JPH0487695A - Organic waste water treating device - Google Patents

Abstract

PURPOSE:To enhance the oxygen dissolution efficiency of an aerobic bioreaction chamber by using a spiral type membrane module wound with a separating membrane via a spacer of a corrugated board shape on the outer periphery of a water collecting pipe as the membrane module of a membrane separator. CONSTITUTION:Raw water is introduced from a piping 11 into the aerobic biochemical reaction chamber 1 and is subjected to a aerobic biochemical reaction treatment. The treated liquid is introduced through an introducing piping 12 into the membrane separator 2 and air is supplied to this liquid from a supplying piping 15 to form the air-liquid mixture which is introduced into the membrane separator 2. While the permeated water of the membrane separator 2 is taken out as treated water, the concd. water is returned to the aerobic biochemical reaction chamber 1. The air in the bubble-mixed liquid flowing into the membrane separator 2 dissolves sufficiently into the liquid during flows together with the liquid in the membrane module 2B. The liquid into which the air is sufficiently dissolved is returned to the aerobic biochemical reaction chamber 1 after the passage through the membrane module 2B and is thereby extremely efficiently biologically treated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an organic wastewater treatment device, and in particular, an organic wastewater treatment device that performs continuous treatment by solid-liquid separation of an aerobic biological reaction treated liquid using a membrane module. The present invention relates to an organic wastewater treatment device that maintains a high membrane permeation rate (flux) without increasing energy in membrane separation and improves the oxygen dissolution efficiency of an aerobic biological reaction tank.

[Prior Art] Conventionally, as a method for continuous aerobic biological reaction treatment of organic wastewater, a method of solid-liquid separation of an aerobic biological reaction treated liquid using a membrane separator is known. This method is industrially advantageous because it is not affected by changes in the biota such as bulking and can provide treated water of good quality that does not contain suspended solids.

In this method, for example, as shown in FIG. In this method, the permeated water is introduced into the membrane and buried in the membrane iIA, and the permeated water is discharged from the pipe 13 as treated water, while the concentrated water is circulated through the pipe 14 to the biological reaction tank 1. In this method, the membrane module 2A of the membrane separation device 2 has a large raw water flow path that is less likely to be clogged with SS in order to separate and process the aerobic biological reaction treated water of biological suspension containing a large amount of SS. Membrane modules such as plate-and-frame membrane modules and tubular membrane modules are used. By the way, please use a net-like spacer on the outer periphery of the water collection pipe. A conventional spiral membrane module formed by winding 18 membranes cannot be used due to clogging.

By the way, in a membrane separation apparatus equipped with a membrane module having a large log flow path, such as a flat membrane type membrane module, in order to maintain a high flux, it is necessary to increase the flow rate of raw water on the separation membrane surface. Increasing the flow rate of raw water is also effective for suppressing the formation of a gel layer on the surface of the separation membrane. For example, a plain coat type membrane module or a tubular type membrane module generally requires a high flow rate of about 2 to 3 m/s.

For this reason, the method using a membrane separation device has the disadvantage that it requires a large amount of energy compared to the case where the aerobic biological reaction treated liquid is solid-liquid separated in a sedimentation tank such as a car.

Conventionally, in such a method, for the purpose of effective use and recovery of energy, an air supply pipe 15 is connected to the introduction pipe 12 for the aerobic biological reaction treated liquid to the membrane separation device 2, as shown in FIG. 5(b). Alternatively, as shown in FIG. 5(c), a reduced pressure generating suction device (ejector) is installed in the piping 14 that circulates the concentrated water of the membrane separation device 2 to the aerobic biological reaction tank 1.
16 has been proposed.

[Problems to be Solved by the Invention] In the method shown in FIG. Although the effect of suppressing the formation of a gel layer on the surface of the membrane 2A can be expected to some extent, in the case of a plain clothes type or tube type membrane module, the dissolution efficiency of the supplied air into the liquid is poor. Another drawback was that the membrane module and piping vibrated because a large amount of gas was supplied into the raw water at a high flow rate.

On the other hand, in the method shown in FIG. 5(c), although the air supplied from the esector 16 can be effectively used in the aerobic biological reaction tank, air bubbles do not flow into the membrane separation device 2, and the There is a problem in that the formation of a gel layer on the 2A surface cannot be suppressed.

