JPH09294996A - Method and apparatus for treating organic waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the washing frequency of a membrane and to eliminate the labor for maintenance and control while extending the life membrane by reducing the contamination of the membrane in a membrane separation type activated sludge method and to provide technique suppressing the rising of filtering pressure in order to ensure the amt. of treated water. SOLUTION: In an org. waste water treatment method by a membrane separation type activated sludge method, a reaction process having two or more reaction chambers 3 and introducing org. waste water 11 into at least the first reaction chamber 3 and setting soluble BOD in the outflow water from the final reaction chamber 3 to 5-100mg/l, a separation process subjecting the outflow water from the reaction process to membrane separation while oxygen- containing air is diffused and a circulating process circulating separated residual water containing activated sludge in the separation process to the reaction process are provided.

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 for organic wastewater discharged from a business site or the like, in which solid-liquid separation of sludge and treated water is carried out by a membrane directly immersed in an activated sludge treatment tank. Type activated sludge method.

[0002]

2. Description of the Related Art Organic wastewater (hereinafter also referred to as raw water) 11 using a conventional membrane separation type activated sludge method as shown in FIG.
When performing the aerobic treatment, the module of the separation membrane (hereinafter, also simply referred to as a membrane) 5 is directly permeated into the activated sludge treatment tank 1 containing the activated sludge, and the treated water 12 is obtained by suction or water pressure. In addition, it has a structure for maintaining the filtration function of the separation membrane 5 by utilizing the air diffuser 6 in the tank.
Since the mixing and reaction of the organic waste water 11 and the activated sludge, the decomposition / removal of the organic matter, and the solid-liquid separation can be performed only by the activated sludge treatment tank 1, the sedimentation tank is unnecessary. Also, the need for sedimentation separation is eliminated, and the activated sludge concentration is 10,000 mg /
Can be operated at a high concentration of about 1 liter, and activated sludge treatment tank 1
Since the capacity can be reduced, there is an advantage that the installation space can be reduced. In addition, by using the separation membrane 5 for solid-liquid separation, it is possible to reliably separate the solid content in the liquid, and to obtain good treated water 12 containing no suspended matter.

[0003]

However, when the BOD concentration of the waste water to be treated exceeds 1,000 mg / liter, the separation membrane 5 is significantly contaminated and the membrane 5 is clogged, and the membrane 5 is clogged.
Since the amount of water that permeates through the water decreased, it became necessary to wash the water several times a year. For this reason, it takes a lot of time to perform maintenance such as cleaning of the membrane 5 and monitoring of the amount of water, and the cleaning is repeated.
The damage to the item has increased.

The inventors of the present invention have made a study on the actual construction and found that the film contamination becomes remarkable when the residual BOD in the vicinity of the film is high. It can be said that this is the first known membrane contamination index. In the case of the membrane-separated activated sludge method, the inflow of wastewater to the separation of treated water is performed in the same tank, and the reaction tank volume is small, so the distance and time from the inflow of wastewater to the permeation of the membrane are shortened. When the concentration of organic matter in the wastewater is high, there is a possibility that the wastewater may pass through the membrane portion without being completely mixed and reacted and thus not sufficiently treated, which may deteriorate the quality of the treated water 12 or contaminate the membrane 5. . When applied to wastewater such as domestic wastewater and sewage, the inflow BOD is as low as 1,000 mg / liter or less, and the raw water 11 passes through the membrane 5 by the short path through the activated sludge treatment tank 1 The effect of the film contamination that occurred in 1 was large.

[0005] In the membrane-separated activated sludge method, if the membrane 5 is not clogged, it is a very easy technique for maintenance. Therefore, according to the present invention, in the membrane-separated activated sludge method, by reducing the membrane pollution, the frequency of cleaning the membrane 5 is reduced, the maintenance and maintenance work is eliminated, and the life of the membrane 5 is extended to secure the amount of treated water. Therefore, it is an object to provide a technique for suppressing an increase in filtration pressure.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventor has made the distance and time from the inflow of waste water to the permeation of the membrane longer, and the solubility BOD in the vicinity of the separation membrane is 5 to 100.
It was found that the membrane contamination was small if mg / liter,
The present invention has been completed based on this finding. That is, the present invention provides (1) a method for treating organic wastewater by a membrane separation type activated sludge method, which has one or more reaction chambers, and the organic wastewater is introduced into at least the first reaction chamber and the last reaction chamber. Of the soluble BOD in the effluent from the water of 5 to 100 mg / liter, a separation step of performing membrane separation of the effluent from the reaction step under oxygen-containing gas diffusion, and a separation residue containing activated sludge in the separation step. A method for treating organic wastewater, comprising a circulation step of circulating water to a reaction step,
(2) In the reaction step, the BOD when the organic wastewater and the residual water separated from the circulation step are mixed is 500 to 750.
The method for treating organic wastewater according to (1) above, characterized in that

