JP2011056383A - Treatment method of nitrogen containing water and treatment apparatus of nitrogen containing water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treatment method and treatment apparatus of nitrogen containing water, capable of granulating a microorganism group containing nitrifying bacteria and denitrifying bacteria in a complete mixing type tank and in a system for continuously making water to be treated flow in. <P>SOLUTION: The biological treatment method of the nitrogen containing water includes: a nitrifying process of supplying the water to be treated to a nitrifying part and oxidizing ammonium ions in the water to be treated to nitric acid or nitrous acid; and a denitrifying process of supplying the water to be treated to the denitrifying part of a complete mixing type, supplying a hydrogen donor and reducing the nitric acid or the nitrous acid in the water to be treated to a nitrogen gas. In the denitrifying process, the addition amount of the hydrogen donor is changed with time so as to change the concentration of the hydrogen donor inside the denitrifying part with time. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a nitrogen-containing water treatment method and a nitrogen-containing water treatment apparatus for biologically oxidizing and reducing ammonium ions, organic nitrogen, and the like contained in water to be treated to nitrogen gas.

  In recent years, in the field of wastewater treatment, biochemical water treatment has been frequently used in which treatment is performed by changing the pollutants in wastewater to harmless substances using the physiological activity of microorganisms. The activated sludge method is the mainstream as a general biological treatment method. However, in the normal activated sludge method, it is difficult to increase the concentration of microorganisms in the system and the load cannot be increased. It has been regarded as a problem that it is necessary, the management of organisms is difficult and processing performance such as bulking is likely to deteriorate, the need for large-scale sedimentation facilities, and the generation of waste such as excess sludge . As a technology to solve these problems, a method that performs solid-liquid separation of activated sludge using a membrane, a method that performs treatment by attaching microorganisms such as sponges and polymer carriers, and so-called granules that self-granulate microorganisms are used. A method for performing the processing has been developed. Among them, the method using granules has been attracting attention because it can retain a large amount of microorganisms in the tank, and thus has a high reaction rate per unit volume and easy solid-liquid separation.

  Similarly, in the treatment of wastewater containing nitrogen, biochemical treatment is often applied. For example, in the treatment of wastewater containing ammonium ions and organic nitrogen, (1) aerobic oxidation treatment of organic matter Or anaerobic methane fermentation treatment, (2) Ammonia oxidizing bacteria and nitrite oxidizing bacteria, etc. under aerobic conditions oxidize ammonium ions to nitrite ions and nitrate ions, and (3) hydrogen under anaerobic conditions In the presence of the donor, the nitrite ions and nitrate ions may be reduced to nitrogen gas, and (4) the excess hydrogen donor may be oxidized to carbon dioxide under aerobic conditions. . As the hydrogen donor, an organic substance or the like contained in the raw water to be treated can be used. However, when the hydrogen donor is insufficient, it is necessary to supply from the outside. At this time, the supply amount of the hydrogen donor is determined based on the nitrogen concentration in the waste water, and the hydrogen donor is continuously added based on the supply amount.

  In addition to the activated sludge method, as a biological treatment method, a treatment method in which a sponge or a gel-like carrier is added to increase the microorganism concentration and facilitate solid-liquid separation is frequently used. However, the processing speed in the method in which the carrier is added is about 0.3 to 0.5 kgN / m 3 / day as the nitrification rate, and the carrier cost is very high. Therefore, speeding up and cost reduction are desired.

  On the other hand, in the anaerobic treatment that does not require dissolved oxygen, the treatment rate per unit microorganism is slow, so the microorganism concentration in the tank can be increased by self-granulating the microorganism itself to form a high specific gravity lump or granule. A method of dramatically increasing the value is used. In the method using granulated microorganisms, since a high concentration of microorganisms can be retained in the tank, the processing speed per tank is faster than that using a carrier, and no carrier is required. Furthermore, since the specific gravity of the granules is high and the sedimentation speed is high, there are advantages such as easy solid-liquid separation. Microorganisms forming such granules have been confirmed in anaerobic methane fermentation, an upflow sludge blanket reactor (USB), and a semi-batch reactor (SBR) (see, for example, Patent Documents 1 to 3). .

JP 63-258695 A JP-A-1-262996 JP 2000-51893 A

  In a semi-batch reactor, (1) inflow of treated water, (2) oxygen supply and contact between treated water and microorganisms, (3) sedimentation of microorganisms, (4) discharge of treated water in one reaction tank However, since both the inflow of treated water and the discharge of treated water are performed in a short time, the fluctuation in the treatment flow rate becomes large, and a large flow rate adjustment tank in the implementation facility Is required. Therefore, although it can be a simple and advantageous device in a small-scale device, it is often difficult to apply to a medium-to-large device. In addition, when an upward flow type sludge blanket reactor (USB reactor) is used, a very high processing speed can be obtained, but a specially shaped reaction tank is used, resulting in an increase in equipment cost. In addition, due to the configuration of the apparatus, the inside of the denitrification tank cannot be sufficiently stirred, making it difficult to control the pH of the water to be treated. In the water to be treated containing calcium, etc., the generation of scales and inorganic substances in the granule Have problems such as accumulation.

  In order to solve these problems, it is desirable to use a completely mixed reaction tank that has been used in many devices in the past, and to have a device configuration that allows continuous flow (and continuous discharge) of water to be treated. There has never been a report on the formation of granules of denitrifying bacteria in such a device configuration.

