TWI386375B - Biological processing mehtod and apparatus for organic sewage - Google Patents

Description

Biological treatment method and device for organic sewage

The invention relates to a biological treatment method and device for organic sewage.

The activated sludge treatment method has been widely practiced as a representative treatment method for biological treatment plant drainage or sewer water. In the activated sludge treatment equipment provided with an aeration tank or a sedimentation tank for carrying out such treatment, the characteristics of the sludge have a great influence on the water treatment function and the treatment cost. In order to maintain good water quality, it is extremely important to maintain good sludge settling.

However, as is well known, the sedimentation and concentration of activated sludge are generally not large. Therefore, in the conventional activated sludge treatment method, the concentration of MLSS (Mixed Liquor Suspended Solids) of the aeration tank is maintained at a high concentration and high, and there is a tendency to generate an activated sludge bulking trouble. problem. As a result, it is inevitable that in the conventional activated sludge treatment method, the volumetric load of the BOD (biological oxygen demand) of the aeration tank cannot be increased, and the volume of the aeration tank and the sedimentation tank becomes large, and even a large amount cannot be solved. The problem related to the nature of the remaining sludge and the like.

So far, there is no known technique for biologically controlling the sedimentation or concentration of activated sludge. For this reason, in the prior art, in order to improve the sedimentation property of the activated sludge, inorganic mineral particles such as very fine sand are added to the aeration tank, and sludge is adhered by adhering sand particles to the activated sludge. A method of good sedimentation, or a method of adding a polymer flocculant to a sludge to be treated, a method of improving sedimentation by aggregating activated sludge, or returning sludge by ozone treatment, thereby killing filamentous bacteria and preventing The method of producing sludge expansion, etc., actually has to use physicochemical methods.

However, in such a physicochemical technique, a method of adding inorganic mineral particles such as sand to an aeration tank, for example, is liable to cause troubles in sedimentation of sand particles and accumulation in the bottom of an aeration tank, and also due to sand particles and The excess sludge is discharged out of the system together, so it is necessary to supplement the shortcomings of sand particles. Further, in the method of adding a polymer flocculant or the method of ozone treatment, the cost of adding a polymer flocculant or the cost of generating ozone is high, and there is a disadvantage of a so-called high cost. Moreover, there is no technique for improving the sedimentation and concentration of the floating sludge itself in such treatment methods. So far, there is no known biological technique that can surely prevent sludge swelling.

The present invention is not based on the above-mentioned physicochemical method, but is based on the knowledge that "the biological means can not reliably improve the sedimentation and concentration of activated sludge?" The inventors have found that the sedimentation and concentration characteristics of the floating sludge can be remarkably improved by a simple method, and as a result, the MLSS concentration of the aeration tank can be significantly increased, and the BOD volume load of the high aeration tank can be set, and the completion is completed. The new technology of the present invention.

One of the conventional biological treatment techniques is to immerse a string-like biological attachment material in an aeration tank of biologically treated organic sewage, and become biological by the attached microorganism (biofilm) on the biological attachment material. Method for purifying sewage (JP-A-8-206673).

The present inventors have found out that in such a biofilm processing apparatus, the sewage inflow side of the aeration tank is treated by the activated sludge method, and the microbial attachment material is impregnated under a condition of a certain BOD volume load or more. By supplying raw water, the sedimentation property and the concentration property of the activated sludge can be remarkably improved by purely biological means without using a drug or the like, and the present invention has been completed based on this knowledge.

In the biological treatment method of the organic sewage according to the present invention, the aeration tank subjected to the activated sludge treatment is divided into a raw water inflow portion, and a downstream side portion is formed closer to the raw water inflow portion, and the microorganism water-attaching portion is impregnated in the raw water inflow portion, and The BOD volume load of the microorganism adhering material is set to be 1 kg/(m ³ .day or more).

The biological treatment device for organic sewage according to the present invention includes: an aeration tank having a raw water inflow portion and a portion closer to a downstream side than the raw water inflow portion, and having an immersion in the raw water inflow portion and capable of being loaded with a BOD volume Microbial attachment material that operates above 1 kg/(m ³ . day).

According to the present invention, the following effects can be obtained.

