JP6530188B2 - Waste water treatment apparatus and waste water treatment method - Google Patents

Description

  BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a technique of a wastewater treatment apparatus and wastewater treatment method for treating organic matter-containing wastewater.

  BACKGROUND ART In recent years, in an activated sludge method used as a treatment technology for organic matter-containing wastewater, a membrane separation activated sludge method has been developed and spread, in which solid-liquid separation of sludge and treated water is performed by a membrane instead of a sedimentation tank. In the normal activated sludge method, when the settling property of the sludge is deteriorated, solid-liquid separation in the sedimentation tank becomes insufficient, SS (Suspended Solids, suspended matter) flows out to the treated water, and the treated water quality is deteriorated. There's a problem. On the other hand, in the membrane separation activated sludge method, since solid-liquid separation is performed by a membrane, there is an advantage that clear treated water can be obtained regardless of the settling property of the sludge.

In addition, as an activated sludge method for treating organic matter-containing wastewater under a high load, a carrier method in which microorganisms are attached to a carrier added in a tank to treat wastewater is also spreading. BOD volume load in general activated sludge method, it is a 0.5~0.8kg ^{/ m} 3 ^/ d, to operate in use when 1.0kg ^{/ m} 3 ^/ d or more BOD volume load carrier method Is possible.

  In the technology combining biological treatment (hereinafter sometimes referred to as carrier method) using a carrier and membrane separation activated sludge treatment (hereinafter sometimes referred to as MBR treatment), high-speed treatment by the carrier method is possible. At the same time, it is possible to have two features that clear treated water can be obtained by MBR treatment.

For example, in Patent Document 1, in a waste water treatment apparatus combining a carrier method and MBR treatment, BOD volume load in the carrier method is operated at 1 kg / m ³ · day or more, and soluble BOD sludge load in MBR treatment is 0 It is disclosed to operate at 1 kg-BOD / kg-MLSS-day or less. And by making soluble BOD sludge load of MBR processing small like patent document 1, the increase rate of sludge and the self-digestion rate of sludge balance, and it becomes possible to reduce the generation amount of sludge.

Patent No. 4667583

  However, as a result of studies by the inventors, although it is possible to reduce the amount of sludge generated by reducing the soluble BOD sludge load of the MBR treatment, at the same time, the in-tank TOC component accompanying the autolysis of the sludge It has been found that the occurrence and accumulation of (membrane clogging substance) occurs, the TOC component adheres to the membrane used for MBR processing, and the membrane clogging becomes apt to occur.

  Therefore, an object of the present invention is to provide a waste water treatment apparatus and a waste water treatment method combining a carrier method and MBR treatment, which can suppress clogging of a membrane used for MBR treatment while suppressing an increase in the amount of generated sludge. A waste water treatment apparatus and a waste water treatment method are provided.

The waste water treatment apparatus of the present invention comprises a first biological treatment tank for biological treatment of organic matter-containing wastewater in the presence of a carrier, and a second biological treatment tank for biological treatment of the first treated water treated in the first biological treatment tank. And a membrane separation biological treatment unit having a membrane separation module for separating the second treated water treated in the second biological treatment tank into sludge and third treated water by a separation membrane, and the inside of the second biological treatment tank Sludge extraction means for extracting sludge, wherein the sludge extraction means has a soluble BOD sludge load of 0.05 kg-BOD / kg-MLSS / d or more in the second biological treatment tank and is 0.10 kg- Sludge in the second biological treatment tank so that the sludge retention time (SRT) in the second biological treatment tank is in a range of 10 to 15 days so as to be operated at less than BOD / kg-MLSS / d Pull out the sludge Serial without returning to the first biological treatment tank, a wastewater treatment apparatus for discharging into the membrane separation biological treatment unit outside.

Further, in the waste water treatment apparatus, the sludge withdrawal means, sludge concentration in the second biological treatment tank is such that the range of 3000~5000mg / L, pulling the sludge of the second biological treatment tank Is preferred.

In the waste water treatment method of the present invention, a first biological treatment step of biological treatment of organic matter-containing waste water in the presence of a carrier, and a second biological treatment step of biological treatment of the first treated water treated by the biological treatment means. And a membrane separation biological treatment step having a membrane separation step of separating the second treated water treated in the second biological treatment step into sludge and third treated water by a separation membrane, and produced in the second biological treatment step Removing sludge, and in the sludge extraction step, the soluble BOD sludge load in the second biological treatment step is 0.05 kg-BOD / kg-MLSS / d or more and 0.10 kg-BOD / as is operated at less than kg-MLSS / d, and the sludge residence time in the second biological treatment step (SRT) is generated in the to be in the range of 10 to 15 days the second biological treatment process Pull the mud, without returning the sludge to the first biological treatment process, a waste water treatment method for discharging into the membrane separation biological treatment step outside.

Further, in the wastewater treatment method, in the sludge withdrawal process, the so sludge concentration becomes range of 3000~5000mg / L in the second biological treatment process, pulling out the sludge generated in the second biological treatment process Is preferred.

  According to the present invention, in the waste water treatment apparatus and the waste water treatment method combining the carrier method and the MBR treatment, it is possible to suppress the clogging of the membrane used for the MBR treatment while suppressing the increase in the amount of generated sludge.

It is a schematic diagram which shows an example of a structure of the processing apparatus which concerns on this embodiment. It is a schematic diagram which shows another example of a structure of the waste-water-treatment apparatus which concerns on this embodiment. It is a schematic diagram which shows another example of a structure of the waste-water-treatment apparatus which concerns on this embodiment. It is a figure which shows transition of the membrane suction pressure of the membrane module of Example 1 and Comparative Examples 1-2. It is a figure which shows transition of the TOC density | concentration in the filtrate obtained by filtering the sludge in the 2nd biological treatment tank of Example 1 and Comparative Examples 1-2. FIG. 10 is a view showing the transition of the membrane suction pressure of the membrane module of Example 2. It is a figure which shows transition of TOC density | concentration in the filtrate obtained by filtering the sludge in the 2nd biological treatment tank of Example 2. FIG. It is a figure which shows transition of the membrane suction pressure of the membrane module of the comparative example 3. FIG. FIG. 16 is a view showing the transition of the membrane suction pressure of the membrane module of Example 3. It is a figure which shows transition of the TOC density | concentration in the filtrate obtained by filtering the sludge in the 2nd biological treatment tank of Example 3. FIG.

