JP2013081945A - Waste water processor and waste water processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain the quality of water in a reaction tank for UASB processing to keep the water in a condition where the reactivity of microorganisms is enhanced.SOLUTION: A waste water processor 1 includes a reaction tank 10 which supplies to-be-processed water from a bottom 100 to cause a microbial mass to come in contact with the to-be-processed water and then discharges it from the upper part of the reaction tank 10 as processed water, and a pH adjusting tank 18 which adjusts the pH of part of processed water flowing out of the reaction tank 10. The pH adjusting tank 18 is connected to the side face of the reaction tank 10 via a return pipe 181b or return pipe 181c. Part of processed water discharged out of the reaction tank 10 is adjusted in pH so that the pH of the processed water stays within a pH range in which the reactivity of the microbial mass is enhanced. The processed water with an adjusted pH is injected into a bed 19 in the reaction tank 10, which bed 19 is a place separated from the processed water supply portion 100 in the direction of distribution of processed water.

Description

  The present invention relates to a wastewater treatment technique using a flowable microbial mass (granule which is a self-granulating sludge composed of microorganisms or a microbial film containing a substance serving as a nucleus).

  The Upflow Anaerobic Sludge Bed (UASB) method supplies treated water from the bottom of a reaction tank filled with microbial mass, and is included in the treated water under the upward water flow generated by this supply. In which organic substances and nitrogen compounds are brought into contact with microbial masses and decomposed by metabolic reactions of microorganisms (for example, Patent Documents 1 to 4).

  The UASB method is characterized by the fact that it does not require a filler as a microbial carrier and can handle a very high load by using a densely aggregated microbial mass. The microbial mass corresponds to a microbial membrane containing a substance called a granule or a nucleus that is self-granulated. Many microbial masses, such as granules and nucleated microbial membranes, have excellent sedimentation properties. When treated water is supplied from the bottom of the reaction tank, there are few floating microbial masses at the top of the reaction tank at an appropriate upward flow rate. Many microbial masses settle and stay below the tank, forming a state called a sludge bed (bed).

In the case of ammonia-containing wastewater, there are a nitrification treatment in which ammonia is oxidized to nitric acid by an aerobic bacterium in the previous stage, and a denitrification treatment in which the nitric acid is reduced to nitrogen gas by using organic substances by anaerobic heterotrophic bacteria. In recent years, anaerobic ammonia oxidizing (commonly known as anammox) bacteria that can be denitrified from ammonia and nitrous acid have attracted attention, and the UASB method is also applied in this method. In the case of using anammox bacteria, by nitrifying ammonia to about half amount of nitrous acid in the former stage, denitrification treatment by the latter stage anammox bacteria is possible, and the aeration power required for the aerobic treatment is greatly reduced. Further, since the latter stage of anammox reaction is based on autotrophic bacteria, the organic matter required for denitrification by heterotrophic bacteria is not required. As a result, it is a very excellent nitrogen treatment system, such as eliminating the need to supply organic matter that was required for wastewater with a low C / N ratio. Although the nitrogen load applicable in the anammox reactor varies depending on the process, it has been reported in the verification test to be 2.8 to 5.4 kg-N / m ³ / day (for example, Non-Patent Document 2).

  In the UASB method, the water quality in the reaction tank (such as the pH of the water to be treated and the concentration of reactants) is controlled so that the microorganisms in the reaction tank maintain a high activity. For example, in Patent Document 1, anammox bacteria are deactivated or reduced in activity due to a local increase in nitrite nitrogen concentration in the treated water injection part by stirring the vicinity of the treated water injection point in the reaction tank. Is preventing. Moreover, in patent document 2, multiple inflow points of the to-be-processed water containing nitrite nitrogen are provided in the height direction of a reaction tank, and the nitrite nitrogen injection density | concentration in the lowest stage (uppermost stream) is 300 mg-N / L. By making it below, the inactivation or the activity reduction of the anammox bacteria resulting from the local increase in nitrite nitrogen concentration in the treated water injection part is prevented.

Japanese Patent Laid-Open No. 2003-033795 JP 2003-033793 A JP-A-62-279891 JP-A-9-225491

Yasuhiro Fukuzaki, 5 others, “High-speed treatment technology of high-concentration nitrogen wastewater by anammox reaction”, Water and wastewater, Industrial Water Research Committee, September 2010, Vol. 52, No. 9, p. 719-727 Report on Evaluation of Nitrogen Removal Technology Using Anammox Reaction, Japan Sewerage Corporation Technical Evaluation Committee, March 2010

  However, when the water quality in the reaction tank cannot be avoided by injecting water to be treated (or mixed water of the water to be treated and dilution water) (for example, an increase in pH accompanying the progress of microbial reaction treatment). There is a possibility that the water quality of the reaction tank cannot be maintained in a state in which the microorganisms are highly active simply by dispersing and supplying the water to be treated into the reaction tank. For example, Patent Document 2 discloses that anammox bacterium activity inhibition occurs from a nitrite nitrogen concentration of about 50 to 200 mg / L, and the higher the concentration, the greater the inhibitory action. When the concentration of water becomes high, it is difficult to eliminate the factor that inhibits the activity of anammox bacteria simply by changing the water to be treated to dispersed input.

