JP2010063987A - Waste water treatment device and treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waste water treatment device and a method therefor which can perform a nitrite type nitrification stage and an anaerobic ammonium oxidation stage in a single treatment tank. <P>SOLUTION: The waste water treatment device 20 is provided with a treatment tank 3, to which nitrogen-containing waste water containing ammonia is fed through a raw water line 2. The treatment tank 3 includes nitrification bacteria 4 and anaerobic ammonia oxidation bacteria 5, and the concentration of dissolved oxygen is controlled to 1.5 to 5.0 mg/L. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wastewater treatment apparatus and a treatment method, and more particularly, to a wastewater treatment apparatus and treatment method using anaerobic ammonia-oxidizing bacteria which are used for nitrogen removal of nitrogen-containing wastewater containing at least ammonia and which use ammonia and nitrous acid as substrates. .

  There is a need to remove nitrogen in wastewater that causes eutrophication in closed waters. This nitrogen is often contained in the form of ammoniacal nitrogen in sewage and various industrial wastewaters.

  As a method for removing ammonia nitrogen from wastewater, a method is generally known in which ammonia nitrogen is converted to nitrogen gas using nitrifying bacteria and denitrifying bacteria. Among them, recently, nitrogen removal by an anaerobic ammonia oxidation method has attracted attention.

  In this anaerobic ammonia oxidation method, anaerobic ammonia-oxidizing bacteria, which are autotrophic bacteria, use ammonia in nitrogen-containing water to be treated as an electron donor, nitrous acid as an electron acceptor, and ammonia and nitrous acid as follows. This is a method of simultaneous denitrification according to the formula (1) shown in Chemical formula 1.

(Chemical formula 1)
NH ₄ ⁺ +1.32 NO ₂ +0.066 HCO ₃ ⁻ + 0.13H ⁺
→ 1.02N ₂ + 0.26NO ₃ ⁻ + 0.066CH ₂ O _0.5 N _0.15 + 2.03H ₂ O
This has the advantage that the amount of methanol used can be significantly reduced compared to conventional nitrification / denitrification bacteria treatment, and the amount of sludge generated can be reduced. It is considered to be an effective method.

  This method requires that the ratio of ammonia and nitrous acid be close to the ratio of 1: 1.32. However, since it is mainly contained in the form of ammonia as the form of nitrogen in the wastewater, ammonia and nitrous acid are rarely contained in a ratio of 1: 1.32 as the form of nitrogen in the actual wastewater. Therefore, in order to construct a nitrogen removal system to which the anaerobic ammonia oxidation method is applied, a nitrite type nitrification step is required in which about half of the ammonia is converted into nitrous acid.

  In addition, it has been reported that anaerobic ammonia-oxidizing bacteria suffer from nitrite inhibition and lose their activity if nitrite-type nitrification produces excessive nitrite. Therefore, studies have been made to maintain nitrite-type nitrification and to maintain a constant nitrite concentration.

  In Patent Document 2, heat treatment is performed to maintain ammonia-oxidizing bacteria, and nitrite-oxidizing bacteria that nitrify (oxidize) nitrite to nitric acid are suppressed to maintain nitrite-type nitrification.

Further, in Patent Document 3, in order to keep ammonia and nitrous acid after nitrite type nitrification at around 1: 1.3, the nitrogen concentration is constantly monitored, the aeration air volume is controlled, and water is sent to the anaerobic ammonia oxidation process. ing.
Japanese Patent No. 2005-324133 Japanese Patent No. 2005-319430 JP 2005-246136 A

  As described above, in order to use the anaerobic ammonia oxidation method, it is necessary to provide a nitrite type nitrification step before the anaerobic ammonia oxidation step by the anaerobic ammonia oxidizing bacteria. In this nitrite type nitrification step, an oxidative reaction is caused using nitrifying bacteria, so it is necessary to aerate the air in the tank and make the dissolved oxygen concentration aerobic at 2 to 5 mg / L.

  On the other hand, in the latter anaerobic ammonia oxidation process, anaerobic ammonia oxidizing bacteria are anaerobic, and excessive dissolved oxygen reduces the activity of the anaerobic ammonia oxidizing bacteria. is there.

