JP2013169529A - Wastewater treatment method and wastewater treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wastewater treatment method and wastewater treatment apparatus, which can stably perform a nitrite-type nitrification reaction efficiently at low cost by selectively suppressing the activity of nitrite-oxidizing bacteria.SOLUTION: A wastewater treatment method is a wastewater treatment method for ammoniac wastewater using a nitrification carrier 14 where ammonium-oxidizing bacteria and nitrite-oxidizing bacteria are immobilized, and includes: a nitrous acid oxidation step of oxidizing the ammoniac wastewater in a nitrification tank 42 to nitrous acid by using the ammonium-oxidizing bacteria; a step of measuring either a nitrate nitrogen concentration or a nitrite nitrogen concentration in the ammoniac wastewater; a step of stopping the supply of the ammoniac wastewater to the nitrification tank 42 before the nitrate nitrogen concentration increases or the nitrite nitrogen concentration decreases; and an aeration step of subjecting the nitrification carrier 14 in the ammoniac wastewater to aeration treatment.

Description

  The present invention particularly relates to a wastewater treatment method and a wastewater treatment apparatus using a nitrite type nitrification reaction.

Biological treatment for treating waste water and sewage with microorganisms is widely used because it can reduce costs, environmental burdens, and the like as compared with physicochemical treatment.
As a method of treating wastewater containing nitrogen compounds using biological treatment, first, ammonia is oxidized to nitrite by ammonia oxidizing bacteria, and then nitrite to nitric acid by nitrite oxidizing bacteria. There is known a nitrification process comprising a nitrification process that oxidizes and a denitrification process in which nitrous acid and nitric acid are reduced to nitrogen gas by denitrifying bacteria under anaerobic conditions. However, the growth rate of ammonia oxidizing bacteria was as slow as 1/10 that of nitrite oxidizing bacteria, and the nitrification reaction was prolonged.

  As a method for further improving the efficiency of this nitrification denitrification method, there is a nitrite type nitrification reaction. In the nitrite type nitrification reaction, the nitrification step is stopped by oxidation to nitrite by ammonia oxidizing bacteria in the above-mentioned nitrification denitrification method. Thereafter, nitrous acid is reduced to nitrogen by denitrifying bacteria. In this nitrite type nitrification reaction, it is necessary to suppress only a reaction in which ammonia is efficiently oxidized into nitrous acid and at the same time a reaction in which nitrous acid is oxidized into nitric acid.

Conventionally, as a method for producing a nitrite-type nitrification carrier in which ammonia-oxidizing bacteria are preferentially accumulated and nitrite-oxidizing bacteria are suppressed, the methods of Patent Documents 1 to 3 can be mentioned.
In the nitrification carrier disclosed in Patent Document 1, an immobilized microorganism carrier in which sludge containing Bacillus, which is a heat-resistant bacterium, is comprehensively immobilized inside is heat-treated at 40 ° C. or higher and 130 ° C. or lower. Biological treatment is performed using this heating carrier.

  The nitrification carrier disclosed in Patent Document 2 is a complex microorganism containing ammonia-oxidizing bacteria and nitrite-oxidizing bacteria, acid-treated in a pH range of 6.0 or less, and the accumulated sludge of this complex microorganism is adhered and immobilized on the carrier. They are manufactured as either entrapping immobilization carriers or granule carriers.

The nitrification carrier disclosed in Patent Document 3 has an adhesion immobilization carrier, a entrapping immobilization carrier, and a granule carrier with pH 9 formed by adhering sludge of a complex microorganism containing ammonia-oxidizing bacteria and nitrite-oxidizing bacteria to a carrier material. It is manufactured by washing with the above alkaline water.
By these methods, it is possible to efficiently produce a nitrite type nitrification carrier that can be limited to an oxidation reaction up to nitrous acid.

JP 2007-300931 A JP 2008-272610 A JP 2010-5517 A

However, when the nitrite type nitrification carrier is heat-treated, the nitrification carrier is heated at a predetermined temperature for a predetermined time, and therefore a container with high heat retention must be prepared.
When the nitrite type nitrification carrier is treated with acid or alkaline water, an acid or alkali chemical solution is required separately, and a reaction vessel having high corrosion resistance against this chemical solution must be prepared.

For this reason, there has been a problem that the manufacturing cost of the conventional nitrite type nitrification carrier is high.
Therefore, in order to solve the above-mentioned problems of the conventional technology, the present invention selectively suppresses the activity of nitrite-oxidizing bacteria and can efficiently and stably carry out a nitrite-type nitrification reaction at low cost. It is an object to provide a method and a wastewater treatment apparatus.

  The wastewater treatment method of the present invention is a wastewater treatment method for ammoniacal wastewater using a nitrification carrier on which ammonia-oxidizing bacteria and nitrite-oxidizing bacteria are immobilized, and the ammoniacal wastewater in a nitrification tank is treated with the ammonia-oxidizing bacteria. Nitrite oxidation step which oxidizes to nitrous acid in step, step of measuring either nitrate nitrogen concentration or nitrite nitrogen concentration in the ammoniacal wastewater, increase in nitrate nitrogen concentration or nitrite It is characterized by comprising a step of stopping the supply of the ammonia waste water to the nitrification tank before the nitrogen concentration is reduced, and an aeration step of aeration treatment of the nitrification carrier in the ammonia waste water.

  In this way, after stopping at a predetermined nitrate nitrogen concentration or nitrite nitrogen concentration in the nitrite oxidation step, the ammonia oxidizing bacteria are activated by a simple method of aeration in the nitrification tank, and the activity of the nitrite oxidizing bacteria Can be selectively suppressed and killed. Moreover, compared with the conventional heating and activation of ammonia-oxidizing bacteria using a chemical solution, it is possible to reduce the cost of the wastewater treatment facility by the nitrite type nitrification reaction.

