CN101374771A - Method for treating waste water by using immobilized carrier - Google Patents

Abstract

The invention relates to a drainage treatment method adopting an immobilized carrier. In order to provide a method for treating wastewater which can reduce the overall size of a tank and which is less in the amount of excess sludge to be withdrawn and is inexpensive, an aeration tank (1) for allowing wastewater to contact granular carriers under aerobic conditions, a total oxidation tank (3) for reducing the capacity of sludge generated in the aeration tank (1) under aerobic conditions, and a solid-liquid separation apparatus for sludge in the total oxidation tank are used, and the method comprises the steps of setting the self-oxidation coefficient of sludge flowing into the total oxidation tank (3) to 0.05 (1/day) or more, and adding a flocculant to the total oxidation tank (3) so as to improve the solid-liquid separation property of the sludge in the total oxidation tank.

Description

Drainage treatment method using immobilized carrier

technical field

The present invention relates to a drainage treatment method using an advanced treatment technology of drainage using an immobilized carrier.

Background technique

In the past, wastewater treatment mainly used the activated sludge method. According to the activated sludge method, the sludge is settled in the sedimentation tank, part of it is returned to the aeration tank, and part of it is extracted as excess sludge, which can be used at a BOD volume load of 0.3-0.8kg/(m ³ ·day) Constant operation is performed under conditions within the range (for example, refer to Non-Patent Document 1). On the other hand, development of carriers capable of retaining microorganisms at high concentrations is underway. If this carrier is used, a high BOD volume load of 2 to 5 kg/m ³ ·day can be applied, and the size of the aeration tank can be reduced (see, for example, Non-Patent Document 2).

集委員会

、“五訂·公害防止の技術と法规(水質

)”、產業環境管理協会

行、第7版、平成13年6月12日、P197Non-Patent Document 1: Pollution Prevention Technology and Regulations

Assembly Committee

, "Five Regulations Pollution Prevention Technology and Regulations (Water Quality

)”, Industry Environmental Management Association

Line, 7th edition, June 12, 2013, P197

物

理

合技術ガイド”、工業調查会、平成14年2月12日

行、p.70Non-Patent Document 2: "Environmental preservation and waste

thing

reason

Co-Technology Guido", Industrial Survey Committee, February 12, 2014

OK, p.70

Patent Document 1: Japanese Patent Laid-Open No. 2001-205290

Patent Document 2: Japanese Patent Laid-Open No. 2001-347284

Contents of the invention

In the conventional activated sludge method, it was necessary to operate under the condition that the BOD volume load was in the range of 0.3 to 0.8 kg/(m ³ ·day), and it was necessary to use a large aeration tank. In the activated sludge method, when the operation with high BOD volume load is carried out, the treatment is insufficient, or the settleability of the sludge is reduced, and the separation of the sludge in the subsequent settling tank is difficult, and it is difficult to continue the stable operation. In addition, in the conventional activated sludge method, about 50% of the removed BOD is converted into sludge (excess sludge), and final treatment such as pumping out of the system, landfill after dehydration, and incineration must be required. In addition, if the sludge is not pumped out, by forming a fully oxidized state in which the speed of sludge proliferation and the speed of sludge oxidation itself are balanced, theoretically, a system that does not generate excess sludge can be formed. However, if The fully oxidized state is formed in the activated sludge tank, and since the MLSS of the aeration tank is very high, there is a disadvantage that a very large activated sludge tank must be installed. In addition, in this case, there arises a problem that the sludge becomes finer and the separation of the sludge by natural sedimentation cannot be realized.

People have proposed the following operation, wherein, if the sedimentation and separation of the sludge cannot be achieved, since the treated water cannot be discharged, the BOD sludge load of the activated sludge tank is 0.08～0.2kg-BOD/(kg-SS· day) to apply a load to the activated sludge to improve the settleability of the sludge. However, in the case of the above method of applying a load, it is difficult to reduce the extraction amount of excess sludge (see Patent Documents 1 and 2).

The object of this invention made|formed in view of the above-mentioned subject is to provide the waste water treatment method which can reduce the size of a tank, and can extract less excess sludge, and is cheap.

The wastewater treatment method of the present invention that solves the above-mentioned problems adopts an aeration tank in which the discharged water contacts a granular carrier under aerobic conditions, a total oxidation tank in which the volume of sludge generated in the aeration tank is reduced under aerobic conditions, A solid-liquid separation device for sludge in a total oxidation tank, the method includes setting the self-oxidation coefficient of the sludge flowing into the above-mentioned total oxidation tank at more than 0.05 (1/day), and adding a flocculant in the total oxidation tank to improve The solid-liquid separation step of the total oxidation tank sludge.

In the total oxidation tank, by aerating with a lower sludge load, the proliferation of sludge and the oxidation rate of sludge itself can be balanced to prevent the increase of sludge. Here, in the case of using activated sludge in the aeration tank, since the volume of the aeration tank increases as mentioned above, and the self-oxidation coefficient of the sludge flowing into the total oxidation tank is very small, it is necessary to make the sludge In the case of a balance between proliferation and the oxidation speed of the sludge itself, the volume of the total oxidation tank must be 2 to 6 times that of the case where the carrier is used in the aeration tank. As the reason for the low self-oxidation coefficient of activated sludge, it is considered that in activated sludge, there are protozoa whose self-oxidation coefficient is smaller than that of bacteria, and the cohesive substances produced in order to aggregate the bacterial community are composed of small self-oxidation coefficients. Polymer composition. In this way, by using a carrier in the aeration tank, the aeration tank and the total oxidation tank can be made compact, but since the sludge generated in the aeration tank contains very little protozoa and adhesive substances, it is Dispersion, unnatural sedimentation, and thus, the problem of difficulty in separation of sludge in sedimentation tanks or membrane filtration devices arises. In wastewater treatment, it is widely known that the addition of a flocculant improves solid-liquid separation. However, the present inventors found that in a wastewater treatment method set according to specific conditions, by adding a predetermined amount of flocculant, The present invention has been accomplished by achieving not only downsizing of the facility and improvement of solid-liquid separation, but also a significant reduction in the amount of sludge pumped out. What is even more surprising is that, according to the present invention, compared with the known flocculant addition methods in the past, the purpose can be achieved by adding a very small amount of flocculant.

According to the present invention, the overall size of the tank can be reduced, and the amount of excess sludge extracted is very small, enabling low-cost wastewater treatment.

Description of drawings

The present invention will be more clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. However, the examples and drawings are merely for illustration and description, and should not be used to determine the scope of the present invention. The scope of the present invention is determined by the scope of the appended claims. In the drawings, the same reference numerals in a plurality of drawings represent the same part.