  Moreover, if the dilution water mixed with the water to be treated is increased in order to maintain the water quality in the reaction tank in a state in which the microorganisms are highly active, the injection of the dilution water is costly, or the dilution water to the reaction tank Water flow increases. When the flow rate of the dilution water to the reaction tank increases, the water flow rate is limited in the reaction tank, and the load may be limited. Furthermore, when dissolved oxygen concentration above a certain level exists in the dilution water, the anaerobic atmosphere in the reaction tank may be destroyed. Therefore, when injecting dilution water, dissolved oxygen is brought into the reaction tank. You must be careful enough.

  Therefore, in order to perform an efficient and stable anaerobic ammonia oxidation treatment, it is necessary to devise an environment that would inhibit the activity of anammox bacteria. At the same time, it is necessary to maintain highly active anammox bacteria in the reaction tank and to involve more anammox bacteria in the treatment reaction.

  Therefore, the wastewater treatment apparatus of the present invention and the wastewater treatment method using this apparatus are the UASB type reaction tank, the pH of the treated water treated in this reaction tank, and the microorganisms held in the reaction tank carry out the nitrogen removal reaction. The pH is adjusted to a pH suitable for carrying out at a high activity, and the pH-adjusted treated water is injected into the bed of the reaction tank, and the pH in the bed is suitable for maintaining the reaction activity of the microorganisms forming the microbial mass. It is characterized by controlling to become.

  That is, the wastewater treatment apparatus of the present invention that solves the above problems is a wastewater treatment apparatus that decomposes nitrogen compounds in the water to be treated by bringing the water to be treated into contact with microorganisms under an ascending water flow. A reaction tank in which water is supplied from the bottom and brought into contact with the microorganisms and then discharged from the top as treated water, and a part of the treated water discharged from the reaction tank has a pH range in which the reaction activity of the microorganisms becomes high. PH adjustment tank to be adjusted and a bed in the reaction tank, the pH adjusted in the pH adjustment tank at a location away from the treated water supply unit in the flow direction of the treated water And a path for injecting water.

  Further, the wastewater treatment apparatus of the present invention injects the pH-adjusted treated water so that the pH-adjusted treated water is injected into a portion of 50% or less of the bed height in the wastewater treatment apparatus. It is characterized by having a route to perform.

  Moreover, the wastewater treatment apparatus of the present invention is characterized in that, in the wastewater treatment apparatus, the pH-adjusted treated water is injected without being mixed with the treated water.

  The wastewater treatment apparatus of the present invention is characterized in that, in the wastewater treatment apparatus, a plurality of paths for injecting the pH-adjusted treated water are provided with respect to a flow direction of the treated water in the reaction tank. It is said.

  Moreover, the wastewater treatment apparatus of the present invention that solves the above-mentioned problems is a wastewater treatment apparatus that decomposes nitrogen compounds in the water to be treated by bringing the water to be treated into contact with microorganisms under an ascending water flow. A reaction tank for supplying water from the bottom and bringing it into contact with the microorganism and then discharging it from the top as treated water, and a pH range in which a part of the treated water discharged from the reaction tank has a higher reaction activity of the microorganism, A pH adjusting tank to be adjusted, a bubble separating member provided in the reaction tank, for separating bubbles generated by a reaction between the microorganisms and the water to be treated and the microorganisms, and the bubble separation A path for injecting the treated water pH-adjusted in the pH-adjusting tank at a location below the member and spaced apart from the treated-water supply unit in the flow direction of the treated water. It is a feature.

  In addition, the wastewater treatment method of the present invention that solves the above-described problems includes a reaction tank in which the water to be treated and microorganisms are brought into contact with each other, and the pH of the treated water that has been treated in the reaction tank has a high reaction activity of the microorganisms. A wastewater treatment method using a wastewater treatment apparatus comprising a pH adjustment tank that is adjusted to be in a pH range, wherein the treated water is supplied from the bottom of the reaction tank, and the treated water is supplied to the microorganism. After being brought into contact with water, it is discharged from the upper part of the reaction tank as treated water, and a part of the discharged treated water is adjusted in the pH adjusting tank so as to be in a pH range in which the reaction activity of the microorganism is increased, In the reaction tank bed, the pH-adjusted treated water is injected into a location separated from the treated water supply unit in the flow direction of the treated water.

  Moreover, the wastewater treatment method of the present invention that solves the above-mentioned problems is provided by a reaction between the water to be treated and the microorganisms in contact with each other, and the reaction between the microorganisms and the water to be treated. PH adjusting tank for adjusting a part of the treated water after being treated in the reaction tank to be in a pH range in which the reaction activity of the microorganism becomes high And a wastewater treatment method using a wastewater treatment apparatus comprising: supplying the treated water from the bottom of the reaction tank; and bringing the treated water into contact with the microorganisms and then treating the treated water as treated water. A part of the discharged treated water is adjusted in the pH adjusting tank so as to be in a pH range in which the reaction activity of the microorganism is high, and is below the bubble separation member and is to be treated The treated water from the water supply unit In spaced locations in the flow direction, it is characterized by injecting the treated water that has been pH adjusted by the pH adjustment tank.

  According to the above invention, the activity of microbial mass can be maintained and it can contribute to the high load of UASB process.

It is the schematic block diagram which showed the wastewater treatment system which concerns on the reference example of invention. It is a figure which shows the pH change of the to-be-processed water of the height direction of the reaction tank of the wastewater treatment system which concerns on the reference example of invention. It is the schematic block diagram which showed the waste water treatment apparatus which concerns on Embodiment 1 of invention. (A) The figure which shows the relationship between the height (H) of a reaction tank when not injecting pH adjusted treated water from the side surface of a reaction tank, and the pH value in a reaction tank, (b) pH adjusted treated water It is a figure which shows the relationship between the height (H) of the reaction tank at the time of inject | pouring from the side surface of a reaction tank, and the pH value in a reaction tank. It is the schematic block diagram which showed the waste water treatment apparatus which concerns on Embodiment 2 of invention.

