JP2002336885A - Method for aerobic treatment of waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for aerobic treatment of waste water so that the water can be efficiently treated at a low cost by using a carrier the preparation of which is free of cost or causes no problems of disposal and on which a microbial film is fast formed. SOLUTION: Granule sludge 2 discharged from the reactor by the UASB(upflow anaerobic sludge blanket) method is introduced as a carrier into an aeration tank 1 to form an aerobic microbial film on the surface of the granule sludge 2. Then raw water is introduced from a raw water passage 4 into the aeration tank 1 and mixed with the granule sludge 2, returned sludge from a sludge returning passage 7, and floating active sludge in the aeration tank 1. The mixture is aerated by supplying air from an air supply passage 5 and diffusing air from a diffusing device 6 to carry out the aerobic treatment. The mixture liquid in the aeration tank 1 is partly discharged and introduced into a settling tank 3 to separate the solid from the liquid. The separated liquid is discharged as treated water from a treated water passage 9 while the separated sludge is returned as the returned sludge through the sludge returning passage 7 to the aeration tank 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aerobic treatment method for wastewater.

[0002]

2. Description of the Related Art An aerobic biological treatment method, such as an activated sludge treatment method, in which an organic effluent is treated under aerobic conditions by utilizing the action of an aerobic microorganism, has a low treatment cost and a high treatment performance. It is widely used because of its superiority. In such an aerobic treatment method, a carrier is introduced for the purpose of increasing the holding amount of the aerobic microorganisms in the aeration tank or extending the residence time, and a sponge, plastic, polymer, or the like is used as the carrier. Gels and the like 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 a high concentration of sludge can be retained in the aeration tank.

[0003] However, the conventionally used carrier has a problem in that the production cost of the carrier itself is high and the processing cost is high. Further, depending on the properties of the carrier surface, it takes a long time until a film of aerobic microorganisms is formed, and therefore, it may take a long time to start up the operation. Further, when the carrier material is an artificial product such as plastic, there is a problem of disposal.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems in the conventional carrier addition method, so that the production cost of the carrier itself is not required, the formation of the microorganism membrane is fast,
It is an object of the present invention to propose an aerobic treatment method for wastewater that can be efficiently treated at low cost by using a carrier having no problem of disposal.

[0005]

The present invention is the following aerobic treatment method for wastewater. (1) In a method in which a carrier carrying an aerobic microorganism is charged into a reaction tank and the wastewater is subjected to aerobic treatment in the presence of activated sludge containing the aerobic microorganism, an anaerobic microorganism is used as a carrier carrying the aerobic microorganism. An aerobic treatment method for wastewater, characterized by using granulated sludge or a crushed product thereof. (2) The aerobic treatment method for wastewater as described in (1) above, wherein granule sludge formed in methane fermentation or a crushed product thereof is used as a carrier for supporting aerobic microorganisms.

The waste water to be treated in the present invention is:
There is no limitation as long as the wastewater can be treated by aerobic biological treatment, and examples thereof include organic wastewater and ammonia-containing wastewater. The organic effluent may contain a hardly biodegradable organic or inorganic substance, or 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 granular sludge obtained by sludge containing anaerobic microorganisms granulated by the self-granulating action of microorganisms or a crushed product thereof. Such granulated sludge includes UASB (Upflow Ana).
erobic Sludge Blanket; Upflow anaerobic sludge blanket method or EGSB (Ex
Pounded Granular Sludge Be
d: Expanded granular sludge bed) Granulated sludge formed in a reactor in which methane fermentation is carried out by the method, and granular sludge discharged from these reactors. Usually, these granulated sludges have good sedimentation properties.

In the UASB or EGSB method,
Organic acid fermentation and methane fermentation are usually performed in separate reactors,
The methane fermentation is carried out by passing the acid product liquid from the organic acid fermentation in an upward flow through a UASB methane fermentation tank in which a sludge blanket made of granular sludge is formed,
In the present invention, the granular sludge formed by the two-phase methane fermentation in which the organic acid fermentation and the methane fermentation are separated into two stages as described above is preferable, but the organic acid fermentation and the methane fermentation are performed in a single reactor. Granular sludge formed in the one-phase methane fermentation performed can also be used.