Fig. 1 is the figure that represents the flow process of embodiment 1, 4～6 and comparative example 1, 2, 5～7 that carry out BOD removal in schematic form;

Fig. 2 is an example of the setting method of the separation membrane in the occasion of the separation membrane for the solid-liquid separation equipment of the total oxidation tank sludge;

Fig. 3 is an example of the setting method of the separation membrane in the occasion of the separation membrane for the solid-liquid separation equipment of the total oxidation tank sludge;

Fig. 4 schematically represents the solid-liquid separation equipment of total oxidation tank sludge as a separation membrane, and carries out the figure of the flow process of embodiment 2 and comparative example 3 that BOD is removed;

5 is a diagram schematically showing the flow of Example 3 and Comparative Example 4 in which BOD removal and nitrogen component removal are performed.

Detailed ways

The (1) aeration tank, (2) self-oxidation coefficient, (3) total oxidation tank, (4) flocculant, and (5) solid-liquid separation equipment which are essential conditions for constituting the present invention will be specifically described.

(1) Aeration tank:

In the aeration tank used in the present invention, it is necessary to carry out aeration treatment in which the self-oxidation coefficient of the sludge flowing from the aeration tank into the total oxidation tank is more than 0.05 (1/day). The mechanism for obtaining the discharge water with an autooxidation coefficient of the above-mentioned sludge of 0.05 (1/day) or more will be described later, but at least in the present invention, the carrier must be dropped into the aeration tank of the present invention .

When the carrier is not charged into the aeration tank, the volume of the aeration tank is very large as described above in order to operate the aeration tank as an activated sludge method. In addition, since the self-oxidation coefficient of the activated sludge is smaller than that of the carrier used in the aeration tank, the volume of the total oxidation tank must also be increased. The use form of the carrier in the aeration tank may be any form of a fluidized bed or a fixed bed, but a fluidized bed is preferable from the viewpoint of treatment efficiency. The carriers that are put into the aeration tank can be various known carriers, but preferably, one carrier selected from colloidal carriers, plastic carriers and fibrous carriers, or a combination of two or more of these carriers carrier. Among them, the acetalized polyvinyl alcohol-based colloid carrier is preferable in terms of high handling performance and fluidity. In the case of a fluidized bed, the filling rate of the carrier is preferably in the range of 5% to 50% of the tank volume, and especially preferably in the range of 10% to 30% in terms of treatment efficiency and fluidity. within range.

(2) Self-oxidation coefficient:

The self-oxidation coefficient refers to the coefficient used in the calculation of the amount of sludge generated, which indicates the proportion of the sludge reduced by the mutual oxidation of sludge every day relative to the total amount of sludge in the total oxidation tank. In the case of activated sludge, the self-oxidation coefficient is generally about 0.02 (1/day) although it varies depending on operating conditions and the like. When the carrier is used in the aeration tank, if the self-oxidation coefficient is in the range of 0.05 to 0.1 (1/day), the amount is likely to decrease compared with activated sludge.

The self-oxidation coefficient refers to the activated sludge whose sludge concentration is calculated in advance or the aeration tank where the carrier is used. The sludge in the aeration tank is put into a 1L measuring cylinder. The sludge concentration is calculated by dividing the original sludge volume by the sludge volume reduced after a certain period of time.

The self-oxidation coefficient of the sludge in the effluent water from the aeration tank changes with the properties of the wastewater, the BOD volume load of the aeration tank, the type, properties, temperature, pH, and the like of the carrier. It has been found that the type and properties of the carrier are greatly affected by the pore diameter of the surface pores of the carrier. Regarding the pore diameter of the pores located on the surface of the carrier, when the surface of the carrier is observed through an electron microscope, the area of the pores below the specified pore diameter (dμm) starts to account for 70% or more compared with the entire area of the pores, Defined below dμm. In order to obtain the discharge water having the self-oxidation coefficient specified in the present invention, in the preliminary test of the specified BOD volume load, it is calculated by using a carrier whose pore diameter is 10 μm or less, 20 μm or less, 50 μm or less, and 100 μm or less. . In the present invention, it is preferable to use a carrier with a pore diameter below 50 μm, especially preferably below 20 μm. The reason for this is not necessarily clear, but it is thought that the inhabitability of microorganisms attached to the carrier is affected.

It has been found that with regard to the BOD volume load of the aeration tank (also described as s-BOD volume load.), when a suitable carrier is used, there is a tendency for the self-oxidation coefficient to increase by increasing the BOD volume load. Regarding the BOD volume load, it is preferable to operate in the range of BOD volume load of 2 to 3 (kg/m ³ ·day) first from the viewpoint of tank stability. As a result of the preliminary test under the above conditions, when the self-oxidation coefficient does not reach the range specified in the present invention, it is preferably in the range of 3 to 4, 4 to 5, and 5 or more (kg/m ³ ·day) in order. internal operation.

Regarding the temperature, from the aspect of the reactivity of the biological reaction, it is used in the range of 3°C to 40°C, preferably in the range of 10°C to 35°C, especially preferably in the range of 20°C to 30°C. conditions of. In addition, regarding the pH, from the aspect of the reactivity of the biological reaction, the pH is in the range of 3-9, preferably in the range of 4-8, especially preferably in the range of 6-8, especially The best conditions are in the range of 6-7.

Since the mechanism for making the self-oxidation coefficient of the sludge in the effluent water from the aeration tank more than 0.05 (1/day) is affected by the nature of the wastewater being treated, when the wastewater treatment method of the present invention is carried out, Variations in conditions suitable for the effluent treatment provided. Therefore, a preliminary test is performed in advance, and the volume load of BOD in the aeration tank, the type of carrier, especially the pore diameter, temperature, and pH of the pores on the surface must be adjusted according to the properties of the wastewater to be treated.

(3) Full oxidation tank:

The sludge concentration in the total oxidation tank varies with the form of solid-liquid separation in the subsequent stage. When the solid-liquid separation is a settling tank, the sludge concentration in the total oxidation tank is not particularly limited, but it is preferably in the range of 3000 to 6000 mg/L, especially more than 6000 mg/L. When the solid-liquid separation is membrane filtration or sand filtration, the sludge concentration in the total oxidation tank is preferably in the range of 6000-10000mg/L for the purpose of further compacting the volume of the total oxidation tank, especially Preferably above 10000mg/L. According to the present invention, for the total oxidation tank, aeration is carried out through a relatively low sludge load, thus, the speed of the proliferation of sludge and the oxidation of sludge itself can be balanced, the increase of sludge can be prevented, and the excess sludge can be recovered. Drainage treatment with a small amount of extraction. In addition, the state in which the extraction amount of excess sludge is small means that the MLSS of the total oxidation tank is basically constant, and in the sedimentation tank that receives the effluent water from the total oxidation tank, the interface of the sludge does not rise substantially, and it is not necessary to carry out more than 1 day. State of extraction of sludge. For example, if the amount of increased sludge per day is less than 1% relative to the total amount of sludge in the total oxidation tank, it means that the amount of excess sludge extracted is small.

