KR101420455B1 - Method and apparatus for biological treatment of organic of organic wastewater - Google Patents

Abstract

An object of the present invention is to stabilize the sludge reduction effect in the multistage activated sludge process using the booster action of animalcules. The organic wastewater is introduced into the first biological treatment tank 1 provided with aeration means and is capable of surviving in ordinary raw water such as Alkaline genesis bacteria, Pseudomonas species, Bacillus species, Aerobacter species, and Flavobacterium species, , 70% or more, preferably 80% or more, and more preferably 90% or more of the organic component (soluble BOD) is oxidatively decomposed by the bacteria. The treated water in the first biological treatment tank 1 is introduced into the second biological treatment tank 2 where oxidation and decomposition of the remaining organic components, autolysis of the dispersing bacteria, and surplus Sludge is reduced. The second biological treatment tank 2 uses a fluidized bed in which the carrier C is added to increase the amount of retention of the animalcules in the tank.

Description

TECHNICAL FIELD The present invention relates to a method and apparatus for biological treatment of organic wastewater,

The present invention relates to a biological treatment method and apparatus for organic wastewater which can be used for organic wastewater treatment in a wide concentration range including domestic wastewater, sewage, food factory or pulp mill, and more particularly, And more particularly, to a biological treatment method and apparatus for organic wastewater which can reduce the amount of excess sludge generated.

The activated sludge method used for biological treatment of organic wastewater is widely used for sewage treatment and industrial wastewater treatment because of its good water quality and easy maintenance. However, since the BOD volume load used for the operation is about 0.5 to 0.8 kg / m 3 / d, a large site area is required. Also, since 20 to 40% of the decomposed BOD is converted into cells or sludge, a large amount of surplus sludge treatment also becomes a problem.

A fluidized bed method (fluidized bed method) in which a carrier is added is known as a method for high-load treatment of organic wastewater. When this method is used, it is possible to operate at a BOD volume load of 3 kg / m 3 / d or more. However, the amount of generated sludge is about 30% of the decomposed BOD, which is higher than the normal activated sludge process.

In Japanese Patent Publication No. 55-20649, organic wastewater is first treated with a bacterium in a first treatment tank, the organic matter contained in wastewater is oxidized and decomposed to convert into cells of non-cohesive bacteria, and then, in a second treatment tank, It is said that the amount of excess sludge can be reduced by removing the fish meal by the animal. In addition, in the above-described method, high-load operation is possible, and the treatment efficiency of the activated sludge process is also improved. As described above, many methods for treating wastewater using booster of protozoa and welfare animals located at high levels of bacteria have been devised.

Japanese Patent Application Laid-Open No. 2000-210692 proposes a countermeasure against deterioration of the processing performance due to fluctuation of the water quality of raw water which is a problem in the processing method of Japanese Patent No. 55-20649. As a specific method, "the BOD variation of the water to be treated is adjusted to be within 50% from the median of the average concentration", "the water quality in the first treatment tank and the first treated water is measured over time" And adding the microbial agent or sludge to the first treatment tank when the water quality of the treated water deteriorates.

Japanese Patent Application Laid-Open No. 60-23832 discloses a method of treating a pre-existing sludge or surplus sludge treated with bacteria, yeast, actinomycetes, seaweeds, fungi or wastewater to a protozoan or welfare animal by ultrasonic treatment or mechanical stirring, The size of the flock of the animal is made smaller than the mouth of the animal.

Patent No. 3410699 is a patent relating to multi-stage treatment of fluidized bed and activated sludge process. In this method, the activated sludge process at the subsequent stage is operated at a low load of BOD sludge load of 0.1 kg-BOD / kg to MLSS / d, thereby self-oxidizing the sludge to significantly reduce sludge discharge amount.

Patent Document 1: JP-A No. 55-20649

Patent Document 2: Japanese Patent Application Laid-Open No. 2000-210692

Patent Document 3: Japanese Patent Publication No. 55-20649

Patent Document 4: Japanese Patent Publication No. 60-23832

Patent Document 5: Japanese Patent No. 3410699

The multistage activated sludge process using the booster action of the animal such as protozoa or welfare animal is actually used for organic wastewater treatment. Depending on the wastewater to be treated, the treatment efficiency is improved, the amount of generated sludge is reduced by about 50% Is possible. However, this sludge reduction effect is not stabilized at present. This is because a stable method of keeping animalcules is not established.

