TW201825410A - Biological treatment method for organic wastewater - Google Patents

Abstract

Provided is a method, in two-stage biological treatment of organic wastewater, for efficiently performing biological treatment after reducing tank volume and reducing the capacity and size of the overall wastewater treatment facility. A biological treatment apparatus is provided with: a feed water adjustment-cum-first biological treatment tank 11 to which organic wastewater is supplied as feed water and which adjusts the water volume and conducts aerobic biological treatment in a single-pass mode; and a second biological treatment tank 12 for conducting aerobic biological treatment of the first biologically treated water. The biological treatment apparatus is operated so that the instantaneous HRT at the time of feed water inflow into the feed water adjustment-cum-first biological treatment tank 11 is 2-8 hours and the water level is at least 40% of full capacity. By having the feed water adjustment tank to function as a first biological treatment tank, the first biological treatment tank is omitted and the capacity of the overall wastewater treatment facility is reduced.

Description

   Biological treatment method for organic drainage   

The invention relates to a biological treatment method for organic drainage, which can be used for the treatment of a wide range of organic drainage in domestic drainage, gutter water, food factories or pulp mills. In particular, the present invention relates to a biological treatment method for organic drainage, using a first biological treatment tank and a second biological treatment tank that introduces first biological treatment water from the first biological treatment tank.

A method for efficiently treating organic drainage with a high load is known to treat organic drainage with bacteria in a first biological treatment tank to oxidize and decompose organic substances contained in the drainage into non-agglutinating bacteria. A treatment method in which the bacterial cells are preyed and removed by the fixed protozoa in the second biological treatment tank, and the resulting dispersed bacteria are removed (for example, Patent Document 1).

This method is actually performed as follows.

The amount or quality of organic drainage discharged from a factory or the like may change with time or season. Therefore, as shown in FIG. 6, a raw water adjustment tank 1 is provided at the front of the first biological treatment tank 2 to make it organic. Drainage is stored in the raw water adjustment tank 1 (for example, about 5 to 8 hours of HRT), and organic drain water adjusted to a certain range in the raw water adjustment tank 1 is sequentially supplied to the first biological treatment tank 2 and the second biological treatment tank 3, And biological treatment. The treated water in the second biological treatment tank 3 is solid-liquid separated in the precipitation tank 4. As shown in FIG. 6, in the first biological treatment tank 2, biological treatment is performed in a cross-flow manner. The treated water of the first biological treatment tank 2 (the first biologically treated water) is processed in the second biological treatment tank 3. The treated water (second biologically treated water) in the second biological treatment tank 3 is solid-liquid separated in the sedimentation tank 4, and the separated water is sent out of the system as treated water. The separated sludge from the sedimentation tank 4 is circulated to the second biological treatment tank 3.

In this two-stage biological treatment, in the first biological treatment tank 2, most of the organic matter is processed by dispersed bacteria (dispersion bacteria) in a cross-flow manner, and the dispersed bacteria are preferentially generated. In the second biological treatment in the later stage, The tank 2 allows the dispersed bacteria to be preyed by micro-animals to reduce the amount of sludge. However, in this case, since the first biological treatment tank 2 in which the bacteria are dispersed is maintained in a floating state, a certain residence time is required. Depending on the characteristics of the drainage, the required residence time becomes longer, and the dispersing bacteria tank (the first biological treatment tank 2) becomes large.

In response to this problem, Patent Document 2 proposes a method in which the liquid in the first biological treatment tank or a part of the first biologically treated water is returned to the original water tank, and the raw water tank is used in a manner of partially dispersing bacteria so as to be dispersed. The first biological treatment tank of the bacteria tank is miniaturized.

Patent Document 1: Japanese Patent Application Publication No. 2013-141640

Patent Document 2: Japanese Patent Application Laid-Open No. 2015-199049

The miniaturization of the first biological treatment tank can be achieved by the method of Patent Document 2. However, in recent years, further miniaturization has been required due to the demand for a small capacity and miniaturization of the apparatus.