(4) Flocculants:

The flocculant of the present invention is added for the purpose of improving the settleability of the sludge generated in the aeration tank and increasing the sludge concentration in the total oxidation tank. The addition of flocculant has the method of setting a flocculant reaction tank between the aeration tank and the total oxidation tank or between the total oxidation tank and the solid-liquid separation equipment, adding to the flocculant reaction tank and directly adding to the total oxidation tank . Preferably, the addition of the flocculant is carried out until the SVI of the total oxidation tank sludge is below 200ml/g.

(5) Solid-liquid separation mechanism:

The solid-liquid separation mechanism of the present invention may be any of conventionally known filtration devices such as sedimentation tanks, membrane filtration, sand filtration, and fiber filtration. When a settling tank is used, the operating conditions of water area load and residence time can be the same as those of the conventional activated sludge method.

FIG. 1 shows an example of the wastewater treatment flow of the present invention for the purpose of BOD removal. In this system, in order to reduce the aeration tank 1 as much as possible, it is preferable that the volume load of soluble BOD in the aeration tank 1 be 1 kg/(m ³ ·day) or more. Here, soluble BOD refers to BOD obtained by measuring the filtrate after filtering through a membrane filter with a pore size of 0.45 μ, and refers to BOD from which microorganisms have been removed (hereinafter, it is simply referred to as “s-BOD”). The higher the soluble BOD volume load, the more the overall size of the aeration tank 1 can be reduced. It can also be operated at 2kg/(m ³ ·day) or above 5kg/(m ³ ·day) by properly selecting the type of carrier and the filling rate. Preferably, the treatment rate of the solvent-based BOD in the aeration tank 1 is above 90%. Preferably, the BOD sludge load of the total oxidation tank 3 which reduces the volume of sludge under aerobic conditions is 0.05 kg-BOD/(kg-SS·day) or less.

In the present invention, the wastewater subjected to aerobic treatment in the above-mentioned aeration tank 1 is guided to the total oxidation tank 3, and a flocculant is added. However, it is not particularly limited, and a flocculant usable for general water treatment can be used. For example, examples of inorganic flocculants include aluminum sulfate (alum), polyaluminum chloride (PAC), ferrous sulfate, ferric sulfate, ferric chloride, copperas, sodium aluminate, ammonium alum, potassium Alum, slaked lime, quicklime, soda ash, sodium carbonate, magnesium oxide, iron-silica polymer, etc.

Examples of organic (polymer) flocculants include polyacrylamide, sodium alginate, sodium carboxymethyl cellulose, sodium polyacrylate, maleic acid copolymer, water-soluble aniline, polythiourea, polyethyleneimine, Quaternary ammonium salts, polyvinylpyridines, polyoxyethylene, causticized starch, etc. Two or more flocculants may be used in combination.

If the addition amount of these flocculants is too small, the coagulation effect will not be obtained, and if too much, the solid content will become excess sludge, and the amount of sludge extracted will increase. For example, in the system using the settling tank 5, it adds until SVI which is the settleability index of sludge becomes 200 ml/g or less. The addition method includes an intermittent addition method of adding until the settleability of sludge is improved, and then not adding until the settleability deteriorates, and a continuous addition method of adding a small amount of flocculant at ordinary times.

The range of pH and temperature suitable for coagulation is specified by the flocculant, and the pH is changed by addition of the flocculant, so it is desirable to perform water quality management suitable for coagulation such as pH adjustment as necessary.

In the total oxidation tank 3 the microorganisms produce their own oxidation, whereby nitric acid and/or nitrite nitrogen of microbial origin is produced, which is discharged from the sedimentation tank 5 into the treatment water. In order to reduce the amount of nitric acid and/or nitrous acid nitrogen, when the purpose of the wastewater treatment in the aeration tank 1 is to remove BOD, it can also be used in the denitrification tank at the front or rear stage of the total oxidation tank 3 A nitrification tank is also provided to return the treated water from the nitrification tank or the total oxidation tank 3 to the denitrification tank. In addition, when the purpose of the wastewater treatment in the aeration tank 1 is to remove nitrogen, the treated water may be returned to the denitrification tank. The process of nitrogen removal is not particularly limited, and nitrification tanks and denitrification tanks like the Wuhmann method can also be installed in sequence, and the sequence of denitrification tanks and nitrification tanks like the Barnard method can also be used to return the liquid from the nitrification tank to the denitrification tank. In the nitrogen tank, organic substances such as methanol are added as a nutrient source for denitrification bacteria. In addition, a method of combining these methods is also considered. For example, in the nitrification tank, under aerobic conditions, the BOD sludge load is below 0.08kg-BOD/kg-MLSS·day, and the nitrification and full nitrification processes that oxidize the sludge itself are carried out in one tank. wait.

The shape of the separation membrane used in the present invention is not particularly limited, and can be appropriately selected from hollow fiber membranes, tubular membranes, flat membranes, etc. In particular, it is preferable to use a hollow fiber membrane in terms of the overall size of the filter device.

In addition, the material constituting the separation membrane is not particularly limited, and can be selected from, for example, polyolefin-based, polysulfone-based, polyethersulfone-based, ethylene-vinyl alcohol copolymer-based , polyacrylonitrile-based, cellulose acetate-based, polyvinylidene fluoride-based, polyperfluoroethylene-based, polymethacrylate-based, polyester-based, polyamide-based, etc. Membranes made of inorganic materials such as ceramics, etc. In terms of high hydrophilicity, poor adhesion of SS components, and excellent peelability of attached SS components, it is preferable to use polysulfone resins that have been hydrophilically treated with polyvinyl alcohol resins. , polysulfone resins, polyvinyl alcohol resins, polyacrylonitrile resins, cellulose acetate resins, hydrophilically treated polyethylene resins and other hydrophilic materials added with hydrophilic polymers, but , Hollow fiber membranes made of other materials can also be used. When an organic polymer-based material is used, it may be a material obtained by copolymerizing a plurality of components, or a material formed by mixing a plurality of materials.

When an organic polymer material is used as the separation membrane material, the production method is not particularly limited, but a method appropriately selected from known methods can be employed according to the characteristics of the material and the desired shape and performance of the separation membrane.

