JP4899253B2 - Wastewater aerobic treatment method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an aerobic treatment method for waste water.
[0002]
[Prior art]
The aerobic biological treatment method that treats organic wastewater under aerobic conditions using the action of aerobic microorganisms, such as the activated sludge treatment method, has low treatment costs and excellent treatment performance. Widely used in general. In such an aerobic treatment method, a carrier is introduced for the purpose of increasing the amount of aerobic microorganisms retained in the aeration tank or extending the residence time. As a carrier, sponge, plastic, polymer Gels are used. By adding a carrier to the aeration tank, a biofilm of aerobic microorganisms is formed on the surface of the carrier, so that high-concentration sludge can be retained in the aeration tank.
[0003]
However, the carrier used conventionally has a problem that the manufacturing cost of the carrier itself is high and the processing cost becomes high. In addition, depending on the properties of the carrier surface, it takes a long time to form an aerobic microorganism film, and thus it may take a long time to start up the operation. Furthermore, when the carrier material is an artificial material such as plastic, there is a problem of disposal.
[0004]
[Problems to be solved by the invention]
The object of the present invention is to solve the problems in the conventional carrier addition method, so that the production cost of the carrier itself is not required, the formation of the microbial film is fast, and there is no problem of disposal. It is to propose an aerobic treatment method for waste water that can be treated efficiently.
[0005]
[Means for Solving the Problems]
The present invention is the following aerobic treatment method for waste water.
(1) In a method of aerobic treatment of wastewater in the presence of activated sludge containing aerobic microorganisms, a carrier carrying aerobic microorganisms is charged into a reaction tank.
As a carrier supporting aerobic microorganisms, granule sludge containing anaerobic microorganisms or a crushed product thereof is put into a reaction tank and mixed with activated sludge in the tank,
By introducing the liquid to be treated into the reaction tank to which the carrier has been added and aeration,
Forming a biofilm of aerobic microorganisms on the surface of the carrier;
A method of aerobic treatment by increasing the amount of aerobic microorganisms that can be held in a reaction tank ,
An aerobic treatment method for wastewater, characterized in that granule sludge formed in methane fermentation or a crushed product thereof is used as the carrier for supporting the aerobic microorganisms .
[0006]
In the present invention, the wastewater to be treated is not limited as long as it can be treated by aerobic biological treatment, and examples thereof include organic wastewater or ammonia-containing wastewater. The organic drainage liquid may contain a hardly biodegradable organic substance or inorganic substance, and may contain ammonia nitrogen or the like. Specific examples of wastewater include sewage, human waste, food factory wastewater and other industrial wastewater.
[0007]
The carrier used in the present invention is granulated sludge in which sludge containing anaerobic microorganisms is granulated by the self-granulating action of microorganisms or a crushed product thereof. As such granular sludge or a crushed product thereof , a granular sludge formed by methane fermentation or a crushed product thereof is used. Granule sludge formed in a reactor in which methane fermentation is carried out by the Granular Sludge Bed (expanded granular sludge bed) method, granule sludge discharged from these reactors, and the like. Usually, these granular sludges have good settling properties.
[0008]
In the UASB or EGSB method, organic acid fermentation and methane fermentation are usually carried out in separate reactors, and the acid production liquid from the organic acid fermentation is placed on a UASB type methane fermentation tank in which a sludge blanket made of granular sludge is formed. Although methane fermentation is carried out by flowing in a countercurrent, granule sludge formed by two-phase methane fermentation in which organic acid fermentation and methane fermentation are separated in two stages is preferable in the present invention. However, it is also possible to use granule sludge formed by one-phase methane fermentation in which organic acid fermentation and methane fermentation are performed in one reactor.
[0009]
Granule sludge used in the present invention does not need to be granulated sludge granulated by selecting special equipment, operation, conditions, etc., in a treatment system in which methane fermentation is generally performed by a known method. The generated granular sludge can be used as it is. For example, any of high temperature methane fermentation and medium temperature methane fermentation may be used.
[0010]
Granule sludge formed by the usual UASB and EGSB methods is composed of acetic acid-assimilating microorganisms belonging to the genus Methanosaeta, with the presence of hydrogen-utilizing methane bacteria, acetic acid-producing bacteria, acid-producing bacteria, etc. It constitutes an ecosystem. In addition, acid-producing bacteria that decompose sugars, lipids, proteins, etc., have a function of producing mucilage and strengthening the binding force between bacteria, and the strongest granular sludge is formed in the case of a sugar substrate. Is done. Ordinary sewage and other organic wastewater contains carbohydrates and other high-molecular organic substances. When this is anaerobically treated, organic acids are produced by the above-mentioned anaerobic microorganisms. It becomes acetic acid and is further decomposed into methane and carbon dioxide. For this reason, the above-mentioned various anaerobic microorganisms proliferate, and granule sludge with high strength is formed.