In this case, the aeration process is 20 to 140 days after the start of the nitrite oxidation process, and the aeration time is 12 to 24 hours.
Thus, the nitrification carrier can be efficiently aerated before the nitrate nitrogen concentration increases or the nitrite nitrogen concentration decreases.

The aeration step is characterized in that methane is aerated in the ammoniacal wastewater.
As a result, the ammonia-oxidizing bacteria in the nitrifying carrier oxidize methane, which is a substitute for ammonia, to generate methanol and acquire energy, thereby reducing the death caused by the autolysis reaction. Therefore, killing of nitrite-oxidizing bacteria is promoted compared to ammonia-oxidizing bacteria, and the proportion of nitrite-oxidizing bacteria in the nitrification carrier can be reduced.

The methane is characterized by supplying a molar amount at least equivalent to denitrogenated nitrogen.
This makes it possible to optimize the supply amount of methane and effectively reduce the death of ammonia-oxidizing bacteria.

  The wastewater treatment apparatus of the present invention is a nitrification carrier in which ammonia-oxidizing bacteria and nitrite-oxidizing bacteria are immobilized, which nitrifies ammoniacal wastewater, a nitrification tank that performs a nitrification reaction of ammoniacal wastewater using the nitrification carrier, An ammonia measuring means for measuring either the nitrate nitrogen concentration or the nitrite nitrogen concentration in the ammonia waste water, an aeration means for aeration treatment of the nitrification carrier in the ammonia waste water, and the ammonia measuring means. Control means for aeration of the nitrification carrier by stopping supply of the ammonia waste water to the nitrification tank before the nitrate nitrogen concentration increases or the nitrite nitrogen concentration decreases based on the measured value It is characterized by having.

  In this way, after stopping at a predetermined nitrate nitrogen concentration or nitrite nitrogen concentration in the nitrite oxidation step, the ammonia oxidizing bacteria are activated by a simple method of aeration in the nitrification tank, and the activity of the nitrite oxidizing bacteria Can be selectively suppressed and killed. Moreover, compared with the conventional heating and activation of ammonia-oxidizing bacteria using a chemical solution, it is possible to reduce the cost of the wastewater treatment facility by the nitrite type nitrification reaction.

In this case, the aeration means is 20 to 140 days after the start of the nitrite oxidation step, and the aeration time is 12 to 24 hours.
Thus, the nitrification carrier can be efficiently aerated before the nitrate nitrogen concentration increases or the nitrite nitrogen concentration decreases.

The nitrification tank comprises first and second nitrification tanks connected in parallel with the ammonia waste water reservoir, and the ammonia waste water is supplied between the reservoir and the first and second nitrification tanks. A valve for controlling, and the control means supplies the ammonia waste water to the second nitrification tank while the supply of the ammonia waste water to the first nitrification tank is stopped and the nitrification carrier is aerated. A signal for performing switching control for performing the nitrite nitrification step is transmitted to the valve.
Thereby, a nitrite type nitrification reaction can be performed continuously and ammonia waste water can be treated efficiently.

The aeration means is characterized in that methane is aerated in the ammoniacal wastewater.
As a result, the ammonia-oxidizing bacteria in the nitrifying carrier oxidize methane, which is a substitute for ammonia, to generate methanol and acquire energy, thereby reducing the death caused by the autolysis reaction. Therefore, killing of nitrite-oxidizing bacteria is promoted compared to ammonia-oxidizing bacteria, and the proportion of nitrite-oxidizing bacteria in the nitrification carrier can be reduced.

The methane is characterized by supplying a molar amount at least equivalent to denitrogenated nitrogen.
This makes it possible to optimize the supply amount of methane and effectively reduce the killing of ammonia-oxidizing bacteria.

The nitrification tank includes an aeration tank that collects a part of the nitrification carrier in the tank, performs an aeration treatment, and then returns to the aeration tank.
Thereby, a nitrite type nitrification reaction can be performed continuously and ammonia waste water can be treated efficiently. Moreover, a processing tank can be reduced in size and space saving of the whole waste water treatment apparatus can be achieved.

The aeration tank includes a methane aeration tank that dissolves methane in the treated water discharged from the nitrification tank, and the methane aeration tank supplies methane-dissolved treated water to the aeration tank.
As a result, the ammonia-oxidizing bacteria in the nitrifying carrier oxidize methane, which is a substitute for ammonia, to generate methanol and acquire energy, thereby reducing the death caused by the autolysis reaction. Therefore, killing of nitrite-oxidizing bacteria is promoted compared to ammonia-oxidizing bacteria, and the proportion of nitrite-oxidizing bacteria in the nitrification carrier can be reduced.

  According to the wastewater treatment method of the present invention, after stopping at a predetermined nitrate nitrogen concentration or nitrite nitrogen concentration in the nitrite oxidation step, the ammonia oxidizing bacteria are activated by a simple method of aeration in the nitrification tank. It can be killed by selectively suppressing the activity of nitrite-oxidizing bacteria. In addition, as compared with the conventional warming and activation of ammonia oxidizing bacteria using a chemical solution, it is possible to achieve a stable nitrite type nitrification reaction while reducing the cost of wastewater treatment facilities by nitrite type nitrification reaction.

It is explanatory drawing of the waste water treatment apparatus of this invention. It is explanatory drawing of the outline of a structure of an experiment apparatus. It is explanatory drawing which shows the composition of the synthetic wastewater used in experiment. It is the graph which showed the relationship between the wastewater treatment time by the 1st wastewater treatment experiment, and each nitrogen concentration in wastewater. It is the graph which showed the relationship between the wastewater treatment time by the 2nd wastewater treatment experiment, and each nitrogen concentration in wastewater. It is explanatory drawing of the waste water treatment apparatus of the modification 1. It is explanatory drawing of the wastewater treatment apparatus of the modification 2.