  Hereinafter, embodiments of the present invention will be described. In addition, this embodiment is an example which implements this invention, Comprising: This invention is not limited to this embodiment.

  FIG. 1: is a schematic diagram which shows an example of a structure of the waste-water-treatment apparatus which concerns on this embodiment. As shown in FIG. 1, the waste water treatment apparatus 1 comprises a separation membrane biological treatment unit having a waste water inflow line (10a, 10b), a first biological treatment tank 12, a second biological treatment tank 14 and a separation membrane module 16, treated water It comprises a sludge extraction device (sludge extraction means) and the like provided with a discharge line 18, a treated water discharge pump 20, a sludge discharge pump 22 and a sludge discharge line 24.

  A carrier 26 is charged into the first biological treatment tank 12 shown in FIG. Moreover, the 1st biological treatment tank 12 and the 2nd biological treatment tank 14 which are shown in FIG. 1 are equipped with the aeration apparatus which has a blower (28a, 28b) and an air inflow line (30a, 30b). The separation membrane module 16 shown in FIG. 1 is installed in the second biological treatment tank 14. Further, in the separation membrane module 16, a separation membrane (not shown) is provided.

  A drainage inlet line 10 a is connected to the drainage inlet of the first biological treatment tank 12. One end of the drainage inflow line 10 b is connected to the treated water outlet of the first biological treatment tank 12, and the other end is connected to the treated water inlet of the second biological treatment tank 14. A treated water discharge line 18 is connected to the discharge port of the separation membrane module 16 installed in the second biological treatment tank 14. A treated water discharge pump 20 is interposed in the treated water discharge line 18. In addition, an air inflow line (30a, 30b) is connected to the bottom of the first and second biological treatment tanks (12, 14). Blowers (28a, 28b) are interposed in the air inflow lines (30a, 30b). Moreover, the sludge discharge line 24 is connected to the sludge discharge port of a 2nd biological treatment apparatus. A sludge discharge pump 22 is interposed in the sludge discharge line 24.

  The organic substance-containing wastewater to be treated in the present embodiment is not particularly limited as long as it is generally a wastewater containing bioprocessable organic substances, and, for example, sewage, electronic industry wastewater, chemical factory wastewater, food factory wastewater Factory drainage etc. The concentration of the organic substance in the waste water to be treated is not particularly limited, but it is preferably in the range of 300 to 2000 mg / L as the BOD concentration from the viewpoint of the biological treatment rate.

  Below, operation | movement of the waste water treatment apparatus 1 of this embodiment is demonstrated.

  The organic matter-containing drainage is introduced into the first biological treatment tank 12 through the drainage inflow line 10 a. Also, the blower 28 a is operated, and air is supplied into the first biological treatment tank 12 through the air inflow line 30 a. In the biological treatment tank 12, under aerobic conditions, the organic matter (soluble BOD) in the waste water is oxidatively decomposed by the dispersible bacteria etc. attached to the carrier 26 (bacterial cells, carbon dioxide etc.) Change). The first treated water treated in the first biological treatment tank 12 is introduced into the second biological treatment tank 14 through the drainage inflow line 10 b. Further, the blower 28 b is operated, and air is supplied into the second biological treatment tank 14 through the air inflow line 30 b. Then, in the second biological treatment tank 14, the organic matter remaining in the first treated water is oxidatively decomposed by the dispersible bacteria and the like under aerobic conditions. Next, the treated water discharge pump 20 is operated to feed the second treated water treated in the second biological treatment tank 14 to the separation membrane module 16. The second treated water is solid-liquid separated into third treated water and sludge by the separation membrane in the separation membrane module 16. The third treated water is discharged from the treated water discharge line 18 to the outside of the system. Further, the sludge discharge pump 22 is operated, and the sludge in the second biological treatment tank 14 is drawn out from the sludge discharge line 24. The sludge extracted from the second biological treatment tank 14 is discharged out of the system of the membrane separated biological treatment unit without being returned to the first biological treatment tank 12, and dewatering and drying treatment and the like are performed.

  In the present embodiment, the soluble BOD sludge load (hereinafter simply referred to as BOD sludge load) of the second biological treatment tank 14 is 0.05 kg-BOD / kg-MLSS / d or more, preferably 0.05 kg-BOD / kg. -MLSS / d or more and less than 0.10 kg-BOD / kg-MLSS / d, more preferably 0.05 kg-BOD / kg-MLSS / d or more and 0.07 kg-BOD / kg-MLSS / d The sludge extraction device pulls out the sludge in the second biological treatment tank 14 so as to be operated at less than. When a part or all of the sludge extracted by the sludge extraction device is returned to the first biological treatment tank 12, the sludge in the extracted sludge and the TOC component that causes the film clogging will be returned to the second biological treatment tank again. In the present embodiment, it is necessary to discharge the extracted sludge out of the system of the membrane separation biological treatment unit without returning it to the first biological treatment tank 12 because it can not be operated with BOD sludge load.

