JP2010046572A - Method and apparatus for biologically treating organic matter-containing water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain stable treated water quality while performing high-load operation in the biological treatment of organic matter-containing water by effectively improving treatment efficiency without additional carriers, an increase in the quantity of airflow, and remodeling including an extension of an aeration tank and the like. <P>SOLUTION: In a method for introducing the organic matter-containing water into an aeration tank 1 having organism carriers in it and aerating the water with an oxygen-containing gas to biologically treat it, nitric acid (salt) and/or nitrous acid (salt) are added to the aeration tank 1 as an oxygen source to carry out the biological oxidation of an organic matter by the aeration and the decomposition of the organic matter by denitrification reaction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method and an apparatus that can be used for biological treatment of water containing organic matter in a wide concentration range including domestic wastewater, sewage, food factories and pulp factories. The present invention relates to a biological treatment method and a biological treatment apparatus that can cope with an increase in load by a simple operation without remodeling such as adding an additional gas, increasing an aeration amount, or adding an aeration tank.

The activated sludge method used when biologically treating organic matter-containing wastewater is widely used for sewage treatment, industrial wastewater treatment, and the like because of its advantages such as good treated water quality and easy maintenance. However, since the BOD volume load to be used in the operation is 0.1 to 1.0 (generally 0.5~0.8) kg / ^{m 3} / day or so, it is necessary to large site area.

For high-load treatment of organic matter-containing wastewater, biological treatment (fixed bed method, fluidized bed method) with a carrier added is known. When this method is used, it is possible to operate with a BOD volumetric load of 1 kg / m ³ / day or more. Moreover, since it is not necessary to return the sludge from the sedimentation basin that separates the biologically treated water into solid and liquid, the labor of sludge management in the sedimentation basin can be saved, and maintenance can be facilitated.

  However, biological treatment using a carrier has the following problems.

  (1) To perform high-load treatment, it is necessary to maintain a high bacterial cell concentration. However, if bacteria are allowed to adhere to the inside of the carrier, it is necessary to perform an operation with a high DO (dissolved oxygen) concentration. . Moreover, if it is going to maintain a high density | concentration of a microbial cell, it will be necessary to fill with many carriers, and not only the carrier cost will go up, but since the dissolution efficiency of DO will fall, aeration cost will also increase.

  (2) In order to achieve a high organic substance removal rate with a low carrier filling rate and a low DO concentration, it is necessary to operate at a low load. If the operation under an overload continues, not only the organic substance removal rate will decrease, but a large amount of highly viscous filamentous fungus will adhere to the carrier, causing odor generation, and if these peel off, In the floor, the screen separating the carrier is blocked. Further, the flow path is blocked on the fixed bed.

  Thus, the biological treatment of the carrier addition type including the fixed bed method, the fluidized bed method, etc. has been put into practical use for the treatment of wastewater containing organic matter, and depending on the target wastewater, stable treatment is possible. On the other hand, in the case of a device designed with a sufficient tank volume, carrier filling rate, and aeration volume, it is impossible to process even if the water volume is increased temporarily or the concentration of raw water is increased. Needs to be modified, such as the addition of carriers and the addition of aeration tanks and blowers.

  In addition, as a method for improving treatment efficiency and a high-load treatment method, there is also an application of a multistage carrier-added biological treatment, but even in this case, the first-stage tank load becomes very high. This causes an increase in filamentous bacteria as described above, leading to problems such as screen blockage, flow path blockage, and odor generation.

  In order to avoid such problems, when determining the carrier filling rate, tank volume, and air flow rate, if the equipment is designed with the assumption of maximum load and summer DO drop, it may be difficult for factories where the busy season is short. For loads during periods other than the busy season, the equipment becomes excessive and uneconomical.

