JPH105762A - Activated sludge process and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a reduction of a membrane permeated water quantity with time due to an adhesion.deposition of a high polymer, etc., to a membrane module by subjecting a mixed soln. containing a slurry product formed in an aeration tank to an ozone treatment, then obtaining a treated water by subjecting this mixed soln. to a solid liq. separation with a membrane separating device. SOLUTION: When a raw waste water containing an org. material is supplied to an aeration tank 12 from a regulating tank 11, the org. material in the waste water is decomposed oxidatively with an aerobic bacteria working actively by aeration to an air sent from an air diffuser 14 and an activated sludge is formed. In this case, an ozone treating device 22 is connected to the aeration tank 12 with a piping, and after subjecting the mixed soln. (activated sludge) 15 containing the slurry product formed in the aeration tank 12 to the ozone treatment, the mixed soln. 15 is subjected to the solid-liq. separation with the membrane separating device 16. That is, a fibrous material inflowing from the raw waste water and preventing the membrane separation is decomposed and conveted into low molecule by the ozone treatment, and also sugars are reduced to reduce a viscosity of the mixed soln. 15 and the reduction of the membrane permeated water quantity with time is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention biologically processes and produces wastewater containing organic substances, such as domestic wastewater such as municipal sewage and settlement wastewater, livestock human wastewater, fishery processing wastewater, and agricultural processing wastewater. The present invention relates to a membrane separation activated sludge method for solid-liquid separation of sludge-like reactants by a membrane separation device and an apparatus therefor.

More specifically, the present invention relates to a membrane separation activated sludge method capable of suppressing blockage of pores of a membrane by sludge particles, extending the membrane life of a membrane separation device, and reducing the amount of sludge generated, and a device therefor. .

[0003]

2. Description of the Related Art In order to cope with the problem of deterioration of sedimentation and separability of activated sludge in the conventional standard activated sludge method and the advanced treatment of sewage treatment plants, a membrane separation device comprising a membrane module is used. A membrane separation activated sludge method has been proposed (Japanese Patent Publication No. 4-70958).

FIGS. 3 and 4 show the configuration of an activated sludge apparatus used in the membrane separation activated sludge method. 3 and 4, reference numeral 12 denotes an aeration tank which is a biological reaction device, 15 denotes a mixed solution (so-called activated sludge) of a liquid to be treated (drainage) and a sludge-like reactant (hereinafter referred to as a mixed solution), 16, 19 Denotes a membrane separation device including membrane modules 17 and 20 and pumps 18 and 21.

[0005] In this method, a mixed solution containing a sludge-like reactant generated in an aeration tank 12 is converted into a primary solution of a membrane module 17 or 20 such as a UF (ultrafiltration) membrane module or an MF (microfiltration) membrane module. By supplying to the side and performing membrane filtration, membrane permeated water is obtained as treated water from the mixed solution. According to this method, a sedimentation separation tank is not required,
The sedimentation and separability of activated sludge is no longer a problem,
The processing apparatus can be made compact, and a tertiary processing apparatus for advanced processing can be easily added.

However, when the membrane separation method is applied as a solid-liquid separation method of the activated sludge method, polymer substances and solids (particles) in the activated sludge adhere to and accumulate on the membrane, and the amount of water permeated through the membrane increases with time. And the life of the film is shortened. Therefore, in the membrane separation activated sludge method, there is a strong demand for a technique capable of effectively suppressing a decrease in the amount of membrane permeated water over time, thereby extending the life of the membrane, and reducing the membrane cost in sewage treatment.

Another problem of the activated sludge method in general is the treatment and disposal of excess sludge. That is, with the increase in the amount of sludge generated in recent years, securing a final disposal site for incinerated ash and the like has become a major problem, and there is a strong demand for the development of a method of treating wastewater containing organic substances that generates a small amount of sludge.

[0008]

SUMMARY OF THE INVENTION According to the present invention, in a membrane separation activated sludge method having the above-mentioned advantages, it is possible to suppress a temporal decrease in the amount of water permeated through a membrane due to adhesion and deposition of a polymer substance or the like on a membrane module. It is another object of the present invention to provide a membrane separation activated sludge method and apparatus capable of generating a small amount of sludge.