  Therefore, in the nitrogen removal method using the anaerobic ammonia oxidation method, the nitrite type nitrification step and the anaerobic ammonia oxidation step are performed in separate tanks. However, the nitrogen removal method using the anaerobic ammonia oxidation method is considered to be a space-saving and energy-saving effective method, and further space saving is desired.

  This invention was made in view of such a situation, and it aims at providing the waste-water-treatment apparatus and processing method which can perform a nitrite type nitrification process and an anaerobic ammonia oxidation process with a single processing tank. To do.

  In order to achieve the above object, the wastewater treatment apparatus of the present invention includes a treatment tank to which nitrogen-containing wastewater containing ammonia is fed via a raw water line, and the treatment tank has nitrifying bacteria and anaerobic ammonia oxidizing bacteria. And the dissolved oxygen concentration is controlled to 1.5 to 5.0 mg / L.

  According to the present invention, a nitrogen-containing wastewater containing at least ammonia is fed, and a single treatment tank containing nitrifying bacteria and anaerobic ammonia oxidizing bacteria is controlled at 1.5 to 5.0 mg / L. Ammonia contained in the nitrogen-containing wastewater can cause a nitrification reaction and a denitrification reaction simultaneously in a single treatment tank.

  In the wastewater treatment apparatus of the present invention, in the above invention, the treatment tank preferably includes a dissolved oxygen meter for measuring a dissolved oxygen concentration in the treatment tank, an air diffuser, and a nitrogen gas generator.

  The dissolved oxygen concentration in the treatment tank can be measured with a dissolved oxygen meter, the oxygen required for nitrifying bacteria can be supplied by an air diffuser, and the dissolved oxygen concentration required for nitrifying bacteria can be controlled. When dissolved oxygen is contained, nitrogen gas is diffused by the nitrogen gas generator, the dissolved oxygen concentration in the treatment tank can be reduced, and the inhibition of the activity of the anaerobic ammonia oxidizing bacteria can be avoided.

  In the wastewater treatment apparatus of the present invention, the first tank for starting up the nitrifying bacteria and the second tank for starting up the anaerobic ammonia-oxidizing bacteria are connected to the processing tank in the invention. It is preferred that

  In the first tank, the nitrifying bacteria contained in the processing tank can be kept in a state in which the nitrite type nitrification can sufficiently react, so that a nitrification activity corresponding to the dissolved oxygen concentration in the processing tank can be obtained. it can.

  Further, in the second tank, which is different from the first tank, the anaerobic ammonia oxidizing bacteria contained in the treatment tank can be kept in a state capable of sufficiently performing the anaerobic ammonia oxidizing reaction. The nitrous acid converted by this and the ammonia in the raw water can be immediately denitrified.

  The waste water treatment apparatus of the present invention is the waste water treatment apparatus according to the present invention, wherein the treatment tank is a nitrogen concentration meter for measuring the concentration of nitrogen in the treatment tank, and a circulation line for returning the treatment water of the treatment tank to the treatment tank. When the concentration of nitrite nitrogen in the treatment tank increases according to the measured value of each nitrogen concentration meter, the amount of air diffused in the air diffuser is decreased and the flow rate of the raw water line is increased. When the ammonia concentration in the treatment tank is increased, it is preferable that the amount of air diffused in the air diffuser is increased, the flow rate of the raw water line is decreased, and the amount of circulation in the circulation line is increased.

  According to this invention, the nitrogen concentration analyzer which can confirm the measured value of at least ammonia and nitrous acid is installed in the processing tank, and it is in the state which can always measure. When the concentration of nitrous acid in the treatment tank is temporarily increased, production of nitrous acid can be suppressed by lowering the amount of air diffused by the air diffuser and lowering the supply of oxygen used by nitrifying bacteria. At the same time, the control of increasing the flow rate of the raw water line is performed, and the denitrification reaction of anaerobic ammonia-oxidizing bacteria can be promoted by applying the ammonia nitrogen load to increase the excess nitrous acid concentration and the excess ammonia. Thereby, the concentration of nitrous acid in the tank can be shifted to a low concentration.

