TWI591024B - Biological treatment of organic wastewater - Google Patents

Description

Biological treatment method for organic wastewater

The present invention relates to a method for biologically treating domestic wastewater, sewage, organic wastewater from a food factory or a pulp factory, and more particularly to the use of bacteria to produce dispersed bacteria in the first biological treatment tank of the aerated organic wastewater. The first biologically treated water containing the dispersed bacteria from the first biological treatment tank is introduced into a biological treatment method for the organic wastewater which is preyed by the micro-animals after the aerobic second biological treatment tank to which the fluidized bed carrier is added.

The activated sludge method used in the biological treatment of organic waste is widely used in sewage treatment or industrial wastewater treatment in view of the advantages of 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, it becomes a large footprint. Further, since 20% of the decomposed BOD is converted into sludge by the cells, a large amount of excess sludge treatment also becomes a problem.

Regarding the high-load treatment of organic wastewater, a fluidized bed method in which a carrier is added is known. 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 sludge generated is about 30% of the decomposed BOD, which is higher than the general activated sludge process and becomes a disadvantage.

In Japanese Patent Publication No. 55-20649, the organic wastewater is first treated with bacteria in the first treatment tank, and the organic matter contained in the wastewater is oxidatively decomposed, converted into a non-aggregating bacterial cell, and then removed in the second treatment tank by supplementation. Fixative protozoa make it possible to reduce the excess sludge. Further, the high-load operation of the above method is made possible, and the treatment efficiency of the activated sludge method is also improved. Most of the wastewater treatment methods that have been used to supplement the protozoa or metazoans that are higher than the bacteria have been examined.

In Japan, JP-A-2000-210692, the water quality of the raw water that has become a problem due to the treatment method of Japanese Patent Publication No. 55-20649 has been proposed, and measures for deterioration in processing performance have been proposed. As a specific method, "the BOD fluctuation of the water to be treated is adjusted from the central value of the average concentration to within 50%", "the water quality of the first treatment tank and the first treated water are constantly measured", and "the first When the water quality of the treated water is deteriorated, the microorganism preparation or the seed sludge is added to the first treatment tank or the like.

In Japanese Patent Publication No. 60-23832, it has been proposed to ultrasonically treat the first precipitated sludge or excess sludge treated with bacteria, yeast, actinomycetes, algae, molds or wastewater by being supplemented by protozoa or metazoans. Or mechanical agitation, such that the size of the bait of the bait is smaller than that of the animal mouthpiece.

As a biological treatment method for organic wastewater by a multi-stage treatment of a fluidized bed and an activated sludge method, it is described in Japanese Patent No. 3,410,699 that the activated sludge method in the latter stage is loaded with 0.1 kg of BOD sludge- The low-load operation below BOD/kg-MLSS/d allows the sludge to self-oxidize, which can greatly reduce the amount of sludge removal.

The multi-stage activated sludge method using the feeding action of the above-mentioned micro-animals is actually used for the treatment of organic wastewater, and it is possible to reduce the treatment efficiency and reduce the amount of sludge generated by about 50% by the drainage of the target. However, the current state of sludge reduction is unstable. This is because it is impossible to specify the maintenance method of the stability of the tiny animals and the ratio of the bacteria and the tiny animals that become bait.

In WO2007/088860, it is described that the amount of minute organisms in the micro organism holding tank which stabilizes the amount of sludge to be transferred to the sludge is reduced by reducing the dissolved BOD sludge load for the second biological treatment tank for keeping the tiny animals.

However, when there are too many dispersing bacteria in the treated water in the first biological tank for the second biological treatment tank, the tiny animals in the second treatment tank cannot be completely preyed, and the amount of sludge generated cannot be reduced. Further, since the dispersed bacteria are difficult to separate from solid and liquid, it is necessary to maintain a margin for the solid-liquid separation conditions even when a solid-liquid separation means is used. In addition, since the dispersed bacteria in the first biological treatment water are bacteria in the logarithmic growth phase, it is impossible to prey on the micro-animals to self-digest and increase the solubility of the organic component, making it difficult to reuse the water (recovering the drainage).

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Special Public Show 55-20649

[Patent Document 2] Japanese Special Open 2000-210692

[Patent Document 3] Japanese Special Public Show 60-23832

[Patent Document 4] Japanese License 3410699

[Patent Document 5] WO2007/088860

The object of the present invention is to provide a biological treatment method for organic wastewater, which is a water-permeable organic wastewater in a gas-soluble first biological treatment tank and then generates a dispersed bacteria by bacteria, and will contain the dispersion from the first biological treatment tank. a biological treatment method for the first biological treatment water of the bacteria, introduced into the aerobic second biological treatment tank to which the fluidized bed carrier is added, and which is preyed by the micro-animals, characterized in that it can be properly preyed in the second biological treatment tank Disperse the bacteria for stable biological treatment.