[Reference example]
Prior to the present invention, the inventors inoculated anammox bacteria in the reaction tank 50 in the wastewater treatment apparatus 5 shown in FIG. 1 as a reference example, and reacted ammonia nitrogen and nitrite nitrogen. And the pH change of the height direction of this reaction tank 50 was measured.

(Device configuration)
As shown in FIG. 1, the reaction processing apparatus 5 according to the reference example includes a pH adjusting tank 18, a reaction tank 50, and a bubble collecting tube 12.

  An artificial wastewater tank 51 described later was connected to the bottom 500 of the reaction tank 50 via a supply pipe 101. And to-be-processed water was supplied from the bottom part 500 of the reaction tank 50, and after making it contact with the bed 19 in the reaction tank 50, it was discharged | emitted from the upper part as treated water. The water to be treated was supplied by the pump P <b> 1 through the supply pipe 101 connected to the lower end of the reaction tank 50. As shown in FIG. 1, the reaction vessel 50 was formed in a cylindrical shape. Further, the inner peripheral surface of the reaction tank 50 in the vicinity of the bottom 500 is formed in a tapered shape so that the microbial mass can be easily collected on the bottom and the contact efficiency with the water to be treated can be improved.

  Furthermore, a circulation pipe 172 for returning a part of the treated water to the reaction tank 50 is provided on the upper side surface of the reaction tank 50. A plurality of water sampling tubes 7 a to 7 f were provided on the side surface of the reaction tank 50 in the height direction of the reaction tank 50.

  The bubble collection tube 12 is configured by a collection cone 121 formed in a Jinkasa shape and a cylindrical portion 122 connected vertically to the upper end opening of the collection cone 121. Arranged coaxially with the tank. The bubble collecting tube 12 collected bubbles generated from the bed 19 and discharged them into the atmosphere via the cylindrical portion 122 connected to the ceiling portion of the reaction tank 50.

The pH adjustment tank 18 was provided via the reaction tank 50 and the circulation pipe 172, and part of the treated water was transferred to the pH adjustment tank 18 via the circulation pipe 172. Furthermore, the pH adjustment tank 18 was provided with a pH meter 18a, and the pH of the treated water was adjusted to a predetermined pH with 0.5 M H ₂ SO ₄ in the pH adjustment tank 18. Then, the treated water whose pH was adjusted by the pump P2 was circulated through the reaction tank 50 again through the circulation pipe 181.

  The artificial wastewater tank 51 was connected to the bottom 500 of the reaction tank 50 via the supply pipe 101. The artificial wastewater tank 51 was provided with a dissolved oxygen concentration (DO) meter 51a and a pH meter 51b. And the to-be-processed water of the artificial wastewater tank 51 was supplied to the reaction tank 50 with the pump P1 through the supply pipe | tube 101. FIG. In the reference example, the artificial wastewater tank 51 is preliminarily provided with treated water adjusted to the composition shown in Table 1, and nitrogen gas is used so that the dissolved oxygen concentration of the treated water is 0.5 mg / L or less. Was degassed.

In the wastewater treatment apparatus 5 having the above-described configuration, the nitrogen volume load (NLR) is set to 7.0 kg-N / m ³ / day in order to investigate the pH characteristics of the water to be treated flowing in the reaction tank 50 in the high load operation. As described above, ammonia nitrogen and nitrite nitrogen were reacted in the presence of anammox bacteria. And the to-be-processed water was extract | collected from the water sampling pipes 7a-7f, and pH of the extract | collected to-be-processed water was measured. FIG. 2 shows the pH change of the water to be treated in the height direction of the reaction tank 50 during the anammox reaction.

For the reaction by anammox bacteria, the reaction formula shown by the following formula (1) has been proposed.
1.0NH ₄ ⁺ + 1.32NO ₂ ⁻ + 0.066HCO ₃ ⁻ + 0.13H ⁺ →
1.02N ₂ + 0.26NO ₃ ⁻ + 0.066CH ₂ O _0.5 N _0.15 + 2.03H ₂ O (1)
According to the equation (1), as the anammox reaction proceeds, H ^{+ in the} water to be treated is consumed, so that the water to be treated at the top of the reaction tank 50 has a higher pH as shown in FIG. ing. This pH change becomes significant when the pH buffering property of the water to be treated flowing into the reaction tank 50 is low.

  In FIG. 2, the pH of the water to be treated in the reaction tank 50 is pH 7.5 at the inflow portion 500 at the bottom of the reaction tank 50, but at a position 180 mm higher than the bottom of the reaction tank 50 (about the bed height). The water to be treated collected by the water collection pipe 7a at 50% is already pH 8.43, which exceeds the pH range (pH 6.5 to 8.0) suitable for the anammox reaction. Then, the position deviating from the upper limit (pH 8.0) of the preferable pH is a position 100 mm (corresponding to 24% of the bed height) from the lowermost part of the reaction tank 50.

  Further, the pH of the water to be treated flowing through the reaction tank 50 increases gradually as it goes upward from the position of the water sampling pipe 7b. That is, when the water to be treated is introduced from the bottom 500 of the reaction tank 50, as shown in FIG. 2, the pH change occurs particularly in almost all the bed 19 region where the microbial mass exists. Then, the pH in the reaction tank 50 deviates from the upper limit of the preferred pH of the anammox bacteria in the vicinity of the upward flow side of the inflow portion 500 at the lower part of the reaction tank 50.