Embodiments of a wastewater treatment method and a wastewater treatment apparatus of the present invention will be described in detail below with reference to the accompanying drawings.
First, the nitrite type nitrification carrier handled in this embodiment will be described. Nitrite-type nitrification carriers are produced using microbial sludge, which is a complex microbial sludge mixed with a large number of microorganisms, such as sludge from lakes, rivers, sea, or activated sludge from sewage and industrial wastewater treatment plants . In particular, it is desirable to use sludge containing a large amount of nitrifying bacteria such as ammonia oxidizing bacteria and nitrite oxidizing bacteria as a microorganism supply source.

  Nitrite-type nitrification carrier is an adsorbed immobilization carrier formed by adhering a complex microbial sludge having nitrification performance containing ammonia-oxidizing bacteria and nitrite-oxidizing bacteria to a carrier material, and using a complex microbial sludge as a carrier material. A entrapping immobilization support formed by entrapment or a nitrification granule support formed by the self-granulating force of complex microbial sludge can be used.

  As a carrier material used for adhesion and fixation, a plastic carrier such as polyvinyl alcohol, alginic acid, ethylene glycol gel, cellulose, polyester, polypropylene, vinyl chloride, or the like can be suitably used. In addition, as the shape of the carrier material, a spherical shape, a cylindrical shape, a porous shape, a cubic shape, a honeycomb shape, or the like can be suitably used.

  Carrier materials used for comprehensive immobilization include monomethacrylates, monoacrylates, dimethacrylates, diacrylates, trimethacrylates, triacrylates, tetraacrylates, urethane acrylates, epoxy acrylates, etc. Polyvinyl alcohol, acrylamide, photocurable polyvinyl alcohol, photocurable polyethylene glycol, photocurable polyethylene glycol polypropylene glycol prepolymer, and the like can be used.

  Also, nitrifying bacteria can be used as a carrier by forming granules by self-granulating force due to its viscosity. In addition, the formation of granules includes not only those formed by self-granulating force but also granules configured to adhere to the outer periphery of granules formed by other bacteria.

  As a method for producing such a nitrite type nitrification carrier, for example, a sheet molding method for producing a square carrier by making a mixture of a microorganism and a polymer material into a sheet shape and finely cutting the mixture can be used. In addition, a tube molding method for producing a cylindrical carrier by injecting a mixture of a microorganism and a polymer material into a vinyl tube having a diameter of several millimeters and extruding it while polymerizing it, and cutting it into a certain length, or a microorganism Alternatively, a dropping granulation method in which a mixture of a polymer material and a polymer material is dropped into another liquid to produce a spherical carrier may be used.

In order to confirm the nitrite type nitrification performance of the nitrite type nitrification carrier of the present invention, a first wastewater treatment experiment was performed by the following method.
FIG. 2 is an explanatory diagram of a schematic configuration of the experimental apparatus. Each tank in the figure shows a state seen through. As shown in the figure, the experimental apparatus 10 includes a reaction tank 12, and a large number of nitrification carriers 14 are placed in the reaction tank 12. The reaction tank 12 is connected to a raw water tank 18 through a raw water pipe 16. Synthetic waste water simulating sewage is stored in the raw water tank 18, and by driving the raw water pump 20 on the raw water pipe 16, the synthetic waste water in the raw water tank 18 is sent to the reaction tank 12 via the raw water pipe 16. It is liquid.

  An adjustment liquid tank 24 is connected to the reaction tank 12 via an adjustment liquid pipe 22. An adjustment liquid pump 26 is disposed in the adjustment liquid pipe 22, and the pH adjustment liquid in the adjustment liquid tank 24 is sent to the reaction tank 12 by driving the adjustment liquid pump 26.

  An air pump pipe 28 is disposed inside the reaction tank 12. The air pump pipe 28 is connected to an air supply means (not shown), and air is supplied from the lower end of the air pump pipe 28 by the air supply means. When air is supplied to the air pump pipe 28, air is diffused from the lower end of the air pump pipe 28, and aeration and agitation are performed. That is, as the bubbles diffused from the lower end of the air pump pipe 28 rise, the nitrification carrier 14 flows in the tank and agitation is performed, and air is supplied to the nitrification carrier 14 to perform biological treatment.

  A pH electrode 30 is disposed inside the reaction vessel 12. The pH electrode 30 is connected to a pH adjuster 32 so that the pH in the reaction vessel 12 can be measured. The pH adjuster 32 is connected to the adjustment liquid pump 26, and the drive of the adjustment liquid pump 26 is controlled based on the measured value of the pH electrode 30. That is, the adjustment liquid pump 26 is driven so that the inside of the reaction tank 12 has a predetermined pH, and the pH adjustment liquid is supplied to the reaction tank 12. Thereby, the inside of the reaction vessel 12 can be controlled to a desired pH. The treated wastewater flows out as treated water from an outflow pipe (not shown) provided at the upper side of the reaction tank 12.

  In this experiment, the nitrification carrier 14 to be tested is obtained by mixing surplus sludge from a sewage treatment plant with a polyethylene glycol-based prepolymer, adding potassium persulfide as a polymerization initiator, polymerizing it, and shaping it into a 3 mm square cube. Used. In addition, what was comprehensively fixed so that the content of sludge in the carrier was 2 W / V% and the prepolymer content was 10 V / V% was used. In addition to the above, the above-mentioned adhesion-immobilized carrier and nitrified granule carrier may be used.

  The obtained microbial carrier was charged into a reaction tank 12 filled with tap water at 10 V / V% and subjected to aeration treatment for 0 hours, 12 hours, 24 hours, and 48 hours to produce a nitrite type nitrification carrier. The amount of aeration air was blown in air equivalent to twice the volume of the reaction tank 12 per minute (excessive than the normal nitrification reaction).

  The wastewater used in this experiment was the synthetic wastewater shown in FIG. 3 simulating sewage, and was used by adjusting the ammonia nitrogen concentration to 40 mg / L. The experiment was started after filling the reaction tank 12 with synthetic wastewater.

