JP2008023485A - Biological denitrification method and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waste water treatment process in which waste water is treated efficiently by biologically denitrifying waste water in the same and one tank where an autotrophic denitrifying microorganism coexists with a heterotrophic denitrifying microorganism and to provide a biological denitrification method and a biological denitrification apparatus, in each of which the simplification of a structure of the biological denitrification apparatus, a reduction in costs and the shortening of a period of construction work can be realized. <P>SOLUTION: The biological denitrification method being a method for biologically treating waste water containing ammonia nitrogen comprises: a waste water supply step of directly supplying at least a part of the waste water to be treated to a denitrification tank and supplying the reminder being the waste water unsupplied to the denitrification tank to a nitration tank; a nitration step of nitrating the waste water supplied to the nitration tank; and a denitrification step of supplying an electron donor to the denitrification tank to denitrify the ammonia nitrogen contained in the waste water supplied directly to the denitrification tank and the nitrate nitrogen which is contained in the waste water, which is supplied from the nitration tank to the denitrification tank, and produced by the nitration at the nitration step. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention treats wastewater by coexisting an independent or heterotrophic denitrifying microorganism that denitrifies ANAMMOX microorganisms and nitric acid in a single tank, thereby producing high-quality treated water with low residual nitrogen and low cost. The present invention relates to a biodenitrification method and apparatus that can be obtained.

  In general, ammonia nitrogen in wastewater is oxidized by ammonia oxidizing bacteria to nitrite nitrogen, and nitrifying nitrogen is oxidized to nitrate nitrogen by nitrite oxidizing bacteria. Nitrite nitrogen and nitrate nitrogen are denitrified bacteria, which are heterotrophic bacteria, and are converted into nitrogen gas through a two-stage biological reaction with a denitrification process that decomposes organic matter into nitrogen gas using an electron donor. Disassembled. However, such a conventional nitrification denitrification method requires a large amount of organic matter such as methanol as an electron donor in the denitrification step, and also requires a large amount of oxygen in the nitrification step, so that the running cost is high. is there.

In contrast, in recent years, ammonia nitrogen and nitrite nitrogen are reacted using autotrophic microorganisms (autotrophic bacteria) using ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor. A method of denitrifying by letting go was proposed. This denitrification treatment by autotrophic denitrification microorganisms (hereinafter sometimes referred to as “ANAMMOX microorganisms”) proceeds by the following ANAMMOX reaction.
NH ₄ ⁺ + 1.32NO ₂ ⁻ → N ₂ + 0.26NO ₃ ⁻ + 2H ₂ O

  ANAMMOX microorganisms are absolutely anaerobic microorganisms that are inhibited by trace amounts of oxygen, that they are inhibited when organic matter remains, and that they are significantly inhibited under absolute anaerobic conditions where hydrogen sulfide is generated. Has been said. However, the wastewater treatment using the ANAMMOX reaction does not require oxidation to nitrate nitrogen by simply nitrifying ammonia nitrogen and organic nitrogen in the wastewater to nitrite nitrogen. From the point of view of this, it is energy-saving, and it does not require a hydrogen donor unlike the conventional denitrification reaction by nitrate respiration of heterotrophic denitrifying microorganisms. Since there is no need for addition, and since it is an autotrophic denitrifying microorganism, it has great advantages such as a low cell conversion rate and extremely low surplus sludge generation, making it an efficient wastewater treatment process. Expected.

  On the other hand, in the ANAMMOX reaction, nitrate nitrogen cannot be denitrified. Therefore, ammonia nitrogen must be treated with nitrite in the nitrification process before denitrification, and nitrite is treated by biological treatment. However, strict operations such as control of air amount, water temperature, pH, and carbonic acid supply amount were required, and stable nitritation control over a long period of time was difficult.

