JP6300103B2 - Membrane separation activated sludge treatment equipment - Google Patents

Description

  The present invention relates to a membrane separation activated sludge treatment apparatus used for treatment of sewage and industrial waste water.

  Various types of activated sludge treatment devices are known, and one of them is to install a membrane separation device in the activated sludge treatment tank and separate the treated water with a membrane while performing activated sludge treatment. (See Patent Documents 1 to 3).

  In Patent Literature 1, as shown in FIG. 7, an aeration device 3 and a membrane separation device 4 are provided in an activated sludge treatment tank 12, and a water flow pump 20 is provided outside the activated sludge treatment tank 12 to activate the activated sludge treatment tank 12. A drawing pipe is connected to the bottom of the sludge treatment tank 12, and a water flow that flows along the membrane surface of the membrane separation device 4 is formed by the water pump 20, and a circulating water flow is formed in the activated sludge treatment tank 12. It eliminates the need for an air diffuser for cleaning, facilitates maintenance, greatly reduces power consumption, and reduces activated sludge treatment costs.

In Patent Document 2, as shown in FIG. 8, in an activated sludge treatment tank 12, a gas separation device 4, and an air diffuser 3 that combines oxygen supply to the activated sludge and cleaning of the membrane of the membrane separator 4. And a membrane separation activated sludge treatment apparatus B provided with a propeller-type underwater stirrer 21 with a turning mechanism. In this apparatus, a water flow is formed using mechanical force, and this is applied to the membrane surface of the membrane separation device 4, whereby the membrane surface is efficiently cleaned using fine bubbles, and oxygen is efficiently supplied. It saves power consumption.
In Patent Document 2, the membrane separation device 4 is composed of a plurality of membrane units, and a diffuser and an upward water flow outlet are provided below each of the membrane units, and a water flow pump is connected to the water flow outlet. There is also a description of an apparatus in which a water supply pipe for supplying water is provided with an automatic opening / closing valve for each membrane unit, and water is supplied by sequentially switching one or a plurality of water flow outlets. This apparatus makes it possible to reduce operating costs by intermittently cleaning the membrane surface.

  Further, Patent Document 3 discloses a membrane separation type oxidation ditch method using an endless water channel having a mechanical aeration device as an activated sludge treatment tank as shown in FIG. A wall 2 is provided to form an endless water channel 11, and an aeration stirrer 3 for forming a circulating water flow is provided in the endless water channel 11, and a filtration water tank having a sludge mixed liquid inlet and outlet 15 is provided with a space between the bottom of the oxidation ditch 1, an immersion type membrane separation device 4 in the filtration water tank 15, and a diffusion pipe (not shown) for membrane cleaning below the membrane separation device 4. And a membrane separation type oxidation ditch device A in which air is sent to the diffuser tube by the blower 13 to clean the membrane.

JP 2012-157849 A JP 2012-176396 A JP 2003-039087 A

A method of mechanically forming a water flow using a stirrer or a water flow pump as described in Patent Documents 1 and 2 is preferable in that oxygen is efficiently supplied to the membrane surface and at the same time the membrane surface is cleaned. Is the method.
However, stirring by a stirring device having a stirring blade cannot ensure a predetermined amount of washing water (flow velocity) inside the membrane separation device because the formed water flow diffuses.
In addition, the method using the water pump requires a pump that can supply a large flow rate. As a result, the power cost becomes high, and it is necessary to perform intermittent operation to suppress the power cost.

Moreover, the method of providing an automatic on-off valve for each membrane unit and selectively supplying a water flow to the membrane unit as described in Patent Document 2 requires a large-diameter main pump-class pump in consideration of realization. In addition, there is a problem in that frequent switching of minute units of large-diameter automatic open / close valves is required, and the processing power exceeds 0.4 kW / m ³ which is a guideline for introducing the membrane separation activated sludge method It becomes.
Furthermore, since the apparatus described in Patent Document 3 needs to diffuse air E for film cleaning from the air diffuser in order to clean the film, power consumption increases.
An object of this invention is to solve the said subject in the membrane separation activated sludge processing apparatus which forms a water flow mechanically using a stirring apparatus.

  As a result of studying to solve the above-mentioned problems, the present inventor uses a propeller-type underwater agitator in a membrane separation activated sludge treatment apparatus and provides a water flow guide for efficiently guiding the water flow to the membrane separation apparatus. The present invention has been completed by finding that the problems can be solved.

