JP2007007557A - Waste water treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waste water treatment apparatus capable of efficiently carrying out nitrite oxidation anaerobic denitrification treatment with a simple apparatus configuration even if the waste water has high BOD and high DO. <P>SOLUTION: The waste water treatment apparatus comprises an aerobic treatment part 13 which oxidizes an ammonium ion in the waste water into a nitrite ion by aerating the waste water, and an anaerobic treatment part 14 which makes the reaction of the generated nitrite ion and the ammonium ion in the waste water in an anaerobic state to generate nitrogen gas wherein the aerobic treatment part 13 and the anaerobic treatment part 14 are partitioned by a partition member 12 formed of, for example, any of a sponge type molding, a filter cloth, a semipermeable membrane and a microfiltration membrane capable of passing the ammonium ion and the nitrite ion without substantially generating convection of water. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wastewater treatment apparatus, and more particularly, to a wastewater treatment apparatus that performs removal treatment of ammonia nitrogen contained in wastewater at a high concentration by partial nitritation and anaerobic ammonia oxidation.

  In the water treatment technology, a circulation nitrification denitrification method has been widely known as a nitrogen removal technology in ammonia-containing wastewater. However, this technology has a problem that a large installation area is required, a cost of equipment such as a circulation pump is high, and a hydrogen donor as a nutrient source in denitrification must be added. There is.

  However, in recent years, in the treatment method of organic waste liquid containing ammonia nitrogen, ammonia nitrogen in the waste liquid is partially nitrified by nitrifying bacteria, and the resulting nitrite is obtained by anaerobic ammonia oxidation method. A treatment method for denitrification is known.

  This technology not only reduces the amount of aeration required for nitrification due to partial oxidation from ammonia to nitrous acid during the nitrification reaction. In addition, the microorganism involved in this reaction is a self-trophic bacterium. Therefore, there is an advantage that the amount of generated sludge is considerably reduced as compared with the conventional method (for example, see Patent Document 1).

  Furthermore, as a technique using this anaerobic ammonia oxidation method, a SNAP method and a Canon method have been proposed. The SNAP method is a method for removing ammonia in a single tank, generating convection in the tank by aeration from the center of the bottom of the tank, and attaching ammonia-oxidizing bacteria, which are aerobic microorganisms, to the surface of the attached fixed carrier installed in the periphery of the tank. In addition, anaerobic ammonia-oxidizing bacteria are allowed to inhabit anaerobic parts inside the carrier, and nitrification and denitrification are performed by the action of both. On the other hand, the Canon method is a method in which half of the ammonia in the inflowing water is converted to nitric acid by the action of ammonia-oxidizing bacteria by supplying oxygen limitedly to the reactor, and nitrogen is removed in one tank.

However, both of these methods have a problem that the inside of the reactor is low DO and anaerobic ammonia-oxidizing bacteria are given priority, so the nitrite production rate is low and the denitrification rate is also reduced. . In addition, it is effective for wastewater with a low C / N ratio, but it is difficult to apply to wastewater with high BOD.
JP 2005-74253 A

  As described above, the denitrification treatment in one tank has various problems as in the SNAP method and the Canon method, but the method described in Patent Document 1 has the above-described advantages. However, it is necessary to install a plurality of treatment tanks, and there are problems in terms of equipment cost, as well as problems such as bringing in BOD and DO, and fine adjustment of the nitrous acid / ammonia concentration ratio.

  Accordingly, an object of the present invention is to provide a wastewater treatment apparatus that can efficiently perform nitritation anaerobic denitrification treatment with a simple apparatus configuration even with high BOD and high DO wastewater.

  In order to achieve the above object, a wastewater treatment apparatus of the present invention is a wastewater treatment apparatus for removing ammonia nitrogen contained in wastewater. The wastewater is introduced and aerated to convert ammonium ions in the wastewater to nitrous acid. An aerobic treatment unit that oxidizes to ions, an anaerobic treatment unit that reacts the generated nitrite ions and ammonium ions in the wastewater in an anaerobic state to generate nitrogen gas, and the aerobic treatment unit and the anaerobic part A partition member capable of allowing the ammonium ions and nitrite ions to pass through without substantially causing convection of water between the processing section, for example, any of sponge-type molded bodies, filter cloths, semipermeable membranes, and microfiltration membranes It is characterized by partitioning with one or more partition members.

