JP5325124B2 - Biological treatment method for nitrogen-containing water and biological treatment apparatus for nitrogen-containing water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for treating nitrogen-containing water biologically, in which the treated water having stable quality can be secured even when the concentration of nitrogen in the water to be treated or the flow rate of the water to be treated is fluctuated. <P>SOLUTION: The method for treating the nitrogen-containing water biologically comprises a step of intermittently adding a hydrogen donor to a reaction tank, into which the water that is to be treated and includes nitric acid or nitrous acid is made to flow, to reduce the nitric acid or nitrous acid into nitrogen gas. The addition rate (v) of the hydrogen donor is set so as to satisfy expression: v=X&times;T&times;(100-D)/(N&times;S<SB>T</SB>&times;D&times;M) (wherein X is the amount of the hydrogen donor to be added per unit time; T is hydraulic residence time; N is a number of intermittent addition cycles of the hydrogen donor; M is the concentration of the hydrogen donor to be added; D is the ratio of the addition time of the hydrogen donor to the time of one cycle of intermittent addition of the hydrogen donor; S<SB>T</SB>is the time to stop the hydrogen donor in the time of one cycle of intermittent addition of the hydrogen donor). <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a biological treatment method for nitrogen-containing water that reduces nitric acid or nitrous acid in water to be treated into nitrogen gas, and a biological treatment apparatus for nitrogen-containing water.

  In recent years, in the field of wastewater treatment, biochemical water treatment has been frequently used in which treatment is performed by changing the pollutants in wastewater to harmless substances using the physiological activity of microorganisms. And the activated sludge method is the mainstream as a biological treatment method of the nitrogen component contained in waste water. In the activated sludge method, for example, a nitrogen component is oxidized by a microorganism to treat it to nitric acid or nitrite nitrogen, and then, in an anaerobic state, denitrification treatment is performed to the nitrogen gas by the microorganism in the presence of a hydrogen donor. . The microorganisms used in these series of treatments are floc-like aggregates. Since this microorganism needs to remain in the reaction system, it is necessary to separate the treated water and the aggregate.

  As a method for separating microorganisms, sedimentation separation has been used for a long time, but recently, a method using membrane separation has also been adopted (see, for example, Patent Document 1). Further, in order to simplify the separation operation, a technique is known in which microbial aggregates are attached in advance to a carrier having good sedimentation (see, for example, Patent Document 2).

  Since the denitrification process requires a hydrogen donor, the denitrification process stops when the hydrogen donor is insufficient in the reaction system. On the other hand, when an excessive amount of hydrogen donor is added, not only is the treatment cost undesirable, but the hydrogen donor leaks into the treated water, leading to deterioration of water quality. From such a viewpoint, a method for controlling the amount of hydrogen donor added in order to add the amount of hydrogen donor added to the reaction system without excess or deficiency has been proposed (see, for example, Patent Documents 3 to 6). .

Japanese Patent Laid-Open No. 11-165182 JP 2007-296499 A Japanese Patent No. 2634478 JP 7-328678 A JP 2003-71492 A Japanese Patent Laid-Open No. 11-104691

  By the way, the treatment capacity in biological treatment increases as the sludge concentration in the reaction tank increases. However, in the case of the activated sludge method (especially in the case of the floating type), there is a problem that separation of treated water and sludge becomes difficult when the sludge concentration increases.

  As a result of intensive studies, the present inventors have given a time concentration gradient of the hydrogen donor in the tank by intermittently adding a necessary amount of the hydrogen donor in the denitrification treatment by the activated sludge method (for example, TOC concentration). 10 mg / L or more), it was found that the settleability of sludge was improved, and treated water and microorganisms could be easily separated by sedimentation separation.

  However, when the required amount of the hydrogen donor changes due to fluctuations in the nitrogen concentration and flow rate in the raw water, if the hydrogen donor is intermittently added only by regular addition, the time of the hydrogen donor in the tank will increase. It becomes difficult to give a concentration gradient, and the sedimentation property of sludge may decrease, or the quality of treated water may become unstable.

  Then, this invention is providing the biological treatment method and biological treatment apparatus of nitrogen-containing water which can ensure the stable treated water quality, even if the nitrogen concentration, flow volume, etc. in to-be-treated water fluctuate.

(1) The present invention is a biological treatment of nitrogen-containing water in which nitric acid or nitrite-containing water to be treated flows into a reactor into which hydrogen donor is intermittently added to reduce the nitric acid or nitrous acid to nitrogen gas. According to an increase or decrease in the amount of nitric acid or nitrous acid determined from the product of the concentration of nitric acid or nitrous acid in the water to be treated flowing into the reaction tank and the amount of water to be treated flowing into the reaction tank, Hydrogen donor addition rate (v), hydrogen donor addition amount (X) required per unit time, total volume of the reaction tank / water flowing into the reaction tank so as to satisfy the following formula (1) The hydraulic residence time (T) determined by the flow rate, the number of intermittent addition cycles of the hydrogen donor obtained by dividing the hydraulic residence time (T) by the time per cycle of intermittent addition consisting of addition and termination of the hydrogen donor. (N), hydrogen donor to be added To set the concentration (M), the intermittent rate of the hydrogen donor addition time for the time of addition per cycle (D), and the intermittent addition of hydrogen donor supply stop time of 1 per cycle time (S _T) A biological treatment method for nitrogen-containing water.
v = X · T · (100−D) / (N · S _T · D · M) (1)

  (2) In the biological treatment method for nitrogen-containing water described in (1) above, the nitric acid or the nitrous acid in the water to be treated flowing into the reaction tank under a constant hydrogen donor addition rate (v). When the amount of nitric acid or nitrous acid obtained from the product of the concentration of nitric acid and the amount of water to be treated flowing into the reaction vessel is increased or decreased, the intermittentness is proportional to the increase or decrease in the amount of nitric acid or nitrous acid. It is preferable to increase or decrease the number of additions (N) and the ratio (D) of the hydrogen donor addition time, respectively.

  (3) In the biological treatment method for nitrogen-containing water described in (2) above, the nitric acid or the nitrous acid in the water to be treated flowing into the reaction tank while the amount of water to be treated flowing into the reaction tank is constant. The nitric acid or nitrous acid obtained from the product of the concentration of the nitric acid or nitrous acid in the treated water flowing into the reaction tank and the amount of treated water flowing into the reaction tank due to the increase or decrease in the concentration of nitric acid When the amount increases or decreases, the number of intermittent additions (N) and the proportion of the hydrogen donor addition time (D) are increased or decreased in proportion to the increase or decrease in the amount of nitric acid or nitrous acid, respectively. Is preferred.

  (4) In the biological treatment method for nitrogen-containing water described in (1) above, the amount of intermittent addition (N) and the ratio (D) of the hydrogen donor addition time are constant, and the amount of water that flows into the reaction vessel is constant. When the concentration of nitric acid or nitrous acid determined from the product of the concentration of nitric acid or nitrous acid in treated water and the amount of water to be treated flowing into the reaction tank increases or decreases, It is preferable to increase or decrease the hydrogen donor addition rate (v) in proportion to the decrease.

  (5) In the biological treatment method for nitrogen-containing water described in (4) above, the nitrogen-containing water further flows into the reaction tank under a constant concentration of nitric acid or nitrous acid in the water to be treated flowing into the reaction tank. The nitric acid or nitrous acid obtained from the product of the concentration of the nitric acid or nitrous acid in the water to be treated flowing into the reaction tank and the amount of water to be treated flowing into the reaction tank due to the increase or decrease in the amount of treated water When the amount increases or decreases, it is preferable to increase or decrease the hydrogen donor addition rate (v) in proportion to the increase or decrease in the amount of nitric acid or nitrous acid.

  (6) In the biological treatment method for nitrogen-containing water according to (1), the water to be treated flows into the reaction tank with the hydrogen donor addition rate (v) and the number of intermittent additions (N) being constant. When the amount of nitric acid or nitrous acid obtained from the product of the concentration of nitric acid or nitrous acid and the amount of water to be treated flowing into the reaction vessel increases or decreases, the amount of nitric acid or nitrous acid increases or decreases. In proportion, it is preferable to increase or decrease the proportion (D) of the hydrogen donor addition time.

  (7) In the biological treatment method for nitrogen-containing water according to any one of (1) to (6) above, the number of intermittent additions (N) is preferably 2.5 or more.

(8) In the biological treatment method for nitrogen-containing water according to (2) or (3) above, as a result of reducing the number of intermittent additions (N), the number of intermittent additions (N) is less than 2.5. In this case, the number of intermittent additions (N) is set to 2.5 or more, and the hydrogen donor supply stop time (S _T ) and the hydrogen donor addition rate (v) are reset so as to satisfy the formula (1). It is preferable to do.

(9) The present invention comprises a reaction tank into which treated water containing nitric acid or nitrous acid flows, and hydrogen donor addition means for intermittently adding a hydrogen donor to the reaction tank, Alternatively, a biological treatment apparatus for nitrogen-containing water that reduces nitrous acid to nitrogen gas, the product of the concentration of nitric acid or nitrous acid in the treated water flowing into the reaction tank and the amount of treated water flowing into the reaction tank Depending on the required increase or decrease in the amount of nitric acid or nitrous acid , the hydrogen donor addition rate (v) and the hydrogen donor addition amount (X) required per unit time so as to satisfy the following formula (1) The hydraulic residence time (T) determined by the total capacity of the reaction tank / the flow rate of water flowing into the reaction tank, and the hydraulic residence time (T) is defined as intermittent addition 1 consisting of addition and stop of a hydrogen donor. Hydrogen donation divided by time per cycle The number of intermittent addition cycles (N), the concentration of hydrogen donor to be added (M), the ratio of hydrogen donor addition time to the time per cycle of intermittent addition (D), and the time per cycle of intermittent addition A biological treatment apparatus for nitrogen-containing water, comprising control means for setting a hydrogen donor supply stop time (S _T ).
v = X · T · (100−D) / (N · S _T · D · M) (1)

  (10) In the biological treatment apparatus for nitrogen-containing water as described in (9) above, the control means is configured such that the nitric acid in the water to be treated flowing into the reaction tank with the hydrogen donor addition rate (v) constant. Alternatively, when the nitric acid or the amount of nitrous acid obtained from the product of the concentration of nitrous acid and the amount of water to be treated flowing into the reaction tank increases or decreases, it is proportional to the increase or decrease of the nitric acid or the amount of nitrous acid. It is preferable to increase or decrease the number of intermittent additions (N) and the ratio (D) of the hydrogen donor addition time, respectively.