[0011]
The growth process of granular sludge in the UASB and EGSB methods is not clear, but anaerobic microorganisms adhere to the surface of the fine inorganic SS with a particle size of around 0.1 mm and the surface of scale components containing calcium and magnesium. It is said that new anaerobic microorganisms grow and adhere in an annual ring shape with the minute SS and scale as the core, and it takes several months or more to grow into granular sludge with an average particle size of 0.3 to 5 mm. Yes. The grown granular sludge is crushed by the flow of water and gas generated in the reaction tank, and the crushed fine particles and debris are used as the nucleus to grow the next granular sludge.
[0012]
Granule sludge used as a carrier in the present invention has an average particle size of about 0.3 to 5 mm, preferably 0.5 to 2 mm, but is crushed by a crushing device such as a cutter pump, a mill, or a homogenizer. You can also use the granule.
[0013]
In aerobic treatment using a carrier, oxygen diffusion may be the main rate-limiting step. The depth at which oxygen penetrates into the biofilm is about 100 μm at the maximum in the case of aeration using ordinary air. To handle high loads, the surface area is increased or the oxygen partial pressure in the aeration gas is increased. It is necessary to let In order to increase the surface area of the carrier, it is effective to reduce the size of the carrier. From this point of view, it is possible to reduce the particle size by crushing rather than using granular sludge exceeding the average particle size as it is. Thus, it is preferable to increase the surface area. Moreover, since the granular sludge with a large particle size has a space | gap formed inside and the sedimentation property may fall, it is preferable to use such a granular sludge by crushing.
[0014]
The carrier is used in a reaction tank such as an aeration tank. An aerobic microorganism forms a biofilm on the surface of the carrier by introducing the carrier into the reaction tank and mixing it with the activated sludge in the tank to perform aerobic treatment. The biofilm is formed spontaneously by performing the same operation as a normal aerobic biotreatment in which a liquid to be treated is introduced into a reaction tank to which a carrier is added and aerated. In order to promote the formation of biofilms, biologically treated sludge can be input as a seeding source. The aerobic microorganisms that form a film on the carrier partly peel off due to growth and become suspended activated sludge.
The added amount of the carrier is 5 to 80% by volume, preferably 10 to 50% by volume, per 1 m ³ of the reaction tank.
[0015]
The treatment method of the present invention can be carried out by adopting a known aerobic treatment method in a state where the carrier is charged into a reaction tank. Any reactor can be used as a reaction tank in the aerobic treatment. Moreover, as a solid-liquid separator, a precipitation tank, a membrane separator, a centrifuge, etc. can be used. In addition, an aerobic treatment apparatus in which GSS (gas solid content separator) is provided in the reaction tank and the aerobic treatment and the solid-liquid separation are performed in one reaction tank may be employed. By performing the aerobic treatment with the carrier loaded, the amount of aerobic microorganisms that can be retained in the reaction tank can be increased, and the treatment efficiency and the quality of the treated water can be improved. As a specific aerobic treatment, the standard activated sludge method is used in which the wastewater is aerated together with the return sludge in the aeration tank, the aerated liquid is solid-liquid separated in the solid-liquid separation tank, and a part of the separated sludge is returned to the aeration tank. , And various modifications thereof.
[0016]
Since granule sludge has a faster settling speed than ordinary floc, it is possible to add granule sludge to a distributed aeration tank having an aeration tank and a settling tank so that the floc and the carrier coexist. In this case, the amount of sludge that can be held in the aeration tank is further increased as compared with the case where the carrier is used alone, so that the sludge retention time can be increased, and the amount of excess sludge can be reduced and the quality of the treated water can be expected.
[0017]
In the present invention, granule sludge, which is originally a set of microorganisms, is used as the carrier, so that the affinity between the carrier and the microorganism is very good, and thus the generation rate of the biofilm is faster than that of the artificial carrier. In the present invention, since such a carrier is used, the operation start-up period can be shortened.
Further, in the present invention, surplus granule sludge generated in the anaerobic treatment can be used as it is, so that the production cost of the carrier is not required and the treatment can be performed at a low cost.
[0018]
In the present invention, since the granular sludge is a mass of anaerobic microorganisms, the amount of carrier in the reaction tank can be controlled in the same manner as in the operation of normal anaerobic treatment. Since the extracted carrier does not contain artifacts, it can be treated by ordinary excess sludge treatment, such as dehydration, anaerobic digestion, composting, etc., and even when it is treated as waste, it is disposed of as biological surplus sludge. it can.