  The inventors of the present invention operate the BOD sludge load of the second biological treatment tank 14 at less than 0.05 kg-BOD / kg-MLSS / d, so that the amount of sludge generated in the second biological treatment tank 14 is low. It was found that the self-digestion of sludge was promoted and TOC components were generated in the tank. It has also been found that the TOC component accumulates without being processed in the second biological treatment tank 14 and causes clogging of the separation membrane in the separation membrane module 16. Therefore, as in the present embodiment, the sludge in the second biological treatment tank 14 is drawn out so that the BOD sludge load of the second biological treatment tank 14 is operated at 0.05 kg-BOD / kg-MLSS / d or more. Thus, it is possible to suppress the self-digestion of sludge while suppressing the amount of generated sludge. As a result, generation and accumulation of TOC components in the tank are suppressed, and clogging of the separation membrane is suppressed. In particular, the BOD sludge load of the second biological treatment tank 14 is 0.05 kg-BOD / kg-MLSS / d or more and 0 or less by operating in a range of less than 0.10 kg-BOD / kg-MLSS / d. . Compared with the case of operating at 10 kg-BOD / kg-MLSS / d or more, the amount of sludge generation is further suppressed, and by operating at 0.05-0.10 kg-BOD / kg-MLSS / d As compared with the case of operating at less than 0.05 kg-BOD / kg-MLSS / d, the generation amount of TOC component in the tank is further suppressed.

  Generally, if the BOD concentration in the first treated water introduced into the second biological treatment tank 14 is constant, the amount of sludge in the second biological treatment tank 14 increases with the biological treatment, so the second The BOD sludge load of the biological treatment tank 14 tends to decrease. Therefore, as in the present embodiment, the sludge is continuously or intermittently withdrawn from the second biological treatment tank 14 by the sludge extraction device, and the BOD sludge load of the second biological treatment tank 14 is 0.05 kg-BOD / kg. Need to be adjusted to operate at MLSS / d or higher. In addition, it is desirable to install a raw water adjustment tank in the front | former stage of the 1st biological treatment tank 12, adjust the BOD density | concentration in waste water to predetermined value, and then liquid-feed to the waste water inflow line 10a. This makes it possible to suppress the fluctuation of the BOD concentration in the first treated water introduced into the second biological treatment tank 14.

  In the present embodiment, for example, the BOD sludge load may be periodically measured (see the example for the calculation method), and the amount of sludge withdrawn from the sludge extraction device may be adjusted based on the value, but usually [2] Since the BOD concentration of the first treated water flowing into the biological treatment tank 14 hardly changes, by pulling out the sludge from the second biological treatment tank 14 so that the sludge residence time and the sludge concentration become the ranges shown below, the BOD It is possible to operate with a sludge load of 0.05 kg-BOD / kg-MLSS / d or more.

  In the present embodiment, the sludge residence time (SRT) in the second biological treatment tank 14 is, for example, in the range of 5 days to 30 days, from the viewpoint of setting the BOD sludge load to 0.05 kg-BOD / kg-MLSS / d or more. The sludge is extracted from the inside of the second biological treatment tank 14 so as to be preferably in the range of 5 days to 20 days, more preferably in the range of 10 days to 15 days. The removal may be always a fixed amount, or may be a set SRT every day or several days using a timer or the like. See the examples for how to calculate the sludge retention time.

  Moreover, in the present embodiment, the sludge concentration (MLSS) in the second biological treatment tank 14 is, for example, 10000 mg / L or less, preferably, from the viewpoint of setting the BOD sludge load to 0.05 kg-BOD / kg-MLSS / d or more. The sludge is extracted from the inside of the second biological treatment tank 14 so as to be in the range of 3000 mg / L to 5000 mg / L. The sludge concentration is measured, for example, by a sewage test method, activated sludge floating substance measurement method (centrifugal separation method, glass fiber filter method, etc.).

In this embodiment, in the technology of combination of carrier method (first biological treatment tank) and MBR (separation membrane biological treatment unit), it becomes possible to reduce the amount of sludge generated in MBR and to suppress membrane clogging. Therefore, it becomes possible to operate at an overall BOD volume load of 1.5 kg / m ³ / d or more, preferably 1.0 kg / m ³ / d or more. The overall BOD volume load is the amount of BOD that flows into one day relative to the sum of the tank volumes of the first biological treatment tank 12 and the second biological treatment tank 14. It becomes possible to process organic matter. See the examples for how to calculate the overall BOD volume load.

  The pH of the first biological treatment tank 12 and the second biological treatment tank 14 is not particularly limited as long as it is a range adapted to general biological treatment, but for example, the range of 6 to 9 is preferable, and 6.5 The range of -7.5 is more preferable. The pH adjustment of the first biological treatment tank 12 and the second biological treatment tank 14 is performed by adding a pH adjuster to each tank. Examples of pH adjusters include acid agents such as hydrochloric acid, and alkali agents such as sodium hydroxide.

  The dissolved oxygen (DO) in the first biological treatment tank 12 and the second biological treatment tank 14 is not particularly limited as long as it is the amount of oxygen necessary for general biological treatment, for example, 0.5 mg / L It is preferably at least 1 mg, more preferably at least 1 mg / L.

  The water temperature of the first biological treatment tank 12 and the second biological treatment tank 14 is not particularly limited as long as it is a range applicable to general biological treatment, but for example, a range of 15 to 35 ° C. is preferable, 20 The range of -30 ° C is more preferable.

  It is preferable to add a nutrient to the first biological treatment tank 12 and the second biological treatment tank 14. The nutrient is not particularly limited as long as it maintains the decomposition activity of the microorganism well, and examples thereof include nitrogen sources, phosphorus sources, and other inorganic salts.

  The carrier 26 to be charged into the first biological treatment tank 12 is not particularly limited, and various known carriers may be used. In the present embodiment, either a fluid type in which the carrier 26 flows in the first biological treatment tank 12 or a fixed type in which a cartridge or the like filled with the carrier 26 is installed in the first biological treatment tank 12 may be used. Further, the shape and the material of the carrier 26 are not limited, but the porous carrier 26 is desirable from the viewpoint of the adhesion of the microorganism, and specifically, the porous polyurethane sponge 26 made of polyurethane and the like can be mentioned. .