  The hydraulic retention time of the wastewater in the experimental apparatus 10 is 3 hours, and if the dissolved oxygen (DO) in the reaction vessel 12 is low, nitrite type nitrification can be caused by this, so the aeration amount to be blown in is increased. The wastewater treatment was carried out while maintaining the dissolved oxygen concentration in the reaction tank 12 at 4.0 mg / L or more.

In addition, when the pH in the reaction tank 12 in the experimental apparatus 10 is high, nitrite-type nitrification can be caused thereby, so that the wastewater treatment was performed by adjusting the pH in the reaction tank to 7.5.
Further, if the water temperature in the reaction tank 12 in the experimental apparatus 10 is high, nitrite-type nitrification can be caused thereby, and the waste water treatment was performed by adjusting the water temperature in the reaction tank to 20 ° C.

  The results of the first wastewater treatment experiment are shown in FIG. FIG. 4 is a graph showing the relationship between the wastewater treatment time in the first wastewater treatment experiment and each nitrogen concentration in the wastewater, and (A) shows the case where the aeration treatment is not performed (aeration time 0), B) shows a case where the aeration process is performed for 12 hours, (C) shows a case where the aeration process is performed for 24 hours, and (D) shows a case where the aeration process is performed for 48 hours.

  In each graph, ○ indicates the ammonia nitrogen concentration of the raw water, ● indicates the ammonia nitrogen concentration of the treated water, ▲ indicates the nitrite nitrogen concentration of the treated water, and ■ indicates the nitrate nitrogen concentration of the treated water Is shown.

  As shown in FIG. 4A, in the wastewater treatment when the aeration treatment is not performed (aeration time 0), the nitrite nitrogen concentration and the nitrate nitrogen concentration both increased after the start of the experiment, but the nitrite nitrogen concentration Decreased immediately. Since then, nitrite-oxidizing bacteria are activated due to high nitrate nitrogen concentration. Thus, around the 10th day from the start, nitrite oxidation activity rose simultaneously with ammonia oxidation activity.

  As shown in FIG. 4B, in the wastewater treatment in the case of aeration for 12 hours, the ammonia-oxidizing bacteria are activated since the nitrite nitrogen concentration has increased after the start of the experiment. On the other hand, the nitrate nitrogen concentration also gradually increases, and nitrite oxidizing bacteria are activated. Thus, while the ammonia oxidation activity rose around the 20th day, the nitrite oxidation activity started to rise around the 20th day and rose around the 90th day.

  As shown in FIG. 4C, in the wastewater treatment in the case of aeration for 24 hours, the ammonia-oxidizing bacteria are activated since the concentration of nitrite nitrogen has increased after the start of the experiment. On the other hand, nitrate nitrogen concentration also starts to increase after 140 days, and nitrite oxidizing bacteria are activated. Thus, while the ammonia oxidation activity rose around the 20th day, the nitrite oxidation activity started to rise around the 140th day and rose around the 190th day.

  As shown in FIG. 4D, in the wastewater treatment in the case of aeration treatment for 48 hours, after the start of the experiment, the concentration of nitrite nitrogen begins to gradually increase, and ammonia oxidizing bacteria are activated. On the other hand, the nitrate nitrogen concentration starts to increase around 170 days, and nitrite oxidizing bacteria are activated. As described above, the nitrite oxidation activity started to increase from around the 170th day, whereas the ammonia oxidation activity rose around the 100th day. Moreover, the ammonia nitrogen concentration which flows out shows a constant value after 100 days, and is in a saturated state.

  From the above results, as the timing of the aeration process, the nitrification reaction of the ammonia-oxidizing bacteria shown in FIG. 4B is stable, and a high value of nitrite nitrogen concentration can be reached in a relatively short time. Desirably 20 days after the start. Further, as shown in FIG. 4C, it is desirable that the nitrite-oxidizing bacteria are activated and before 140 days before the nitrate nitrogen concentration starts to increase.

  Next, the aeration time is preferably between 12 hours shown in FIG. 4 (B) and 48 hours shown in FIG. 4 (C). This is because if the aeration time is less than 12 hours, ammonia-oxidizing bacteria and nitrite-oxidizing bacteria are not sufficiently killed and remain. On the other hand, if it exceeds 48 hours, the activity of the ammonia-oxidizing bacteria is delayed. From this experiment, it was confirmed that a good nitrite-type nitrification carrier was obtained when the microorganism carrier was subjected to aeration treatment for 20 to 140 days after the start of the nitrification reaction and the aeration time was 12 to 24 hours.

Next, a second wastewater treatment experiment was conducted in order to examine a method of supplying methane as a method for preventing a decrease in activity of ammonia oxidizing bacteria simultaneously with nitrite oxidizing bacteria by aeration treatment.
In the second wastewater treatment experiment, the experimental apparatus 10 shown in FIG. 2 was used, and the same microbial carrier used in the first wastewater treatment experiment was used as the nitrification carrier 14 to be tested. And the reaction tank 12 was filled with tap water, methane gas was inject | poured into the reaction tank 12, and the methane saturated solution was produced. Thereafter, dilution with tap water is adjusted so that the chemical oxygen demand (COD; Chemical Oxygen Demand) becomes 70 mg / L, and the microbial carrier obtained in the reaction tank 12 filled with the methane solution is 10 V / V%. Then, the mixture was aerated for 24 hours to produce a nitrite type nitrification carrier.

  The wastewater used in this experiment was the synthetic wastewater shown in FIG. 3 simulating sewage, and was used by adjusting the ammonia nitrogen concentration to 40 mg / L. The experiment was started after filling the reaction tank 12 with synthetic wastewater.