The present invention solves the above conventional problems and provides an organic wastewater treatment device that maintains a high flux and improves the oxygen dissolution efficiency of an aerobic biological reactor without increasing energy in membrane separation. The purpose is to

[Means for Solving the Problems] The organic wastewater treatment device of the present invention includes an aerobic biological reaction tank that performs aerobic biological reaction treatment on organic wastewater, and a membrane fraction III treatment of the treated liquid in the aerobic biological reaction tank. Equipped with a membrane separation device that
In an organic wastewater treatment device in which concentrated water of the membrane separation device is returned to the aerobic biological reaction tank, an air supply means for supplying air to the treated liquid of the aerobic biological reaction tank introduced into the membrane separation device is provided. In addition, as a membrane module of the membrane separator, a corrugated plate-shaped spacer is provided on the outer periphery of the water collection pipe.
The present invention is characterized by the use of a spiral membrane module formed by winding m membranes.

[Operation] In the organic wastewater treatment device of the present invention, air is supplied to the aerobic biological reaction treated liquid introduced into the membrane separation device, and the gas-liquid mixture of the aerobic biological reaction treated liquid and air is membrane separated. Introduced into the membrane module of the device.

This membrane module is a spiral type membrane module in which a separation membrane is wound around the outer periphery of a water collection pipe through a corrugated spacer. Air contained in the liquid is efficiently dissolved into the liquid. Air dissolved in water hardly escapes to the permeate side and is effectively used for aerobic biological reactions.

That is, if a spiral membrane module (corrugated type spiral membrane module) having a corrugated spacer is used as a module for membrane-separating biological treatment liquid, the air (gas) supplied into the biological treatment liquid can be efficiently Dissolve in the liquid. Since the dissolution of air for the aerobic biological reaction treatment is performed simultaneously with the solid-liquid fraction m treatment by membrane separation, the energy required for dissolving the air for the aerobic biological reaction is significantly reduced.

Moreover, in the corrugated spiral membrane module used in the present invention, strong turbulence occurs when the raw water passes through, which prevents clogging caused by SS and also suppresses the formation of a gel layer on the membrane surface. There is a lot of flux even in the flow velocity range. In addition, in the present invention, the air in the gas-liquid mixture further strengthens this gel layer formation suppressing effect and maintains the flux at an extremely high level.

Note that a corrugated type spiral membrane module is known from Japanese Patent Application No. 62-205809.

[Example] The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a system diagram of an organic wastewater treatment apparatus according to an embodiment of the present invention, and FIG. 7 is an assembled perspective view of a corrugated type membrane module. As shown in FIG. 7, the device of this embodiment uses a spiral type membrane module in which a W1 membrane 23 is wound around the outer periphery of a water collection pipe 21 via a corrugated spacer 22 as a membrane module of the membrane separation device 2. I am using it. The rest of the flow path configuration itself of the device shown in FIG. S1 is the same as that of the conventional example shown in FIG. 5(b), and the same reference numerals indicate the same parts.

In the apparatus shown in FIG. 1, raw water is introduced into the aerobic biological reaction tank 1 through the pipe 11 and subjected to an aerobic biological reaction treatment, similar to the apparatus shown in FIG. 5(b). The treatment liquid is introduced into the membrane separator 2 via the introduction pipe 12, and during this time, air is supplied from the supply pipe 15, and the liquid is introduced into the membrane separator 2 as a gas-liquid mixture.

The permeated water of the membrane separator 2 is taken out as treated water, while the concentrated water is returned to the aerobic biological reaction al.

In the corrugated type membrane module 2B used in the device of this embodiment, as shown in FIG. A net-like spacer 24 is loaded inside the portion 11g23. When assembling this membrane Modineal 2B, one short side of the bag-shaped separation membrane 23 is attached to the water collection pipe 21.

(An opening is provided on the circumferential surface of the water collection pipe 21 so that the inside of the bag communicates with the inside of the water collection pipe 216) Next, this bag-shaped portion MIi 23 is wound around the outer periphery of the water collection pipe 21. At this time, a corrugated spacer 22 is interposed between the 11I films 23.

