JP2013081881A - Apparatus for treating ammonia nitrogen content wastewater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for treating ammonia nitrogen content wastewater capable of stably performing nitrification treatment (nitrification reaction of a nitrous acid type) to nitrite nitrogen at high load.SOLUTION: The apparatus 1 for treating ammonia nitrogen content wastewater includes a nitrification tank for oxidizing ammonia nitrogen in the ammonia nitrogen content wastewater to nitride nitrogen with ammonia oxidizing bacteria, a denitrification tank 14 for reducing the nitrite nitrogen into nitrogen, and a sludge returning line 18 for returning a biological sludge in a liquid treated with the nitrification tank or the denitrification tank 14 to the ammonia nitrogen content wastewater of the nitrification tank or before being introduced into the nitrification tank. The nitrification tank arranges a first nitrification tank 10 and a second nitrification tank 12 in series. At least the second nitrification tank 12 does not have a biological retention carrier. The volume of the second nitrification tank 12 is in a range of ≥1/50 to ≤1/3 of the whole volume of all the nitrification tanks.

Description

  The present invention relates to a treatment apparatus for waste water containing ammonia nitrogen.

  A nitrification denitrification method is generally performed as a method for treating ammonia nitrogen-containing wastewater. This nitrification denitrification method oxidizes ammonia nitrogen to nitrite nitrogen or nitrate nitrogen by microorganisms under aerobic conditions, and water treated in nitrification process to nitrogen (gas) under anaerobic conditions It consists of a denitrification step to reduce. In the nitrification step, a treatment using floating sludge (floating activated sludge method) and a biofilm method using a microorganism holding carrier are employed. In recent years, in order to suppress energy consumption such as aeration power, a method has been disclosed in which the oxidation of ammonia nitrogen is stopped only up to nitrite nitrogen in the nitrification step, and nitrate nitrogen is not generated.

  For example, Patent Document 1 discloses performing a nitrite-type nitrification reaction while maintaining the ammonia nitrogen load per nitrification tank and the ammonia nitrogen concentration in the nitrification tank within predetermined ranges.

  For example, Patent Document 2 discloses a method of performing a nitrite-type nitrification reaction by controlling the dissolved oxygen (DO) concentration. For example, Patent Document 3 discloses a method of performing a nitrite-type nitrification reaction by keeping the inorganic carbon concentration high. Further, for example, Patent Document 4 discloses a method of increasing the processing speed by maintaining nitrifying bacteria as a nitrifying granule at a high concentration in a nitrifying tank.

JP 2000-61494 A Japanese Patent Laid-Open No. 4-122498 International Publication No. 2004/74191 JP 2006-320723 A

  However, in the methods of Patent Document 1 and Patent Document 3, ammonia nitrogen remains at a high concentration in the treated water. Therefore, it is necessary to treat the remaining ammonia nitrogen by oxidizing it to nitrate nitrogen in a subsequent step. If it does so, the ammonia oxidation bacteria required for a process will be inhibited, the process activity per sludge may become low, and a high load process may be impossible.

  Further, in the method of Patent Document 2, it is possible to keep the concentration of remaining ammonia nitrogen low, but it is necessary to reduce the concentration of oxygen as a substrate, so that the treatment activity per sludge becomes low and the load is high. Processing may not be possible. Further, the method of Patent Document 4 requires a large amount of an organic substance as a hydrogen donor required for reducing nitric acid into nitrous acid and nitrogen gas in the denitrification step.

  Accordingly, an object of the present invention is to provide an ammonia nitrogen-containing wastewater treatment apparatus capable of performing nitrification to nitrite nitrogen (nitrite-type nitrification reaction) stably and at a high load. To do.

  The present invention comprises a nitrification means for oxidizing ammonia nitrogen in waste water containing ammonia nitrogen to nitrite nitrogen by ammonia oxidizing bacteria, a denitrification means for reducing the nitrite nitrogen to nitrogen, the nitrification means or the above A biological waste sludge in the liquid treated by the denitrification means, or the return means for returning the ammonia sludge containing wastewater before being introduced to the nitrification means, to the ammonia nitrogen containing wastewater treatment apparatus. The nitrification means includes a plurality of nitrification tanks arranged in series, and at least the last nitrification tank is not provided with a biological support, and the volume of the last nitrification tank is a total nitrification tank. It is the range of 1/50 or more and 1/3 or less of the total volume of the tank.