The raw water is diluted 100 times or more with treated water and charged into the reaction tank, and the conditions such as pH, water temperature and NH ₃ -N concentration in the reaction tank are controlled to nitrify and dehydrate in the reaction tank. Although a method for improving the processing efficiency by simultaneously performing nitrogen is proposed (Patent Document 1), returning a large amount of treated water in this way leads to an increase in reaction tank capacity.
Japanese Patent Publication No. 1-222039

  The present invention solves the above-mentioned conventional problems, and in the biological treatment of organic matter-containing water, it is possible to effectively improve the treatment efficiency without remodeling such as adding a carrier, increasing the aeration amount, or adding an aeration tank. An object of the present invention is to provide a biological treatment method and apparatus for organic matter-containing water that can maintain a stable treated water quality after performing a high-load operation.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor added nitric acid (salt) and / or nitrous acid (salt) to the aeration tank, and caused denitrifying bacteria inside the carrier where oxygen did not reach. The present inventors have found that the treatment efficiency can be improved by performing the organic matter decomposition without increasing the carrier filling rate, the aeration tank capacity, and the aeration amount, thereby completing the present invention.

That is, the gist of the present invention is as follows.
In this specification, “nitric acid (salt)” means one or both of “nitric acid” and “nitrate”, and “nitrous acid (salt)” means “nitrite” and “nitrite”. Means either or both. Hereinafter, ““ nitric acid (salt) and / or nitrous acid (salt) ”may be abbreviated as“ NOx ”.

  The biological treatment method for organic matter-containing water according to the present invention (Claim 1) is a method for conducting biological treatment by introducing organic matter-containing water into a single tank type or multistage aeration tank containing a biological carrier and aeration of oxygen-containing gas. , A liquid containing nitric acid (salt) and / or nitrous acid (salt) as an oxygen source is added to the aeration tank, and the organic oxidation of the organic substance by aeration and the decomposition of the organic substance by a denitrification reaction are performed in the aeration tank. It is characterized by that.

  The biological treatment method for organic substance-containing water according to claim 2 is characterized in that, in claim 1, the biological carrier is a carrier that flows by aeration in the aeration tank.

  The biological treatment method for organic matter-containing water according to claim 3 is the biological treatment method according to claim 1 or 2, wherein the aeration tanks are provided in multiple stages in series, and part of the treated water in the latter aeration tank is one of the first to third tanks or It is returned to a plurality of aeration tanks.

The biological treatment method for organic substance-containing water according to claim 4 is the organic carrier load in an aeration tank according to any one of claims 1 to 3, wherein the nitric acid (salt) and / or nitrous acid (salt) -containing liquid is added. The ratio of kg-COD _Cr / m ³ -carrier / day) and dissolved oxygen (mg / L) is 2.0 or more.

The biological treatment method for organic substance-containing water according to claim 5 is the biological treatment method according to any one of claims 1 to 4, wherein 1/6 to 1 of the soluble COD _Cr to be decomposed, which should be decomposed by the denitrification reaction. It is characterized by adding a liquid containing nitric acid (salt) and / or nitrous acid (salt) (NO _x -N conversion) in an amount of 2 times by weight.

  The biological treatment method for organic matter-containing water according to claim 6 is characterized in that, in any one of claims 1 to 5, the filling rate of the biological carrier is 5 to 50% of the volume of the aeration tank.

  The biological treatment method for organic substance-containing water according to claim 7 is characterized in that, in any one of claims 1 to 6, the biological carrier has the shortest side or diameter of 2 mm or more.

  The biological treatment apparatus for organic matter-containing water according to the present invention (invention 8) has an aeration tank containing a biological carrier and means for introducing organic matter-containing water into the aeration tank, and the oxygen-containing gas in the aeration tank. A means for adding a nitric acid (salt) and / or nitrous acid (salt) as an oxygen source to the aeration tank, and biologically oxidizing organic matter by aeration in the aeration tank; It is characterized by decomposing organic matter by denitrification reaction.

  The biological treatment apparatus for organic matter-containing water according to claim 9 is characterized in that, in claim 8, the biological carrier is a carrier that flows by aeration in the aeration tank.

  The biological treatment apparatus for organic substance-containing water according to claim 10 is the biological treatment apparatus according to claim 8 or 9, wherein the aeration tanks are provided in series in multiple stages, and means for returning a part of the treated water in the latter aeration tank to the front aeration tank. It is characterized by having.

The biological treatment apparatus for organic matter-containing water according to claim 11 is the organic carrier load (kg--) according to any one of claims 8 to 10, wherein the nitric acid (salt) and / or nitrous acid (salt) is added. The ratio of COD _Cr / m ³ -carrier / day) and dissolved oxygen (mg / L) is 2.0 or more.

