JPH08173983A - Method and apparatus for fluidized bed type wastewater treatment - Google Patents

Abstract

PURPOSE: To utilize the merit of an oxygen enriched air aeration method and to attain downsizing and energy saving by fluidizing a microorganism sticking use carrier with real specific gravity within a specified range and surface- aerating using oxygen-enriched air in a closed type treatment tank. CONSTITUTION: Raw wastewater is supplied from a raw wastewater supply port 4 to a closed type aeration tank 1 packed with a microorganism sticking use carrier 10, and a surface aerator 2 and an agitator 3 are operated to fluidize the carrier uniformly. Raw wastewater is treated continuously by supplying oxygen-enriched air from an oxygen-enriched air supply port 7. The treated water is discharged from a treated water outlet 6 through a screen 5. In other words, in a closed type treatment tank 1, raw wastewater is treated by fluidizing the carrier 10 with real specific gravity of 1.03-1.10 and surface-aerating using oxygen-enriched air. In this way, BOD decomposition speed and nitration speed can be greatly increased to increase treatment quantity per unit volume.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention uses oxygen-enriched air to conserve energy in municipal sewage containing BOD components and nitrogen components, industrial wastewater, etc.
The present invention relates to a wastewater treatment technology for removing OD and nitrifying nitrogen components.

[0002]

2. Description of the Related Art Generally, as a method for treating sewage and industrial wastewater containing BOD components and nitrogen components, BOD substances are subjected to activated sludge treatment by air aeration to decompose and remove them.
The nitrogen component in the wastewater is also nitrified by treating it with activated sludge in an air aeration tank, and then anaerobic to denitrify it. However, since such a method requires a long processing time, the processing equipment is generally large in size, and a large amount of energy is required for aeration for dissolving oxygen, which also serves as stirring.

In order to make the apparatus compact, it is necessary to reduce the processing time. For this purpose, it is necessary to increase the concentration of activated sludge (microorganism concentration) and improve the oxygen dissolution rate. In order to increase the concentration of activated sludge, it has been proposed to put a microorganism-attached carrier in an air aeration tank, form an active microorganism layer on the surface of the carrier, and treat the wastewater. It has been found that this method is effective in increasing the effective microorganism concentration and is an effective means for shortening the treatment time of wastewater and improving the quality of treated water. However, increasing the concentration of active microorganisms leads to an increase in oxygen consumption per unit time. The dissolution rate of oxygen in the air aeration method is proportional to the amount of diffused gas when the concentration gradient is constant and the bubble diameter is the same, and it is necessary to increase the amount of diffused gas according to the increased oxygen consumption. Occurs. However, when the amount of diffused gas is increased, the pressure loss in the pipe increases, the bubble diameter of diffused gas increases, and the channeling of gas is easily caused. It was inevitable that the energy supply would have to be reduced and the energy efficiency would have to be reduced.

On the other hand, in order to enhance the adhesion of microorganisms to the carrier, there are also proposals for porous carriers such as pumice, cylindrical carriers having through holes, and synthetic resin particles whose surface is roughened by sandblasting. In pumice or roughened granular material, when the surface microbial layer is peeled by the collision of the carriers with each other by stirring, or the carrier and the wall, the microbial layer inside the pores does not peel, The amount of the microbial layer present inside the pores is too small, which is insufficient as a means for increasing the microbial concentration in the aeration tank and stably shortening the wastewater treatment time. Further, in a cylindrical carrier having large through holes, even if the carrier surface is unreasonable, the microbial layer grown inside the cylinder can be increased in quantity, and is not easily peeled off even under vigorous stirring,
Although the concentration of the microbial layer in the aeration tank can be maintained at a high level, the efficiency is inferior to that of the microbial layer on the surface of the carrier because it is a microorganism in the cylinder, and it is not very effective for short-time treatment. When a sponge-like porous carrier was used, it collapsed in a short-term operation and was not suitable for stable wastewater treatment.