Furthermore, because ANAMMOX microorganisms are inhibited by residual organic matter, it is difficult to treat nitrate nitrogen by coexisting with heterotrophic denitrifying bacteria that require organic matter as an electron donor in the same tank. I came. Therefore, a method of denitrifying only a small amount of nitric acid by-produced by ANAMMOX reaction by adding heterodegradable solid organic substances by heterotrophic denitrifying microorganisms (Patent Document 1), or batch-type treatment reaction instead of continuous treatment Has been proposed in which the nitrite nitrogen and nitrate nitrogen remaining in the treated water after the ANAMMOX reaction are denitrified by heterotrophic denitrifying bacteria (Patent Document 2). Further, since ANAMMOX microorganisms are generally considered to have a slow growth rate, a method of adding a small amount of hydrazine, methanol or the like as a growth promoter when the apparatus is started up has been proposed (Patent Document 3). In this specification, the terms “microorganism”, “bacteria”, and “fungus” may be used in connection with ANAMMOX and denitrification, all of which are synonymous.
Japanese Patent Laid-Open No. 2004-283758 JP 2003-39092 A JP 2003-1292 A

  In view of the current situation as described above, the present invention provides an efficient wastewater treatment process in wastewater treatment for biological denitrification by allowing autotrophic denitrification microorganisms and heterotrophic denitrification microorganisms to coexist in the same tank. An object of the present invention is to provide a biological denitrification method and apparatus capable of simplifying the structure of the apparatus, reducing costs, shortening the construction period, and the like.

The biological denitrification method according to the present invention that meets the above-mentioned object is a biological treatment method of ammoniacal nitrogen-containing wastewater,
A wastewater supply step of supplying at least a part of the wastewater to be treated directly to the denitrification tank and supplying the remaining wastewater not supplied to the denitrification tank to the nitrification tank;
A nitrification process for nitrating the wastewater supplied to the nitrification tank;
Electron donors in the denitrification tank are ammoniacal nitrogen in the wastewater that has been directly supplied to the denitrification tank and nitrate nitrogen that has been nitrated in the nitrification step in the wastewater that is supplied from the nitrification tank to the denitrification tank. A denitrification step of denitrifying by supplying
It comprises the method characterized by including.

Moreover, the biological denitrification apparatus according to the present invention is a biological treatment apparatus for ammonia nitrogen-containing wastewater,
A waste water supply means for supplying at least part of the waste water to be treated directly to the denitrification tank by bypassing the nitrification tank and supplying the remaining waste water not supplied to the denitrification tank to the nitrification tank;
Nitrification means for nitrating the wastewater that has been supplied to the nitrification tank;
Electron donors in the denitrification tank are ammonia nitrogen in the wastewater that has been directly supplied to the denitrification tank and nitrate nitrogen that has been nitrated by the nitrification means in the wastewater that is supplied from the nitrification tank to the denitrification tank. Denitrification means for denitrification by supplying
It comprises the apparatus characterized by including.

  That is, the biological denitrification method and apparatus according to the present invention bypasses the nitrification tank for a part of the wastewater to be treated and supplies it to the denitrification tank together with the remaining wastewater nitrated under the addition of the electron donor. In addition, denitrification is performed efficiently and at low cost at an appropriate ratio of ammonia nitrogen and nitrate nitrogen.

  In the biological denitrification method and apparatus according to the present invention, it is preferable to use a fluidized bed biological treatment apparatus for the denitrification step. A fluidized bed biological treatment apparatus can also be used for the nitrification step. As a biological carrier in a fluidized bed biological treatment apparatus, for example, at least one of sponge, gel, granule, and plastic molded product can be used.

  By using a fluidized bed biological treatment device that is easier to install and easier to modify the existing equipment in the denitrification process, the internal structure of the tank can be simplified and the construction period and cost can be reduced. it can.

  According to the biological denitrification method and apparatus according to the present invention, ammonia nitrogen and nitrate nitrogen are supplied to the denitrification tank at an appropriate ratio by supplying a part of the waste water directly to the denitrification tank, bypassing the nitrification tank. This makes it possible to perform efficient processing in the denitrification tank. Further, nitritation treatment is unnecessary and stable treatment can be performed for a long time.

  Further, by using a fluidized bed type denitrification device, the existing facilities can be easily improved and the structure of the device is simplified, so that the construction period and cost can be reduced.

Hereinafter, the present invention will be described in detail together with preferred embodiments.
FIG. 1 is a schematic configuration diagram showing an example of a nitrogen-containing wastewater treatment apparatus suitable for carrying out the method according to the present invention. For comparison, FIG. 2 shows a schematic configuration of an example of a conventional denitrification apparatus, and FIG. 3 shows a schematic configuration of an example of a processing apparatus using a conventional ANAMOX reaction.

