JPH08257585A - Method and apparatus for activated sludge treatment of waste water - Google Patents

Abstract

PURPOSE: To efficiently subject biologically treated waste water to solid-liquid separation in a final sedimentation basin. CONSTITUTION: This apparatus is provided with a reaction tank 1 biologically treating waste water and a horizontal flow type final sedimentation basin 2 introducing biologically treated waste water from one end part thereof and leading out the same from the other end part thereof. The final sedimentation basin 2 is partitioned at the intermediate part thereof by a partition wall 3 of which the lower end reaches a deep intermediate part and a floating filter material packed part 4 is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an activated sludge treatment method and an activated sludge treatment device for treating wastewater containing solids such as sewage, and particularly for solid-liquid separation of biologically treated wastewater. Regarding improved final settling basin.

[0002]

2. Description of the Related Art Conventionally, in a standard activated sludge method for treating wastewater containing organic matter such as sewage, as shown in the flow chart of FIG. Is solid-liquid separated by. Next, the treated water is sent to a reaction tank for biological treatment, and then sent to a precipitation treatment device called a final sedimentation tank for final solid-liquid separation. In this case, the sludge extracted from the final settling tank is returned to the reaction tank as return sludge. However, the activated sludge sent from the reaction tank to the final settling tank is
Its properties are unstable, such as the flocs becoming finer, and the sedimentation in the final sedimentation tank often deteriorates. Therefore, SS of treated water discharged from the final settling tank
The concentration may be high and may adversely affect the water quality in public water areas.

In addition, a treatment method called a modified activated sludge circulation method in which nitrification and denitrification are performed in a reaction tank for treating activated sludge has been put into practical use. In this method, as shown in the flow chart of FIG. 4, a denitrification tank and a nitrification tank are first provided after the sedimentation tank, biological treatment is performed while circulating the nitrification solution, and then sent to the precipitation treatment device. The final solid-liquid separation is performed. Also in this method, nitrification and denitrification generally cause deterioration of the sedimentation of the activated sludge, so that the SS concentration of treated water becomes higher than that of the standard activated sludge method.

Further, recently, in order to accelerate the nitrogen removal rate in place of this activated sludge circulation modified method, a carrier-introduced activated sludge circulation modified method is used as a method of increasing the sludge concentration in the reaction tank by introducing a carrier. It is being put to practical use. However, in this treatment method, in addition to the obstacles for solid-liquid separation in the final sedimentation tank due to the above-mentioned nitrification and denitrification treatment, the sludge concentration is high, so the SS concentration of the treated water in the final sedimentation tank should be low. There is a problem that it becomes difficult. There is also a problem that the sludge peeled off from the carrier is fine and not flocculated, and thus is extremely unlikely to settle.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an activated sludge treatment method and an active sludge treatment method for efficiently performing solid-liquid separation of biologically treated wastewater in a final settling tank. A sludge treatment device is provided.

[0006]

The above problems can be solved by the following method for treating activated sludge of wastewater. After biological treatment of the wastewater, the wastewater is introduced into the cross-flow type final settling tank to allow the solids to settle naturally in the convection settling section, and a partition wall is provided in the latter stage of the final settling tank to fill the floating filter media In the section, the method for treating activated sludge of wastewater, comprising the step of passing wastewater upward to capture and remove fine solids in the floating filter medium.

The above problem can also be solved by the following activated sludge treatment device for wastewater. A reaction tank for biological treatment of wastewater, and a lateral flow type final settling tank in which biologically treated wastewater is introduced from one side and discharged from the other, the upper end of which is higher than the water surface and the lower end of which is in the middle of the water depth. An activated sludge treatment device for wastewater, comprising: a transverse flow type final settling tank having a filter material filling section filled with a floating filter material in a stage subsequent to the final settling tank partitioned by partition walls.

[0008]

In general, as shown in FIG. 5, inside the final settling basin 2, the introduced wastewater immediately flows downward, becomes a lateral flow below the pond, and turns upward below the trough 02 at the latter stage. It is known that a circulating water stream 03 that returns to the introduction section is generated in the preceding stage of the final settling tank 2. It is also known that most of the settled sludge 04 is settled up to the rear end of the hopper 05, and that it is very small from the central part to the downstream part of the pond.