  From this, when the water to be treated is supplied from the bottom portion 500 of the reaction tank 50, the region where the activity of the anammox bacteria can be maintained is limited to the bed 19 portion in the vicinity of the inflow portion.

  And since the anammox bacteria existing in the part where the activity deviates from the upper limit of the preferred pH is low, the nitrogen removal performance is improved even if a large amount of anammox bacteria is retained in the bed 19 region. May not be expected. Further, since the reaction of the formula (1) proceeds faster as the high load treatment operation with the nitrogen volume load (NLR) set to be higher, the bed 19 region that changes from the inflow initial pH of the treated water supplied to the bottom portion 500. The pH change in the upward flow direction becomes faster. Then, since the bed 19 region that is affected by the inhibition of activity due to deviation from the upper limit of the preferred pH becomes wider, even if the total amount of anammox bacteria is sufficiently secured, the nitrogen removal performance in proportion to the amount of bacteria is improved. May not be expected, and conversely, the nitrogen removal performance may decrease. In addition, when this overload is caused by this inhibition, the substrate concentration remains in the treated water at a high level, so the dilution effect of the pH-adjusted treated water is lost, and the treatment may be accelerated. There is also.

  In addition, the microbial mass floating together with bubbles above the bed 19 (in the reference example, deposited up to a position near 420 mm from the bottom of the reaction tank) hardly inhibits nitrogen removal because it is inhibited by the activity due to pH. In addition, the longer the residence time at the top, the more likely the activity of anammox bacteria will decrease. Therefore, it is necessary to quickly return the microbial mass floating together with the bubbles to the inside of the bed 19, and the microbial mass collides with the collection cone 121 so that the bubbles and the microbial mass are separated, and the microorganisms from which the bubbles are separated are separated. The lump descends and returns to the bed 19.

  In view of the measurement result of the pH change in the reaction tank 50 in the wastewater treatment apparatus 5 according to the above reference example, the inventors have created the present invention. Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1]
With reference to FIG. 3 and FIG. 4, the waste water treatment apparatus 1 which concerns on Embodiment 1 of this invention, and the waste water treatment method by this apparatus are demonstrated in detail.

(Device configuration)
As shown in FIG. 3, the wastewater treatment apparatus 1 includes a reaction tank 10, a pH adjustment tank 18, and a side screen 13. Then, return pipes 181a to 181c are branched from the return pipe 181 connected to the pH adjusting tank 18.

  The reaction tank 10 is supplied with water to be treated from the bottom 100, brought into contact with a bed 19 of microbial masses deposited at the bottom of the reaction tank 10, and then discharged from the top as treated water. The bed 19 (sludge bed) is a layer formed by the microbial mass that has settled and stayed below the reaction tank 10, and the microbial mass is a substance called a granule in which microorganisms are self-granulated and forms a nucleus. Applicable to microbial membranes containing. Examples of microorganisms that form this microbial mass include anammox bacteria. The load of nitrogen compound supplied to the reaction tank 10 is determined by the volume of the bed 19, the substrate concentration of the water to be treated, the amount of water, and the like. And the microorganisms which proliferated with the continuation of a driving | running | working are regularly extracted so that the height of the bed 19 may be maintained the predetermined height suitably. Therefore, the height of the bed 19 of the reaction tank 10 is set in advance as one of the operating conditions of the reaction tank 10.

  The water to be treated is supplied by the pump P <b> 1 through the supply pipe 101 connected to the lower end of the reaction tank 10. As the water to be treated, for example, the water to be treated containing ammonia was treated with an aerobic ammonia-oxidizing bacterium in advance in a treatment tank (not shown) to convert a part of the ammonia to be treated into nitrous acid. For example, water to be treated is used. The water to be treated is not particularly limited, and for example, water to be treated containing ammonia nitrogen and nitrite nitrogen may be supplied so that the reaction shown in the formula (1) proceeds efficiently. .

  The reaction tank 10 is formed in a cylindrical shape. In addition, the inner peripheral surface of the reaction tank 10 near the bottom 100 is formed in a tapered shape so that the microbial mass can be easily collected on the bottom and the contact efficiency with the water to be treated can be improved. In addition to the outflow pipe 171 for flowing the treated water out of the system, a circulation pipe 172 for returning a part of the treated water to the reaction tank 10 is connected to the upper part of the reaction tank 10 in communication with the treated water separation chamber 17. ing. A pH adjustment tank 18 for adjusting the pH of the treated water transferred from the treated water separation chamber 17 is connected to the circulation pipe 172.

  The liquid phase in the reaction vessel 10 may have a pH exceeding 8.5 due to the reaction shown in the formula (1), which may reduce the activity of the microbial mass. Therefore, the pH of the treated water is adjusted to be near neutral (for example, pH 7.1 to 7.4) in the pH adjusting tank 18, and the treated water whose pH has been adjusted is returned to the reaction tank 10. Stabilize microbial mass activity.