The present invention is a membrane separation activated sludge treatment apparatus as described below.
(1) A membrane separation activated sludge treatment apparatus having an endless water channel,
In the endless water channel, an aeration device, a propeller-type underwater agitator and a membrane separation device are provided in this order,
The propeller-type underwater stirrer is disposed to face the membrane separation device,
A membrane separation activated sludge treatment apparatus characterized in that at least a propeller portion of the propeller-type underwater stirrer and a space between the propeller portion and the membrane separation device are surrounded by a cylindrical water flow guide.
(2) The membrane separation activated sludge treatment apparatus according to (1), wherein the water flow guide has a taper shape in a downstream portion from a portion surrounding the propeller toward a peripheral portion of the membrane separation device.
(3) The membrane separation activated sludge treatment apparatus as described in (1) or (2) above, wherein a space upstream of the propeller portion is also surrounded by the water flow guide.
(4) The membrane separation activity according to any one of (1) to (3) above, wherein the water flow guide has a tapered shape in which a portion on the upstream side from a portion surrounding the propeller extends toward the upstream side. Sludge treatment equipment.
(5) On the downstream side of the propeller of the propeller type submerged stirrer, an auxiliary propeller having a diameter smaller than the propeller diameter of the propeller is provided on the rotation shaft of the propeller, and a cylindrical auxiliary water flow guide surrounding the auxiliary propeller The membrane separation activated sludge treatment apparatus according to any one of the above (1) to (4), wherein:
(6) The membrane-separated activated sludge treatment apparatus according to (5), wherein the auxiliary water flow guide has a tapered shape spreading toward the downstream side.

  By using the membrane separation activated sludge treatment device of the present invention, it is possible to perform membrane cleaning only with the water flow formed by equipment necessary for water flow generation, and additionally install a diffuser for membrane surface cleaning, etc. There is no need to do. Further, since there is no need to perform intermittent operation, operations such as valve switching are not required. As a result, the power consumption can be greatly reduced, and the activated sludge treatment cost can be reduced.

It is a figure which shows schematic structure of embodiment of the apparatus of this invention. It is a figure which shows schematic structure of other embodiment of the apparatus of this invention. It is the elements on larger scale of FIG. It is a figure which shows the example of the water flow guide in the apparatus of this invention. It is a figure which shows the example of the water flow guide in the apparatus of this invention. It is a figure which shows schematic structure of embodiment of the apparatus of this invention which has arrange | positioned the water flow guide shown to FIG. 4-2 (c). It is a figure which shows schematic structure of the other example of this invention. It is a figure which shows schematic structure of the conventional apparatus. It is a figure which shows schematic structure of the conventional apparatus. It is a figure which shows schematic structure of the conventional apparatus.

Hereinafter, the membrane separation activated sludge treatment apparatus of the present invention will be described in detail based on FIG. 1 showing one of the embodiments of the present invention.
The membrane-separated activated sludge treatment apparatus A of the present invention has, as a basic configuration, an oval or circular activated sludge treatment tank 1 constituting an endless water channel 11, and an air diffuser 3 provided in the activated sludge treatment tank 1. , A membrane separator 4, a propeller-type underwater stirrer 5 as a water flow generator, and a water flow guide 6.
Hereinafter, each component will be described.

(Activated sludge treatment tank)
An oval or circular endless water channel 11 having a water depth of 1 to 3 m is formed in the activated sludge treatment tank 1 by a partition wall 2. Activated sludge is accommodated in the activated sludge treatment tank 1, and the water to be treated in the activated sludge treatment tank 1 is circulated in the endless water channel 11 by being given a thrust in the horizontal direction by the rotation of the propeller underwater agitator 5. The inflow water supplied into the activated sludge treatment tank 1 circulates in the endless water channel 11 through the air diffuser 3, the propeller-type underwater stirrer 5, the water flow guide 6 and the membrane separator 4 to perform membrane separation. The treated water separated by the separation membrane of the device 4 is discharged by the pump 10.