1. It does not use inorganic mineral particles such as sand, or a coagulant or ozone, and it can produce activated sludge with good sedimentation and concentration by biological action. It can prevent sludge swelling caused by filamentous bacteria.

2. As a result, by providing a sedimentation tank on the downstream side of the aeration tank, the sedimentation tank can surely precipitate the sludge, so that the treated water can be obtained. And increasing the concentration of returned sludge, thus increasing the concentration of MLSS in the aeration tank.

3. As a result, the amount of suspended microorganisms in the aeration tank will be increased, and the microbial factors attached to the microbial attachment material can also be used to purify the sewage, so that the BOD volume load of the aeration tank can be increased. Therefore, it is possible to easily cope with an increase in the BOD concentration of the sewage or an increase in the amount of the sewage water.

4. Even if a filamentous fungus is produced, it may be caught by the microbial attachment material or entangled into a silky shape without the trouble of sludge swelling.

5. After the MLSS concentration is increased, it can be reliably operated under high MLSS (10000 mg/L or more). To this end, the amount of excess sludge is reduced by an active food chain.

At the same time, in the conventional water treatment method, the MLSS of the standard activated sludge method is about 1000 to 2000 mg/L, and even the MLSS of the Oxidation ditch method is about 2000 to 5000 mg/L. In this fact, it can be understood how high the concentration of MLSS can be used to treat sewage.

In summary, the technology of the present invention can significantly improve the sedimentation and concentration of the floating sludge for the biological treatment of the organic sewage, and is a technique capable of significantly increasing the MLSS concentration of the aeration tank.

A representative embodiment of the present invention will be described with reference to Fig. 1.

In Fig. 1, reference numeral 1 denotes an aeration tank which is divided into a raw water inflow portion 3 on the upstream side and a downstream side portion 4 on the downstream side thereof by the partition wall 2. In Fig. 1, although the downstream side portion 4 of one stage is illustrated, the downstream side portion 4 may have a multi-stage structure. The treated water generated by the treatment in the raw water inflow portion 3 flows over the upper end of the partition wall 2 and flows into the downstream side portion 4. 5 is a raw water supply path, and raw water can be supplied to the raw water inflow portion 3 and the downstream side portion 4. A sedimentation tank 6 is provided on the downstream side of the aeration tank 1, and the sedimentation tank 6 receives treated water generated by treatment in the downstream side portion 4 of the aeration tank 1. The sedimentation treatment of the sludge is carried out in the sedimentation tank 6 and the sludge is sent back to the sludge delivery circuit in the aeration tank 1 in order to return the precipitated sludge as a return sludge, in the illustrated example. It is connected to the raw water supply road 5. The 8 series residual sludge discharge path branches from the sludge delivery circuit 7. 9 is a discharge path of treated water generated by precipitating sludge in the sedimentation tank 6.

In the raw water inflow portion 3 of the aeration tank 1, the microorganism attachment material 10 is provided in an immersed state. This microbial attachment material 10 can be treated under the condition that the BOD capacity load is 1 kg/(m ³ .day) or more. The material to be treated under such a high load condition is relatively limited, and it is impossible to handle such a high load condition in a contact material such as a pellet, a cylinder or a rod made of a conventional synthetic resin. As a suitable adhering member, for example, those shown in JP-A-5-92196 can be mentioned. The adhering member has a core material composed of a material which does not easily adhere to microorganisms and a spike-shaped thread composed of a material which is easy to adhere to microorganisms, and a plurality of spike-shaped filaments are distributed throughout the length direction of the core material, whereby the core material is formed The spiral is radial and is a string that can be shaken and protruded. Specifically, for example, it is sold by NED Corporation in Japan as "rocking bed (registered trademark)" or "Bio fringe (registered trademark).

The microbial attachment material 10 is preferably a string-shaped attachment member made of such a core material and a spiked wire, and is arranged in a plurality of rows in the vertical direction inside the frame. In the case of such a special adhering member, the above-described BOD capacity load can be stably treated under a high load condition of 1 kg/(m ³ .day) or more.