  The pH adjustment tank 18 is connected to the bottom 100 of the reaction tank 10 via a return pipe 181 a and a supply pipe 101, and the water to be treated supplied from the supply pipe 101 is treated water whose pH is adjusted in the pH adjustment tank 18. Diluted by The pH adjustment tank 18 is connected to the side surface of the reaction tank 10 via a return pipe 181b or 181c, and injects pH-adjusted treated water into the vicinity of the lower portion of the bed 19 of the reaction tank 10. The pH adjustment tank 18 includes a pump for injecting a chemical solution for pH adjustment and a stirrer for stirring the treated water. A well-known chemical | medical agent (a sulfuric acid, hydrochloric acid, etc.) applied to water treatment technology should just be applied for a chemical | medical solution. Note that a plurality of return pipes 181b and 181c are provided in the flow direction of the water to be treated flowing through the reaction tank 10 (that is, the height direction of the reaction tank 10), and the pH is adjusted according to the treatment state of the reaction tank 10. Water injection may be controlled.

  The injection point for injecting the pH-adjusted treated water is not particularly limited as long as the bed 19 is deposited in the reaction tank 10. Since the water to be treated supplied from the supply pipe 101 is adjusted to have a pH range in which the activity of the anammox reaction is high, an injection point for injecting the pH-adjusted treated water is supplied from the supply pipe 101. Provided at locations separated in the direction of treatment water flow. Moreover, the injection point of the pH-adjusted treatment water is not limited to providing the injection point on the side surface of the reaction tank 10 as long as the pH-adjusted treatment water can be injected into the bed 19. As shown in the reference example, the height is 180 mm (corresponding to about 50% of the height of the bed 19) from the lowermost part of the reaction tank 50, and deviates from the upper limit of suitable pH (pH 8.0) for the activity of anammox bacteria. ing. Therefore, when the injection point of the pH-adjusted treated water into the reaction tank 10 is set to be 50% or less of the height of the bed 19 in the reaction tank 10, the quality of the treated water flowing through the bed 19 is determined. The activity of anammox bacteria can be maintained or restored to a high state.

  The side screen 13 separates the liquid phase containing the microbial mass in the upper layer of the reaction tank 10 into the microbial mass and the water to be treated. The side screen 13 is formed of a slit-like or lattice-like screen such as a wedge wire screen formed in a cylindrical shape. The mesh width of the screen is set to be smaller than the average particle diameter of the microbial mass so as to be suitable for solid-liquid separation between the microbial mass and the water to be treated. The side screen 13 is formed in a cylindrical shape having the same diameter as the reaction vessel 10 and is installed on the peripheral side surface near the upper end of the reaction vessel 10. A treated water separation chamber 17 in which treated water is transferred via the side screen 13 is provided on the outer periphery near the upper end. If the inner surface of the reaction vessel 10 above the side screen 13 immersed in the liquid phase is made into a slit-like or lattice-like screen such as a wedge wire, the floating microorganism mass is pushed out to the outflow side by the flow of water to be treated. It becomes easy to block the side screen 13. Therefore, it is desirable that the inner surface portion of the reaction vessel 10 above the side screen 13 does not have water permeability.

(Explanation of operation example)
An example of the operation of the wastewater treatment apparatus 1 will be described with reference to FIG.

  The water to be treated is supplied into the reaction tank 10 from the bottom 100 via the supply pipe 101 by the pump P1. When the water to be treated is supplied into the reaction tank 10, the nitrogen compounds in the water to be treated are decomposed by the microbial mass constituting the bed 19. For example, nitrous acid and ammonia components contained in the water to be treated are converted into nitrogen gas by a denitrification reaction by an anammox bacterium which is one of the bacteria constituting the microbial mass exemplified in the formula (1). Nitrogen gas generated from the microbial mass rises toward the liquid level in the reaction tank 10 by the upward water flow. In addition, the microbial mass near the bottom 100 where the biological activity is the highest has a strong gas generation and may lose its sedimentation property due to adhesion of bubbles of the gas. When the microbial mass to which the bubbles are attached rises, it is detached from the microbial mass to which the bubbles have adhered by the action of the flow received from the upward flow, and the microbial mass from which the bubbles have partly settled is settled by its own weight. Return to 19. In this process, the microbial mass that does not separate from the bubbles and the bubbles separated from the microbial mass ascend the reaction tank 10 and move to the vicinity of the liquid level. When the rising bubbles reach the liquid level, they are released as gas into the gas phase in the reaction tank 10 and discharged from the exhaust pipe 103 to the outside of the system. Further, the microbial mass separated from the bubbles when floating on the liquid surface descends by its own weight and settles toward the bed 19. Even in this region of the reaction tank 10, the microbial mass to which bubbles still adhere comes into contact with the side screen 13 by riding on the flow of treated water flowing out of the system via the side screen 13. The bubbles are released from the gas, the gas is released into the gas phase, and the microbial mass separated from the bubbles descends by its own weight and settles toward the bed 19.

  The water to be treated that has risen to the upper layer near the liquid level in the reaction tank 10 is separated into solid and liquid by the side screen 13 and then discharged out of the system from the outflow pipe 171 of the treated water separation chamber 17.

  In the pH adjusting tank 18, a pH adjusting agent such as an acid is added to the treated water flowing out from the treated water separation chamber 17 so that the treated water has a pH range in which the reaction activity of the microbial mass is increased. adjust. Specifically, the pH is adjusted so that the pH of the treated water is around neutral (pH 7.1 to 7.4). The pH-adjusted treated water is injected from the return pipe 181 into the vicinity of the lower part of the bed 19 of the reaction tank 10 by the pump P2 through the return pipes 181b and 181c. As a result, the pH of the liquid phase environment of the reaction vessel 10 can be adjusted to a pH range (for example, about pH 7.5 or less) in which the biological activity of the microorganism mass can be maintained. In order to dilute the substrate concentration of the water to be treated, a part of the treated water is supplied to the pH adjustment system via the circulation pipe 172 and then circulated and supplied to the supply pipe 101 via the return pipe 181a.