  Although the membrane separation biological processing unit of this embodiment exemplifies an in-tank type device in which the separation membrane module 16 is installed in the second biological treatment tank 14, the present invention is not limited thereto. 2) The apparatus of the tank outside type installed out of the biological treatment tank 14 may be sufficient. Among these, it is preferable to use an in-tank type membrane separation biological treatment unit from the viewpoint of the installation area of the device and the operation power. As the separation membrane provided in the separation membrane module 16, although conventionally known ones and the like are used, a hollow fiber membrane element is preferable in that the installation area can be reduced. Also, the film material is not particularly limited, but a polyvinylidene fluoride porous film is desirable from the viewpoint of excellent strength and chemical resistance.

  In the present embodiment, an example has been described in which an aeration apparatus is installed in the first biological treatment tank 12 and the second biological treatment tank 14 and biological treatment is performed under aerobic conditions, but the present invention is not limited thereto. Biological treatment may be performed under the conditions. In this case, it is desirable to install a stirrer in the first biological treatment tank 12 and the second biological treatment tank 14 instead of the aeration apparatus.

  The sludge extracting apparatus of the present embodiment is limited to the apparatus configuration including the sludge discharge pump 22 and the sludge discharge line 24 shown in FIG. 1 as long as the apparatus configuration can extract sludge from the second biological treatment tank 14 Instead, for example, an on-off valve may be installed in the sludge discharge line 24 and the on-off valve may be opened to allow the sludge to naturally flow down from the sludge discharge line 24.

  FIG. 2 is a schematic view showing another example of the configuration of the wastewater treatment device according to the present embodiment. In the waste water treatment apparatus 2 shown in FIG. 2, about the structure similar to the waste water treatment apparatus 1 shown in FIG. 1, the same code | symbol is attached | subjected and the description is abbreviate | omitted. The waste water treatment apparatus 2 shown in FIG. 2 is a separation membrane biological treatment unit having a waste water inflow line (10a, 10b, 10c), a first biological treatment tank 12, a second biological treatment tank (14a, 14b) and a separation membrane module 16. The system includes a sludge extraction device having a treated water discharge line 18, a treated water discharge pump 20, a sludge discharge pump 22 and a sludge discharge line 24, a sludge return device having a sludge return pump 32 and a sludge return line 34, and the like.

  A carrier 26 is charged into the first biological treatment tank 12 shown in FIG. Further, the first biological treatment tank 12 and the second biological treatment tank (14a, 14b) shown in FIG. 2 are provided with an aeration device having blowers (28a, 28b, 28c) and air inflow lines (30a, 30b, 30c). ing.

  In the present embodiment, the second biological treatment tank is composed of two tanks (14a, 14b), and the separation membrane module 16 is installed in the second biological treatment tank 14b in the latter stage. The second biological treatment tank may be composed of three or more tanks. Moreover, the separation membrane module 16 may be installed in each tank which comprises a 2nd biological treatment tank, and may be installed in any one of each tank which comprises a 2nd biological treatment tank. Further, in the separation membrane module 16, a separation membrane (not shown) is provided.

  A drainage inlet line 10 a is connected to the drainage inlet of the first biological treatment tank 12. One end of the drainage inflow line 10b is connected to the treated water outlet of the first biological treatment tank 12, and the other end is connected to the treated water inlet of the second biological treatment tank 14a. Further, one end of the drainage inflow line 10c is connected to the treated water outlet of the second biological treatment tank 14a, and the other end is connected to the treated water inlet of the second biological treatment tank 14b. A treated water discharge line 18 is connected to the discharge port of the separation membrane module 16 installed in the second biological treatment tank 14 b. A treated water discharge pump 20 is interposed in the treated water discharge line 18. Further, an air inflow line (30a, 30b, 30c) is connected to the bottom of the first and second biological treatment tanks (12, 14a, 14b). Blowers (28a, 28b, 28c) are interposed in the air inflow lines (30a, 30b, 30c). Moreover, the sludge discharge line 24 is connected to the sludge discharge port of the 2nd biological treatment tank 14b. A sludge discharge pump 22 is interposed in the sludge discharge line 24. Further, one end of the sludge return line 34 is connected to the sludge return outlet of the second biological treatment tank 14 b, and the other end is connected to the sludge return inlet of the second biological treatment tank 14 a. A sludge return pump 32 is interposed in the sludge return line 34.

  The organic matter-containing drainage is introduced into the first biological treatment tank 12 through the drainage inflow line 10 a. In the first biological treatment tank 12, the organic matter (soluble BOD) in the waste water is oxidized and decomposed under aerobic conditions by the dispersible bacteria etc. attached to the carrier 26 (bacterial bacteria, carbon dioxide, etc. Change)). The first treated water treated in the first biological treatment tank 12 passes through the drainage inflow line (10b, 10c) and is introduced into the second biological treatment tank (14a, 14b). In the second biological treatment tank (14a, 14b), the organic matter remaining in the first treated water is oxidatively decomposed by the dispersible bacteria and the like under aerobic conditions. Next, the treated water discharge pump 20 is operated to pass the second treated water treated in the second biological treatment tank 14 b to the separation membrane module 16. The second treated water is solid-liquid separated into third treated water and sludge by the separation membrane in the separation membrane module 16. The third treated water is discharged from the treated water discharge line 18 to the outside of the system. In addition, the sludge discharge pump 22 is operated, and the sludge in the second biological treatment tank 14 b is withdrawn from the sludge discharge line 24 and discharged out of the system without being returned to the first biological treatment tank 12. Further, in the present embodiment, the sludge return pump 32 is operated to equalize the sludge concentration of the second biological treatment tank (14a, 14b), and the sludge in the second biological treatment tank 14b in the latter stage is sludged. It is desirable to return to the second biological treatment tank 14 a in the previous stage through the return line 34. Although the amount of sludge returned is not particularly limited, it is three times or more the amount of water passing through the separation membrane module 16 in terms of equalizing the sludge concentration in the second biological treatment tank (14a, 14b), etc. It is desirable to do.