  The ammonia nitrogen-containing wastewater treatment apparatus further comprises control means for controlling the concentration of ammonia nitrogen in the nitrification tank, and the control means remains in the nitrification tank except for the last nitrification tank. It is preferable to control the ammonia nitrogen in the nitrification tank so that the ammonia nitrogen concentration is 3 mg-N / L or more.

  Further, in the ammonia nitrogen-containing wastewater treatment apparatus, the nitrification means has at least three nitrification tanks, and the nitrification tank excludes the last-stage nitrification tank and the last-stage nitrification tank. A bypass passage is provided for allowing at least a part of the liquid treated in the nitrification tank to flow into the last nitrification tank, and the concentration of ammonia nitrogen flowing into the last nitrification tank is 3 mg in the treatment liquid bypass path. It is preferable to include a flow rate adjusting unit that adjusts the flow rate of the liquid that passes through the processing liquid bypass path so as to be equal to or higher than −N / L.

  In the ammonia nitrogen-containing wastewater treatment apparatus, the nitrification tank is provided with a drainage path for allowing the drainage to flow into each nitrification tank other than the last stage nitrification tank. It is preferable to provide a flow rate adjusting means for adjusting the flow rate of the liquid passing through the drainage channel so that the concentration of ammonia nitrogen flowing into the nitrification tank of the stage becomes 3 mg-N / L or more.

  According to the present invention, nitrification to nitrite nitrogen can be performed stably and with a high load.

It is a schematic block diagram which shows an example of the waste water processing apparatus which concerns on this embodiment. It is a schematic block diagram which shows another example of the waste water processing apparatus which concerns on this embodiment. It is a schematic block diagram which shows another example of the waste water processing apparatus which concerns on this embodiment. It is a schematic block diagram which shows another example of the waste water processing apparatus which concerns on this embodiment. It is a schematic block diagram which shows another example of the waste water processing apparatus which concerns on this embodiment. It is a figure which shows a time-dependent change of the density | concentration of ammonia nitrogen of the 1st nitrification tank in Example 1, nitrite nitrogen, and nitrate nitrogen. It is a figure which shows a time-dependent change of the density | concentration of ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen in the treated water of the 2nd nitrification tank in Example 1. FIG. It is a figure which shows the relationship between the ammonia nitrogen of the 1st nitrification tank at the time of nitrite type nitrification in Example 1, and the nitrate nitrogen density | concentration in the treated water of a 2nd nitrification tank. It is a figure which shows the time-dependent change of the nitrification rate in Example 1. FIG. It is a schematic block diagram which shows the structure of the waste water treatment equipment used by the test of the comparative example 1. It is a figure which shows the time-dependent change of the density | concentration of the ammonia nitrogen of the treated water in the comparative example 1, nitrite nitrogen, and nitrate nitrogen. It is a figure which shows the time-dependent change of the nitrification rate in the comparative example 1. It is a schematic block diagram which shows the structure of the waste water treatment equipment used by the test of the comparative example 2. It is a figure which shows the time-dependent change of the density | concentration of the ammonia nitrogen of the treated water in the comparative example 2, nitrite nitrogen, and nitrate nitrogen.

  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 wastewater treatment apparatus according to the present embodiment. A waste water treatment apparatus 1 shown in FIG. 1 includes a first nitrification tank 10 and a second nitrification tank 12 as an example of a nitrification means, a denitrification tank 14 as an example of a decomposing means, and a solid-liquid separation tank 16 as an example of a return means. And the main part is comprised by the sludge return line 18, the oxidation tank 20, the pH adjuster tank 22, and the control part 24. FIG.

  As shown in FIG. 1, a drainage inflow line 26 is connected to the first nitrification tank 10, and a discharge line 28 is connected between the tanks. A sludge return line 18 is connected between the sludge discharge port (not shown) of the solid-liquid separation tank 16 and the drainage inflow line 26. The sludge return line 18 may be directly connected to the first nitrification tank 10. pH adjusting agent inflow lines 30 a and 30 b are connected between the pH adjusting agent tank 22 and the first nitrifying tank 10 and the second nitrifying tank 12. Pumps 32a and 32b are installed in the pH adjuster inflow lines 30a and 30b.

  The wastewater to be treated in this embodiment is wastewater containing ammonia nitrogen, and examples thereof include industrial wastewater such as domestic wastewater, food factory wastewater, power plant wastewater, and electronic industrial wastewater.