The biological treatment method of the organic wastewater of the present invention is characterized in that the water-passing organic wastewater is in the aerobic first biological treatment tank and then the bacteria are dispersed, and the dispersed bacteria from the first biological treatment tank are included. A biological treatment method for biologically treating water, introducing a biologically-treated second biological treatment tank to which a fluidized bed carrier is added, and then being preyed by micro-animals, characterized in that the overall BOD volume load is set to 5 kg/m ³ /d Hereinafter, the load of the carrier from the dispersed bacteria in the first biological treatment water relative to the carrier in the second biological treatment tank (hereinafter referred to as the dispersion carrier load) is set to 8 kg-SS/m ³ -carrier/d or less.

In the method of the present invention, in order to obtain a balance between the dispersed bacteria generated by the first biological treatment tank and the predatory dispersed bacteria of the tiny animals in the second biological treatment tank, the removal of the dispersed bacteria in the second biological treatment tank can be prevented ( Can't prey on it).

1‧‧‧First biological treatment tank

2‧‧‧Second biological treatment tank

1a, 2a‧‧‧ carrier

Fig. 1 is a flow chart showing a biological treatment method for organic wastewater according to an embodiment.

Fig. 2 is a flow chart showing a biological treatment method for organic wastewater according to an embodiment.

Fig. 3 is a flow chart showing a biological treatment method for organic wastewater according to an embodiment.

The invention is further described in detail below.

Fig. 1 is a view showing a method of biological treatment of organic wastewater according to an embodiment of the present invention, in which organic wastewater is treated by the first biological treatment tank 1 and the second biological treatment tank 2. In this embodiment, the aeration means 1b is provided at the bottom of the first biological treatment tank 1, and the first biological treatment tank 1 is used as an aeration tank to which no carrier is added. The second biological treatment tank 2 is provided with an aeration means 2b at the bottom, and the carrier 2a is used as an aeration tank.

The organic wastewater is introduced into the first biological treatment tank 1, and 70% or more of the organic component (solubility BOD) is oxidatively decomposed by bacteria, and it is desirably 80% or more and more desirably 85 to 90%. The pH of the first biological treatment tank 1 is 6 or more, and it is desirable to be 8 or less. However, when the raw water contains a large amount of oil or an organic solvent or a surfactant, the pH may be 8.0 or more. The BOD volume load of the first biological treatment tank 1 is 1 kg/m ³ /d or more, HRT is 24 hours or less, and DO is 1 mg/L or less. By desirably 0.05 to 0.5 mg/L, the dispersed bacteria can be dominant. Treat water. Further, by shortening the HRT, the drainage having a low BOD concentration can be treated with a high load.

Further, a part of the treated water containing the sludge from the biological treatment tank in the latter stage is returned to the first biological treatment tank 1, or the first biological treatment tank 1 may be divided into a plurality of stages. However, when it becomes longer than the most appropriate value of the residence time (HRT), it is related to the predominance of the filamentous bacteria or the formation of flocs, which causes the second biological treatment tank 2 to generate bacteria which are difficult to be preyed. Therefore, it is preferable to control the HRT of the first biological treatment tank 1 to be constant. Since the most suitable HRT differs depending on the drainage, it is necessary to obtain 70 to 90% of the HRT capable of removing organic components from preliminary tests or simulations. As a method of maintaining the HRT at the most appropriate value, when the amount of water is reduced, returning to one part of the treated water, maintaining the amount of water flowing into the first biological treatment tank 1 constant, and stabilizing the HRT of the first biological treatment tank 1, or A method of changing the water level of the first biological treatment tank 1 in accordance with the change in the displacement. The range of stability is expected to be within 0.75 to 1.5 times of the most appropriate HRT obtained from preliminary tests or simulations.

Introducing the treated water of the first biological treatment tank 1 into the bottom Since the second biological treatment tank 2 of the aeration means 2b is provided, the residual sludge is reduced by oxidative decomposition of the remaining organic components, self-decomposition of the dispersed bacteria, and predation by the tiny animals. In the second biological treatment tank 2, in order to utilize the effect of the micro-animal having a slow proliferation rate and the self-decomposition of the bacteria in comparison with the bacteria, it is preferable to use an operating condition and a treatment device for keeping the micro-animals and bacteria in the system. The carrier separation screen 2c is provided in the drain portion of the second biological treatment tank 2, and the fluidized bed can be formed by adding the fluidized bed carrier 2a to increase the amount of retention of the tiny animals in the tank.