The granular sludge used in the present invention does not need to be granulated sludge granulated by selecting a special apparatus, operation, conditions and the like, and methane fermentation is generally performed by a known method. Granule sludge generated in the treatment system can be used as it is. For example, any of high temperature methane fermentation and medium temperature methane fermentation may be used.

[0010] Granular sludge formed by the usual UASB and EGSB methods has a skeleton formed by a microorganism of the genus Methanosaeta capable of assimilating acetic acid. , Constitute a kind of ecosystem. In addition, acid-producing bacteria that degrade carbohydrates, lipids, proteins, etc., produce mucilage and work to strengthen the binding force between bacteria, and when sugar substrates are used, the strongest granular sludge is formed. Is done. Normal sewage and other organic wastewater contains saccharides and other high-molecular organic substances, and when this is anaerobically treated, the above-described anaerobic microorganisms produce organic acids, which are successively reduced in molecular weight. It becomes acetic acid and is further decomposed into methane and carbon dioxide gas. For this reason, the above-mentioned various anaerobic microorganisms proliferate and form granular sludge having high strength.

Although the growth process of granulated sludge in the UASB and EGSB methods is not clear, anaerobic microorganisms are present on the surface of minute inorganic SS with a particle size of about 0.1 mm and the surface of scale components containing calcium and magnesium. New anaerobic microorganisms grow and adhere in the form of annual rings with small SSs and scales as nuclei, and grow into granular sludge with an average particle size of 0.3 to 5 mm over several months. It has been done. It is said that the grown granule sludge is crushed by a flow caused by the flow of water and gas in the reaction tank, and the crushed fine particles and fragments become nuclei, and the next granule sludge grows.

In the present invention, the granular sludge used as a carrier has an average particle size of about 0.3 to 5 mm,
It is preferably 0.5 to 2 mm, but granules crushed by a crushing device such as a cutter pump, a mill, and a homogenizer can also be used.

In aerobic treatment using a carrier, diffusion of oxygen may be the main rate-determining step. The depth of oxygen permeation into the biofilm is about 100 μm at the maximum in the case of aeration using ordinary air. To handle high loads, increase the surface area or increase the oxygen partial pressure in the aeration gas. Need to be done. In order to increase the surface area of the carrier, it is effective to reduce the size of the carrier, and from this point, crushing is performed rather than using granule sludge that exceeds the average particle size as it is, and the particle size is reduced. To increase the surface area. In addition, granule sludge having a large particle diameter has voids formed therein and may have reduced sedimentation properties. Therefore, it is preferable to use such granule sludge by crushing.

The carrier is used by being charged into a reaction tank such as an aeration tank. The aerobic microorganisms form a biofilm on the surface of the carrier by introducing the carrier into the reaction tank, mixing with the activated sludge in the tank, and performing aerobic treatment. The formation of the biofilm is spontaneously formed by performing the same operation as the usual aerobic biological treatment in which the liquid to be treated is introduced into the reaction tank to which the carrier is added and aerated. Biotreated sludge can also be introduced as a seed source to promote biofilm formation. In addition, aerobic microorganisms that formed a film on the carrier partially exfoliated by growth,
It becomes floating activated sludge. The addition amount of the carrier, the reaction vessel 1 m ³ per 5 to 80 vol%, preferably desirably 10 to 50 vol%.

[0015] The treatment method of the present invention can be carried out by employing a known aerobic treatment method in a state where the carrier is charged in a reaction tank. Any reactor can be used as a reaction tank in the aerobic treatment. As the solid-liquid separator, a sedimentation tank, a membrane separator, a centrifuge, and the like can be used. Further, an aerobic treatment apparatus in which a GSS (gas solids separator) is provided in the reaction tank and aerobic treatment and solid-liquid separation are performed in one reaction tank may be adopted. By performing the aerobic treatment with the carrier charged, the amount of aerobic microorganisms that can be held in the reaction tank can be increased, and the treatment efficiency and treated water quality can be improved. As a specific aerobic treatment, a standard activated sludge method in which wastewater is aerated together with return sludge in an aeration tank, aerated liquid is separated into solid and liquid in a solid-liquid separation tank, and a part of the separated sludge is returned to the aeration tank. , And various modifications thereof can be employed.

