JP2923411B2 - How to remove scum from oxidation ditch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method in which foamed scum generated on the water surface is sucked by a screw-type aerator or stirrer with a draft tube, the scum is wound into water, and brought into contact with activated sludge to be adsorbed. The present invention relates to a method for removing scum in an oxidation ditch in which scum on a water surface is removed.

[0002]

2. Description of the Related Art In small-scale sewage treatment plants, an oxidation ditch method is employed. This oxidation ditch has a high concentration of activated sludge and a long residence time of the sludge, so that actinomycetes proliferate and foam in the activated sludge, and scum is easily formed. However, in the conventional oxidation ditch, even if scum is generated, the scum is caused to overflow together with the sludge mixed solution, guided to the sedimentation basin, and removed by the scum skimmer of the sedimentation basin.

[0003]

The generation of scum in the oxidation ditch causes a part of actinomycetes to adhere to the aerated air bubbles and float on the water surface. Of these suspended actinomycetes, those that are caught in the vortex near the water surface return to the water again, but some floating scum adheres to the inner wall of the aeration tank where the flow is small, or where the flow is weak. , The actinomycetes repeat the growth in that portion and abnormally grow. The growth of this actinomycete increases in volume, which causes other scum to accumulate in that part, and also takes up activated sludge into the network structure of the actinomycete, which further promotes the growth and gradually increases the amount. It will cover the water surface. When scum is multiplied and accumulated in the oxidation ditch in this way, the scum itself anaerobically rots and emits a bad smell, and flies and pests are generated in the scum, which is unsanitary and significantly impairs the appearance. . In addition, there is a problem that aeration efficiency is reduced by a scum covering the water surface.

According to the present invention, a scum floating on the water surface is guided above a draft tube of an aeration or agitator provided in water,
An object of the present invention is to remove the scum on the water surface by sucking the scum into the water by sucking into the tube and contacting and adsorbing 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 an oxidation ditch method. An oil fence-like scum collection guide extending from the position of the side wall on the upstream side of the position where the stirrer is installed to the aerator or the stirrer is arranged, and the scum floating on the water surface is removed by the surface flow in the aeration tank or the aerator. The method is characterized in that the scum is guided above the stirrer, sucked from the upper end of the draft tube, engulfed in water, and removed by contacting and adsorbing with activated sludge in the water.

[0006]

The scum generated on the water surface is sucked into the draft tube by the aeration provided in the water or driven by the stirrer, and is taken into the water. The scum contacts the activated sludge in the water and is sucked. This makes it impossible for the scum to be completely taken into the water together with the activated sludge in the water and float on the water surface, and the scum on the water surface is easily removed.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for removing scum in an oxidation ditch according to the present invention will be described with reference to the illustrated embodiment. In the figure, reference numeral 1 denotes an aeration tank for biologically decomposing and removing organic waste water (sewage) installed in a small-scale sewage treatment plant or the like by activated sludge. Has a required internal volume in which a circulating water channel is formed, but this shape is not necessarily limited, and may be a circular shape or any other shape in addition to an oval shape. Also, a corner guide 2 is installed in the aeration tank 1 having a wide oval shape to rectify and stabilize the flow as shown in the figure.

[0010] One or more aerators 3 are installed at predetermined positions in the aeration tank 1, and the operation of the aerator 3 aerates and agitates the sewage, and controls the flow of water into the circulation channel. To be generated.

As shown in FIG. 1, the aerator 3 penetrates a hollow shaft 12 into a draft tube 15 of a required diameter bent at a required angle into an oval shape. A screw 13 is fixed to the distal end side while a motor 13 is attached to the motor shaft, and an intake pipe 14 is attached to a motor shaft or a motor casing to which a hollow shaft is further fixed. That is, air is sucked from the tip of the intake pipe 14 above the water surface by the negative pressure generated in the water area at the tip of the screw 11. When the sucked air flows down in the hollow shaft 12 and is discharged into the water from the tip of the screw 11, it is crushed by the agitated flow to be released as fine bubbles into the water, thereby performing aeration. At this time, the draft tube 15
The upper end is installed at a predetermined position below the water surface so as to open upward.

The screw 11 provided at the tip of the hollow shaft 12 penetrating through the draft tube 15 may have a shape protruding into the water from the lower end of the draft tube 15 as shown in the drawing, or may be located in the draft tube 15. Can also.

