JP2006075765A - Scum removal method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for removing scum by withdrawing it, where the scum is generated at an aerator, or the like, during waste water treatment with activated sludge and the method by which the concentration of the scum in mixed liquid containing the scum and activated sludge can be increased, and the efficiency of scum removal can be increased as a result. <P>SOLUTION: A scum removal apparatus is used which is provided with: a scum skimmer 2 for sucking the mixed liquid containing the scum and activated sludge floating in the vicinity of the water surface in a water treating tank; a force-feeding means 4 for force-feeding the mixed liquid sucked from the scum skimmer 2; and a scum concentrating tank 1 for temporarily storing the mixed liquid force-fed by the force-feeding means 4 and further returning the same to the water treating tank. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a scum removal method and apparatus capable of efficiently removing scum generated when wastewater is treated with activated sludge, and a wastewater treatment apparatus equipped with the scum removal apparatus.

  When purifying wastewater by the activated sludge method, actinomycetes are often generated in the treated water when wastewater containing a large amount of oil and fat discharged from a food factory or the like is to be treated. This actinomycete adheres to bubbles generated by aeration and generates scum. This scum causes problems such as overflow from the aeration tank.

Conventionally, in order to prevent the occurrence of this scum, measures such as sterilization of actinomycetes with chemicals and adjustment of the amount of aeration have been taken, but the effect has been insufficient.
For this reason, a symptomatic measure of removing once generated scum has been taken, and a method of removing scum using various scum skimmers, scum pumps, etc. is employed (see Patent Document 1).

However, those using a scum skimmer or scum pump have the disadvantages that the liquid mixture containing scum and activated sludge is drawn out, so that the scum concentration of the drawn liquid is low and the scum removal efficiency is low. For this reason, there also exists a fault that the efficiency at the time of dehydrating this drawing liquid is also bad.
JP-A-10-216410

  Therefore, the problem in the present invention is to increase the scum concentration in a mixed liquid containing scum and activated sludge in a method of removing scum generated in an aeration tank or the like when performing wastewater treatment with activated sludge. It is to be able to increase the scum removal efficiency.

To solve this problem,
According to the first aspect of the present invention, a mixed liquid containing scum and activated sludge floating near the water surface of the water treatment tank is sucked by a scum skimmer, and the mixed liquid is sent to the scum concentrating tank. A scum removal method characterized by increasing the scum concentration in the liquid mixture in the scum concentration tank by repeatedly sucking the scum again with the scum skimmer and drawing out the liquid mixture having a high scum concentration in the scum concentration tank. is there.
The invention according to claim 2 is the scum removal method according to claim 1, characterized in that the liquid mixture having a high scum concentration from the scum concentration tank is dehydrated.

According to a third aspect of the present invention, there is provided a scum skimmer for sucking a mixed liquid containing scum and activated sludge floating near the water surface of a water treatment tank, a pressure feeding means for pumping the mixed liquid sucked from the scum skimmer, A scum removal characterized by comprising a scum concentrating tank that temporarily stores the liquid mixture pumped by the pressure feeding means, returns a part of the liquid mixture to the water treatment tank, and sucks the remainder into the scum skimmer. Device.
The invention according to claim 4 is the scum removing device according to claim 3, further comprising a dehydration processing device for extracting the mixed solution from the scum concentration tank and dehydrating the mixed solution.

  A fifth aspect of the present invention is a wastewater treatment apparatus in which the scum removing device according to the third or fourth aspect is installed in a water treatment tank.

  According to the present invention, the scum concentration in the liquid mixture in the scum concentration tank gradually increases. Therefore, the scum can be efficiently removed by discharging the liquid mixture having a high scum concentration. Therefore, the failure | damage by the scum in a water treatment tank can be prevented. Furthermore, since high-concentration scum and sludge can be drained, the disposal of this product becomes easy and the processing cost is also low.

1 and 2 show an example of the scum removing device of the present invention.
In these drawings, reference numeral 101 denotes a scum removing device. The scum removing device 101 is provided in the vicinity of the water surface of a water treatment tank (not shown) such as an aeration tank.
The scum removing device 101 is generally composed of a scum concentrating tank 1, a scum skimmer 2, and a pneumatic inlet pipe 4 that functions as a pressure feeding means. The scum concentration tank 1 further includes a front tank 11, an intermediate tank 12, and a rear tank 13.
A scum skimmer 2 is provided in the front tank 11. As this scum skimmer 2, for example, a commercially available float scum skimmer can be used as it is.