<Nitrification treatment>
Ammonia nitrogen-containing wastewater is supplied to the first nitrification tank 10 from the drainage inflow line 26, and the first nitrogenation tank 10 and the second nitrification tank 12 remove the ammonia nitrogen in the wastewater under the aerobic condition. A nitrification reaction that oxidizes to nitrite nitrogen is performed. Specifically, as will be described later, the volume of the second nitrification tank 12 is defined in a range from 1/50 to 1/3 of the total volume of the first nitrification tank 10 and the second nitrification tank 12. In the first nitrification tank 10, most of the ammonia nitrogen in the waste water is oxidized to nitrite nitrogen, and in the second nitrification tank 12, the ammonia nitrogen remaining in the water treated in the first nitrification tank 10 is sublimated. While being oxidized to nitrate nitrogen, nitrification from ammonia nitrogen to nitrate nitrogen can be suppressed. Hereinafter, each nitrification tank will be specifically described.

  An aeration apparatus 33 is provided in the first nitrification tank 10. In the first nitrification tank 10, the nitrite nitrogen-containing wastewater flowing from the wastewater inflow line 26 is aerated by the aeration device 33, and the ammonia nitrogen in the wastewater is aerobic under the action of ammonia oxidizing bacteria in the tank. It is oxidized to nitrite nitrogen (nitrification reaction).

  Here, in the first nitrification tank 10, the concentration of ammonia nitrogen remaining in the first nitrification tank 10 is controlled in order to suppress nitrification (oxidation) from ammonia nitrogen to nitrate nitrogen in the waste water. Is preferred. In general, in a nitrification reaction tank in which a nitrite accumulation type nitrification reaction occurs, Nitrosomonas bacteria tend to prevail over Nitrosospira bacteria that generally prevail in ammonia oxidizing bacteria. Therefore, Nitrosomonas bacteria may have a defect in the symbiotic relationship with nitrite-oxidizing bacteria. Therefore, it is preferable to prioritize bacteria belonging to the genus Nitrosomonas. That is, it is preferable to control the ammonia nitrogen concentration in the first nitrification tank 10 so as to remain high enough to give priority to Nitrosomonas bacteria.

  An example of a method for controlling the concentration of ammonia nitrogen remaining in the first nitrification tank 10 will be described. For example, first, the ammonia concentration of the water treated in the first nitrification tank 10 is measured by the ammonia meter 34 installed in the first nitrification tank 10. And the control part 24 controls the opening / closing amount of valve | bulb V1 etc. of the aeration apparatus 33 with which the 1st nitrification tank 10 was equipped based on this measurement result, and adjusts aeration air volume. Thereby, the ammonia nitrogen concentration remaining in the first nitrification tank 10 can be controlled. The concentration of ammonia nitrogen in the first nitrification tank 10 is preferably 3 mg-N / L or more, and more preferably 10 to 70 mg-N / L in that the ammonia-oxidizing bacteria belonging to the genus Nitromononas have priority in the tank. When the ammonia nitrogen concentration in the first nitrification tank 10 is less than 3 mg-N / L, the Nitrosospira genus ammonia-oxidizing bacterium may have priority over the Nitrosomonas genus ammonia-oxidizing bacterium. Further, when the ammonia nitrogen concentration in the first nitrification tank 10 exceeds 70 mg-N / L, the nitrification activity may be lowered due to free ammonia inhibition and the nitrification rate may be lowered.

  Further, when the concentration of ammonia nitrogen in the raw water varies, it is desirable to adjust the sludge concentration in the first nitrification tank 10 so that the ammonia nitrogen remains in the first nitrification tank 10. For example, the control unit 24 controls the discharge time and timing of sludge settled in the solid-liquid separation tank 16 installed at the subsequent stage of the nitrification tank, and adjusts the amount of sludge returned to the first nitrification tank 10. Thus, ammonia nitrogen can be left in the first nitrification tank 10.

  The first nitrification tank 10 is not particularly limited as long as it is a biological treatment method capable of oxidizing ammonia nitrogen to nitrite nitrogen. For example, the floating activated sludge method or activated sludge is self-granulated. Or a combination of the floating activated sludge method or the granular sludge method with a fixed bed, a fluidized bed, a biological support carrier addition method, or the like. In the method for adding a biological support, a biological support on which ammonia-oxidizing bacteria are supported is placed in a tank. The biological carrier is not particularly limited, and for example, a sponge, gel, plastic molded product, or the like can be used. Specifically, it is preferable to use hydrophilic polyurethane sponge, polyvinyl alcohol gel, or the like.