In such a configuration, when the screw 11 is rotated by the motor 13, the sewage around the screw 11 is agitated, and a water flow pushed out by the screw 11 is generated. Thereby, the sewage at the water surface position is sucked into the draft tube 15 through the opening 16 at the upper end of the draft tube 15. At this time, as shown in FIG. 1, the scum a floating on the water surface is sucked into the draft tube 15 together with the sewage, crushed by the screw 11, mixed with the sludge, and pushed out into the water area at the tip of the screw 11 by the water flow. It is. And
Scum b pushed into the water area at the tip of screw 11
Is adsorbed by the activated sludge in the sewage and is completely taken into the water.

In this case, as shown in FIG. 1, an aerator 3 and a stirrer 4 used to increase the stirring force in the water area are arranged in a pair in a straight portion of a circulation channel in the oxidation ditch 1 having an oval shape. At the same time, an scum collection guide 5 in the form of an oil fence is provided so that the scum a floating on the water surface is more reliably collected and sucked into the draft tube 11. The scum collection guide 5 is installed so as to extend from the position of the side wall on the upstream side of the position where the aerator 3 or the stirrer 4 is installed to the aerator or the stirrer. In order to collect the scum a more efficiently, As shown in FIG. 2, it is desirable to minimize the angle with respect to the side wall,
Further, as the material, a material to which scum is unlikely to adhere is selected. Further, if water is sprayed on the guide surface of the scum collection guide 5, scum is prevented from adhering and collection can be performed more effectively.

Next, the operation and operation of the present invention will be described. When the screw-type aerator 3 with the draft tube is operated,
As the screw 11 rotates, a stirring flow is generated and a negative pressure is generated at the tip of the screw 11. Thereby, the air above the water is sucked from the upper opening of the ventilation pipe 14, guided to the tip of the screw 11 through the hollow shaft and the hollow shaft 12 of the underwater motor 13, and sheared by the screw edge to be miniaturized. . When a screw-type stirrer is used, only a 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 15 toward the screw 11 is generated in the draft tube 15. At this time, the opening 16 at the upper end of the draft tube 15 is 10 mm to several tens of meters below the water surface.
m, a vortex is generated above the opening 16, and suspended matter on the water surface such as scum a is sucked from the opening 16 together with the sewage in the aeration tank 1. On the other hand, a circulating flow as shown in FIG. 2 is formed on the surface of the aeration tank 1, and the scum a floating on the water surface reaches the scum collection guide 5 and is formed along the scum collection guide 5 in the form of a screw with a draft tube. It flows toward the aerator 3. Then, it is accelerated by the vortex generated in the upper part of the draft tube 15, reaches the draft tube 15, is sucked by the opening 16 and is pushed out to the tip of the screw 11. The scum b entrained in the water comes into contact with and adsorbs activated sludge which is present in a large amount in the water.

[0014]

According to the method for removing scum in the oxidation ditch of the present invention, a screw-type aerator or stirrer with a draft tube is installed in the aeration tank, and the upstream side of the position where the aerator or stirrer is installed. An oil fence-shaped scum collection guide extending from the position of the side wall to the aerator or stirrer is provided, and the scum floating on the water surface is guided above the aerator or stirrer by the surface flow in the aeration tank, and the draft tube Since the scum is sucked from the upper end, caught in the water, and is contacted and removed with the activated sludge in the water, the scum in the oxidation ditch can be reliably and efficiently removed with little energy,
Deterioration of appearance and generation of odors and pests due to scum retention can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of an oxidation ditch facility used in a method for removing scum in an oxidation ditch according to the present invention.

FIG. 2 is an explanatory diagram showing an operation of a method for removing scum in an oxidation ditch of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Aeration tank 3 Aerator 11 Screw 12 Hollow shaft 13 Motor 14 Ventilation pipe 15 Draft tube a Scum b Scum

Claims (1)

(57) [Claims] 1. A screw-type aerator or stirrer with a draft tube is installed in an aeration tank of the oxidation ditch method, and the aerator or stirrer is positioned from the position of the side wall on the upstream side of the position where the aerator or the stirrer is installed. A scum collection guide in the form of an oil fence is provided, and the scum floating on the water surface is guided above the aerator or stirrer by the surface flow in the aeration tank, and the scum is suctioned from the upper end of the draft tube into the water. A method for removing scum in an oxidation ditch, wherein the scum is removed by contact and adsorption with activated sludge in water.