(Air diffuser)
The air diffuser 3 jets bubbles to supply oxygen to the activated sludge. The air diffuser 3 may basically be the same as a normal air diffuser, and is provided with a large number of air outlets in a manifold having a shape such as a box or a tube. The air outlet may be a fine hole, and a nozzle may be attached. The pore diameter is determined so as to form fine bubbles in order to increase the oxygen dissolution efficiency. The bubble diameter is preferably about 0.5 to 4 mm, particularly about 0.5 to 1.0 mm. If the bubble diameter is too large, sufficient oxygen dissolution efficiency cannot be obtained, and if the bubble diameter is too small, the pressure loss of the air diffuser increases and it becomes difficult to perform stable operation. A bubble diameter of 0.5 to 1.0 mm is preferable because an oxygen dissolution efficiency of 30 to 40% can be obtained. With this bubble diameter, the membrane cleaning effect due to the bubbles cannot be obtained sufficiently, but there is no particular problem in the operation of the membrane because cleaning with a water flow described later is also used.

With regard to the amount of air diffused, in the conventional method in which coarse bubbles and fine bubbles are diffused, the air volume of the coarse bubbles necessary for cleaning the membrane is determined from the projected area of the membrane, and the oxygen calculated from the oxygen dissolution efficiency at that time The air volume of the fine bubbles is determined from the difference between the supply amount and the required oxygen amount of the activated sludge.
On the other hand, in the present invention, in order to ensure the shearing force required for membrane cleaning using a propeller-type underwater stirrer described later, it is possible to perform aeration using only fine bubbles, and the air volume is necessary for activated sludge. Determined from the amount of oxygen.

(Membrane separator)
The membrane separation device 4 separates activated sludge and treated water, and a microfiltration membrane or an ultrafiltration membrane can be applied for the pore size of the membrane. The arrangement of the membranes is usually parallel to each other so as not to disturb the water flow and bubble flow.
When the membrane separation device 4 is a hollow fiber type membrane, the pore size of the membrane is preferably in the range of about 0.01 to 1 μm, and particularly in the range of 0.02 to 0.5 μm It is often used to obtain water quality and an economical permeate flux.

Although the cleaning effect can be obtained by setting the flow rate of the water flow at the membrane surface portion to 0.1 m / s or more, it is preferably 0.2 to 0.5 m / s.
The angle at which the water flow is applied to the membrane surface is preferably as shallow as possible, and about 0 to 45 degrees is appropriate. In the membrane arranged vertically in the activated sludge treatment tank, a swirl flow is generated in the entire tank, whereby a water flow parallel to the membrane surface can be efficiently generated.

(Propeller type underwater stirrer)
The propeller-type underwater stirrer 5 forms a circulating water flow in the activated sludge treatment tank 1 by mechanical force.
The propeller-type underwater stirrer 5 is arranged so that the stirring blade (hereinafter also referred to as “propeller”) faces the membrane separation device 4 and the direction of water flow faces the membrane separation device 4.

(Water flow guide)
The water flow guide 6 has a cylindrical shape, and as shown in FIG. 3, the upstream side portion 61 of the water flow guide 6 is in contact with the wall surface of the activated sludge treatment tank, and the water to be treated is mixed with the propeller underwater stirrer 5. Lead to. Further, the downstream side portion 62 of the water flow guide 6 guides the water to be treated to which the thrust is applied by the propeller type underwater agitator 5 to the membrane separation device 4. The downstream edge of the downstream portion 62 of the water flow guide 6 is attached to the upstream edge of the membrane separation device 4.

Examples of water flow guides are shown in FIGS. 4-1 and 4-2.
The shape of the water flow guide 6 can be a cylindrical shape, a rectangular tube shape, a tapered cylindrical shape, or a tapered rectangular tube shape, but the propeller portion has a cylindrical shape.
The water flow guide 6 has a shape in which the swirling flow is entirely supplied to the propeller portion from the portion surrounding the propeller of the propeller type underwater agitator 5, and the lower portion from the portion surrounding the propeller is membrane-separated. It has a shape connected to the peripheral edge of the device 4.
It should be noted that there should be as little gap as possible between the upstream end of the water flow guide 6 and the wall surface of the activated sludge treatment tank forming the endless water channel. If there is a gap, the water to be treated will stay in this part and the quality of the treated water will deteriorate.

In FIG. 4A, the water flow guide 6 has a straight cylindrical shape, and the propeller 5 is disposed at the center of the water flow guide 6.
In FIG. 4B, the upstream water flow guide has a tapered shape that narrows toward the downstream side, and the downstream water flow guide has a straight cylindrical shape. By setting it as such a shape, treated water can be guide | induced to the membrane separator 4. FIG.
In FIG. 4-2 (c), the upstream water flow guide has a tapered shape that widens toward the upstream side, and the downstream water flow guide has a tapered shape that widens toward the downstream side.
In FIG. 4D, the upstream water flow guide has a tapered shape that widens toward the upstream side, and the downstream water flow guide has a tapered shape that narrows toward the downstream side.