(3) In the reaction step, the BOD volume load is 3.5 to 6.0 kg-BOD / m ³ · day, and the residence time of the separated residual water from the circulation step and the mixed water of the organic waste water is 2
~ 5 hours, the method for treating organic wastewater according to (1) above, (4) the volume load of activated sludge circulated in all the steps is 0.5 to 5 kg-BOD / m ³ · (1) characterized in that the amount of water is adjusted so that it becomes a day
(5) The method for treating organic wastewater according to (1) above, wherein a microorganism-attached carrier is introduced into the reaction step, and recovery means for the carrier is provided between the reaction step and the separation step.
A method for treating organic wastewater according to any one of (4),
(6) An organic wastewater treatment apparatus having an immersion sludge separation membrane in an activated sludge treatment tank, which carries out the above treatment, wherein the activated sludge treatment tank is separated from one or more reaction chambers by an in-tank water short path preventing means. An apparatus for treating organic wastewater, comprising a separation chamber in which the separated separation membrane is immersed, and having a circulation means for circulating sludge from the separation chamber to the reaction chamber. As the short-pass prevention means here, a baffle plate, a partition wall, and the like in the same tank may be provided, or the reaction chamber and the separation chamber may be provided as separate tanks that communicate with each other.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An example of the device of the present invention is shown in FIGS.
Will be described below. In the device of the present invention, the activated sludge treatment tank 1 is a separate tank or a partition 2 is inserted,
It is composed of one or more reaction chambers 3 and a final separation chamber 4. Alternatively, a baffle plate is provided in the activated sludge treatment tank 1 to make a bypass. The inflow / outflow portions of the reaction chamber 3 are alternately provided above and below or to the left and right of the tank 1, and the linear distance between the inflow / outflow portions of the reaction chamber 3 is long.
In order to achieve this condition, the solubility BOD in the separation chamber (step) 4 in which the membrane separation is performed is set to 5 to 100 mg / liter. In addition, FIG. 1 shows an apparatus in which one activated sludge treatment tank 1 is divided into a reaction chamber 3 and a separation chamber 4, and FIG. 2 shows an example in which the activated sludge treatment tank 1 is divided into two reaction chambers 3 and a separation chamber 4. FIG. 3 shows an example of an apparatus in which the activated sludge treatment tank 1 is separated into two reaction chambers 3 and two separation chambers 4.

Volume of activated sludge in the activated sludge treatment tank 1 as a whole
The load is 0.5 to 5 kg-BOD / m ^Three・ Be less than a day
BOD of inflowing wastewater is 500 ~ 750mg /
The final stage is a mixture of activated sludge that is diluted to 1 liter
It is circulated from the separation chamber 4 of. The capacity of one reaction chamber 3 is
BOD volume addition is 3.5-6.0kg-BOD / m^Three・
The residence time including circulating water will be 2 to 5 hours a day.
Then, a reaction of a number is performed for 4 volumes of the reaction tank excluding the separation chamber 4.
A room 3 is provided.

The number of rooms a is calculated by the following equation. _{a = V R / V 1 a} : Number of reaction chamber [chamber] (Integer: rounded down) VR: reaction chamber total volume _{V R = V A -V M V} A: the reaction tank capacity [m ^3] V _M: the separation chamber Capacity [m ³ ] (minimum capacity for installing a separation membrane) V ₁ : BOD volume load is 3.5 to 6.0 kg-BOD /
m ³ · day, residence time including circulating water is 2 to 5 hours. The number of chambers is determined as the volume [m ³ ] per reaction chamber.

BOD is sufficiently adsorbed or decomposed in one or more reaction chambers 3 in the preceding stage so that the soluble BOD concentration is 5 to 100.
After removal to mg / l, the treated water 12 is obtained by suction or water pressure through the membrane 5 installed in the latter stage. The activated sludge transferred to the subsequent stage is transferred to the foremost stage as the circulating water 13, mixed with the raw water 11 again, and reacted and treated. Thereby, the treated water 12 having good water quality is obtained, the progress of the contamination of the membrane 5 is slowed down, the cleaning frequency is reduced, and at the same time, the life of the membrane 5 is extended. The gist of the present invention is that the index of membrane contamination is BOD in the vicinity of the membrane instead of SS,
In particular, it has been found that it is preferable to use dissolved BOD, and the level is limited by the efforts of the inventor. Although the BOD value is usually removed by the action of activated sludge and is reduced from the inlet, it was found that most of the membrane contamination was due to the short path of high BOD drainage.