  Usually, in the 1st nitrification tank 10, since ammonia nitrogen is nitrified and nitrite nitrogen is produced | generated, pH falls. When the pH decreases, the concentration of free nitrite nitrogen that is toxic to nitrifying bacteria such as ammonia-oxidizing bacteria increases, which may affect nitrifying activity. Therefore, the pH meter 36 installed in the first nitrification tank 10 measures the pH of the water treated in the first nitrification tank 10, and when the measured value falls below a predetermined value, the pump 32a is operated. Then, the alkaline agent filled in the pH adjuster tank 22 is supplied from the pH adjuster inflow line 30a to the first nitrification tank 10 to adjust the pH. The concentration of free nitrite nitrogen flowing out from the first nitrification tank 10 is preferably 0.04 mg / L or less. In order to make the concentration range, the pH is preferably adjusted to 6.8 to 8.0, preferably 7.3 to 8.0. Examples of the alkali agent to be used include sodium hydroxide and potassium hydroxide, but are not particularly limited.

  Moreover, it is preferable that the water temperature in the 1st nitrification tank 10 shall be 10-40 degreeC. If the water temperature exceeds 40 ° C, the nitrification reaction stops, and if it is less than 10 ° C, the nitrification activity may be inferior.

  Next, the water treated in the first nitrification tank 10 is supplied from the discharge line 28 to the second nitrification tank 12. In the second nitrification tank 12, the water treated in the first nitrification tank 10 is aerated by the aeration apparatus 37 provided in the tank, and the ammonia nitrogen remaining in the water treated in the first nitrification tank 10 is It is oxidized to nitrite nitrogen by ammonia oxidizing bacteria in the tank under aerobic conditions. Even if the water treated in the first nitrification tank 10 (water in which ammonia nitrogen remains) is supplied as it is to the denitrification tank 14 described later, the ammonia nitrogen is not sufficiently treated. This is because, for example, when heterotrophic denitrifying bacteria are used for the denitrification treatment in the denitrification tank 14, ammonia nitrogen cannot be treated with the heterotrophic denitrifying bacteria, and ANAMMOX (autotrophic denitrifying bacteria) is used for the denitrification treatment. This is because, when used, it is difficult to control the ratio of ammonia and nitrous acid.

  The second nitrification tank 12 is not particularly limited as long as it is a biological treatment method that can oxidize the ammonia nitrogen remaining in the first nitrification tank 10 to nitrite nitrogen. For example, the floating activated sludge method And granulated sludge method in which activated sludge is self-granulated. However, with regard to the method for adding a biological support, the Nitrosospira genus preferentially adheres and fixes to the biological support loaded in the second nitrification tank 12 and oxidizes ammonia nitrogen and nitrite nitrogen to nitrate nitrogen. . Therefore, in this embodiment, the biological support is not installed in the second nitrification tank 12. In addition, the case where it is not installed includes the case of filling with a water tank volume ratio of 1% or less.

  The volume of the second nitrification tank 12 is preferably 1/50 to 1/3 of the total volume of the first nitrification tank 10 and the second nitrification tank 12. If the volume of the second nitrification tank 12 is smaller than 1/50, for example, the nitrification volume load is too high, so that the ammonia nitrogen remaining in the water treated in the first nitrification tank 10 cannot be converted into nitrite nitrogen. In addition, if the volume of the second nitrification tank 12 is larger than 1/3, for example, HRT in a low ammonia concentration environment where Nitrosospira genus bacteria are likely to be preferred becomes long, and nitrite oxidizing bacteria are also preferred. The ammonia nitrogen remaining in the first nitrification tank 10 is oxidized to nitrate nitrogen.

  Since most of the ammonia nitrogen is introduced into the second nitrification tank 12 in a nitrified state, the pH is hardly lowered. For example, when the apparatus is started up or the nitrification activity is lowered. In this case, ammonia nitrogen flows into the second nitrification tank 12 at a high concentration, and the pH of the second nitrification tank 12 may be lowered due to oxidation of ammonia nitrogen. Therefore, the pH meter 38 installed in the second nitrification tank 12 measures the pH of the water treated in the second nitrification tank 12, and if the measured value falls below, for example, the predetermined value described above, the pump 32b is turned on. It is preferable that the alkaline agent filled in the pH adjuster tank 22 is operated and supplied to the second nitrification tank 12 from the pH adjuster inflow line 30b to adjust the pH.

  In the present embodiment, two nitrification tanks (first nitrification tank 10 and second nitrification tank 12) are provided, but three or more (a plurality) may be provided. In that case, the nitrification tank in the rearmost stage is configured to serve as the second nitrification tank 12 described in the present embodiment.