[0019]
In long-term operation, granulated sludge is destroyed and may flow out into the treated water as SS. However, since the carrier itself is derived from microorganisms, the load on the environment is not the usual aerobic sludge outflow. does not change.
When the amount of the carrier in the reaction tank decreases due to outflow or the like, granule sludge can be additionally charged.
[0020]
Further, in the present invention, the SRT of activated sludge is increased by adding a carrier, and can be, for example, 10 days or longer, so that it is possible to retain nitrifying bacteria. In the aerobic treatment system, organic matter is decomposed. In addition, nitrification can be performed simultaneously, which is advantageous when performing biological nitrification denitrification.
[0021]
As described above, in the present invention, granule sludge is used as a carrier for supporting aerobic microorganisms, so the following effects can be obtained.
1) Adhesion to the carrier is good and the startup period can be shortened.
2) Since the production cost of the carrier is not required, the processing cost can be reduced.
3) Good sedimentation and easy solid-liquid separation.
4) All disposal can be done as organic sludge.
5) The size and amount of the carrier can be controlled according to the operating conditions.
6) It is possible to have a denitrification effect.
7) The performance of the processing apparatus can be improved by combining with floating sludge.
[0022]
【Effect of the invention】
In the method for aerobic treatment of waste water of the present invention, as a carrier for supporting aerobic microorganisms, granular sludge containing anaerobic microorganisms or a crushed product thereof is introduced into a reaction tank and mixed with activated sludge in the tank, and the carrier is used. By introducing a liquid to be treated into the added reaction tank and aeration, a biofilm of aerobic microorganisms is formed on the surface of the carrier, and the amount of aerobic microorganisms that can be retained in the reaction tank is increased to perform aerobic treatment . Since the granular sludge formed in methane fermentation or its crushed material is used as the carrier for supporting the aerobic microorganisms, there is no manufacturing cost of the carrier itself, the formation of the microbial film is fast, and there is a problem of disposal. The waste water can be aerobically treated at low cost and efficiently using no carrier.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the present invention will be described below.
FIG. 1 is a flow sheet showing an aerobic treatment method for organic waste water according to an example.
In FIG. 1, 1 is an aeration tank, 2 is granule sludge as a carrier, and 3 is a sedimentation tank.
[0024]
In the treatment method of FIG. 1, at the start of operation, raw water is introduced into the aeration tank 1 from the raw water channel 4, granule sludge 2 is introduced, air is sent from the air supply channel 5, and air is diffused from the diffuser 6. Then, aeration is performed to form a biofilm of aerobic microorganisms on the surface of the granular sludge 2. In this case, a biofilm can be formed spontaneously, or biotreatment sludge of another treatment system can be input as a seeding source to promote the formation of the biofilm. Granule sludge 2 has a very good affinity with microorganisms and has a high rate of biofilm formation, so the operation start-up period can be shortened compared to the case where a carrier made of an artificial material such as a sponge is used. It is possible to shift to a steady state at an early stage.
[0025]
In a steady state after an aerobic microorganism biofilm is formed on the surface of the granule sludge 2, the raw water is introduced into the aeration tank 1 from the raw water channel 4 and returned from the granule sludge 2 and the sludge return channel 7. It mixes with the return sludge and the floating activated sludge in the aeration tank 1, sends air from the air supply path 5, diffuses air from the air diffuser 6, performs aeration, and performs aerobic treatment. At this time, the granular sludge 2 flows in the aeration tank 1.
[0026]
The mixed liquid in the aeration tank 1 is taken out part by part and introduced into the precipitation tank 3 from the communication path 8 to perform solid-liquid separation. The separated liquid is discharged from the treated water channel 9 as treated water, and the separated sludge containing the granular sludge 2 and the suspended activated sludge is returned to the aeration tank 1 from the sludge return channel 7 as a returned sludge. Granule sludge 2 has good sedimentation and solid-liquid separation is performed well. The remainder is discharged out of the system from the sludge discharge passage 10 as surplus sludge.
When the granule sludge 2 in the aeration tank 1 decreases due to outflow or the like, the granule sludge 2 is additionally charged into the aeration tank 1.
[0027]
By performing aerobic treatment in this manner, aerobic microorganisms are carried in the granule sludge 2 and held in large quantities in the aeration tank 1, so that the aerobic treatment performance is efficiently performed and the water quality is high. Treated water is obtained. In addition, even if SS such as granule sludge 2 flows into the treated water for some reason, since the granule sludge 2 is derived from microorganisms, the load on the environment is the outflow of activated sludge in the conventional aerobic treatment. No change.
