003]

When scum is generated in the oxidation ditch, some actinomycetes attach to the aerated bubbles and float on the water surface. Of these floating actinomycetes, those caught in vortices near the surface of the water return to the water again, but some floating scum adheres to the inner wall surface where the flow is small in the aeration tank, or where the flow is weak. When retained in, the actinomycetes repeatedly grow in that part and are abnormally proliferated. The growth of this actinomycetes increases in volume, and as a result, other scum accumulates in that part, and activated sludge is incorporated into the actinomycetes mesh structure to promote further growth, and the amount of water gradually increases. Will be covered. When scum propagates and accumulates in the oxidation ditch in this way, the scum itself anaerobically decomposes and gives off a bad odor, and flies and pests occur in the scum, which is unsanitary and significantly impairs the appearance. . There is also a problem that the aeration efficiency is reduced due to the scum covering the water surface.

The present invention introduces a scum floating on the water surface above the draft tube of an aerator or agitator provided in water,
The purpose is to remove the scum on the water surface by sucking it into the tube, winding the scum into the water, and contacting and adsorbing it with the activated sludge in the water.

[0005]

Means for Solving the Problems The present invention has been made to achieve the above object, and a screw type aerator or agitator with a draft tube is installed in an aeration tank of the oxidation ditch method to float on the water surface. The scum to be introduced is guided to the upper part of the aerator or agitator by the surface flow in the aeration tank, and the scum is sucked from the upper end of the draft tube to be caught in the water so that the scum comes into contact with the activated sludge in the water to remove it. To do.

[0006]

The scum generated on the water surface is sucked into the draft tube by being aerated or driven by an agitator provided in the water, and is taken into the water. The scum comes into contact with the activated sludge in water and is sucked. As a result, the scum becomes completely integrated with the activated sludge in the water and is completely taken into the water so that it cannot float on the water surface, and the scum on the water surface is easily removed.

[0007]

The method for removing scum in the oxidation ditch of the present invention will be described below with reference to the illustrated embodiment. In the figure, 1 is an aeration tank for biologically decomposing and removing organic wastewater (sewage) with activated sludge, which is installed in a small-scale sewage treatment plant, etc. This aeration tank 1 is generally oval as shown in the figure. Although it has a necessary internal volume in which a circulating water channel is formed, this shape is not necessarily limited, and it may be a circular shape or another shape other than the oval shape. Further, as shown in the drawing, a corner guide 2 is installed in the aeration tank 1 having an oval shape and a wide width so as to rectify and stabilize the flow.

In this aeration tank 1, one aerator 3 or a plurality of aerators 3 is installed at a predetermined position,
By operating the aerator 3, the waste water is aerated and agitated, and a water flow is generated in the circulating water channel.

As shown in detail in FIG. 1, the aerator 3 penetrates the hollow shaft 12 into a draft tube 15 having a required diameter bent in a V shape at a required angle, and the hollow shaft 12 is provided at the base end side thereof. The motor 13 is attached and the screw 11 is fixed to the tip side, and further the intake pipe 14 is attached to the motor shaft or the motor casing to which the hollow shaft is fixed. At the negative pressure generated by, the air is sucked in from the tip of the intake pipe above the water surface, flows down the hollow shaft, and when it is discharged into the water from the screw tip, it is crushed by the stirring flow and released as fine bubbles into the water. It is aerated. At this time, the upper end of the draft tube is installed at a predetermined position below the surface of the water so as to open upward 16.

The screw 11 provided at the tip of the hollow shaft penetrating through the draft tube 15 may be shaped so as to project into the water from the lower end of the draft tube as shown in the drawing, or may be located inside the draft tube.

When the screw is rotated by the motor in this structure, the waste water around the screw is agitated and a water flow pushed forward by the screw is generated. This allows the upper end opening 16 of the draft tube.
Sewage at a more water surface is sucked into the draft tube. At this time, as shown in FIG. 1, the scum a floating on the water surface is also sucked into the draft tube, crushed by the screw, contact-mixed with sludge, and pushed out into the screw tip water area by the water flow. At this time, the scum b adsorbed on the activated sludge in the wastewater is completely taken into the water.

FIG. 1 shows an embodiment in which an aerator 3 and an agitator 4 used to increase the agitating force in a water area are paired in an oval oxidation ditch, and they are arranged in a straight line portion of a circulating water channel. An oil fence-shaped scum collecting guide 5 is provided so that floating scum can be collected more reliably and sucked into the draft tube. Although the installation position of this guide is not limited, in order to collect scum more efficiently, it is desirable to make the angle with respect to the side wall as small as possible as shown in FIG. Select difficult materials. Furthermore, if water is sprinkled on the guide surface of the scum collecting guide 5, scum adhesion can be prevented,
Collecting can be done more effectively.

Next, the operation and action of the present invention will be described. When the screw type aerator 3 with a draft tube is operated, the screw 11 rotates, a stirring flow is generated, and a negative pressure is generated at the tip of the screw. Therefore, the air above the water is sucked from the opening in the upper part of the ventilation pipe 14, guided to the tip of the screw through the hollow shaft of the submersible motor 13 and the hollow shaft 12, and sheared by the screw edge to be miniaturized. When a screw type stirrer is used, only the stirring flow is generated by the screw. Due to the stirring flow generated by the rotation of the screw 11, a flow from the upper part of the draft tube to the screw 11 is generated in the draft tube 15. At this time, since the scum suction port 16 at the upper end of the draft tube is installed in the range of 10 mm to several tens of mm below the water surface, a vortex is generated at the upper part of the scum suction port 16 and suspended matter on the water surface such as scum a is aerated. It is sucked into the scum suction port together with the sludge mixed liquid in 1. On the other hand, a circulating flow as shown in FIG. 2 is formed on the surface of the aeration tank 1, and scum floating on the water surface reaches the scum collecting guide 5 and flows toward the screw type aerator 3 with a draft tube along the guide.
At this time, the scum suction port 1 is accelerated by the vortex flow generated above the draft tube 15 and reaches the draft tube.
6 is sucked and pushed out to the tip of the screw 11.
The scum b caught in the water comes into contact with the large amount of activated sludge existing in the water and is adsorbed.

[0014]

The method for removing scum in the oxidation ditch of the present invention provides a screw type aerator with a draft tube or an agitator in the aeration tank, collects the scum floating on the water surface, sucks it with the draft tube and entrains it in water. Since it is brought into contact with the activated sludge in water and adsorbed to the activated sludge, the scum in the oxidation ditch can be efficiently removed with less energy, and the deterioration of the appearance and the generation of odors and pests due to the retention of scum can be prevented. Have an effect.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of an aerator used in a scum removing method in an oxidation ditch of the present invention.

FIG. 2 is a plan view showing an embodiment of a scum removing method in the oxidation ditch of the present invention.

[Explanation of symbols]

 1 Aeration Tank 3 Aerator 11 Screw 12 Hollow Shaft 13 Motor 14 Vent Pipe 15 Draft Tube a Scum

Claims (1)

[Claims] 1. A screw type aerator or agitator with a draft tube is installed in an aeration tank of the oxidation ditch method, and scum floating on the water surface is provided on the aerator or agitator by the surface flow in the aeration tank. A method for removing scum in an oxidation ditch, which comprises guiding scum from the upper end of a draft tube, entraining it in water, contacting it with activated sludge in water, and removing it.