The biological treatment apparatus for organic substance-containing water according to claim 12 is the biological treatment apparatus according to any one of claims 8 to 11, wherein the organic substance is to be decomposed by the denitrification reaction and is 1/6 to 1 of the soluble COD _Cr to be decomposed. / 2 weight times nitric acid (salt) and / or nitrous acid (salt) is added.

  The biological treatment apparatus for organic matter-containing water according to claim 13 is characterized in that, in any one of claims 8 to 12, the filling rate of the biological carrier is 5 to 50% of the volume of the aeration tank.

  The biological treatment apparatus for organic matter-containing water according to claim 14 is characterized in that, in any one of claims 8 to 13, the biological carrier has the shortest side or diameter of 2 mm or more.

  According to the present invention, nitric acid (salt) and / or nitrous acid (salt) is added to the aeration tank instead of oxygen, and the organic matter is removed by denitrification reaction by denitrifying bacteria inside the carrier where oxygen does not reach. By decomposing, it is possible to remove residual organic substances that could not be removed by bacteria near the carrier surface.

  For this reason, in the biological treatment of organic matter-containing water, it is possible to effectively improve the treatment efficiency and maintain a stable treated water quality after performing a high load operation.

  In the present invention, in an existing facility, a simple operation of adding nitric acid (salt) and / or nitrous acid (salt) at high load makes it possible to add a carrier, increase the air flow rate, or add an aeration tank. It is possible to cope with an increase in load without performing the above.

Such a biological treatment method and apparatus for organic matter-containing water according to the present invention is a facility with limited processing capacity such that a soluble COD _Cr concentration remains at 30 mg / L or more in the case of only aeration treatment. This makes it possible to cope with an industrially advantageous increase in high load in facilities where it is difficult to add aeration tanks or blowers.

  Hereinafter, embodiments of a biological treatment method and apparatus for organic matter-containing water according to the present invention will be described in detail with reference to the drawings.

  1-3 is a systematic diagram showing an embodiment of a biological treatment apparatus for organic matter-containing water according to the present invention. 1-3, the same code | symbol is attached | subjected to the member which show | plays the same function.

  The apparatus shown in FIG. 1 is provided with one transient aeration tank (without sludge return) 1 into which a carrier 2 is introduced, and performs biological treatment of raw water (organic matter-containing water). 1, the organic matter in the raw water is oxidized and decomposed under aeration by floating bacteria and carrier-attached bacteria in the aeration tank 1, and the biologically treated water passes through the screen 3 in the aeration tank 1 and is taken out from the pipe 12.

  In FIG. 1, nitric acid (salt) and / or nitrous acid (salt) (NOx) is added to the aeration tank 1 from a pipe 13 to improve biological treatment efficiency.

  2 and 3 divide the aeration tank into two aeration tanks 1A and 1B and adopt a multi-stage treatment system. In the apparatus of FIGS. 2 and 3, the raw water is supplied from the pipe 11 to the first aeration tank 1A. The introduced organic matter in the raw water is oxidatively decomposed under aeration by floating bacteria and carrier-attached bacteria in the aeration tank 1A, and the biologically treated water passes through the screen 3 in the aeration tank 1A and passes through the pipe 14 to the second aeration tank 1B. The residual organic matter in the treated water of the first aeration tank 1A is oxidized and decomposed under aeration by floating bacteria and carrier-attached bacteria in the aeration tank 1B, and the biologically treated water passes through the screen 3 in the aeration tank 1B. And taken out from the pipe 12.

  In such a multi-stage processing method, the foremost (first stage) aeration tank 1A is heavily loaded, which may cause the above-described adverse effects.

  Therefore, in the apparatus of FIG. 2, NOx is added to the first-stage aeration tank 1A from the pipe 13, and the decomposition and removal of the residual organic matter is promoted by the denitrification reaction in the carrier as in the apparatus of FIG.

  Further, in the apparatus of FIG. 3, a part of the treated water in the subsequent aeration tank 1 </ b> B is returned from the pipe 15 to the preceding aeration tank 1 </ b> A. That is, when such multi-stage treatment is applied, self-digestion in the aeration tank 1B in the subsequent stage is promoted, and the amount of sludge generated is reduced, but the concentration of nitrogen flowing out into the treated water (nitric acid, nitrous acid concentration) increases. In such a case, it is preferable to return the treated water in the subsequent aeration tank 1B containing NOx-N to the preceding aeration tank 1A as a NOx source. In this case, the amount of NOx added from outside the system through the pipe 13 can be reduced, or the addition of NOx can be made unnecessary. In the apparatus of FIG. 3, in addition to improving the stability of the treatment, it is possible to reduce the NOx-N concentration of the treated water, and a more efficient treatment can be performed.