DISCLOSURE OF INVENTION

An object of the present invention is to stabilize the sludge reduction effect in the multistage activated sludge process using the booster action of animalcules.

The method for biological treatment of organic wastewater according to the present invention is characterized in that organic wastewater is passed through a first biological treatment tank with two or more biological treatment vessels and subjected to biological treatment with bacteria to remove bacteria in a dispersed state from the first biological treatment tank Wherein the first treatment water is introduced into a second biological treatment tank for biological treatment so that the animalcules are present in the second biological treatment tank, wherein the concentration of dissolved oxygen in the first biological treatment tank is 0.5 mg / L or less And the second biological treatment tank is made into a fluid phase having a carrier, and the treated water of the second biological treatment tank is solid-liquid separated.

The biological treatment apparatus for organic wastewater according to the present invention is characterized in that the organic wastewater is passed through the first biological treatment tank with two or more biological treatment vessels and subjected to biological treatment with bacteria, The first treatment water is introduced into a second biological treatment tank for biological treatment so that the animalcules are present in the second biological treatment tank, wherein the concentration of dissolved oxygen in the first biological treatment tank is 0.5 mg / L or less And a solid-liquid separating means for subjecting the second biological treatment-treated water to solid-liquid separation treatment.

1 is a flow chart of the first embodiment.

2 is a flow chart of the second embodiment.

3 is a flowchart of the third embodiment.

4 is a flowchart of the fourth embodiment.

5 is a flowchart of a comparative example.

In the present invention, since the dissolved oxygen concentration of the first biological treatment tank is set to 0.5 mg / L or less, dispersed bacteria of about 1 to 5 mu m are preferentially placed in the first biological treatment tank. This dispersed bacterium having a size of 1 to 5 mu m is rapidly entrapped by the animalcules in the second biological treatment tank.

Further, in the present invention, since the second biological treatment tank is a fluidized bed having a carrier, the holding amount of the animalcules in the tank can be increased. That is, since the carrier functions as a footstep of the sticky filtration-predominant type animal that predates dispersed bacteria, the animal can be stably kept in the tank.

Hereinafter, an embodiment will be described with reference to Figs. 1 to 4. Fig.

Figure 1 is a schematic diagram of the basic flow of the invention. The organic wastewater is introduced into the first biological treatment tank 1 equipped with an aeration means and is supplied to the first biological treatment tank 1 with the use of a conventional biological treatment tank such as Alcaligenes spp., Pseudomonas spp., Bacillus spp., Aerobacter spp., Flavobacterium spp. 70% or more, preferably 80% or more, more preferably 90% or more of the organic component (soluble BOD) is oxidatively decomposed by the bacteria that survive in the wastewater.

The pH of the first biological treatment tank 1 is set to 6 or more, preferably 8 or less. However, when the raw water contains a large amount of oil component, the pH may be 8.0 or more.

In the present invention, by controlling the concentration of dissolved oxygen (DO) in the first biological treatment tank 1 to 0.5 mg / L or less, preferably 0.1 mg / L or less, more preferably 0.05 mg / L or less, Mu m of dispersed bacteria are ignited, and they are rapidly predated in the second biological treatment tank.

The DO concentration can be adjusted by controlling the aeration amount.

By setting the BOD volume load of the first biological treatment tank 1 to 1 kg / m 3 / d or more and the HRT to 24 hours or less, it is possible to promote the right of the dispersing bacteria. Further, by shortening the HRT, it is possible to treat a drain with a low BOD concentration at a high load.

A part of the sludge from the second biological treatment tank 2 may be conveyed to the first biological treatment tank 1, or the first biological treatment tank 1 may be made into two or more tanks.