  According to the waste water treatment apparatus of the present invention, since water (liquid) does not convect (circulate) between the aerobic treatment unit and the anaerobic treatment unit, it is possible to minimize the introduction of BOD and DO into the anaerobic treatment unit, and high efficiency. Can be operated at high load.

  1 and 2 show a first embodiment of the wastewater treatment apparatus of the present invention, FIG. 1 is a schematic system diagram, and FIG. 2 is an explanatory view of a partition member. This wastewater treatment apparatus is configured such that the inside of a treatment tank 11 is partitioned into an aerobic treatment unit 13 and an anaerobic treatment unit 14 by a partition member 12, and oxygen is supplied to the bottom of the aerobic treatment unit 13. An air diffuser 15 is provided for this purpose. The aerobic treatment unit 13 is provided with waste water introduction means 16. In the case of continuously injecting waste water, the treated water deriving means 17 is preferably provided in the anaerobic treatment section 14, and in the case of a so-called batch treatment system in which waste water is introduced intermittently, the treated water deriving means is an aerobic treatment section. 13 is preferable.

  The partition member 12 is a material in which convection of water is substantially suppressed and ions can pass and move mainly only by diffusion, for example, a sponge-shaped molded body, a filter cloth, a semipermeable membrane, or a microfiltration membrane. Or it is formed by the material which needs to apply pressure in order to let water pass like the thing which combined these, ie, the material which has water flow resistance. That is, since ions are moved to the aerobic processing unit 13 and the anaerobic processing unit 14 by the diffusion phenomenon to suppress the movement of water, oxygen in the water hardly moves to the anaerobic processing unit 14, It prevents that the anaerobic process part 14 will be in an aerobic state. Moreover, since the diffusion rate of the organic compound having a large molecular weight compared to ions is relatively slow, it is possible to suppress the movement of the BOD component in the aerobic processing unit 13 to the anaerobic processing unit 14.

The material and shape of the partition member 12 can be selected as appropriate, but the water flow resistance needs to be a certain level or more. Here, when representing the flow resistance in the unit area ^{[m 2]} passing water amount _{Q 10} per partition member 12 at the pressure 10 kPa, passing water _{Q 10} of the preferred partitioning member 12 is in 500L / min / ^{m 2} or less Particularly preferred is 100 L / min / m ² . If passing water Q ₁₀ is 500L / min / m ² or less, is resistance to fluid passage for suppressing the convection is ensured, it is possible to move the ions preferentially. Further, the surface area of the partition member 12 will vary depending properties such as the material and waste, nitrogen load 1 kg-N / day surface area 10 m ² or more preferably, 50 m ² or more is particularly preferable.

  On the other hand, nitrite ions (nitrite nitrogen) generated by oxidation of ammonium ions (ammonia nitrogen) dissolved in water by aeration treatment from the air diffuser 15 in the aerobic treatment unit 13 and unreacted The ammonium ions pass through the partition member 12 by diffusion according to the difference in ion concentration on both sides of the partition member 12 and move from the aerobic processing unit 13 to the anaerobic processing unit 14. The ammonium ions and nitrite ions that have moved to the anaerobic treatment unit 14 generate nitrogen gas by anaerobic ammonia oxidation, and the nitrogen gas is bubbled out of the system.

  The aerobic treatment unit 13 which is a nitritation means is configured to nitrite ammonia nitrogen by a nitrite bacterium so that nitric acid is not produced, thereby producing ammonium nitrite. As such nitritation means, a means for bringing ammonia nitrogen and nitrite bacteria into contact with each other under aerobic condition to nitrite ammonia nitrogen can be employed. Nitrite bacteria may be in a floating state, or may be in a state of being supported on a carrier such as a sponge, a resin molded body, or activated carbon.