In addition, when the ammonia concentration in the treatment tank temporarily increases, the amount of nitrous acid produced can be increased by increasing the amount of air diffused by the air diffuser and increasing the supply of oxygen used by nitrifying bacteria. . At the same time, it can be returned from the treated water line of the treatment tank to the raw water tank via the circulation line. And by increasing the amount of circulation and simultaneously reducing the amount of raw water, the amount of excess ammonia discharged can be reduced,
The above control can maintain the activity of nitrifying bacteria and anaerobic ammonia-oxidizing bacteria in the treatment tank without being disturbed by the concentration of nitrogen in each state. Can be removed.

  In order to achieve the above object, the wastewater treatment method of the present invention comprises a nitrogen-containing wastewater containing ammonia via a raw water line, having nitrifying bacteria and anaerobic ammonia-oxidizing bacteria, and having a dissolved oxygen concentration of 1.5 to Water is fed to a treatment tank controlled to 5.0 mg / L, and nitrification / denitrification is performed in the treatment tank.

  According to the present invention, a nitrogen-containing wastewater containing at least ammonia is fed, and a single treatment tank having nitrifying bacteria and anaerobic ammonia oxidizing bacteria is controlled at 1.5 to 5.0 mg / L. Ammonia contained in the nitrogen-containing wastewater can cause a nitrification reaction and a denitrification reaction simultaneously in a single treatment tank.

  In the wastewater treatment method of the present invention, in the above invention, the treatment tank includes a dissolved oxygen meter for measuring the dissolved oxygen concentration of the treatment tank, an air diffuser, and a nitrogen gas generator, and the measured value of the dissolved oxygen meter. It is preferable to control the air diffuser and the nitrogen gas generator according to the above.

  In the wastewater treatment method of the present invention, in the above invention, the nitrifying bacteria and the anaerobic ammonia oxidizing bacteria in the treatment tank are preferably added to the treatment tank after being started up in separate tanks. .

  The wastewater treatment method of the present invention is the waste water treatment method according to the present invention, wherein the treatment tank comprises a nitrogen concentration meter for measuring the concentration of nitrogen in the treatment tank, and a circulation line for returning the treatment water in the treatment tank to the treatment tank. When the concentration of nitrite nitrogen in the treatment tank increases according to the measured value of each nitrogen concentration meter, the amount of air diffused in the air diffuser is decreased and the flow rate of the raw water line is increased. When the ammonia concentration in the treatment tank is increased, it is preferable to control to increase the amount of air diffused in the air diffuser, decrease the flow rate of the raw water line, and increase the amount of circulation in the circulation line.

  According to the present invention, nitrogen-containing wastewater containing ammonia is fed into a treatment tank containing nitrifying bacteria and anaerobic ammonia oxidizing bacteria, and the dissolved oxygen concentration in the treatment tank is 1.5 to 5.0 mg / L. By controlling, nitrification and denitrification can be performed simultaneously in a single treatment tank.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. The present invention will be described with reference to the following preferred embodiments, but can be modified in many ways without departing from the scope of the present invention, and other embodiments than the present embodiment can be utilized. be able to. Accordingly, all modifications within the scope of the present invention are included in the claims. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to”.

  FIG. 1 is a conceptual diagram showing an example of the overall configuration of the wastewater treatment apparatus of the present invention. The wastewater treatment apparatus 20 includes a raw water tank 1, a treatment tank 3 connected to the raw water tank 1 by a raw water line 2 via a flow meter 12, a dissolved oxygen meter 7 provided in the treatment tank 3, and an air diffuser 8. , A nitrogen gas generator 9, a nitrogen concentration analyzer 10, a treated water line 6 provided in the treatment tank 3, and a circulation line 11 connecting the treated water line 6 and the raw water line 2.

  Further, the wastewater treatment apparatus 20 makes the nitrifying bacteria 4 in a state where the nitrite type nitrification can be sufficiently performed, and the anaerobic ammonia oxidizing bacteria 5 in a state where the anaerobic ammonia oxidation reaction can be sufficiently performed. A second tank 14. The first tank 13 is connected to the processing tank 3 by a first line 15. The second tank is connected to the processing tank 3 by a second line 16.

  Next, a method for treating nitrogen-containing wastewater containing ammonia using the wastewater treatment apparatus 20 of the present invention will be described with reference to FIG.

