JP4203853B2 - Method for producing nitrite-type nitrification carrier - Google Patents

Description

  The present invention relates to a method for producing a nitrite-type nitrification carrier formed by preferentially accumulating ammonia-oxidizing bacteria that nitrify ammoniacal nitrogen to nitrite.

  Conventionally, biological treatment in which wastewater or sewage is treated with microorganisms is widely adopted because of its relatively low cost. However, some microorganisms have a slow growth rate, are easily poisoned, or are difficult to grow in the environment, and may not necessarily be an efficient method. Therefore, in order to actively form an environment in which microorganisms are easy to propagate, a treatment method has already been put into practical use by using an immobilized microorganism carrier in which specific microorganisms are comprehensively immobilized in advance.

Patent Document 1 proposes the use of a nitrite type nitrification carrier as a nitrification treatment for nitrifying ammoniacal nitrogen contained in water or air to nitrous acid under aerobic conditions. This nitrite type nitrification carrier is formed by heat-treating the collected activated sludge after comprehensively immobilizing it with a monomer or a prepolymer. Thereby, the nitrite type nitrification carrier can preferentially accumulate ammonia oxidizing bacteria, so that nitrite type nitrification treatment can be performed on ammoniacal nitrogen.
JP 2003-2111177 A

  However, since the nitrite-type nitrification carrier of Patent Document 1 is manufactured by heat treatment after entrapping and immobilization, moisture is released from the carrier due to heat during the heat treatment and contracts. There is a drawback that handling becomes worse when bagging and the like. Further, when the contracted nitrite-type nitrification carrier is put into a treatment tank and wastewater treatment is performed, there is a drawback that it flows out of the screen provided in the treatment tank or clogs the screen. Furthermore, since the carrier is used semi-permanently in the treatment tank, it is required that the carrier has high strength. However, the nitrite type nitrification carrier of Patent Document 1 is still not sufficient in terms of carrier strength. .

  The present invention has been made in view of such circumstances, and is capable of performing nitrite-type nitrification, and also has the disadvantages of conventional nitrite-type nitrification carriers such as carrier handling, screen clogging, and insufficient carrier strength. An object of the present invention is to provide a method for producing a nitrite-type nitrification carrier that can be eliminated.

In order to achieve the above object, claim 1 of the present invention is a method for producing a nitrite-type nitrification carrier in which ammonia-oxidizing bacteria that nitrify ammoniacal nitrogen to nitrite are preferentially accumulated. Nitrogen-oxidizing bacteria-containing complex microbial sludge for heat treatment temperatures in the range of 50 ° C to less than 60 ° C for 60 minutes or more, and heat treatment temperatures in the range of 60 ° C to less than 80 ° C. For 40 minutes or more, when the heat treatment temperature is in the range of 80 ° C. or higher and 100 ° C. or lower, heat treatment is performed for 20 minutes or longer, and the heat-treated sludge is comprehensively fixed in either a monomer or a prepolymer.

  Specific examples of complex microbial sludge having nitrification performance containing at least ammonia-oxidizing bacteria and nitrite-oxidizing bacteria include activated sludge from a treatment plant that treats sewage and factory wastewater, lakes, rivers, and sea bottom mud. There is soil on the surface.

  According to claim 1, in the production of a nitrite type nitrification carrier, after heat treatment of sludge of a complex microbial system having a nitrification performance containing at least ammonia oxidizing bacteria and nitrite oxidizing bacteria in a range of 40 to 100 ° C, It was made to carry out comprehensive fixation to either a monomer or a prepolymer. This makes it possible to produce a nitrite-type carrier that sterilizes nitrite-oxidizing bacteria and preferentially accumulates ammonia-oxidizing bacteria, and heat treatment is not performed after the sludge is comprehensively fixed as in the past. The carrier can be prevented from shrinking due to the heat of treatment. Therefore, the handling of the carrier can be improved while maintaining the nitrite type nitrification performance, and the carrier is not clogged in the screen of the treatment tank in which the carrier is introduced to perform the nitrification treatment. Furthermore, since the entrapment is carried out after the heat treatment, the temperature of the activated sludge during the entrapment immobilization becomes high, so that it is easy to bind to the monomer or prepolymer gel, and the polymerization is carried out quickly and strongly during the polymerization reaction. Thereby, since the carrier strength can be increased, damage due to impact and shrinkage due to reheating can be suppressed. As described above, the nitrite type nitrification carrier produced by the production method of the present invention can perform nitrite type nitrification, and the conventional nitrite type such as carrier handling, screen clogging, and lack of carrier strength. The disadvantages of the nitrification carrier can be eliminated.