As shown in FIG. 2, the scum skimmer 2 in this example includes two floats 21 and 21 and one scum suction pipe 22, and two floats on both sides near the opening of the scum suction pipe 22. 21 and 21 are attached.
The scum skimmer 2 floats on the water surface by placing a weight such as sand or water in the floats 21 and 21 so that the opening of the scum suction pipe 22 is slightly submerged than the water surface. It has become.

The lower portion of the scum suction pipe 22 of the scum skimmer 2 extends downward through the bottom of the front tank 11, and the lower portion is movably inserted into one end side of the communication pipe 3. The vertical movement due to the fluctuation of the water level is allowed.
The communication pipe 3 is U-shaped, and an end portion of the rising portion is open to the bottom of the rear tank 13.

Also, a pneumatic input pipe 4 is connected to the rising portion of the communication pipe 3, and air is blown into the mixed liquid in the communication pipe 3 from the pneumatic input pipe 4. A flow, that is, a flow in which the mixed solution sucked from the scum suction pipe 22 flows into the rear tank 13 through the communication pipe 3 is formed. The press-fitting of air from the pneumatic fitting pipe 4 is a pressure feeding means in this example.
In addition, without providing the pneumatic inlet pipe 4, a normal pump may be attached to the communication pipe 3 to create the above-described mixed liquid flow.

The said rear tank 13 is comprised so that the full water level may become higher than the full water level of the other front tank 11 and the intermediate tank 12, so that the liquid mixture from the rear tank 13 may overflow into the intermediate tank 12. It has become.
The intermediate tank 12 is partitioned by a front tank 11 and a partition wall 14, and the mixed liquid flows into the front tank 11 from the intermediate tank 12 through the lower part of the partition wall 14.

The intermediate tank 12 is provided with one end of the drainage pipe 5 facing the opening in the mixed liquid. The drainage pipe 5 is connected to a pump 51 to draw out the mixed liquid in the intermediate tank 12 and send it to a dehydration processing apparatus (not shown).
Further, the intermediate tank 12 is provided with a water level switch (not shown) for controlling the operation of the pump.

As shown in FIG. 2, the front tank 11 is provided with a float anti-skid plate 15 that prevents the floats 21 and 21 of the scum skimmer 2 from floating. Further, a wall portion 16 is provided at the front portion of the front tank 11. The height of the wall portion 16 is set lower than the water level of the water treatment tank, and the mixed liquid from the front tank 11 passes over the upper portion of the wall portion 16 and flows into the water treatment tank.
And, as shown in FIG. 1, such a scum removing device is provided in the water treatment tank so that the position of the upper end of the wall portion 16 of the front tank 11 is lower than the water level W of the water treatment tank. It is arranged.

  In the scum removing device having such a structure, of the mixed liquid flowing into the front tank 11 from the water treatment tank, the mixed liquid containing scum and activated sludge that floats on the water surface is supplied from the scum suction pipe 22 of the scum skimmer 2. It is sucked and passes through the communication pipe 3 and flows into the rear tank 13. This mixed liquid further overflows from the rear tank 13 and flows into the intermediate tank 12, then enters the front tank 11 through the partition wall 14, and part of the mixed liquid is again scumed together with the scum that newly flows from the water treatment tank. Inhaled by skimmer 2. Moreover, the remaining part will get over the wall part 16 of the front tank 11, and will flow out to a water treatment tank.

And by continuing the circulation of such a liquid mixture continuously or intermittently, the scum density | concentration in the liquid mixture in the intermediate tank 12 becomes high gradually. That is, the mixed liquid containing scum overflowing from the rear tank 13 and flowing into the intermediate tank 12 passes through the partition wall 14 and flows into the front tank 11 and is sucked into the scum skimmer 2 together with the scum on the water surface. Concentration increases. By repeating this operation, the scum concentration in the mixed liquid gradually increases, and the scum is concentrated in the intermediate tank 12.
The mixed liquid having a high scum concentration in the intermediate tank 12 is drawn out from the drain pipe 5 and dehydrated.
In this way, the scum of the water treatment tank is removed.