  Accordingly, the present invention provides a method and a method for treating nitrogen-containing water capable of granulating a group of microorganisms containing nitrifying bacteria and denitrifying bacteria in a completely mixed type tank and a system in which treated water is continuously introduced. An object is to provide an apparatus.

  (1) The present invention provides a nitrification step of supplying water to be treated to a nitrification unit to oxidize ammonium ions in the water to be treated to nitric acid or nitrous acid, and the water to be treated in a complete mixing type denitrification unit. And a denitrification step of supplying a hydrogen donor and reducing the nitric acid or nitrous acid in the water to be treated into nitrogen gas, wherein the denitrification process comprises: In the process, the amount of the hydrogen donor added is varied with time so that the concentration of the hydrogen donor in the denitrification section changes with time.

  (2) The present invention also provides a nitrification step of supplying water to be treated to a nitrification unit to oxidize ammonium ions in the water to be treated to nitric acid or nitrous acid, and a complete mixing type denitrification unit. A denitrification step of supplying treated water, supplying a hydrogen donor, and reducing the nitric acid or nitrous acid in the treated water to nitrogen gas, and a biological treatment method of nitrogen-containing water, The denitrification unit includes at least a first denitrification unit and a second denitrification unit, and in the denitrification step, a concentration of a hydrogen donor between the first denitrification unit and the second denitrification unit. A hydrogen donor is supplied to at least the first denitrification unit so that a difference is formed.

  (3) In the method for treating nitrogen-containing water described in (2) above, the volume of the first denitrification unit is preferably 1/3 or less of the total volume of the denitrification unit.

  (4) In the method for treating nitrogen-containing water described in (1) above, the difference between the maximum concentration and the minimum concentration of the hydrogen donor in the denitrification part is preferably 50 mg TOC / L or more.

  (5) In the method for treating nitrogen-containing water described in (2) or (3) above, the maximum concentration of the hydrogen donor in the first denitrification part and the hydrogen donor in the second denitrification part It is preferable to supply the hydrogen donor to at least the first denitrification unit so that the difference from the minimum concentration of the compound becomes 50 mg TOC / L or more.

  (6) In addition, in the method for treating nitrogen-containing water according to (2), (3) or (5), the amount of the hydrogen donor added to the first denitrification unit is changed with time. Is preferred.

  (7) Moreover, in the processing method of nitrogen-containing water as described in any one of (1) to (6) above, it is preferable to return the sludge after the denitrification step to the nitrification step.

  (8) Further, in the method for treating nitrogen-containing water according to any one of (1) to (6) above, a treatment step of performing an organic matter treatment or a denitrification treatment of water to be treated before the nitrification step. The sludge after the denitrification step is preferably returned to at least one of the nitrification step and the treatment step.

  (9) The present invention also includes a nitrification unit that oxidizes ammonium ions in the water to be treated to nitric acid or nitrous acid, and a fully mixed type denitrification that reduces the nitric acid or nitrous acid in the water to be treated to nitrogen gas. A nitrogen-containing water treatment apparatus comprising: a nitriding unit; and a hydrogen donor supplying unit that supplies a hydrogen donor to the denitrifying unit, wherein the hydrogen donor supplying unit supplies hydrogen in the denitrifying unit. The amount of the hydrogen donor added is varied with time so that the concentration of the body changes with time.

  (10) The present invention also includes a nitrification unit that oxidizes ammonium ions in the water to be treated to nitric acid or nitrous acid, and a fully mixed type denitrification that reduces the nitric acid or nitrous acid in the water to be treated to nitrogen gas. A nitrogen-containing water treatment apparatus comprising: a nitriding unit; and a hydrogen donor supplying means for supplying a hydrogen donor to the denitrifying unit, wherein the denitrifying unit includes at least a first denitrifying unit and a second denitrifying unit. The hydrogen donor supply means includes at least the first denitrification unit so that a difference in hydrogen donor concentration is formed between the first denitrification unit and the second denitrification unit. Supply a hydrogen donor to the nitrogen section.

  (11) In the nitrogen-containing water treatment apparatus according to (10), it is preferable that a volume of the first denitrification unit is 1/3 or less of a total volume of the denitrification unit.

  (12) Moreover, in the nitrogen-containing water treatment apparatus as described in (9) above, the difference between the maximum concentration and the minimum concentration of the hydrogen donor in the denitrification part is preferably 50 mg TOC / L or more.

  (13) In the nitrogen-containing water treatment apparatus according to the above (10) or (11), the hydrogen donor supply means includes a maximum concentration of the hydrogen donor in the first denitrification unit, and the second It is preferable to supply the hydrogen donor to at least the first denitrification unit so that the difference from the minimum concentration of the hydrogen donor in the denitrification unit is 50 mg TOC / L or more.

  (14) In the nitrogen-containing water treatment apparatus according to (10), (11), or (13), the hydrogen donor supply means adds the hydrogen donor to be added to the first denitrification unit. It is preferable to vary the amount with time.

  (15) The nitrogen-containing water treatment apparatus according to any one of (9) to (14), further including a return unit that returns the sludge discharged from the denitrification unit to the nitrification unit. Is preferred.

  (16) Moreover, in the nitrogen-containing water treatment apparatus according to any one of the above (9) to (14), a treatment unit that performs an organic matter treatment or a denitrification treatment of water to be treated before the nitrification unit. It is preferable to provide a return means for returning the sludge discharged from the denitrification unit to at least one of the nitrification unit and the treatment unit.