  In this way, when the treated water in the subsequent aeration tank is returned to the previous aeration tank, if there is a solid-liquid separation means such as coagulation sedimentation or pressure flotation in the further subsequent stage of the subsequent aeration tank, before the solid-liquid separation Returning the biologically treated water is advantageous in that the solid-liquid separation device can be reduced in size.

  In the present invention, when performing multi-stage treatment, the aeration tank is not limited to two stages, but may be provided in series in three or more stages. However, when NOx is added, the addition of NOx is the first stage with the highest load. The aeration tank is preferably added, and may be added to any one of the first to third aeration tanks or to a plurality of aeration tanks. In addition, it is preferable to return the treated water in the last stage aeration tank having the highest NOx-N concentration of the treated water to the first stage aeration tank having the highest load. It may be returned to any one or a plurality of aeration tanks. This return can be used as an auxiliary or substitute for the added NOx-containing liquid.

  In this way, when a part of the treated water in the subsequent aeration tank is returned to the previous aeration tank, the amount of treated water in the entire apparatus is not excessively increased, and the amount of treated water per apparatus is not reduced. In order to sufficiently obtain the above effect, for example, it is preferable to return about 25 to 200% of the raw water inflow amount of the treated water in the subsequent aeration tank to the previous aeration tank.

  Hereinafter, a mechanism for improving biological treatment efficiency by adding NOx to the aeration tank in the present invention will be described with reference to FIG.

In FIG. 4, reference numeral 10 denotes a porous carrier. With a general aeration amount, oxygen does not reach the inside 10 </ b> A (portion with a dot) of the carrier 10 and is in an oxygen-free state. When NOx is added to the aeration tank, NOx penetrates into the oxygen-free region 10A of the carrier 10 as described above. Further, when an organic substance enters the oxygen-free region 10A, a denitrification reaction by anaerobic denitrifying bacteria occurs using NOx present in the oxygen-free region 10A, and the organic material is decomposed. NOx is decomposed into nitrogen gas, and organic matter is decomposed into CO ₂ and water. As a result, without increasing the carrier filling rate, increasing the aeration volume, or increasing the aeration tank capacity, residual organic substances that could not be removed on the support surface by biological treatment in the aeration tank only by adding NOx. The biological treatment efficiency in the entire aeration tank can be increased by effectively decomposing and removing by the denitrification reaction in the carrier.

  In the present invention, the shape of the carrier held in the aeration tank is arbitrary, and may be any of a spherical shape, a pellet shape, a hollow cylindrical shape, a cubic or rectangular parallelepiped shape, a rod shape, and other irregular shapes.

Further, the material of the carrier is arbitrary, and natural materials, inorganic materials, polymer materials, etc. can be used. Further, it may be a gel material, but preferably it is a porous polyurethane fluid carrier (sponge). A carrier that flows by aeration in an aeration tank such as a carrier. In the case of a fluid carrier, NOx and organic substances are taken into the oxygen-free region inside the carrier by flowing under aeration, and nitrogen gas and water, which are denitrification decomposition products, and CO ₂ are discharged from the oxygen-free region. Can be done efficiently. In this case, the pore diameter of the porous carrier is preferably about 0.01 to 0.5 mm from the viewpoint of the fluidity of the carrier and the efficiency of inflow and outflow of gas and liquid into and out of the carrier.

  In addition, if the size of the carrier is small, the oxygen-free region shown in FIG. 4 cannot be formed. Therefore, both the surface layer region in which oxygen can reach in the carrier and the inner region (oxygen-free region) in which oxygen cannot reach It is preferable that it is large to some extent so that it can be secured. From this point of view, although the carrier depends on its shape, the length of the shortest side or the diameter is preferably 2 mm or more, particularly 3 mm or more. However, if the size of the carrier is excessively large, it is not preferable in terms of fluidity, handling properties, and securing a specific surface area for bacteria to adhere, so the longest side or the diameter should be 10 mm or less. Is preferred.