In the membrane module 2B assembled in this manner, the raw water flows from one end surface of the wound body along the spacer 22 to between the separation membranes 23 as shown by the arrow in FIG. It flows out from the other end face of the wound body as shown in M. While the raw water is flowing along the spacer 22, the liquid passes through the separation membrane 23 and enters the bag-shaped separation membrane 23. Inside the bag-shaped membrane 23, permeated water flows toward the water collection pipe 21 along the net-shaped spacer 24,
Finally, it flows into the water collecting pipe 21 and is taken out from the membrane module 2B as permeated water.

In such a corrugated membrane module 2B, when the gas-liquid mixture flows into the channel along the corrugated spacer 22 or while flowing through the narrow channel along the spacer 22, the gas-liquid mixture is The air bubbles are finely sheared,
Forms microbubbles and efficiently dissolves in liquid.

As a result, the air in the bubble mixture that has flowed into the membrane dividing device 2 is sufficiently dissolved into the liquid while flowing through the membrane module 2B together with the liquid. After the liquid sufficiently dissolved in air passes through the membrane module 2B, it is returned to the aerobic biological reaction treatment device and subjected to extremely efficient biological treatment.

FIGS. 2 and 3 are system diagrams showing another embodiment of the organic wastewater treatment apparatus of the present invention. In FIGS. 2 and 3, a pipe 17 for discharging excess sludge from the middle of the concentrated water pipe 14
is branching out. The rest of the structure is similar to that of the apparatus shown in FIG. 1, and members having the same functions as those in FIG. 1 are given the same reference numerals.

In the organic wastewater treatment equipment shown in Figure 2 and the organic wastewater treatment equipment shown in Figure 3, an aerobic biological reaction treatment tank (aeration tank) is used.
The only difference is the connection position of the concentrated water circulation pipe 14 of the membrane separation device 2 to the membrane separation device 1, and the other configurations are the same. Thus, in the present invention, there is no restriction on the connection position of the circulation piping 14, and it may be in the upper part or the lower part of the aerobic biological reaction tank 1.

In addition, in FIGS. 2 and 3, aerobic biological reaction M
Air is supplied via a pipe 15 by a blower or the like to the suction side (upstream side) of the pump P of the introduction pipe 12 that introduces the treated liquid No. 1 into the membrane separation device 2. By supplying air to the pump, the air can be introduced at a low pushing pressure, and the dissolution of the air can also be promoted during the process of passing through the pump, which is extremely advantageous.

This air supply means is not limited to the air pressure feeding method using a blower, but may be configured such that the air supply section is in the form of an ejector so as to self-suction the atmosphere, as shown in FIG.

In the case of a single ejector type, the air intake open end of the air supply pipe 15 is provided at a position higher than the water level of the aerobic biological reaction tank 1 to prevent backflow of liquid when the pump P is stopped.

Further, as shown in FIGS. 1 to 3, when connecting the air supply pipe 15 to the suction side of the pump P, it is necessary to select a pump that can be operated even when sucking air. As such a pump, for example, a centrifugal pump or the like can be used.

In the present invention, the amount of air supplied into the treatment liquid is preferably 5 to 10% (volume ratio) of the amount of water fed to the aerobic biological reaction treatment liquid. The spiral membrane module 2B of the membrane separation apparatus 2 according to the present invention can ensure a sufficiently high flux with a smaller air supply amount than such a normal membrane module. Note that even if the air supply amount exceeds 10%, it will not have much effect on improving the flux, and on the contrary, the energy cost for air supply will increase, and favorable operating conditions will be maintained due to vibration of the introduction pipe 12, etc. There may be problems such as not being able to do it.

In the present invention, the spiral membrane module includes:
As shown in FIG. 7, it is preferable that the corrugated spacer 22 has continuously extending and meandering corrugations. In such a spiral membrane module, the flow along the membrane surface is disturbed by the meandering ripples. This eliminates concentration polarization and further increases the flux.

Moreover, the raw water flow path is continuous without interruption, and S
S is also less likely to get caught, and blockage of the raw water flow path is also prevented. For this reason, relatively low membrane flow velocity, e.g. 0.5
It is possible to maintain a high flux even at ~1.0 m/s. Moreover, according to the spiral membrane module including the corrugated spacer having such a turbulent flow promoting function, even higher air dissolution efficiency can be obtained.

In the organic wastewater treatment apparatus of the present invention, since air supply and membrane separation can be performed simultaneously, separate
Although it is not necessary to provide an air supply line, it goes without saying that it may be provided.