  The nitrite bacteria used in the aerobic treatment unit 13 are bacteria conventionally used for nitritation of ammonia nitrogen, and oxidize ammonia nitrogen under aerobic condition to convert to nitrite nitrogen. Bacteria to do. Such nitrite bacteria can be generated by oxidizing a liquid containing ammoniacal nitrogen under aerobic condition, but the sludge collected from the aerobic treatment means of organic wastewater treatment is used as it is or filled. It can be used attached to a layer. Normally, the inside of the aerobic processing unit 13 is in a substantially uniform mixed state due to aeration, but when the agitation force due to aeration is insufficient, agitation means such as an agitator and a circulation pump can be provided.

  The anaerobic treatment unit 14 which is a denitrification means is configured to denitrify the nitrite solution by reacting ammonia nitrogen and nitrite nitrogen with anaerobic ammonia oxidizing bacteria. Since anaerobic ammonia oxidizing bacteria are anaerobic, a structure in which oxygen is not supplied is employed. Anaerobic ammonia oxidizing bacteria may be used as floating sludge, or may be used in a state of being supported on a carrier or in a granular state such as granules. In such denitrification means, a liquid containing ammonia nitrogen and nitrite nitrogen is brought into contact with anaerobic ammonia oxidizing bacteria, ammonia nitrogen and nitrite nitrogen are reacted, converted into nitrogen gas, and dehydrated. Nitrogen is performed.

  The anaerobic ammonia oxidizing bacterium used in the anaerobic treatment unit 14 is a bacterium belonging to Plantomycetes, and is an autotrophic bacterium, unlike the heterotrophic denitrifying bacterium used for conventional denitrification. For this reason, at the time of denitrification, it is not necessary to add a nutrient source such as methanol, which is necessary for conventional denitrifying bacteria. In addition, anaerobic ammonia-oxidizing bacteria react ammonia nitrogen and nitrite nitrogen directly to convert them into nitrogen gas, so ammonia ammonia and nitrite nitrogen can be removed at the same time, and harmful waste can be removed. It has the feature of not generating.

  Furthermore, anaerobic ammonia-oxidizing bacteria use ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor to react ammonia nitrogen and nitrite nitrogen directly to convert them into nitrogen gas. Nitrate nitrogen is not necessary, and the presence of oxygen reduces the denitrification activity of anaerobic ammonia oxidizing bacteria. Therefore, the anaerobic treatment unit 14 should be supplied with a liquid (waste water) that is substantially free of oxygen. Moreover, since anaerobic ammonia oxidizing bacteria cannot assimilate nitric acid, it is preferable that nitrate nitrogen is not substantially generated in the aerobic treatment unit 13. Since oxygen is consumed by bacteria while moving from the partition member 12 to the anaerobic treatment unit 14, the amount of aeration at which dissolved oxygen disappears at the inlet portion of the anaerobic treatment unit 14 can be easily set.

  The anaerobic ammonia oxidizing bacteria react ammonia nitrogen and nitrite nitrogen at a molar ratio of 1: 1.32. However, the wastewater supplied to the anaerobic treatment unit 14 is nitrite nitrogen rather than ammonia nitrogen. The nitrous acid produced | generated in the aerobic process part 13 will pass the partition member 12 at any time, and will be in the state removed by the anaerobic process part 14. FIG.

  The waste water supplied to the aerobic treatment part 13 and the anaerobic treatment part 14 has an ammoniacal nitrogen concentration of 50 to 3000 mg / L, preferably 80 to 2000 mg / L, more preferably 300 to 1000 mg / L. The nitrogen concentration is 10 to 300 mg / L, preferably 20 to 200 mg / L, more preferably 30 to 100 mg / L, and pH 6.5 to 8.0, preferably pH 6.7 to 7.5. Is desirable.

  The processing temperature in the aerobic processing unit 13 and the anaerobic processing unit 14 may be room temperature or higher, particularly 30 ° C. or higher, and may be heated at low temperatures. Moreover, a pH adjuster, a nutrient, and other additives can be inject | poured as needed. Furthermore, when sludge is generated excessively, a part of it may be extracted and discarded.

  In the anaerobic treatment unit 14, as described above, the anaerobic ammonia oxidizing bacteria react with ammonia nitrogen and nitrite nitrogen in the nitrite and convert it to nitrogen gas for denitrification. At this time, since the presence of dissolved oxygen decreases the activity of the anaerobic ammonia oxidizing bacteria, it is desirable that the dissolved oxygen does not flow into the anaerobic treatment unit 14. As shown in the present embodiment, since the dissolved oxygen is inhibited from flowing directly into the anaerobic treatment unit 14 by interposing the partition member 12, the anaerobic treatment can be performed at a larger flow rate than before. Reaction by anaerobic ammonia oxidizing bacteria is shown in the following reaction formula (1), and ammonia nitrogen and nitrite nitrogen react at about 1: 1.32.