  The filling rate of the carrier into the aeration tank is appropriately determined according to the load of the aeration tank, but is preferably 5 to 50% (volume%) of the aeration tank volume. When the carrier filling rate is less than 5% or more than 50%, the biological treatment efficiency tends to decrease. From the viewpoint of denitrification activity in the oxygen-free region in the carrier, the carrier filling rate is particularly preferably 5 to 20%.

  Moreover, as NOx added to the aeration tank, any one or more of nitric acid, nitrate, nitrous acid, and nitrite can be used. For example, it is added in the form of an aqueous solution such as sodium nitrate. Is preferable in terms of operation.

The addition of NOx to the aeration tank is appropriately determined according to the amount of organic matter to be removed by the denitrification reaction in the oxygen-free region inside the support by adding NOx. Usually, the carrier-added biological treatment in the aeration tank cannot be removed and remains. Therefore, it is necessary to remove by NOx-N conversion (NO ₃ -N conversion and / or NO ₂ -N conversion) weight by denitrification inside the carrier, and 1/6 to the weight of soluble COD _Cr based on organic matter It is preferable to add 1/2 times, preferably 1/4 to 1/3 times of NOx. With such an addition amount, residual soluble COD _Cr that cannot be removed by the carrier-added biological treatment, It can be effectively decomposed and removed by denitrification reaction in an oxygen-free region inside the carrier.

  By the way, according to the present invention, in order to add NOx to the aeration tank and cause the denitrification reaction inside the carrier, it is necessary to form an oxygen-free region inside the carrier and to allow not only NOx but also organic matter to permeate into the carrier. There is. This condition depends on the volume load of the aeration tank, the carrier filling rate, and the DO, and can be expressed by the relationship between the carrier load of the tank to cause denitrification and DO.

FIG. 5 shows this relationship. Here, when nitrogen removal activity of 0.05 kg-N / m ³ / day or more is obtained, it is assumed that “denitrification occurs in the carrier” and It is shown by. The white circle in the graph is a condition where denitrification does not occur.

From FIG. 5, the ratio of the organic carrier load (kg-COD _Cr / m ³ -carrier / day) and DO (mg / L) in the aeration tank in which NOx is added to cause denitrification in the carrier. It can be seen that denitrification can be caused by setting the ratio to 2.0 or more.

For example, as can be seen from FIG. 6, which is a graph showing the relationship between the possibility of demolding when a 5 mm square sponge carrier is used at a carrier filling rate of 40%, the organic substance volume load in the aeration tank, and DO, the carrier filling rate is 40. %, DO = 4 mg / L, it is necessary to operate at a volume load of 3.2 kg-COD _Cr / m ³ -carrier / day or more.

Further, in the bulk of the aeration tank which attempts to cause the denitrification, solubility _{COD Cr} as a carbon source for the denitrification is _{30mg-COD Cr} / L or more, for example _{30~100mg-COD Cr} / L about remaining It is preferable to control the operating conditions so that NOx is added in the above-described amount of NOx added in order to cause the denitrification reaction more reliably.

  In addition, in order to cause the carrier reaction to occur stably, DO in the bulk of the aeration tank to cause the denitrification reaction is 4.0 mg / L or less, oxygen does not penetrate into the carrier, and the carrier does not penetrate into the carrier. It is preferable to perform aeration in the aeration tank under such a condition that a wide oxygen-free region is formed.

  In this way, even if the operating conditions of the aeration tank are set to those suitable for the growth of denitrifying bacteria, the denitrifying bacteria will grow if the raw water does not contain any essential components for bacterial growth. The organic matter removal efficiency by denitrification is not improved. Therefore, it is possible to stabilize the organic matter removal rate by adding a nutrient to the aeration tank and stably maintaining denitrification in the carrier. In the multistage treatment as shown in FIGS. 2 and 3, when adding a nutrient for denitrifying bacteria, it is desirable to add it to the aeration tank at the forefront (first stage) where denitrification is most advanced.