A diffuser 11 such as a diffuser is provided on the side of the microorganism adhering material 10 of the raw water inflow portion 3, and an air lift effect of the bubble ejected from the diffuser 4 is generated along the air lift effect. The circulating flow (moving) of the adhering member of the microbial attachment material 10. Reference numeral 12 denotes a blower 12 (blower) provided outside the tank for supplying air to the air diffusing device 11.

The microorganism attachment material 10 described above is not provided in the downstream side portion 4 of the aeration tank 1, and instead of this, the downstream side portion 4 is provided with a diffuser 13 for aeration treatment. The air diffusing device 13 also receives the air supplied from the air blower 12.

The details of the biological treatment device having such a structure during operation are as follows. That is, when the aeration tank 1 is an aerobic biofilm treatment method, since it is not desirable to significantly increase the anaerobic layer inside the biofilm, it is important to replace the new biofilm early, for this purpose. By causing a turbulent flow of water or bubble flow in the attached member material, or colliding with the attached member material, the self-adhesive member peels off the excess biofilm sludge to prevent the adhesion due to excessive adhesion of the biofilm sludge. The material is occluded. For example, in the string-like attachment member described in the above-mentioned JP-A-5-92196, the spike-like wire system is formed by shaking the position of the core material as the base end, so that it can be shaken. The shaking effect causes peeling when the biofilm reaches an appropriate thickness, so that the effect of preventing excessive adhesion of the biofilm is particularly excellent. As described above, the so-called shear peeling effect effectively prevents the biofilm from excessively adhering to the adhering member, and effectively performs the renewal of the biofilm, and by peeling, a large amount of peeling sludge is generated.

In this way, the peeled sludge which occurs in the raw water inflow portion 3 having a high BOD volume load will flow over the upper end of the partition wall 2 and flow into the downstream side portion 4 of the aeration tank 1, where the downstream side portion 4 serves as a floating sludge. After flowing, it is sent to the precipitation tank 6 and is surely separated by precipitation.

The downstream side portion 4 of the aeration tank 1 is a region where the microorganism adhering material 10 is not provided, and is a region where the activated sludge floats and flows by aeration of the diffusing device 13 as in the usual activated sludge method. In this portion, it is also possible to coexist with a conventional flow granular support such as gel particles, a granular sponge, or a granular plastic.

The partition wall 2 may be provided as needed according to the demand, and may not be provided depending on the occasion. When it is installed, there is no reverse mixing from the downstream side portion 4 to the raw water inflow portion 3, and the BOD volume load in the raw water inflow portion 3 can be surely maintained at a high value.

The immersion of the microorganism adhering material 10 in the raw water inflow portion 3 of the aeration tank 1 is extremely important, and even if it is provided in the downstream side portion 4, the sedimentation effect of the floating sludge cannot be improved. The reason for this is that when the microorganism-attached material 10 is filled in the downstream side portion 4, the raw water BOD is mostly removed by the floating activated sludge before contacting the microorganism-attached material 10, so that the biofilm of the microorganism-attached material 10 grows. Since the speed is small, the amount of the peeled sludge is reduced.

When the BOD of the raw water is extremely high, when the raw water flows into the raw water inflow portion 3, the BOD volume load on the microorganism adhering material 10 becomes extremely high, for example, at 10 kg/(m ³ .day) or more. There will be cases where the oxygen supply is insufficient and the dissolved oxygen cannot be maintained. In this case, it is sufficient to distribute a part of the raw water to the downstream side portion 4 of the rear stage.

In the sedimentation tank 6, the activated sludge is sedimented and separated. The treated water is sent to the discharge path 9 over the outflow. Part or all of the settled sludge is regarded as the return sludge, and is sent back to the raw water inflow portion 3 of the aeration tank 1 through the sludge feed circuit 7. The returned sludge can also be returned to the downstream side portion 4 of the aeration tank 1.

The present inventors have experimentally examined the results of various conditions in which the peeling sludge having good sedimentation property can be efficiently produced, and the sedimentation property of the entire activated sludge of the aeration tank 1 can be improved, and the following facts are clarified. In other words, the raw material inflow portion 3 of the aeration tank 1 is partially impregnated with the microorganism adhering material 10 to positively contact the raw water with the microorganism adhering material 10. In the downstream side portion 4 of the aeration tank 1, even if the microbial adherend 10 is impregnated, the effect of improving the sedimentation property is hardly judged.