[0009]

A first aspect of the present invention is an activated sludge method used for treating raw wastewater containing an organic substance, wherein a mixed solution containing a sludge-like reaction substance generated in an aeration tank is used. The activated sludge method is characterized in that the mixed solution subjected to the ozone treatment is subjected to solid-liquid separation by a membrane separation device to obtain treated water.

[0010] A second invention is an activated sludge apparatus for treating raw wastewater containing organic substances, wherein the activated sludge apparatus includes an aeration tank and a sludge-like reactant generated in the aeration tank. An ozone treatment device for ozone treatment of the mixed solution, a membrane separation device that is a solid-liquid separation unit for the mixed solution in the aeration tank, and the mixed solution in the aeration tank with the aeration tank and the ozone treatment device. An activated sludge apparatus having a circulating means for circulating between them.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. 1 and 2 show examples of the configuration of the activated sludge apparatus of the present invention. 1 and 2, reference numeral 22 denotes an ozone treatment device (hereinafter, referred to as an ozone treatment device) for the mixed solution 15 in the aeration tank 12, which comprises an ozone generator 23, a reactor 24, and a pump 25. Reference numerals indicate the same contents as in FIGS.

The membrane modules 17 and 20 in FIGS. 1 and 2 are preferably UF (ultrafiltration) membranes,
A filtration membrane module selected from an MF (microfiltration) membrane or the like is exemplified. Raw wastewater containing organic substances is supplied to the regulating tank 11
Is supplied to the aeration tank 12, and the organic substances contained in the wastewater are oxidatively decomposed by aerobic bacteria that are actively active by aeration to the air supplied from the blower 13 through the diffuser 14, A mixed solution containing sludge-like reactants, ie, activated sludge, is formed.

The mixed solution in the aeration tank 12 is
Membrane module 17 installed outside the aeration tank connected by piping
Alternatively, solid-liquid separation is performed by the membrane module 20 immersed in the mixed solution 15 in the aeration tank 12, and the treated water is obtained as membrane permeated water on the secondary side of each membrane module. In the present invention, an ozone treatment device 22 for a mixed solution (activated sludge) is connected to the aeration tank 12 by piping, and the mixed solution 15 containing the sludge-like reactant generated in the aeration tank 12 is ozone-treated, and The treated mixed solution is transferred to membrane separation devices 16, 19
To obtain treated water.

According to the activated sludge apparatus of the present invention, the mixed solution 15 from the aeration tank 12 is supplied to the reactor 24 by the pump 25, and the ozone-containing gas from the ozone generator 23 is supplied to the reactor 24. After the ozone treatment is performed, the mixed solution is returned to the aeration tank 12, and is treated cyclically. It is considered that the reaction occurring in the reactor 24 at this time is mainly caused by the cleavage of the molecule by the action of ozone on the chemical bond of the molecule, ie, the reduction of the molecular weight of the organic polymer.

For this reason, fibrous materials which flow from raw wastewater and adhere to the membrane to inhibit membrane separation are decomposed by ozone treatment to a considerable extent to be reduced in molecular weight, and saccharides also have a molecular weight of 1/10.
To this extent, the viscosity of the mixed solution (activated sludge) decreases. According to the action of ozone on the mixed solution described above, according to the present invention, a temporal decrease in the amount of membrane permeated water, which is an important problem in the membrane separation activated sludge method, is significantly suppressed,
Furthermore, the amount of excess sludge is reduced.

From the above-described action of ozone, in the present invention, the ozone treatment of the mixed solution and the solid-liquid separation of the mixed solution by the membrane separation device may be performed in parallel with time.
The method may be performed separately over time, and the method is not limited. However, a method performed in parallel with time is more preferable for the purpose of preventing the adhesion of the polymer substance to the film surface. In the present invention, the ozone supply amount in the ozone treatment apparatus 22 is such that the BOD of the raw wastewater is about 150 to 200 mg / l, the SS is about 100 to 200 mg / l, and the MLSS of the aeration tank is about 1500 to 6000 mg / l. , preferably _{0.015 ~0.075kg -O 3 / kg-MLSS} / day,
It is more preferred that in _{0.03~0.05kg-O 3 / kg-MLSS} / day.