The object of the present invention is to provide a two-stage biological treatment of organic drainage using a first biological treatment tank and a second biological treatment tank that introduces first biological treatment water from the first biological treatment tank, thereby reducing the volume of the tank body, A small capacity, miniaturization and efficient biological treatment method for the entire drainage treatment facility is required.

The inventors believe that by providing the raw water adjustment tank with the function of the first biological treatment tank, the first biological treatment tank can be omitted and the volume of the entire drainage treatment facility can be reduced. Then, as a result of further reviewing the conditions required for the raw water adjustment and the first biological treatment tank, the present invention was completed as described below.

[1] A biological treatment method for organic drainage, which introduces organic drainage as raw water in the first biological treatment tank and the first biological treatment tank provided in two stages in series, 1 The first biological treatment water obtained by performing aerobic biological treatment in the biological treatment tank is introduced into the second biological treatment tank, and the aerobic biological treatment is performed in the second biological treatment tank and the second biological treatment water is discharged from the organic drainage. The biological treatment method is characterized in that: the first biological treatment tank is set as the first biological treatment tank and the first biological treatment tank, and the first biological treatment tank is adjusted by adjusting the water amount of the introduced raw water and performing aerobic biological treatment in a cross-flow manner. The instant HRT of the biological treatment tank when raw water flows in is set to 2 to 8 hours, and the water level of the raw water adjustment and the first biological treatment tank is set to 40% or more when the water is full.

[2] The biological treatment method for organic drainage according to [1], wherein the average HRT of the raw water adjustment and the first biological treatment tank is set to be more than 10 hours, and the average HRT includes that the raw water does not flow into the aforementioned raw water adjustment and the first biological Time to process the tank.

[3] The biological treatment method for organic drainage according to [1] or [2], wherein a nutrient source necessary for decomposition of organic matter is added to the aforementioned raw water adjustment and first biological treatment tank, and the raw water adjustment and first biological treatment are added The pH of the liquid in the tank was adjusted to 6.5 to 8.5.

[4] The biological treatment method for organic drainage according to any one of [1] to [3], wherein in the raw water adjustment and the first biological treatment tank, the organic drainage included in the tank is conducted. In the process of converting organic matter into disperse bacteria, in the second biological treatment tank, a treatment for dispersing bacteria in the first biologically treated water containing the dispersing bacteria from the first biological treatment tank is performed to reduce disperse bacteria. Second biologically treated water with residual organic matter.

[5] The biological treatment method for organic drainage according to any one of [1] to [4], wherein the bottom of the raw water adjustment and the first biological treatment tank is arranged at a height of 40% or less of the maximum water depth of the tank Fixed bed support.

According to the present invention, in the two-stage biological treatment of organic drainage, the volume of the tank can be reduced, the small capacity and miniaturization of the entire drainage treatment equipment can be achieved, and the biological treatment can be efficiently performed.

11‧‧‧ Raw water adjustment and first biological treatment tank

11A‧‧‧ fluid bed support

11B‧‧‧ Carrying Screen

12‧‧‧The second biological treatment tank

12A‧‧‧ fluid bed support

13‧‧‧ settling tank

L ₁ ‧‧‧ full waterline

L ₂ ‧‧‧Control line

P‧‧‧Pump

B ₁ , B ₂ ‧‧‧ diffuser

FIG. 1 is a system diagram showing an example of an embodiment of an apparatus for performing a biological treatment method for organic drainage of the present invention.

FIG. 2 is a system diagram showing another example of an embodiment of an apparatus for performing a biological treatment method for organic drainage of the present invention.

FIG. 3 is a system diagram showing another example of an embodiment of an apparatus for performing a biological treatment method for organic drainage of the present invention.

FIG. 4 is a system diagram showing an example of the embodiment of the raw water adjustment and the first biological treatment tank.

FIG. 5 is a graph showing a time-dependent change of the raw water adjustment and the amount of water (L) in the first biological treatment tank and the COD _Cr (mg / L) of the first biological treatment water in Example 1. FIG.

FIG. 6 shows a system diagram of a conventional two-stage biological treatment program.

Hereinafter, embodiments of the present invention will be described in detail.

In the present invention, the function of the first biological treatment tank is provided in the raw water adjustment tank, which is considered necessary in the conventional drainage treatment equipment, so that the first biological treatment tank can be omitted and the volume of the entire drainage treatment equipment can be reduced.