(effect)
According to the wastewater treatment apparatus 1, by adjusting the pH-adjusted treated water to the bed 19 of the reaction tank 10, the water quality of the bed 19 is adjusted so that the water quality can be maintained in a state where the activity of anammox bacteria is high. Can do.

  That is, by injecting the pH-adjusted treated water into the vicinity of the lower part of the bed 19 of the reaction tank 10, the pH increased by the biological treatment is lowered, and the treated water supplied to the reaction tank 10 and the anammox reaction are generated. The reaction products can be diluted simultaneously. Further, by diluting the water to be treated supplied to the reaction tank 10 by returning the pH-adjusted treated water, a high concentration substrate that inhibits the biological activity of the microbial mass can be obtained at a concentration level that does not inhibit the activity of the microbial mass. And the anaerobic biological activity of the bed 19 can be maintained. As a result, it is possible to widen the region where the activity of the microbial mass can be maintained, so that wastewater treatment can be performed with a high load. Moreover, since the volume of the reaction tank 10 can be used effectively, the reaction tank 10 can be downsized.

  Furthermore, since the pH-adjusted treated water returned to the reaction tank 10 is treated water that circulates through the reaction tank 10, the dissolved oxygen concentration is low. Therefore, the influence of dissolved oxygen on the anammox bacteria can be reduced by using treated water for the return water for adjusting the pH of the bed 19. Note that the pH-adjusted water injected from the return pipes 181b and 181c is not limited to returning the pH-adjusted treated water as in the embodiment. If the pH-adjusted solution is injected, the pH-adjusted water is injected. An effect can be obtained.

  Further, when a plurality of return pipes for injecting the pH-adjusted treated water are provided in the height direction of the reaction tank 10 and each return pipe is provided with a valve (not shown), the reaction tank can be adjusted by adjusting the valve. PH adjustment and dilution of water to be treated can be performed according to changes in biological reaction at 10 (changes in pH and substrate concentration in the height direction of the reaction tank 10).

As shown in FIG. 4A, when the wastewater treatment apparatus 1 is operated with a high nitrogen volume load such as a nitrogen volume load (NLR) of 7 kg-N / m ³ / day, the pH-adjusted treated water is not injected. Then, the pH of the water to be treated in the reaction tank 10 has already risen to pH 8.5 near the middle of the reaction tank 10. As described above, when the pH of the water to be treated flowing in the reaction tank 10 is increased, the activity of the microbial mass may be inhibited. On the other hand, the wastewater treatment apparatus 1 according to the embodiment of the present invention allows the reaction in the reaction tank 10 to react as shown in FIG. 4B by injecting the pH-adjusted treated water from the side surface of the reaction tank 10. It can be seen that the accompanying increase in pH is suppressed. In FIG. 4 (b), the pH-adjusted treated water is injected into the bed 19 in the reaction tank 10, which is 50% or less of the height of the bed 19. As shown in FIG. 4 (a), even in an environment where the pH in the reaction vessel 10 deviates from 8.0 and the nitrogen removal reaction by the anammox bacteria does not proceed due to pH inhibition, It is shown that the anammox reaction can be advanced again by adjusting the pH. That is, when the pH-adjusted treated water is injected into the bed 19 located at 50% or less of the bed 19 height in the reaction tank 10, in a treatment operation such as when the high nitrogen load or the pH buffering property of the treated water is low. Thus, it is possible to effectively maintain and recover the pH within a suitable pH range. As a result, since the effective area of the bed 19 formed by sedimentation of the microbial mass (area where the activity of the bed 19 in the reaction tank 10 can be maintained) can be widened, when wastewater treatment is performed at a high load. In addition, the anaerobic wastewater treatment can be performed while maintaining the activity of the microbial mass at a high level.

[Embodiment 2]
With reference to FIG. 5, the waste water treatment apparatus 2 which concerns on Embodiment 2 of this invention, and the waste water treatment method by this apparatus are demonstrated in detail.

  The wastewater treatment apparatus 2 according to Embodiment 2 shown in FIG. 5 is provided with a bubble separation member that separates the gas generated by the contact reaction between the microorganism and the water to be treated in the reaction tank 10 and the microorganism. The configuration is the same as that of the wastewater treatment apparatus 1 according to the first embodiment. Therefore, about the structure similar to the waste water treatment apparatus 1 which concerns on Embodiment 1, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

(Device configuration)
The wastewater treatment apparatus 2 includes a reaction tank 10, a pH adjustment tank 18, a bubble separation screen 11, and a side screen 13. Then, return pipes 181a to 181c are branched from the return pipe 181 connected to the pH adjusting tank 18.

  The bubble separation screen 11 comes into contact with the microbial mass to which gas bubbles generated as a result of the microbial reaction are attached from the bed 19 staying near the bottom 100 of the reaction tank 10 to separate the bubbles from the microbial mass. The bubble separation screen 11 is formed of a slit-like or lattice-like screen such as a wedge wire screen formed in a camp shape.

  In the wastewater treatment apparatus 2 according to the second embodiment, the return pipes 181b and 181c are provided on the side surface of the reaction tank 10 so as to inject the treated water whose pH is adjusted into the treated water below the bubble separation screen 11.