The activated sludge treatment tank 1 is divided by providing a plurality of tanks or partitions in the tanks, an inflow section for the raw water 11 is provided at the forefront stage of the reaction chamber 3, and the treated water 12 is provided at the separation chamber 4 at the last stage. Install the membrane 5 to obtain. Each room is provided with an air diffuser 6 for aerating an oxygen-containing gas so that the amount of air in each room can be adjusted as necessary. The raw water 11 is agitated and bypassed so that the raw water 11 can be sufficiently mixed and reacted through each chamber and each chamber. A circulation pump 7 is installed in the separation chamber 4 at the final stage. Raw water (drainage) 11 is allowed to flow into the reaction chamber 3 at the front stage, and at the same time, the liquid in the tank, preferably the liquid in the separation chamber 4 at the last stage is advected, and mixed and reacted in the chamber 3 in which the membrane 5 is not immersed. When advancing to the separation chamber 4 at the final stage where the membrane 5 is immersed, the concentration of the remaining organic matter becomes 5 to 100 mg / liter as a soluble BOD, and the treated water 12 is sucked through the membrane 5 or hydraulically.
Get. Since the liquid that permeates the membrane 5 contains almost no organic matter that is the source of contamination of the membrane 5, the progress of contamination of the membrane 5 by the organic matter can be made extremely slow.

When the concentration of inflowing BOD is further high, as shown in FIG. 4, in the reaction chamber 3 in which the membrane 5 is not immersed, the bioadhesive carrier 8 made of an organic gel is charged. At this time, the screen 9 is installed so as to prevent the carrier 8 together with the liquid in the tank from being transferred to the reaction chamber 3 or the separation chamber 4 in the subsequent stage by the charged reaction chamber 3. Carrier 8 in reaction chamber 3
It is possible to accelerate the removal and decomposition of the organic matter in the reaction chamber 3 and reduce the amount of the organic matter remaining in the separation chamber 4 by introducing the.

[0014]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto. [Example 1] As shown in Fig. 5, a partition 2 was provided in the activated sludge treatment tank 1 such that the front stage was 12 m ³ , the middle stage was 12.5 m ³ , and the rear stage was 15.5 m ³ . The partition 2 between the front stage and the middle stage has an opening so as to allow advection from the lower side, and the partition 2 between the middle stage and the rear stage is a piston flow type in which an opening is provided so as to overflow the upper side. ing. Membrane 5
Is immersed in the rearmost part of the latter tank, and 20 hollow fiber membrane modules (4 m / piece) are arranged. A circulation pump 7 is installed so as to be able to circulate from the latter tank to the former tank, and when drainage flows from the flow rate adjusting tank 10 into the former tank, this pump operates at the same time and the mixed liquid of activated sludge from the latter tank to the former tank. Circulate and mix with drainage. An air diffuser 6 is provided in each stage, and air is diffused so that DO is at least 1 mg / liter or more. Using this tank, the waste water with a water amount of 156 m ³ / day, BOD of 4,000 mg / liter, and SS of 700 mg / liter is used as a reaction tank MLS.
The treatment was carried out with S8,000 mg / liter.

The waste water is once stored in the flow rate adjusting tank 10 and is constantly transferred from here to the former tank by a pump. The treated water 12 is obtained by suction with a pump at the tip of a pipe attached to the module of the hollow fiber membrane immersed in the latter-stage tank. When the circulation pump is operated at the same time as the inflow of the wastewater to mix the wastewater and the circulating water 13, the BOD concentration is 50
The circulating water amount was transferred to be about 5 times the inflowing drainage amount so that the amount became 0 to 750 mg / liter and transferred to the pre-stage tank. When the BOD before the inflow to the latter-stage tank in which the membrane 5 was installed was treated with 95 mg / liter or less by the above operating method without adding the carrier, the membrane 5 was not contaminated for one year,
Treated water with suction pressure of 0.05 to 0.3 kgf / cm ²
was gotten. The BOD of the obtained treated water 12 was 5 mg / liter or less.