Such a scum removing device is installed and used at a position close to the water surface inside a water treatment tank constituting the waste water treatment apparatus, such as an aeration tank or a sedimentation tank, so that the water level W shown in FIG. Provided.
FIG. 3 shows an example in which the scum removing device shown in FIGS. 1 and 2 is installed in an aeration tank (water treatment tank) of a wastewater treatment apparatus.

  In FIG. 3, the treated raw water is sent to the adjustment tank 31, and after the amount of water is adjusted here, it is sent to the first fluidized bed 33 by the pump 32. In the first fluidized bed 33, the treatment is performed using a porous carrier carrying activated sludge. The treated water from the first fluidized bed 33 is sent to the second fluidized bed 34 and subjected to the same treatment, and then overflows into the first aeration tank 35 where it is aerated and treated with activated sludge.

The first aeration tank 35 is provided with the scum removing device 36 described above, and the above-described operation is performed to remove the scum generated in the first aeration tank 35.
Waste water from the first aeration tank 35 is sent to the second aeration tank 37, and after receiving the same aeration process, it is sent to the submerged film tank 38 by a pump.

The submerged membrane tank 38 uses a separation membrane, filters waste water flowing into the submerged membrane tank 38 and separates it into sludge and the like, and the treated water is sent to the outside. Sludge and the like are sent to the sludge storage tank 39 by a pump and temporarily stored.
The sludge in the sludge storage tank 39 is further extracted by a pump and sent to the agglomeration and mixing tank 40, where a flocculating agent such as PAC or polymer flocculant is added and agglomerated.
The agglomerated solid content is dehydrated by the dehydrator 41 and discharged to the outside as a dehydrated cake.

  Further, in this example, the liquid mixture having a high scum concentration of the scum removing device 36 is sent to the agglomeration mixing tank 40 through the drain pipe 5 and dehydrated in the same manner as the sludge from the sludge storage tank 39. Yes.

  In such a wastewater treatment apparatus, since the scum generated in the first aeration tank 35 is removed by the scum removal apparatus 36, these treatments do not flow into the treatment tanks after the second aeration tank 36 in the subsequent stage. The tank will not be damaged by scum.

  In the present invention, the processing tank in which the scum removing device is installed is not limited to the first aeration tank shown in FIG. 3, but a precipitation tank, a raw water tank, an oil separation tank, or the like that may cause scum. Can be installed.

It is a schematic sectional drawing which shows an example of the scum removal apparatus of this invention. FIG. 2 is a schematic plan view of the scum removing device shown in FIG. 1. It is a schematic block diagram which shows the example of the waste water treatment apparatus which attached the scum removal apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Scum thickening tank, 2 ... Scum skimmer, 3 ... Communication pipe, 4 ... Air introduction pipe, 40 ... Coagulation mixing tank, 41 ... Dehydrator

Claims (5)

  A mixed solution containing scum and activated sludge floating near the water surface of the water treatment tank is sucked by the scum skimmer, this mixed liquid is sent to the scum concentrating tank, and this mixed liquid and scum are again sucked by the scum skimmer. A scum removal method characterized by increasing the scum concentration in the mixed solution in the scum concentrating tank by repeating this and drawing out the mixed liquid having a high scum concentration in the scum concentrating tank.   The method for removing scum according to claim 1, wherein the mixed solution having a high scum concentration from the scum concentration tank is dehydrated.   A scum skimmer for sucking a mixed liquid containing scum and activated sludge floating near the surface of the water treatment tank, a pressure feeding means for pumping the mixed liquid sucked from the scum skimmer, and a liquid mixture pumped by the pressure feeding means A scum removing device comprising a scum concentrating tank that temporarily stores a part of the mixed liquid, returns a part of the mixed liquid to the water treatment tank, and sucks the remaining part into a scum skimmer.   4. The scum removing device according to claim 3, further comprising a dehydrating device for extracting the mixed solution from the scum concentrating tank and dehydrating the mixed solution. A wastewater treatment apparatus, wherein the scum removal device according to claim 3 or 4 is installed in a water treatment tank.

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