(Explanation of operation example)
An example of the operation of the wastewater treatment apparatus 2 will be described with reference to FIG.

  The water to be treated is supplied into the reaction tank 10 from the bottom 100 via the supply pipe 101 by the pump P1. When the water to be treated is supplied into the reaction tank 10, the nitrogen compounds in the water to be treated are decomposed by the microbial mass constituting the bed 19. For example, nitrous acid and ammonia components contained in the water to be treated are converted into nitrogen gas by a denitrification reaction by anammox bacteria, which is one of the bacteria constituting the microbial mass. Bubbles such as nitrogen gas generated from the microbial mass rise toward the liquid level in the reaction tank 10 by the upward water flow. In addition, the microbial mass near the bottom 100 where the biological activity is the highest has a strong gas generation and may lose its sedimentation property due to adhesion of bubbles of the gas.

  The microbial mass to which the bubbles are attached is quickly desorbed by contact with the bubble separation screen 11 installed in the bed 19. For this reason, since the microbial mass from which the bubbles are detached easily stays in the vicinity of the bottom portion 100, the accumulation degree of the microbial mass in the bed 19 can be increased. On the other hand, the water to be treated which has been treated by the bed 19 is solid-liquid separated by the bubble separation screen 11, and then moves on the upward flow toward the upper layer of the reaction tank 10.

  Further, when the microbial mass to which bubbles are attached rides on the flow of treated water flowing out of the system through the side screen 13 and comes into contact with the side screen 13, the bubbles are detached from a part of the microbial mass and the gas is removed. Released in the phase, the microbial mass settles towards the bed 19.

  The water to be treated that has risen to the upper layer near the liquid level in the reaction tank 10 is separated into solid and liquid by the side screen 13 and then discharged out of the system from the outflow pipe 171 of the treated water separation chamber 17. Further, part of the treated water in the treated water separation chamber 17 is transferred to the pH adjusting tank 18 through the circulation pipe 172.

  In the pH adjustment tank 18, the pH of the treated water is adjusted to near neutrality (pH 7.1 to 7.4) by adding a pH adjusting agent such as an acid to the treated water flowing out from the treated water separation chamber 17. To do. The pH-adjusted treated water is supplied from the return pipe 181 to the lower side of the bubble separation screen 11 of the reaction tank 10 by the pump P2 through the return pipes 181b and 181c. As a result, the pH of the liquid phase environment of the reaction vessel 10 can be adjusted to a pH range (for example, about pH 7.5 or less) in which the biological activity of the microorganism mass can be maintained. In addition, in order to dilute the substrate concentration of to-be-processed water, a part of treated water is circulated and supplied to the supply pipe | tube 101 via the return pipe | tube 181a, after adjusting pH in the pH adjustment tank 18. FIG.

(effect)
According to the wastewater treatment apparatus 2, air bubbles can be separated from the floating microbial mass, and the water quality in the height direction of the reaction tank 10 in the bed 19 can be adjusted to a water quality that allows the microorganisms to maintain high activity. Moreover, in addition to the effect of the wastewater treatment apparatus 1 according to Embodiment 1 of the present invention, by providing the injection location of the pH-adjusted treatment water in the arrangement location of the bubble separation screen 11 provided in the reaction vessel 10, To prevent the microbial mass from adhering to the bubble separation screen 11 due to the water flow at the time of injection of the pH-adjusted treated water, and to promote the separation of the air bubbles adhering to the microbial mass, thereby increasing the degree of accumulation of the microbial mass in the bed 19 Can do.

  Moreover, in the reaction tank 10, the water quality of the bed 19 and the to-be-processed water may change according to reaction conditions and reaction processing time. In the wastewater treatment apparatus 2 according to Embodiment 2 of the present invention, the microbial activity of the reaction tank 10 is achieved regardless of the height of the bed 19 by injecting the pH-adjusted treated water into a position corresponding to the bubble separation screen 11. Can be controlled to a high state. That is, when the bed 19 is deposited below the bubble separation screen 11, the pH between the bed 19 and the bubble screen 11 is controlled so that the activity of the microorganism mass is not inhibited, so that It is returned to the bed 19 again while maintaining the activity. Therefore, the growth of the bed 19 can be promoted. Further, when the bubble separation screen 11 is embedded in the bed 19, the water quality in the region where the microbial reaction is active can be obtained by injecting treated water adjusted in pH into the bed 19 in which bubbles are generated. Can be controlled to maintain a high activity.

  If the return pipes 181b and 181c are provided so that the pH-adjusted treated water directly hits the bubble separation screen 11, the microbial mass attached to the bubble separation screen 11 is peeled off due to the water pressure of the pH-adjusted treated water. Can do.

  As described above with reference to Embodiments 1 and 2, according to the wastewater treatment apparatus and the wastewater treatment method of the present invention, the pH-adjusted treated water is injected into the vicinity of the lower part of the bed, thereby The increase in pH of the water is suppressed, and the substrate (or reaction product) of the water to be treated can be sufficiently diluted. In other words, while suppressing the increase in pH of the treated water accompanying the progress of the anammox reaction, and the substrate concentration in the treated water increases to a concentration that may inhibit the activity of anammox bacteria, It can be controlled to relax. Therefore, the reaction activity of the microbial mass in the reaction tank can be maintained at a high level.