Further, when the residence time (HRT) is longer than the optimum value, bacteria tend to predominate and flocs are formed, and bacteria that are difficult to be predated by animalcules are produced in the second biological treatment tank 2 Throw away. Therefore, it is preferable to control the HRT of the first biological treatment tank 1 to be constant. Since the optimum HRT differs depending on the drainage amount, it is desirable to obtain HRT capable of removing 70 to 90% of the organic components from a desk test or the like. As a method of maintaining the HRT at an optimum value, a part of the treated water is returned at the time of the decrease in the amount of water discharged to keep the amount of water flowing into the first biological treatment tank 1 constant, and the HRT of the first biological treatment tank 1 is stabilized There is a method of varying the water level of the first biological treatment tank in accordance with the variation of the method or the amount of displacement. The stabilizing width is preferably within 0.75 to 1.5 times the optimum HRT obtained from the desk test.

In the present invention, when a large amount of organic matter remains in the treated water from the first biological treatment tank 1 introduced into the second biological treatment tank 2, the oxidative decomposition is carried out in the second biological treatment tank 2, .

It is known that when the organic matter is oxidatively decomposed by bacteria in the second biological treatment tank 2 in which a large number of animalcules are present, the bacteria proliferate as a countermeasure for escape from the supplementation of the animalcules. The bacterial group that is proliferated in this form is not starved by the animalcules, and the decomposition thereof depends only on the self-extinguishment, so that the effect of reducing the amount of sludge generation is lowered.

Therefore, in the present invention, it is preferable to decompose most of the organic matter in the first treatment tank (1), that is, 70% or more, preferably 80% or more of the discharged BOD, and stably convert it into bacterial cells. Therefore, as shown in Fig. 2, it is preferable that the first biological treatment tank 1 also be a fluidized bed having a carrier. In addition, when the filling rate of the carrier in the first biological treatment tank 1 is excessively high, no dispersed microorganisms are formed, and bacteria adhere to the carrier or mature bacteria are proliferated. Therefore, It is preferable that the content of the dispersed microorganism is 10% or less, preferably 2 to 10%, more preferably 2 to 5%.

The carrier may be any shape such as a spherical shape, a pellet shape, a hollow cylindrical shape, and a thread shape, and may have a diameter of about 0.1 to 10 mm. The material may be any material such as a natural material, an inorganic material, or a polymer material, and a gel material may be used.

Next, the treated water in the first biological treatment tank 1 is introduced into the aerobic second biological treatment tank 2 provided with the aeration means, where the oxidative decomposition of the remaining organic components, And the excess sludge is reduced by decomposition and booster of the animalcules.

A sticky animal is suitable as the animal. This fixed animal is a protozoan with a property that the protozoa or protozoa which are likely to be fixed to solid particles or solid substances are adhered and agglomerated, such as, for example, vaginal type (Pilodina, In addition to benthicella, epistylis, opercularia, carcassum, and jujutanium, pestilent ciliates are included, but asbestos and uroproteins that crawl solid surfaces are also associated with sludge It can be used because it is easily settled.

In the second biological treatment tank (2), since the action of the animalcules with a slower growth rate than the bacteria and the autolysis of the bacteria are used, the operating conditions and treatment apparatuses in which the animalcules and bacteria stay in the system should be used. Thus, in the second biological treatment tank 2, the carrier C is added to form a fluidized bed so as to increase the holding amount of the animalcules in the tank. The carrier to be added may be any shape such as a spherical shape, a pellet shape, a hollow cylindrical shape, and a thread shape, and may have a diameter of about 0.1 to 10 mm. The material may be any material such as a natural material, an inorganic material, or a polymer material, and a gel material may be used. Further, the carrier (C) flows by aeration.

In the second biological treatment tank 2, since a large amount of suckers are required for holding the animalcules, it is preferable to set the filling rate of the carrier to be added to 10% or more, preferably 10 to 50%, particularly 20 to 40% Do.

The treated water from the second biological treatment tank 2 is separated into precipitated excess sludge and solid water (treated water) by solid-liquid separation in the sedimentation tank 3.

3, the solid-liquid separating means can be stably coagulated sedimentation system or floatation system (not shown) comprising flocculation tank 4 and sedimentation tank 5, so that treated water of stable quality can be obtained.

4, a part or the whole of the sludge separated from the treated water from the second biological treatment tank 2 is added to the third biological treatment tank 6 provided with aeration means, May be further promoted.