  When the second biological treatment tank is composed of a plurality of tanks (14a, 14b) as in the present embodiment, the BOD sludge load of each tank needs to be operated at 0.05 kg-BOD / kg-MLSS / d or more. is there. In the present embodiment, since the sludge concentration in the second biological treatment tank 14a and the second biological treatment tank 14b is equalized by the sludge return device, the BOD sludge load of the second biological treatment tank 14b in the latter stage is 0.05 kg- If the sludge in the second biological treatment tank 14b is withdrawn by the sludge extraction device so that the BOD / kg-MLSS / d or more is operated, the BOD sludge load of the second biological treatment tank 14a in the previous stage is 0.05 kg. -It will be operated at BOD / kg-MLSS / d or more. In addition, the sludge extraction device which has the sludge discharge pump 22 and the sludge discharge line 24 is installed also in the second biological treatment tank 14a of the former stage, and the BOD sludge load of the second biological treatment tank 14a is 0.05 kg-BOD / kg. -The sludge in the second biological treatment tank 14a may be withdrawn by a sludge extraction device so as to be operated at -MLSS / d or more.

  FIG. 3 is a schematic view showing another example of the configuration of the wastewater treatment device according to the present embodiment. In the waste water treatment apparatus 3 shown in FIG. 3, about the structure similar to the waste water treatment apparatus 1 shown in FIG. 1, the same code | symbol is attached | subjected and the description is abbreviate | omitted. The waste water treatment apparatus 3 shown in FIG. 3 includes a separation membrane biological treatment unit having a waste water inflow line (10a, 10b), a first biological treatment tank 12, a second biological treatment tank 14, and a separation membrane module 16, a treated water discharge line 18 A sludge extraction device having a treated water discharge pump 20, a sludge discharge pump 22, and a sludge discharge line 24, and a drainage bypass line 36 and the like. A carrier 26 is charged into the first biological treatment tank 12 shown in FIG. Moreover, the 1st biological treatment tank 12 and the 2nd biological treatment tank 14 which are shown in FIG. 3 are equipped with the aeration apparatus which has a blower (28a, 28b) and an air inflow line (30a, 30b). The separation membrane module 16 is installed in the second biological treatment tank 14. Further, in the separation membrane module 16, a separation membrane (not shown) is provided.

  In the waste water treatment apparatus 3 shown in FIG. 3, one end of the waste water bypass line 36 is connected to the waste water inflow line 10 a, and the other end is connected to the second biological treatment tank 14. The other form is the same as that of the waste water treatment apparatus 1 of FIG.

  In the waste water treatment apparatus 3 shown in FIG. 3, for example, when the BOD concentration in the first treated water flowing into the second biological treatment tank 14 decreases, the second biological treatment is performed by suppressing the amount of sludge drawn by the sludge drawing device. Although it is possible to operate so that the BOD sludge load in the tank 14 is 0.05 kg-BOD / kg-MLSS / d or more, furthermore, organic matter-containing wastewater from the wastewater bypass line 36 is treated as the second biological treatment tank 14 The BOD sludge load in the second biological treatment tank 14 is 0.05 kg-BOD / kg-MLSS without changing the sludge removal amount by directly supplying to the BOD and increasing the BOD concentration in the second biological treatment tank 14 It becomes possible to make it / d or more.

  In this embodiment, although the 2nd biological treatment tank 14 is made into a single tank, as shown in FIG. 2, you may be comprised from a several tank. In this case, the drainage bypass line 36 is connected to the second biological treatment tanks from the drainage inflow line 10a. Although the inflow of drainage through the drainage bypass line 36 is appropriately set by the BOD sludge load of the second biological treatment tank 14, the range of 10% to 30% of the inflow of drainage through the drainage inflow line 10a It is desirable to

  Hereinafter, the present invention will be described in more detail by way of examples and comparative examples, but the present invention is not limited to the following examples.

Example 1
In Example 1, the waste water treatment apparatus shown in FIG. 1 was used. In Example 1, a first biological treatment tank having a volume of 12 L and a second biological treatment tank having a volume of 26 L were prepared. In the first biological treatment tank, 2.4 L of a sponge carrier was charged. A PVDF hollow fiber membrane was used as a separation membrane provided in the separation membrane module. The organic substance-containing wastewater (raw water) to be treated contains an artificial substrate with a BOD concentration of 1000 mg / L, and the water flow rate was 60 L / d. In Example 1, the sludge is extracted so that the sludge concentration of the second biological treatment tank is in the range of 3000 to 5000 mg / L, and the sludge retention time of the second biological treatment tank is in the range of 5 to 10 days, and the second biological treatment is performed. The tank was operated at a BOD sludge load of 0.05 kg-BOD / kg-MLSS / d or more and less than 0.09 kg-BOD / kg-MLSS / d.

<Operating conditions of wastewater treatment equipment>
Total BOD volume load: 1.5 kg / m ³ / d
Filtration Flux: 0.4m / d
Sludge concentration in the second biological treatment tank (MLSS of MBR): 3000 to 5000 mg / L
Sludge retention time of second biological treatment tank (SRT of MBR): 5 to 10 days BOD sludge load of second biological treatment tank (BOD sludge load of MBR): 0.05 kg-BOD / kg-MLSS / d or more-0 .09 kg-BOD / kg-MLSS / d or less

The total BOD volume load is the amount of BOD flowing into one day with respect to the total tank volume of the first biological treatment tank and the second biological treatment tank, and is calculated as follows.
Overall BOD volume load = BOD concentration × influent water amount (or treated water amount) / total tank volume BOD concentration × influent water amount is the BOD inflow amount.