2. In order to produce activated sludge having good sedimentation property, the volume of the microbial attachment material 10 is present under certain conditions, that is, (the volume of the microbial attachment material 10 / the total volume of the aeration tank 1) ≧ 0.1. (The volume of the microbial attachment material 10 / the total volume of the aeration tank 1) <0.1, the effect of improving the sedimentation property is hardly judged.

3. The BOD volume load of the microbial attachment material 10 is set to 1 kg/(m ³ .day) or more. When the load is lower than this, the sedimentation improving effect may become small or have no effect.

4. Even if the volume of the microbial attachment material 10 / the total volume of the aeration tank 1 is ≧ 0.8, there is almost no improvement in the sedimentation improving effect, and only the equipment cost of the microbial attachment material 10 is increased, which becomes meaningless. investment.

When the sewage treatment apparatus is operated under the above conditions, it is determined that activated sludge having excellent sedimentation property and concentration property can be surely produced.

According to the present invention, the detailed mechanism of the significant improvement in the sedimentation property of the activated sludge is not known at present, but can be estimated as follows.

In other words, when the microbe adhering material 10 is immersed in the raw water inflow portion 3 of the aeration tank 1 to supply the raw water under the predetermined BOD volume load condition, the microbial membrane is formed on the surface of the adhering member of the microbial adherend 10 when the operation is continued. It will proliferate protozoa and tiny metazoans. Under the symbiosis of these microorganisms, a dense biofilm is formed by a variety of microbial metabolites (considered as mucopolysaccharides) instead of the usual activated sludge flocs. This biofilm is considered to have good sedimentation due to the inclusion of the above-mentioned viscous material. The dense biofilm is appropriately peeled off from the adhering member of the microbial adherend 10 due to turbulent flow, and the exfoliated sludge formed by the peeling is considered to be floating active sludge, and floats inside the downstream side portion 4 of the latter stage. When it is in a state of good sedimentation, it is sent to the sedimentation tank 6 and is separated by sedimentation.

When the BOD volume load of the microbial attachment material 10 is less than 1 kg/(m ³ .day), it is judged that the effect of improving the sedimentation performance of the floating sludge is not caused, and it is presumed that the growth rate of the biofilm is slow, resulting in the biofilm. The peeling frequency is lowered, and the particle diameter of the peeled biofilm (peeling sludge) becomes small.

The peeling sludge is subdivided in the downstream side portion 4 of the aeration tank 1 due to the long-term retention process, and although there is a concern that the sedimentation property is deteriorated, the actual experiment confirms that even if the downstream side portion 4 is aerated, the sewage is contaminated. The mud is not subdivided but flows into the sedimentation tank 6 while maintaining a good sedimentation state.

In the microbial attachment material 10, when the rocking type attachment member described in JP-A-5-92196 is applied, the water flow in the vicinity of the spiked wire of the attached member is formed by a lot of Karman Vortex. The peeling sludge and the activated sludge from the adhering member are turned into granular sludge, and it is considered that the sedimentation separation property of the activated sludge in the sedimentation tank 6 is further increased. By the above-described eddy current action, the filamentous fungus which becomes a cause of sludge swelling becomes a round wire-like mass, and the fact that the sedimentation property is improved can also be observed.

[Example 1] [Review of the appropriate ratio of (volume of microbial attachment material) / (full volume of aeration tank)]

In a laboratory-scale apparatus, an appropriate ratio of the volume of the microbial adherent/(the full volume of the aeration tank) is also obtained, in order to obtain a necessary ratio for improving the sedimentation effect of the activated sludge. The details are described below.

The Bio fringe manufactured by NED Corporation was made into a length of 40 cm, and a plurality of strips were placed in various volume molds shown in Table 1, in which the Bio fringe was densely packed with each other and prepared for different volumes. Various microbial attachment materials. Further, a plurality of aeration tanks having an effective volume of 50 liters (depth 20 cm, width 50 cm, water depth 50 cm) were prepared, and various microbial adherends of the above different volumes were immersed in the respective raw water inflow portions. An aeration tank that does not impregnate the microbial attachment material is also prepared (the mold volume is 0 liter). A sedimentation tank is disposed near the downstream side of the aeration tank. In each of these tanks, the activated sludge collected by the sewage treatment plant was charged in a manner of MLSS of 5000 mg/L.