<Sludge return>
The liquid processed in the second nitrification tank 12 is supplied to the solid-liquid separation tank 16. In the solid-liquid separation tank 16, it is separated into water and biological sludge. Then, water is supplied to the denitrification tank 14, and the biological sludge is returned to the first nitrification tank 10 through the sludge return line 18. Thereby, the sludge in the 1st nitrification tank 10 and the 2nd nitrification tank 12 can be made into the same microflora. Further, as described above, the ammonia nitrogen concentration in the first nitrification tank 10 can be controlled by the amount of biological sludge to be returned. In this embodiment, although the solid-liquid separation tank 16 is installed, it is not always necessary to install it, and only the sludge return line 18 may be used. That is, a part of the biological sludge passing through the discharge line 28 between the second nitrification tank 12 and the denitrification tank 14 is returned from the sludge return line 18 to the first nitrification tank 10.

  In this embodiment, the biological sludge is returned to the first nitrification tank 10 via the sludge return line 18 and the drainage inflow line 26, but the sludge return line 18 is connected to the first nitrification tank 10 to May be returned directly from the sludge return line 18 to the first nitrification tank 10.

  2 to 3 are schematic configuration diagrams illustrating another example of the waste water treatment apparatus according to the present embodiment. In the waste water treatment apparatuses 2 and 3 shown in FIGS. 2 to 3, the same components as those in the waste water treatment apparatus 1 shown in FIG. The waste water treatment apparatus 2 shown in FIG. 2 replaces the solid-liquid separation tank 16 and the sludge return line 18 provided between the second nitrification tank 12 and the denitrification tank 14, and as an example of a return means, a denitrification tank 14 and an oxidation tank. 20 and a solid-liquid separation tank 40 and a sludge return line 42 installed at the rear stage of the oxidation tank 20. As shown in FIG. 2, the sludge return line 42 is connected between a sludge discharge port (not shown) of the solid-liquid separation tank 40 installed at the rear stage of the oxidation tank 20 and the drainage inflow line 26. The sludge return line 42 may be connected between the sludge discharge port of the solid-liquid separation tank 40 and the first nitrification tank 10. In such a wastewater treatment apparatus 2, the liquid treated in the denitrification tank 14 (and the oxidation tank 20) is separated into water and biological sludge by the solid-liquid separation tank 40, and the biological sludge is returned to the sludge return line 42 (and wastewater). It is returned to the first nitrification tank 10 from the inflow line 26). The waste water treatment apparatus 3 shown in FIG. 3 includes a first solid-liquid separation tank 16 and a first sludge return line 18 (first return means) provided between the second nitrification tank 12 and the denitrification tank 14, a denitrification tank 14, A second solid-liquid separation tank 40 and a second sludge return line 42 (second return means) are provided between the oxidation tank 20 or downstream of the oxidation tank 20. As shown in FIG. 3, the second sludge return line 42 is between the sludge discharge port (not shown) of the second solid-liquid separation tank 40 and the discharge line 28 between the first solid-liquid separation tank 16 and the denitrification tank 14. It is connected to the. In the second solid-liquid separation tank 40, the liquid treated in the denitrification tank 14 (and the oxidation tank 20) is separated into water and biological sludge, and the biological sludge is removed from the second sludge return line 42 and the discharge line 28. Will be returned to. As shown in FIGS. 2 and 3, when the oxidation tank 20 is installed, the solid-liquid separation tank 40 disposed in the subsequent stage of the denitrification tank 14 is preferably installed in the subsequent stage of the oxidation tank 20. .

<Denitrification treatment>
The water treated in the second nitrification tank 12 is treated in the denitrification tank 14 (via the solid-liquid separation tank 16). The denitrification tank 14 can employ, for example, a denitrification method that reduces nitrite nitrogen to nitrogen (gas) by heterotrophic denitrifying bacteria. In the denitrification treatment with heterotrophic denitrifying bacteria, it is necessary to add a hydrogen donor as a nutrient source for the heterotrophic denitrifying bacteria. As the hydrogen donor, methanol or a BOD component contained in waste water is used. In this embodiment, since most of the NOx in the water treated in the second nitrification tank 12 is nitrite nitrogen, the amount of hydrogen donor required for denitrification can be reduced.

  Further, the denitrification tank 14 reduces nitrite nitrogen to nitrogen (gas) by the action of ANAMOX bacteria that performs denitrification treatment using ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor, for example. A denitrification method or the like can be employed. One example will be described below.