The BOD sludge load of the MBR is the amount of BOD flowing into the sludge in the second biological treatment tank (MBR tank) on one day, and is calculated as follows.
BOD sludge load of MBR = (BOD concentration of inflowing water to MBR tank × inflowing water volume (or treated water volume)) / (sludge concentration (MLSS) × tank volume)
The sludge concentration (MLSS) × tank volume is the amount of sludge in the tank.

SRT is the time until the sludge in the tank is discharged out of the system as excess sludge (extracted sludge), and is calculated as follows.
SRT = (in-tank sludge concentration × tank volume) / ((extracted sludge concentration × extracted water amount) + (SS × treated water amount in treated water))
Here, since sludge is removed by membrane separation in the second biological treatment tank, SS in the treated water is usually zero, so the sludge retention time is as follows.
SRT of MBR = (Sludge concentration in tank × tank volume) / (extracted sludge concentration × withdrawn amount)

The filtration flux is the amount of treated water per unit membrane area of the separation membrane, and is calculated as follows.
Filtration Flux = flow rate of treated water / membrane area of separation membrane

(Comparative example 1)
In Comparative Example 1, the sludge is extracted so that the sludge concentration (MLSS of MBR) of the second biological treatment tank is 10000 mg / L, and the sludge retention time (SRT of MBR) of the second biological treatment tank is 30 days, The BOD sludge load (BOD sludge load of MBR) of the processing apparatus was operated at 0.01 kg-BOD / kg-MLSS / d or less. The other conditions were the same as in Example 1.

(Comparative example 2)
In Comparative Example 2, the waste water treatment apparatus shown in FIG. 3 was used. The volumes of the first biological treatment tank and the second biological treatment tank used in Comparative Example 2 were the same as in Example 1. In Comparative Example 2, raw water with a flow rate of 5 to 8 L / d was directly supplied from the drainage bypass line to the second biological treatment tank. In addition, the sludge is extracted so that the sludge concentration (MLSS of MBR) in the second biological treatment tank is 10000 mg / L and the sludge retention time (SRT in MBR) of the second biological treatment tank is 30 days, and the second biological treatment device BOD sludge load (BOD sludge load of MBR) was made into the range of 0.03-0.04 kg-BOD / kg-MLSS / d. The other conditions were the same as in Example 1.

  The operating conditions of Example 1 and Comparative Examples 1 and 2 are summarized in Table 1.

The treated water quality and sludge conversion rate (g-MLSS / g-BOD) of Example 1 and Comparative Examples 1 and 2 are summarized in Table 2. The sludge conversion rate is the amount of sludge generated in the second biological treatment tank relative to the BOD treatment amount, and is expressed as follows. The same applies to all the following examples and comparative examples.
Sludge conversion rate = generated sludge amount of second biological treatment tank / BOD treated amount generated sludge amount = ((sludge concentration of the second biological treatment tank after a predetermined period has elapsed-sludge concentration of the second biological treatment tank at the initial stage) x second 2 tank volume of biological treatment tank) + (extracted sludge concentration × amount of extracted water)
BOD treatment amount = (raw water BOD concentration-treated water BOD concentration discharged from the second biological treatment) x treatment flow rate where the sludge of the second biological treatment tank after a predetermined period of Example 1 and Comparative Examples 1 and 2 has elapsed The concentration is the sludge concentration of the second biological treatment tank on the 12th day.

  FIG. 4: is a figure which shows transition of the membrane suction pressure of the membrane module of Example 1 and Comparative Examples 1-2. The membrane suction pressure of the membrane module is a value measured by a pressure gauge (Model GC67 manufactured by Nagano Keiki Co., Ltd.) installed in the treated water discharge line.

  Moreover, the sludge in the 2nd biological treatment tank of Example 1 and Comparative Examples 1-2 was filtered with a 5 C filter paper, and the TOC density | concentration in the obtained filtrate was measured.

  FIG. 5: is a figure which shows transition of the TOC density | concentration in the filtrate obtained by filtering the sludge in the 2nd biological treatment tank of Example 1 and Comparative Examples 1-2. The operating days on the horizontal axis of FIG. 5 represent the operating days of the apparatus. The TOC concentration was determined by measuring all the following examples and comparative examples in the same manner as described above.

  In Example 1, as understood from Table 2, the treated water BOD was less than 10 mg / L, the treated water TOC was 15 mg / L, and the sludge conversion rate was 0.212 (g-MLSS / g-BOD). Further, in Example 1, as can be seen from FIG. 4, no increase in the membrane suction pressure was observed during 12 days of operation days, and stable operation could be performed. Furthermore, in Example 1, as can be seen from FIG. 5, the TOC in the filtrate obtained by filtering the sludge in the second biological treatment tank was stable at about 100 mg / L for 12 days of operation days .

  In Comparative Example 1, as seen from Table 2, the treated water BOD was less than 10 mg / L, the treated water TOC was 17 mg / L, and the sludge conversion rate was 0.207, which were similar to those of Example 1. However, in Comparative Example 1, as can be seen from FIG. 4, the film suction pressure increased during 12 days of operation days, and stable operation could not be performed. Furthermore, in Comparative Example 1, as can be seen from FIG. 5, the TOC in the filtrate obtained by filtering the sludge in the second biological treatment tank rises during the operation days of 12 days, to about 300 mg / L. Reached. In addition, 300 mL of sludge in the second biological treatment tank on the 4th day of operation is collected in a beaker, aerated with air stone at 2 L / min, immediately after aeration, 1 hour after aeration start, 3 days after aeration start The sludge was filtered through 5 C filter paper, and the TOC concentration in the filtrate obtained was measured. The TOC concentration immediately after the start of aeration was 151 mg / L. The TOC concentration one hour after the start of aeration was 150 mg / L, and there was no change from the TOC concentration immediately after the start of aeration, but the TOC concentration three days after was 191 mg / L, which was higher than the TOC concentration immediately after the start of aeration. It was From this, it was found that the TOC component generated once in the second biological treatment tank is accumulated in the second biological treatment tank without being biodegradable.