  According to the present invention, a group of microorganisms containing nitrifying bacteria and denitrifying bacteria can be granulated in a completely mixed tank and a system in which water to be treated is continuously flowed, and the apparatus can be downsized or reduced in cost. Can be realized.

It is a schematic block diagram which shows an example of the processing method of nitrogen-containing water which concerns on this embodiment. It is a schematic block diagram which shows an example of the processing method of nitrogen-containing water which concerns on this embodiment. It is a schematic block diagram which shows an example of the processing method of nitrogen-containing water which concerns on this embodiment. It is a schematic block diagram which shows an example of the processing method of nitrogen-containing water which concerns on this embodiment. It is a schematic block diagram which shows an example of the processing method of nitrogen-containing water which concerns on this embodiment. It is a schematic block diagram which shows an example of the processing method of nitrogen-containing water which concerns on this embodiment. It is a figure which shows the change of the nitrification rate with respect to the test elapsed days of an Example and a comparative example. It is a figure which shows the change of the denitrification speed with respect to the test elapsed days of an Example and a comparative example. It is a figure which shows the change of the MLSS density | concentration with respect to the test elapsed days of an Example and a comparative example. It is a figure which shows the change of the water quality in the 1st denitrification tank of an Example. It is a figure which shows the change of the water quality in the 2nd denitrification tank of an Example.

  The present inventors have found that granules obtained by self-granulation of denitrifying bacteria can be easily formed by varying the concentration of the hydrogen donor added in the denitrifying reaction. Furthermore, by circulating this granule in the nitrogen-containing water treatment system that performs nitrification and denitrification, all fungal groups such as nitrifying bacteria are granulated, and the entire treatment system for nitrogen-containing water is substantially the same. It was found that it was possible to process with granule. Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

  FIGS. 1-6 is a schematic block diagram which shows an example of the processing method of nitrogen-containing water which concerns on this embodiment. 1A and 1B show a method for treating nitrogen-containing water in which treatment is performed in the order of a nitrification step, a denitrification step A or B, and a precipitation treatment step.

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

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

  The nitrogen-containing wastewater from which hydrogen peroxide and fluorine ions have been removed is temporarily stored in the water tank before being treated by the nitrification process, denitrification process, etc., and the flow rate and water quality required for the subsequent nitrification process are stabilized. At the same time, it is preferably adjusted to an appropriate pH. And the nitrogen-containing waste water (henceforth a to-be-processed water may be called) from which the flow volume, water quality, pH, etc. were adjusted will be sent to a nitrification process etc.

  The nitrification process is a process in which water to be treated is supplied to a nitrification unit (for example, a nitrification tank), and mainly ammonium ions in the water to be treated are aerobically (in the presence of oxygen) oxidized to nitric acid or nitrous acid. is there. The nitrification part is filled with a microorganism-supporting carrier formed by supporting a microorganism film containing nitrifying bacteria on a carrier. In addition, an air introduction pipe (not shown) is connected to the nitrification unit so that air can be supplied to the water to be treated in the nitrification unit. Then, in the nitrification unit, ammonium ions in the water to be treated are nitrified into nitric acid and nitrous acid by the action of the nitrifying bacteria of the microorganism-supporting carrier. Here, the nitrifying bacteria are ammonia-oxidizing bacteria that are autotrophic bacteria that nitrify ammonium ions contained in the water to be treated into nitrite, nitrite-oxidizing bacteria that are autotrophic bacteria that nitrify ammonium ions to nitric acid, and the like.

  The carrier on which nitrifying bacteria are supported is not particularly limited, and for example, sponges, gels, plastic molded products, and the like can be used. Specifically, it is preferable to use hydrophilic polyurethane sponge, polyvinyl alcohol gel, or the like. As will be described later, when returning the denitrification granules, a carrier on which nitrifying bacteria are supported is not necessarily required.

  The denitrification steps A and B are steps in which a hydrogen donor is supplied to a complete mixing type denitrification section and nitric acid or nitrous acid in the water to be treated is reduced to nitrogen gas under oxygen-free conditions. In the case of the denitrification step A, sludge containing denitrifying bacteria is accommodated in the denitrifying part (for example, a denitrifying tank), and in the denitrifying part, nitric acid or nitrous acid is reduced to nitrogen gas by the action of the denitrifying bacteria. Will be. In the case of the denitrification step B, the first denitrification unit (and the second denitrification unit) contains sludge containing denitrification bacteria, and the first denitrification unit (for example, the first denitrification tank) After making treated water contact denitrifying bacteria, treated water, denitrifying bacteria, and a hydrogen donor are sent to the 2nd denitrification part (for example, the 2nd denitrification tank). And in a 1st denitrification part and a 2nd denitrification part, nitric acid or nitrous acid in to-be-processed water is reduce | restored to nitrogen gas by the effect | action of denitrifying bacteria.

  When methanol is used as the hydrogen donor in the denitrification step, nitric acid (nitrate ions) and nitrous acid (nitrite ions) in the water to be treated are reduced to nitrogen gas by the reaction shown in the following reaction formula.