  In addition, the hydraulic residence time of the wastewater in the experimental apparatus 10 is 3 hours, and if the dissolved oxygen (DO) in the reaction tank 12 is low, nitrite-type nitrification can be caused thereby, so the aeration amount to be blown in The amount of dissolved oxygen in the reaction tank 12 was increased to 4.0 mg / L or more to perform wastewater treatment.

In addition, when the pH in the reaction tank 12 in the experimental apparatus 10 is high, nitrite-type nitrification can be caused thereby, so that the wastewater treatment was performed by adjusting the pH in the reaction tank to 7.5.
Further, if the water temperature in the reaction tank 12 in the experimental apparatus 10 is high, nitrite-type nitrification can be caused thereby, and the waste water treatment was performed by adjusting the water temperature in the reaction tank to 20 ° C.

  The result of the second wastewater treatment experiment is shown in FIG. FIG. 5 is a graph showing the relationship between the wastewater treatment time and the nitrogen concentration in the wastewater in the second wastewater treatment experiment, where (A) shows the case of aeration for 12 hours, and (B) shows the aeration for 24 hours. The case where it processed is shown, (C) has shown the case where it carries out the aeration process for 48 hours. In each graph, ○ indicates the ammonia nitrogen concentration of the raw water, ● indicates the ammonia nitrogen concentration of the treated water when aerated with tap water, and Δ indicates the treated water when aerated with a methane solution. Ammonia nitrogen concentration is shown.

As shown in FIG. 5A, the number of days for the nitrogen concentration to reach 5 mg / L was about 20 days in the case of tap water aeration and about 13 days in the case of methane aeration.
As shown in FIG. 5B, the number of days for the nitrogen concentration to reach 5 mg / L was about 28 days in the case of tap water aeration and about 21 days in the case of methane aeration.
As shown in FIG. 5C, the number of days for the nitrogen concentration to reach 15 mg / L was about 44 days in the case of tap water aeration and about 31 days in the case of methane aeration.

  As a result, it was confirmed that by aeration treatment of the microorganism carrier with a methane solution, the rise of ammonia oxidation activity was accelerated by about 7 to 10 days regardless of the aeration treatment time. Ammonia-oxidizing bacteria in the nitrifying carrier oxidize methane, which is a substitute for ammonia, to generate methanol and acquire energy, thereby reducing the death caused by autolysis. Therefore, killing of nitrite-oxidizing bacteria is promoted compared to ammonia-oxidizing bacteria, and the proportion of nitrite-oxidizing bacteria in the nitrification carrier can be reduced.

Next, an embodiment of a wastewater treatment apparatus made based on the above experimental results will be described.
FIG. 1 is an explanatory diagram of the wastewater treatment method of the present invention. As shown in the drawing, the wastewater treatment apparatus 40 of the present invention includes a nitrification carrier 14 in which ammonia-oxidizing bacteria and nitrite-oxidizing bacteria that nitrify the ammoniacal wastewater are immobilized, and ammoniacal wastewater using the nitrification carrier 14 A nitrification tank 42 for performing the nitrification reaction, ammonia measuring means 50 for measuring either nitrate nitrogen concentration or nitrite nitrogen concentration in the ammonia waste water, and the nitrification carrier 14 in the ammonia waste water. Based on the measured values of the aeration means 60 for aeration and the ammonia measurement means 50, the ammonia waste water to the nitrification tank 42 before the nitrate nitrogen concentration increases or the nitrite nitrogen concentration decreases. The control unit 70 which stops supply and performs the aeration process of the nitrification carrier 14 has a main basic configuration.

  The nitrification tank 42 is connected to a storage tank 44 for ammonia waste water through a pipe 46. The pipe 46 is provided with a valve 48 that can switch inflow or stop of wastewater. A large number of nitrite-type nitrification carriers 14 are placed in the nitrification tank 42. This nitrification carrier 14 is the same as the carrier used in the above-described experiment, and is an adhesion-fixation formed by adhering sludge of a complex microbial system having nitrification performance including ammonia-oxidizing bacteria and nitrite-oxidizing bacteria to the carrier material. A nitrifying carrier, a entrapping immobilization carrier formed by encapsulating composite microbial sludge in a carrier material, or a nitrified granule carrier formed by the self-granulating force of composite microbial sludge is used.

  The nitrification carrier 14 oxidizes ammoniacal nitrogen contained in the ammoniacal wastewater in the nitrification tank 42 to nitrous acid. The treated water treated in the nitrification tank 42 is supplied to a denitrification tank such as a subsequent denitrification reaction (not shown).

  An ammonia measuring means 50 is installed in the nitrification tank 42. The ammonia measuring means 50 is a measuring means capable of measuring the ammonia nitrogen concentration of the ammonia waste water and either the nitrite nitrogen concentration or the nitrate nitrogen concentration.

  Further, aeration means 60 is installed in the nitrification tank 42. The aeration means 60 includes an aeration pipe 62 and an aeration pump 64. The aeration pipe 62 is connected to an aeration pump 64, and air is diffused from the aeration pipe 62 into the nitrification tank 42 by the aeration pump 64, and aeration agitation is performed. As the air bubbles diffused from the aeration pipe 62 rise, the nitrification carrier 14 flows in the tank and agitation is performed, and air is supplied to the nitrification carrier 14 to perform biological treatment. Further, after the supply of ammonia waste water to the nitrification tank 42 is stopped, the nitrite oxidizing bacteria can be selectively killed by aeration in the tank. Note that the air of the aeration means 60 uses a gas that does not contain ammonia, which is an active source of ammonia oxidizing bacteria.

  The control means 70 is electrically connected to the valve 48, the ammonia measuring means 50, and the aeration means 60. The control means 70 drives and controls the valve 48 and the aeration means 60 based on the measurement value of the ammonia measurement means 50. Specifically, the control means 70 supplies ammonia wastewater to the nitrification tank 42 before the nitrate nitrogen concentration in the nitrification tank 42 increases or the nitrite nitrogen concentration decreases based on the result of the wastewater treatment experiment described above. A control signal for stopping is transmitted to the valve 48. Then, a control signal for aeration treatment of the nitrification carrier 14 in the ammonia waste water is transmitted to the aeration means 60.

