JPH08257557A - Treatment method for foamed scum - Google Patents

Abstract

PURPOSE: To treat foamed scum by a method in which the scum is concentrated in a concentration tank, the concentrated scum is collected on the water surface to be defoamed by water spray, the scum which is restored to a form of sludge is concentrated by gravity to be treated by a sludge dewatering machine. CONSTITUTION: A scum flow obstruction wall 8 is installed radially on the water surface of a circular treatment tank equipped with a scum scraping machine to obstruct the following turn of foamed scum by a scum scraper 72. The operation of the scum scraping machine is periodically stopped for a while to collect the foamed scum efficiently between the scum flow obstruction wall 8 and the scum scraper 72 for defoaming treatment by water spray.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention relates to a sewage treatment system in which a scum in a sedimentation tank or a scum treatment tank provided for concentrating foam scum is collected and efficiently settled by sprinkling for treatment. The present invention relates to a method for treating foam scum.

[0002]

2. Description of the Related Art In the treatment of sewage, aeration of sewage causes a large amount of foam scum to be generated in a treatment tank and float on the water surface of the tank. This foamed scum is that soil bacteria (actinomycetes) aerate and abnormally proliferate, and become foamed scum in the aeration tank. The foamed scum floats above the surface of the final settling basin to make it look unattractive and overflow with the treated water to deteriorate the water quality. As a countermeasure, there is a removal method using a scum skimmer, but since the properties of the foam scum are soft and it contains a large amount of water, it is difficult to separate it as a solid content, and after removal it is returned to the inlet of the sewage treatment plant as scum return water. There is.

[0003]

However, in this method, the foam scum cannot be completely removed, and residual actinomycetes circulate in the sewage treatment system. Therefore, when the actinomycete flows into the aeration tank, foam scum is formed again. , It floats on the surface of the water.

The present invention concentrates foam scum in a thickener,
The purpose is to collect this on the surface of the water, defoam it by sprinkling it, return it to the sludge state again, gravity concentrate it, and treat it with a sludge dehydrator.

[0005]

The present invention has been made to achieve the above object, and a scum baffle wall is provided on the water surface in the radial direction of a circular processing tank equipped with a scum scraper. , Prevents the foam scum from going around with the scum draw plate,
In addition, the scum crawler that makes an orbital motion is temporarily stopped, and the foam scum is efficiently collected between the scum baffle wall and the scum crawler plate to perform defoaming treatment by watering.

[0006]

Operation: A scum blocking wall is provided on the water surface in the radial direction of a circular treatment tank equipped with a scum scraper to prevent the foam scum from being circulated by the scum scraper plate and to move around the scum scraper. By periodically suspending the stop machine, the foam scum can be efficiently collected and concentrated between the scum barrier wall and the scum draw plate, and this is defoamed by sprinkling and returned to the sludge state. Therefore, the processing of the foam scum can be efficiently performed.

[0007]

The method for treating the foamed scum of the present invention will be described below with reference to the illustrated embodiment. Fig. 3 is a flow chart of sewage treatment in which sewage (sewage) flowing into the sewage treatment plant is concentrated in an enrichment tank via an aeration tank and then led to the final settling tank for treatment, where 1 is wastewater from each household or the like. A raw water tank 2 for collecting and inflowing sewage is a raw water tank 1, which is an aeration tank for supplying sludge or the like in which solid-liquid is separated in advance through a pump P or the like to perform aeration treatment.

Since the foamed scum generated in the aeration tank 2 floats on the water surface, it can be efficiently overflowed from the aeration tank by a combination of the stirring flow in the aeration tank, the air flow of the blower and the oil fence. , To the residue screen 6. In this residue screen 6, the water sent from the aeration tank and the final sedimentation tank is pretreated for the purpose of removing the residue that has a property different from that of the foam scum such as a plastic bag and sanitary goods, and then Ensure that foam scum can be treated in the process.