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

  In addition, in the denitrification step A, the amount of hydrogen donor added is changed over time so that the concentration of the hydrogen donor in the denitrification part changes with time. Further, in the denitrification step B, at least a first denitrification unit and a second denitrification unit are provided, and a predetermined hydrogen donor concentration difference is formed between the first denitrification unit and the second denitrification unit. As such, at least the first denitrification tank is fed with a hydrogen donor. In addition, the addition of the hydrogen donor in this embodiment is performed from the hydrogen donor addition line 10 connected to the denitrification part.

  Below, the supply method of the hydrogen donor in the denitrification process A will be described in detail.

  Normally, the hydrogen donor calculates the supply amount of the hydrogen donor required for the denitrification treatment from the concentration of nitrate ion and nitrite ion in the water to be treated supplied to the denitrification section, and changes the amount. Continuously supplied to the denitrification section. Therefore, the concentration of the hydrogen donor in the denitrification part is almost constant at a low concentration. In general, in order to efficiently perform the denitrification treatment, the hydrogen donor supply amount (the hydrogen donor necessary theoretical amount) necessary for the denitrification treatment of nitrate ions and nitrite ions in the denitrification portion is 1. About twice as much is supplied to the denitrification section.

  However, in the denitrification step A, hydrogen donor supply-stop (intermittent addition), hydrogen donor large-volume supply-small-volume supply, etc. are performed so that the hydrogen donor concentration in the denitrification section changes with time. Do. Thus, the granule which the sludge containing denitrifying bacteria self-granulated can be formed by giving a fluctuation | variation to the density | concentration of a hydrogen donor.

  Here, the difference between the maximum concentration and the minimum concentration of the hydrogen donor in the denitrification part (for example, in the hydraulic retention time of the water to be treated in the denitrification tank part) is 50 mg TOC / L or more. It is preferable to supply a hydrogen donor into the denitrification part, and it is more preferable to supply a hydrogen donor into the denitrification part so as to be 100 mg TOC / L or more. If the difference between the maximum concentration and the minimum concentration of the hydrogen donor in the denitrification part is smaller than 50 mg TOC / L, self-granulation of the denitrifying bacteria may not be sufficiently induced.

  Here, it is preferable that the minimum concentration of the hydrogen donor in the denitrification part is ½ or less (greater than 0 and ½ or less of the maximum concentration) with respect to the maximum concentration. If the minimum concentration exceeds 1/2 with respect to the maximum concentration, it may be difficult to induce self-granulation of denitrifying bacteria.

  In this embodiment, the concentration of the hydrogen donor in the denitrification unit can be changed over time by intermittently supplying the hydrogen donor to the denitrification unit. Specifically, at the time of supplying the hydrogen donor, the concentration of the hydrogen donor in the denitrification unit is increased by supplying the hydrogen donor at a rate exceeding the processing rate of the denitrifying bacteria present in the denitrification unit, Thereafter, the concentration of the hydrogen donor in the denitrification unit is lowered by stopping the supply of the hydrogen donor.

  The supply stop time of the hydrogen donor is preferably longer than 50% of the supply time of the hydrogen donor. If the supply stop time of the hydrogen donor is 50% or less of the supply time of the hydrogen donor, even if the difference between the maximum concentration and the minimum concentration of the hydrogen donor is, for example, 50 mg TOC / L or more, It may be difficult to sufficiently induce self-granulation of the sludge contained.

  When a plurality of hydrogen donor supply and stop cycles are performed, the time of one cycle (feed-stop) is shorter than 50% of the hydraulic residence time, that is, two cycles or more with respect to the hydraulic residence time. It is preferable. If only one cycle is performed for the hydraulic residence time, the difference between the maximum concentration and the minimum concentration of the hydrogen donor increases, but treated water having a high hydrogen donor concentration is discharged outside the denitrification section. For this reason, the load of the oxidation tank or the like installed for removing the hydrogen donor from the treated water is increased, and the quality of the treated water may be deteriorated. In addition, since the number of hydrogen donors that are not effectively used in the denitrification treatment increases, it is necessary to increase the supply amount of the hydrogen donor, which may increase the cost of the dechambering treatment.

  In this embodiment, the amount of nitric acid and nitrous acid in the denitrification part is smaller than the reference value based on the supply amount of hydrogen donor (necessary theoretical amount of hydrogen donor) required for the denitrification treatment. A hydrogen donor is supplied to the denitrification unit by combining a first supply step for supplying the hydrogen donor to the denitrification unit and a second supply step for supplying a hydrogen donor in an amount greater than the reference value to the denitrification unit. The hydrogen donor concentration in the denitrification part can also be changed over time by supplying.

  The supply time of the hydrogen donor in the first supply step is preferably longer than 50% of the supply time of the hydrogen donor in the second supply step. When the supply time of the hydrogen donor in the first supply step is 50% or less of the supply time of the hydrogen donor in the second supply step, the difference between the maximum concentration and the minimum concentration of the hydrogen donor is, for example, 50 mg TOC / L Even in this case, it may be difficult to sufficiently induce self-granulation of denitrifying bacteria.

  When a plurality of cycles of the first supply step and the second supply step are performed, the time of one cycle (first supply step-second supply step) is shorter than 50% of the hydraulic residence time, that is, the hydraulic residence It is preferable to perform two or more cycles with respect to time. If only one cycle is performed for the hydraulic residence time, the difference between the maximum concentration and the minimum concentration of the hydrogen donor increases, but treated water having a high hydrogen donor concentration is discharged outside the denitrification section. For this reason, the load of the oxidation tank or the like installed for removing the hydrogen donor from the treated water is increased, and the quality of the treated water may be deteriorated. In addition, since the number of hydrogen donors that are not effectively used in the denitrification treatment increases, it is necessary to increase the supply amount of the hydrogen donor, which may increase the cost of the dechambering treatment.