As described above, the amount of raw water discharged from factories and the like varies greatly depending on the time zone or season. Therefore, for example, when the amount of water discharged is small, if the amount of raw water adjusted and stored in the first biological treatment tank is almost exhausted, and the amount of dispersed bacteria in the first biological treated tank is changed, Too little, the efficiency of decomposition of organic matter will be reduced. Therefore, in order to keep the dispersed bacteria in the tank, the water level of the raw water adjustment and the first biological treatment tank is designed to be 40% or more when full of water.

Unlike a normal raw water adjustment tank, it is necessary to ensure a reaction time necessary for sufficiently decomposing organic matter in the raw water adjustment and first biological treatment tank. Therefore, the instantaneous HRT when raw water flows in is set to 2 to 8 hours, and the average HRT including the time when raw water has not flowed in (hereinafter referred to as the "average HRT" for short) should be set to 10 hours or more.

The instantaneous HRT at the time when raw water flows in is the instantaneous HRT (hydraulic retention time) when the raw water flows into the raw water adjustment and the first biological treatment tank. For example, if the maximum flow rate of raw water flowing into the raw water adjustment and the first biological treatment tank when the raw water flows in is set to Q _max (m ³ / hr), the amount of water in the raw water adjustment and the first biological treatment tank at a certain moment when the raw water flows in is set to V ₁ (m ³ ), the instantaneous HRT is calculated as V ₁ / Q _max (hr). If the capacity of the raw water adjustment and the first biological treatment tank (the amount of water when the raw water adjustment and the first biological treatment tank is full) is set to V _max (m ³ ), the amount of water when the raw water adjustment and the minimum water level of the first biological treatment tank is set. If V _min (m ³ ) is set, the instantaneous HRT will vary from V _min / Q _max to V _max / Q _max (hr).

The average HRT can be calculated as follows. For example, if the average HRT during the operation of the device, the average daily flow rate of raw water flowing into the raw water adjustment and first biological treatment tank is set to Q _max (m ³ / d), and the maximum water amount of the raw water adjustment and first biological treatment tank is set to V _max (m ³ ), the average HRT is calculated as V _max / Q _max × 24 (hr).

The biological treatment tank has a constant cross-sectional area and is not affected by the depth. Therefore, in the present invention, the capacity control is specified by water level (depth) control.

The biological treatment method of organic drainage according to the present invention will be specifically described below with reference to the drawings.

1 to 3 are system diagrams showing an example of an embodiment of an apparatus for performing a biological treatment method for organic drainage of the present invention. FIG. 4 is a system diagram showing an example of the embodiment of the raw water adjustment and the first biological treatment tank related to the present invention. In Figures 1 to 4, components that perform the same functions are given the same symbols. In the figure, P is the pump, and B ₁ and B ₂ are the air diffusers. L ₁ indicates a full water line described later, and L ₂ indicates a control line described later.

The raw water adjustment and the first biological treatment tank related to the present invention is a tank body having the functions of the first biological treatment tank and the raw water adjustment tank. Therefore, the first stage of the raw water adjustment and the first biological treatment tank does not need to correspond to the raw water adjustment. Slot body. The organic drainage discharged from the factory or the like can be directly introduced into the raw water adjustment and first biological treatment tank without going through the raw water adjustment and first biological treatment tank. However, in the case of processing a combined drainage of a plurality of types of drainage, a storage tank may be provided for each drainage. In this case, the raw water adjustment tank that does not pass through the total drainage is directly introduced into the raw water adjustment and first biological treatment tank. In addition, the first biological treatment water from the raw water adjustment and the first biological treatment tank is directly introduced into the second biological treatment tank.

    [The raw water adjustment and the first biological treatment tank are set to a batch type, and the second biological treatment tank is set to a continuous biological treatment]    

FIG. 1 is a system diagram showing an example of a case where the raw water adjustment and first biological treatment tank is set as a batch type biological treatment tank, and the second biological treatment tank is set as a continuous biological treatment tank.