Considering the separation performance of sludge and water, the pore size of the separation membrane used in the present invention is preferably below 5 microns. It is preferably in the range of 0.1 micron to 3 microns. The pore size mentioned here refers to the particle diameter of colloidal silica, emulsion, latex, etc., which excludes 90% of the reference substances when various known reference substances are filtered through the separation membrane. Preferably, the pore size is uniform. If it is an ultrafiltration membrane, it is impossible to obtain the pore size based on the particle diameter of such a reference substance. When using a known protein for molecular weight and performing the same measurement, it is best to have a molecular weight cut-off (molecular weight cut-off) of 3000 or more.

In the present invention, the separation membrane is modularized and used for filtration. The shape of the module can be appropriately selected according to the shape of the separation membrane, filtration method, filtration conditions, cleaning method, etc., and one or more membrane components can be installed to form a hollow fiber membrane module. For example, as the form of a membrane module formed by hollow fiber membranes, for example, dozens or even hundreds of thousands of hollow fiber membranes are bundled together to form a U-shaped type in the module; A type in which one end of the hollow fiber bundle is completely sealed; a type in which one end of the hollow fiber bundle is sealed in a state (free state) without one fiber being fixed by a suitable seal member; both ends of the hollow fiber bundle are opened type etc. In addition, the shape is not particularly limited, and may be, for example, a cylindrical shape or a mesh shape.

In the separation membrane, the pores are generally clogged and the filtration performance is reduced, but it can also be regenerated by cleaning it physically and chemically. Regeneration conditions can be appropriately selected according to the material, shape, pore size, etc. constituting the separation membrane module, but, for example, as the physical cleaning method of the hollow fiber membrane module, there are listed membrane filtration water backwashing, gas backwashing, flushing, bubble treatment, etc. In addition, as a chemical cleaning method, a method of cleaning with acids such as hydrochloric acid, sulfuric acid, nitric acid, oxalic acid, and citric acid; a method of cleaning with alkalis such as sodium hydroxide; A method of cleaning with an oxidizing agent; a method of cleaning with a chelating agent such as ethylenediaminetetraacetic acid, etc.

Fig. 2, Fig. 3 and Fig. 4 show an example of the arrangement of the separation membrane and a structural example of the membrane filtration device which can be used in the present invention. As a filtration method, as shown in FIG. 2, a membrane module (membrane filtration device) 7 or the like including a separation membrane is provided outside the total oxidation tank 3, and the stock solution including sludge is supplied to the membrane module 7 or the like, and The mode of carrying out total filtration; as shown in Fig. 3, the membrane assembly 7 etc. that comprise separation membrane etc. are arranged on the outside of total oxidation tank 3, while making the stock solution that comprises sludge circulate, with the mode of its part filtration; Like Fig. As shown in 4, the membrane module 7 including the separation membrane is immersed in the inside of the total oxidation tank 3, and suction filtration is performed. In addition, by setting the total oxidation tank 3 and the membrane module 7, a water head difference can be used instead of the pressurizing pump and the suction pump. In addition, in the case of such a method as shown in FIG. 3, there is generally the advantage that high permeation flux operation can be performed, and the membrane area is small. However, there is a problem that the energy required to circulate the stock solution including sludge shortcoming. On the other hand, in the case of the method shown in FIG. 4 , there are advantages of small installation space and energy, but generally, the permeation flux is low, and a large membrane area must be required. In addition, in the case of adopting the method of immersing the separation membrane in the inside of the total oxidation tank 3 as shown in FIG. 4, and performing filtration through suction and water head difference, a membrane including the separation membrane can be installed on the top of the diffuser. Module 7, etc., uses the effect of cleaning the membrane surface by diffusing air, and suppresses clogging of membrane pores. In order to carry out the present invention, it is also possible to newly install waste water treatment facilities, however, it is also possible to remodel existing waste water treatment facilities.

According to the present invention, it is possible to continue operation with a small amount of excess sludge generation by using compact equipment.

The present invention will be described in detail below based on the examples. In addition, the following physical quantities described in Examples and Comparative Examples were measured by the following evaluation methods.

(BOD removal rate)

The BOD of the untreated water passed to the test tank and the soluble BOD of the discharged water were measured and calculated according to the following formula.

BOD removal rate (%)

=({BOD of untreated water}-{soluble BOD of effluent water})÷{BOD of untreated water}×100

(SS)

After measuring the volume of the discharged water, filter it through a 0.45 μm filter, dry the filter, subtract the weight of the filter before treatment from the weight of the dried filter, calculate the weight of the solid content, divide it by the volume of the discharged water, Converted to concentration.

(Sludge Conversion Rate)

Calculated from the amount of BOD treated in the test tank and the amount of SS generated in the test tank.

Sludge conversion rate (%)={SS amount}÷{BOD removal amount}×100

(sludge extraction volume)

Record the dry weight of the amount of sludge that has been extracted.

Example 1

(Preliminary test) Put 100ml of acetalized polyvinyl alcohol-based rubber carrier with a pore diameter of 20μm or less in a 1000ml test tank, and supply the chemical wastewater A with a BOD volume load of 3.5kg (m ³ ·day). to the test tank. From the SS concentration in the effluent water when the BOD removal rate in the tank is 95% or more, the sludge conversion rate = 10%. Next, this SS was put into a 1L graduated cylinder, and the self-oxidation coefficient was calculated from the time-dependent change of the sludge concentration under aerobic conditions. At this time, the self-oxidation coefficient=0.082 (1/day) was obtained.

(Practical test) According to the sludge conversion rate and self-oxidation coefficient obtained through the preliminary test, according to the process shown in Figure 1, the aeration tank 1 with a capacity of ^230m3 , the total oxidation tank ³ with a capacity of 100m3 and the capacity For the wastewater treatment device formed by the sedimentation tank 5 of 50m ³ , a treatment experiment of chemical wastewater A of 400m ³ /day was carried out. In the aeration tank 1, 23 m ³ of an acetalized polyvinyl alcohol-based rubber carrier having a pore diameter of 20 μm or less was put into the aeration tank 1 . In the total oxidation tank 3, polyaluminum chloride (inorganic flocculant) is added until the solid-liquid separation of the sludge in the sedimentation tank 5 is improved. When operating under the condition that the BOD volume load in the aeration tank 1 was 3.5kg/(m ³ ·day), the MLSS in the total oxidation tank 3 gradually increased, but became almost constant at 10000mg/L. The sludge conversion rate in the aeration tank 1 was 10%. In addition, the self-oxidation coefficient calculated based on the amount of sludge flowing into the total oxidation tank 3 at a certain time of the MLSS of the total oxidation tank 3 and the amount of sludge reduced in the internal capacity of the total oxidation tank 3 is 0.080, which is basically consistent with the preliminary test results. unanimous. When the flocculant is continuously supplied for about one month from the start of the operation, and then when the SS of the treated water is equal to or more than 10 mg/L, the operation is continued for 10 months by adding it again. During the period, the addition of the flocculant was not added after the initial one month. In addition, it was possible to operate without pumping out sludge during the test period, and the treated water quality was good with BOD=5mg/L or less and SS=10mg/L or less.