As the fluidized bed carrier 2a to be added, various shapes such as a spherical shape, a granular shape, a hollow cylindrical shape, and a filament shape can be used. The diameter of the carrier 2a is preferably from 0.1 to 10 mm. The material of the carrier 2a may be any of natural materials, inorganic materials, polymer materials, and the like, and a gel-like substance may also be used. However, as the carrier 2a, an angular carrier made of foam is desired. Further, in addition to the fluidized bed carrier, a filament carrier or a part of the sheet carrier may be added to the tank to form a shaking bed, and if so, the filling rate of the carrier can be comprehensively reduced.

In the present invention, the bulk BOD volume load is set to 5 kg/m ³ /d or less (even if the fluctuation of the raw water load is specified or less), and the carrier load of the dispersed bacteria is set to 8 kg-SS/m ³ -carrier/d or less. By setting the DO of the first biological treatment tank 1 or the carrier filling rate of the second biological treatment tank 2, it is possible to completely obtain the scattered bacteria and reliably prey on the tiny animals. Further, when the second biological treatment further uses a rocking bed carrier, the carrier for combining the fluidized bed carrier and the rocking bed carrier becomes a load of the dispersed bacteria.

As the SS from this dispersed bacteria, to become the first student It is preferable that the fine SS of the 8 μm polycarbonate filter is inside the treated water SS.

The first biologically treated water SS is composed of SS derived from the raw water and SS of the dispersed bacteria formed by the SS other than the bacterial cells and the first biological treatment tank 1. The size of the SS-based cells from the dispersed bacteria is less than 8 μm, for example, about 1 to 5 μm, and the predator-type micro-animals are filtered outside the cells to make the main SS-based particle size difficult to prey more than 8 μm, for example, about 10 to 50 μm. Accordingly, it is preferred that the SS which has passed through the mesh opening 8 μm filter becomes the SS derived from the dispersed bacteria. Further, as the fiber of the filter paper also captures fine SS, it is preferable to use a polycarbonate filter having a perforated plate as a filter. Based on the results of the SS measurement, the operating conditions such as the amount of carrier added to the second biological treatment tank 2 are adjusted so that the load of the dispersed bacteria in the second biological treatment tank 2 does not exceed the limit.

As described above, most of the organic matter is decomposed in the first biological treatment tank 1, that is, 70% or more of the drainage BOD, and it is desirable to be 80% or more, and it is preferable to stably change the cells. Therefore, even in the first biological treatment tank 1, as shown in Fig. 2, it is desirable to provide the carrier separation screen 1c to the drain portion to form a fluidized bed to which the carrier 1a is added. However, when the filling rate of the carrier of the first biological treatment tank 1 is excessively high, the dispersed bacteria cannot be formed, and the bacteria adhere to the carrier or the filamentous bacteria can proliferate. Therefore, the filling rate of the carrier added to the first biological treatment tank 1 is 20% or less, and particularly 10% or less, so that the concentration fluctuation can not be affected, and the generation of the dispersed bacteria which can be easily preyed is preferable. As the carrier 1a of the first biological treatment tank 1, the same one as the carrier 2a of the second biological treatment tank 2 can be used.

In the second biological treatment tank 2, in order to maintain tiny animals, It is necessary to have a large number of footholds, and it is desirable that the filling rate of the added carrier be 10% or more, particularly 20% or more, for example, 20 to 40%, in the fluidized bed.

In order to promote predation by a micro animal, the pH of the second biological treatment tank is 7.0 or less, and for example, it is preferably 6.0 to 7.0.

When the first biological treatment tank 1 completely decomposes the dissolved organic matter due to the initial stage of operation or the load caused by the fluctuation of the raw water, it is difficult to form a biofilm for the carrier in the second biological treatment tank, and to grow the microscopic animal. The nutrition is also insufficient. Therefore, in such a case, one part of the raw water is branched and introduced into the second biological treatment tank 2, and the dissolved BOD sludge load of the second biological treatment tank 2 is 0.001 kg-BOD/kg-MLSS/d or more, and it is desired to become Run as 0.025~0.1kg-BOD/kg-MLSS/d.

The solid-liquid separation of the treated water from the second biological treatment tank 2 can also obtain treated water having good water quality. As the solid-liquid separation means, one type or two or more types of a sedimentation tank, agglomeration sedimentation, agglutination-pressure flotation, and membrane separation can be used. 3 shows an example in which the inorganic flocculant is added to the reaction tank 3 to the treated water from the second biological treatment tank 2, and the polymer flocculant is added to the agglutination tank 4, and then the sedimentation tank 5 is subjected to sedimentation separation treatment. Separate treated water and sedimented sludge.

[Examples] [Example 1]

Follow the flow of Figure 2 to treat BOD 800mg/L, COD _cr 1300mg/L raw water (simulated drainage of food factory drainage). The capacity of the first biological treatment tank 1 was 2.5 L, and the capacity of the second biological treatment tank 2 was 4.4 L. The DO of the first biological treatment tank 1 was set at 0.5 mg/L, and the second biological treatment tank 2 was operated at DO2 to 3 mg/L. The carrier was added at a filling rate of 5% in the first biological treatment tank 1, and the carrier was added at a filling rate of 40% in the second biological treatment tank 2. As the carrier, an angular sponge carrier made of a polyurethane having a particle diameter of 3 mm was also used.