Therefore, in the method for treating activated sludge of wastewater according to the present invention, in the filter medium filling section partitioned by the partition wall, the wastewater is passed upward to capture and remove fine solids. The SS can be removed without disturbing the water flow in the final settling tank and the sedimentation behavior of the solid matter, and the efficiency can be further improved because the floating filter medium is provided in the filter medium filling section. Further, in the activated sludge treatment device of the wastewater of the present invention, in the middle of the final settling basin, the upper end is higher than the water surface and the lower end is in the middle of the water depth. In addition, since the filter material filling section is used, SS can be efficiently captured and removed without disturbing the precipitation flow behavior of the conventional final settling tank and solid matter.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. (Embodiment 1) First, FIG. 1 shows an embodiment of the present invention, in which a reaction tank 1 for biologically treating wastewater containing solids is provided, and the wastewater biologically treated in this reaction tank 1 is a cross-flow type final It is introduced from one of the settling basins 2 and derived from the other. As in the conventional case, the final settling tank 2 is provided with a convection settling section 20 having a hopper section 21 for settling relatively coarse solid matter in the first stage, and a tank inclined gently upward in the downstream direction. A bottom 22 is formed continuously, and a scraping chain 2 for scraping the settled sludge in the direction of the hopper 21 on the tank bottom 22.
3 is provided.

Further, in the middle of the flow direction of the final settling tank, the upper end is higher than the water surface and the lower end is in the middle of the water depth. The filter medium filling unit 4 is configured. A drainage trough 41 is provided on the upper portion of the filter medium filling unit 4, and a plurality of aeration pipes 42 for supplying air are provided on the lower portion thereof. In this way, the final settling tank of the present invention is partitioned by the partition wall 3 and the convection settling section 2
It is divided into 0 and the filter medium filling section 4.

The position and the depth of the partition wall 3 for partitioning the final settling tank are set so as not to obstruct the circulating water flow returning to the introduction part in the front stage of the final settling tank and the upward flowing water flow in the rear stage. However, it may be provided at a position 1/4 to 3/4 of the length of the pond from the wastewater introduction part. The filter medium filling portion 4 thus formed is filled with a myriad of floating fillers (not shown) to a required depth. This filler can be appropriately selected from materials such as foamed plastic having a specific gravity of less than 1.0, sponge, or fibrous material, and the shape thereof is a granular or tubular shape of about 3 to 100 mm,
Those with a large contact area with wastewater, such as hollow holes, spherical shapes, and spiral shapes, are used.

In order to remove the organic components and the like in the wastewater by the activated sludge treatment apparatus of the wastewater of the present invention thus constructed,
First, the wastewater is biologically treated in the reaction tank 1, and then introduced into the lateral flow type final settling tank 2. In this case, the SS concentration of the wastewater at the stage of being introduced into the lateral flow type final settling tank 2 is 1000
Concentration as low as mg / l may be used, but 10,000 mg / l
Higher concentrations can be applied. Then, the introduced wastewater is allowed to spontaneously settle a relatively coarse solid content in the convection settling section 20 of the lateral flow type final settling tank 2 and then the hopper section 21.
And the SS concentration is 5 to 30 mg /
The waste water of about 1 gently flows in the downstream direction along the slanted tank bottom 22 and passes upward through the filter medium filling section 4 filled with the floating filter medium at the latter stage, whereby fine solids are contained in the floating filter medium. After being captured and removed, the purified wastewater is discharged from the trough 41 as treated water.

As described above, in the activated sludge treatment method of this embodiment, in the filter medium filling section 4 partitioned by the partition wall 3, the wastewater is passed upward to capture and remove fine solids. However, the SS can be removed without disturbing the conventional water flow in the final settling basin and the sedimentation behavior of the solid matter, and the efficiency can be further improved because the filter medium filling section 4 is provided with the floating filter medium. Become. Further, in the activated sludge treatment device of this embodiment,
In the middle of the final settling basin, the upper end is higher than the water surface and the lower end is in the middle of the water depth. The SS can be efficiently captured and removed without disturbing the water flow and the precipitation behavior of the solid matter.

When the solid content adheres to the floating filter medium in the filter medium filling section 4 and its function deteriorates, air is supplied from a plurality of aeration pipes 42 provided in the lower part of the filter medium filling section 4 to suspend the floating filter medium. It may be washed by rocking. In this case, some of the solid matter attached to the floating filter medium settles to the bottom of the tank, but most of it rises with the wastewater, so the drainage trough 4
1 may be discharged, or may be discharged from a separately provided washing drainage pipe (not shown). Further, if necessary, the waste water for cleaning is returned to a stage before the reaction tank, for example, the first settling tank. In this way, it is not necessary to stop the supply of waste water to the filter medium filling section 4 even when washing the floating filter medium.

Further, the reaction tank 1 of the present invention is not limited to the one for carrying out a normal biological treatment, but is also applied to a reaction tank used in an activated sludge circulation modified method or a carrier charging activated sludge circulation modified method. obtain. Further, in the present invention, the water area load of the final settling tank is the same as that of the normal final settling tank, which is 20
It can be taken from the value of ~30m ³ / m ² / day to a maximum of 100m ³ / m ² / day.