In any case, it is necessary to use a considerably large amount of the microorganism-attached carrier in order to increase the concentration of microorganisms.
Air aeration fluidized bed system (a conceptual diagram of this system is shown in Fig. 3)
However, in order to fluidize the carrier, it is necessary to use air in an amount equal to or larger than the air diffusion amount that corresponds to the oxygen dissolution rate originally required for the decomposition of BOD components, etc., and the energy saving effect cannot be sufficiently exerted. Further, in order to reduce the amount of air, if the specific gravity of the carrier is reduced or the size of the carrier is reduced, it is not possible to evenly flow the carrier in the aeration tank, or to prevent overflow from the aeration tank. It is necessary to reduce the mesh size of the screen, which easily causes clogging and causes troubles in the subsequent process, which makes it difficult to maintain stable operation.

On the other hand, in the case of the oxygen-enriched air aeration method (a conceptual diagram of this method is shown in FIG. 4) using oxygen gas, which has become cheaper due to the technological innovation of the oxygen gas separation method, instead of air, supply oxygen-enriched air The required supply amount (oxygen concentration of about 90%) may be about 1/30 to 1/50 of the required supply air amount in the air aeration method. Therefore, it can be seen that this is a method of considerable compactification and energy saving. As a treatment method in which a carrier for adhering microorganisms is used in combination with this oxygen-enriched air aeration method, there is a proposal of a method using an activated sludge entrapping carrier using polyethylene glycol or the like. In this case (the conceptual diagram of this method is shown in FIG. 5), although the amount of activated sludge loaded on the carrier has reached a practical level, mechanical agitation can be adopted because the strength against agitation is insufficient. There wasn't. Therefore, in order to fluidize the carrier and sufficiently dissolve oxygen in the liquid, it is necessary to circulate a large amount of oxygen-enriched air in the aeration tank, making use of the excellent oxygen dissolution rate of oxygen-enriched air. Not not. In this way, sufficient technology has been completed, including the development of a total system for wastewater treatment, such as a carrier suitable for the oxygen-enriched air treatment method, a liquid-gas contact method, and a fluidization method without separation of the microbial layer adhering to the microorganism-attached carrier. I haven't.

[0007]

As described above, various problems still remain in the prior art in achieving compactness and energy saving. It is an object of the present invention to develop a fluidized bed type wastewater treatment method and apparatus using oxygen-enriched air, which makes it possible to realize the advantages of the oxygen-enriched air aeration method, compactness, and energy saving.

[0008]

According to the present invention, surface aeration is carried out by using oxygen-enriched air while flowing a carrier for adhering microorganisms having an actual specific gravity of 1.03 to 1.10 in a closed treatment tank. Fluidized bed wastewater treatment method, characterized in that the raw wastewater is treated by the method, a cylindrical carrier for adhering to microorganisms, comprising a synthetic resin and an inorganic material and having a large number of 0.1-100 μm fine pores or fine grooves on the surface. Fluidized bed type waste water treatment method, fluidized bed type waste water treatment method in which a carrier for adhering microorganisms is placed in a closed type treatment tank in an amount of 10 to 40 vol% of the amount of waste water retained in the vessel, and microorganisms are attached to a closed type waste water treatment device Fluidized bed type wastewater treatment method provided with stirring device for fluidizing carrier, raw wastewater supply port, supply port from oxygen-enriched air supply device, surface aerator, agitation device for carrier flow for microorganism adhesion, for microorganism adhesion Develop a single-stage or multi-stage closed wastewater treatment system that uses a carrier for adhering microorganisms that has a treated water outlet with a screen to prevent body outflow and a gas phase gas supply port or waste gas outlet to the next chamber. By doing so, the above object was achieved.