  Moreover, in this embodiment, it is preferable that the minimum concentration of the hydrogen donor in a denitrification part is 100 mgTOC / L or less, and it is more preferable that it is the range of 2 mgTOC / L-100 mgTOC / L. If the minimum concentration of the hydrogen donor is greater than 100 mg TOC / L, it may be difficult to sufficiently induce self-granulation of denitrifying bacteria. Moreover, when the minimum concentration of the hydrogen donor is smaller than 2 mg TOC / L, the denitrification treatment cannot be performed efficiently, and the quality of the treated water may be deteriorated.

  Next, a method for forming a hydrogen donor concentration difference in the denitrification step B will be described.

  In the denitrification step B, the hydrogen donor is supplied to at least the first denitrification unit so that a concentration difference of the hydrogen donor is formed between the first denitrification unit and the second denitrification unit. In the denitrification step B, it is sufficient that two or more denitrification units are provided, for example, between the first denitrification unit and the second denitrification unit, etc. Nitrogen tank) may be installed. And in this specification, the denitrification part with the highest hydrogen donor concentration is defined as a first denitrification part, and the denitrification part with the lowest hydrogen donor concentration is defined as a second denitrification part.

  In the present embodiment, the denitrification unit is desirably a tank type, but is not necessarily limited to this, and particularly in the first denitrification unit, a contact opportunity between the water to be treated and the hydrogen donor is ensured. If it can do, it does not necessarily need to be a tank type, and may be a line (tube) having a predetermined length.

  The volume of the first denitrification unit is preferably 1/3 or less of the total volume of the denitrification unit in order to increase the concentration difference of the hydrogen donor with the second denitrification unit, and further, the entire denitrification unit It is preferable that it is 1/5 or less of the volume. In addition, when the HRT (hydraulic residence time) of the first denitrification unit becomes too short, the consumption of dissolved oxygen in the inflowing treated water cannot catch up and the first denitrification unit becomes an aerobic condition. There is. Therefore, although depending on the nitrate ion, nitrite ion concentration, and dissolved oxygen concentration in the water to be treated, the first denitrification unit is preferably of a size that can secure an HRT of several minutes or more. The lower limit of the volume of the part is preferably 1/30 or more of the volume of the entire denitrification part, and more preferably 1/20 or more of the volume of the whole denitrification part.

  Here, the maximum concentration of the hydrogen donor in the first denitrification unit (for example, in the hydraulic residence time (HRT) of the treated water in the second denitrification unit), and (for example, in the second denitrification unit) Supply the hydrogen donor in at least the first denitrification part so that the difference from the minimum concentration of hydrogen donor in the second denitrification part (in the hydraulic residence time of the treated water) is 50 mg TOC / L or more. It is preferable to supply a hydrogen donor into at least the first denitrification unit so that the concentration is 100 mg TOC / L or more. If the difference between the maximum hydrogen donor concentration in the first denitrification section and the minimum hydrogen donor concentration in the second denitrification section is less than 50 mg TOC / L, self-granulation of sludge containing denitrifying bacteria will occur. There are cases where it cannot be sufficiently guided.

  The amount of hydrogen donor added is calculated from the nitrate ion or nitrite ion concentration in the water to be treated. Usually, a value obtained by adding the amount used for consumption of dissolved oxygen in the water to be treated to the above calculated value and multiplying by a certain safety factor is determined as the addition amount of the hydrogen donor. In the denitrification step B, the determined amount of hydrogen donor may be continuously supplied to the first denitrification unit (may also be supplied to the second denitrification unit). When the concentration of nitrate ion and nitrite ion is low, the concentration of the hydrogen donor necessary for the denitrification treatment is also low. Therefore, between the first denitrification part and the second denitrification part, It becomes difficult to form a density difference.

  In such a case, the amount of hydrogen donor added to the first denitrification part is increased, or supply of hydrogen donor as described above-stop (intermittent addition), supply of a large amount of hydrogen donor- By providing a temporal variation in the amount of hydrogen donor added, such as by supplying a small amount, a difference in hydrogen donor concentration is easily formed between the first denitrification unit and the second denitrification unit. be able to. The hydrogen donor supply and stop time and the hydrogen donor large amount supply-small amount supply time are determined by the maximum concentration of the hydrogen donor in the first denitrification part and the minimum concentration of the hydrogen donor in the second denitrification part. It is preferable that the difference is set to be 50 mg TOC / L or more, for example.

  When multiple hydrogen donor supply and stop cycles are performed in the first denitrification section, when multiple hydrogen donor supply-small supply cycles are performed, the hydrogen donor in the second denitrification section at the subsequent stage One cycle time is shorter than 50% of the hydraulic detention time in the entire denitrification section, that is, two cycles with respect to the hydraulic residence time in the entire denitrification section in that the concentration can be averaged. It is preferable to perform the above.

  In the present embodiment, it is sufficient to supply the hydrogen donor to at least the first denitrification unit. However, a concentration difference of the hydrogen donor is formed between the first denitrification unit and the second denitrification unit. The hydrogen donor may also be supplied to the second denitrification unit (including supply-stop intermittent supply, large amount supply-small amount supply, etc.).