  (11) In the biological treatment apparatus for nitrogen-containing water according to (10), the control unit further includes a treatment water flowing into the reaction tank with a constant amount of water to be treated flowing into the reaction tank. The concentration obtained by increasing or decreasing the concentration of nitric acid or nitrous acid is determined from the product of the concentration of nitric acid or nitrous acid in the water to be treated flowing into the reaction tank and the amount of water to be treated flowing into the reaction tank. When the amount of nitric acid or nitrous acid increases or decreases, the number of intermittent additions (N) and the ratio (D) of the hydrogen donor addition time are proportional to the increase or decrease in the amount of nitric acid or nitrous acid, respectively. It is preferable to increase or decrease.

  (12) In the biological treatment apparatus for nitrogen-containing water as described in (9) above, the control means performs the reaction under the condition that the number of intermittent additions (N) and the ratio (D) of the hydrogen donor addition time are constant. When the amount of nitric acid or nitrous acid determined from the product of the concentration of nitric acid or nitrous acid in the water to be treated flowing into the tank and the amount of water to be treated flowing into the reaction tank increases or decreases, It is preferable to increase or decrease the hydrogen donor addition rate (v) in proportion to an increase or decrease in the amount of nitric acid.

  (13) In the biological treatment apparatus for nitrogen-containing water according to (12), the control means is further configured so that the concentration of nitric acid or nitrous acid in the water to be treated flowing into the reaction tank is constant. Since the amount of water to be treated flowing into the reaction tank is increased or decreased, the concentration of nitric acid or nitrous acid in the water to be treated flowing into the reaction tank and the product of the amount of water to be treated flowing into the reaction tank are determined. When the amount of nitric acid or nitrous acid increases or decreases, it is preferable to increase or decrease the hydrogen donor addition rate (v) in proportion to the increase or decrease of the amount of nitric acid or nitrous acid.

  (14) In the biological treatment apparatus for nitrogen-containing water as described in (9) above, the control means is provided in the reaction tank with the hydrogen donor addition rate (v) and the intermittent addition number (N) being constant. When the amount of nitric acid or nitrous acid obtained from the product of the concentration of nitric acid or nitrous acid in the treated water flowing in and the amount of treated water flowing into the reaction tank increases or decreases, the amount of nitric acid or nitrous acid It is preferable to increase or decrease the proportion (D) of the hydrogen donor addition time in proportion to the increase or decrease of the hydrogen donor.

  (15) In the biological treatment apparatus for nitrogen-containing water according to any one of (9) to (14), the control unit may set the number of intermittent additions (N) to 2.5 or more. preferable.

(16) In the biological treatment apparatus for nitrogen-containing water according to (10) or (11), the control means decreases the intermittent addition number (N), so that the intermittent addition number (N) is 2. When the number of intermittent additions (N) is 2.5 or more, the hydrogen donor supply stop time (S _T ) and the hydrogen donor addition rate (S _T ) are satisfied so that the formula (1) is satisfied. It is preferable to reset v).

  According to the present invention, stable treated water quality can be ensured even if the nitrogen concentration or flow rate in the water to be treated fluctuates.

It is a schematic block diagram which shows an example of the biological treatment apparatus of nitrogen-containing water which concerns on this embodiment. It is a schematic block diagram which shows another example of the biological treatment apparatus of nitrogen-containing water which concerns on this embodiment. It is a schematic block diagram which shows another example of the biological treatment apparatus of nitrogen-containing water which concerns on this embodiment. It is a figure which shows the change of the MLSS density | concentration with respect to the test elapsed days of Example 1. FIG. It is a figure which shows the change of the process speed of the denitrification process with respect to the test elapsed days of Example. (A) is a figure showing the density | concentration change of the methanol and nitrate ion of a 1st denitrification reaction tank, (B) is a figure showing the density | concentration change of the methanol and nitrate ion of a 2nd denitrification reaction tank. It is a figure which shows the result of the nitrogen concentration in the treated water of Examples 3-5. It is a figure which shows the relationship between the intermittent addition cycle number of a hydrogen donor, and a treated water quality.

  Hereinafter, embodiments of the present invention will be described. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

  FIG. 1 is a schematic configuration diagram illustrating an example of a biological treatment apparatus for nitrogen-containing water according to the present embodiment. A biological treatment apparatus 1 for nitrogen-containing water shown in FIG. 1 includes a denitrification reaction tank 10, an oxidation tank 12, a precipitation treatment tank 14, a pump 16 as a hydrogen donor addition means, a tank 18, and a hydrogen donor. Addition line 20, treated water inflow lines 22a, 22b, 22c, treated water discharge line 24, sludge return line 26, flow rate sensor 28, TN (total nitrogen) sensor 30, and control unit 32 , Are provided. The flow rate sensor 28 and the TN sensor 30 and the control unit 32 are electrically connected. The control unit 32 and the pump 16 are also electrically connected.

  A treated water inflow line 22 a is connected to a treated water inlet (not shown) of the denitrification reaction tank 10. A hydrogen donor addition line 20 is connected via a pump 16 between a hydrogen donor inlet (not shown) of the denitrification reaction tank 10 and an outlet (not shown) of the tank 18. A treated water inflow line 22b is connected between the outlet (not shown) of the denitrification reaction tank 10 and the inlet (not shown) of the oxidation tank 12, and the outlet (not shown) of the oxidation tank 12 and the precipitation processing tank 14 are connected. The inflow line 22c to be treated is connected to the inlet (not shown). A treated water discharge line 24 is connected to a treated water outlet (not shown) of the precipitation treatment tank 14. A sludge return line 26 is connected between the sludge outlet (not shown) of the settling tank 14 and the treated water inflow line 22a.

  Below, operation | movement of the biological treatment apparatus 1 of nitrogen-containing water of this embodiment is demonstrated.

  The treated water containing nitric acid (nitrate ions) and nitrous acid (nitrite ions) is supplied to the denitrification reaction tank 10 through the treated water inflow line 22a. When the treated water passes through the treated water inflow line 22a, the flow rate of the treated water (including return sludge) supplied to the denitrification reaction tank 10 by the flow sensor 28 and the TN sensor 30 and the treated water. The total nitrogen concentration in the water is detected, and data is transmitted to the control unit 32. Although details will be described later, based on the data, the control unit 32 controls operating conditions such as operation and stoppage of the pump, and the hydrogen donor is intermittently added to the denitrification reaction tank 10.

  When methanol is used as the hydrogen donor, in the denitrification reaction tank 10, nitric acid and nitrous acid in the water to be treated are reduced to nitrogen gas by the reaction shown in the following reaction formula.

2NO ₂ ⁻ + CH ₃ OH → N ₂ + CO ₂ + H ₂ O + 2OH ^{−
_{6NO 3 - + 5CH 3 OH →}} 3N 2 + 5CO 2 + 7H 2 O + 6OH -

  The first treated water treated in the denitrification reaction tank 10 is supplied to the oxidation tank 12 through the treated water inflow line 22b. In many cases, since the hydrogen donor is added to the denitrification reaction tank 10 in a slightly excessive amount, the hydrogen donor may remain in the water to be treated. In the oxidation tank 12, oxygen is supplied by aeration, and mainly the hydrogen donor in the water to be treated is oxidized.

  The second treated water treated in the oxidation tank 12 passes through the treated water inflow line 22c and is supplied to the precipitation treatment tank 14. In the sedimentation treatment tank 14, sludge in the water to be treated is separated and (final) treated water is obtained from the treated water discharge line 24, and the separated sludge is supplied to the denitrification reaction tank 10 through the sludge return line 26. Is done. In the case where organic nitrogen or ammonia is contained in the water to be treated as in the embodiment described later, a nitrification reaction tank is installed in the previous stage of the denitrification reaction tank 10, and the separated sludge is stored in the nitrification tank. Preferably returned.

  Below, the setting method of the intermittent addition conditions of a hydrogen donor in the denitrification reaction tank 10 is demonstrated.

For example, when waste water (treated water) having a concentration of 100 g (NO ₃ / NO ₂ ) −N / m ³ flows into the 1 m ³ denitrification reaction tank 10 with the amount of treated water of 10 m ³ / d. In addition, when all of nitric acid and nitrous acid are removed, if the hydrogen donor is methanol, the amount of methanol added is generally 2.4 to 3.3 of the amount of nitrogen contained in the inflowing nitrate ions and nitrite ions. Since it is 0 times (weight ratio), the addition amount of methanol is set to 3.0 times here. In the present embodiment, the control unit 32 causes the hydrogen donor addition rate (v), the amount of hydrogen donor to be added per unit time (X), and the denitrification reaction so as to satisfy the following formula (1). Hydraulic retention time (T) and hydraulic retention time (T) determined by the total capacity of the tank / the flow rate of water flowing into the denitrification reaction tank are calculated per cycle of intermittent addition consisting of hydrogen donor addition and stoppage. Number of hydrogen donor intermittent addition cycles divided by time (N), concentration of hydrogen donor to be added (M), ratio of hydrogen donor addition time to time per cycle of intermittent addition (D), and intermittent addition 1 A hydrogen donor feed stop time (S _T ) in time per cycle is set. The hydrogen donor addition rate (v) in this specification is synonymous with the average flow rate of the hydrogen donor to be added.
v = X · T · (100−D) / (N · S _T · D · M) (1)

  Further, the hydrogen donor may be added by the pump 18 or may be simply dropped by gravity without installing the pump 18. In the case of gravity drop addition, a valve is installed in place of the pump 18, and the hydrogen donor addition rate (v) is adjusted by the valve.