  In FIG. 1, raw water containing at least ammonia is fed from a raw water tank 1 to a single treatment tank 3 containing nitrifying bacteria 4 and anaerobic ammonia oxidizing bacteria 5 through a raw water line 2 by a raw water pump (not shown). The treatment tank 3 holds the nitrifying bacteria 4 raised in the first tank 13 and the anaerobic ammonia oxidizing bacteria 5 raised in the second tank.

  The treatment tank 3 is controlled so that the dissolved oxygen concentration in a microaerobic state is 1.5 to 5.0 mg / L. The nitrifying bacteria 4 in the treatment tank 3 cause a nitrification reaction by the slightly aerobic dissolved oxygen, and a part of the ammonia contained in the raw water is converted into a form of nitrous acid. Ammonia in raw water and nitrous acid converted by nitrifying bacteria 4 are used as substrates for conversion to nitrogen gas by the denitrification reaction of anaerobic ammonia oxidizing bacteria 5. The raw water is discharged out of the system via the treated water line 6 in a state where ammonia and nitrite nitrogen are removed. Accordingly, different nitrification and denitrification reactions can be simultaneously performed in the single treatment tank 3 for ammonia contained in the raw water.

The concentration of ammoniacal nitrogen in the raw water flowing into the treatment tank 3 is preferably 50 to 2000 mg / L, and particularly preferably 200 to 1000 mg / L. The volume load of nitrogen-containing wastewater is most preferably 0.1 to 10 kg-N / m ³ / day as the amount of nitrogen, and the HRT of the culture tank is preferably about 2 to 48 hours.

The start-up state of nitrifying bacteria 4 included in the processing vessel 3, 0.05~5kgN ^/ m 3 ^/ day is considered good as nitrous acid production rate. Moreover, 0.1-10 kg-N / m < ³ > / day is preferable also as a starting state of the anaerobic ammonia oxidizing bacterium 5. FIG.

  Raw water can be used for both the nitrifying bacteria 4 and the anaerobic ammonia oxidizing bacteria 5. Moreover, it can be started by the normal nitrite type nitrification start-up according to the activity and the start-up method of the anaerobic ammonia oxidizing bacteria. Furthermore, the raw water used for the start-up of the anaerobic ammonia-oxidizing bacteria may be nitrite-type nitrification water during or after the start-up.

  The nitrifying bacteria 4 and the anaerobic ammonia-oxidizing bacteria 5 contained in the treatment tank 3 are preferably immobilized on either a fixed bed or a fluidized bed cell-fixing material, particularly those that are difficult to be discharged out of the system. desirable.

The material of the carrier in the immobilization material is not particularly limited, but is a plastic carrier such as vinyl chloride, cellulose, polyester, polypropylene, etc., a comprehensive immobilization carrier with a gel of polyvinyl alcohol, alginic acid, polyethylene glycol, resin property, sponge property A carrier, acrylic fiber nonwoven fabric, activated carbon fiber, or the like can be used.
The shape is not particularly limited, but it is possible to use a spherical body, a cylindrical state, a porous body, a cube, a rectangular parallelepiped, a sponge-like body, a fiber shape, a shape shaped like a chrysanthemum, a honeycomb-like body, or the like. preferable. In the case of a fluidized bed, the diameter needs to be such that the line is not blocked, and is preferably about 1 to 10 mm.

  For anaerobic ammonia oxidizing bacteria, self-granulated granules can be used. Their filling rate is preferably 20 to 50% by volume.

  Since the nitrifying bacteria 4 are aerobic bacteria, dissolved oxygen must be retained in the treatment tank 3 in order to cause a nitrifying reaction. On the other hand, since the anaerobic ammonia oxidizing bacteria 5 are anaerobic bacteria, there is a possibility that the anaerobic ammonia oxidizing bacteria 5 lose activity due to excessive oxygen.

  In order to maintain the activity of both the nitrifying bacteria 4 and the anaerobic ammonia oxidizing bacteria 5, it is necessary to control the dissolved oxygen concentration in the treatment tank 3.

  The treatment tank 3 is provided with a dissolved oxygen meter 7 for measuring the dissolved oxygen concentration in the treatment tank 3, an air diffuser 8, and a nitrogen gas generator 9. The dissolved oxygen meter 7 can constantly monitor the dissolved oxygen concentration. The dissolved oxygen concentration in the treatment tank 3 can be controlled by controlling the air diffuser 8 based on the value of the oxygen concentration of the dissolved oxygen meter 7 to diffuse the air into the treatment tank 3. The dissolved oxygen concentration in the treatment tank 3 is preferably in the range of 1.5 mg / L to 5.0 mg / L, and most preferably around 3 mg / L.