Comparative example 1

(Preliminary test) Put 100ml of acetalized polyvinyl alcohol-based rubber carrier with a pore size of 20μm or less in a 1000ml test tank, and supply the chemical wastewater A with a BOD volume load of 2.5kg (m ³ ·day). to the test tank. From the SS concentration in the effluent water when the BOD removal rate in the tank is 95% or more, the sludge conversion rate = 10%. Next, this SS was put into a 1L graduated cylinder, and the self-oxidation coefficient was calculated from the time-dependent change of the sludge concentration under aerobic conditions. At this time, the self-oxidation coefficient=0.034 (1/day) was obtained.

(Demonstration test) According to the sludge conversion rate and self-oxidation coefficient obtained through the preliminary test, according to the process shown in Figure 1, the aeration tank 1 with a capacity of ^320m3 , the total oxidation tank ³ with a capacity of 100m3 and the capacity For the wastewater treatment device formed by the sedimentation tank 5 of 50m ³ , a treatment experiment of chemical wastewater A of 400m ³ /day was carried out. In the aeration tank 1, 32 m ³ of acetalized polyvinyl alcohol-based rubber carriers having a pore diameter of 20 μm or less were put into the aeration tank 1 . In the total oxidation tank 3, polyaluminum chloride (inorganic flocculant) is added until the solid-liquid separation of the total oxidation tank 3 sludge in the sedimentation tank 5 is improved. When operating under the condition that the BOD volume load in the aeration tank 1 was 2.5 kg/(m ³ ·day), the sludge conversion rate in the aeration tank 1 was 10%. According to the gradual increase of MLSS flowing into the total oxidation tank 3, it becomes almost constant at about 10000 mg/L, and in the sedimentation tank 5, the sludge level rises every day, and about 47 kg of sludge must be extracted every day. According to the amount of sludge generated in the total oxidation tank 3 and the amount of sludge that has been extracted, the self-oxidation coefficient is calculated, and at this time, the self-oxidation coefficient=0.033 (1/day).

Comparative example 2

(Demonstration test) According to the sludge conversion rate and the self-oxidation coefficient obtained by the preliminary test implemented in Comparative Example 1, according to the flow process shown in Figure 1, the aeration tank 1 with a capacity of ^320m is adopted, and the capacity is ^240m The wastewater treatment device formed by the total oxidation tank 3 and the sedimentation tank 5 with a capacity of 50m ³ was used for the treatment experiment of 400m ³ /day chemical wastewater A. In the aeration tank 1, 32 m ³ of acetalized polyvinyl alcohol-based rubber carriers having a pore diameter of 20 μm or less were put into the aeration tank 1 . In the total oxidation tank 3, polyaluminum chloride (inorganic flocculant) is added until the solid-liquid separation of the sludge in the sedimentation tank 5 is improved. When operating under the condition that the BOD volume load in the aeration tank 1 is 2.5kg/(m ³ ·day), the MLSS of the total oxidation tank 3 gradually increases and becomes a substantially constant value, about 10000mg/L. The sludge conversion rate in the aeration tank 1 was 10%. In addition, the self-oxidation coefficient calculated according to the amount of sludge flowing into the total oxidation tank 3 at a certain time of the MLSS of the total oxidation tank 3 and the sludge volume reduced in the total oxidation tank 3 is 0.033, which is basically consistent with the preliminary test results. The flocculant is continuously supplied for about one month from the start of operation, and then operated for 10 months by adding more when the SS of the treated water is more than 10 mg/L. During this period, no additional addition of flocculant was added after the initial one month. In addition, during the test period, it was possible to operate without pumping out sludge, and for the treated water quality, BOD=5mg/L or less and SS=10mg/L or less were good.

Except by changing the capacity of the carrier in the same manner for the same drainage as in Example 1 and Comparative Example 1, the carrier capacity ratio of the aeration tank 1 and the corresponding aeration tank 1 of Example 1, thereby changing the BOD volume Except the aspect of load, carry out the same operation, but, in the occasion of the BOD volume load of comparative example 1, self-oxidation coefficient is little, if adopt the full oxidation tank of its capacity and the total oxidation tank 3 identical capacity of embodiment 1, then must Sludge extraction is carried out. In order not to extract sludge under this condition, it must be required as shown in Comparative Example 2 to adopt a total oxidation tank 3 with a capacity more than twice that of Example 1. Obviously, by the wastewater treatment method of the present invention, It can be implemented in a way that the capacity of the device is small.

Example 2

(Preliminary test) Put 100ml of acetalized polyvinyl alcohol-based rubber carrier with a pore size of 20μm or less in a 1000ml test tank, and supply the chemical wastewater B with a BOD volume load of 2.5kg (m ³ ·day). to the test tank. From the SS concentration in the effluent water when the BOD removal rate in the tank is 95% or more, the sludge conversion rate = 30%. Next, the SS was put into a 1L graduated cylinder, and the autooxidation coefficient was calculated from the time-dependent change of the sludge concentration under aerobic conditions. At this time, the autooxidation coefficient=0.070 (1/day) was obtained.

(Demonstration test) According to the sludge conversion rate and self-oxidation coefficient obtained through the preliminary test, according to the process shown in Figure 4, the aeration tank 1 with a capacity of ^320m3 , the total oxidation tank ³ with a capacity of 300m3 and the membrane The wastewater treatment device formed by the filter device was used for the treatment experiment of 400m ³ /day chemical wastewater B. In the aeration tank 1, 32 m ³ of acetalized polyvinyl alcohol-based rubber carriers having a pore diameter of 20 μm or less were put into the aeration tank 1 . In the total oxidation tank 3, polyaluminum chloride (inorganic flocculant) is added until the solid-liquid separation of the sludge in the sedimentation tank 5 is improved. As for the membrane filtration device, the hollow fiber membrane module 7 with a pore size of 0.4 microns is immersed in the total oxidation tank 3, and it is operated in the manner of suction filtration while aeration for usual membrane cleaning is performed. When operating under the condition that the BOD volume load in the aeration tank 1 is 2.5kg/(m ³ ·day), the MLSS in the total oxidation tank 3 increases gradually, but becomes almost constant at about 11000mg/L about. The sludge conversion rate in the aeration tank 1 was 30%. In addition, the self-oxidation coefficient calculated based on the amount of sludge in the total oxidation tank 3 at a certain timing of the MLSS flowing into the total oxidation tank 3 and the amount of sludge reduced in the internal capacity of the total oxidation tank 3 is 0.073, which is basically consistent with the preliminary test results. unanimous. The flocculant was continuously supplied for about one month from the start of operation, and then operated for six months without adding it. During this period, the addition of the flocculant was not added after the initial one month. In addition, during the test period, it was possible to operate without extracting sludge, and the treated water quality was good at BOD=5mg/L or less and SS=0mg/L or less.