The amount (X) of hydrogen donor required per unit time is 10 m ³ / d × 100 g (NO ₃ / NO ₂ ) −N / m ³ × 3 times = 3 kg / d, and the hydraulic residence time ( T) is 1 m ³ ÷ 10 m ³ /d=0.1d. Further, when the ratio (D) of the hydrogen donor addition time to the time per cycle of intermittent addition is set to 5% and the number of intermittent addition cycles (N) is set to 4 cycles, the time of one cycle of intermittent addition is 0.1 d ÷ Since 4 cycles = 0.025d, the hydrogen donor supply stop time (S _T ) in the time per cycle of intermittent addition is 0.025d × (1-5 ÷ 100) = 0.02375d. When the concentration (M) of the hydrogen donor to be added is 500 kg / m ³ , the hydrogen donor addition rate (v) is 3 × 0.1 × (100−5) ÷ ( 4 × 0.02375 × 5 × 500) = 0.12 m ³ / d. As described above, conditions for intermittent addition of hydrogen donor (substantially pump operating conditions) are determined. Based on the intermittent addition conditions of the hydrogen donor determined in this manner, the quality of the treated water can be improved by intermittently adding the hydrogen donor.

Next, the case where the nitric acid / nitrous acid concentration of the water to be treated and the amount of the water to be treated are changed will be described. For example, when the amount of water to be treated is constant and the concentration of nitric acid and nitrous acid in the water to be treated is 200 g (NO ₃ / NO ₂ ) −N / m ³ , which is twice the above condition, the present embodiment (control method) In 1), the hydrogen donor addition rate (v) is constant, the ratio (D) of the hydrogen donor addition time to the time per cycle of intermittent addition (D) and the number of cycles of intermittent addition (N) are set as nitric acid. Increase in proportion to the increase in the amount of nitric acid and nitrous acid determined by the product of the concentration of nitrous acid and the amount of water to be treated (because the amount of water to be treated is constant, the concentration of nitric acid and nitrous acid is substantially increased). That is, the ratio (D) of the hydrogen donor addition time to the time per cycle of intermittent addition is the above set value 5% × 2 (times) = 10%, and the number of intermittent addition cycles (N) is the above set value 4 cycles. X2 (times) = 8 is set. The addition amount (X) of the hydrogen donor required per unit time is 10 m ³ / d × 200 g (NO ₃ / NO ₂ ) −N / m ³ × 3 times = 6 kg / d. In addition, since the hydraulic retention time (T) does not change even if the nitric acid / nitrite concentration of the water to be treated increases, if the concentration (M) of the hydrogen donor to be added is not changed, the above formula (1) Thus, the hydrogen donor supply stop time (S _T ) per cycle of intermittent addition is 6 × 0.1 × (100−10) ÷ (8 × 0.12 × 10 × 500 = 0.01125d). . on the other hand, when changing the concentration (M) of the hydrogen donor to be added, according to the value of M (1) wherein the hydrogen donor supply stop time in the time per intermittent addition cycle so as to satisfy the (S _T Stable treated water quality can be ensured by performing intermittent addition of the hydrogen donor based on the intermittent addition condition of the hydrogen donor thus determined.

  In the above description, the case where the amount of nitric acid / nitrous acid (substantially nitric acid / nitrous acid concentration) is increased is described as an example. However, when the amount of nitric acid / nitrous acid decreases, the hydrogen donor addition rate (v) is increased. As a constant, the ratio (D) of the hydrogen donor addition time to the time per cycle of intermittent addition (D) and the number of intermittent addition cycles (N) may be reduced in proportion to the decrease in the amount of nitric acid and nitrous acid.

  Further, even when the amount of water to be treated is increased or decreased while the nitric acid / nitrite concentration of the water to be treated is constant, the hydrogen donor addition rate (v) is constant, and the hydrogen donor with respect to the time per cycle of intermittent addition Increase or decrease in the amount of nitric acid / nitrous acid determined by the product of the nitric acid / nitrous acid concentration of the water to be treated and the amount of water to be treated (Nitrate / nitrous acid) Since the concentration is constant, it may be increased or decreased substantially in proportion to the increase or decrease in the amount of water to be treated.

In another embodiment (control method 2), for example, the nitric acid / nitrite concentration of treated water is doubled 200 g (NO ₃ / NO ₂ ) −N / If it becomes m ^3, the intermittent ratio of the hydrogen donor addition time for the time of addition per cycle (D), and intermittent addition number of cycles (N) constant, a hydrogen donor additive rate (v), the water to be treated In proportion to the increase in the amount of nitric acid and nitrous acid determined by the product of the concentration of nitric acid and nitrous acid and the amount of treated water (the amount of treated water is constant, so the concentration of nitric acid and nitrous acid increases substantially) . That is, the hydrogen donor addition rate (v) is set to the above set value 0.12 m ³ / d × 2 (times) = 0.24 m ³ / d. The addition amount (X) of the hydrogen donor required per unit time is 10 m ³ / d × 200 g (NO ₃ / NO ₂ ) −N / m ³ × 3 times = 6 kg / d. In addition, since the hydraulic residence time does not change even if the concentration of nitric acid and nitrous acid in the water to be treated is increased, if the concentration (M) of the hydrogen donor to be added is not changed, the above equation (1) The hydrogen donor supply stop time (S _T ) in the time per one addition cycle is 6 × 0.1 × (100−5) ÷ (4 × 0.24 × 5 × 500 = 0.02375d. When changing the concentration (M) of the hydrogen donor to be added, the hydrogen donor supply is stopped at the time per cycle of intermittent addition so as to satisfy the above formula (1) according to the value of the hydrogen donor concentration (M). Time (S _T ) may be set, and stable treatment water quality can be ensured by performing intermittent addition of the hydrogen donor based on the intermittent addition condition of the hydrogen donor thus determined.

  In the above description, the case where the amount of nitric acid / nitrous acid (substantially nitric acid / nitrous acid concentration) increases is described as an example. However, when the amount of nitric acid / nitrous acid decreases, the hydrogen with respect to the time per cycle of intermittent addition The ratio (D) of the donor addition time and the number of intermittent addition cycles (N) may be constant, and the hydrogen donor addition rate (v) may be decreased in proportion to the decrease in the amount of nitric acid / nitrite.

  Further, even when the amount of water to be treated is increased or decreased while the nitric acid / nitrite concentration of the water to be treated is constant, the ratio (D) of the hydrogen donor addition time to the time per cycle of intermittent addition, the number of intermittent addition cycles (N) is constant, and the hydrogen donor addition rate (v) is increased or decreased (nitric acid / nitrous acid) determined by the product of the nitric acid / nitrous acid concentration of the water to be treated and the amount of water to be treated. Since the concentration is constant, it may be increased or decreased substantially in proportion to the increase or decrease in the amount of water to be treated.

In another embodiment (control method 3), for example, the nitric acid / nitrous acid concentration of the treated water is doubled from the above conditions by 200 g (NO ₃ / NO ₂ ) −N / m ³ , the hydrogen donor addition rate (v) and the number of intermittent addition cycles (N) were constant, and the ratio (D) of the hydrogen donor addition time to the time per cycle of intermittent addition was determined as the water to be treated. In proportion to the increase in the amount of nitric acid and nitrous acid determined by the product of the concentration of nitric acid and nitrous acid and the amount of treated water (the amount of treated water is constant, so the concentration of nitric acid and nitrous acid increases substantially) . That is, the ratio (D) of the hydrogen donor addition time to the time per cycle of intermittent addition is set to the above set value 5% × 2 (times) = 10%. The addition amount (X) of the hydrogen donor required per unit time is 10 m ³ / d × 200 g (NO ₃ / NO ₂ ) −N / m ³ × 3 times = 6 kg / d. In addition, since the hydraulic residence time does not change even if the concentration of nitric acid and nitrous acid in the water to be treated is increased, if the concentration (M) of the hydrogen donor to be added is not changed, the above equation (1) The hydrogen donor supply stop time (S _T ) in the time per addition cycle is 6 × 0.1 × (100−10) ÷ (4 × 0.12 × 10 × 500 = 0.0225d. When changing the concentration (M) of the hydrogen donor to be added, supply of the hydrogen donor at a time per cycle of intermittent addition so as to satisfy the above formula (1) according to the value of the hydrogen donor concentration (M). A stop time (S _T ) may be set, and stable treatment water quality can be ensured by performing intermittent addition of the hydrogen donor based on the intermittent addition condition of the hydrogen donor thus determined.

  In the above, the case where the amount of nitric acid / nitrous acid (substantially nitric acid / nitrous acid concentration) is increased is described as an example. However, when the amount of nitric acid / nitrous acid decreases, the hydrogen donor addition rate (v), The number of intermittent addition cycles (N) may be constant, and the ratio (D) of the hydrogen donor addition time to the time per cycle of intermittent addition may be reduced in proportion to the decrease in the amount of nitric acid / nitrite.

  In addition, even if the amount of water to be treated increases or decreases while the concentration of nitric acid and nitrous acid is constant, the hydrogen donor addition rate (v) and the number of intermittent addition cycles (N) are constant and one cycle of intermittent addition is performed. Increase or decrease in the amount of nitric acid / nitrous acid determined by the product of the nitric acid / nitrous acid concentration of the water to be treated and the amount of water to be treated (the nitric acid / nitrous acid concentration) Therefore, it may be increased or decreased in proportion to the increase or decrease of the amount of water to be treated.