  As a nutrient, inorganic substances essential for denitrification such as iron, copper, molybdenum, magnesium, potassium, and calcium can be used singly or in combination of two or more.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

Example 1
The raw water was treated using a transient aeration tank (without sludge return) having a capacity of 2.86 L shown in FIG. A carrier made of polyurethane foam of 5 mm square (cube with a side of 5 mm) was used and added so that the carrier filling rate was 20% with respect to the volume of the aeration tank. The tank DO was 1 mg / L, the COD _Cr volumetric load on the aeration tank was 5.6 kg-COD _Cr / m ³ / day, and HRT was operated for 2.4 hours. The raw water COD _Cr concentration was 560 mg / L, and artificial drainage mixed with vegetable extract, fish meat extract, and liquid sugar was used as a substrate.

When operated for one month under these conditions, the soluble COD _{Cr in} the treated water was stable at 57-80 mg-COD _Cr / L.

One month after the start of operation, a 10% by weight aqueous sodium nitrate solution was added to the raw water so that the concentration was 20 mg-N / L. The soluble COD _Cr concentration in the treated water was 25 to 34 mg-COD _Cr / L. Declined.

(Comparative Example 1)
When the operation was continued without adding sodium nitrate under the same conditions as in Example 1, the soluble COD _Cr concentration in the treated water remained 57-80 mg-COD _Cr / L and did not decrease.

(Comparative Example 2)
Under the conditions of Example 1, when the carrier filling rate was increased to 30% and operated at DO> 2 mg / L, the soluble COD _Cr concentration in the treated water decreased to 28-42 mg-COD _Cr / L. The carrier cost and aeration cost are high.

FIG. 7 shows the change over time in the soluble COD _Cr concentration of the treated water in Example 1 and Comparative Examples 1 and 2.

  From Example 1 and Comparative Examples 1 and 2, it can be seen that according to the present invention, it is possible to improve the processing efficiency while suppressing the carrier filling rate and the amount of aeration.

(Example 2)
The raw water was treated by a two-stage biological treatment in which two tanks with a capacity of 2.86 L (no sludge return) were connected in series as shown in FIG. The carrier used was a 5 mm square polyurethane foam similar to that used in Example 1, and was added so as to be 20% of the volume of each aeration tank. DO was 1 mg / L in the front aeration tank, 3 mg / L in the rear aeration tank, and the COD _Cr volumetric load for the entire apparatus was 5.6 kg-COD _Cr / m ³ / day, and the operation was performed at HRT of 2.4 hours. The raw water COD _Cr concentration was 560 mg / L, and artificial drainage mixed with vegetable extract, fish extract, and liquid sugar was used as a substrate.

When operated under this condition for one month, the soluble COD _{Cr in} the treated water was stable at 28-37 mg-COD _Cr / L, but the screen of the previous aeration tank was clogged with slime, so it must be cleaned daily. was there.

Therefore, when a 10% by weight sodium nitrate aqueous solution was added to the raw water so as to be 10 mg-N / L, clogging by slime was resolved, and soluble COD _Cr in the treated water was 28 to 33 mg-COD _Cr / L. It dropped to.

  The nitrate nitrogen concentration in the treated water was stable at 20 mg-N / L.

(Example 3)
The raw water was treated in a two-stage biological treatment in which two tanks with a capacity of 2.86 L (no sludge return) were connected in series as shown in FIG. The carrier used was a 5 mm square polyurethane foam similar to that used in Example 1, and was added so as to be 20% of the volume of each aeration tank. DO was 1 mg / L in the front aeration tank, 3 mg / L in the rear aeration tank, and the COD _Cr volumetric load on the entire apparatus was 5.6 kg-COD _Cr / m ³ / day, and the operation was performed at HRT of 2.4 hours. The raw water COD _Cr concentration was 560 mg / L, and artificial drainage mixed with vegetable extract, fish meat extract, and liquid sugar was used as a substrate. In addition, 40 ml / min corresponding to 50% of the treated water in the latter stage aeration tank (100% of the raw water flow rate) was extracted with a pump and returned to the former stage.

When operated for one month under these conditions, clogging with slime did not occur, and the soluble COD _{Cr in the} treated water was stable at 25 to 35 mg-COD _Cr / L. Furthermore, the nitrate nitrogen concentration of the treated water decreased to 10 mg-N / L.