Comparative example 3

(Preliminary test) Put 100ml of acetalized polyvinyl alcohol-based rubber carrier with a pore size of 100μm or less into a 1000ml test tank, and supply the chemical wastewater B with a BOD volume load of 2.5kg (m ³ ·day). to the test tank. From the SS concentration in the effluent water when the BOD removal rate in the tank is 95% or more, the sludge conversion rate = 30%. Next, the SS was put into a 1L graduated cylinder, and the autooxidation coefficient was calculated from the time-dependent change of the sludge concentration under aerobic conditions. At this time, the autooxidation coefficient=0.025 (1/day) was obtained.

(Demonstration test) According to the sludge conversion rate and self-oxidation coefficient obtained through the preliminary test, according to the flow process shown in Figure 4, using the same drainage treatment device as in Example 2, the treatment experiment of 400m ³ /day chemical drainage B was carried out . In the aeration tank 1, 32 m ³ of acetalized polyvinyl alcohol-based rubber carriers having a pore diameter of 100 μm or less were put into the aeration tank 1 . In the total oxidation tank 3, polyaluminum chloride (inorganic flocculant) is added until the solid-liquid separation of the sludge in the sedimentation tank 5 is improved. As for the membrane filtration device, the hollow fiber membrane module 7 with a pore size of 0.4 microns is immersed in the total oxidation tank 3, and it is operated in the manner of suction filtration while aeration for usual membrane cleaning is performed. When operating under the condition that the BOD volume load in the aeration tank 1 is 2.5 kg/(m ³ ·day), the sludge conversion rate of the aeration tank 1 is about 30%. The MLSS in the total oxidation tank 3 is the same as in Example 2, which is about 11000 mg/L. In order to operate under the condition that the MLSS is 11000 mg/L, about 155 kg of sludge from the total oxidation tank 3 must be pumped out every day. When calculating the self-oxidation coefficient based on the amount of sludge generated in the total oxidation tank 3 and the amount of sludge that has been drawn out, the self-oxidation coefficient=0.026 (1/day).

Example 3

(Preliminary test) Put 100ml of acetalized polyvinyl alcohol-based rubber carrier with a pore size of 20μm or less in a ^1000ml test tank, and supply the artificial sewage to test tank. From the SS concentration in the effluent water when the BOD removal rate in the tank is 95% or more, the sludge conversion rate = 30%. Next, the SS was put into a 1L graduated cylinder, and the autooxidation coefficient was calculated from the time-dependent change of the sludge concentration under aerobic conditions. At this time, the autooxidation coefficient=0.070 (1/day) was obtained.

(Demonstration test) According to the sludge conversion rate obtained through the preliminary test and the self-oxidation coefficient, according to the flow process shown in Figure 5, the denitrification tank 9 with a capacity of 200L, the nitrification tank 11 with a capacity of 200L, and the tank with a capacity of 200L are adopted. The drainage treatment device formed by the total oxidation tank 3 and the sedimentation tank 5 with a capacity of 150L is used for the treatment experiment of 1200L/day artificial sewage. It is prepared in such a way that artificial sewage is BOD=200mg/L and total nitrogen content=50mg/L. In the denitrification tank 9 and the nitrification tank 11, 20 L of acetalized polyvinyl alcohol-based rubber carriers with a pore diameter of 20 μm or less were put into the denitrification tank 9 and the nitrification tank 11, respectively. The liquid in the nitrification tank 11 is returned to the denitrification tank 9 at about 3600 L/day. In the total oxidation tank 3, 230 g of polyaluminum chloride (inorganic flocculant) was initially added. As a result of operating under such conditions, the nitrogen removal performance in the denitrification tank 9 and the nitrification tank 11 reached the target nitrogen removal rate=75% one month after the start of operation. The MLSS of the total oxidation tank 3 gradually rises to a constant value of about 5200mg/L. The sludge conversion rate in the denitrification tank 9 and the nitrification tank 11 is 30%. In addition, according to the MLSS of the total oxidation tank 3, the amount of sludge flowing into the total oxidation tank 3 at a certain time and the sludge amount calculated by the internal capacity of the total oxidation tank 3 are 0.069 (1/day), which is 0.069 (1/day). The preliminary test results were basically the same. The flocculant was only injected at the start of operation, and then operated for 10 months without additional addition. In addition, during the test period, the operation can be carried out without pumping out the sludge, and the treated water quality is: BOD=5mg/L or less, SS=10mg/L or less, which is good.

Comparative example 4

(Preliminary test) Put 100ml of acetalized polyvinyl alcohol-based rubber carrier with a pore size of 100μm or less in a ^1000ml test tank, and supply artificial sewage to the test tank. From the SS concentration in the effluent water when the BOD removal rate in the tank is 95% or more, the sludge conversion rate = 30%. Next, the SS was put into a 1L graduated cylinder, and the autooxidation coefficient was calculated from the time-dependent change of the sludge concentration under aerobic conditions. At this time, the autooxidation coefficient=0.030 (1/day) was obtained.

(Demonstration test) According to the sludge conversion rate and the self-oxidation coefficient obtained through the preliminary test, according to the flow process shown in Figure 5, using the same drainage treatment device as in Example 3, the treatment experiment of 1200L/day of artificial sewage was carried out. It is prepared in such a way that artificial sewage is BOD=200mg/L and total nitrogen content=50mg/L. In the denitrification tank 9 and the nitrification tank 11, 20 L of acetalized polyvinyl alcohol-based rubber carriers with a pore diameter of 100 μm or less were put into the denitrification tank 9 and the nitrification tank 11, respectively. The liquid in the nitrification tank 11 is returned to the denitrification tank 9 at about 3600 L/day. In the total oxidation tank 3, 230 g of polyaluminum chloride (inorganic flocculant) was added initially. As a result of operating under such conditions, the nitrogen removal performance in the denitrification tank 9 and the nitrification tank 11 reached the target nitrogen removal rate=75% one month after the start of operation. The sludge conversion rate in the nitrification tank 11 was 15%. The MLSS flowing into the total oxidation tank 3 gradually increases and becomes almost constant at about 5200 mg/L. However, in the sedimentation tank 5, the sludge level rises every day, and about 40 g of sludge must be extracted every day. When calculating the self-oxidation coefficient based on the amount of sludge generated in the total oxidation tank 3 and the amount of sludge that has been drawn out, the self-oxidation coefficient=0.031 (1/day).