A final settling tank 3 is connected to the aeration tank 2 to supply a sludge component to be separated and removed in the aeration tank, the solid content in the sludge is separated in the final sedimentation tank 3, and the solid content ( A part of the sludge is returned to the aeration tank 2 to be returned sludge, and the other sludge is sent to the sludge concentration storage tank 4 to concentrate and temporarily store it. The supernatant water generated here is discharged as treated water.

A sludge dewatering machine 5 is installed in the sludge thickening storage tank 4, and the concentrated sludge is further dehydrated and discharged so as to have a predetermined water content, and the desorbed water generated here is recovered to collect the raw water tank 1. To reprocess and reprocess.

The residue screen 6 has a foam scum concentrating tank 7
Connect. In the foam scum concentrating tank 7, the foam scum pretreated by the residue screen 6 is defoamed to be gravity precipitated and concentrated. The foam scum concentrate has the same actinomycetes / sludge microbial ratio as the aeration tank mixed solution, and it becomes foam scum concentrate, that is, sludge concentrate, and is mixed with the excess sludge drawn from the final settling tank 3, Sludge treatment is possible.
Since 95 to 99% of the actinomycetes can be recovered in the sludge dehydration treatment, the actinomycetes in the system can be reduced by carrying out the dehydrated cake.
The number of actinomycetes contained in this foamed scum is about 10 million per 1 g of foamed scum, which is higher than that of the aeration tank mixed solution.
The concentration is 10 times or more, and the ratio of actinomycetes and sludge microorganisms is the same in both foam scum and mixed solution. That is, since the defoamed material of the foam scum is the sludge itself, ordinary sludge dewatering treatment is possible, and the recovery rate of actinomycetes by the sludge dewatering machine is 95 to 99%, which is an efficient treatment.

Since the actinomycetes of the desorbed water by the dehydrator 5 are reduced to the same level as the inflowing sewage, about 1000 to 10000 / ml, it can be returned to the raw water tank 1. In some cases, it may be sterilized by a means such as chlorine and returned. Next, the supernatant water of the foaming scum concentrating tank 7 overflows upon returning to the tank and is returned to the raw water tank. In this case, since the supernatant water has a treatment equal to or less than that of the inflow sewage, it can be returned to the site.

FIG. 1 is a plan view of the foam scum concentrating tank 7, FIG.
Is a vertical sectional view of the same, and the operation of the foam scum concentrating tank 7 will be described below with reference to FIGS. A drive shaft 71 driven by a motor 70 is rotatably disposed at the center of the foamed scum concentrating tank 7 having a required area, and a scum draw plate 72, a tank are provided at the water surface position on the drive shaft 71. Sludge drawing plate 73 on the bottom
Are provided so that they can rotate together.

Further, a center well 74 is disposed in the center of the foam scum concentrating tank 7 so as to be submerged in water, and a scum inflow pipe 75 is provided therein, and a mud collecting pit 76 is provided in the center of the bottom of the tank. The sludge drawing pipe 77 discharges the sludge.

A supernatant water drainage trough 8 is arranged on the outer peripheral portion of the water surface position of the foam scum concentrating tank 7, and the treated supernatant water is drained through a supernatant water drainage pipe 79 connected thereto, and the inner peripheral wall from the center of the tank. The inner peripheral surface of the scum overflow prevention plate 81 in which the scum baffle wall 8 is arranged at the water surface position in the radial direction and the outer end of the scum baffle wall 8 is circularly arranged along the inner wall surface of the tank. Abut.

A water sprinkling pipe 9 is provided upstream of the scum baffle wall 8.
Are provided in the radial direction, and sprinkling water for defoaming is supplied to the sprinkler pipe 9. However, the scum attractor plate 72 is provided in the front direction of the sprinkler pipe so that the scum attractor plate 72 does not enter the position below the sprinkler pipe. A stop device 91 is provided.