  Also in Comparative Example 2, as can be seen from Table 2, the treated water quality and the sludge conversion rate were the same as in Example 1. However, as can be seen from FIG. 4, the membrane suction pressure increased during 12 days of operation days, and stable operation could not be performed. Furthermore, in Comparative Example 2, as can be seen from FIG. 5, TOC in the filtrate obtained by filtering the sludge in the second biological treatment tank rises during the operation days of 12 days, to about 300 mg / L. Reached.

  As described above, the sludge conversion rate is suppressed to a low level in all of Example 1 and Comparative Examples 1 and 2 (the increase in the amount of sludge generation is suppressed). The second biological treatment apparatus as in Comparative Examples 1 and 2 by discharging sludge from the treatment tank and operating the BOD sludge load of the second biological treatment apparatus at 0.05 kg-BOD / kg-MLSS / d or more. The clogging of the separation membrane was able to be suppressed as compared with the case where the BOD sludge load (BOD sludge load of MBR) is less than 0.05 kg-BOD / kg-MLSS / d. This is because by operating the BOD sludge load of the second biological treatment apparatus at 0.05 kg-BOD / kg-MLSS / d or more, accumulation of TOC components in the second biological treatment tank is suppressed. It is considered that the amount of TOC component adhering to the separation membrane decreases, and the occurrence of clogging of the membrane is suppressed.

(Example 2)
In Example 2, the waste water treatment apparatus shown in FIG. 1 was used. In Example 2, a first biological treatment tank having a volume of 0.9 L and a second biological treatment tank having a volume of 1.5 L were prepared. In the first biological treatment tank, 0.1 L of a sponge carrier was charged. A PVDF hollow fiber membrane was used as a separation membrane provided in the separation membrane module. The organic matter-containing wastewater to be treated contains an artificial substrate with a BOD concentration of 120 mg / L, and the water flow rate was 30 L / d. In Example 2, the sludge is extracted so that the sludge concentration in the second biological treatment tank is 5000 mg / L and the sludge residence time in the second biological treatment tank is 10 days, and the BOD sludge load in the second biological treatment tank Was operated in the range of 0.09 kg-BOD / kg-MLSS / d or more and less than 0.10 kg-BOD / kg-MLSS / d.

<Operating conditions of wastewater treatment equipment>
Total BOD volume load: 1.5 kg / m ³ / d
Filtration Flux: 0.5m / d
Sludge concentration in second biological treatment tank (MLSS in MBR): 5000 mg / L
Sludge retention time of second biological treatment tank (SRT of MBR): 10 days BOD sludge load of second biological treatment tank (BOD sludge load of MBR): 0.09 kg-BOD / kg-MLSS / d or more-0.10 kg -Less than BOD / kg-MLSS / d

  The operating conditions of Example 2 are summarized in Table 3.

  Table 4 summarizes the treated water quality and sludge conversion rate (g-MLSS / g-BOD) of Example 2.

  FIG. 6 is a diagram showing the transition of the membrane suction pressure of the membrane module of Example 2. Moreover, FIG. 7 is a figure which shows transition of TOC density | concentration in the filtrate obtained by filtering the sludge in the 2nd biological treatment tank of Example 2. As shown in FIG.

  In Example 2, as understood from Table 4, the treated water BOD was less than 5 mg / L, the treated water TOC was 2 mg / L, and the sludge conversion rate was 0.186 (g-MLSS / g-BOD). Further, in Example 2, as can be seen from FIG. 6, no increase in the membrane suction pressure was observed during 20 days of operation days, and stable operation could be performed. Furthermore, in Example 2, as can be seen from FIG. 7, the TOC in the filtrate obtained by filtering the sludge in the second biological treatment tank was stable at about 20 mg / L for 20 days of operation days .

  In Comparative Examples 3 and 4 below, the BOD volume load, MLSS, and SRT of the second biological treatment tank were changed, and the influence of the amount of sludge generated in the second biological treatment tank was examined.

(Comparative example 3)
In the comparative example 3, it tested using the waste-water-treatment apparatus comprised only from a 2nd biological treatment tank. In Comparative Example 3, only the second biological treatment tank with a volume of 50 L was prepared. A PVDF hollow fiber membrane was used as a separation membrane provided in the separation membrane module. The organic matter-containing wastewater to be treated contains an artificial substrate having a BOD concentration of 1000 mg / L, and the water flow rate was 60 L / d. In Comparative Example 3, the sludge is extracted so that the sludge concentration of the second biological treatment tank is 10000 mg / L and the sludge retention time of the second biological treatment tank is 30 days, and the BOD sludge load of the second biological treatment tank is 0. It was operated at 12 kg-BOD / kg-MLSS / d or more.

<Operating conditions of wastewater treatment equipment>
Total BOD volume load (2nd biological treatment tank BOD volume load): 1.2 kg / m ³ / d
Filtration Flux: 0.4m / d
Sludge concentration in the second biological treatment tank (MLSS in MBR): 10000 mg / L
Sludge retention time (SBR of MBR) of the second biological treatment tank: 30 days BOD sludge load of the second biological treatment tank (BOD sludge load of the MBR): 0.12 kg-BOD / kg-MLSS / d or more

  Table 5 summarizes the operating conditions of Comparative Example 3.

  Table 6 summarizes the treated water quality and the sludge conversion rate (g-MLSS / g-BOD) of Comparative Example 3.

  FIG. 8 is a diagram showing the transition of the membrane suction pressure of the membrane module of Comparative Example 3.

  In Comparative Example 3, as seen from Table 6, the treated water BOD was less than 10 mg / L, and the treated water TOC was 18 mg / L. However, the sludge conversion rate was 0.394 (g-MLSS / g-BOD), and the sludge conversion rate was high compared to Example 1. This is considered to be because the amount of sludge generated in the second biological treatment tank was increased by operating at a high BOD sludge load as compared with Example 1. However, in Comparative Example 3, as can be seen from FIG. 8, the membrane suction pressure did not increase for 12 days of operation days, and stable operation could be performed. It is considered that this is because the operation with a high BOD sludge load as in Comparative Example 3 suppresses the generation of the TOC component accompanying the autolysis of the sludge in the second biological treatment tank.