The corn steep liquor was made into artificial raw water (water temperature 22 to 24 ° C) diluted with tap water in a BOD of 1000 mg/L, and the whole volume of each aeration tank was 1 kg/(m ³ .day). The conditions flow into each of the tanks, and the return sludge ratio [(return sludge flow rate) / (raw water flow rate)] = 2, the dissolved oxygen concentration in the aeration tank is above 2 mg / L, and the sedimentation tank water area load is 8 Under the condition of m ² /(m ³ .day), it was continuously operated for 5 months. Then, after 4 months from the lapse of the time point, the average value of the return sludge concentration returned from the sedimentation tank to the aeration tank was measured, and the results are shown in Table 1.

In Table 1, the higher the concentration of the returned sludge, the more excellent the sedimentation/concentration of the activated sludge.

From Table 1, when the ratio of (the volume of the microorganism attached material) / (the total volume of the aeration tank) is less than 0.1, the effect of improving the sedimentation property is hardly judged. On the contrary, the ratio of (the volume of the microbial attachment material) / (the total volume of the aeration tank) is in the range of 0.1 to 0.7, and the concentration of the returned sludge is remarkably large, and it can be confirmed that the effect is large. However, when the ratio of (the volume of the microorganism attached material) / (the total volume of the aeration tank) is 0.8 or more, the effect of increasing the concentration of the returned sludge cannot be determined.

[Embodiment 2] [Review of appropriate BOD volume load conditions for microbial attachments]

In a laboratory scale device, a review of the appropriate BOD volume loading conditions of the microbial attachment material is performed.

The aeration tank (volume 50 liter) used in the test of Example 1 was used with the sedimentation tank. The aeration tank has the same structure as that of the first embodiment, but the volume is filled with 20 liters of Bio fringe type microorganism attachment material. For comparison, tests were also carried out without filling the microbial attachment material. Further, the BOD capacity load of the microbial attachment material is varied by changing the amount of raw water treatment. In the raw water, the water was diluted with a corn steep liquor having a BOD of 1000 mg/L used in Example 1.

The test results are shown in Table 2. As shown in Table 2, when the BOD capacity load of the microbial attachment material is less than 1 kg/(m ³ .day), the sludge concentration returned from the sedimentation tank becomes low, and there is no microbial adhesion. Compared with the case of materials, it is not considered to have the effect of improving the sedimentation of activated sludge.

[Example 3] [Results applicable to actual facilities]

An example of the present invention is applied to the drainage treatment facility of the confectionery factory.

In the past, the plant, the water depth of 5 m section of the aeration tank 2 arranged in series, with each volume of 800 m ^3, 750 m ³ of activated sludge plant, the column 3 of the table shown in the old method of The water quality (average value) raw water is treated with activated sludge at a return sludge ratio of 2.4. The results are shown in Table 3. In that case, as shown in Table 3, it is difficult to increase the MLSS of the aeration tank to 6000 mg/L or more due to poor sedimentation of the activated sludge. Further, when the amount of the drainage treatment is increased to 450 m ³ /day or more, since the activated sludge flows out from the sedimentation tank, it is impossible to increase the drainage treatment amount higher than this.

In the old equipment of such a condition, the present invention was carried out in order to improve the sedimentation property of activated sludge.

That is, in the conventional raw water inflow side of the conventional aeration tank (volume 800 m ³ ), the microbial attachment material (volume 370 m ³ ) is immersed in the mold box, wherein the microbial attachment material is substantially bio-independent with each other. The space is not provided, and the above-mentioned Bio fringe is densely installed. The Bio fringe (each with a length of 3.5 m) has a mounting pitch of 10 mm. The volume of the mold box is 370 m ³ , and the total length of the Bio fringe installed in the mold box is 37,000 m. The volume of material adhering microorganisms substantial (370m ³⁾ and the full volume of the aeration tank (1525 m ³⁾ ratio of 0.24. The volumetric load in the microbial attachment material was 1.46 kg/(m ³ .day).