Therefore, the inflow into the foam scum concentrating tank 7 contains a large amount of mixed liquid in addition to the foam scum. Therefore, the sludge part is directly moved to the sludge pit 76 under the center of the apparatus so that the sludge is not diffused by the center well 74. On the other hand, the foam scum has a small specific gravity and floats above the water surface, but the center well 7
Since 4 is submerged, it spreads over the entire water surface. This foamed scum is scraped by the scum scraping plate 72 of the center drive, but since the scum blocking wall 8 is provided in the radial direction of the pond,
Prevents foam scum from going around. The scum crawler plate temporarily stops its rotation by means such as a limit switch at the scum crawler plate stop device position. The foamed scum is raked at a high density between the scum draw plate and the scum baffle and stays there. A large number of sprinkling pipes for defoaming are installed above the retention position, and showering is performed during the rotation suspension time to sufficiently perform defoaming treatment.

After defoaming, the foamed scum is concentrated as ordinary sludge, collected in the lower part of the center of the tank by a sludge attracting plate, and transferred to a sludge treatment process through a sludge drawing pipe. On the other hand, the scum scraping plate is restarted by a timer after operating for a predetermined time to operate on the circular tank orbit, and the scraping / pausing cycle is repeated to efficiently collect the foamed scum at a predetermined position.

The concentration tank described below can provide the same function to the final settling basin. In this case, the concentration tank is abolished, and the precipitation tank 3A is circular, and its flow chart is shown in FIG.

In this embodiment, as shown in FIG. 4, the inflowing sewage is introduced from the raw water tank 1 to the settling tank 3A through the aeration tank 2 and the residue screen 6, and then the sludge collected in the settling tank 3A is concentrated into sludge. It is led to the storage tank 4 and dehydrated by the dehydrator 5.

Further, as in the first embodiment, the settling tank 3A is provided with a scum scraper and a sludge scraper that rotate in the tank as shown in FIGS. The scum baffle wall 8 and the sprinkler pipe 9 are provided on the water surface in the radial direction, and the same operation as that of the first embodiment is performed.

[0022]

According to the method for treating foam scum of the present invention, the scum blocking wall is provided on the water surface in the radial direction of the circular treatment tank equipped with the scum scraper, and the scum scooping plate serves to provide the foam scum. The scum scraper that blocks the rotation and moves in a circular motion is temporarily stopped, and the foamed scum is efficiently collected between the scum barrier wall and the scum scraper plate to perform defoaming treatment by sprinkling water. Therefore, the actinomycetes that are the causative organism of the foaming scum can be efficiently collected and discharged into the dehydrated cake, so the number of actinomycetes in the system can be reduced, and the appearance and the quality of treated water can be prevented from being deteriorated due to the foaming scum. There is.

[Brief description of drawings]

FIG. 1 is a flowchart showing an embodiment of a method for treating foam scum according to the present invention.

FIG. 2 is a vertical sectional view of a foam scum concentrating tank.

FIG. 3 is a plan view of the same.

FIG. 4 is a flow chart of a method of treating foam scum according to another embodiment.

[Explanation of symbols]

 1 Raw water tank 2 Aeration tank 3 Final settling tank 4 Sludge concentration storage tank 5 Dewatering machine 6 Silt screen 7 Concentration tank 72 Scum draw plate 73 Sludge draw plate 74 Center well 78 Clear water drainage trough 8 Scum barrier wall 81 Overfill Flow prevention plate 9 Sprinkling pipe

Claims (3)

[Claims] 1. A scum baffle wall is provided on the water surface in the radial direction of a circular processing tank equipped with a scum scraper to prevent the foam scum from being circulated by a scum scraper plate and to make a circular motion. A method for treating foam scum, which comprises periodically suspending the scum scraper, efficiently collecting the foam scum between the scum barrier wall and the scum draw plate, and performing defoaming treatment by sprinkling water. 2. The method for treating foam scum according to claim 1, wherein in the step of treating the sewage flowing into the sewage treatment plant using the concentrating tank and the final settling tank, the circular treating tank is a concentrating tank. 3. The method for treating foam scum according to claim 1, wherein in the step of treating the sewage flowing into the sewage treatment plant by using the precipitation tank, the circular treatment tank is a precipitation tank.