  For example, when the ammonia nitrogen-containing wastewater discharged in the semiconductor industry is treated in a wastewater treatment apparatus comprising a nitrification tank, a denitrification tank, and an oxidation tank, the present invention is implemented with the configuration shown in FIG. Therefore, wastewater treatment can be performed at a low cost.

  Specifically, for example, as shown in FIG. 1, nitrification tank 2 in which ammonia nitrogen in waste water 1 is nitrate nitrogen, and nitrate nitrogen in treated water (drain water) from nitrification tank 2 is denitrified. In a wastewater treatment apparatus comprising a denitrification tank 3 and an oxidation tank 4 for treating organic matter remaining in wastewater treated in the denitrification tank 3, a part of the wastewater 1 is directly bypassed the nitrification tank 2 and directly denitrification tank 3 is supplied. In the denitrification tank 3, ammonia nitrogen used as an electron donor in a reaction by an autotrophic denitrifying microorganism (ANAMMOX reaction) is supplied by the bypass line B, and an electron by a reaction by a heterotrophic denitrifying microorganism (denitrification reaction). The organics used as donors are supplied by line Y. The present invention can be implemented by coexisting the above-mentioned ANAMMOX reaction treatment and denitrification reaction treatment. That is, ammonia is converted into nitric acid in the nitrification tank 2, and ammonia that has been bypassed in the denitrification tank 3 that performs denitrification and ANAMMOX reaction is added, and methanol is added, and the interaction between the denitrifying bacteria and ANAMMOX bacteria (from denitrifying bacteria to ANAMMOX The nitric acid and ammonia are treated with nitrogen by the delivery of nitrous acid to the bacteria, and if there is excess methanol added, it is treated in the oxidation tank 4. In addition, as organic substances to be added as an electron donor, in addition to soluble organic substances (alcohols) such as methanol, isopropyl alcohol, propionic acid, formic acid, acetic acid (organic acids), alanine, and glucose, hardly soluble liquids such as oil Organic matter is also conceivable. In addition, an autotrophic denitrifying bacterium that supplies hydrogen gas and a reduced sulfur compound into the tank and uses the hydrogen gas or the reduced sulfur compound as an electron donor may be used.

  The electron donor is ammonia in the case of ANAMMOX microorganisms, hydrogen in the case of other independent denitrifying microorganisms, and organic substance in the case of reduced sulfur and heterotrophic denitrifying bacteria. The electron acceptor is nitrous acid for ANAMMOX microorganisms, nitric acid or nitrous acid for other independent denitrifying microorganisms, and nitric acid or nitrous acid for reduced sulfur and heterotrophic denitrifying bacteria.

  At this time, the ammonia nitrogen supplied as an electron donor to the denitrification tank remains in the treated water from the nitrification tank, or bypasses part of the ammonia nitrogen-containing waste water to be treated. Can be supplied.

  In addition, sufficient organic matter and autotrophic denitrifying bacteria are available for use by heterotrophic denitrifying bacteria as electron donors in the nitrification tank treated water and ammonia nitrogen-containing wastewater supplied to the denitrifying tank. If sufficient electron donor is contained in the liquid, supply of methanol or the like is not necessary.

  Further, when the organic matter such as methanol supplied in the denitrification tank is consumed in the denitrification tank and does not remain, the subsequent oxidation tank 4 is not necessary.

  The means for nitrating nitric acid is not limited to that by biological treatment, and adjusting the pH and the like in a denitrification tank is a general means.

  Furthermore, from the viewpoint of early start-up of biological treatment, what has been accumulated in advance in a state where autotrophic denitrifying bacteria having a slow growth rate are attached to sludge or a carrier in advance may be added to the denitrification tank. .

  In addition, the growth rate of autotrophic and heterotrophic denitrifying bacteria in the denitrification tank is controlled by controlling the ratio of nitrite nitrogen and nitrate nitrogen in the wastewater supplied to the denitrification tank in the nitrification tank Can coexist.