  FIG. 4 is a schematic configuration diagram illustrating another example of the waste water treatment apparatus according to the present embodiment. In the waste water treatment apparatus 4 shown in FIG. 4, the same components as those in the waste water treatment apparatus 1 shown in FIG. The waste water treatment apparatus 4 shown in FIG. 4 employs a USB reaction tank (Upflow Sludge Bed) in which a granulated sludge bed of ANAMMOX bacteria is formed as the denitrification tank 14. In this case, the drainage inflow line 26 is branched and connected to the discharge line 28 between the denitrification tank 14 and the solid-liquid separation tank 16 so that the wastewater is supplied to the USB reaction tank (denitrification tank 14). Is preferred.

<Oxidation treatment>
As shown in FIGS. 1-3, the liquid discharged | emitted from the denitrification tank 14 is supplied to the oxidation tank 20 (aeration tank) installed in a back | latter stage. The liquid after the denitrification treatment is aerated by an aeration apparatus (not shown) provided in the oxidation tank 20, and the BOD component and the like remaining in the liquid are oxidized under aerobic conditions. In addition, when the BOD component is not contained excessively, the oxidation tank 20 is not necessarily installed.

  In addition, when SS components, hydrogen peroxide, fluorine ions, etc. are mixed in the waste water before being supplied to the waste water treatment apparatus (drainage treatment apparatuses 1 to 4) of this embodiment, hydrogen peroxide, fluorine ions, etc. Since it has an inhibitory effect on organisms, it is preferably removed in advance before the nitrification reaction or 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. In addition, SS components and the like can be treated by coagulation precipitation, and in the treatment of fluorine ions, there are a method of adding calcium and removing it as calcium fluoride, a method of treating with an ion exchange resin, and the like.

  Further, if fluorine ions are removed in advance using Ca or the like before performing the nitrification reaction and the denitrification reaction, Ca may be contained in the waste water to be treated in this embodiment. There is a possibility that inorganic carbon and calcium react to precipitate calcium carbonate. In that case, precipitation of calcium carbonate can be prevented by determining the pH of the denitrification reaction with reference to the Langeria index.

  FIG. 5 is a schematic configuration diagram illustrating another example of the waste water treatment apparatus according to the present embodiment. In the waste water treatment apparatus 5 of FIG. 5, the same components as those of the waste water treatment apparatus 1 of FIG. As shown in FIG. 5, the waste water treatment apparatus 5 includes three nitrification tanks, a first nitrification tank 10, a second nitrification tank 10 a, and a third nitrification tank 12. In addition, a bypass 46 is connected between the discharge line 28 between the first nitrification tank 10 and the second nitrification tank 10 a and the third nitrification tank 12. By such a bypass 46, the water treated in the first nitrification tank 10 flows into the third nitrification tank 12 through the bypass 46. That is, the water treated in each nitrification tank except for the third nitrification tank 12 which is the last nitrification tank flows into the third nitrification tank 12 which is the last nitrification tank. Further, in the present embodiment, the drainage inflow line 26 is branched, and a drainage passage 26a connected to the second nitrification tank 10a is provided, so that the wastewater is directly supplied to the second nitrification tank 10a. Yes.

  In the wastewater treatment apparatus 5 of the present embodiment, for example, when the concentration of ammonia nitrogen in the water discharged from the nitrification tank upstream of the last nitrification tank, that is, the second nitrification tank 10a fluctuates, it is provided in the bypass passage 46. The third nitrification tank, which is the last nitrification tank, is adjusted by adjusting the flow rate of the liquid passing through the bypass path 46 and the drainage path 26a by adjusting the opening / closing amount of the valve V3 provided in the drainage path 26a. It is preferable to maintain the ammonia nitrogen concentration flowing into 12 within a certain range. This makes it possible to reliably perform the nitritation treatment in the third nitrification tank 12, which is the last nitrification tank. Here, the concentration of ammonia nitrogen flowing into the third nitrification tank 12, which is the last nitrification tank, is preferably 3 mg-N / L or more, and more preferably 10 to 70 mg-N / L.

  The fluctuation of the ammonia nitrogen concentration in the water discharged from the second nitrification tank 10a can be detected by, for example, an ammonia meter 34 installed in the second nitrification tank 10a.