Since granulated sludge has a higher sedimentation speed than ordinary floc, granule sludge can be added to a dispersion type aeration tank having an aeration tank and a sedimentation tank so that floc and a carrier can 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 residence time can be extended, and the amount of excess sludge can be reduced and the quality of treated water can be improved.

In the present invention, since granular sludge, which is originally a mass of microorganisms, is used as a carrier, the affinity between the carrier and the microorganisms is very good. Therefore, the biofilm formation rate is lower than that of an artificial carrier. Be faster. In the present invention, since such a carrier is used, the operation start-up period can be shortened. Further, in the present invention, since excess granule sludge generated in the anaerobic treatment can be used as it is, the production cost of the carrier is not required, and the treatment can be performed at low cost.

Further, in the present invention, since the granular sludge is a mass of anaerobic microorganisms, the amount of the carrier in the reaction tank can be controlled in the same manner as in ordinary anaerobic treatment operation. Since the extracted carrier does not contain any artificial matter, it can be treated by ordinary excess sludge treatment, for example, dehydration, anaerobic digestion, compost, etc., and when it is treated as waste, it is disposed of as excess sludge of biological origin. it can.

In the long-term operation, it is conceivable that the granular sludge is destroyed and flows out into the treated water as SS. However, since the carrier itself is derived from microorganisms, the load on the environment is limited to that of ordinary aerobic sludge. It is no different from a spill.
Further, when the amount of the carrier in the reaction tank decreases due to outflow or the like, granule sludge can be additionally charged.

In the present invention, the SRT of the activated sludge can be extended by adding a carrier, for example, to 10 days or more, so that nitrifying bacteria can be retained. In addition to decomposing organic matter,
Nitrification can be performed simultaneously, which is advantageous when performing biological nitrification denitrification treatment.

As described above, in the present invention, granule sludge is used as a carrier for supporting aerobic microorganisms, so that the following effects can be obtained. 1) Good adhesion to the carrier, 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 waste can be disposed of 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 treatment apparatus can be improved by combining with the suspended sludge.

[0022]

According to the aerobic treatment method for wastewater of the present invention, as a carrier for supporting aerobic microorganisms, granular sludge containing anaerobic microorganisms or a crushed product thereof is used. In addition, wastewater can be efficiently aerobic-treated at low cost by using a carrier that quickly forms a microbial membrane and has no disposal problem.

[0023]

Embodiments of the present invention will be described below. FIG. 1 is a flow sheet showing an aerobic treatment method for organic wastewater of an example. In FIG. 1, 1 is an aeration tank,
2 is a granular sludge as a carrier, and 3 is a settling tank.

In the processing method shown in FIG. 1, at the start of operation, raw water is introduced into the aeration tank 1 from the raw water channel 4, granulated sludge 2 is charged, air is sent from the air supply channel 5, and the air diffuser 6 is started. And aeration is performed to form a biofilm of aerobic microorganisms on the surface of the granular sludge 2. In this case, the biofilm can be formed spontaneously, or the biofilm formation can be promoted by introducing biologically treated sludge from another treatment system as a seed source. Granule sludge 2 has a very good affinity for microorganisms and has a high biofilm generation rate, so that 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, A transition can be made to the steady state early.

In a steady state after a biofilm of aerobic microorganisms is formed on the surface of the granular sludge 2, raw water is introduced from the raw water channel 4 into the aeration tank 1, and the granular sludge 2,
Returned sludge returned from the sludge return path 7 and the aeration tank 1
It mixes with the floating activated sludge in the inside, sends air from the air supply path 5, diffuses air from the diffuser 6 to perform aeration, and performs aerobic treatment. At this time, the granular sludge 2 flows in the aeration tank 1.

The mixed solution in the aeration tank 1 is partly taken out and introduced into the settling tank 3 through the communication line 8 to perform solid-liquid separation. The separated liquid is discharged as treated water from the treated water passage 9, and the separated sludge including the granular sludge 2 and the suspended activated sludge is discharged to the sludge return passage 7.
Is returned to the aeration tank 1 as return sludge. Granule sludge 2 has good sedimentation property, and solid-liquid separation is performed well. The remaining part is discharged out of the system from the sludge discharge passage 10 as surplus sludge. When the granular sludge 2 in the aeration tank 1 decreases due to outflow or the like, the granular sludge 2 is additionally charged into the aeration tank 1.