It is a systematic diagram which shows embodiment of the biological treatment apparatus of the organic substance containing water of this invention. It is a systematic diagram which shows another embodiment of the biological treatment apparatus of the organic substance containing water of this invention. It is a systematic diagram which shows different embodiment of the biological treatment apparatus of the organic substance containing water of this invention. It is explanatory drawing of the denitrification reaction mechanism inside the support | carrier which concerns on this invention. It is a graph which shows the relationship between the possibility of denitrification reaction, organic substance support load, and DO (In the figure, the area | region which attached | subjected the dot is an area | region where denitrification occurs.). It is a graph which shows the relationship between the propriety of denitrification reaction, the organic substance volume load of an aeration tank, and DO (In the figure, the area | region which attached | subjected the dot is an area | region where denitrification occurs.). It is a graph which shows the time-dependent change of the solubility COD _Cr of the treated water in Example 1 and Comparative Examples 1 and 2.

Explanation of symbols

1, 1A, 1B Aeration tank 2 Carrier 3 Screen 10 Porous carrier

Claims (14)

  Nitric acid (salt) and / or nitrous acid (salt) as an oxygen source in a method of biological treatment by introducing organic substance-containing water into a single tank or multi-stage aeration tank containing a biological carrier and aeration of oxygen-containing gas A biological treatment method for organic matter-containing water, which comprises adding a contained liquid to the aeration tank, and performing biological oxidation of the organic substance by aeration in the aeration tank and decomposition of the organic substance by a denitrification reaction.   The biological treatment method for organic matter-containing water according to claim 1, wherein the biological carrier is a carrier that flows by aeration in the aeration tank.   The aeration tank according to claim 1 or 2, wherein a plurality of aeration tanks are provided in series, and a part of the treated water in the latter aeration tank is returned to one of the first to third tanks or a plurality of aeration tanks. A method for biological treatment of organic-containing water. The organic carrier load (kg-COD _Cr / m ³ -carrier / day) of the aeration tank to which the nitric acid (salt) and / or nitrous acid (salt) -containing liquid is added according to any one of claims 1 to 3. The biological treatment method of organic substance containing water characterized by making ratio with dissolved oxygen (mg / L) 2.0 or more. 5. The nitric acid (salt) and / or the sub-oxide in any one of claims 1 to 4, wherein the organic matter should be decomposed by the denitrification reaction, and is 1/6 to 1/2 times by weight the soluble COD _Cr to be decomposed. biological treatment method of organic-containing water, which comprises adding nitric acid (salt) (NO x _-N equivalent) containing liquid.   6. The biological treatment method for organic substance-containing water according to claim 1, wherein a filling rate of the biological carrier is 5 to 50% of the volume of the aeration tank.   The biological treatment method for organic substance-containing water according to any one of claims 1 to 6, wherein the biological carrier has a shortest side or diameter of 2 mm or more.   Nitric acid (salt) as an oxygen source in an apparatus having an aeration tank containing a biological carrier and means for introducing organic substance-containing water into the aeration tank and aspirating oxygen-containing gas in the aeration tank And / or a means for adding nitrous acid (salt) to the aeration tank, wherein organic oxidation is carried out in the aeration tank by organic oxidation of the organic substance and decomposition of the organic substance by denitrification reaction. Water biological treatment equipment.   9. The biological treatment apparatus for organic matter-containing water according to claim 8, wherein the biological carrier is a carrier that flows by aeration in the aeration tank.   10. The biological treatment apparatus for organic matter-containing water according to claim 8, wherein the aeration tanks are provided in series in multiple stages, and have means for returning a part of the treated water in the subsequent aeration tank to the front aeration tank. . The organic carrier load (kg-COD _Cr / m ³ -carrier / day) and dissolved oxygen in the aeration tank to which the nitric acid (salt) and / or nitrous acid (salt) are added according to any one of claims 8 to 10. A biological treatment apparatus for organic matter-containing water, wherein the ratio of (mg / L) to 2.0 or more. 12. The nitric acid (salt) and / or the sub-oxide of any one of claims 8 to 11, wherein the organic matter should be decomposed by the denitrification reaction, the soluble COD _Cr to be decomposed is 1/6 to 1/2 times by weight. A biological treatment apparatus for water containing organic matter, characterized by adding nitric acid (salt).   The biological treatment apparatus for organic matter-containing water according to any one of claims 8 to 12, wherein a filling rate of the biological carrier is 5 to 50% of the volume of the aeration tank.   14. The biological treatment apparatus for organic matter-containing water according to claim 8, wherein the biological carrier has a shortest side or diameter of 2 mm or more.

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