According to the waste water treatment apparatus according to the present embodiment as described above, the nitrification treatment to nitrite nitrogen can be performed stably and with a high load. In addition, the following effects can be considered.
(1) Since it is not necessary to limit DO etc. in the 1st nitrification tank, ammonia oxidation at high speed is attained.
(2) Unlike the conventional method, the second nitrification tank can perform a nitrite type nitrification reaction although it can be processed with almost no ammonia nitrogen remaining.
(3) In the conventional method, the ratio of ammonia, nitrous acid, and nitric acid after treatment was greatly influenced by the concentration of ammonia nitrogen in the inflow raw water and the load, but in this embodiment, the flora of ammonia-oxidizing bacteria having a slow growth rate However, it is difficult to be affected by short-term concentration and load fluctuations, and it is possible to maintain a stable nitrite type nitrification reaction.
(4) When the nitrification liquid obtained by the nitrification tank of this embodiment is introduced into the denitrification tank, the reduction treatment of nitric acid-nitrous acid can be shortcuted, so that the required hydrogen donor amount can be greatly reduced.
(5) In the treatment apparatus shown in FIG. 4, in order to introduce the ammonia nitrogen-containing wastewater into the denitrification tank together with the nitrification solution, a denitrification reaction is performed using ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor. Due to the action of denitrifying bacteria, denitrification can be performed without the need for a hydrogen donor such as organic matter. Further, in the case of using a denitrification reaction in which ammonia is used as a hydrogen donor and nitrous acid is used as an electron acceptor in the latter stage, most of the ammonia nitrogen is converted to nitrite nitrogen in the nitrification tank of this embodiment. The ratio of ammonia nitrogen and nitrite nitrogen can be adjusted more easily than in the conventional method by flowing ammonia nitrogen-containing wastewater into the denitrification tank together with the nitrification solution.

  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
Using the apparatus shown in FIG. 1, nitrite type nitrification and denitrification were performed. The properties of the waste water of Example 1 and the specifications and conditions of the apparatus used are as follows.

<Test conditions>
Drainage: Synthetic drainage first nitrification tank to which NH ₄ -N concentration is 350 mg / L by adding ammonium chloride: Dimensions 382 mmφ × 528 mm height, capacity 25 L (water surface height approximately 225 mm
), Treatment method is floating activated sludge method (granule method)
Second nitrification tank: dimensions 140 mm x 140 mm x 550 mm height, capacity 5.1 L (water surface height
About 320mm), treatment method is floating activated sludge method (granule method)
Water temperature in the first and second nitrification tanks: 20 ° C
DO concentration in the first and second nitrification tanks: 5 mg / L
Denitrification tank: Dimensions 382mmφ x 528mm height, capacity 22L (water surface height approximately 190mm),
Treatment method is heterotrophic denitrification treatment oxidation tank: Dimensions 200mm x 200mm x 250mm height, capacity 4.5L (water surface height approx. 11
3mm)

  In the test of Example 1, a load was applied to the nitrification tank such that the ammonia nitrogen concentration in the first nitrification tank was 10 mg-N / L. FIG. 6 is a graph showing changes over time in the concentrations of ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen in the first nitrification tank. FIG. 7 is a graph showing changes over time in the concentrations of ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen in the treated water (digested liquid) of the second nitrification tank. FIG. 8 shows the relationship between the ammonia nitrogen in the first nitrification tank and the nitrate nitrogen concentration in the treated water (in the nitrification solution) of the second nitrification tank during nitrite type nitrification. FIG. 9 is a graph showing the change with time in the nitrification rate in Example 1. FIG.

(Comparative Example 1)
FIG. 10 is a schematic configuration diagram showing the configuration of the waste water treatment apparatus used in the test of Comparative Example 1. The configuration of the waste water treatment device 6 shown in FIG. 10 is the same as the configuration of the waste water treatment device 1 shown in FIG. 1 except that the nitrification tank is a single unit. The properties of the waste water of Comparative Example 1 and the specifications and conditions of the apparatus used are as follows.

Drainage: by the addition of ammonium chloride, synthetic wastewater nitrification tank was _NH 4 -N concentration 800 mg / L: Dimensions 382mmφ × 528mm height; capacity 38L (water surface height of about 340 mm)
Treatment method: Floating activated sludge method

In Comparative Example 1, using the nitrification granules shown in JP-A-2006-320723, acclimatization to a nitrification load of 1.3 kgN / m ³ / day was performed, and it was confirmed that the nitrogen in the treated water was almost converted to nitrate nitrogen Then, the time-dependent changes in the concentrations of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen of the treated water were measured. The result is shown in FIG. In addition, FIG. 12 shows the results of the change over time in the nitrification rate in Comparative Example 1.

(Comparative Example 2)
FIG. 13 is a schematic configuration diagram showing the configuration of the waste water treatment apparatus used in the test of Comparative Example 2. The waste water treatment apparatus 7 shown in FIG. 13 includes a first nitrification tank 50 and a second nitrification tank 52. In each of the first nitrification tank 50 and the second nitrification tank 52, a sponge carrier 54, which is a single organism holding organism, is placed in each water tank. It was filled so that it might become 20% by volume ratio. Except for this, nitrification was performed under the same conditions as in Example 1, and changes over time in the concentrations of ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen in the treated water (in the digestive fluid) were measured. The result is shown in FIG.