Organic drainage of raw water is introduced into the raw water adjustment and first biological treatment tank 11. At the same time as the amount of water is adjusted, biological oxidation treatment is performed by aeration. 70% of the organic components (soluble BOD) contained in the organic drainage. Above, it is hoped that 75 ~ 90% will be oxidized and decomposed by bacteria.

The circulation in the raw water adjustment and the first biological treatment tank 11 is performed by a cross flow method. The instantaneous HRT when the raw water flows in is set to 2 to 8 hours, and the water level is set to 40% or more when the water is full, that is, the water level is set. The variation is designed to be 40 to 100% relative to the water level at 100% when full. Thereby, the minimum number of seed bacteria can be left in the tank, and the raw water whose water amount fluctuates can be processed.

Here, "design" refers to determining the maximum water amount and the minimum water amount of the raw water adjustment and the first biological treatment tank based on the maximum flow rate of the raw water flowing into the raw water adjustment and the first biological treatment tank and the average daily flow rate. The first biological treatment tank.

The instantaneous HRT of the raw water adjustment and first biological treatment tank 11 when the raw water flows in will vary with the water level of the raw water adjustment and first biological treatment tank 11. If the instantaneous HRT is less than 2 hours, the organic matter cannot be sufficiently decomposed. If the transient HRT exceeds 8 hours, filamentous bacteria will be produced. The instant HRT of the raw water adjustment and first biological treatment tank 11 when raw water flows in should be designed to be 2 to 6 hours.

If the raw water adjustment and the water level of the first biological treatment tank 11 is less than 40% when the water is full, the number of dispersed bacteria in the tank becomes too small, and the organic matter decomposition efficiency decreases. Therefore, it is designed in such a way that the raw water adjustment and the water level of the first biological treatment tank 11 are maintained at 40% or more, and preferably 50 to 100%, when the water is full.

In the following, the water level (100%) when the raw water is adjusted and the first biological treatment tank is full will be referred to as the "full water line", and the line with a water level of 40% relative to the full water line will be referred to as the "limit line" .

The BOD volume load in the raw water adjustment and first biological treatment tank 11 should be set to 1 kg / m ³ / d or more, for example, 1 to 10 kg / m ³ / d. The instantaneous maximum BOD volume load during raw water adjustment and circulation of the first biological treatment tank 11 should be 10 kg / m ³ / d or less, such as 2-20 kg / m ³ / d, and the average HRT should be designed to be more than 10 hours, especially 10 ~ 24 hours. If the BOD volume load is lower than the lower limit described above, the processing efficiency decreases. If the average HRT is lower than the lower limit described above, the organic matter in the organic wastewater cannot be sufficiently treated. If the average HRT is too long, the processing efficiency will be lowered, so it should be set below the above upper limit.

A support can also be added to the raw water adjustment and first biological treatment tank 11 to increase the amount of sludge retention to cope with load fluctuations. The support may be any of a fluid bed support and a fixed bed support.

The shape of the fluid bed support can be arbitrary, such as spherical, granular, hollow cylindrical, linear, plate-shaped, cubic, rectangular parallelepiped, etc., and the size is also arbitrary, such as a particle size of about 0.1 to 10 mm. The material of the support is also arbitrary, such as natural materials, inorganic materials, polymer materials, and the like, and colloidal substances may be used.

When a fluidized bed support is provided in the raw water adjustment and first biological treatment tank 11, in order to prevent outflow of the support, a screen must be installed in the tank. FIG. 4 shows the raw water adjustment and first biological treatment tank 11 in a case where a fluidized bed support 11A is added to the raw water adjustment and first biological treatment tank 11 and a support separation screen 11B is provided. When a fluidized bed support is added to the raw water adjustment and first biological treatment tank 11, the filling rate of the support is desirably set to 1 to 10%.

The fixed bed support is fixed to at least a part of the support to either the bottom, side, or upper portion of the raw water adjustment and first biological treatment tank 11 and is designed to swing. Its shape can be arbitrary, such as a line shape, a plate shape, a strip shape, and the like. The material of the support is also arbitrary, such as natural materials, inorganic materials, polymer materials, and the like, and colloidal substances may be used.