The present invention will be explained in more detail with reference to specific examples below.

Example 1. Comparative Example 1 Oxygen dissolution efficiency was measured using an aerobic biological reaction tank and a membrane separation device. The specifications of each device are as follows.

Aerobic biological reaction tank Water depth: 2m Effective water volume: 35011 Membrane separation device membrane module: Spiral type membrane module with a diameter of 100mm and a length of 1000mm.

The effective flow path height due to the corrugated spacer is 2.5mm.

That is, as shown in FIG. 1 (Example 1) or FIG. 4 (Comparative Example 1), the liquid from the aerobic biological reaction [1] was introduced into the membrane separation device 2 through an introduction pipe 12 equipped with a pump P. , membrane S
The concentrated water of the device is passed through the circulation piping 14 to perform an aerobic biological reaction a.
! In a system where city water is circulated at
When introducing the membrane separator 2 at m/s, the ventilation ratio is 2vvh (airflow ratio per aerobic biological reaction tank).
As shown in Table 1 below, by supplying air from pipe 15 or 16 (ejector in Figure 4) and determining KL (oxygen dissolution capacity coefficient) from the rising curve of dissolved oxygen, I sought efficiency.

Table 1 Example 2. Comparative Example 2 Using the apparatus of Example 1 and Comparative Example 1, synthetic sewage (peptone, glucose substrate) (BOD = 1200 mg, /4
2) was performed continuously. In addition, the membrane surface flow velocity is 0.5 m
The process was carried out under the same conditions except that /s was set. The obtained flux is shown in Table 2.

Table 2 Comparative Example 3 In Example 2, as a membrane module of the membrane separation device,
When the treatment was carried out in the same manner except that a normal spiral membrane module was used, which consists of a membrane wrapped around the outer periphery of the water collection pipe through a net-like spacer, the operation continued due to clogging due to SS. I couldn't do it.

From the above results, it is clear that according to the organic wastewater treatment apparatus of the present invention, it is possible to increase the flux and at the same time effectively utilize oxygen for aerobic biological treatment.

Example 3 In Example 2, continuous treatment was performed by changing the aeration amount,
The relationship between air flow and flux was investigated, and the results are shown in Figure 6.

Note that an excessive amount of aeration was separately performed in the aerobic biological reaction tank, so that even if the aeration amount on the pump suction side was changed, the dissolved oxygen concentration etc. were not affected.

As is clear from Figure 6, (aeration amount/water supply amount) x 10
A good flux recovery effect is observed when the ratio (volume ratio) of 0 is in the range of 5 to 10%.

It has been found that even if this ratio exceeds 10%, a remarkable recovery effect of the flux is not observed, but on the other hand, vibrations of piping, etc. increase, making it impossible to maintain favorable operating conditions.

[Effects of the Invention] As detailed above, according to the organic wastewater treatment device of the present invention, the energy efficiency of the entire device is improved, air is effectively used for aerobic biological reaction treatment, oxygen dissolution efficiency is improved, and membrane This improves the flux of the separation device, suppresses the formation of a gel layer on the membrane surface, and prevents clogging. Therefore, it is possible to treat organic wastewater more efficiently and at lower cost.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing an outline of the organic wastewater treatment device of the present invention, Figs. 2 and 3 are system diagrams showing an embodiment of the organic wastewater treatment device of the present invention, and Fig. 4 is the ejector structure. 5 is a system diagram showing a conventional example, FIG. 6 is a graph showing the results of Example 3, and FIG. 7 is an assembled perspective view showing an example of a spiral membrane module. 1...Aerobic biological reaction tank, 2...Membrane separation device, 2B...Spiral type membrane module.

Claims (1)

[Claims] (1) Equipped with an aerobic biological reaction tank that processes organic wastewater by an aerobic biological reaction, and a membrane separation device that performs membrane separation treatment on the treated liquid of the aerobic biological reaction tank, and that concentrates the concentrated water of the membrane separation device. An organic wastewater treatment device configured to return the water to the aerobic biological reaction tank is provided with an air supply means for supplying air to the treated liquid of the aerobic biological reaction tank introduced into the membrane separation device, and An organic wastewater treatment device characterized in that the membrane module is a spiral membrane module in which a separation membrane is wound around the outer periphery of a water collection pipe with a corrugated spacer interposed therebetween.