  In addition, when granulating denitrifying bacteria, addition of some metals may give a favorable result. These are generally positioned as granulation accelerators, and examples of ions include calcium ions and iron ions, examples of compounds include fly ash, iron oxide, and calcium carbonate. Among these, ions are preferably added continuously or intermittently over the denitrification treatment period or at the start-up period of the apparatus. Further, regarding the compounds, it is preferable to add them together with the addition of sludge when the apparatus is started up.

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

  The reduction reaction from nitrate ion or nitrite ion to nitrogen gas is slightly different depending on the type of hydrogen donor, but in any case, nitrate ion and equimolar hydroxide ion are formed, so denitrification The treated water pH in the section rises. In general, it is preferable to adjust the pH of water to be treated in the denitrification treatment to a range of 8-9. However, when the carbonate ion concentration derived from the hydrogen donor is high and there is a concern about the generation of scale due to calcium ions or the like contained in the water to be treated, the pH of the water to be treated in the denitrification section is 6 to 7.5. It is preferable to adjust to a range, and it is more preferable to adjust to the range of 6.3-7.0. For example, a pH sensor is installed in the denitrification unit to detect the pH of the water to be treated in the denitrification unit, and based on the detected pH value, the pH of the water to be treated in the denitrification unit is in the above range. Then, an acid agent or an alkali agent is supplied to the denitrification unit, and the pH of the water to be treated in the denitrification unit is adjusted.

  Next, the sludge is separated from the treated water discharged from the denitrification steps A, B, etc. by the precipitation treatment step. 1 (A) and 1 (B) are provided with a return line 12 for returning the sludge separated from the treated water in the precipitation process to the nitrification process, and the granules obtained by the denitrification process A or B of the present embodiment. Sludge can be circulated. As a result, granules containing nitrifying bacteria are formed, so that the nitrification process and the like can be processed with the same granules.

  2A and 2B show a method for treating nitrogen-containing water in which treatment is performed in the order of an organic matter treatment step, a nitrification step, a denitrification step A or B, and a precipitation treatment step. The organic matter treatment process treats organic nitrogen and other organic matter in the water to be treated under aerobic or anaerobic conditions, and converts organic nitrogen to ammonia nitrogen along with removal of organic matter (eg IPA, TMAH, etc.) It is the process of doing. Further, the treatment of nitrogen-containing water shown in FIGS. 2 (A) and 2 (B) includes a return line 14 for returning sludge separated from the treated water in the precipitation treatment step to the organic matter treatment step. Granule sludge obtained by the denitrification step A or B can be circulated. As a result, granules containing nitrifying bacteria are formed, so that the nitrification process and the like can be processed with the same granules.

  3A and 3B show a method for treating nitrogen-containing water in which treatment is performed in the order of the nitrification step, the denitrification step A or B, the oxidation step, and the precipitation treatment step. An oxidation process is a process of aerobically processing the surplus of the hydrogen donor added by denitrification. Similarly, the treatment of the nitrogen-containing water shown in FIGS. 3A and 3B includes a return line 12 for returning the sludge separated from the treated water by the precipitation treatment step to the nitrification step. Granule sludge obtained by the process A or B can be circulated. As a result, granules containing nitrifying bacteria are formed, so that the nitrification process and the like can be processed with the same granules.

  4A and 4B show a treatment method for nitrogen-containing water in which the denitrification step A or B, the nitrification step, the denitrification step C, the oxidation step, and the precipitation treatment step are performed in this order. 5A and 5B show a treatment method for nitrogen-containing water in which treatment is performed in the order of denitrification step C, nitrification step, denitrification step A or B, oxidation step, and precipitation treatment step. In the denitrification step C, hydrogen is supplied to the denitrification unit intermittently or in a large amount—a small amount is supplied, or a predetermined concentration difference is provided between the first denitrification unit and the second denitrification unit. This is a conventional denitrification process in which nitric acid or nitrite nitrogen is reduced to nitrogen gas under oxygen-free conditions without supplying a body. In addition, in the processing method of nitrogen-containing water of FIG. 4 (A), (B) or FIG. 5 (A), (B), in order to improve processing performance, a part of the processing water obtained by a nitrification process is changed to the former stage. Are returned to the denitrification step A, B or denitrification step C. Similarly, in the treatment of the nitrogen-containing water shown in FIGS. 4 (A), 4 (B) and FIGS. 5 (A), 5 (B), the return line 16 returns the sludge separated from the treated water in the precipitation treatment step to the denitrification step. The granular sludge obtained by the denitrification process A or B of this embodiment is circulated. In this case, since granules containing nitrifying bacteria are formed, the nitrification process and the like can be processed with the same granules.

  FIGS. 6A and 6B show a method for treating nitrogen-containing water in which treatment is performed in the order of an organic matter treatment step, a nitrification step, a denitrification step A or B, an oxidation step, and a precipitation treatment step. Similarly, the treatment of the nitrogen-containing water shown in FIGS. 6A and 6B includes a return line 12 for returning the sludge separated from the treated water in the precipitation treatment step to the organic matter treatment step. Granule sludge obtained by the nitriding step A or B is circulated. As a result, granules containing nitrifying bacteria are formed, so that the nitrification process and the like can be processed with the same granules.