When a fixed bed support is provided in the raw water adjustment and first biological treatment tank, if the height of the fixed bed is high, when the water level in the raw water adjustment and first biological treatment tank is low, the fixed bed will be exposed from the water surface, so the height should be determined. It is adjusted for raw water and less than 40% of the maximum water depth of the first biological treatment tank, for example, 20 to 40%. The filling rate of the fixed bed support of the raw water adjustment and the first biological treatment tank should be 0.1 to 2%.

In the case where any support is provided, if the filling rate is low, the effect of improving the microbial cell holding capacity by providing the support cannot be sufficiently obtained, and if the filling rate is high, the air permeability or air diffusion is hindered.

In the raw water adjustment and first biological treatment tank 11, in order to promote the reaction, it is preferable to directly add a nutrient. Nutrients refer to N, P, S, Ca, Mg, K, Zn, Cu, amino acids, vitamins, etc., inorganic substances, organic substances, minerals, trace metals, etc. necessary for the proliferation of microorganisms, and are insufficient in the target raw water substance.

The raw water adjustment and the pH of the liquid in the tank of the first biological treatment tank 11 should be adjusted to 6.5 to 8.5. Especially in the case of drainage containing oil, in order to prevent solidification of the oil, the pH is desirably set to 7.5 to 8.5.

In the inflow water of the raw water adjustment and first biological treatment tank 11 or the raw water adjustment and first biological treatment tank 11, a nutrient addition means or an acid or alkali pH adjustment means may be appropriately provided.

The first biological treatment water from the raw water adjustment and the first biological treatment tank 11 is introduced into the second biological treatment tank 12, and the oxidative decomposition of the remaining organic components, the self-decomposition of dispersed bacteria, and the use of predators of small animals are performed by aeration. Reduction of remaining sludge. In the second biological treatment tank 12, in order to take advantage of the action of micro-animals whose growth rate is slower than that of bacteria and the self-decomposition of bacteria, it is necessary to use operating conditions and processing devices that leave micro-animals and bacteria in the system. By adding a fluidized bed support or a fixed bed support to the second biological treatment tank 12, it is possible to increase the holding amount of the micro-animal in the tank.

The shape of the fluidized bed support added to the second biological treatment tank 12 can be arbitrary, such as spherical, granular, hollow cylindrical, linear, plate, cubic, rectangular parallelepiped, etc., and the size is also arbitrary, such as 0.1 ~ 10mm particle size. The material of the support may be arbitrary, such as natural materials, inorganic materials, polymer materials, and the like, and colloidal materials may also be used.

The fixed-bed support is a structure in which at least a part of the support is fixed to any one of the bottom, side, and upper portion of the second biological treatment tank 12. Its shape is arbitrary, such as a linear shape, a plate shape, a strip shape, etc., and the material is arbitrary, such as a natural material, an inorganic material, a polymer material, etc., and a colloidal substance may be used.

The filling rate of the fluid bed support in the second biological treatment tank 12 should preferably be 5 to 50%, especially 10 to 40%. The filling rate of the fixed-bed support in the second biological treatment tank 12 should preferably be 0.1 to 30%, especially 0.5 to 10%. If the filling rate of any one of the supports is low, the number of tiny animals cannot be increased, and if the filling rate is too high, the flowability or air diffusion will be hindered. An example of a case where a fluidized bed support is provided in the second biological treatment tank 12 is shown in FIG. 2 described later.

By providing a solid-liquid separation device such as a sedimentation tank 13 at the rear stage of the second biological treatment tank 12, the second biological treatment water from the second biological treatment tank 12 is separated into solid and liquid, and the separated water is taken out as treated water. The separated sludge is returned to the second biological treatment tank 12 as return sludge, and the sludge can be maintained. This solid-liquid separation can be any of a precipitation tank, a membrane separation, and an upflow separation. The second biological treatment tank 12 can also be operated in batches to simplify solid-liquid separation. It is also possible to adopt a cross-flow type in which a support is added to the second biological treatment tank, and then an agglutination solid-liquid separation device is provided to obtain clear treated water.