  If the dissolved oxygen concentration temporarily increases excessively, the air diffuser 8 is stopped. The nitrogen gas generator 9 is started by control, and nitrogen gas is diffused from the lower part in the processing tank 3. Thereby, a dissolved oxygen concentration can be reduced. When the dissolved oxygen concentration can return to the set value for a certain time, the control is switched to the air diffuser 8 and the steady operation is started.

  Oxygen necessary for the nitrifying bacteria 4 is supplied by the air diffuser 8 and a dissolved oxygen meter 7 is provided to keep the dissolved oxygen concentration constant, and the dissolved oxygen concentration in the treatment tank 3 is controlled by a combination of both. Thereby, it becomes possible to give the required dissolved oxygen amount according to the activity of the nitrifying bacteria 4, and it becomes possible to reduce the inhibition of the activity of the anaerobic ammonia oxidizing bacteria 5 due to the excessive dissolved oxygen. Moreover, when dissolved oxygen exceeding the set value is included, the nitrogen gas is diffused by the nitrogen gas generator 9 to reduce the dissolved oxygen concentration and to prevent the activity inhibition of the anaerobic ammonia-oxidizing bacteria 5. Become.

  In the wastewater treatment apparatus 20, it is preferable that the nitrifying bacteria 4 contained in the treatment tank 3 be in a state where the nitrite type nitrification can be sufficiently reacted in the first tank 13. This makes it possible to obtain nitrification activity that can cope with dissolved oxygen control.

  It is preferable to keep the anaerobic ammonia oxidizing bacteria 5 contained in the treatment tank 3 in a state where the anaerobic ammonia oxidation reaction can be sufficiently performed in a second tank different from the first tank 13. This makes it possible to immediately denitrify nitrous acid converted by the nitrifying bacteria 4 that have been started up and ammonia in the raw water.

  Furthermore, the anaerobic ammonia-oxidizing bacterium 5 that has been started up is likely to become anaerobic around the bacterium due to a large amount of nitrogen gas generated by itself, and a rapid reaction is possible. Even in a slightly aerobic state, a sufficient anaerobic ammonia oxidation reaction can be maintained. For this reason, it becomes possible to maintain the activity of the anaerobic ammonia-oxidizing bacteria 5 together with the nitrifying bacteria 4 in which the nitrification reaction proceeds.

  For this reason, it is possible to maintain the activity of the anaerobic ammonia-oxidizing bacteria 5 together with the nitrifying bacteria 4 in which the nitrification reaction proceeds, and it is possible to perform the nitrification / denitrification reaction in the single treatment tank 3.

  In the anaerobic ammonia oxidizing bacteria 5, the nitrogen removal rate varies greatly depending on the concentration ratio of ammonia and nitrous acid. In particular, if the concentration of nitrous acid in the treatment tank 3 is excessively increased, the activity of the anaerobic ammonia oxidizing bacteria 5 may be reduced. Therefore, it is necessary to control the nitrogen concentration ratio in the treatment tank 3.

  The treatment tank 3 is provided with a nitrogen concentration analyzer 10 that can measure at least the concentrations of ammonia and nitrous acid. The nitrogen concentration analyzer 10 constantly monitors the nitrogen concentration in the treatment tank 3.

  When the concentration of nitrous acid in the treatment tank 3 temporarily increases, the air diffuser 8 is controlled via the nitrogen concentration analyzer 10 to reduce the amount of diffused air. Thereby, the nitrifying bacteria 4 can delay the reaction of nitrifying ammonia in the raw water to nitrite by oxygen-limiting.

  At the same time, the flow rate of the raw water line 2 is increased from the set flow rate. Thereby, the residual nitrous acid is denitrified by the anaerobic ammonia oxidizing bacteria 5 together with the ammonia from the raw water line 2. Therefore, the nitrous acid concentration in the treatment tank 3 can be reduced.