In addition, in the present invention, it is preferable that the sludge from the second biological treatment tank 2 is not conveyed to either the first biological treatment tank 1 or the second biological treatment tank 2. This is because when the sludge from the second biological treatment tank 2 is returned to the first biological treatment tank 1, the dispersed bacteria in the first biological treatment tank 1 are predated by the animalcules. Further, when this sludge is transported to the second biological treatment tank 2, the transported animalcules are fixed on the flock, not the carrier, so that when the flock is disintegrated due to load fluctuation or temperature fluctuation, This is because there are cases.

However, in the present invention, in order to supplement the animalcules to the second biological treatment tank in addition to the reduction of the sludge, a part of the treated sludge from the third biological treatment tank 6 is supplied to the second biological treatment tank 2 It may be returned. In this case, if the supplementation of the animalcules is carried out excessively, it becomes difficult to maintain the amount of the bacteria to remove the organic matter. In addition, since bacteria that are difficult to be predated are also proliferated and may not be able to be subjected to sludge reduction in the second biological treatment tank, the return to the second biological treatment tank 2 is carried out when the ratio of animalcules in the second biological treatment tank is VSS It is preferable to control so as not to exceed 20%.

Further, after the third animal's treatment tank 6 is not provided, the excess sludge may be anaerobically treated, physically treated, or chemically treated to kill the animalcules, And may be returned to the first or second biological treatment tank. Further, the third biological treatment tank 6 may be provided, and the above-described treatment may be performed on the excess sludge from the third biological treatment tank.

In addition, a settling tank in which the treated water in the third biological treatment tank 6 is introduced may be provided, and at least a part of the settled sludge may be returned to the biological treatment tank 3. In addition, the third biological treatment tank 6 may be made to have a long sludge retention time by using a fluidized bed or a membrane separation type aerobic treatment method in which a carrier is added. The treated water may be sent to the first biological treatment tank 1 or the second biological treatment tank 2 by solid-liquid separation, and the solid component may be returned to the third biological treatment tank 6. Further, the solid component may be discharged as excess sludge without being transported.

The pH of the second biological treatment tank 2 or the third biological treatment tank 6 may be set to 7.0 or less, for example, 5.0 to 7.0 in order to promote predation by the animalcules.

In addition, even if the operation conditions are set to be suitable for the proliferation of animalcules as described above, the animalcules are not proliferated and the effect of reducing the amount of sludge is not improved unless the essential components for propagation of the animalcules are contained in the wastewater. Therefore, by adding a nutrient to the second biological treatment tank 2, the effect of the amount of sludge can be stabilized by keeping the animalcules stably. Further, by adding a nutrient to the third biological treatment tank 6, the weight loss effect may be stabilized.

Examples of such nutrients include phospholipids, free fatty acids, sterol and lecithin containing them, other liquids such as liquid sugar, rice bran, beef squeezed beef, vegetable oil squeeze, soybean products (liquid soy milk, powdered soy milk, Which is effective in promoting the proliferation of welfare animals such as bean curd, bean curd, soybean derived feed, etc.), sugar beet ginger, shellfish powder, egg shell, vegetable extract, fish extract, various amino acids and various vitamins Nutrients may be used alone or in combination.

Example 1

(Raw fish extract, vegetable extract, and liquid sugar were mixed at a weight ratio of 2: 2: 1 and the BOD was adjusted to 650 mg / L) according to the flow shown in Fig. The volume of the first biological treatment tank 1 was 2.5 L and the volume of the second biological treatment tank 2 was 4.4 L in the raw water supply volume of 21 L / / L, and the DO concentration in the second biological treatment tank 2 was maintained at a level of 2 to 3 mg / L.

In addition, a sponge having a filling rate of 5% in the first biological treatment tank 1, a filling rate of 40% in the second biological treatment tank, and an average particle size of 3 mm (angle) as a carrier was added.

The BOD volume load for the first biological treatment tank was 5.5 kg-BOD / m ³ / d, the HRT was 3.5 hours, the total BOD volume load was 2.0 kg-BOD / m ³ / d, and HRT was 9.6 hours. The results are shown in Table 1. The sludge conversion rate averaged 0.30 kg-MLSS / kg-BOD. The BOD of the treated water was 10 mg / L or less.

Reference Example 1

3, 50% of the excess sludge settled in the sedimentation tank 5 was transferred to the second biological treatment tank 2, and the operation was performed under the same conditions as in Example 1, except that the sludge retention time was extended.