[0028]
In FIG. 1, granule sludge on which a biofilm has already been formed can be introduced, or granule sludge can be introduced into an aeration tank in which aerobic treatment is performed in a steady state without using a carrier. .
In FIG. 1, a membrane separator or other sludge separator can be used instead of the sedimentation tank 3.
[0029]
FIG. 2 is a cross-sectional view of an aerobic treatment apparatus showing an aerobic treatment method for organic wastewater according to another embodiment. The apparatus of FIG. 2 is an apparatus that performs aerobic treatment of organic wastewater in one reaction tank by utilizing the good sedimentation property of granular sludge, omitting the solid-liquid separation device.
In FIG. 2, 11 is a reaction tank, 12 is granular sludge as a carrier, a funnel-shaped inclined separation plate 13 in the upper part of the tank, and a cap-shaped gas separation plate 14 so as to close the opening in the lower part. And the inside of the tank is divided into a reaction unit 15 and a solid-liquid separation unit 16, and the reaction unit 15 performs aerobic treatment, and the solid-liquid separation unit 16 sediments and separates the granular sludge 12. Has been. The inclined separation plate 13 and the gas separation plate 14 constitute a gas solid content separator.
[0030]
In order to perform the aerobic treatment with the apparatus of FIG. 2, raw water is introduced into the lower part of the reaction tank 11 from the raw water channel 21, and air is sent from the air supply channel 22 and diffused from the air diffuser 23 to perform aeration. The raw water passes through the perforated plate 24, becomes an upflow A and rises in the reaction section 15, and then becomes a reverse flow B and descends in the reaction section 15. During this time, it is mixed with and contacted with the granule sludge 12 and the suspended activated sludge in the reaction section 15, and the organic matter is oxidatively decomposed.
[0031]
A part of the mixed liquid in the reaction unit 15 is accompanied by the granular sludge 12 and passes as a rising flow C through the gap between the lower end of the inclined separation plate 13 and the gas separation plate 14, and further inside the cylindrical rectifying plate 25. However, since the ingress of aeration air is blocked by the gas separation plate 14, the granular sludge 12 is settled and separated by the solid-liquid separation portion 16 and is rectified with the lower portion of the inclined separation plate 13. It returns to the reaction part 15 through the rectifying passage 26 formed between the outer periphery of the plate 25. The separated liquid from which the granular sludge 12 has been separated overflows, enters the treated water extraction section 27, and is discharged out of the system from the treated water channel 28 as treated water.
[0032]
According to the method of FIG. 2, a biofilm was formed on the surface of the granular sludge 12 in the reaction section 15 while efficiently sedimenting and separating the granular sludge 12 in the solid-liquid separation section 16 provided in the reaction tank 11. A large amount of aerobic microorganisms are retained, and aerobic treatment can be efficiently performed in one reaction tank.
[0033]
Although the cylindrical reaction tank 11 is used in the apparatus of FIG. 2, a rectangular reaction tank can also be used. Further, instead of the funnel-shaped inclined separator 13, an inverted funnel-shaped inclined separator having a lower end opening larger than the upper end opening is used, the gas separator is provided on the inner wall side of the reaction tank, and the outer side of the inclined separator is arranged. An apparatus having a solid-liquid separation part and a reaction part inside can also be used.
[0034]
FIG. 3 is a cross-sectional view of an aerobic treatment apparatus showing a wastewater aerobic treatment method of still another embodiment. The apparatus of FIG. 3 omits the solid-liquid separation apparatus and performs nitrification of ammonia-containing water with a single reactor.
In FIG. 3, 31 is a columnar air lift reactor, with a raw water channel 32 and an air supply channel 33 communicating with the lower part, and a treatment water channel 34 communicating with the upper part. A draft tube 35 having both ends opened is provided in the air lift reactor 31, and an air diffuser plate 36 is provided at the lower end opening so as to communicate with the air supply path 33 and diffuse into the draft tube 35. ing. From the vicinity of the upper end opening of the draft tube 35, the inner diameter of the air lift reactor 31 is increased to form a solid-liquid separation part 37, and the lower part constitutes a reaction part 38. The solid-liquid separation part 37 is provided with a gas collector 40 having a gas separation plate 39 so as to cover the upper end opening of the draft tube 35.