  Here, when the amount of nitric acid / nitrite obtained from the product of the nitric acid / nitrite concentration of the water to be treated and the amount of water to be treated is increased or decreased, stable treatment can be achieved by any of the above control methods 1 to 3. Water quality can be ensured. However, when the concentration of treated water increases and the concentration of nitric acid and nitrous acid in treated water increases, it is possible to secure more stable treated water quality than the control methods 2 and 3 when the control method 1 is performed. . In addition, when the amount of water to be treated is increased or decreased while the concentration of nitric acid and nitrous acid is constant, the ratio of hydrogen donor addition time to the time per cycle of intermittent addition (D) and the number of intermittent addition cycles It is preferable to implement the control method 2 in that it is easy to control with (N) being constant.

  Next, the number of intermittent addition cycles (N) of the hydrogen donor will be described. In the intermittent addition cycle number (N), when the amount of hydrogen donor added within the hydraulic retention time (T) of the denitrification reaction layer 10 is the same, the higher the intermittent addition cycle number (N), the better the treated water quality. On the other hand, as the number of intermittent addition cycles (N) is smaller, the quality of the treated water is worsened. This is because when the hydrogen donor has a temporal concentration gradient in the denitrification reaction layer 10 than the intermittent addition of the hydrogen donor, the concentration of the hydrogen donor becomes zero (zero) if the intermittent addition cycle number (N) is small. This is because the time required for the denitrification process is not performed. For example, when the nitrogen concentration in the denitrified treated water is 10 mg N / L or less, it is desirable to set the number of intermittent addition cycles (N) to 2.5 or more, and if the treated water quality is more important. 3.5 or more is more desirable. On the other hand, when the number of intermittent addition cycles (N) is large, the time when the hydrogen donor concentration becomes zero is shortened and the water quality is improved, but the width of the temporal concentration gradient of the hydrogen donor is reduced in the denitrification reaction layer 10. And the sedimentation property of sludge becomes worse. In consideration of the sedimentation property of the sludge, the width of the temporal concentration gradient of the hydrogen donor in the denitrification reaction tank 10 is desirably 10 mg / L or more in terms of the TOC concentration. Therefore, the number of intermittent addition cycles (N) Is preferably set such that the width of the temporal concentration gradient of the hydrogen donor in the denitrification reaction tank 10 is 10 mg / L or more in terms of the TOC concentration.

In addition, it takes time for the hydrogen donor concentration to be zero (including near zero) in order to improve sedimentation. When the number of intermittent addition cycles (N) is large, continuous injection is approached, making it difficult to control the hydrogen donor concentration to near zero. Therefore, also from this viewpoint, the upper limit of the number of intermittent addition cycles (N) is determined. Usually, the hydrogen donor is added about 1 to 20% more than the theoretical consumption. For example, when 10% more hydrogen donors are added to the required amount of hydrogen donors, 10% of the hydrogen donors are discharged to the subsequent stage by the incoming treated water during the time per cycle of intermittent addition. In this case, the hydrogen donor concentration becomes zero (including near zero). That is, the hydrogen donor supply stop time (S _T ) in the time per cycle of intermittent addition is determined by the total capacity of the denitrification reaction tank / the flow rate of water flowing into the denitrification reaction tank (T) It is not preferable to set the number of intermittent addition cycles (N) or the ratio (D) of the hydrogen donor addition time with respect to the time per one cycle of intermittent addition, which is less than 10%. Therefore, in this example, when the ratio (D) of the hydrogen donor addition time to the time per cycle of intermittent addition is 5%, the number of cycles is set to (100-5) /10%=9.5 or less. It is desirable. In the case where 5% more hydrogen donor is added to the required hydrogen donor, it is desirable to set it to 19 or less. Thus, the number of intermittent addition cycles (N) is such that the width of the temporal concentration gradient of the hydrogen donor is 10 mg / L or more in terms of the TOC concentration, and the hydrogen donor concentration is zero (including near zero). It is desirable to be determined within a range including time.

  In addition, as exemplified above, when the number of intermittent addition cycles (N) is decreased in proportion to the decrease in the amount of nitric acid / nitrous acid obtained from the product of the nitric acid / nitrous acid concentration of the water to be treated and the amount of water to be treated When the number of intermittent addition cycles (N) is less than 2.5, the number of intermittent addition cycles (N) is set to 2.5 or more, and each parameter is set so as to satisfy the above formula (1). It is preferable to reset. Further, the ratio (D) of the hydrogen donor addition time with respect to the time per one cycle of intermittent addition and the number (N) of the intermittent addition cycles become values that cannot form the above-described time of zero (including near zero). In this case, the parameters are reset so as to satisfy the above-described expression (1) so that the range including the time that is zero (including the vicinity of zero) is included.

  The intermittent addition of the hydrogen donor may be controlled by combining the above control methods 1 to 3. For example, when the control method 1 is performed when the concentration of nitric acid and nitrous acid in the water to be treated is reduced, the number of intermittent addition cycles (N) is reduced. Therefore, when the number of intermittent addition cycles (N) reaches 2.5, if a further decrease in the concentration of nitric acid / nitrous acid in the water to be treated is recognized, control method 2 or 3 is performed.

Moreover, also when the nitric acid and nitrous acid density | concentration of to-be-processed water and the to-be-processed water quantity increase / decrease simultaneously, control by the said control methods 1-3, or a combination is possible. For example, the amount of water to be treated is 10 m ³ / d, the concentration of nitric acid / nitrite in treated water is 100 g (NO ₃ / NO ₂ ) -N / m ^{3, the} amount of water to be treated is 20 m ³ / d, and the concentration of nitric acid and nitrous acid in treated water When the control method 1 is carried out when the amount is changed to 200 g (NO ₃ / NO ₂ ) −N / m ³ , the amount of nitric acid / nitrite obtained from the product of the nitric acid / nitrite concentration of the water to be treated and the amount of water to be treated is In the above formula (1), the hydrogen donor addition rate (v) is constant, and the ratio (D) of the hydrogen donor addition time to the time per cycle of intermittent addition and the intermittent addition cycle The number (N) is increased in proportion to the increase in the concentration of nitric acid and nitrous acid in the water to be treated. That is, the ratio (D) of the hydrogen donor addition time to the time per cycle of intermittent addition is the above set value 5% × 4 (times) = 20%, and the number of intermittent addition cycles (N) is the above set value 4 cycles. X4 (times) = 16 is set. The amount (X) of hydrogen donor required per unit time is 3 kg / d × 4 (times) = 12 kg / d. The hydraulic retention time (T) is 0.1d / 2 = 0.05d. When the concentration (M) of the hydrogen donor to be added is not changed, the hydrogen donor supply stop time (S _T ) in the time per cycle of intermittent addition is 12 × 0.05 according to the above formula (1). X (100-20) / (16 * 0.12 * 20 * 500 = 0.0005d).

For example, when controlling by a combination of the control methods 1 and 2, first, the control method 1 is performed on the assumption that the amount of water to be treated is constant and the concentration of nitric acid and nitrous acid in the water to be treated has doubled. Each parameter is obtained. And each parameter at the time of implementing the control method 2 by amending that the amount of to-be-processed water doubled is calculated | required. The parameters in this case are as follows: the ratio of hydrogen donor addition time to the time per cycle of intermittent addition (D) is 10%, the number of intermittent addition cycles (N) is 8 cycles, and the hydrogen donor at the time per cycle of intermittent addition The supply stop time (S _T ) is 0.0056d.

Thus, when the control method 1 is implemented and when the combination of the control methods 1 and 2 is implemented, the calculated parameter values are different. In such a case, the hydrogen in the time per cycle of intermittent addition is different. Control method in which the donor supply stop time (S _T ) can be reduced, and the ratio (D) of the hydrogen donor addition time to the time per cycle of intermittent addition and the value of the number of intermittent addition cycles (N) do not vary as much as possible. Is preferably adopted. When the value of the hydrogen donor supply stop time ( _ST ) per cycle of intermittent addition increases, the time during which the concentration of the hydrogen donor in the denitrification reaction layer 10 becomes zero becomes longer, and the zero time is reached. The amount of nitric acid and nitrous acid that flows out as treated water will increase. Moreover, if the ratio of the hydrogen donor addition time to the time per one cycle of intermittent addition (D) and the value of the number of intermittent addition cycles (N) vary greatly, the sedimentation property of sludge decreases.

  In the case of continuous addition of a hydrogen donor, which is a general technique, the method of increasing the amount of hydrogen donor according to the increase in the concentration of nitric acid and nitrous acid can only increase the addition rate of the hydrogen donor. However, in intermittent addition, control combining the above parameters is possible.

  Further, the width of the temporal concentration gradient of the hydrogen donor can also be improved by dividing the denitrification reaction tank 10 into a plurality of parts (for example, see FIG. 3). When the denitrification reaction tank 10 is divided into a plurality of parts, the preceding denitrification reaction tank 10 is made smaller and the hydrogen donor is intermittently added to the previous stage under the condition of intermittent addition of the hydrogen donor in the single denitrification reaction tank 10. By doing so, the temporal concentration gradient of the hydrogen donor can be increased. In addition, when the size of the front tank is equal to the size of the rear tank, the temporal concentration gradient of the hydrogen donor is reduced, but the quality of the treated water is improved. From these viewpoints, the size of the front tank is preferably set to be 1/3 or less of the size of the rear tank. In addition, as the number of divisions increases, the respective effects become more prominent, but the processing cost may increase because the operating power required for the reaction vessel increases. Therefore, the number of divisions is preferably 5 or less, and more preferably 3 or less.

  Further, the time during which the hydrogen donor concentration is zero (including near zero) can be improved by dividing the denitrification reaction tank 10 into a plurality of parts (see, for example, FIG. 3). When the denitrification reaction tank 10 is divided into a plurality of parts, the preceding denitrification reaction tank 10 is made smaller and the hydrogen donor is intermittently added to the previous stage under the condition of intermittent addition of the hydrogen donor in the single denitrification reaction tank 10. As a result, the hydraulic retention time required by the total volume of the previous reaction tank / the flow rate of water flowing into the previous reaction tank is shortened, so that it is easy to push out to the subsequent stage, and the hydrogen donor concentration is zero (including near zero). ).