[Example 2] 10% of a carrier (particle size: 3 to 5 mm) was charged into the reaction chamber 3 at the front stage, and the water flow was 20 with the same water quality.
Treated as m ³ / day. When the amount of circulating water was transferred so as to be about 6 times the amount of inflowing wastewater and treated, the BOD before the inflow of the latter stage where the membrane 5 was installed was 50 mg / liter or less, and similarly, the membrane 5 was not contaminated for one year. Moreover, the treated water 12 was obtained at a suction pressure of 0.05 to 0.30 kgf / cm ² , and the BOD of the treated water 12 was 5 mg / liter or less.

[Comparative Example 1] Partition 2 in activated sludge treatment tank 1
When the operation was carried out without the addition of the filter, the filtration pressure of the membrane 5 exceeded 0.4 kgf / cm ² after about 6 months, and the membrane 5 had to be washed. In contrast to Comparative Example 1, when the partition 2 is placed in the tank 1, there is no need for cleaning even after about 1 year has passed, and it is 0.3 kgf / cm ² or less. By this, the progress of the contamination of the membrane 5 was slowed down, the cleaning frequency was reduced, and good treated water 12 could be obtained.

[0018]

Industrial Applicability According to the present invention, by dividing the activated sludge treatment tank, a long path from the raw water flowing into the activated sludge treatment tank to the permeation of the membrane is secured, and a short path may occur. Therefore, the reaction of decomposing (removing) the organic substance can be sufficiently performed. In addition, since the activated sludge mixed solution that has been treated is circulated water and mixed with the raw water in the reaction chamber at the front stage, the organic matter in the raw water and the activated sludge are efficiently contacted and reacted. By these actions, it is possible to completely remove the organic matter in the raw water in the reaction chamber in the previous stage,
In the latter-stage separation tank, the solubility BOD in the mixed solution is 1 to 5 m.
It becomes g / liter. Therefore, the growth of organisms on the surface of the film can be almost completely suppressed, and the film is not clogged due to the contamination of the film with the organic matter. As a result, the quality of the permeate that passes through the membrane is stable in a good state,
The frequency of cleaning the membrane was reduced and the life of the membrane was extended.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an organic wastewater treatment apparatus of the present invention.

FIG. 2 is a diagram showing another example of the organic sewage treatment apparatus of the present invention.

FIG. 3 is a view showing another example of the organic sewage treatment apparatus of the present invention.

FIG. 4 is a view showing another example of the organic sewage treatment apparatus of the present invention.

FIG. 5 is a diagram showing an organic wastewater treatment apparatus used in Examples.

FIG. 6 is a diagram showing an example of a conventional organic sewage treatment apparatus.

[Explanation of symbols]

 1 Activated sludge treatment tank 2 Partition 3 Reaction tank 4 Separation tank 5 Separation membrane 6 Diffuser 6 Circulation pump 8 Carrier 9 Screen 10 Flow control tank 11 Organic wastewater 12 Treated water 13 Circulating water

Claims (6)

[Claims] 1. A method for treating organic wastewater by a membrane separation activated sludge method, which comprises one or more reaction chambers, wherein the organic wastewater is introduced into at least the first reaction chamber and the effluent water from the last reaction chamber is introduced. Of which the soluble BOD is 5 to 100 mg / liter, a separation step in which effluent water from the reaction step is subjected to membrane separation under oxygen-containing gas diffusion, and a separation residual water containing activated sludge in the separation step A method for treating organic wastewater, comprising: 2. The BOD when the organic waste water and the residual water separated from the circulation step are mixed in the reaction step is 500.
The method for treating organic wastewater according to claim 1, wherein the treatment amount is set to 750 mg / liter. 3. In the reaction step, the BOD volume load is 3.5 to 6.0 kg-BOD / m ³ · day, and the residence time of the mixed water of the separation residual water from the circulation step and the organic waste water is 2 to 5
The method for treating organic wastewater according to claim 1, wherein the method is performed for a period of time. 4. The organic substance according to claim 1, wherein the amount of water is adjusted so that the volume load of the activated sludge circulated in all the steps is 0.5 to 5 kg-BOD / m ³ · day. Wastewater treatment method. 5. The method according to any one of claims 1 to 4, wherein a carrier having a microorganism attached thereto is introduced into the reaction step, and a recovery means for collecting the carrier is provided between the reaction step and the separation step. How to treat organic wastewater. 6. An organic wastewater treatment apparatus having an immersion sludge separation membrane in the activated sludge treatment tank, wherein the activated sludge treatment tank is 1
It is characterized by having the above-mentioned reaction chamber and a separation chamber in which the separation membrane separated by the in-tank water short path preventing means is immersed, and having a circulation means for circulating sludge from the separation chamber to the reaction chamber. A device for treating organic wastewater.