  On the other hand, when the ammonia concentration in the processing tank 3 temporarily increases, the air diffuser 8 is controlled via the nitrogen concentration analyzer 10 to increase the amount of air diffused. Thereby, with the supply of oxygen, the nitrifying bacteria 4 increase the activity of converting ammonia into nitrous acid.

  Furthermore, when the ammonia concentration in the treatment tank 3 increases, the treated water can be returned from the treated water line 6 to the raw water line 2 via the circulation line 11 by a circulation pump (not shown).

  In this case, it is necessary to reduce the inflow of raw water. An amount that can be circulated is returned to the raw water line 2 from the ammonia concentration of the raw water and the treated water, and the flow rate of the raw water is set from the ammonia amount, and the control is performed so that the amount less than the necessary amount is introduced. As a result, the ammonia load can be kept constant or lowered at any time. The flow rate control is performed by the flow meter 12.

  Thereby, the nitrogen concentration in the treated water can be reduced by causing the ammonia contained in the treated water to flow again into the treatment tank 3 again. Moreover, the ammonia concentration in the processing tank 3 can be reduced. The activity of both cells contained in the treatment tank 3 can be maintained.

  The nitrous acid concentration is desirably 1.1 to 1.5 with respect to the ammonia concentration 1 in the raw water, and if the range is exceeded, the above control is preferably performed.

  By having the configuration as described above, nitrogen-containing wastewater containing ammonia is passed through a treatment tank containing nitrifying bacteria and anaerobic ammonia oxidizing bacteria, and the inside of the treatment tank is kept slightly aerobic. Thus, nitrification and denitrification can be performed simultaneously in a single treatment tank.

  Also, by providing a dissolved oxygen meter, an air diffuser and a nitrogen gas generator in the treatment tank, the dissolved oxygen concentration can be controlled to a constant set value within the range of 1.5 to 5.0 mg / L. Stable nitrification and denitrification can be performed in a single treatment tank without reducing the activity of nitrifying bacteria and anaerobic ammonia oxidizing bacteria.

  In addition, the nitrifying bacteria are processed in a separate tank, and the anaerobic ammonia-oxidizing bacteria are also started in a separate tank. Water can be passed through, and further, the decrease in activity due to the increase and decrease of the oxygen concentration can be minimized.

  The nitrogen concentration in the treatment tank is constantly measured, and when the nitrite nitrogen concentration in the treatment tank increases, the air diffuser is reduced and the flow rate of the raw water line is increased to reduce the load of ammonia. By giving an excess, it is possible to reduce a decrease in the activity of the bacterial cells in the tank, and it is possible to minimize the residual nitrogen concentration in the wastewater.

  The nitrogen concentration in the treatment tank is constantly measured, and if the ammonia concentration in the treatment tank increases, the amount of air diffuser in the air diffuser is increased and the flow rate of the raw water line is increased by providing a circulation line. The load can be controlled and the residual nitrogen concentration in the wastewater can be kept to a minimum.

  The present invention will be described more specifically with reference to the following examples. Conditions and the like shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention is not limited to the following specific examples.

  From the raw water tank in which the waste water containing ammonia was stored, water was continuously passed to the nitrification tank containing nitrifying bacteria with a raw water pump, and the nitrification reaction to nitrous acid was advanced at a water temperature of 30 ° C. and pH 7.5. The nitrifying bacteria added to the nitrification tank was conditioned at a water temperature of 30 ° C. and a pH of 7.5 under raw water DO = 4 mg / L, and a nitrification rate of about 55% was used in a steady state. The DO concentration in the nitrification tank was aerated with a blower and adjusted to each set DO. Table 1 shows the DO set in the nitrification tank, the respective ammonia loads, and the production rate of nitrous acid.

  A nitrification rate to nitrite of 60% or more is obtained even between DO = 1.5 and 4, and it can be confirmed that anaerobic ammonia oxidizing bacteria can contain a sufficient amount of nitrous acid for use.