Example 4

(Preliminary test) Put 100ml of acetalized polyvinyl alcohol-based rubber carrier with a pore size of 20μm or less in a 1000ml test tank, and feed the food drainage A to the water in such a way that the BOD volume load is 3.0kg (m ³ ·day). to the test tank. From the SS concentration in the effluent water when the BOD removal rate in the tank is 95% or more, the sludge conversion rate = 40%. Next, this SS was put into a 1L graduated cylinder, and the self-oxidation coefficient was calculated from the time-dependent change of the sludge concentration under aerobic conditions. At this time, the self-oxidation coefficient=0.069 (1/day) was obtained.

(Demonstration test) According to the sludge conversion rate and self-oxidation coefficient obtained through the preliminary test, according to the process shown in Figure 1, the aeration tank 1 with a capacity of ^70m3 , the total oxidation tank ³ with a capacity of 190m3 and the capacity For the wastewater treatment device formed by the sedimentation tank 5 of 25m ³ , the treatment experiment of 200m ³ /day food wastewater was carried out. In the aeration tank 1, 7 m ³ of an acetalized polyvinyl alcohol-based rubber carrier having a pore diameter of 20 μm or less was put into the aeration tank 1 . In the total oxidation tank 3, polyaluminum chloride (inorganic flocculant) is added until the solid-liquid separation of the sludge in the sedimentation tank 5 is improved. When the volume load of BOD in the aeration tank 1 is 3.0kg (m ³ ·day), the MLSS in the total oxidation tank 3 increases slowly and basically becomes a constant value, about 6000mg/L. The sludge conversion rate in the aeration tank 1 was 40%. In addition, the self-oxidation coefficient calculated based on the amount of sludge flowing into the total oxidation tank 3 at a certain time of the MLSS of the total oxidation tank 3 and the amount of sludge reduced in the capacity of the total oxidation tank 3 is 0.070 (1/day), It is basically consistent with the preliminary test results. The flocculant is continuously supplied for about one month from the start of operation, and then, when the treated water SS=10mg/L or more, it is operated for 10 months by adding it again. During this period, after the addition of the flocculant was carried out for the first month, no additional increase was made. In addition, it was possible to operate without pumping out sludge during the test period, and the treated water quality was good with BOD=5mg/L or less and SS=10mg/L or less.

Comparative Example 5

(Preliminary test) Put 100ml of acetalized polyvinyl alcohol-based rubber carrier with a pore size of 100μm or less in a 1000ml test tank, and feed the food drainage A to the water in such a way that the BOD volume load is 3.0kg (m ³ ·day). to the test tank. From the SS concentration in the effluent water when the BOD removal rate in the tank is 95% or more, the sludge conversion rate = 40%. Next, this SS was put into a 1L graduated cylinder, and the self-oxidation coefficient was calculated from the time-dependent change of the sludge concentration under aerobic conditions. At this time, the self-oxidation coefficient=0.024 (1/day) was obtained.

(Demonstration test) According to the sludge conversion rate and self-oxidation coefficient obtained through the preliminary test, according to the process shown in Figure 1, using the same drainage treatment device as in Example 4, a treatment experiment of 200m ³ /day food drainage was carried out. In the aeration tank 1, 7 m ³ of an acetalized polyvinyl alcohol-based rubber carrier having a pore diameter of 100 μm or less was put into the aeration tank 1 . In the total oxidation tank 3, polyaluminum chloride (inorganic flocculant) is added until the solid-liquid separation of the sludge in the sedimentation tank 5 is improved. When the BOD volume load in the aeration tank 1 was operated at 3.0 kg (m ³ ·day), the sludge conversion rate in the aeration tank 1 was 40%. In addition, the MLSS of the total oxidation tank 3 gradually increases and becomes a substantially constant value of about 6000 mg/L. However, in the sedimentation tank 5, the sludge interface gradually rises every day, and about 50 kg must be extracted every day. of sludge. When calculating the self-oxidation coefficient from the amount of sludge generated in the total oxidation tank 3 and the amount of sludge that has been drawn out, the self-oxidation coefficient=0.025 (1/day).

Example 5

(Preliminary test) Put 100ml of acetalized polyvinyl alcohol-based rubber carrier with a pore size of 20μm or less in a 1000ml test tank, and supply chemical wastewater C with a BOD volume load of 2.5kg (m ³ ·day). to the test tank. From the SS concentration in the effluent water when the BOD removal rate in the tank is 95% or more, the sludge conversion rate = 30%. Next, this SS was put into a 1L graduated cylinder, and the self-oxidation coefficient was calculated from the time-dependent change of the sludge concentration under aerobic conditions. At this time, the self-oxidation coefficient=0.069 (1/day) was obtained.

(Practical test) According to the sludge conversion rate and self-oxidation coefficient obtained through the preliminary test, according to the process shown in Figure 1, the aeration tank 1 with a capacity of ^320m3 , the total oxidation tank ³ with a capacity of 570m3 and the capacity For the wastewater treatment device formed by the sedimentation tank 5 of 50m ³ , a treatment experiment of 400m ³ /day chemical wastewater C was carried out. In the aeration tank 1, 32 m ³ of acetalized polyvinyl alcohol-based rubber carriers having a pore diameter of 20 μm or less were put into the aeration tank 1 . In the total oxidation tank 3, polyaluminum chloride (inorganic flocculant) is added until the solid-liquid separation of the sludge in the sedimentation tank 5 is improved. When the volume load of BOD in the aeration tank 1 is 2.5kg (m ³ ·day), the MLSS in the total oxidation tank 3 gradually increases and basically becomes a constant value, about 6000mg/L. The sludge conversion rate in the aeration tank 1 was 30%. In addition, the self-oxidation coefficient calculated based on the amount of sludge flowing into the total oxidation tank 3 at a certain MLSS of the total oxidation tank 3 and the amount of sludge reduced in the internal capacity of the total oxidation tank 3 is 0.070, which is consistent with the preliminary test results . The flocculant is continuously supplied for about one month from the start of operation, and then, when the treated water SS=10mg/L or more, it is operated for 12 months by adding it again. During this period, no additional flocculant was added after the addition of the initial one month. In addition, it was possible to operate without extracting sludge during the test period, and the treated water quality was good with BOD = 5 mg/L or less and SS = 10 mg/L or less.

Comparative Example 6

(Preliminary test) Put 100ml of acetalized polyvinyl alcohol-based rubber carrier with a pore diameter of 100μm or less in a 1000ml test tank, and supply chemical wastewater C with a BOD volume load of 2.5kg (m ³ ·day). to the test tank. From the SS concentration in the effluent water when the BOD removal rate in the tank is 95% or more, the sludge conversion rate = 30%. Next, put this SS into a 1L graduated cylinder, and calculate the self-oxidation coefficient from the time-dependent change of the sludge concentration under aerobic conditions. At this time, the self-oxidation coefficient=0.033 (1/day) was obtained.