FIG. 1 is a system diagram showing a case where the second biological treatment tank 12 is operated in a floating type or a fixed bed type. A system diagram in which a fluidized bed support 12A is filled in the second biological treatment tank 12 and the support is maintained in the tank by a separation screen (not shown) is shown in FIG. 2. In the example of FIG. 2, the surplus sludge separated from the sedimentation tank 13 is not returned to the second biological treatment tank 12. The second biological treatment tank 12 can also be used in the cross-flow type in the same way as the raw water adjustment and the first biological treatment tank 11. Come and run.

    [Set the raw water adjustment and the first biological treatment tank and the second biological treatment tank as a batch type biological treatment]    

FIG. 3 is a system diagram showing a case where not only the raw water adjustment and the first biological treatment tank 11 but also the second biological treatment tank 12 is set to operate in batch mode, and the sedimentation tank 13 is omitted.

In this case, it is suitable to provide a fixed bed support in the second biological treatment tank 12 so as to maintain the number of small animals. In this case, a fixed bed support must be provided at a position lower than the lowest water level of the second biological treatment tank 12.

    [Example]    

Hereinafter, examples, comparative examples, and reference examples will be described.

    [Example 1]    

In the raw water adjustment with a capacity of 10 L and the first biological treatment tank 11 (without support), food-based drainage (COD _Cr = 2100 mg / L, BOD = 1200 mg / L, SS = 0 mg / L) was used as raw water. The apparatus of FIG. 1 performs processing. Raw water is circulated in the water conditioning and first biological treatment tank 11 at 6 mL, 32 mL / min (= instantaneous maximum flow rate), and then stopped for 6 hours. (23L / d of treated water per day).

The first biologically treated water from the raw water adjustment and the first biologically treated tank 11 was intermittently transported to the second biologically treated tank 12 (capacity 10L, no load) at 22 mL / min for 2.25 hours out of 3 hours. The second biological treatment tank 12 is introduced.

The instantaneous HRT at the highest water level (full water: 10L) is 5.2 hours at the highest water level (the full water: 10L), and the instantaneous HRT at the lowest water level (40% at the full water: 4L) is 2.1 hours. The average HRT is For 10.4 hours. The BOD volume load of the raw water adjustment and the first biological treatment tank 11 is 2.76 kg / m ³ / d, and the instantaneous maximum BOD volume load may vary within a range of 5.5 to 13.8 kg / m ³ / d.

The pH was adjusted to 7. To the raw water adjustment and first biological treatment tank 11, urea and phosphoric acid are added as nutrition sources (N and P sources).

The time-varying raw water adjustment at this time and the amount of water (L) in the first biological treatment tank and the COD _Cr (mg / L) of the first biological treatment water are shown in FIG. 5.

It is clear from FIG. 5 that the raw water adjustment and the amount of water in the first biological treatment tank will vary between 100% and 40% when full water is used, and the COD _Cr removal rate of the first biological treatment water will also be 50 to 84%. (COD _{Cr is} about 1000 ~ 330mg / L), but the average removal rate is 75%, which can efficiently convert organic matter to disperse bacteria.

The SS of the second biologically treated water was 30 mg / L or less, and the sludge conversion rate was 0.1 kg-SS / kg-COD _{Cr in} total with the remaining sludge fraction extracted from the second biologically treating tank.

    [Comparative Example 1]    

The same operation as in Example 1 was performed except that the minimum water level of the raw water adjustment and the first biological treatment tank was set to 20% at the time of full water. As a result, the instantaneous HRT when the water level was the lowest was 1.02 hours. During this period, the dispersed bacteria would flow out from the raw water adjustment and the first biological treatment tank, and the COD _Cr removal rate was 10 to 54%, with an average of 30%. Dispersed bacteria were generated in the raw water adjustment and the first biological treatment tank, but the inflow of COD _{Cr in} the second biological treatment tank increased. In the device of FIG. 1, sludge overflow occurred in the sedimentation tank due to swelling caused by filamentous bacteria. flow. The sludge conversion rate was 0.24 kg-SS / kg-COD _Cr .