Then, in the present invention, heat treatment, heat treatment temperature is 50 ° C or more, 60 ° carried out over 60 minutes in a range of less than C, the heat treatment temperature is 60 ° C or more, 40 minutes or more in the range of less than 80 ° C When the heat treatment temperature is in the range of 80 ° C. or higher and 100 ° C. or lower, it is performed for 20 minutes or longer.

By performing the pressurized heat treatment under the above conditions, carried out with possible integration of ammonia oxidizing bacteria to eliminate the nitrite oxidizing bacteria, it is possible to prevent deactivation of the ammonium oxidizing bacteria due to excessive heating, the nitrite type nitrification efficiently A carrier can be produced.

  As described above, according to the manufacturing method of the nitrite type nitrification carrier according to the present invention, nitrite type nitrification can be performed, and the conventional nitrite such as carrier handling, screen clogging, and lack of carrier strength. The drawbacks of the mold nitrification carrier can be eliminated.

  The preferred embodiments of the method for producing a nitrite type nitrification carrier according to the present invention will be described in detail below with reference to the accompanying drawings.

  The nitrite-type nitrification carrier of the present invention is a complex microbial system in which a large number of microorganisms are mixed, such as lakes, rivers, sea bottom mud, surface soil, or activated sludge in treatment plants treating sewage and factory wastewater. Sludge, particularly sludge containing a large amount of nitrifying bacteria such as ammonia-oxidizing bacteria and nitrite-oxidizing bacteria, is used as a microbial source, and this complex microbial sludge is comprehensively fixed to a monomer or prepolymer, and then 40 to 100 ° C, preferably 50 In the range of 40 to 100 ° C, preferably in the range of 50 to 90 ° C when heat-treated within the range of ~ 90 ° C, or when the monomer or prepolymer is polymerized and fixed in the presence of sludge of a complex microbial system It is manufactured by heat treatment in the inside.

  That is, the present invention is not a heat treatment during polymerization in a state in which complex microbial sludge is encapsulated with a monomer or prepolymer, or a gelation reaction that is encapsulated with a monomer or prepolymer. It is important to polymerize with a monomer or a prepolymer and fix them inclusive.

  As a result, among the multiple types of microorganisms mixed in the sludge of the complex microbial system, ammonia-oxidizing bacteria that nitrify ammonia nitrogen to nitrite preferentially accumulate, and nitrite-oxidizing bacteria that oxidize nitrite to nitric acid. Accumulation can be suppressed. At this time, the microorganisms in the sludge of the complex microorganism system are easily solubilized by the heat of the heat treatment, but since the entrapping is immediately performed, a habitat space for the microorganisms after entrapping can be formed. Moreover, since the activated sludge is heated by heat processing by carrying out comprehensive fixation after heat processing, the bond strength by superposition | polymerization can be strengthened. As a result, the strength of the manufactured carrier can be increased, so that a carrier with good handling that is less damaged by impact and less heat-shrinkable by reheating can be provided.

  Monomers or prepolymers used in the production of the nitrite type nitrification carrier of the present invention include monomethacrylates, monoacrylates, dimethacrylates, diacrylates, trimethacrylates, triacrylates, tetraacrylates, urethane acrylates. In addition, epoxy acrylates, polyvinyl alcohol, acrylamide, photocurable polyvinyl alcohol, photocurable polyethylene glycol, photocurable polyethylene glycol polypropylene glycol prepolymer, and the like can be used.

  In the method for producing a nitrite type nitrification carrier of the present invention, the following first wastewater treatment test was conducted in order to investigate the nitrite type nitrification performance by heat treatment.

  For the carrier to be tested, excess sludge from the sewage treatment plant was collected in a beaker, and the beaker was immersed in a hot water bath and heated at 60 ° C. for 60 minutes. The sludge after the heat treatment was mixed with a polyethylene glycol prepolymer, and potassium persulfide was added as a polymerization initiator for polymerization. The gel after polymerization was shaped into a 3 mm square cube to produce a nitrite type nitrification carrier (hereinafter referred to as the carrier of the present invention). In addition, what was comprehensively fixed so that the sludge content of the carrier of the present invention was 2% and the prepolymer content was 10% was used.

  As a comparative example, a carrier (hereinafter referred to as a comparative carrier) in which the activated sludge described above was mixed with a polyethylene glycol-based prepolymer without heat treatment and polymerized by adding potassium persulfide was used.

  The wastewater treatment conditions were a water temperature of 20 ° C., a hydraulic retention time (HRT) of 6 hours, and a DO of 7 or more. As the test wastewater, synthetic wastewater containing 100 mg / L of ammoniacal nitrogen was used. The composition of synthetic wastewater is shown in Table 1.