  Wastewater containing about 1.3 times the amount of nitrous acid with respect to ammonia and ammonia is stored in the raw water tank 2 so that the nitrogen load is about 4.3 kgN / m 3 / d, and anaerobic ammonia oxidizing bacteria are stored in the raw water tank 2. Water was continuously passed through the denitrification tank contained by the raw water pump 2 to proceed an anaerobic ammonia oxidation reaction at a water temperature of 30 ° C. and a pH of 7.6. In the raw water tank, DO was adjusted to the set value by aeration with a blower. Anaerobic ammonia-oxidizing bacteria added to the denitrification tank are conditioned at a water temperature of 30 ° C. and a pH of 7.6 under raw water DO = 0 mg / L, and a nitrogen removal rate of 4.0 kg N / m 3 / d is in a steady state. used. Table 2 shows the DO concentration and ammonia removal rate of the raw water passed through the denitrification tank.

  Even when DO = 0 to 5.0 mg / L, the ammonia removal rate is 80% or more, particularly 95% until DO = 4.8 mg / L, and even when the DO concentration is high, the anaerobic condition has been adapted and finished. It was confirmed that sufficient activity was obtained in the ammonia-oxidizing bacteria.

  In nitrifying bacteria and anaerobic ammonia oxidizing bacteria, it is understood that activity is obtained in the range of DO = 1.5 to 5.0 mg / L, and nitrification and denitrification can be performed in the same tank. .

  Next, an example of the startup state referred to here using the activity of anaerobic ammonia oxidizing bacteria is shown below. A raw water pump continuously passes through a denitrification tank containing anaerobic ammonia-oxidizing bacteria from a raw water tank in which wastewater containing about 1.3 times the amount of nitrous acid relative to ammonia and ammonia is stored, and a water temperature of 30 ° C., pH 7 The anaerobic ammonia oxidation reaction was advanced under .6.

  FIG. 2 is a graph in which the amount of nitrous acid or nitric acid removed is plotted against the number of days elapsed, the nitrogen removal rate, and the amount of ammonia removed.

  As shown in FIG. 2, the nitrogen removal rate has a difference with respect to the nitrogen volume load until approximately 30 days have elapsed, and is in a state that hardly rises. In this case, it cannot be said that the start-up has been completed.

  However, the nitrogen removal rate increases from around 45 days and shows a stable value. In this case, it can be said that the startup has been completed.

  Moreover, as a judgment of start-up, in the reaction of anaerobic ammonia-oxidizing bacteria, the removal amount of nitrous acid or nitric acid with respect to the removal amount of ammonia of 1 is 1.32 and −0.26 (nitric acid production), respectively, from the reaction formula. It can be judged by using these. From FIG. 2, the reaction ratio varies until about 30 days have passed, and the anaerobic ammonia oxidation reaction has not sufficiently progressed, and it cannot be said that the start-up has been completed. On the other hand, the reaction ratio has stably changed from 1.32 to -0.26 from around 45 days elapsed. From this, it can be said that the start-up of the anaerobic ammonia oxidizing bacteria has been completed.

  If the reaction ratio stably shows values close to 1: 1.32 and −0.26, an anaerobic ammonia oxidation reaction is considered to be possible, so the nitrogen removal rate is low (1 kg N / m 3 / d) or less. It cannot be said that it is not in a standing state.

  Furthermore, as a judgment of the standing state of anaerobic ammonia-oxidizing bacteria, there is a feature that, by reacting, 0.13 hydrogen ions are used for ammonia 1 and the pH in the tank is increased. It is also possible to make a judgment using this.

  Next, an example of the start-up state of nitrite type nitrification is shown below. From the raw water tank in which wastewater containing about 700 mg N / L of ammonia is stored, water is continuously passed through the nitrification tank containing nitrifying bacteria with a raw water pump, and air is aerated with a blower at a water temperature of 20 ° C. to nitrous acid. The nitrification reaction was advanced.

  As shown in FIG. 3, the concentration of nitrous acid in the tank does not increase until around 15 days elapsed, and the ammonia concentration is in a state where there is almost no difference between the raw water and the treated water. For this reason, at this time, it cannot be said that it is in a startup state.

  The concentration of nitrous acid in the tank tends to increase and the concentration of ammonia also tends to decrease from around 20 days elapsed. In this case, it can be said that the nitrite type nitrification is started up.

  However, in order to advance the anaerobic ammonia oxidation reaction more efficiently and to raise the nitrogen removal rate from the viewpoint of wastewater treatment called nitrogen removal, the nitrification reaction is further advanced, and the ratio of ammonia and nitrous acid contained in the tank is further increased. It is necessary to approach 1: 1.32 (nitrification rate: 56.9%).