The supply amount of ozone is 0.015 kg-O ₃ / kg-MLSS /
In the case of less than a day, the effect of suppressing occlusion of pores of the membrane of the membrane module and the effect of reducing excess sludge by ozone treatment are small,
For more than 0.075kg -O ₃ / kg-MLSS / day, these effects are saturated, it is not economical. Further, in the present invention, the circulation amount (l / h) of the mixed solution from the aeration tank 12 to the ozone treatment device 22 per unit time (l / h) is 5 to 5 times the treatment amount (l / h) of the raw wastewater per unit time. 40% is preferable, and 10 to
More preferably, it is 30%.

If the amount is less than 5%, the effect of suppressing occlusion of pores in the membrane of the membrane module and the effect of reducing excess sludge by ozone treatment are small. If the amount exceeds 40%, these effects are saturated and are not economical. The activated sludge apparatus of the present invention employs a system in which the mixed solution is circulated between the aeration tank 12 and the ozone treatment device 22, because it has an advantage of improving ozone treatment efficiency for the mixed solution.

According to the present invention, the ozone supply amount and the circulating amount of the mixed solution are preferably set within the above ranges, whereby the clogging of the pores of the membrane by the sludge particles is suppressed, and the life of the membrane is significantly extended. It is possible to further reduce the amount of surplus sludge generated to 70 to 0% of the conventional activated sludge method.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. (Embodiment 1) The treatment of domestic wastewater was performed using the activated sludge apparatus according to the present invention shown in FIG.

The volume of the aeration tank 12 is 45 liters,
150l / day, aeration tank residence time is 7.2 hours. The UF (ultrafiltration) membrane module used in the membrane separator 16 is
It is a hollow fiber type having a molecular weight cut off of 13000 and an effective membrane area of 0.2 m ² . Air is supplied to the mixed solution in the aeration tank 12 by the blower 13 at a flow rate of 2 l / min, and the mixed solution 15 is sent to the membrane module 17 by the pump 18 while being aerated, and the differential pressure is 2 kg / c.
The membrane was separated at m ² , and a part of the mixed solution was continuously drained while being extracted as excess sludge.

During this time, the mixed solution 15 is removed from the aeration tank 12.
And the ozone-containing gas from the ozone generator 23 are supplied to the reactor 24 to ozone-treat the mixed solution, the ozone-treated mixed solution is returned to the aeration tank 12, and the mixed solution in the aeration tank is continuously discharged. Ozone treatment. Incidentally, the ozone supply amount of the ozone treatment apparatus _{22, 0.04kg-O 3 / kg-} MLSS /
On the other hand, the circulation amount (l / h) of the mixed solution from the aeration tank 12 to the ozone treatment device 22 per unit time (l / h) was set to 20% of the treatment amount (l / h) of the raw wastewater per unit time.

As a result of continuous operation of the activated sludge apparatus by the above method, the amount of permeated water was 1.47 at the beginning of the treatment of raw wastewater.
m ³ / m ² / day, after 24 hours, 1.46 m ³ / m ² / day, the amount of excess sludge generated was 1.9 g, and the average MLSS was 4500 mg / l. The average BOD of the raw wastewater during the continuous operation period was 190 mg / l and the average SS was 132 mg / l, while the average BOD of the treated water was 1.9 mg / l.
The average SS was 0.1 mg / l.

(Comparative Example 1) Using the apparatus shown in FIG.
The continuous operation of the activated sludge apparatus was performed under the same conditions as in Example 1 except that ozone treatment of the mixed solution 15 was not performed. As a result, the amount of permeated water was 1.40 m ^{3 at the} beginning of the treatment of raw wastewater.
/ m ² / day, after 24h lapse is at 0.39 m ³ / m ² / day, the amount of excess sludge, 5.7 g, the average MLSS was 4600mg / l.

Further, the average BOD of the raw wastewater during the continuous operation period
Is 192 mg / l and the average SS is 158 mg / l, while the average
D was 1.1 mg / l and average SS was 0.1 mg / l. (Example 2) Domestic wastewater was treated using the activated sludge apparatus according to the present invention shown in FIG.

The volume of the aeration tank 12 is 45 liters,
150l / day, aeration tank residence time is 7.2 hours. The MF (microfiltration) membrane module used in the membrane separator 19 is
It is a hollow fiber type having a pore diameter of 0.35 μm and an effective membrane area of 0.1 m ² . While supplying air to the mixed solution in the aeration tank 12 by the blower 13 at a flow rate of 2 l / min and aerating, the secondary side of the membrane module 20 is depressurized to about 0.2 atm by the pump 21 to continuously perform drainage treatment. I went to.