The usage pattern of what is shown in FIG. 4-2 (c) is shown in FIG.
Fig.5 (a) is a longitudinal cross-sectional view of a membrane separation activated sludge processing apparatus, FIG.5 (b) is XX sectional drawing in Fig.5 (a). By providing the water flow guide having the structure shown in FIG. 4-2 (c) as shown in FIG. 5 (a), this water flow guide is indicated by E in FIG. 5 (b) on the upstream side of the membrane separator. A structure in which such a flow of water to be treated does not flow in other than the propeller portion is formed, and a shaded portion in FIG. For this reason, all of the water flow passes through the propeller and the membrane separation device 4. This embodiment is preferable because a large amount of treated water can be led to the membrane separation device 4.

Various shapes can be adopted as the shape of the water flow guide 6 depending on the size of the propeller and the size of the membrane separation device 4.
As shown in FIG. 5A, the propeller upstream portion preferably has a structure in which the water flow does not pass through a region other than the propeller, for example, the propeller upstream portion has a taper that expands toward the upstream side.
In this case, when the size of the propeller is larger than the size of the inflow portion of the membrane separation device, the propeller downstream portion has a taper that decreases toward the downstream side as shown in FIG. .
In addition, if the size of the propeller is the same as that of the inflow portion of the membrane separation device, the propeller downstream portion has a straight cylindrical shape as shown in FIGS. 4-1 (a) and (b).
Further, when the size of the propeller is smaller than the inflow portion of the membrane separation device, the propeller downstream portion has a taper that expands toward the downstream side as shown in FIG.

  By providing such a water flow guide 6, the water flow of the water to be treated driven by the propeller-type underwater stirrer 5 is directed toward the membrane separation device 4 efficiently without stagnation. Furthermore, the water flow guided to the membrane separation device 4 has a uniform velocity distribution with respect to the flow path cross section.

(Auxiliary water flow guide and auxiliary propeller)
In the case shown in FIG. 3, the water flow is uniformly supplied to the membrane surface. However, in order to more effectively and uniformly supply the water flow guided to the membrane separation device 4 to the membrane surface, as shown in FIG. It is preferable to provide the auxiliary propeller 7 and the auxiliary water flow guide 8 having a taper shape spreading toward the downstream side surrounding the auxiliary propeller 7 inside the water flow guide 6.
When the propeller of the propeller-type underwater agitator 5 is smaller than the membrane portion and has a shape in which the downstream side portion of the propeller expands, the propeller has directivity although it is imperfect, and therefore it cannot effectively supply water flow to the most widened portion. The auxiliary water flow guide 8 supplies the fluid flowing straight into the membrane portion to the most widened portion, and the water flow is supplied to the membrane surface more effectively and uniformly by supplying the water flow through the auxiliary propeller 7 at the central portion that is insufficient as the water flow. Can be supplied.

FIG. 2 shows another embodiment of the membrane separation activated sludge treatment apparatus of the present invention.
The pressure loss due to the separation membrane increases / decreases depending on the length of the separation membrane in the direction of the water to be treated (the amount of separation membrane), so the membrane separation device is divided by dividing the membrane separation device according to the amount of separation membrane required The cleaning effect can be enhanced by providing the water flow guide and the propeller type underwater agitator in each of the stages.
FIG. 2 shows the membrane separation activated sludge treatment apparatus shown in FIG. 1, wherein the separation membrane is divided and the membrane separation apparatus 4 is divided into two stages of the membrane separation apparatus 4-1 and the membrane separation apparatus 4-2. The membrane separators 4-1 and 4-2 are provided with propeller-type underwater stirrers 5-1 and 5-2 and water flow guides 6-1 and 6-2.
Although what was shown in FIG. 2 provided the membrane separation apparatus in 2 steps | paragraphs, you may provide in 3 or more multistage.

  The present invention will be described below in more detail based on examples, but the technical scope of the present invention is not limited to the following examples.