  In these embodiments, existing methods can be used for organic matter treatment, nitrification treatment, oxidation treatment, and the like. The conventional technique can also be applied to the precipitation treatment, but in granulation, it is preferable to screen sludge having a high density by applying a certain amount of water area load and hold it in the system. In an ordinary activated sludge system, the water area load is generally designed to be about 0.6 m / hr or less, but in this embodiment, it is preferably 0.8 m / hr or more. More preferably, it is 0.0 m / hr or more.

  Moreover, when the sludge separated by the precipitation treatment is returned to the organic matter treatment step, the nitrification step, etc., the return rate is preferably about 10% to 200% with respect to the flow rate of the water to be treated. The return can be performed by a normal pump (not shown) installed in the return line (12, 14, 16). However, the granule may be crushed by a normal spiral pump, so that the rotary displacement type is used. It is preferable to perform the return using a pump, a tube pump, an air lift pump or the like.

  In addition, in the precipitation treatment step, instead of installing a precipitation tank, a denitrification part or a part of the oxidation tank is partitioned to provide a sedimentation part, a GSS is provided in the denitrification part or the oxidation tank, a membrane separation device, etc. It may be provided.

  In addition, the water to be treated, which is to be treated, is basically continuously flowed in. However, even if a flow rate adjustment tank or the like is installed and the level control of the flow rate adjustment tank is used, ON / OFF control of the inflow of treated water is performed. Good. Also in this case, in this embodiment, the granule is formed satisfactorily. It is desirable to control the addition time and timing of the hydrogen donor in accordance with the inflow of the water to be treated.

  Although it does not restrict | limit especially as MLSS density | concentration in a denitrification part, It is preferable that MLSS density | concentration shall be about 5000-100000 mgMLSS / L at the point which can achieve sufficient processing speed.

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

  In the example, the test was performed by the processing method shown in FIG. A nitrification tank having a volume of 36 L was used in the nitrification process, a first denitrification tank having a volume of 4 L and a second denitrification tank having a volume of 36 L were used in the denitrification process B, and an oxidation tank having a volume of 20 L was used in the oxidation treatment process.

  Water to be treated shown in Table 1 below was continuously passed. Moreover, air was aerated in the nitrification tank and the oxidation tank, and DO was maintained at 2 mgO / L or more. A stirrer was installed in the first denitrification tank and the second denitrification tank to perform stirring. Methanol was used as a hydrogen donor and added intermittently to the first denitrification tank. One cycle of addition and stop of the hydrogen donor was 1/4 of the second denitrification tank HRT calculated from the flow rate of the water to be treated and the volume of the second denitrification tank. The time ratio of addition and termination of the hydrogen donor was 1:19. In Example 1, the amount of water to be treated was increased stepwise so that the total nitrogen concentration in the treated water discharged from the sedimentation tank was 10 mgN / L or less, and the load was increased. The amount of methanol added was 3 kg methanol / kgN with respect to the inflow nitrogen amount. Moreover, the activated sludge which is performing denitrification so that it may become about 500 mgMLSS / L at the time of a test start was supplied to the 1st denitrification tank and the 2nd denitrification tank. Moreover, pH controllers were installed in the nitrification tank and the second denitrification tank, and the pH of the water to be treated was adjusted to 7.0 to 7.5 using hydrochloric acid or sodium hydroxide. Moreover, the sludge collected in the sedimentation tank installed in the latter stage of the denitrification part was returned to the nitrification tank using an air lift pump.

  In the comparative example, the test was performed under the same conditions as in Example 1 except that the first denitrification tank was not installed and the hydrogen donor was continuously added to the second denitrification tank.

FIG. 7 is a graph showing changes in the nitrification rate with respect to the number of days elapsed from the test in Examples and Comparative Examples. FIG. 8 is a graph showing changes in the denitrification rate with respect to the number of days elapsed in the tests of the examples and comparative examples. FIG. 9 is a diagram showing a change in the MLSS concentration with respect to the number of days elapsed from the test in the examples and the comparative examples. In the comparative example, the temporary nitrification rate increased to 0.3 kg N / m ³ / day and the denitrification rate increased to around 0.4 kg N / m ³ / day, but the sludge flowed out from the settling tank, and the sludge concentration was sufficient. Could not be maintained. For this reason, the MLSS concentration also decreased, and as a result, the nitrification rate was stabilized at 0.15 kgN / m ³ / day and the denitrification rate was stabilized at around 0.18 kgN / m ³ / day. In addition, the sludge was hardly granulated. In the examples, an increase in the MLSS concentration was confirmed, and the nitrification rate and the denitrification rate increased accordingly, and after 2 months from the start of the test, both the nitrification rate and the denitrification rate were about 0.6 kgN / m ³ / day. The speed was about 3 times that of the comparative example. The sludge was self-granulated and formed granules with a diameter of about 200 μm.

  FIG. 10 is a diagram showing a change in water quality in the first denitrification tank of the example, and FIG. 11 is a diagram showing a change in water quality in the second denitrification tank of the example. In the 1st denitrification tank of an Example, the fluctuation | variation of the hydrogen donor density | concentration of about 0-200 mgTOC / L (maximum concentration is about 200 mgTOC / L) is given as a TOC density | concentration, and 2-18 mgTOC as a TOC density | concentration in a 2nd denitrification tank. It was confirmed that a variation in hydrogen donor concentration of about / L (minimum concentration was about 2 mg TOC / L) was given.