    [Example 2]    

The minimum water level of the raw water adjustment and the first biological treatment tank was set to 50% of the full water, and the raw water flow rate at the time of circulation was set to 37 mL / min (the treated water volume per day was 26.6 L / d). The same operation was performed in Example 1. As a result, the instantaneous HRT was 2.25 to 4.5 hours, and the average HRT was 9 hours. During this period, the dispersed bacteria were stably maintained, and the COD _Cr removal rate fluctuated from 37 to 70%, with an average of 57%. Treat water quality. In addition, the inflow of COD _{Cr in} the second biological treatment tank increased. However, compared with Example 1, the increase in the amount of sludge generation stopped at about 30%.

    [Example 3, Comparative Example 2]    

The operation was performed under the same conditions as in Example 1 except that the tank volume and water volume of the raw water adjustment and the first biological treatment tank were changed, and the accompanying transient HRT was changed as shown in Table 1.

The results are shown in Table 1 together with the results of Example 1 and Comparative Example 1.

    [Example 4]    

As a fixed bed support, a plate-shaped soft polyurethane foam system support (1 piece) having a length of 10 cm × a width of 6.5 cm × a thickness of 0.8 cm was used so that the direction of the surface of the board became vertical, and Except that the upper part and the lower part were fixed in the second biological treatment tank, the same operation as in Example 1 was performed. As a result, the average COD _Cr removal rate was 90%, and the sludge conversion rate was 0.08 kg-SS / kg-COD _Cr .

As can be seen from Table 1, according to the present invention, in the two-stage biological treatment of organic drainage, by providing the raw water adjustment tank with the function of the first biological treatment tank, the first biological treatment tank can be omitted, and the entire drainage treatment equipment can be sought. The volume is reduced, and a small capacity and miniaturization of the entire drainage treatment facility are required, and biological treatment can be performed efficiently.

Although the present invention has been described in detail using specific aspects, it will be apparent to those skilled in the art that various changes can be made without departing from the spirit and scope of the present invention.

This application is based on the Japanese Patent Application No. 2016-185517 filed on September 23, 2016, the entire contents of which are hereby incorporated by reference.

Claims (5)

    An organic drainage biological treatment method is to introduce organic drainage as raw water in the first biological treatment tank and the first biological treatment tank provided in two stages in series, and the first biological treatment tank will be treated in the first biological treatment tank. Biological treatment method for organic drainage of first biologically treated water obtained by aerobic biological treatment in a tank and introducing it into a second biologically treated tank, and performing aerobic biological treatment in the second biologically treated tank and discharging the second biologically treated water It is characterized in that the first biological treatment tank is set as the first biological treatment tank and the first biological treatment tank which adjusts the amount of raw water introduced while performing aerobic biological treatment in a cross-flow manner, and the first biological treatment tank The instantaneous HRT when the raw water flows in is set to 2 to 8 hours, and the water level of the raw water adjustment and the first biological treatment tank is set to 40% or more when the water is full.         For example, the biological treatment method of organic drainage in the first scope of the patent application, wherein the average HRT of the raw water adjustment and the first biological treatment tank is set to be more than 10 hours, and the average HRT includes that the raw water does not flow into the aforementioned raw water adjustment and the first biological Time to process the tank.         For example, the biological treatment method for organic drainage of item 1 or 2 of the patent scope, wherein the nutrient source necessary for the decomposition of organic matter is added to the aforementioned raw water adjustment and first biological treatment tank, and the raw water adjustment and first biological treatment tank are added. The pH of the solution was adjusted to 6.5 ~ 8.5.         For example, the biological treatment method for organic drainage in any one of claims 1 to 3, wherein the organic water contained in the organic drainage introduced into the tank is converted into the aforementioned raw water adjustment and the first biological treatment tank into The dispersing bacteria are treated in the second biological treatment tank to make tiny animals prey on the dispersing bacteria in the first biological treatment water containing the dispersing bacteria from the first biological treatment tank, thereby reducing the number of dispersing bacteria and residual organic matter. 2nd biologically treated water.         For example, the biological treatment method for organic drainage according to any one of claims 1 to 4, wherein a fixed bed with a height of 40% or less of the maximum water depth of the tank is arranged at the bottom of the aforementioned raw water adjustment and 1st biological treatment tank Carrying body.