The BOD volume load of the first biological treatment tank 1 was 5.5 kg-BOD/m ³ /d and HRT 3.5 h, and was operated under the conditions of the overall BOD volume load of 2.0 kg-BOD/m ³ /d and HRT 9.6 h. The SS concentration in the first biologically treated water was 600 mg/L, and the dispersed bacterial carrier load was 5.9 kg-SS/m ³ -carrier/d. As a result, the SS concentration in the second biological treatment water was not 250 mg/L, and the sludge conversion rate was 0.19 kg-SS/kg- _CODcr .

[Embodiment 2]

In the first embodiment, the raw water was treated under the same conditions except for the flow of Fig. 3 in which the reaction tank 3, the flocculation tank 4, and the sedimentation tank 5 were provided in the subsequent stage of the second biological treatment tank 2. Further, PAC 300 mg/L was added as an inorganic flocculant, and KURIFLOCK PA331 manufactured by Kurida Industrial Co., Ltd. was added as an anionic polymer flocculant. As a result, the sludge conversion rate was 0.19 kg-SS/kg-COD _cr (excluding PAC sludge), and the treated water COD _cr and SS concentration were maintained at a good treated water quality of 20 mg/L or less.

[Comparative Example 1]

In Example 1, the carrier filling rate of the second biological treatment tank 2 was set to 25%, and the carrier load of the carrier 2a of the second biological treatment tank 2 was set to 9.4 kg-SS/m ³ -carrier/d. Others operate on the same conditions. As a result, the sludge conversion rate was changed to 0.29 kg-SS/kg-COD _{cr by the} outflow of the dispersed bacteria which was not preyed.

[Comparative Example 2]

In Example 2, except that the carrier filling rate of the second biological treatment tank 2 was set to 25%, and the dispersion carrier load of the carrier 2a of the second biological treatment tank 2 was set to 9 kg-SS/m ³ -carrier/d In addition, the operation is carried out under the same conditions. As a result, the sludge conversion rate was changed to 0.29 kg-SS/kg-COD _cr (excluding PAC sludge) by the outflow of the dispersed bacteria which were not preyed. Further, in order to set the treated water SS to 20 mg/L or less, the necessary agglutination conditions were PAC 800 mg/L, and the anionic polymer was increased to 2 mg/L. Further, even if the COD _cr 30 mg/L of this condition-treated water was compared with Example 2, the water quality was deteriorated.

1‧‧‧First biological treatment tank

1b, 2b‧‧ means

1c, 2c‧‧‧ screen

2‧‧‧Second biological treatment tank

1a, 2a‧‧‧ carrier

Claims (6)

A biological treatment method for organic wastewater, which is a first organism in which a water-permeable organic wastewater is formed in a first gas-treated biological treatment tank and then a bacteria is formed, and a dispersed bacteria from the first biological treatment tank is contained. A biological treatment method for treating water, introducing an organic wastewater which is preyed by micro-animals after adding a fluidized second biological treatment tank to a fluidized bed carrier, characterized in that the overall BOD volume load is set to 2.0 to 5 kg/m ³ /d Hereinafter, the BOD volume load of the first biological treatment tank is set to be 1 kg/m ³ /d or more, and 70 to 90% of the organic components in the organic wastewater are removed in the first biological treatment tank, and the first biological treatment water is derived from The load of the SS of the dispersed bacteria relative to the carrier in the second biological treatment tank (hereinafter referred to as the dispersion carrier load) is set to be 8 kg-SS/m ³ -carrier/d or less. The biological treatment method of the organic wastewater according to claim 1, wherein the first biological treatment tank is defined as a fluidized bed having a carrier filling rate of 20% or less, and the second biological treatment tank is defined as a fluidization of a carrier filling rate of 10% or more. bed. The biological treatment method of the organic wastewater according to claim 1 or 2, wherein the second biological treatment tank treatment water is formed by at least one of agglomeration sedimentation, agglutination, flotation separation, and membrane separation. The separation means performs solid-liquid separation of sludge and treated water. The biological treatment method of the organic wastewater according to claim 1 or 2, wherein the pH of the second biological treatment tank is set to 6-7. The biological treatment method of the organic wastewater according to claim 1 or 2, wherein one part of the raw water is added to the second biological treatment tank. The biological treatment method of the organic wastewater according to claim 1 or 2, wherein, among the SS of the first biological treatment water, the SS derived from the dispersed bacteria passes through the fine SS of the 8 μm polycarbonate filter.