  In the wastewater treatment device 40 having such a configuration, when ammonia wastewater is supplied from the water storage tank 44 into the nitrification tank 42, the nitrification reaction is performed by the nitrification carrier 14 in the tank. During the nitrification reaction, the ammonia measurement means 50 measures the ammonia nitrogen concentration and either the nitrite nitrogen concentration or the nitrate nitrogen concentration by the ammonia waste water. The control means 70 supplies the ammonia waste water to the nitrification tank 42 before the nitrate nitrogen concentration in the nitrification tank 42 increases or the nitrite nitrogen concentration decreases based on the measurement value of the ammonia measurement means 50. A control signal to be stopped is transmitted to the valve 48. Then, after the supply of ammonia waste water in the tank is stopped, a control signal for aeration treatment of the nitrification carrier 14 in the ammonia waste water is transmitted to the aeration means 60. As a result, the nitrification carrier 14 in the nitrification tank 42 is depleted of ammonia supply, and ammonia oxidizing bacteria become inactive. Along with this, the supply of nitrous acid is depleted and nitrite oxidizing bacteria become inactive. In addition, the aeration treatment accelerates and kills ammonia-oxidizing bacteria and nitrite-oxidizing bacteria by autolysis or by heterotrophic bacteria. In the present invention, since the aeration treatment is performed before the nitrate nitrogen concentration is increased or the nitrite nitrogen concentration is decreased, that is, before the nitrite oxidizing bacteria are activated, the nitrification carrier 14 is oxidized with ammonia as compared with the nitrite oxidizing bacteria. A lot of bacteria.

  The timing of the aeration process is 20 days after the start of the nitrification reaction, in which the nitrification reaction of ammonia-oxidizing bacteria is stabilized and a high value of nitrite nitrogen can be reached in a relatively short time, based on wastewater treatment experiments. It is desirable that Moreover, it is desirable that it is before 140 days when nitrite-oxidizing bacteria are activated and the nitrate nitrogen concentration starts to increase.

  Further, the aeration step may be configured to supply methane gas from a methane gas supply means (not shown) to the aeration pipe 62 to aerate methane into the ammoniacal waste water. Thereby, the ammonia oxidizing bacteria in the nitrification carrier 14 can reduce the death due to the self-decomposing reaction by generating methanol by oxidizing methane, which is an alternative to ammonia, and acquiring energy. Therefore, killing of nitrite oxidizing bacteria is promoted compared to ammonia oxidizing bacteria, and the ratio of nitrite oxidizing bacteria in the nitrification carrier 14 can be reduced.

  The amount of methane gas to be supplied is preferably a molar amount at least equivalent to that of nitrogen that has been denitrified. This is because it is possible to optimize the supply amount of methane and effectively reduce the killing of ammonia-oxidizing bacteria.

  As a result, after stopping at a predetermined nitrate nitrogen concentration or nitrite nitrogen concentration in the nitrite oxidation step, the ammonia oxidizing bacteria are activated by a simple method of aeration in the nitrification tank 42, and the nitrite oxidizing bacteria are The activity can be selectively suppressed and killed. In addition, compared to conventional warming and activation of ammonia-oxidizing bacteria using chemicals, it is possible to perform stable nitrite-type nitrification reactions while reducing the cost of wastewater treatment facilities by nitrite-type nitrification reactions It becomes.

  Next, an embodiment of the wastewater treatment apparatus of Modification 1 will be described. FIG. 6 is an explanatory diagram of a wastewater treatment apparatus according to the first modification. As shown in the figure, the wastewater treatment apparatus 40A of Modification 1 includes a first nitrification tank 42A and a second nitrification tank 42B, and is connected in parallel to a water storage tank 44 of the ammoniacal wastewater. First and second valves 48A and 48B are respectively installed in the piping 46A branched in parallel from the water storage tank 44 to the first and second nitrification tanks 42A and 42B. The first and second nitrification tanks 42A and 42B are provided with first and second ammonia measuring means 50A and 50B and first and second aeration means 60A and 60B, respectively. The control means 70A is electrically connected to the first and second valves 48A and 48B, the first and second ammonia measuring means 50A and 50B, and the first and second aeration means 60A and 60B.

  In the wastewater treatment apparatus 40A of Modification 1 having such a configuration, first, ammonia wastewater from the storage tank 44 is supplied to one of the first and second nitrification tanks 42A and 42B, for example, the first nitrification tank 42A. Is done. At this time, the supply of the ammonia waste water to the second nitrification tank 42B is stopped. Then, the nitrification reaction is performed by the nitrification carrier 14 in the tank. During the nitrification reaction, the first ammonia measuring means 50A measures the ammonia nitrogen concentration and either the nitrite nitrogen concentration or the nitrate nitrogen concentration by the ammonia waste water. In the control means 70A, based on the measurement value of the first ammonia measuring means 50A, before the nitrate nitrogen concentration in the first nitrification tank 42A increases or the nitrite nitrogen concentration decreases, A control signal for stopping the supply of the ammonia waste water is transmitted to the first valve 48A. Accordingly, a control signal for opening the second valve 48B and supplying ammonia wastewater to the second nitrification tank 42B is transmitted to the second valve 48B.

  Then, after the supply of the ammoniacal wastewater in the first nitrification tank 42A is stopped, a control signal for aeration treatment of the nitrification carrier 14 in the ammoniacal wastewater is transmitted to the first aeration means 60A. As a result, the nitrification carrier 14 in the first nitrification tank 42A is depleted of ammonia supply, and ammonia oxidizing bacteria become inactive. Along with this, the supply of nitrous acid is depleted and nitrite oxidizing bacteria become inactive. In addition, the aeration treatment accelerates and kills ammonia-oxidizing bacteria and nitrite-oxidizing bacteria by autolysis or by heterotrophic bacteria.