As the closed type treatment tank used in the present invention, a wastewater treatment apparatus used as a usual oxygen-enriched air aeration type wastewater treatment apparatus can be used. For example, raw wastewater supply port,
It has an oxygen-enriched air supply port from the oxygen-enriched air manufacturing equipment, a surface aerator, a treated water outlet and a waste gas outlet equipped with a screen for preventing the outflow of the carrier for adhering microorganisms, or a supply port to the next chamber. Closed-type wastewater treatment equipment for single-stage or multi-stage treatment can be used. In order to ensure the fluidization of the carrier and the diffusion of dissolved oxygen into the liquid even when the amount of carrier used is large to increase the concentration of microorganisms, or when the depth of water in the treatment tank is deep, a stirring device for carrier flow for adhering microorganisms is used. It is preferable to provide a coaxial deep stirring blade on the surface aerator or separately provide a stirring device for fluidizing the carrier.

The carrier for adhering microorganisms used in the present invention has a specific gravity, size and shape suitable for flow and capable of easily preventing outflow without causing clogging of screens and the like. It has strength that does not cause crushing, deformation, abrasion, etc. due to stirring and the like, and also has flexibility. It has the ability to retain microorganisms so that the supported microorganisms do not peel off or fall off due to stirring, mutual contact of carriers, and the like. The amount of microorganisms supported per unit volume of carrier is large. It is necessary to have requirements such as.

The specific gravity that allows the carrier to flow was 1.2 or less when the stirring strength required for oxygen dissolution using oxygen-enriched air was such that the carrier surface microbial layer was not separated. In addition, carriers having a specific gravity of less than 1.03 tended to collect near the surface of the liquid in the treatment tank. From the above results, the specific gravity is 1.03 to 1.10
Was chosen. The smaller the carrier size, the larger the surface area per carrier filling volume. From this aspect, the smaller the better, but with a typical diameter of 5 mmφ or less, the outflow prevention screen also becomes 5 mm or less, and problems such as clogging are likely to occur. If it is too large, the fluidity deteriorates, so the typical diameter of the carrier is 5 to 30 mmφ, preferably 7 to 25 mmφ. As a shape, a large amount of microorganisms are retained, and a large number of micropores of 0.1 to 100 μm suitable for adsorption and growth of microorganisms and //
Or a cylindrical one having a narrow groove, in particular, by combining the microbial layer adhered to the outer cylinder surface with the microbial layer adhered to the inner surface of the cylinder, the micropores are penetrated in order to enhance the retention of the microbial layer. It is preferable that the cylindrical shape is easy to manufacture and excellent in performance.

The material of the carrier includes specific gravity, size, strength,
It is preferable to combine a synthetic resin and an inorganic material in terms of flexibility, surface condition, moldability and the like. As the synthetic resin, a flexible and lightweight polyolefin general-purpose thermoplastic synthetic resin such as polyethylene or polypropylene is used, and as the inorganic material, calcium carbonate, talc, barium sulfate, zeolite or the like is used. Specific gravity of synthetic resin is 1.0 g / cm ³
Since these are the followings, these inorganic materials are combined for the purpose of adjusting the specific gravity of the synthetic resin, roughening the surface of the carrier, and imparting hydrophilicity. In particular, in order to form a large number of fine holes and fine grooves in the material and form a strong microbial retention layer, at the time of molding
It is preferable to use a foaming agent together for the purpose of roughening the surface of the carrier and adjusting the specific gravity. The oxygen-enriched air to be used may be high-purity oxygen such as oxygen liquefied and separated, but economically, oxygen gas having a concentration such as PSA using a zeolitic molecular sieve (70 vol% or more, preferably 90 vol% or more).

Since there is almost no difference in carrier performance due to the material combination of the synthetic resin and the inorganic substance, the mixing ratio is adjusted so that the specific gravity and the surface state fall within the target ranges. However, as the proportion of inorganic substances increases, it becomes easier to break, so
A mixing ratio within the range of the specific gravity is also suitable from the viewpoint of strength. The surface state of the carrier has a great influence on the amount of microorganisms supported per unit volume of the carrier and the ability to retain the microorganisms with respect to stirring and the like. It is possible to control the size and distribution of pores on the surface of the carrier, and the size and number of through-holes from the inner surface to the outer surface of the cylindrical carrier, depending on the conditions at the time of molding the carrier (drawing speed, type and amount of blowing agent, etc.) I found it. In addition,
The shape of the carrier is preferably cylindrical in terms of processability and surface state controllability, but is not particularly limited.