During this time, a part of the mixed solution was withdrawn as excess sludge, and the MLSS was kept almost constant. During this time, the mixed solution 15 was supplied from the aeration tank 12 and the ozone generator 23.
, An ozone-containing gas was supplied to the reactor 24 to ozone-treat the mixed solution, the ozone-treated mixed solution was returned to the aeration tank 12, and the mixed solution in the aeration tank was continuously ozone-treated.

The supply amount of ozone in the ozone treatment device 22 is 0.04 kg-O ₃ / kg-MLSS / day, and the circulation amount (l / l) of the mixed solution from the aeration tank 12 to the ozone treatment device 22 per unit time. h) is the amount of raw wastewater treated per unit time (l / h).
20%. As a result of performing the continuous operation of the activated sludge apparatus by the above method, the amount of membrane permeated water was 0.33 at the beginning of the treatment of raw wastewater.
m ³ / m ² / day, after 24 hours, 0.33 m ³ / m ² / day, the amount of excess sludge generated was 2.2 g, and the average MLSS was 5000 mg / l.

The average BOD of the raw wastewater during the continuous operation period
Is 206 mg / l and the average SS is 143 mg / l.
D was 2.2 mg / l and average SS was 0.1 mg / l. (Comparative Example 2) Using the apparatus shown in FIG.
The activated sludge apparatus was continuously operated under the same conditions as in Example 2 except that ozone treatment was not performed.

[0030] As a result, membrane permeation water amount, the process starts early original wastewater 0.33m ³ / m ² / day, after 24h lapse is at 0.10m ³ / m ² / day, the amount of excess sludge is 6.0 g, average MLSS was 4800 mg / l. In addition, the average BOD of raw wastewater during continuous operation is 2
The average BOD of the treated water is 03 mg / l and the average SS is 125 mg / l.
The average SS was 1.4 mg / l and the average SS was 0.1 mg / l.

[0031]

As described above in detail, according to the present invention, in the treatment of organic substance-containing wastewater by the membrane separation activated sludge method, the membrane separation treatment is performed while circulating the activated sludge with ozone. As a result, the adhesion and deposition of organic polymer substances and solids on the membrane of the membrane module can be significantly suppressed, and the clogging of the pores of the membrane by sludge particles can be suppressed, and the life of the membrane can be significantly extended. became.

Further, the amount of excess sludge generated can be reduced to 70% or less of the conventional method, and various problems associated with disposal of excess sludge, such as securing a final disposal site for sludge incineration ash, are greatly improved. You. That is, the present invention is a method for treating wastewater containing organic substances such as domestic wastewater such as urban sewage and settlement wastewater, livestock wastewater, processed fishery wastewater, and processed agricultural wastewater, which is much more efficient and economical than conventional treatment techniques. It can be realized by a method that is excellent in both the characteristics.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of an activated sludge apparatus of the present invention.

FIG. 2 is a configuration diagram showing an example of the activated sludge apparatus of the present invention.

FIG. 3 is a configuration diagram of a conventional activated sludge apparatus.

FIG. 4 is a configuration diagram of a conventional activated sludge apparatus.

[Explanation of symbols]

 11 Regulating tank 12 Aeration tank (biological reactor) 13 Blower 14 Aerator 15 Mixed solution (activated sludge) 16, 19 Membrane separator 17, 20 Membrane module 18, 21, 25 Pump 22 Ozonator 23 Ozone generator 24 Reactor

Claims (2)

[Claims] 1. An activated sludge method used for treating raw wastewater containing an organic substance, wherein the mixed solution containing a sludge-like reactant generated in an aeration tank is subjected to ozone treatment, and the ozone-treated mixed solution is treated. An activated sludge method characterized in that treated water is obtained by solid-liquid separation of a mixed solution by a membrane separation device. 2. An activated sludge apparatus for treating raw wastewater containing organic substances, said activated sludge apparatus comprising an aeration tank and a mixed solution containing sludge-like reactants generated in the aeration tank. An ozone treatment device for processing, a membrane separation device as solid-liquid separation means of the mixed solution in the aeration tank, and circulating the mixed solution in the aeration tank between the aeration tank and the ozone treatment device An activated sludge apparatus having circulation means.