As is clear from FIG. 11, in Comparative Example 1 in which the nitrification tank was not divided, almost all nitrogen was converted to NO ₃ —N in the treated water. And as shown in FIG. 12, the nitrification speed | rate in the comparative example 1 was the range of 0.5-1.5 kgN / m < ³ > / day. On the other hand, as apparent from FIGS. 6 and 7, in Example 1 in which the nitrification tank was divided, the amount of conversion to NO ₂ -N increased, and the NO ₃ -N concentration of the treated water was partially in a stable state. Of nitrogen was removed. In addition, there was almost no residual ammonia nitrogen in the nitrification solution. Further, as shown in FIG. 8, when the ammonia nitrogen in the first nitrification tank is less than 3 mg-N / L, the nitrate nitrogen concentration in the nitrification liquid greatly increases, so the ammonia nitrogen concentration in the first nitrification tank Was preferably adjusted to 3 mg-N / L or more. As shown in FIG. 9, the nitrification rate in Example 1 is in the range of 1 to 2.4 kgN / m ³ / day, which is higher than that in Comparative Example 1.

As apparent from FIG. 14, in Comparative Example 2 in which the nitrification tank was divided and filled with the sponge carrier, NO ₃ -N was given priority in the nitrification liquid despite the situation where ammonia nitrogen remained in the nitrification liquid. As a result. This is presumably because the ammonia oxidizing bacteria belonging to the genus Nitrosospira, which are preferential at a low concentration of ammonia nitrogen, remain in the water tank due to the presence of the carrier.

  1-7 Wastewater treatment equipment, 10, 50 First nitrification tank, 10a, 12, 52 Second nitrification tank or third nitrification tank, 14 Denitrification tank, 16, 40 Solid-liquid separation tank, 18, 42 Sludge return line, 20 Oxidation tank, 22 pH adjuster tank, 24 control unit, 26 drainage inflow line, 26a drainage channel, 28 discharge line, 30a, 30b pH adjuster inflow line, 32a, 32b pump, 33, 37 aeration device, 34 ammonia meter, 36,38 pH meter, 46 Bypass, 54 Sponge carrier.

Claims (4)

A nitrification means for oxidizing ammonia nitrogen in waste water containing ammonia nitrogen to nitrite nitrogen by ammonia oxidizing bacteria, a denitrification means for reducing the nitrite nitrogen to nitrogen, and the nitrification means or the denitrification means A treatment apparatus for ammonia nitrogen-containing wastewater having a biological sludge in the treated liquid, or the return means for returning to the ammonia nitrogen-containing wastewater before being introduced into the nitrification means or the nitrification means,
The nitrification means has a plurality of nitrification tanks arranged in series, and at least the last nitrification tank is not provided with a biological support, and the volume of the last nitrification tank is the total of all nitrification tanks. An ammonia nitrogen-containing wastewater treatment apparatus characterized by being in a range of 1/50 to 1/3 of the volume. A control means for controlling the concentration of ammonia nitrogen in the nitrification tank;
The control means controls the ammonia nitrogen in the nitrification tank so that the concentration of ammonia nitrogen remaining in the nitrification tank excluding the last nitrification tank is 3 mg-N / L or more. The apparatus for treating ammonia-nitrogen-containing wastewater according to claim 1. The nitrification means has at least three nitrification tanks,
The nitrification tank is provided with a bypass for allowing at least a part of the liquid treated in the nitrification tank excluding the last nitrification tank and the last nitrification tank to flow into the last nitrification tank,
The treatment liquid bypass passage has a flow rate adjusting means for adjusting the flow rate of the liquid passing through the treatment liquid bypass passage so that the concentration of ammonia nitrogen flowing into the last-stage nitrification tank is 3 mg-N / L or more. The apparatus for treating wastewater containing ammonia nitrogen according to claim 1 or 2, characterized in that it is provided. The nitrification tank is provided with a drainage channel for allowing the wastewater to flow into each nitrification tank other than the last nitrification tank,
The drainage channel is provided with a flow rate adjusting means for adjusting the flow rate of the liquid passing through the drainage channel so that the concentration of ammonia nitrogen flowing into the last-stage nitrification tank is 3 mg-N / L or more. The processing apparatus of the waste water containing ammonia nitrogen according to any one of claims 1 to 3.