(Example 3)
In Example 3, the waste water treatment apparatus shown in FIG. 3 was used. In Example 3, a first biological treatment tank having a volume of 12 L and a second biological treatment tank having a volume of 26 L were prepared. In the first biological treatment tank, 2.4 L of a sponge carrier was charged. A PVDF hollow fiber membrane was used as a separation membrane provided in the separation membrane module. The organic matter-containing wastewater to be treated contains an artificial substrate having a BOD concentration of 1000 mg / L, and the water flow rate was 60 L / d. In Example 3, waste water with a flow rate of 8 to 10 L / d was supplied directly from the waste water bypass line to the second biological treatment tank. Then, in Example 3, the sludge is extracted so that the sludge concentration of the second biological treatment tank is 9000 mg / L and the sludge retention time of the second biological treatment tank is 30 days, and the BOD sludge load of the second biological treatment tank is It was operated at 0.06 kg-BOD / kg-MLSS / d.

<Operating conditions of wastewater treatment equipment>
Total BOD volume load: 1.5 kg / m ³ / d
Filtration Flux: 0.4m / d
Sludge concentration in the second biological treatment tank (MLSS in MBR): 9000 mg / L
Sludge retention time of second biological treatment tank (SBR of MBR): 30 days BOD sludge load of second biological treatment tank (BOD sludge load of MBR): 0.06 kg-BOD / kg-MLSS / d

  The operating conditions of Example 3 are summarized in Table 7.

  Table 8 summarizes the treated water quality and sludge conversion rate (g-MLSS / g-BOD) of Example 3.

  FIG. 9 is a diagram showing the transition of the membrane suction pressure of the membrane module of Example 3. Moreover, FIG. 10 is a figure which shows transition of TOC density | concentration in the filtrate obtained by filtering the sludge in the 2nd biological treatment tank of Example 3. FIG.

  In Example 3, as shown in Table 8, the treated water BOD was less than 10 mg / L, the treated water TOC was 17 mg / L, and the sludge conversion rate was 0.207 (g-MLSS / g-BOD). Further, in Example 3, as can be seen from FIG. 9, no increase in the membrane suction pressure was observed for 5 days of operation days, and stable operation could be performed. Furthermore, in Example 3, as can be seen from FIG. 10, the TOC in the filtrate obtained by filtering the sludge in the second biological treatment tank was stable at about 120 mg / L for 5 days of operation days . However, in Example 3 in which SRT and MLSS were higher than Example 1, both the increase in membrane suction pressure and the TOC in the filtrate were higher. Further, considering the result of Comparative Example 3 in which the sludge conversion rate is increased, the BOD sludge load is in the range of 0.05 to 0.1 in terms of suppression of clogging of separation membrane and reduction of sludge generation amount, and It is preferable to make SRT into the range of 10-15, and to make MLSS into the range of 3000-5000.

  1 to 3 Waste water treatment apparatus, 10a, 10b, 10c Waste water inflow line, 12 first biological treatment tank, 14, 14a, 14b second biological treatment tank, 16 separation membrane modules, 18 treated water discharge line, 20 treated water discharge pump 22, 22 sludge discharge pumps, 24 sludge discharge lines, 26 carriers, 28a, 28b blowers, 30a, 30b air inflow lines, 32 sludge return pumps, 34 sludge return lines, 36 drainage bypass lines.

Claims (4)

A first biological treatment tank for biological treatment of organic matter-containing wastewater in the presence of a carrier;
A second biological treatment tank for biological treatment of the first treated water treated in the first biological treatment tank, and a second treated water treated in the second biological treatment tank with a separation membrane using sludge and third treated water A membrane separation biological processing unit having a membrane separation module for separating into
Sludge extraction means for extracting the sludge in the second biological treatment tank;
The sludge extracting means is operated at a soluble BOD sludge load of 0.05 kg-BOD / kg-MLSS / d or more and less than 0.10 kg-BOD / kg-MLSS / d in the second biological treatment tank. And the sludge in the second biological treatment tank is extracted so that the sludge retention time (SRT) in the second biological treatment tank is in the range of 10 to 15 days, and the sludge is subjected to the first biological treatment The waste water treatment apparatus characterized in that the waste water is discharged to the outside of the membrane separation biological treatment unit without being returned to the tank. The sludge withdrawal means, as sludge concentration in the second biological treatment tank is range of 3000~5000mg / L, according to claim 1, wherein the withdrawal of the sludge of the second biological treatment tank Waste water treatment equipment. A first biological treatment step of biological treatment of organic matter-containing wastewater in the presence of a carrier;
A second biological treatment step of biological treatment of the first treated water treated by the biological treatment means, and separation of the second treated water treated in the second biological treatment step into sludge and third treated water by a separation membrane A membrane separation biological treatment step having a membrane separation step;
And d) a sludge extraction step of extracting sludge generated in the second biological treatment step;
In the sludge extraction step, the soluble BOD sludge load in the second biological treatment step is 0.05 kg-BOD / kg-MLSS / d or more and less than 0.10 kg-BOD / kg-MLSS / d The sludge generated in the second biological treatment step is extracted so that the sludge retention time (SRT) in the second biological treatment step is in the range of 10 to 15 days, and the sludge is used as the first biological treatment step. The waste water treatment method characterized in that the waste water is discharged out of the membrane separation biological treatment process without being returned. In the sludge drawing process, the so sludge concentration becomes range of 3000~5000mg / L in the second biological treatment process, according to claim 3, wherein the withdrawal of the sludge generated in the second biological treatment process Wastewater treatment method.