  During the aeration process of the first nitrification tank 42A, the nitrification reaction of ammonia waste water is performed in the second nitrification tank 42B by the nitrification carrier 14 in the tank. During the nitrification reaction in the second nitrification tank 42B, the ammonia ammonia nitrogen concentration and any one of the nitrite nitrogen concentration and the nitrate nitrogen concentration are measured by the second ammonia measuring means 50B. In the control means 70A, based on the measured value of the second ammonia measuring means 50B, before the nitrate nitrogen concentration in the second nitrification tank 42B increases or the nitrite nitrogen concentration decreases, the control means 70A supplies the above-mentioned to the second nitrification tank 42B. A control signal for stopping the supply of ammonia waste water is transmitted to the second valve 48B. Accordingly, in the first nitrification tank 42A, since the aeration process described above has been completed, a control signal for opening the first valve 48A and supplying ammonia wastewater to the first nitrification tank 42A is supplied to the first valve 48A. Send.

  By repeating such a process, even if the nitrification reaction of ammonia wastewater is stopped in any one nitrification tank by the aeration process, the nitrification reaction of ammonia wastewater can be performed in either one nitrification tank. The nitrification reaction of ammonia waste water can be treated continuously.

  Note that the wastewater treatment apparatus 40A of the modified example 1 is also nitrite-like, as in the wastewater treatment apparatus 40 shown in FIG. 1, because the nitrification reaction of the ammonia oxidizing bacteria is stabilized based on the wastewater treatment experiment. It is desirable that it is 20 days after the start of the nitrification reaction that allows a high value of nitrogen concentration to be reached in a relatively short time. Moreover, it is desirable that it is before 140 days when nitrite-oxidizing bacteria are activated and the nitrate nitrogen concentration starts to increase.

  Further, the aeration process may be configured to supply methane gas to the aeration pipes 62A and 62B from a methane gas supply means (not shown) to aerate methane into the ammoniacal waste water. The amount of methane gas to be supplied is preferably a molar amount at least equivalent to nitrogen to be denitrified.

  Next, an embodiment of the wastewater treatment apparatus of Modification 2 will be described. FIG. 7 is an explanatory diagram of a wastewater treatment apparatus according to the second modification. In the wastewater treatment apparatus 40 </ b> B of the second modification, the aeration tank 80 is connected to the nitrification tank 420. The aeration tank 80 is a processing tank that is smaller than the nitrification tank 420, and an aeration means 600 is installed in the tank. The aeration tank 80 includes a drawing pipe 82 for collecting a part of the nitrification carrier 14 of the nitrification tank 420 together with the ammonia waste water, and a part of the nitrification carrier 14 aerated in the aeration tank 80 together with the ammonia waste water. A pipe 84 that returns to the nitrification tank 420 and a pipe 86 that returns the treated water in the aeration tank 80 to the nitrification tank 420 are connected. A pump 81 is installed in the drawing pipe 82. Valves 83 and 85 are installed in the pipes 84 and 86, respectively.

Further, the wastewater treatment apparatus 40B according to the modified example 2 is provided with a return pipe 90 that returns a part of the treated water discharged from the tank through the nitrification reaction to the aeration tank 80. In the return pipe 90, a valve 92, a pump 94, and a methane aeration tank 96 are installed. The treated water supplied from the return pipe 90 to the aeration tank 80 does not contain ammonia as an active source of ammonia oxidizing bacteria.
The methane aeration tank 96 is a tank capable of supplying to the aeration tank 80 treated water obtained by aeration of methane gas into treated water and dissolving methane.

  The control means 70B is electrically connected to the valves 83, 85, 92, the pumps 81, 94, the ammonia measuring means 50, and the aeration means 60 (the control means 70B and the valves 83, 85, FIG. 92, the connecting line between the control means 70B and the pumps 81 and 94 is omitted).

  In the wastewater treatment apparatus 40B of Modification 2 having such a configuration, when ammoniacal wastewater is supplied from the water storage tank 44 into the nitrification tank 420, the nitrification reaction is performed by the nitrification carrier 14 in the tank. During the nitrification reaction, the ammonia measurement means 50 measures the ammonia nitrogen concentration and either the nitrite nitrogen concentration or the nitrate nitrogen concentration by the ammonia waste water.

  The aeration treatment in the aeration tank 80 is performed 20 to 140 days after the start of the nitrous acid oxidation step, and the aeration time is 12 to 24 hours based on the above-described wastewater treatment experiment. A predetermined amount of the nitrification carrier 14 is supplied to the aeration tank 80 from the nitrification tank 420 through the extraction pipe 82 together with the ammonia waste water so that the aeration process is performed at this timing.

  Further, a control signal for opening the valves 85 and 92 is transmitted to the valves 85 and 92 from the control means 70B. The valve 83 is closed. A part of the treated water oxidized in the nitrification tank 420 is supplied from the return pipe 90 to the aeration tank 80. This treated water does not contain ammonia. In the aeration tank 80, treated water is supplied to the nitrification tank 420 via the pipe 86. As a result, the ammoniacal nitrogen concentration in the aeration tank 80 is diluted with the treated water from the return pipe 90 and decreases. Then, the nitrification carrier 14 in the aeration tank 80 is aerated by the aeration means 600. The nitrification carrier 14 in the aeration tank 80 is depleted of ammonia supply, and ammonia oxidizing bacteria become inactive. Along with this, the supply of nitrous acid is depleted and nitrite oxidizing bacteria become inactive. In addition, the aeration treatment accelerates and kills ammonia-oxidizing bacteria and nitrite-oxidizing bacteria by autolysis or by heterotrophic bacteria. Thereafter, a control signal for opening the valve 83 is transmitted to the valve 83 by the control means 70B, and the nitrification carrier 14 and the treated water are supplied to the nitrification tank 420 via the pipe 84.