  In controlling the intermittent operation of the hydrogen donor in the present embodiment, the hydrogen donor concentration may be detected using a sensor that directly detects the concentration of the hydrogen donor in the denitrification reaction tank 10, The intermittent operation of the hydrogen donor can also be controlled based on the result of measuring the concentration of nitric acid and nitrous acid. It is also possible to measure the pH and control the intermittent operation of the hydrogen donor based on the result.

  For example, when the nitric acid / nitrous acid concentration is measured to control the intermittent operation of the hydrogen donor, the nitric acid / nitrous acid concentration in the water to be treated in this embodiment is, for example, the nitric acid / nitrous acid flowing into the denitrification reaction tank 10. Although it may be measured by a method of directly detecting the nitric acid concentration, it may be indirectly estimated by a TN sensor 30 (which may be an ammonia sensor or the like). The treated water flow rate is detected by, for example, the flow rate sensor 28. These pieces of data are transmitted to the control unit 32. The control unit 32 determines the amount of nitric acid / nitrous acid from the product of the concentration of nitric acid / nitrite in the water to be treated and the amount of water to be treated. The nitric acid / nitrous acid concentration data in the for-treatment water and the amount of the for-treatment water are sent to the control unit 32 at predetermined time intervals, and an increase or decrease in the amount of nitric acid / nitrite for a predetermined elapsed time is calculated. Then, according to the increase or decrease in the calculated amount of nitric acid / nitrite, the control unit 32 sets various parameters as described above, and controls the intermittent addition of the hydrogen donor (substantially) The operating conditions of the pump 16 are controlled).

  In the present embodiment, when the pH is measured to control the intermittent operation of the hydrogen donor, in this embodiment, the hydrogen donor concentration is determined using a sensor that directly detects the hydrogen donor concentration in the denitrification reaction tank 10. Although it may be detected, the concentration of the hydrogen donor may be indirectly detected from the pH value in the denitrification reaction tank 10 using a pH sensor or the like. When there is sufficient hydrogen donor in the denitrification reaction tank 10 and the denitrification reaction proceeds, the alkalinity is supplied by the reaction, so the pH tends to increase. If the donor is insufficient, the denitrification reaction is stopped, so the alkalinity is not supplied, and the pH is lower than when the denitrification reaction is in progress. By detecting this change in pH with a pH sensor, the concentration of the hydrogen donor can be indirectly detected.

  When the hydrogen donor concentration in the denitrification reaction tank 10 is measured to control the intermittent operation of the hydrogen donor, the hydrogen donor concentration in the denitrification reaction tank 10 at the start of hydrogen donor addition and in the denitrification reaction tank 10 is determined. When the hydrogen donor is close to zero, that is, when the concentration gradient of the monitored hydrogen donor is sufficient, it shows a constant value according to the denitrification reaction rate of the zeroth order reaction. As shown in the Michaelis-Menten equation, the reaction rate decreases as the substrate concentration decreases, so the time difference from when the inflection point is detected is read as the time per cycle of intermittent hydrogen donor addition, and hydrogen is donated. When the body concentration is near zero, the pump 16 is activated and a hydrogen donor is added. And the value of the number of intermittent addition cycles (N) obtained by dividing the hydraulic residence time of the denitrification reaction tank 10 by the time per cycle of the intermittent addition described above is 2.5 or more (preferably 3.5 or more). Thus, the hydrogen donor addition time and the hydrogen donor addition rate are increased when the number of cycles is larger than the number of cycles set arbitrarily (5 cycles, etc.), and decreased when the number of cycles is small. Control. By controlling in this way, intermittent addition can be controlled while improving the water quality by controlling the time near zero.

  FIG. 2 is a schematic configuration diagram illustrating another example of the biological treatment apparatus for nitrogen-containing water according to the present embodiment. The biological treatment apparatus 2 for nitrogen-containing water shown in FIG. 2 has the same configuration as the biological treatment apparatus 1 for nitrogen-containing water shown in FIG. 1 except that a nitrification reaction tank 34 is provided. The biological treatment apparatus 2 for nitrogen-containing water shown in FIG. 2 is suitable when the water to be treated contains organic nitrogen, ammonium ions, etc., and the organic nitrogen and ammonium ions are aerobic in the nitrification reaction tank 34. Can be oxidized (in the presence of oxygen) to nitric acid or nitrous acid. Although the TN sensor 30 is installed in the nitrification reaction tank 34, the TN sensor 30 may be installed anywhere as long as it can detect the concentration of nitric acid and nitrous acid in the water to be treated flowing into the denitrification reaction tank 10. .

  A treated water inflow line 22 a is connected to a treated water inlet (not shown) of the nitrification reaction tank 34. A treated water inflow line 22b is connected between the treated water outlet (not shown) of the nitrification reaction tank 34 and the treated water inlet (not shown) of the denitrification reaction tank 10. A hydrogen donor addition line 20 is connected via a pump 16 between a hydrogen donor inlet (not shown) of the denitrification reaction tank 10 and an outlet (not shown) of the tank 18. A treated water inflow line 22c is connected between the outlet (not shown) of the denitrification reaction tank 10 and the inlet (not shown) of the oxidation tank 12, and the outlet (not shown) of the oxidation tank 12 and the precipitation treatment tank 14 are connected. An inlet line (22d) to be treated is connected to the inlet (not shown). A treated water discharge line 24 is connected to the treated water outlet of the precipitation treatment tank 14. A sludge return line 26 is connected between the sludge outlet of the sedimentation tank 14 and the treated water inflow line 22a.

  Below, operation | movement of the biological treatment apparatus 2 of nitrogen-containing water of this embodiment is demonstrated.

  The treated water is supplied to the nitrification reaction tank 34 from the treated water inflow line 22a. In the nitrification reaction tank 34, organic nitrogen, ammonia and the like in the water to be treated are mainly oxidized aerobically (in the presence of oxygen) to nitric acid or nitrous acid.

  The nitrification reaction tank 34 is filled with a microorganism-supporting carrier obtained by supporting a microorganism film containing nitrifying bacteria on a carrier. In addition, an air introduction pipe (not shown) is connected in the nitrification reaction tank 34 so that air can be supplied to the water to be treated in the nitrification unit. Then, in the nitrification reaction tank 34, ammonium ions in the water to be treated are nitrified into nitric acid and nitrous acid by the action of the nitrifying bacteria of the microorganism-supporting carrier. The nitrifying bacteria include ammonia-oxidizing bacteria, which are autotrophic bacteria that nitrify ammonium ions contained in the water to be treated into nitrite, and nitrite-oxidizing bacteria, which are autotrophic bacteria that nitrify ammonium ions into nitric acid.

When nitrified to nitric acid, the pH decreases. Therefore, a pH sensor is installed in the nitrification reaction tank 34, and alkali is added by a pump based on the pH data measured by the pH sensor so that the pH of the bacteria is high 6-8. Examples of the alkali used include sodium hydroxide and potassium hydroxide, but are not particularly limited. At this time, when the processing speed of the nitrification reaction tank 34 is operated at 0.6 kg / m ³ / d or more, a line for supplying inorganic carbon to the nitrification reaction tank 34 is installed to supply inorganic carbon. Examples of the inorganic carbon to be supplied include sodium hydrogen carbonate, sodium carbonate, carbon dioxide and the like, but are not particularly limited. When phosphorus is not contained in the incoming raw water, phosphorus is added in the nitrification reaction tank 34 or the raw water tank so that about 1 mg P / L of phosphorus remains in the final treated water. Examples of phosphorus to be added include phosphoric acid and other phosphates, but there is no particular limitation.

  The first treated water treated in the nitrification reaction tank 34 is supplied to the denitrification reaction tank 10 from the treated water inflow line 22b. Further, the detected water flow rate and nitric acid and nitrous acid concentration data are transmitted to the control unit 32 by the flow rate sensor 28 and the TN sensor 30. As described above, the amounts of nitric acid and nitrous acid are calculated at predetermined time intervals based on the data. Then, according to the increase or decrease in the amount of nitric acid / nitrous acid, various parameters are set as described above, and intermittent addition of the hydrogen donor is controlled.

  When nitric acid is reduced by the denitrification reaction, the pH rises. Therefore, based on the pH data measured by the pH sensor installed in the denitrification reaction tank 10, an acid is added by a pump so that the pH of the bacteria is high 6-8. Examples of the acid used include hydrochloric acid and sulfuric acid, but are not particularly limited. In the case where the denitrification reaction tank 10 is divided, the hydrogen donor may be added only to the frontmost tank or may be divided and added to all the tanks. The pH sensor and its control may be installed only in the largest tank or in all tanks.

  The second treated water treated in the denitrification reaction tank 10 is supplied to the oxidation tank 12 through the treated water inflow line 22c, and the hydrogen donor in the treated water is oxidized.

  The third treated water treated in the oxidation tank 12 passes through the treated water inflow line 22d and is supplied to the precipitation treatment tank 14. In the sedimentation treatment tank 14, sludge in the water to be treated is separated, and (final) treated water is obtained from the treated water discharge line 24, and the separated sludge is supplied to the nitrification reaction tank 34 through the sludge return line 26. The By returning the sludge to the nitrification reaction tank 34 in this way, sludge containing nitrifying bacteria is formed, so that the nitrification reaction and denitrification reaction can be treated with the same sludge.