  In the case of FIG. 3, the ammonia concentration is about 300 mgN / L and the nitrite concentration is about 400 mgN / L around the lapse of 30 days. At this time, the nitrifying bacteria are sufficiently efficient for anaerobic ammonia oxidation reaction with ammonia and Nitric acid can be supplied, and it can be said that this is the optimum startup state of nitrite type nitrification for anaerobic ammonia oxidation reaction.

Schematic configuration diagram of a wastewater treatment apparatus according to an embodiment of the present invention A graph showing the relationship of the amount of nitrous acid or nitric acid to the elapsed days, nitrogen removal rate, and ammonia removal Graph showing the relationship between elapsed days and nitrogen concentration

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Raw water tank, 2 ... Raw water line, 3 ... Treatment tank, 4 ... Nitrification bacteria, 5 ... Anaerobic ammonia oxidation bacteria, 6 ... Treated water line, 7 ... Dissolved oxygen meter, 8 ... Air diffuser, 9 ... Nitrogen Gas generator, 10 ... nitrogen concentration analyzer, 11 ... circulation line, 12 ... flow meter, 13 ... first tank, 14 ... second tank, 15 ... first line, 16 ... second line, 20 ... Waste water treatment equipment

Claims (8)

  A treatment tank in which nitrogen-containing wastewater containing ammonia is fed through a raw water line, the treatment tank has nitrifying bacteria and anaerobic ammonia oxidizing bacteria, and a dissolved oxygen concentration of 1.5 to 5.0 mg / A wastewater treatment apparatus characterized by being controlled to L.   The wastewater treatment apparatus according to claim 1, wherein the treatment tank includes a dissolved oxygen meter that measures a dissolved oxygen concentration in the treatment tank, an air diffuser, and a nitrogen gas generator.   The wastewater treatment apparatus according to claim 1 or 2, wherein a first tank for starting up the nitrifying bacteria and a second tank for starting up the anaerobic ammonia-oxidizing bacteria are connected to the treatment tank, respectively. . The treatment tank comprises a nitrogen concentration meter for measuring the concentration of nitrogen in the treatment tank, and a circulation line for returning treated water from the treatment tank to the treatment tank.
According to the measured value of each nitrogen concentration meter,
When the concentration of nitrous acid nitrogen in the treatment tank is increased, the amount of air diffused by the air diffuser is decreased, and the flow rate of the raw water line is increased,
4. The control according to claim 2 or 3, wherein when the ammonia concentration in the treatment tank is increased, the amount of air diffused in the air diffuser is increased, the flow rate of the raw water line is decreased, and the amount of circulation in the circulation line is increased. Wastewater treatment equipment.   Nitrogen-containing wastewater containing ammonia is fed through a raw water line to a treatment tank having nitrifying bacteria and anaerobic ammonia-oxidizing bacteria and having a dissolved oxygen concentration controlled to 1.5 to 5.0 mg / L. A wastewater treatment method comprising nitrification and denitrification in the treatment tank.   The treatment tank includes a dissolved oxygen meter, an air diffuser, and a nitrogen gas generator that measure the dissolved oxygen concentration of the treatment tank, and the air diffuser and the nitrogen gas according to the measured value of the dissolved oxygen meter. The wastewater treatment method according to claim 5, wherein the generator is controlled.   The waste water treatment method according to claim 5 or 6, wherein the nitrifying bacteria and the anaerobic ammonia-oxidizing bacteria in the treatment tank are added to the treatment tank after being started up in separate tanks. The treatment tank comprises a nitrogen concentration meter for measuring the concentration of nitrogen in the treatment tank, and a circulation line for returning treated water from the treatment tank to the treatment tank.
According to the measured value of each nitrogen concentration meter,
When the concentration of nitrous acid nitrogen in the treatment tank is increased, the amount of air diffused by the air diffuser is decreased, and the flow rate of the raw water line is increased,
The control according to claim 6 or 7, wherein when the ammonia concentration in the treatment tank is increased, the amount of air diffused in the air diffuser is increased, the flow rate of the raw water line is decreased, and the amount of circulation in the circulation line is increased. Wastewater treatment method.

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