[0035]
In order to perform nitrification with the apparatus of FIG. 3, ammonia-containing water is introduced into the lower part of the air lift reactor 31 from the raw water channel 32, and air is sent from the air supply channel 33 and diffused from the diffuser plate 36 into the draft tube 35. . As the air rises, an upward flow is generated in the draft tube 35, and the liquid in the draft tube 35 is mixed with the granular sludge 40, the air 41 and the suspended activated sludge, and passes through the upper end opening to the outside of the draft tube 35. The liquid outside the draft tube 35 flows into the draft tube 35 from the lower end opening. In this way, an upward flow is formed in the draft tube 35 and a downward flow is formed outside the draft tube 35, and the liquid in the reactor circulates inside and outside the draft tube 35. During this time, nitrification is carried out by nitrifying bacteria that are in contact with the granular sludge 40, the air 41 and the suspended activated sludge and have formed a biofilm on the surface of the granular sludge 40.
[0036]
The internal liquid in the draft tube 35 flows upward and flows out from the upper end opening, but the solid-liquid separation part 37 has a large inner diameter, so the flow rate of the upward flow becomes small. Therefore, the granular sludge 40 is caused by its own weight. It settles, moves to the outside liquid side of the draft tube 35, and circulates through the reaction part 38. The air 41 is collected in the gas collector 40 by the gas separation plate 39 and discharged from the air discharge path 42. The treated water from which the granular sludge 40 has been separated by settling and the air 41 has been separated is discharged from the treated water channel 34.
[0037]
In the apparatus of FIG. 3, nitrifying bacteria can be retained in a large amount on the surface of the granular sludge 40 and the SRT can be lengthened to efficiently perform nitrification, and the solid-liquid separation apparatus can be omitted.
[0038]
【Example】
Example 1
The ammonia-containing water was nitrified under aerobic conditions using the apparatus shown in FIG. As the carrier, UASB granular sludge having an average particle size of 2.0 mm was used as it was. FIG. 4 shows the ammonia concentration of the inflow water flowing into the air lift reactor 31 and the daily changes in the quality of the treated water.
[0039]
Comparative Example 1
The nitrification treatment was performed in the same manner as in Example 1 except that a polypropylene sponge having a cubic shape of 3 mm square was used instead of the granular sludge in Example 1. The addition amount of the sponge was added so that the surface area of the carrier per 31 volumes of the air lift reactor was the same as in Example 1. The results are shown in FIG.
[0040]
As can be seen from the results of FIGS. 4 and 5, in Example 1 (FIG. 4) in which UASB granular sludge was added as a carrier, biofilm formation was faster than in Comparative Example 1 (FIG. 5) in which sponge was added. It was possible to shorten the startup period required to oxidize ammonia to nitric acid.
[Brief description of the drawings]
FIG. 1 is a flow sheet showing an aerobic treatment method of waste water of an example.
FIG. 2 is a cross-sectional view of an aerobic treatment apparatus showing an aerobic treatment method for wastewater according to another embodiment.
FIG. 3 is a cross-sectional view of an aerobic treatment apparatus showing a wastewater aerobic treatment method of still another embodiment.
4 is a graph showing the results of Example 1. FIG.
5 is a graph showing the results of Comparative Example 1. FIG.
[Explanation of symbols]
1 Aeration tank 2, 12, 40 Granule sludge 3 Precipitation tank 4, 21, 32 Raw water channel 5, 22, 33 Air supply channel 6, 23 Air diffuser 7 Sludge return channel 8 Communication channel 9, 28, 34 Treatment channel 10 Sludge discharge path 11 Reaction tank 13 Inclined separation plate 14, 39 Gas separation plate 15 Reaction unit 16 Solid-liquid separation unit 24 Perforated plate 25 Rectification plate 26 Rectification passage 27 Treated water extraction unit 31 Air lift reactor 35 Draft tube 36 Aeration plate 37 Solid Liquid separation unit 38 Reaction unit 40 Gas collector 41 Air 42 Air discharge path

Claims (1)

In a method of aerobic treatment of wastewater in the presence of activated sludge containing aerobic microorganisms, a carrier carrying aerobic microorganisms is charged into the reaction tank.
As a carrier supporting aerobic microorganisms, granule sludge containing anaerobic microorganisms or a crushed product thereof is put into a reaction tank and mixed with activated sludge in the tank,
By introducing the liquid to be treated into the reaction tank to which the carrier has been added and aeration,
Forming a biofilm of aerobic microorganisms on the surface of the carrier;
A method of aerobic treatment by increasing the amount of aerobic microorganisms that can be held in a reaction tank ,
An aerobic treatment method for wastewater, characterized in that granule sludge formed in methane fermentation or a crushed product thereof is used as the carrier for supporting the aerobic microorganisms .

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