In the oxidation tank 12, it is not necessary to control the pH, but the pH rises when inorganic carbon is discharged as CO ₂ by aeration. If the pH of the treated water does not satisfy the drainage standard or the environmental standard, a pH sensor is installed in the oxidation tank 12 and an acid is added so that the treated water becomes a reference value based on the measured pH data. Adjust by. Alternatively, when pH control is performed in the oxidation tank 12, the amount of inorganic carbon contained in the return flow rate is reduced, and shortage of inorganic carbon easily occurs in the nitrification reaction tank 34. Therefore, a pH sensor is installed in the treated water tank for control. Examples of the acid used include hydrochloric acid and sulfuric acid, but are not particularly limited.

  FIG. 3 is a schematic diagram illustrating another example of the biological treatment apparatus for nitrogen-containing water according to the present embodiment. The biological treatment apparatus 3 for nitrogen-containing water shown in FIG. 3 has the same configuration as the biological treatment apparatus 2 for nitrogen-containing water shown in FIG. 2 except that the denitrification reaction tank is divided into a plurality of parts. The denitrification reaction tank shown in FIG. 3 includes a first denitrification reaction tank 10a and a second denitrification reaction tank 10b.

  A treated water inflow line 22 a is connected to a treated water inlet (not shown) of the nitrification reaction tank 34. A treated water inflow line 22b is connected between the treated water outlet (not shown) of the nitrification reaction tank 34 and the treated water inlet (not shown) of the first denitrification reaction tank 10a. A hydrogen donor addition line 20 is connected via a pump 16 between the hydrogen donor inlet (not shown) of the first denitrification reaction tank 10 a and the outlet (not shown) of the tank 18. A treated water inflow line 22c is connected between the outlet (not shown) of the first denitrification reaction tank 10a and the inlet (not shown) of the second denitrification reaction tank 10b, and the second denitrification reaction tank 10b. A treated water inflow line 22d is connected between the outlet (not shown) and the inlet (not shown) of the oxidation tank 12, and the outlet (not shown) of the oxidation tank 12 and the inlet of the precipitation tank 14 (not shown) The untreated water inflow line 22e is connected to the unillustrated). A treated water discharge line 24 is connected to a treated water outlet (not shown) of the precipitation treatment tank 14. A sludge return line 26 is connected between the sludge outlet (not shown) of the settling tank 14 and the treated water inflow line 22a.

  Below, operation | movement of the biological treatment apparatus 3 of the nitrogen-containing water of this embodiment is demonstrated.

  The treated water is supplied to the nitrification reaction tank 34 from the treated water inflow line 22a. In the nitrification reaction tank 34, organic nitrogen, ammonia and the like in the water to be treated are mainly oxidized aerobically (in the presence of oxygen) to nitric acid or nitrous acid.

  The first treated water treated in the nitrification reaction tank 34 is supplied from the treated water inflow line 22b to the first denitrification reaction tank 10a. Further, the detected water flow rate and nitric acid and nitrous acid concentration data are transmitted to the control unit 32 by the flow rate sensor 28 and the TN sensor 30. As described above, the amounts of nitric acid and nitrous acid are calculated at predetermined time intervals based on the data. Then, according to the increase or decrease in the amount of nitric acid / nitrous acid, various parameters are set as described above, and intermittent addition of the hydrogen donor is controlled.

  Sludge containing denitrifying bacteria is accommodated in the first denitrifying reaction tank 10a. After the treated water is brought into contact with the denitrifying bacteria in the first denitrifying reaction tank 10a, the treated water, denitrifying bacteria, hydrogen The donor is fed from the treated water inflow line 22c to the second denitrification reaction tank 10b. And in the 2nd denitrification reaction tank 10b (and 1st denitrification reaction tank 10a), nitric acid or nitrous acid in to-be-treated water is reduced to nitrogen gas by the action of denitrifying bacteria.

  As described above, by dividing the denitrification reaction tank, for example, a temporal concentration gradient of the hydrogen donor is formed between the first denitrification reaction tank 10a and the second denitrification reaction tank 10b. It becomes easy, and the sedimentation property of the sludge in the subsequent sedimentation treatment can be improved.

  The second treated water treated in the first and second denitrification reaction tanks (10a, 10b) is supplied to the oxidation tank 12 through the treated water inflow line 22d, and the hydrogen donor in the treated water is oxidized. Is done.

  The third treated water treated in the oxidation tank 12 passes through the treated water inflow line 22e and is supplied to the precipitation treatment tank 14. In the sedimentation treatment tank 14, sludge in the water to be treated is separated, and (final) treated water is obtained from the treated water discharge line 24, and the separated sludge is supplied to the nitrification reaction tank 34 through the sludge return line 26. The By returning the sludge to the nitrification reaction tank 34 in this way, sludge containing nitrifying bacteria is formed, so that the nitrification reaction and denitrification reaction can be treated with the same sludge.

  Examples of the hydrogen donor used in the present embodiment include methanol, ethanol, isopropanol, acetic acid, hydrogen gas, acetone, glucose, ethyl methyl ketone, tetramethyl ammonium hydroxide (TMAH), and the like, but are not limited thereto. However, any conventionally known hydrogen donor can be used.

  The wastewater to be treated in this embodiment is treated water containing ammonia nitrogen compounds or organic nitrogen compounds, especially industrial wastewater such as domestic wastewater, food factory wastewater, power plant wastewater, and electronic industrial wastewater. . Here, the electronic industrial wastewater contains various chemicals, and the components in the wastewater vary greatly depending on the product to be manufactured, but examples of the nitrogen-containing wastewater include wafer cleaning wastewater. This waste water often contains TMAH (tetramethylammonium hydroxide), hydrogen peroxide, fluorine ions, IPA (isopropyl alcohol) and the like in addition to ammonia.

  In biological treatment of such wastewater, since hydrogen peroxide and fluorine ions have an inhibitory effect on living organisms, it is preferable to remove them in advance before performing a nitrification reaction or a denitrification reaction. . As a method for treating these inhibitory substances, existing techniques can be used, and in the treatment of hydrogen peroxide, a method of adding an enzyme, a method of injecting a reducing agent, a method of contacting with activated carbon and the like can be mentioned. It is done. Further, in the treatment of fluoride ions, a method of adding calcium and removing it as calcium fluoride, a method of treating with ion exchange resin, and the like can be mentioned.

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

<Example 1>
The test was conducted using a biological treatment apparatus for nitrogen-containing water equipped with a 50 L capacity denitrification reactor and a 8 L capacity sedimentation tank.

The denitrification sludge was added to the denitrification reaction tank so that the sludge concentration was 500 mg / L, and the water to be treated was continuously passed through. The sludge was returned to the denitrification reactor using an air lift at a flow rate twice that of the water to be treated. The water to be treated was prepared by adding sodium nitrate at 100 mg NO ₃ -N / L to industrial water with phosphorus added at 2 mg P / L. Hydrochloric acid was added to the denitrification reaction tank, and the pH in the denitrification reaction tank was adjusted to 7.0 to carry out the denitrification reaction. The concentration of hydrogen donor to be added to the denitrification reactor (M) 100 mL / L (79 g / L) of methanol was used, and the amount of hydrogen donor added was three times the amount of inflowing nitrate nitrogen (NO ₃ -N) The number of hydrogen donor intermittent addition cycles was set to 5 and the ratio of the hydrogen donor addition time to the time per cycle of intermittent addition was set to 5%. From the amount of treated water flowing in, the hydraulic residence time and the hydrogen donor supply stop time in the time per cycle of intermittent addition were set. These were applied to the above equation (1) to determine the hydrogen donor addition rate.

In Example 1, after confirming that the nitric acid concentration in the treated water was 10 mg NO ₃ −N / L or less, the amount of treated water was increased stepwise, and each parameter was set according to the control method 2 described above. . The test was conducted for 26 days.

<Comparative example>
In the comparative example, the hydrogen donor supply stop time in the time per cycle of intermittent addition was zero, that is, a continuous addition system in which no hydrogen donor supply stop time was provided was tested. Methanol was continuously added so as to be three times the amount of inflowing nitrate nitrogen (NO ₃ —N). The test was conducted for 26 days.

In the comparative example, on the 26th day from the start of the test, the MLSS concentration reached only about 3000 mgMLSS / L, and the treatment speed of the denitrification treatment was about 0.6 kgN / m ³ / day. FIG. 4 is a diagram showing a change in MLSS concentration with respect to the number of days elapsed in the test of Example 1. FIG. 5 is a diagram illustrating a change in the processing speed of the denitrification process with respect to the elapsed test days of Example 1. As shown in FIG. 4, in Example 1, the MLSS concentration increased with the passage of days, and the MLSS concentration reached 8000 mg MLSS / L on the 26th day from the start of the test. Further, as shown in FIG. 5, with the increase of the MLSS concentration, the processing speed of the denitrification process increases, and reaches about 2 kgN / m ³ / day on the 26th day from the start of the test, and a high processing speed is obtained. It was confirmed. In Example 1, granulation of sludge containing denitrifying bacteria was confirmed after about 2 weeks from the start of the test, and almost all sludge containing denitrifying bacteria was granulated after about 3 weeks. did. By controlling the intermittent addition of methanol according to the above formula (1) as in Example 1, the sedimentation property of the sludge was improved, and a sludge having a high treatment capacity could be created.

<Example 2>
The test was carried out using a biological treatment apparatus for nitrogen-containing water comprising a 10 L first denitrification tank, a 90 L second denitrification reaction tank, a 20 L oxidation tank, and a 8 L precipitation tank.

Denitrification sludge was added to the denitrification reaction tank so that the sludge concentration was 3000 mg / L, and continuous water treatment was performed on the water to be treated. The sludge was returned to the first denitrification reaction tank using an air lift at a flow rate of 0.5 times the flow rate of the water to be treated. The water to be treated was prepared by adding sodium nitrate to 80 mg NO ₃ —N / L to industrial water to which phosphorus was added to 2 mg P / L. Hydrochloric acid was added to the denitrification reaction tank, and the pH in the denitrification reaction tank was adjusted to 7.0 to carry out the denitrification reaction. As other conditions, the inflow nitrogen load is 0.6 kg / m ³ / d, methanol having a concentration of 100 mL / L is used as the hydrogen donor to be supplied to the first denitrification reaction tank, and the added amount of the hydrogen donor flows. The amount of nitrate nitrogen (NO ₃ —N) was 2.8 times, the number of hydrogen donor intermittent addition cycles was set to four, and the hydrogen donor addition time per cycle of intermittent addition was set to 5%.