By performing the aerobic treatment in this manner, the aerobic microorganisms are filled with the granular sludge 2 in the aeration tank 1.
The aerobic treatment performance is carried out efficiently, and high-quality treated water is obtained. Also, for any reason, when SS such as granulated sludge 2 flows out into the treated water, the granulated sludge 2 is derived from microorganisms. It does not change at all.

In FIG. 1, granular sludge on which a biofilm has already been formed can be charged, and granular sludge is charged into an aeration tank in which aerobic treatment is performed in a steady state without using a carrier. You can also. In FIG. 1, a membrane separation device or another sludge separation device can be used instead of the sedimentation tank 3.

FIG. 2 is a sectional view of an aerobic treatment apparatus showing an aerobic treatment method for organic waste water according to another embodiment. The apparatus shown in FIG. 2 is an apparatus that performs aerobic treatment of organic wastewater in one reaction tank by omitting a solid-liquid separation device by utilizing good sedimentation of granular sludge. In FIG. 2, reference numeral 11 denotes a reaction tank, 12 denotes granule sludge as a carrier, and a funnel-shaped inclined separating plate 13 is provided at the upper part of the tank, and a cap-shaped gas separating plate 14 is provided at the lower part thereof so as to substantially close the opening. The inside of the tank is partitioned into a reaction section 15 and a solid-liquid separation section 16, and aerobic treatment is performed in the reaction section 15, and the solid-liquid separation section 16 is provided.
Is used to settle and separate the granular sludge 12. The inclined separation plate 13 and the gas separation plate 14 constitute a gas solid content separator.

In the aerobic treatment using the apparatus shown in FIG. 2, raw water is introduced into the lower part of the reaction tank 11 from the raw water channel 21, air is sent from the air supply channel 22, and air is diffused from the air diffuser 23 to perform aeration. Do. The raw water passes through the perforated plate 24 and becomes the upward flow A and rises in the reaction section 15, and then becomes the reverse flow B and descends in the reaction section 15. During this time, the granular sludge 12 and the floating activated sludge in the reaction section 15 are mixed and contacted, and the organic matter is oxidatively decomposed.

A part of the mixed liquid in the reaction section 15 is accompanied by the granular sludge 12, passes through the gap between the lower end of the inclined separation plate 13 and the gas separation plate 14 as an upflow C, and further flows into a cylindrical rectifying plate 25. The granulated sludge 12 is settled and separated in the solid-liquid separation unit 16 because the inflow of aerated air is blocked by the gas separation plate 14, It returns to the reaction part 15 through the rectifying passage 26 formed between the lower part and the outer periphery of the rectifying plate 25.
The separated liquid from which the granular sludge 12 has been separated overflows into the treated water extracting section 27, and is discharged as treated water from the treated water passage 28 to the outside of the system.

According to the method shown in FIG. 2, while the granular sludge 12 is settled and separated efficiently by the solid-liquid separation unit 16 provided in the reaction tank 11, the granular sludge 12
A large amount of aerobic microorganisms having a biofilm formed on the surface thereof can be retained, and aerobic treatment can be performed efficiently in a single reaction tank.

Although the cylindrical reaction tank 11 is used in the apparatus shown in FIG. 2, a rectangular reaction tank can be used. Further, instead of the funnel-shaped inclined separating plate 13, an inverted funnel-shaped inclined separating plate having a lower end opening larger than the upper end opening is used, a gas separating plate is provided on the inner wall side of the reaction vessel, and the outside of the inclined separating plate is provided. It is also possible to use an apparatus having a solid-liquid separation section and a reaction section inside.

FIG. 3 is a sectional view of an aerobic treatment apparatus showing an aerobic treatment method for wastewater according to still another embodiment. The apparatus in FIG. 3 is an apparatus in which the solid-liquid separation device is omitted and nitrification of the ammonia-containing water is performed in one reactor. In FIG. 3, 3
Reference numeral 1 denotes a column-shaped air lift reactor, in which a raw water passage 32 and an air supply passage 33 communicate with each other at a lower portion, and a treated water passage 3 at an upper portion.
4 are in contact. A draft tube 35 having both ends opened is provided in the air lift reactor 31, and a diffuser plate 36 is provided at the lower end opening to communicate with the air supply path 33 and to 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 increases, and the solid-liquid separation section 3
7 is formed, and the lower part thereof constitutes the reaction part 38. The solid-liquid separator 37 is provided with a gas collector 40 having a gas separation plate 39 so as to cover the upper opening of the draft tube 35.