[Example 1]
The apparatus shown in FIG. 1 was used.
As the activated sludge treatment tank having an endless water channel, a tank having a water depth of 2 m and a circulation distance of 6.6 m was used.
The air diffuser position of the air diffuser 3 was set at a water depth of 1.7 m. The amount of air diffused was set to 113 m ³ / h, that is, 38 vvh as the aeration rate for the water to be treated.
As the membrane separation device 4, a MF membrane module having a box size of 0.8 m (L) × 1.6 m (W) × 2.0 m (H) and a pore diameter of 0.2 μm was adopted. The membrane area was 108 m ² .
The treated water outlet is structured to be taken out of the system through a center pipe installed at the center of the membrane module.
The propeller-type underwater stirrer 5 was set so that the rotation diameter was 1.5 m and the flow rate at the propeller portion was 1.0 to 1.2 m / s.

Water to be treated was one having a BOD concentration of 80 mg / L, and the amount of water to be treated was set to 72 m ³ / d. The excess sludge was appropriately discharged so that the MLSS concentration was maintained at about 6,000 to 10,000 mg / L.
As a result, the BOD of the treated water could be 1.5 mg / L or less, and a favorable biological treatment could be performed. The DO in the reaction tank could always be kept at 1.5 mg / L or more.
The required power for aeration per unit treated water amount was a blower power of 0.39 kWh / m ³ and a stirring power of 0.36 kWh / m ³ for a total of 0.75 kWh / m ³ .

[Comparative Example 1]
The apparatus which removed the water flow guide from the apparatus shown in FIG. 1 was used.
In this case, by increasing the stirring power to 0.48 kWh / m ³ , the BOD of the treated water could be 1.5 mg / L or less, and good biological treatment could be performed. The DO in the reaction tank could always be kept at 1.0 mg / L or more.
The power required for aeration and membrane cleaning per unit treated water amount in this case was a blower power of 0.39 kWh / m ³ and a stirring power of 0.48 kWh / m ³ for a total of 0.87 kWh / m ³ .

As described above, in the examples, by providing the water flow guide, it was possible to obtain treated water with low power and good water quality.
On the other hand, the amount of electric power in the comparative example increased compared to the example, and the water quality also deteriorated.

  Since the membrane separation activated sludge treatment apparatus of the present invention can reduce the electric power used for activated sludge treatment, it can be widely used for membrane separation activated sludge treatment equipment.

DESCRIPTION OF SYMBOLS 1 Activated sludge processing tank 2 Partition wall 3 Air diffuser 4, 4-1, 4-2 Membrane separator 5, 5-1, 5-2 Propeller type underwater agitator 6, 6-1, 6-2 Water flow guide 7 Auxiliary Propeller 8 Auxiliary water flow guide 10 Pump 11 Endless water channel 12 Activated sludge treatment tank 13 Blower 14 Mud mixed liquid outlet 15 Filtration water tank 20 Water flow pump 21 Propeller type submerged stirrer with swivel mechanism 61 Upstream side portion 62 of water flow guide Downstream side A Membrane separation activated sludge treatment device B Membrane separation activated sludge treatment device D Non-water-flowing region E Structure where swirl flow does not flow to other than propeller

Claims (6)

A membrane separation activated sludge treatment apparatus having an endless water channel,
In the endless water channel, an aeration device, a propeller-type underwater agitator and a membrane separation device are provided in this order,
The propeller-type underwater stirrer is disposed to face the membrane separation device,
A membrane separation activated sludge treatment apparatus characterized in that at least a propeller portion of the propeller-type underwater stirrer and a space between the propeller portion and the membrane separation device are surrounded by a cylindrical water flow guide.   2. The membrane separation activated sludge treatment apparatus according to claim 1, wherein at least the water flow guide has a taper shape toward a peripheral portion of the membrane separation device at a downstream portion from a portion surrounding the propeller.   The membrane separation activated sludge treatment apparatus according to claim 1 or 2, wherein a space in an upstream portion of the propeller portion is also surrounded by the water flow guide.   The membrane separation activated sludge treatment apparatus according to any one of claims 1 to 3, wherein the water flow guide has a tapered shape in which a portion on the upstream side from a portion surrounding the propeller extends toward the upstream side. On the downstream side of the propeller of the propeller-type underwater stirrer, an auxiliary propeller having a smaller diameter than the propeller diameter of the propeller is provided on the rotation shaft of the propeller, and
The membrane-separated activated sludge treatment apparatus according to any one of claims 1 to 4, further comprising a cylindrical auxiliary water flow guide surrounding the auxiliary propeller.   The membrane separation activated sludge treatment apparatus according to claim 5, wherein the auxiliary water flow guide has a tapered shape spreading toward the downstream side.

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