FIG. 6A is a diagram showing changes in the concentrations of methanol and nitrate ions in the first denitrification reaction tank, and FIG. 6B is a diagram showing changes in the concentrations of methanol and nitrate ions in the second denitrification reaction tank. FIG. As shown in FIG. 6 (A), the maximum methanol concentration in the first denitrification reaction tank was 600 mg / L. This almost coincided with the calculated value (80 (mgNO ₃ −N / L) × 2.8 (times) × 10 (times) × 4 (times) = 560 mg / L). In addition, as shown in FIG. 6B, it can be seen that the nitrate ion concentration is increasing while the methanol concentration in the second denitrification reaction tank is zero (denitrification reaction is stopped). Therefore, in order to shorten the time when the methanol concentration is zero and to ensure stable treated water quality, it is important to set the hydrogen donor supply stop time (S _T ) as short as possible in the time per cycle of intermittent addition. It can be said that.

<Example 3>
The test was carried out using a biological treatment apparatus for nitrogen-containing water comprising a 10 L first denitrification tank, a 90 L second denitrification reaction tank, a 20 L oxidation tank, and a 8 L precipitation tank.

Denitrification sludge was added to the denitrification reaction tank so that the sludge concentration was 3000 mg / L, and continuous water treatment was performed on the water to be treated. The sludge was returned to the first denitrification reaction tank using an air lift at a flow rate of 0.5 times the flow rate of the water to be treated. The water to be treated, to which was added phosphorus so that 2mgP / L in industrial water and sodium nitrate 60MgNO ₃ from -N / L 20h until 80mgNO ₃ -N / L over, in proportion with time concentration Was raised. The initial load of inflowing nitrogen was 0.4 kg / m ³ / d. In order to adjust the pH in the denitrification reaction tank to 7.0 and perform the denitrification reaction, hydrochloric acid was added to the denitrification reaction tank. In Example 3, as the nitrogen concentration increased, the hydrogen donor addition time per cycle of intermittent addition was made constant, and the number of intermittent addition cycles was increased by reducing the supply stop time of the hydrogen donor. The amount of methanol added per hydraulic residence time was increased. The addition amount of the hydrogen donor was set to 2.6 times the amount of nitrate nitrogen (NO ₃ —N) flowing in.

  The initial hydrogen donor intermittent addition conditions of Example 3 were set such that the hydrogen donor addition time was set to 5% of the time per cycle of hydrogen donor intermittent addition, and the number of intermittent addition cycles was set to 3.5. Set. Further, the time per cycle of intermittent addition of the hydrogen donor was determined by (hydraulic residence time) / (number of intermittent addition cycles). The hydrogen donor addition time per cycle of intermittent addition is set to (time per cycle) × (5%), and the supply stop time of hydrogen donor per cycle of intermittent addition is (one cycle of intermittent addition) Per hour)-(hydrogen donor addition time per cycle of intermittent addition). Also, the hydrogen donor addition rate was determined from the hydrogen donor addition time, the number of intermittent hydrogen donor addition cycles, the amount of methanol required within the time per cycle of intermittent addition, and the methanol concentration.

<Example 4>
In Example 4, in accordance with the increase in the nitrogen concentration, the hydrogen donor addition time per cycle of intermittent addition was increased and the hydrogen donor supply stop time was decreased (however, the number of intermittent addition cycles was 3. The test was conducted under the same conditions as in Example 3 except that the amount of methanol added per hydraulic residence time was increased.

<Example 5>
In Example 5, the hydrogen donor addition rate was increased as the nitrogen concentration increased (however, the number of intermittent addition cycles was fixed at 3.5, and the hydrogen donor addition per cycle of intermittent addition was increased). The test was conducted under the same conditions as in Example 3 except that the amount of methanol added per hydraulic residence time was increased).

  The results of Examples 3-5 are summarized in Table 1. Moreover, FIG. 7 is a figure which shows the result of the nitrogen concentration in the treated water of Examples 3-5.

  As can be seen from Table 1 and FIG. 7, in Example 3 in which the hydrogen donor supply stop time per cycle of intermittent addition was decreased and the number of intermittent addition cycles was increased in accordance with the increase in nitrogen concentration, intermittent addition was performed. Example 4 in which the number of cycles was fixed, the hydrogen donor addition time per cycle of intermittent addition was increased, and the hydrogen donor supply stoppage time was decreased in accordance with the increase in nitrogen concentration. In Example 5 in which the speed was increased, the nitrogen concentration of the treated water was maintained at a low value even if the nitrogen concentration of the treated water was increased. In Examples 3 to 5, the most stable treated water quality can be ensured by decreasing the hydrogen donor supply stop time per cycle of intermittent addition in accordance with the increase in nitrogen concentration. In Example 3, the number of intermittent addition cycles was increased.

<Example 6>
The test was carried out using a biological treatment apparatus for nitrogen-containing water comprising a 10 L first denitrification tank, a 90 L second denitrification reaction tank, a 20 L oxidation tank, and a 8 L precipitation tank.

Denitrification sludge was added to the denitrification reaction tank so that the sludge concentration was 3000 mg / L, and continuous water treatment was performed on the water to be treated. The sludge was returned to the first denitrification reaction tank using an air lift at a flow rate of 0.5 times the flow rate of the water to be treated. The water to be treated was prepared by adding sodium nitrate so as to satisfy the conditions shown in Table 2 with respect to water added to industrial water so as to be 2 mg P / L. Hydrochloric acid was added to the denitrification reaction tank, and the pH in the denitrification reaction tank was adjusted to 7.0 to carry out the denitrification reaction. As other conditions, the inflow nitrogen load is 0.6 kg / m ³ / d, methanol having a concentration of 100 mL / L is used as the hydrogen donor to be supplied to the first denitrification reaction tank, and the added amount of the hydrogen donor flows. The amount was set to 2.6 times the amount of nitrate nitrogen (NO ₃ —N).

  Table 2 shows the hydraulic retention time, the number of intermittent addition cycles, the calculated TOC concentration gradient, and the treated water quality under each condition. The conditions for intermittent addition of the hydrogen donor were determined as follows. The time per cycle of intermittent hydrogen donor addition was determined by (hydraulic residence time) / (number of intermittent addition cycles). The hydrogen donor addition time per cycle of intermittent addition is set to (time per cycle) × (5%), and the supply stop time of hydrogen donor per cycle of intermittent addition is (one cycle of intermittent addition) Per hour)-(hydrogen donor addition time per cycle of intermittent addition). Also, the hydrogen donor addition rate was determined from the hydrogen donor addition time, the number of intermittent hydrogen donor addition cycles, the amount of methanol required within the time per cycle of intermittent addition, and the methanol concentration.

  The calculated TOC concentration gradient shown in Table 2 is (nitrogen concentration in the water to be treated) × (total capacity of the denitrification reaction tank / capacity of the first denitrification reaction tank) × (hydrogen donation with respect to the inflowing nitrogen concentration) It is calculated | required by multiplying the value calculated | required by the addition ratio of the body | division / (number of intermittent addition cycles of a hydrogen donor) by 0.375, and converting into TOC.

  FIG. 8 is a diagram showing the relationship between the number of intermittent hydrogen donor addition cycles and the quality of treated water. As can be seen from FIG. 8, the quality of the treated water was improved as the number of intermittent addition cycles of the hydrogen donor was increased. And in order to make nitrogen concentration in treated water 10 mgN / L or less, it turned out that the number of intermittent addition cycles of 2.5 times or more is required. Moreover, even if the nitrogen concentration of to-be-processed water increased, it turned out that the stable treated water quality is obtained by setting the number of intermittent addition cycles more than 2.5 times. Further, it was found that the intermittent addition cycle number needs to be set to 3.5 or more in order to bring the nitrogen concentration in the treated water close to zero. Thus, in order to ensure stable treated water quality, the number of intermittent addition cycles is preferably set to 2.5 times or more, and more preferably set to 3.5 times or more. In addition, it can be said that the higher the nitrogen concentration of the water to be treated, the more markedly deteriorated the quality of the treated water with the decrease in the number of intermittent addition cycles.

In the present invention, the hydrogen donor supply stop time (S _T ) is set so as to satisfy the formula (1), but when the hydrogen donor supply stop time is not provided (when S _T = 0), For example, when the hydraulic residence time (T) is 15 minutes and the amount of hydrogen donor required within this hydraulic residence time is 27 g, 5 g / min in 1 minute from the start of addition (0 minutes) 1 to 5 minutes at 1 g / min, 5 to 6 minutes at 5 g / min, 6 to 10 minutes at 1 g / min, 10 to 11 minutes at 5 g / min, 11 to 15 minutes at 1 g / min with 3 cycles of hydrogen It is also possible to add a donor. In this case, it is assumed that 1 g / min (minimum addition amount) of hydrogen donor 15 g is continuously added within this hydraulic residence time, and the remaining 12 g (27 g-15 g) is necessary in the present invention. What is necessary is just to set each parameter so that (1) Formula may be satisfy | filled as the addition amount X of a hydrogen donor.

In addition, when the hydrogen donor to be added per cycle is stored in a container and charged into the denitrification reaction tank all at once, the hydrogen donor addition rate (v) and the hydrogen donor addition time ratio (D) are set. Therefore, the hydrogen donor amount v ′ added per cycle can be determined by the following equation.
v ′ = X · T / (N · M)

  1-3 Biological treatment equipment of nitrogen-containing water, 10 Denitrification reaction tank, 10a First denitrification reaction tank, 10b Second denitrification reaction tank, 12 Oxidation tank, 14 Precipitation treatment tank, 16 Pump, 18 Tank, 20 Hydrogen Donor addition line, 22a-22e treated water inflow line, 24 treated water discharge line, 26 sludge return line, 28 flow rate sensor, 30 TN sensor, 32 control unit, 34 nitrification reaction tank.