To perform nitrification using the apparatus shown in FIG.
The ammonia-containing water is introduced into the lower portion of the air lift reactor 31 from above, and air is sent from the air supply path 33 to diffuse air from the diffuser plate 36 into the draft tube 35. As the air rises, an ascending flow is generated in the draft tube 35, and the liquid in the draft tube 35 becomes granular sludge 4.
0, mixed with air 41 and floating activated sludge, flows out of the draft tube 35 through the upper end opening, and the liquid outside the draft tube 35 flows into the draft tube 35 from the lower end opening. In this way, an ascending flow is formed inside the draft tube 35 and a descending 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 performed by the nitrifying bacteria that have come into contact with the granular sludge 40, the air 41 and the floating activated sludge and have formed a biofilm on the surface of the granular sludge 40.

The internal liquid of the draft tube 35 flows out from the upper end opening as an upward flow. However, since the inner diameter of the solid-liquid separating section 37 is wide, the flow velocity of the upward flow is small, and as a result, the granular sludge 40 Is settled by its own weight, moves to the outside liquid side of the draft tube 35, and circulates through the reaction section 38. The air 41 is collected by the gas collector 40 by the gas separation plate 39 and discharged from the air discharge passage 42. The treated water from which the granular sludge 40 is settled and separated and the air 41 is separated is discharged from the treated water channel 34.

In the apparatus shown in FIG. 3, a large amount of nitrifying bacteria can be retained on the surface of the granular sludge 40, and the SRT can be lengthened to efficiently perform nitrification, and the solid-liquid separation device can be omitted. .

[0038]

EXAMPLE 1 Nitrification treatment was performed on ammonia-containing water under aerobic conditions using the apparatus shown in FIG. UASB granular sludge having an average particle size of 2.0 mm was used as a carrier as it was. FIG. 4 shows the ammonia concentration of the inflow water flowing into the air lift reactor 31 and the daily change of the treated water quality.

Comparative Example 1 In Example 1, 3 mm was used instead of the granular sludge.
The nitrification treatment was performed in the same manner as in Example 1, except that a sponge made of polypropylene having a corner cube shape was used. 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.
FIG. 5 shows the results.

As can be seen from the results of FIGS. 4 and 5,
In Example 1 (FIG. 4) in which UASB granular sludge was charged as a carrier, Comparative Example 1 in which sponge was charged (FIG. 5)
The formation of a biofilm was faster than that of, and the start-up period required to oxidize ammonia to nitric acid could be shortened.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing an aerobic treatment method for wastewater of an example.

FIG. 2 is a cross-sectional view of an aerobic treatment device showing an aerobic treatment method for wastewater according to another embodiment.

FIG. 3 is a cross-sectional view of an aerobic treatment apparatus showing an aerobic treatment method for wastewater according to still another embodiment.

FIG. 4 is a graph showing the results of Example 1.

FIG. 5 is a graph showing the results of Comparative Example 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Aeration tank 2,12,40 Granule sludge 3 Sedimentation 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 water 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 Rectifying plate 26 Rectifying passage 27 Treated water extraction unit 31 Air lift reactor 35 Draft tube 36 Diffusion plate 37 Solid Liquid separation unit 38 Reaction unit 40 Gas collector 41 Air 42 Air exhaust passage

Claims (2)

[Claims] Claims: 1. A method of introducing a carrier carrying an aerobic microorganism into a reaction tank and subjecting the wastewater to aerobic treatment in the presence of activated sludge containing the aerobic microorganism, wherein the carrier carrying the aerobic microorganism is anaerobic. An aerobic treatment method for wastewater, comprising using granular sludge containing bacterium or a crushed product thereof. 2. The aerobic treatment method for wastewater according to claim 1, wherein the carrier carrying the aerobic microorganisms is granular sludge formed in methane fermentation or a crushed product thereof.