(Embodiment 2) In the activated sludge treatment method and apparatus for wastewater of the present invention, aerobic bacteria are adhered to the floating filter medium in the filter medium filling section 4, and the aeration pipe 42 is used to filter the medium. By constantly supplying air to the extent that solid matter attached to the floating filter medium is not separated, and supplying oxygen to the floating filter medium, the filter medium filling section 4 is provided with a function as an aerobic biological filter bed, and SS Can be embodied so as to remove BOD simultaneously with the removal of BOD.

Further, in this case, as shown in FIG. 2, a part of the treated water may be sucked and taken out by a pump 51 through a large number of membrane modules 5 arranged above the filter medium filling section 4. You can For this membrane module 5, a membrane module such as a hollow microfiltration membrane may be used. The membrane-permeating treated water thus taken out has a higher level of water quality than the treated water obtained by sand filtration or biological membrane filtration. The membrane permeation-treated water is preferably sucked continuously, but it may be sucked intermittently. Further, the membrane permeation flow rate is set to be equal to or less than the minimum introduction amount when the introduction amount of water in the final settling tank fluctuates. By doing so, it is possible to coexist the treated water that is not permeated with the membrane and the fluctuation of the water level in the sedimentation basin even if the amount of introduction is changed.

(Example 3) Further, in the method for treating activated sludge of wastewater and the apparatus for treating activated sludge of the present invention, the reaction tank is used as a reaction tank for nitrification reaction, and denitrifying bacteria are added to the floating filter medium in the filter medium filling section 4. Is attached and the function as a denitrification tank is imparted to the filter medium filling unit 4 without supplying air from the aeration pipe 42 to the filter medium filling unit 4 except when cleaning the filter medium.
It can be embodied so that denitrification is carried out simultaneously with the removal of S.

(Embodiment 4) Furthermore, the activated sludge treatment device for wastewater of the present invention can be easily embodied by applying it to an activated sludge treatment device equipped with an existing ordinary reaction tank and final settling tank. it can. That is, it is possible to form the filter medium filling section 4 of the present invention by providing the partition wall 3 in the subsequent stage of the existing final settling tank, and even in this case, the water flow and the solid settling in the conventional final settling tank are settled. The SS can be removed without disturbing the behavior, and the efficiency can be further improved by the floating filter medium in the filter medium filling section 4.

[0021]

Since the present invention is constructed as described above, it has the following excellent effects. (1) The SS treatment of biologically treated wastewater can be effectively performed without impairing the original water flow and the behavior of the sedimentation action of the lateral flow type final sedimentation basin. Further, according to the embodiment, it is possible to perform denitrification or BOD removal together. (2) Therefore, since a new treatment bed such as a sand filtration bed or a biofilm filtration bed is not required, treatment space, construction cost or operating cost can be saved. (3) It is not necessary to stop the operation of the settling tank when washing the floating filter medium in the filter medium filling section, and the introduced water to be treated is used as washing water for washing, so that the treatment efficiency is good. (4) Since the filter medium filling portion is formed, the water area load can be increased, and thus the processing space can be significantly reduced. (5) Since the present invention can be easily applied only by adding the filter medium filling section to the existing cross-flow type final settling tank, its application range is extremely wide. Therefore, the present invention has an extremely great industrial value as an activated sludge treatment method and an activated sludge treatment apparatus for wastewater which solves the conventional problems.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional conceptual view showing a portion of another embodiment.

FIG. 3 is a diagram showing a flow of a standard activated sludge method.

FIG. 4 is a diagram showing a flow of a modified activated sludge circulation method.

FIG. 5 is a diagram showing the water flow and the sludge of the final settling tank.

[Explanation of symbols]

 1 Reactor 2 Final sedimentation tank 3 Partition wall 4 Filter medium filling section

Claims (2)

[Claims] 1. After the wastewater is biologically treated, it is introduced into a cross-flow type final settling tank to allow the solids to naturally settle in the convection settling section, and a partition wall is provided in the latter stage of the final settling tank to set a floating filter medium. A method for treating activated sludge of wastewater, characterized in that in the filled filter medium filling portion, wastewater is passed upward to capture and remove fine solids from the floating filter medium. 2. A reaction tank for biologically treating wastewater, and a cross-flow type final settling basin in which biologically treated wastewater is introduced from one side and discharged from the other, the upper end being higher than the water surface and the lower end in the middle of the final settling basin. Is equipped with a cross-flow type final settling basin in which the latter stage of the final settling basin, which is partitioned by a partition wall extending to the middle of the water depth, is a filter medium filling section filled with a floating filter medium. apparatus.