As a result, the propagated fixed animalcules were fixed on the conveyed sludge flocs instead of the carrier, and when the flocks were disintegrated due to load fluctuations or temperature changes, they flowed out of the system. Table 1 shows other operational results. As shown in Table 1, the sludge conversion rate was 0.42 kg-MLSS / kg-BOD on average. From the above results, it is apparent that the conversion rate of Example 1, which does not carry sludge to the second biological treatment tank, is lower than that of the first reference example.

Example 2

The same raw water as in Example 1 was treated according to the flow shown in Fig. The second embodiment is obtained by connecting the third biological treatment tank 6 having a capacity of 4 L to the settling tank 5 in the first embodiment. The DO of the third biological treatment tank 6 was set to 2 to 3 mg / l. In the same manner as in Example 1, the same carrier was added to the first biological treatment tank 1 at a filling rate of 5% and to the second biological treatment tank 2 at a filling rate of 40%. As in Example 1, the BOD volume load for the first biological treatment tank was 5.5 kg-BOD / m 3 / d, the HRT was 3.5 hours, the BOD volume load was 2.0 kg-BOD / m 3 / d as a whole, Respectively.

The sludge in the tank was discharged from the third biological treatment tank 6 as excess sludge to release 0.4 l / d from the sedimentation tank 5 and 0.4 l / d of surplus sludge was added to the third biological treatment tank 6. Also, once in a day, the concentration of lecithin as a nutrient was added to the third biological treatment tank 6 so that the concentration in the tank was 1 mg / l. As a result, the sludge conversion rate was 0.15 kg-MLSS / kg-BOD. The BOD of the treated water was 10 mg / L or less.

Comparative Example 1

5, the same raw water as that in Example 1 was treated according to the flow of connecting the biological treatment tank 10 and the sedimentation tank 11 having a capacity of 6.9 liters. No carrier was added to the biological treatment tank (10). And the DO of the biological treatment tank (10) was operated to be 2 to 3 mg / l. The raw water supply amount was the same as that in Example 1, and the entire amount of the sludge from the settler 11 was transferred to the biological treatment tank 10, and a part of the sludge in the sludge was discharged intermittently as excess sludge . As a result of operation under the conditions of a total BOD volume load of 2.0 kg-BOD / m 3 / d and an HRT of 9.6 hours, mushy bacteria appeared on the fifth day after the start of operation and sludge was not settled in the sedimentation basin.

Comparative Example 2

In Comparative Example 1, the same carrier as in the above Example was added to the biological treatment tank at a filling rate of 40%. The sludge from the sedimentation paper 11 was not conveyed at all. The others were operated under the same conditions as in Comparative Example 2. As a result, the sludge conversion rate was 0.55 kg-MLSS / kg-BOD. In addition, the amount of the flocculant added when the biologically treated water was subjected to solid-liquid separation was about twice as large as that in Example 1.

Comparative Example 3

The operation was carried out in the same manner as in Example 1 except that the DO of the first biological treatment tank 1 was set at 1 mg / l. The results are shown in Table 1. As shown in Table 1, if the DO is higher than 0.5 mg / l, the dispersed microorganism becomes 10 m or more in length and can not feed the animalcules, confirming that the sludge conversion rate is increased.

<Review>

From the above results, the following items were confirmed.

(1) By making the DO of the first biological treatment tank 0.5 mg / L or less, the treatment can be performed efficiently.

(2) The amount of sludge generated in Examples 1 and 2 in which a carrier was added to the second biological treatment tank was lowered.

(3) In the standard activated sludge process, it was possible to remove stable organic matter even in the case of a failure due to bulking or the like.

(4) The amount of sludge generated was smaller than that of the conventional fluidized bed method of Comparative Example 2, and the addition amount of the flocculant in the flocculation tank was reduced to about 50%.

(5) According to the present invention, efficient biological treatment of organic wastewater is possible, and drastic reduction of sludge generated during wastewater treatment; Improvement of treatment efficiency by high load operation; It is possible to obtain the effect of maintaining a stable treated water quality and the like.