  In addition, by controlling the amount of nitrite nitrogen in the wastewater supplied to the denitrification tank and the amount of electron donor (such as methanol) added to the denitrification tank from the amount of nitrate nitrogen, the autotrophic denitrifying bacteria It is possible to control the growth rate of heterotrophic denitrifying bacteria and coexist in more ideal conditions.

  For comparison with the present invention, FIG. 2 shows an example of a conventional treatment mode by denitrification, and FIG. 3 shows an example of a conventional treatment mode by ANAMOX reaction. In the example shown in FIG. 2, ammonia is converted into nitric acid in the nitrification tank 2, methanol is added in the denitrification tank 3 a and nitric acid is converted into nitrogen, and excess added methanol is processed in the oxidation tank 4. In the example shown in FIG. 3, ammonia is converted into nitrous acid in the nitrification tank 2, ammonia is added in the ANAMOX tank 3b, and nitrous acid and ammonia are converted into nitrogen. In this case, since no methanol is added, an oxidation tank is not necessary.

  That is, in the conventional denitrification process shown in FIG. 2, methanol as an electron donor is added to the denitrification tank 3a, but a part of ammonia is supplied to the denitrification tank 3a by bypassing the nitrification tank 2. In the conventional ANAMOX treatment shown in FIG. 3, it is conceivable that a part of ammonia is supplied to the ANAMOX tank 3b by bypassing the nitrification tank 2, but is supplied to the ANAMOX tank 3b as an electron donor. It is not considered to supply organic substances (methanol, etc.).

  In contrast to these conventional treatments, in the present invention, an appropriate amount of ammonia is bypassed through the nitrification tank 2 and directly supplied to the denitrification tank 3, and the treated water from the nitrification tank 2 is supplied by bypass in the denitrification tank 3. Ammonia nitrogen-containing wastewater was added under conditions where organic substances such as an electron donor (methanol etc.) were added (under conditions where organic substances such as an electron donor (methanol etc.) were present) and independently The denitrification treatment is performed under conditions where the nutritional denitrifying bacteria and the heterotrophic denitrifying bacteria coexist appropriately. In other words, the denitrification process and the ANAMOX process can proceed without interfering with each other. The amount of raw water supplied to the bypass line is preferably 20 to 60%. By making this range, coexistence processing can be performed more stably.

4 and 5 show an example of a biological denitrification apparatus suitable for carrying out the present invention.
For example, granule (sludge granule) or microbial carrier of heterotrophic or autotrophic denitrifying bacteria which are denitrifying microorganisms is added to the denitrification tank 3, and the carrier is installed with a simple device structure. Wastewater treatment becomes possible with reduced cost and construction period. In addition, the structure of the apparatus is simple and maintenance is easy, and in applying this method to existing equipment, it is sufficient to add a carrier and the improvement is easy.

  As the carrier, sponges, gels, plastic molded articles, various granules (denitrification granules, nitrification granules, ANAMOX granules, etc.) and the like can be used. Preferably, a hydrophilic polyurethane sponge or polyvinyl alcohol (PVA) gel can be used. In the example shown in FIG. 4, the hydrophilic polyurethane sponge carrier 5 is used, and in the example shown in FIG. 5, the hydrophilic polyurethane sponge carrier 5 and the PVA gel carrier 6 are used. In addition, in view of the characteristics that anaerobic microorganisms reduce nitric acid to nitrous acid and denitrify the nitrous acid using ANAMMOX bacteria in this method, both bacteria are present in the same carrier and nitrous acid can be easily transferred. A carrier that combines materials that easily adhere to each bacterium may be used.

  In addition, as a means for flowing in the biological denitrification tank 3, a method of causing flow by installing an underwater stirrer 7 (illustrated in FIG. 4) or an underwater pump 8 (illustrated in FIG. 5) is conceivable. In particular, a draft tube 9 ( By installing (illustrated in FIG. 5), strong agitation can be obtained with lower energy.