その結果を図１に示す。図１は試験結果を示したグラフであり、図１（Ａ）は本発明担体を使用した場合、図１（Ｂ）は比較担体を使用した場合である。なお、各グラフにおいて、■は総窒素濃度を示し、□は亜硝酸濃度を示し、○は硝酸性窒素濃度を示し、●はアンモニア性窒素濃度を示している。

The result is shown in FIG. FIG. 1 is a graph showing test results. FIG. 1 (A) shows a case where the carrier of the present invention is used, and FIG. 1 (B) shows a case where a comparative carrier is used. In each graph, ■ represents the total nitrogen concentration, □ represents the nitrous acid concentration, ○ represents the nitrate nitrogen concentration, and ● represents the ammonia nitrogen concentration.

  As shown in FIG. 1 (A), in the wastewater treatment using the carrier of the present invention, ammonia oxidation activity was confirmed from the start to the second to third weeks, and the production of nitrous acid was confirmed. Thereafter, wastewater treatment was carried out for 2 months or more, but no nitric acid was produced. On the other hand, as shown in FIG. 1 (B), when wastewater treatment was performed with a comparative carrier, production of nitric acid was confirmed from the third week onward, and it was found that nitrite-oxidizing bacteria were present. As described above, it was confirmed that the carrier of the present invention produced by entrapping and immobilizing activated sludge after heat treatment performs nitrite type nitrification.

  Next, in order to investigate the relationship between the heat treatment temperature and the heat treatment time in the method for producing a nitrite type nitrification carrier of the present invention, a second wastewater treatment test was conducted.

  The carrier to be tested is the heat treatment of the activated sludge used in the first wastewater treatment test at 40 ° C, 50 ° C, 60 ° C, 70 ° C, 80 ° C, 90 ° C, 100 ° C. The heat treatment time was 20 minutes, 40 minutes, 60 minutes, and 120 minutes under each temperature condition. Each activated sludge after heat treatment was mixed with a polyethylene glycol-based prepolymer, and a carrier obtained by polymerizing by adding potassium persulfide was used. Moreover, the wastewater to be used was a synthetic wastewater containing 40 mg / L of nitrogen nitrite. In the wastewater treatment test, 50 mg of carrier was introduced into 450 ml of synthetic wastewater, wastewater was treated by continuous aeration, and the nitric acid concentration in the exchanged treated water was measured by exchanging every day.

  The result is shown in FIG. FIG. 2 is a graph showing the nitric acid concentration in the treated water at each heat treatment temperature and each heat treatment time.

  As can be seen from FIG. 2, the activity was heat-treated at 40 ° C. and 50 ° C. for 60 minutes or longer, at 60 ° C. and 70 ° C. for 40 minutes or longer, and at 80 ° C., 90 ° C. and 100 ° C. for 20 minutes or longer. In the sludge, nitric acid was hardly detected, and nitrite type nitrification could be performed on wastewater.

  From this, the heat treatment of a plurality of microbial sludges is performed at 40 ° C or more and less than 60 ° C for 60 minutes or more, at 60 ° C or more and less than 80 ° C for 40 minutes or more, at 80 ° C or more, and at 100 ° C or less, 20 It was confirmed that a nitrite-type nitrification carrier that performs nitrite-type nitrification can be produced by carrying out the treatment for more than 5 minutes.

  The carrier of the present invention that uses activated sludge from a treatment plant that treats sewage and factory wastewater, sludge from different collection sites such as lakes, rivers, sea bottom mud, surface soil, etc. And, compared with the conventional carrier that performs heat treatment after comprehensively fixing sludge as in Patent Document 1, the carrier handling property, the clogging avoidance property of the screen of the treatment tank, and the carrier strength are compared. It was superior to conventional carriers in all of the handling properties of the carrier, the ability to avoid clogging of the processing tank screen, and the strength of the carrier.

The graph which showed the relationship between the heat treatment of the excess sludge in the manufacturing method of the nitrite type nitrification support | carrier of this invention, and the nitrite type nitrification ability The graph which showed the relationship of the heat processing temperature and heat processing time in the manufacturing method of the nitrite type nitrification support | carrier of this invention, and the digestive capacity of a nitrite type

Claims (1)

In a method for producing a nitrite-type nitrification carrier that preferentially accumulates ammonia-oxidizing bacteria that nitrify ammonia nitrogen to nitrite,
A complex microbial sludge having nitrification performance containing at least ammonia-oxidizing bacteria and nitrite-oxidizing bacteria has a heat treatment temperature of 50 ° C. or more and less than 60 ° C. for 60 minutes or more, and the heat treatment temperature is 60 ° C. or more and 80 When the temperature is less than ° C, the heat treatment is performed for 40 minutes or longer .
A method for producing a nitrite-type nitrification carrier, wherein the heat-treated sludge is entrapped and immobilized in either a monomer or a prepolymer.

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