In the practice of the present invention, the microorganism frit material of Bio fringe is placed in the raw water inflow portion of the aeration tank, and the rest is operated under the same conditions as the original equipment. Thus, after three months, the same measurement as in the old method was performed. The results are shown in Table 3. As shown in Table 3, according to the present invention, the sedimentation and concentration of the activated sludge can be remarkably improved, and the return sludge concentration returned from the sedimentation tank to the aeration tank is 8500 from the old method. The mg/L is increased to 15600 mg/L. As a result, the MLSS of the aeration tank was increased from 6000 mg/L of the old method to about 11000 mg/L of about 2 times.

Accordingly, the BOD and sludge load can be reduced to less than 1/2 from the old method. Moreover, regarding the excess sludge conversion rate in the old equipment, the average BOD removal is 0.26 kg per 1 kg, whereas in contrast to this invention, the excess sludge conversion rate can be reduced to 0.056 per 1 kg of BOD. Kg. The reason for this is considered to be caused by the effect of halving the BOD and the sludge load, and the effect of sludge reduction caused by the attached sludge food chain of the microbial attachment material.

In Table 3, SVI (Sludge Volume Index) means that when the mixture of the aeration tank is allowed to stand for 30 minutes, the volume occupied by 1 gram of MLSS is expressed by the number of liters (ml). And have the following relationship.

SVI=SV30×10000/MLSS

In detail, the SVI system indicates the sedimentation property and compaction property of the activated sludge, and it is usually preferably about 100 angstroms, and when the mixed liquid in the aeration tank is in a state in which the sludge is expanded, that is, in the case of so-called light sludge, Become a value of 300 or more. When the MLSS is high, since the SV rises due to the measured tube wall resistance, the SV is tested by diluting 2 times and diluting 3 times to obtain a true SV.

The above SV (Sludge Volume) indicates the precipitation rate of the activated sludge. This SV is the percentage of the amount of precipitated sludge after the mixture of the aeration tank in which the cylinder is taken up by the measuring cylinder is allowed to stand for 30 minutes, relative to the entire percentage of the sample.

1. . . Aeration tank

2. . . Partition wall

3. . . Raw water inflow

4. . . Downstream side

5. . . Raw water

6. . . Precipitation tank

7. . . Sludge delivery circuit

8. . . Excess sludge discharge road

9. . . Disposal of treated water

10. . . Microbial attachment material

11. . . Air diffuser

12. . . Blowing machine

13. . . Air diffuser

Fig. 1 is a view showing a biological treatment apparatus for organic sewage according to an embodiment of the present invention.

1. . . Aeration tank

2. . . Partition wall

3. . . Raw water inflow

4. . . Downstream side

5. . . Raw water

6. . . Precipitation tank

7. . . Sludge delivery circuit

8. . . Excess sludge discharge road

9. . . Disposal of treated water

10. . . Microbial attachment material

11. . . Air diffuser

12. . . Blowing machine

13. . . Air diffuser

Claims (2)

A biological treatment method for organic sewage, wherein an aeration tank for performing activated sludge treatment is divided into a raw water inflow portion and a portion closer to a downstream side than the raw water inflow portion, and a microbial attachment material is impregnated in the raw water inflow portion, and The BOD volume load of the microorganism attachment material is set to be 1 kg/(m ³ ‧ day) or more; the volume of the microorganism attachment material and the total volume of the aeration tank satisfy the following relationship: 0.1 ≦ (volume of the microorganism attachment material / The full volume of the aeration tank is <0.8. An organic sewage treatment device includes: an aeration tank having a raw water inflow portion and a portion closer to a downstream side than the raw water inflow portion; and an immersion in the raw water inflow portion and capable of being loaded with a BOD volume 1kg/(m ³ ‧ day) or more of the microbial attachment material; the volume of the microbial attachment material and the full volume of the aeration tank satisfy the following relationship: 0.1 ≦ (volume of the microbial attachment material / full volume of the aeration tank) ) <0.8.