Claims (16)

A biological treatment method for nitrogen-containing water in which a hydrogen donor is intermittently added to a reaction tank into which treated water containing nitric acid or nitrous acid flows, and the nitric acid or nitrous acid is reduced to nitrogen gas,
Depending on the increase or decrease in the amount of nitric acid or nitrous acid obtained from the product of the concentration of nitric acid or nitrous acid in the water to be treated flowing into the reaction tank and the amount of water to be treated flowing into the reaction tank, the following formula (1 ) So that the hydrogen donor addition rate (v), the hydrogen donor addition amount (X) required per unit time, the total volume of the reaction tank / the water flow rate flowing into the reaction tank Physical residence time (T), number of intermittent addition cycles of hydrogen donor (N) divided by time per cycle of intermittent addition consisting of addition and termination of hydrogen donor. Concentration of hydrogen donor (M), ratio of hydrogen donor addition time to time per cycle of intermittent addition (D), and hydrogen donor supply stop time ( _ST ) in time per cycle of intermittent addition Set Biological treatment method of the nitrogen-containing water, characterized in that.
v = X · T · (100−D) / (N · S _T · D · M) (1) The biological treatment method for nitrogen-containing water according to claim 1,
The nitric acid obtained from the product of the concentration of the nitric acid or nitrous acid in the water to be treated flowing into the reaction tank and the amount of water to be treated flowing into the reaction tank under a constant hydrogen donor addition rate (v) When the amount of nitrous acid is increased or decreased, the number of intermittent additions (N) and the ratio of hydrogen donor addition time (D) are increased or decreased in proportion to the increase or decrease of the nitric acid or the amount of nitrous acid, respectively. A biological treatment method for nitrogen-containing water, which is characterized by reducing the amount.   The biological treatment method for nitrogen-containing water according to claim 2, further comprising: the nitric acid or the nitrous acid in the treated water flowing into the reaction tank under a constant amount of treated water flowing into the reaction tank. As the concentration increases or decreases, the amount of nitric acid or nitrous acid obtained from the product of the concentration of nitric acid or nitrous acid in the water to be treated flowing into the reaction tank and the amount of water to be treated flowing into the reaction tank is When increased or decreased, the intermittent addition frequency (N) and the hydrogen donor addition time ratio (D) are increased or decreased in proportion to the increase or decrease in the amount of nitric acid or nitrous acid, respectively. A biological treatment method for nitrogen-containing water.   2. The biological treatment method for nitrogen-containing water according to claim 1, wherein the number of intermittent additions (N) and the ratio (D) of the hydrogen donor addition time are constant, and the treated water flows into the reaction tank. When the amount of nitric acid or nitrous acid obtained from the product of the concentration of nitric acid or nitrous acid and the amount of water to be treated flowing into the reaction vessel increases or decreases, the amount of nitric acid or nitrous acid increases or decreases. A biological treatment method for nitrogen-containing water, characterized by increasing or decreasing the hydrogen donor addition rate (v) in proportion.   The biological treatment method for nitrogen-containing water according to claim 4, further comprising a treatment to flow into the reaction tank under a constant concentration of the nitric acid or nitrous acid in the treated water flowing into the reaction tank. Due to the increase or decrease in the amount of water, the amount of nitric acid or nitrous acid determined from the product of the concentration of nitric acid or nitrous acid in the treated water flowing into the reaction tank and the amount of treated water flowing into the reaction tank is A biological treatment method for nitrogen-containing water, characterized by increasing or decreasing the hydrogen donor addition rate (v) in proportion to an increase or decrease in the amount of nitric acid or nitrous acid when increased or decreased.   2. The biological treatment method for nitrogen-containing water according to claim 1, wherein the hydrogen donor addition rate (v) and the intermittent addition frequency (N) are constant and the treatment water flowing into the reaction tank flows into the reaction tank. When the amount of nitric acid or nitrous acid obtained from the product of the concentration of nitric acid or nitrous acid and the amount of treated water flowing into the reaction vessel increases or decreases, it is proportional to the increase or decrease in the amount of nitric acid or nitrous acid. And increasing or decreasing the hydrogen donor addition time ratio (D).   The biological treatment method for nitrogen-containing water according to any one of claims 1 to 6, wherein the number of intermittent additions (N) is 2.5 or more. . The biological treatment method for nitrogen-containing water according to claim 2 or 3, wherein the intermittent addition frequency (N) is less than 2.5 as a result of reducing the intermittent addition frequency (N). The number of additions (N) is set to 2.5 or more, and the hydrogen donor supply stop time (S _T ) and the hydrogen donor addition rate (v) are reset so as to satisfy the formula (1). A biological treatment method for nitrogen-containing water. A reaction vessel into which treated water containing nitric acid or nitrous acid flows, and a hydrogen donor addition means for intermittently adding a hydrogen donor to the reaction vessel, wherein the nitric acid or nitrous acid is converted to nitrogen gas in the reaction vessel. A biological treatment apparatus for reducing nitrogen-containing water,
Depending on the increase or decrease in the amount of nitric acid or nitrous acid obtained from the product of the concentration of nitric acid or nitrous acid in the water to be treated flowing into the reaction tank and the amount of water to be treated flowing into the reaction tank, the following formula (1 ) So that the hydrogen donor addition rate (v), the hydrogen donor addition amount (X) required per unit time, the total volume of the reaction tank / the water flow rate flowing into the reaction tank Physical residence time (T), number of intermittent addition cycles of hydrogen donor (N) divided by time per cycle of intermittent addition consisting of addition and termination of hydrogen donor. Concentration of hydrogen donor (M), ratio of hydrogen donor addition time to time per cycle of intermittent addition (D), and hydrogen donor supply stop time ( _ST ) in time per cycle of intermittent addition Set Biological treatment apparatus of the nitrogen-containing water, characterized in that it comprises a control means.
v = X · T · (100−D) / (N · S _T · D · M) (1) The biological treatment apparatus for nitrogen-containing water according to claim 9,
The control means calculates the concentration of the nitric acid or the nitrous acid in the water to be treated flowing into the reaction tank and the amount of the water to be treated flowing into the reaction tank under a constant hydrogen donor addition rate (v). When the required amount of nitric acid or nitrous acid increases or decreases, the ratio of the intermittent addition number (N) and the hydrogen donor addition time (D) in proportion to the increase or decrease of the nitric acid or nitrous acid amount (D ), Or a biological treatment apparatus for nitrogen-containing water.   The biological treatment apparatus for nitrogen-containing water according to claim 10, wherein the control means further includes the nitric acid in the water to be treated flowing into the reaction tank under a constant amount of the water to be treated flowing into the reaction tank. Alternatively, as the concentration of nitrous acid is increased or decreased, the nitric acid obtained from the product of the concentration of nitric acid or nitrous acid in the water to be treated flowing into the reaction tank and the amount of water to be treated flowing into the reaction tank or When the amount of nitrous acid is increased or decreased, the number of intermittent additions (N) and the ratio of hydrogen donor addition time (D) are increased or decreased in proportion to the increase or decrease of the nitric acid or the amount of nitrous acid, respectively. A biological treatment apparatus for nitrogen-containing water, characterized in that it is reduced.   10. The biological treatment apparatus for nitrogen-containing water according to claim 9, wherein the control means is arranged in the reaction tank under a constant number of intermittent additions (N) and a ratio (D) of the hydrogen donor addition time. When the amount of nitric acid or nitrous acid obtained from the product of the concentration of nitric acid or nitrous acid in the treated water flowing in and the amount of treated water flowing into the reaction tank increases or decreases, the amount of nitric acid or nitrous acid A biological treatment apparatus for nitrogen-containing water, wherein the hydrogen donor addition rate (v) is increased or decreased in proportion to an increase or decrease in the amount of hydrogen.   13. The biological treatment apparatus for nitrogen-containing water according to claim 12, wherein the control means is further configured so that the concentration of the nitric acid or the nitrous acid in the water to be treated flowing into the reaction tank is constant. The amount of treated water flowing into the reaction tank increases or decreases, so that the concentration of the nitric acid or nitrous acid in the treated water flowing into the reaction tank and the amount of treated water flowing into the reaction tank are determined by the product of the nitric acid or When the amount of nitrous acid increases or decreases, the hydrogen donor addition rate (v) is increased or decreased in proportion to the increase or decrease of the nitric acid or the amount of nitrous acid. Biological treatment equipment.   10. The biological treatment apparatus for nitrogen-containing water according to claim 9, wherein the control means flows into the reaction tank with the hydrogen donor addition rate (v) and the number of intermittent additions (N) being constant. When the amount of nitric acid or nitrous acid obtained from the product of the concentration of nitric acid or nitrous acid in the water to be treated and the amount of water to be treated flowing into the reaction tank increases or decreases, the amount of nitric acid or nitrous acid increases Alternatively, the biological treatment apparatus for nitrogen-containing water, wherein the proportion (D) of the hydrogen donor addition time is increased or decreased in proportion to the decrease.   The biological treatment apparatus for nitrogen-containing water according to any one of claims 9 to 14, wherein the control means sets the number of intermittent additions (N) to 2.5 or more. Biological treatment equipment for contained water. The biological treatment apparatus for nitrogen-containing water according to claim 10 or 11, wherein the control means decreases the number of intermittent additions (N), so that the number of intermittent additions (N) is less than 2.5. In this case, the number of intermittent additions (N) is set to 2.5 or more, and the hydrogen donor supply stop time (S _T ) and the hydrogen donor addition rate (v) are reestablished so as to satisfy the formula (1). A biological treatment apparatus for nitrogen-containing water, characterized by being set.

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