  10 Hydrogen donor addition line, 12, 14, 16 Return line.

Claims (16)

A nitrification step of supplying treated water to the nitrification unit and oxidizing ammonium ions in the treated water to nitric acid or nitrous acid;
A denitrification step of supplying the water to be treated to a fully mixed denitrification section, supplying a hydrogen donor, and reducing the nitric acid or nitrous acid in the water to be treated to nitrogen gas. A biological treatment method for water,
In the denitrification step, a method for treating nitrogen-containing water is characterized in that the amount of hydrogen donor added is changed over time so that the concentration of the hydrogen donor in the denitrification section changes with time. . A nitrification step of supplying treated water to the nitrification unit and oxidizing ammonium ions in the treated water to nitric acid or nitrous acid;
A denitrification step of supplying the water to be treated to a fully mixed denitrification section, supplying a hydrogen donor, and reducing the nitric acid or nitrous acid in the water to be treated to nitrogen gas. A biological treatment method for water,
The denitrification unit includes at least a first denitrification unit and a second denitrification unit,
In the denitrification step, a hydrogen donor is supplied to at least the first denitrification unit so that a concentration difference of the hydrogen donor is formed between the first denitrification unit and the second denitrification unit. A method for treating nitrogen-containing water, comprising:   The method for treating nitrogen-containing water according to claim 2, wherein the volume of the first denitrification unit is 1/3 or less of the total volume of the denitrification unit. .   The method for treating nitrogen-containing water according to claim 1, wherein the difference between the maximum concentration and the minimum concentration of the hydrogen donor in the denitrification part is 50 mg TOC / L or more. Method.   The method for treating nitrogen-containing water according to claim 2 or 3, wherein the difference between the maximum hydrogen donor concentration in the first denitrification part and the minimum hydrogen donor concentration in the second denitrification part. However, the hydrogen-containing water is supplied to at least the first denitrification unit so as to be 50 mg TOC / L or more.   The method for treating nitrogen-containing water according to claim 2, 3 or 5, wherein the amount of the hydrogen donor added to the first denitrification part is temporally varied. Processing method.   It is a processing method of nitrogen-containing water of any one of Claims 1-6, Comprising: The sludge after the said denitrification process is returned to the said nitrification process, The processing method of nitrogen-containing water characterized by the above-mentioned. It is a processing method of nitrogen content water given in any 1 paragraph of Claims 1-6, Comprising: The processing process which performs organic matter processing or denitrification processing of to-be-processed water before the nitrification process,
A method for treating nitrogen-containing water, wherein the sludge after the denitrification step is returned to at least one of the nitrification step and the treatment step. A nitrification part that oxidizes ammonium ions in the water to be treated to nitric acid or nitrous acid;
A fully mixed denitrification section for reducing the nitric acid or nitrous acid in the treated water to nitrogen gas;
A hydrogen donor supply means for supplying a hydrogen donor to the denitrification unit, and a nitrogen-containing water treatment apparatus comprising:
The hydrogen donor supply means is characterized in that the amount of hydrogen donor added varies with time so that the concentration of the hydrogen donor in the denitrification section changes over time. Processing equipment. A nitrification part that oxidizes ammonium ions in the water to be treated to nitric acid or nitrous acid;
A fully mixed denitrification section for reducing the nitric acid or nitrous acid in the treated water to nitrogen gas;
A hydrogen donor supply means for supplying a hydrogen donor to the denitrification unit, and a nitrogen-containing water treatment apparatus comprising:
The denitrification unit includes at least a first denitrification unit and a second denitrification unit,
The hydrogen donor supply means includes at least a hydrogen donor in the first denitrification unit so that a difference in hydrogen donor concentration is formed between the first denitrification unit and the second denitrification unit. An apparatus for treating nitrogen-containing water.   The apparatus for treating nitrogen-containing water according to claim 10, wherein the volume of the first denitrification unit is 1/3 or less of the total volume of the denitrification unit. .   The apparatus for treating nitrogen-containing water according to claim 9, wherein the difference between the maximum concentration and the minimum concentration of the hydrogen donor in the denitrification part is 50 mg TOC / L or more. apparatus.   12. The apparatus for treating nitrogen-containing water according to claim 10, wherein the hydrogen donor supply means includes a maximum concentration of the hydrogen donor in the first denitrification unit and a hydrogen in the second denitrification unit. An apparatus for treating nitrogen-containing water, wherein a hydrogen donor is supplied to at least the first denitrification unit so that a difference from the minimum concentration of the donor is 50 mg TOC / L or more.   14. The apparatus for treating nitrogen-containing water according to claim 10, 11 or 13, wherein the hydrogen donor supply means gives a temporal variation to the addition amount of the hydrogen donor added to the first denitrification section. An apparatus for treating nitrogen-containing water.   It is a processing apparatus of nitrogen content water given in any 1 paragraph of Claims 9-14, Comprising: It has a return means which returns sludge discharged from said denitrification part to said nitrification part, It contains nitrogen Water treatment equipment. The nitrogen-containing water treatment apparatus according to any one of claims 9 to 14, further comprising a treatment unit that performs an organic matter treatment or a denitrification treatment of water to be treated in a stage preceding the nitrification unit,
An apparatus for treating nitrogen-containing water, comprising a return means for returning sludge discharged from the denitrification section to at least one of the nitrification section and the treatment section.