  The wastewater treatment apparatus and the wastewater treatment method according to the present invention are not limited to the above-described embodiment, and can be appropriately changed in design as long as the effects are not impaired. For example, the shape of the reaction vessel is not limited to a cylindrical shape, and may be a rectangular tube shape such as a rectangular cross section and a polygonal shape. Furthermore, the shape of the bubble separation screen is not limited to the shape formed in the Jinkasa shape, and if the surface of the bubble separation screen is inclined with respect to the horizontal, the reaction vessel has a rectangular tube with a rectangular cross section. In the case of a shape, it may be formed in a plate shape having an inclination with respect to the horizontal extending in the longitudinal direction of the reaction vessel.

Moreover, although the embodiment illustrated and demonstrated the form which performs a denitrification process with an anammox bacterium, the waste water treatment apparatus of this invention and the denitrification process by the anaerobic heterotrophic bacteria (denitrification bacteria) currently implemented conventionally and Even if the wastewater treatment method is applied, the same effect can be obtained. That is, the pH range in which the heterotrophic bacteria can maintain high activity is near neutral pH, and the reaction by denitrifying bacteria occurs as shown in the following formulas (2) and (3). The pH of the water is thought to increase.
NO ₂ ⁻ + 3H ⁺ → 1 / 2N ₂ + H ₂ O + OH ⁻ (2)
NO ₃ ⁻ + 5H ⁺ → 1 / 2N ₂ + 2H ₂ O + OH ⁻ (3)
Therefore, by adjusting the pH of the treated water and supplying it to the bed, the quality of the treated water can be controlled so that the pH of the heterotrophic bacteria becomes high. As a result, the activity of heterotrophic bacteria can be maintained and UASB treatment can be performed with a high load.

1, 2, 5 ... Waste water treatment device 10, 50 ... Reaction tank 11 ... Bubble separation screen (bubble separation member)
13 ... Side screen 18 ... pH adjustment tank 19 ... Bed (deposited layer of microorganisms)
181, 181 a to 181 c ... return pipe

Claims (7)

A wastewater treatment apparatus for decomposing nitrogen compounds in water to be treated by bringing the water to be treated into contact with microorganisms under a rising water flow,
A reaction vessel for supplying the water to be treated from the bottom and contacting it with the microorganisms and then discharging the treated water from the top;
A pH adjusting tank for adjusting a part of the treated water discharged from the reaction tank to be in a pH range in which the reaction activity of the microorganism is high;
The treated water adjusted in the pH adjusting tank is injected into a place where the treated water is accumulated in the reaction tank, and is separated from the treated water supply unit in the flow direction of the treated water. A wastewater treatment apparatus comprising a path. The path for injecting the pH-adjusted treated water is provided such that the pH-adjusted treated water is injected into a location that is 50% or less of the height of the microorganism deposition layer. Item 2. A wastewater treatment apparatus according to item 1. The wastewater treatment apparatus according to claim 1 or 2, wherein the pH-adjusted treated water is injected without being mixed with the treated water. The path | route which inject | pours the said pH-adjusted treated water is provided with two or more with respect to the distribution direction of the said to-be-processed water of the said reaction tank, The any one of Claims 1-3 characterized by the above-mentioned. Wastewater treatment equipment. A wastewater treatment apparatus for decomposing nitrogen compounds in water to be treated by bringing the water to be treated into contact with microorganisms under a rising water flow,
A reaction vessel for supplying the water to be treated from the bottom and contacting it with the microorganisms and then discharging the treated water from the top;
A pH adjusting tank for adjusting a part of the treated water discharged from the reaction tank to be in a pH range in which the reaction activity of the microorganism is high;
A bubble separating member provided in the reaction vessel, for separating the microorganisms from the bubbles generated by the reaction between the microorganisms and the water to be treated;
A path for injecting treated water pH-adjusted in the pH-adjusting tank into a location below the bubble separation member and spaced apart from the treated water supply unit in the flow direction of the treated water. A wastewater treatment apparatus characterized by that. A reaction tank for reacting water to be treated with microorganisms;
A pH adjusting tank for adjusting a part of the treated water after being treated in the reaction tank so as to be in a pH range in which the reaction activity of the microorganism is increased;
A wastewater treatment method using a wastewater treatment apparatus comprising:
Supplying the water to be treated from the bottom of the reaction tank, allowing the water to be treated to come into contact with the microorganisms and then discharging it from the top of the reaction tank as treated water;
In the pH adjustment tank, a part of the discharged treated water is adjusted so as to be in a pH range in which the reaction activity of the microorganism is increased,
The deposited layer of microorganisms deposited in the reaction tank, wherein the pH-adjusted treated water is injected into a place separated from the treated water supply unit in the flow direction of the treated water. Wastewater treatment method. A reaction tank for reacting water to be treated with microorganisms;
A bubble separating member provided in the reaction vessel, for separating the microorganisms from the bubbles generated by the reaction between the microorganisms and the water to be treated;
A pH adjusting tank for adjusting a part of the treated water after being treated in the reaction tank so as to be in a pH range in which the reaction activity of the microorganism is increased;
A wastewater treatment method using a wastewater treatment apparatus comprising:
Supplying the water to be treated from the bottom of the reaction tank, allowing the water to be treated to come into contact with the microorganisms and then discharging it from the top of the reaction tank as treated water;
In the pH adjustment tank, a part of the discharged treated water is adjusted so as to be in a pH range in which the reaction activity of the microorganism is increased,
The treated water whose pH is adjusted in the pH adjusting tank is injected into a location below the bubble separation member and spaced from the supply portion of the treated water in the flow direction of the treated water. Wastewater treatment method.

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