Claims (19)

The first biological treatment tank is divided into two or more biological treatment vessels, the organic biological wastewater is passed through the first biological treatment tank and subjected to biological treatment by bacteria, and the first treated water containing bacteria in the dispersed state from the first biological treatment tank is subjected to a second biological treatment In a biological treatment method for causing a animal to be present in this second biological treatment tank, The dissolved oxygen concentration of the first biological treatment tank is controlled to be 0.5 mg / L or less, The second biological treatment tank is formed into a fluid phase having a carrier, the treated water of the second biological treatment tank is subjected to solid- And the outflow sludge from the second biological treatment tank is not transported to either the first biological treatment tank or the second biological treatment tank. The method according to claim 1, wherein a carrier is present in each of the first and second biological treatment tanks, wherein the carrier filling rate of the first biological treatment tank is set at 10% or less, the second biological treatment tank is set at 10% Wherein the organic wastewater is in a fluidized bed. The biological treatment method for organic wastewater according to claim 1, wherein the solid-liquid separation treatment is carried out by coagulation sedimentation or pressurized flotation separation. The biological treatment method for organic wastewater according to claim 1, wherein the sludge separated by the solid-liquid separation treatment is introduced into the third biological treatment tank and is reduced. The biological treatment method for organic wastewater according to claim 4, wherein the pH of at least one of the second biological treatment tank and the third biological treatment tank is set to 5.0 to 7.0. The biological treatment method for organic wastewater according to claim 4, wherein a biological nutrient is added to at least one of the second biological treatment tank and the third biological treatment tank. The biological treatment method for organic wastewater according to claim 1, wherein a part of the raw water is added to the second biological treatment tank. The biological treatment method for organic wastewater according to claim 4, wherein part of the raw water is added to at least one of the second biological treatment tank and the third biological treatment tank. The biological treatment method of organic wastewater according to claim 1, wherein the bacterium is at least one member selected from the group consisting of Alcaligenes spp., Pseudomonas spp., Bacillus spp., Aerobacter spp., And Flavobacterium spp. The biological treatment method for biological wastewater according to claim 1, wherein 70% or more of the soluble BOD is decomposed by the bacteria in the first biological treatment tank. The biological treatment method for biological wastewater according to claim 1, wherein the pH of the first biological treatment tank is 6 to 8. The biological treatment method for biological wastewater according to claim 1, wherein the concentration of dissolved oxygen in the first biological treatment tank is 0.1 mg / L or less. The biological treatment method for biological wastewater according to claim 1, wherein the BOD volume load on the first biological treatment tank is set to 1 kg / m 3 / d or more and the HRT is set to 24 hours or less. The biological treatment method for organic wastewater according to claim 2, wherein the diameter of the support is 0.1 to 10 mm. The method according to claim 1, wherein aeration is carried out in a second biological treatment tank to make it aerobic, oxidative decomposition of organic components introduced into the second biological treatment tank, autolysis of dispersible bacteria and reduction of excess sludge by booster of animalcules Wherein the organic wastewater is subjected to a biological treatment. The biological treatment method for organic wastewater according to claim 1, wherein the animal animal is a fixative animal. The organic wastewater treatment method according to claim 16, wherein the sticky animal is at least one of vaginal, voritissella, epistylis, opercularia, carcassium, juctammium, asbestosca, Biological treatment method. The nutrient according to claim 6, wherein the nutrient is selected from the group consisting of phospholipid, free fatty acid, rhizolin lipid, sterol, lecithin, liquid sugar, rice bran, beef squeeze, vegetable oil squeeze, liquid soymilk, powdered soymilk, Wherein the organic wastewater is at least one selected from the group consisting of flour, soybean-derived feed, sugar beet ginger, shell powder, egg shell, vegetable extract, fish meal extract, amino acid and vitamin. The first biological treatment tank is divided into two or more biological treatment vessels, the organic biological wastewater is passed through the first biological treatment tank and subjected to biological treatment by bacteria, and the first treated water containing bacteria in the dispersed state from the first biological treatment tank is subjected to a second biological treatment And the biological sludge from the second biological treatment tank is not returned to any of the first biological treatment tank and the second biological treatment tank, As a result, A control device for controlling the dissolved oxygen concentration of the first biological treatment tank to 0.5 mg / L or less, An apparatus for forming a fluidized bed of a carrier in the second biological treatment tank, And a solid-liquid separation device for subjecting the second biological treatment tank treated water to solid-liquid separation treatment.

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