  Tables 1 to 3 show the test results of the denitrification method using the PVA gel and the hydrophilic polyurethane sponge carrier (Test Nos. 1 to 5). Specifically, the test conditions are shown in Table 1 (circles indicate that they exist), and a solution having the composition shown in Table 2 is prepared in a sealable container, and the gel and carrier described above are prepared. Was added to the aqueous solution so that the total volume ratio would be 5% and 10%, respectively, and then added as seed sludge for attaching autotrophic denitrifying bacteria and heterotrophic denitrifying bacteria to the carrier. Thereafter, the inside of the container was sealed with nitrogen gas to make anaerobic conditions, and the inside of the container was stirred by shaking the container several times a day. And the solution in a container was extract | collected in nitrogen atmosphere so that oxygen might not be touched every predetermined time, and each density | concentration of ammonia nitrogen, nitrate nitrogen, and nitrite nitrogen was measured. In addition, indophenol blue absorptiometry (JIS (1998), K0102, P145) was used for measuring ammonia nitrogen, and ion chromatography was used for measuring nitrate nitrogen and nitrite nitrogen.

  As a result, as shown in Table 3, in the system where autotrophic denitrifying bacteria (ANAAMOX bacteria) and heterotrophic denitrifying bacteria coexist in the presence of a carrier, the concentration of nitric acid and ammoniacal nitrogen is increased by adding methanol. (Table 6, No. 4, No. 5), it was confirmed that biological nitrogen removal removes ammonia nitrogen and nitrate nitrogen simultaneously.

  The present invention can be applied to biological denitrification treatment of ammoniacal nitrogen-containing wastewater in all fields such as the semiconductor manufacturing field.

It is a schematic block diagram of the waste water treatment equipment for enforcing the method concerning one example of the present invention. It is a schematic block diagram which shows an example of the conventional denitrification apparatus. It is a schematic block diagram which shows an example of the processing apparatus by ANAMMOX reaction. It is a schematic perspective view which shows an example of the biological denitrification apparatus suitable for implementation of this invention. It is a schematic perspective view which shows another example of the biological denitrification apparatus suitable for implementation of this invention.

Explanation of symbols

1 Wastewater containing ammonia nitrogen 2 Nitrification tank 3 Denitrification tank 4 Oxidation tank 5 Hydrophilic polyurethane sponge carrier 6 PVA gel carrier 7 Submerged agitator 8 Submersible pump 9 Draft tube B Bypass line

Claims (8)

A biological treatment method for ammoniacal nitrogen-containing wastewater,
A wastewater supply step of supplying at least a part of the wastewater to be treated directly to the denitrification tank and supplying the remaining wastewater not supplied to the denitrification tank to the nitrification tank;
A nitrification process for nitrating the wastewater supplied to the nitrification tank;
Electron donors in the denitrification tank are ammoniacal nitrogen in the wastewater that has been directly supplied to the denitrification tank and nitrate nitrogen that has been nitrated in the nitrification step in the wastewater that is supplied from the nitrification tank to the denitrification tank. A denitrification step of denitrifying by supplying
A biological denitrification method comprising:   The biological denitrification method according to claim 1, wherein a fluidized bed biological treatment apparatus is used in the denitrification step.   The biological denitrification method according to claim 1 or 2, wherein a fluidized bed biological treatment apparatus is used in the nitrification step.   The biological denitrification method according to claim 2 or 3, wherein at least one of a sponge, a gel, a granule, and a plastic molded product is used as a biological carrier in the fluidized bed biological treatment apparatus. A biological treatment apparatus for ammonia-containing nitrogen-containing wastewater,
A waste water supply means for supplying at least part of the waste water to be treated directly to the denitrification tank by bypassing the nitrification tank and supplying the remaining waste water not supplied to the denitrification tank to the nitrification tank;
Nitrification means for nitrating the wastewater that has been supplied to the nitrification tank;
Electron donors in the denitrification tank are ammonia nitrogen in the wastewater that has been directly supplied to the denitrification tank and nitrate nitrogen that has been nitrated by the nitrification means in the wastewater that is supplied from the nitrification tank to the denitrification tank. Denitrification means for denitrification by supplying
A biological denitrification apparatus comprising:   The biological denitrification apparatus according to claim 5, wherein a fluidized bed biological treatment apparatus is used as the denitrification means.   The biological denitrification apparatus according to claim 5 or 6, wherein a fluidized bed biological treatment apparatus is used as the nitrification means.   The biological denitrification apparatus according to claim 6 or 7, wherein at least one of a sponge, a gel, a granule, and a plastic molded product is used as a biological carrier in the fluidized bed biological treatment apparatus.

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