NH 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)

  In the above process, the ammonia nitrogen is sublimated under conditions where nitric acid is not generated in the aerobic treatment unit 13 by treating the liquid of high ammonia nitrogen concentration and nitrite nitrogen in the aerobic treatment unit 13 and the anaerobic treatment unit 14. Nitrification can be performed, and denitrification can be performed with high efficiency in the anaerobic treatment unit 14 in the absence of oxygen.

  In the aerobic processing unit 13, it is not necessary to generate a nitrite having an ammonia nitrogen: nitrite nitrogen molar ratio of approximately 1: 1.32, and the generated nitrite ions pass through the partition member 12. Then, since it moves to the anaerobic processing part 14 sequentially, accumulation of nitrite ions does not occur. In addition, it is only necessary to oxidize ammonia nitrogen to nitrite nitrogen, and it is not necessary to oxidize nitrite nitrogen to nitrate nitrogen as in the past, so sludge containing nitrifying bacteria is unnecessary and supports nitrifying bacteria. Therefore, the processing tank 11 can be reduced in size and the amount of oxygen necessary for oxidation (aeration amount) can be reduced.

  In the anaerobic treatment unit 14, ammonia nitrogen and nitrite nitrogen are reacted at a molar ratio of approximately 1: 1.32 for denitrification. Therefore, no nutrient source such as methanol is required, and denitrification is performed efficiently. be able to. Moreover, it is harmless nitrogen gas produced | generated by denitrification reaction, and can be discarded as it is. Since nitrite bacteria and anaerobic ammonia-oxidizing bacteria have a low growth rate, the amount of sludge increase is small and the amount of surplus sludge generated is small.

  FIG. 3 is a schematic system diagram showing a second embodiment of the wastewater treatment apparatus of the present invention. Since the denitrification process is performed in the same manner as in the first embodiment, detailed description is omitted.

  The wastewater treatment apparatus shown in the present embodiment includes an aerobic treatment tank 21 serving as an aerobic treatment part and an anaerobic treatment tank 22 serving as an anaerobic treatment part via a communication part 23 formed of the same material as the partition member. The fluid in the anaerobic treatment tank 22 is circulated into the communication portion 23 by the pump 24 via the circulation path, and the anaerobic liquid inside the communication portion 23 and the external aerobic liquid are communicated. Ammonium ions and nitrite ions are formed to move. Thus, the reaction efficiency in the anaerobic treatment tank 22 can be improved by generating a fluid flow in the anaerobic treatment tank 22 by the pump 24.

1 is a schematic system diagram showing a first embodiment of a wastewater treatment apparatus of the present invention. It is explanatory drawing of a partition member. It is a schematic system diagram which shows the 2nd form example of the waste water treatment apparatus of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Processing tank, 12 ... Partition member, 13 ... Aerobic processing part, 14 ... Anaerobic processing part, 15 ... Air diffuser, 16 ... Waste water introduction means, 17 ... Treated water derivation means, 21 ... Aerobic processing tank, 22 ... Anaerobic treatment tank, 23 ... Communication part, 24 ... Pump

Claims (2)

  In a wastewater treatment apparatus for removing ammonia nitrogen contained in wastewater, an aerobic treatment unit that introduces the wastewater, aeration treatment to oxidize ammonium ions in the wastewater to nitrite ions, and generated nitrite ions And an anaerobic treatment part that reacts ammonium ions in wastewater in an anaerobic state to generate nitrogen gas, and substantially does not cause convection of water between the aerobic treatment part and the anaerobic treatment part. A wastewater treatment apparatus characterized by being partitioned by a partition member through which the ammonium ions and nitrite ions can pass.   The wastewater treatment apparatus according to claim 1, wherein the partition member is at least one of a sponge-type molded body, a filter cloth, a semipermeable membrane, and a microfiltration membrane.

Images