As the screen for preventing carrier outflow, a screen having a mesh as large as possible is used as long as the carrier does not pass through in order to prevent clogging of the screen. At the time of operation, the amount of the microorganism-attached carrier used is 10 to 10% of the amount of waste water retained in the tank.
40 vol%, preferably 20 to 35 vol% is added. It is preferable to operate so that the oxygen concentration in the gas phase portion of the closed type treatment layer is maintained at least 30 vol%, and preferably 50 vol% or more. In the case of multi-stage treatment, either countercurrent flow or cocurrent flow may be used, but the oxygen concentration in the final stage treatment tank is at least 25 vol%, preferably 40 vo
It is preferable to operate so as to maintain 1% or more.

[0015]

The purpose of the wastewater treatment of the present invention is to compact the equipment by a short-time treatment, and in the method of using a microorganism-attached carrier to increase the concentration of microorganisms, high oxygen consumption is achieved even under the condition that gas-liquid contact is moderated. Using oxygen-enriched air that can respond to the speed and ensuring sufficient flow of the carrier even if the contact of gas and liquid is loosened, while preventing the detachment of the microbial layer adhered and grown on the carrier surface, more active microorganisms The purpose is to secure activities. This means that oxygen is mainly dissolved by the surface aeration method (of course, oxygen-enriched air or circulating oxygen-containing gas may be supplied below the surface of the water). By using such mechanical agitation together, efficient wastewater treatment becomes possible even in special cases such as when the liquid depth of the treatment tank is deep. The method of the present invention enables a more efficient operation by replacing the aeration tank of the conventional wastewater treatment apparatus using oxygen-enriched air (for example, the UNOX system) as it is.
In particular, it has a feature that nitrification can be efficiently performed by activated sludge treatment in the treatment of wastewater having a high total nitrogen content.

[0016]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing an example of an oxygen-enriched air aeration method fluidized wastewater treatment method using the carrier of the present invention. Aeration tank 1 is 100
0mm x 1000mm, height 1000mm closed type,
Surface aerator 2, coaxial carrier flow agitator 3, raw wastewater supply port 4, treated water outlet 6 with a screen 5 having an opening of 8 mm, oxygen-enriched air supply port 7, waste gas outlet 8 ing. The carrier 10 for adhering microorganisms is as shown in FIG. 2, and is made of a composition of polyethylene and polypropylene and calcium carbonate, and has a specific gravity of about 1.05 and an outer diameter of about 10 mm.
It is a porous cylindrical carrier of φ, inner diameter of about 8 mmφ, and length of about 10 mm. There are innumerable micropores and fine grooves of about 1 to 100 μm on the inner and outer surfaces of the cylinder, and penetration of about 100 to 500 μm holes inside and outside the cylinder. There are some holes.

About 30 vol% of this carrier for adhering microorganisms
Raw wastewater is supplied from the raw wastewater supply port 4 to the sealed aeration tank 1 (210 liters) at a rate of 350 liters / hr, and the surface aerator 2 and the agitator 3 are activated to uniformly fluidize the carrier. Next, oxygen-enriched air (oxygen concentration of about 90
%) Through the oxygen-enriched air supply port 7 to continuously treat the raw wastewater. The treated water passes through the screen 5 and is discharged from the treated water outlet 6. The raw wastewater treatment conditions are as follows. Aeration tank effective inner volume 700 liters Raw wastewater supply amount 350 liters / hr Oxygen-enriched air supply amount 100 liters / hr Stirring power 50w Table 1 shows the treatment conditions of raw wastewater, the composition of raw wastewater and the treatment for 4 months continuous treatment. The composition of the treated wastewater after reaching equilibrium is shown.