(Demonstration test) According to the sludge conversion rate and self-oxidation coefficient obtained through the preliminary test, according to the process shown in Figure 1, using the same drainage treatment device as in Example 5, a 400m ³ /day chemical drainage treatment experiment was carried out. In the aeration tank 1, 32 m ³ of acetalized polyvinyl alcohol-based rubber carriers having a pore diameter of 100 μm or less were put into the aeration tank 1 . In the total oxidation tank 3, polyaluminum chloride (inorganic flocculant) is added until the solid-liquid separation of the sludge in the sedimentation tank 5 is improved. When the BOD volume load in the aeration tank 1 was operated at 2.5 kg (m ³ ·day), the sludge conversion rate in the aeration tank 1 was 30%. In addition, the MLSS flowing into the total oxidation tank 3 gradually increases and becomes a substantially constant value of about 6000 mg/L. In the sedimentation tank 5, the sludge level rises every day, and about 127 kg of sludge must be pumped out every day. When calculating the self-oxidation coefficient based on the amount of sludge generated in the total oxidation tank 3 and the amount of sludge that has been drawn out, the self-oxidation coefficient=0.033 (1/day).

Example 6

(Preliminary test) Put 100ml of acetalized polyvinyl alcohol-based rubber carrier with a pore size of 100μm or less in a 1000ml test tank, and supply food drainage B to BOD so that the volume load is 5kg (m ³ ·day). test tank. From the SS concentration in the effluent water when the BOD removal rate in the tank is 95% or more, the sludge conversion rate = 30%. Next, put this SS into a 1L graduated cylinder, and calculate the self-oxidation coefficient from the time-dependent change of the sludge concentration under aerobic conditions. At this time, the self-oxidation coefficient=0.055 (1/day) was obtained.

(Demonstration test) According to the sludge conversion rate and self-oxidation coefficient obtained through the preliminary test, according to the process shown in Figure 1, the aeration tank 1 with a capacity of ^160m3 , the total oxidation tank ³ with a capacity of 700m3 and the capacity For the wastewater treatment device formed by the sedimentation tank 5 of 50m ³ , the treatment experiment of 400m ³ /day food wastewater B was carried out. In the aeration tank 1, 16 m ³ of acetalized polyvinyl alcohol-based rubber carriers having a pore size of 100 μm or less were put into the aeration tank 1 . In the total oxidation tank 3, polyaluminum chloride (inorganic flocculant) is added until the solid-liquid separation of the sludge in the sedimentation tank 5 is improved. When the volume load of BOD in the aeration tank 1 is 5kg (m ³ ·day), the MLSS in the total oxidation tank 3 increases slowly and basically becomes a constant value, about 6000mg/L. The sludge conversion rate in the aeration tank 1 was 30%. In addition, the self-oxidation coefficient calculated according to the amount of sludge flowing into the total oxidation tank 3 at a certain time of the MLSS of the total oxidation tank 3 and the amount of sludge reduced in the capacity of the inside of the total oxidation tank 3 is 0.057 (1/day), It is basically consistent with the preliminary test results. The flocculant is continuously supplied for about one month from the start of operation, and then, when the treated water SS=10mg/L or more, it is operated for 12 months by adding it again. During this period, no additional flocculant was added after the addition of the initial one month. In addition, during the test period, the operation can be carried out without extracting sludge, and the treated water quality is good at BOD=5mg/L or less and SS=10mg/L or less.

Comparative Example 7

(Preliminary test) Put 100ml of acetalized polyvinyl alcohol-based rubber carrier with a pore size of 100μm or less in a 1000ml test tank, and feed the food drainage B to a BOD volume load of 2.0kg (m ³ ·day). to the test tank. From the SS concentration in the effluent water when the BOD removal rate in the tank is 95% or more, the sludge conversion rate = 30%. Next, put this SS into a 1L graduated cylinder, and calculate the self-oxidation coefficient from the time-dependent change of the sludge concentration under aerobic conditions. At this time, the self-oxidation coefficient=0.020 (1/day) was obtained.

(Demonstration test) According to the sludge conversion rate and self-oxidation coefficient obtained through the preliminary test, according to the process shown in Figure 1, the aeration tank 1 with a capacity of ^400m3 , the total oxidation tank ³ with a capacity of 700m3 and the capacity For the wastewater treatment device formed by the sedimentation tank 5 of 50m ³ , the treatment experiment of 400m ³ /day food wastewater B was carried out. In the aeration tank 1, 40 m ³ of an acetalized polyvinyl alcohol-based rubber carrier having a pore diameter of 100 μm or less was put into the aeration tank 1 . In the total oxidation tank 3, polyaluminum chloride (inorganic flocculant) is added until the solid-liquid separation of the sludge in the sedimentation tank 5 is improved. When the BOD volume load in the aeration tank 1 was operated at 2.0 kg (m ³ ·day), the sludge conversion rate in the aeration tank 1 was 30%. In addition, the MLSS of the total oxidation tank 3 gradually increases and becomes a substantially constant value, which is about 6000 mg/L. In the sedimentation tank 5, the sludge interface gradually rises every day, and about 150 kg must be extracted every day. of sludge. When calculating the self-oxidation coefficient based on the amount of sludge generated in the total oxidation tank 3 and the amount of sludge that has been drawn out, the self-oxidation coefficient=0.021 (1/day).

Claims (6)

1. A drainage treatment method with few residual sludge extractions, which adopts an aeration tank that drains water under aerobic conditions and a granular carrier contacts, and makes the capacity of the sludge produced in the aeration tank under aerobic conditions Reduced total oxidation tank, solid-liquid separation equipment of total oxidation tank sludge, the method is characterized in that, including the self-oxidation coefficient of the sludge flowing in the above-mentioned total oxidation tank is set at more than 0.05 (1/day), in The step of adding flocculant in the total oxidation tank to improve the solid-liquid separation of the total oxidation tank sludge. 2. The wastewater treatment method according to claim 1, characterized in that the purpose of wastewater treatment in the aeration tank is BOD removal or nitrogen removal. 3. The wastewater treatment method according to claim 1, characterized in that the BOD sludge load in the above-mentioned total oxidation tank is set below 0.05kg-BOD/(kg-SS·day). 4. The wastewater treatment method according to claim 1, characterized in that the solid-liquid separation equipment for the sludge in the total oxidation tank is a sedimentation tank or a filtration equipment. 5. The wastewater treatment method according to claim 1, wherein the carrier is at least one carrier selected from the group consisting of gel carrier, plastic carrier and fibrous carrier. 6. The wastewater treatment method according to claim 5, characterized in that the carrier is an acetalized polyvinyl alcohol colloid.

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