  In addition, the methane aeration tank 96 provided in the return pipe 90 can supply treated water in which methane gas is aerated to the treated water and methane is dissolved to the aeration tank 80. Thereby, in the aeration process in the aeration tank 80, the ammonia oxidizing bacteria in the nitrification carrier 14 oxidize methane, which is an alternative to ammonia, to generate methanol, and acquire energy, thereby obtaining self-decomposition reaction. Death can be reduced. Therefore, killing of nitrite oxidizing bacteria is promoted compared to ammonia oxidizing bacteria, and the ratio of nitrite oxidizing bacteria in the nitrification carrier 14 can be reduced.

  According to the wastewater treatment apparatus 40B of Modification 2 having such a configuration, a part of the nitrification carrier 14 is extracted from the nitrification tank 420 and aerated in the aeration tank 80, and then returned to the nitrification tank 420. The nitrification reaction of ammonia waste water can be continuously processed without stopping the nitrification reaction in the nitrification tank 420. In addition, the processing tank can be downsized as compared with the configuration of the first modification, and the entire apparatus can be saved in space.

  The present invention is particularly useful in the field of wastewater treatment of ammoniacal wastewater among various industrial wastewaters.

10 ......... Experimental equipment, 12 ......... Reaction tank, 14 ......... Nitrification carrier, 16 ...... Raw water piping, 18 ...... Raw water tank, 20 ...... Raw water pump, 22 ...... Adjustment liquid piping, 24 ......... Adjusted liquid tank, 26 ......... Adjusted liquid pump, 28 ......... Air pump tube, 30 ......... pH electrode, 32 ......... pH controller, 40, 40A, 40B ......... Waste water treatment device, 42, 42A, 42B, 420 ......... Nitrification tank, 44 ......... Water storage tank, 46 ......... Piping, 48 ......... Valve, 48A ......... First valve, 48B ......... Second valve, 50 ... ... Ammonia measuring means, 50A ......... First ammonia measuring means, 50B ......... Second ammonia measuring means, 60,600 ......... Aeration means, 60A ......... First aeration means, 60B ......... Second Aeration means 62... Aeration tube 64 64 Aeration pump 70 70A, 70B ... Control means, 80 ... Aeration tank, 81 ... Pump, 82 ... Extraction pipe, 83 ... Valve, 84 ... Pipe, 85 ... Valve, 86 ... Piping, 90 ......... Return pipe, 92 ......... Valve, 94 ......... Pump, 96 ......... Methane aeration tank.

Claims (11)

A wastewater treatment method for ammonia wastewater using a nitrification carrier on which ammonia-oxidizing bacteria and nitrite-oxidizing bacteria are immobilized,
A nitrite oxidation step of oxidizing the ammoniacal wastewater in the nitrification tank to nitrite with the ammonia oxidizing bacteria;
Measuring either one of nitrate nitrogen concentration or nitrite nitrogen concentration in the ammoniacal wastewater;
Stopping the supply of the ammoniacal wastewater to the nitrification tank before the nitrate nitrogen concentration rises or the nitrite nitrogen concentration decreases;
An aeration process for aeration treatment of the nitrification carrier in the ammoniacal wastewater;
A wastewater treatment method comprising:   2. The wastewater treatment method according to claim 1, wherein the aeration step is performed 20 to 140 days after the start of the nitrite oxidation step, and the aeration time is performed for 12 to 24 hours.   The wastewater treatment method according to claim 1 or 2, wherein the aeration step comprises aeration of methane into the ammoniacal wastewater.   The wastewater treatment method according to claim 3, wherein the methane is supplied in a molar amount that is at least equivalent to denitrogenated nitrogen. A nitrification carrier in which ammonia-oxidizing bacteria and nitrite-oxidizing bacteria are immobilized to nitrify ammoniacal wastewater;
A nitrification tank for performing nitrification reaction of ammonia waste water using the nitrification carrier;
Ammonia measuring means for measuring either nitrate nitrogen concentration or nitrite nitrogen concentration in the ammoniacal wastewater;
Aeration means for aeration treatment of the nitrification carrier in the ammoniacal wastewater;
Based on the measured value of the ammonia measuring means, the supply of the ammonia waste water to the nitrification tank is stopped before the nitrate nitrogen concentration increases or the nitrite nitrogen concentration decreases, and the nitrification carrier is aerated. Control means for performing processing;
A wastewater treatment apparatus characterized by comprising:   The waste water treatment apparatus according to claim 5, wherein the aeration means is 20 to 140 days after the start of the nitrite oxidation step, and the aeration time is 12 to 24 hours. The nitrification tank consists of first and second nitrification tanks connected in parallel with the ammonia waste water reservoir,
A valve for controlling the supply of the ammoniacal waste water between the water storage tank and the first and second nitrification tanks;
The control means supplies the ammonia waste water to the second nitrification tank and stops the nitrite nitrification step while the supply of the ammonia waste water to the first nitrification tank is stopped and the nitrification carrier is aerated. The wastewater treatment apparatus according to claim 5 or 6, wherein a signal for switching control for performing the control is transmitted to the valve.   The waste water treatment apparatus according to any one of claims 5 to 7, wherein the aeration means aerates methane into the ammoniacal waste water.   The wastewater treatment apparatus according to claim 8, wherein the methane supplies a molar amount that is at least equivalent to denitrogenated nitrogen.   The waste water treatment apparatus according to claim 5 or 6, wherein the nitrification tank includes an aeration tank that collects a part of the nitrification carrier in the tank and performs an aeration treatment and then returns the aeration tank. The aeration tank includes a methane aeration tank for dissolving methane in the treated water discharged from the nitrification tank,
The wastewater treatment apparatus according to claim 10, wherein the methane aeration tank supplies methane-dissolved treated water to the aeration tank.

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