[Comparative Example 1] No carrier for adhering microorganisms was added to the treatment tank, and the concentration of microorganisms in the treatment tank was about 4000 m.
The apparatus and processing conditions were the same as in the example except that the returning microorganisms were circulated to maintain g / l. Table 1 shows treatment conditions, composition of raw wastewater, and composition of treated water after continuous treatment for 4 months.

[Comparative Example 2] The same apparatus and treatment conditions as in Comparative Example 1 were used, except that the raw wastewater supply rate was lowered so that the concentration of NH ₄ -N in the treated water was almost the same as in Example 1. Table 1 shows treatment conditions, composition of raw wastewater, and composition of treated water after continuous treatment for 4 months.

[0020]

[Table 1]

[0021]

The oxygen-enriched air fluidized-bed wastewater treatment method using the microorganism-attached carrier according to the present invention is not limited to the air aeration-type wastewater treatment method, but is also a conventional method such as the conventional oxygen-enriched air wastewater treatment method. The BOD decomposition rate and the nitrification rate can be remarkably increased as compared with the above, and the treatment amount per unit volume of the treatment tank can be increased. Although not particularly shown as data, not only is the activated sludge concentration in the treatment tank high due to the use of the carrier for adhering microorganisms, the BOD is low and the ammoniacal nitrogen is low in spite of the short treatment time, The ability to maintain a high dissolved oxygen concentration (DO) in the treated water and the excellent settability of activated sludge in the settling tank,
It is an energy-saving, compact device and a wastewater treatment method with excellent performance. INDUSTRIAL APPLICABILITY The present invention has solved all the problems of wastewater treatment to be solved, and was able to provide an extremely compact wastewater treatment apparatus and method with low equipment costs and operating costs.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the present invention.

FIG. 2 is a schematic view showing one example of the carrier used in the present invention.

FIG. 3 is a conceptual diagram of a conventional air aeration flow tank system.

FIG. 4 is a conceptual diagram of a conventional oxygen-enriched air aeration system.

FIG. 5 is a conceptual diagram of an oxygen-enriched air aeration system using a conventional activated sludge entrapping carrier.

[Explanation of symbols]

 1 Treatment Tank 2 Surface Aerator 3 Stirrer for Flowing Carrier for Microorganism Adhesion 4 Raw Wastewater Supply Port 5 Screen 6 Treated Water Outlet 7 Oxygen-enriched Air Supply Port 8 Waste Gas Outlet 10 Microbe Adhesion Carrier 11 Air Diffuser 12 Air Supply pump

Claims (5)

[Claims] 1. An actual specific gravity of 1.0 in a closed processing tank.
A fluidized bed wastewater treatment method, characterized in that the raw wastewater is treated by aerating the surface with oxygen-enriched air while flowing the carrier for adhering microorganisms of 3 to 1.10. 2. A fluidized bed wastewater treatment system according to claim 1, wherein a cylindrical carrier for adhering to microorganisms, which is made of a synthetic resin and an inorganic material and has a large number of micropores or fine grooves of 0.1 to 100 μm on its surface, is caused to flow. Method. 3. The fluidized bed wastewater treatment method according to claim 1, wherein the carrier for adhering microorganisms is put in a closed type treatment tank in an amount of 10 to 40 vol% of the amount of wastewater retained in the tank and allowed to flow. 4. The fluidized bed wastewater treatment method according to claim 1, wherein the closed wastewater treatment device is provided with a stirring device for causing the carrier for adhering microorganisms to flow. 5. A treatment provided with a raw wastewater supply port, a supply port from an oxygen-enriched air supply device, a surface aerator, a stirring device for flowing a carrier for adhering microorganisms, and a screen for preventing the carrier for adhering microorganisms from flowing out. A one-stage or multi-stage closed wastewater treatment device using a carrier for adhering microorganisms, which has a water outlet and a gas phase gas supply port or a waste gas outlet to the next chamber.