JPWO2018155436A1 - Denitrification treatment method and denitrification treatment apparatus - Google Patents

Abstract

Provided is a denitrification treatment method capable of improving the workability of denitrification treatment in biological treatment and realizing removal of nitrate nitrogen and / or nitrite nitrogen quickly, satisfactorily and stably over a long period of time. A method for continuously denitrifying a treatment liquid containing nitrate nitrogen and / or nitrite nitrogen, wherein the treatment liquid is passed through a container filled with a filler containing a biodegradable polymer. The step of biologically performing the denitrification treatment by causing the solution to be treated in the container to have an average residence time of 10 hours or less, and the solution to be treated contains a phosphorus compound. Denitrification treatment method.

Description

  The present invention relates to a method and apparatus for treating nitrogen compounds continuously from contaminated water containing nitrate nitrogen and / or nitrite nitrogen (hereinafter also referred to as nitrogen compounds).

  In order to harmonize human activities with the environment, it is necessary to reduce as much as possible the pollutants generated by human activities and to detoxify the generated pollutants. One of the pollutants is nitrate nitrogen and nitrite nitrogen.

  One of the methods for treating nitrate nitrogen is a biological treatment method, and a typical example is denitrification treatment using activated sludge treatment. This is a treatment method in which nitrate nitrogen and / or nitrite nitrogen is reduced to nitrogen gas and detoxified using denitrifying bacteria in an anaerobic state (denitrification reaction). This denitrification reaction utilizes the action of nitrate-respiring bacteria that use nitrate nitrogen as an electron acceptor. As a result, nitrate nitrogen passes through nitrous acid, nitrogen monoxide, and dinitrogen monoxide to nitrogen. As a result, various nitrogen compounds in the liquid to be treated are removed by being diffused into the atmosphere as nitrogen gas.

  For this denitrification reaction, an electron donor is essential, and conventionally, an inexpensive liquid electron donor such as methanol or acetic acid has been used. However, an appropriate amount is used depending on the remaining nitrate nitrogen. It is necessary to add an electron donor, which is very difficult to control. Therefore, a method is adopted in which an excess amount is added and the methanol remaining in the subsequent treatment is removed, but there is a concern about the effect of the residual methanol, for example, on the fishery equipment when considering application to aquaculture equipment, etc. Therefore, in order to surely remove the residual electron donor, the equipment cost is increased.

  In order to avoid such a problem, a method using a biodegradable solid substance as an electron donor is mentioned. Examples of this include wood chips, higher fatty acids, biodegradable polymers, and the like, and attempts have been made to solve the above-mentioned problems using the sustained release properties of electron donors.

  For example, in Patent Document 1, as a biodegradable solid electron donor, a solid-phase denitrification method using solid polylactic acid (hereinafter referred to as PLA) having improved hydrolyzability by modifying physical properties such as molecular weight. Proposals have been made. This modified PLA is said to be hydrolyzable to the extent that lactic acid can be supplied, and to adjust the rate of sustained release of lactic acid released with hydrolysis. In addition, for example, Patent Document 2 proposes a denitrification method using a microorganism-produced polyester which is a kind of biodegradable polymer as a biodegradable solid electron donor. According to this, by adding and coexisting a biodegradable polymer in general activated sludge treatment, the activity of bacteria that occurs when the organic matter contained in the liquid to be treated is insufficient, especially denitrification ability It is stated that it is possible to suppress the decrease in the above.

JP 2011-104551 A JP 2000-153293 A

  However, PLA is generally very poorly biodegradable, and has a problem that it is not suitable as a substrate for denitrification treatment as it is. For example, Patent Document 1 proposes a solid-phase denitrification method using solid PLA with improved hydrolyzability, and it is possible to adjust the sustained release rate of lactic acid released with hydrolysis. However, there was a problem with the sustainability of hydrolysis.

  Patent Document 2 proposes a method in which microorganism-produced polyester is added as an electron donor in normal activated sludge treatment to maintain the activity of bacteria, but the denitrification treatment efficiency is still insufficient. In addition, there was a problem in the stability of processing.

  In general, a nitrification treatment that oxidizes ammonia nitrogen to nitrate nitrogen and nitrite nitrogen is often carried out before the denitrification treatment, but this nitrification reaction must be carried out under aerobic conditions. For this reason, the liquid to be treated in the subsequent denitrification treatment is often in an aerobic state containing a large amount of oxygen. Therefore, in order to advance the denitrification reaction promptly, it is necessary to remove oxygen in the liquid to be treated and make it anaerobic. Therefore, in general, as the oxygen reduction treatment, the oxygen supply is shut off and allowed to stand, but there is a problem that the capacity of the tank becomes large in order to secure a sufficient time necessary for oxygen reduction.

  The present invention has been made in view of the above-mentioned problems, and improves the workability of denitrification treatment in biological treatment, and removes nitrate nitrogen and / or nitrite nitrogen quickly and satisfactorily. It is an object of the present invention to provide a denitrification method that can be stably realized over a long period of time.

  As a result of intensive studies to achieve the above object, the inventors of the present invention have made a phosphorus compound coexist in a liquid to be treated in a continuous denitrification method using a solid electron donor, By setting the average residence time to 10 hours or less, the denitrification ability can be remarkably increased, and at the same time, it is found that denitrification can be performed without any problems even in the middle temperature range where the activity is relatively low, and the present invention is completed. It came.

  That is, the present invention provides the following inventions, for example.

[1] A method for continuously denitrifying a liquid to be treated containing nitrate nitrogen and / or nitrite nitrogen,
Including a step of biologically performing the denitrification treatment by passing the treatment target liquid through a container filled with a filler containing a biodegradable polymer, and an average residence time of the treatment target liquid in the container For 10 hours or less, and the liquid to be treated contains a phosphorus compound.

  [2] The denitrification method according to [1], wherein the solution after passing through the container has a dissolved oxygen concentration of 5 mg / L or less.

  [3] The denitrification treatment method according to [1] or [2], wherein the biodegradable polymer is an aliphatic polyester.

  [4] The denitrification method according to [3], wherein the aliphatic polyester is poly (3-hydroxyalkanoate).

  [5] The container according to any one of [1] to [4], wherein the container is a container in which the filler is filled with a filling degree of 30 vol% or more with respect to the capacity (100 vol%) of the container. Denitrification treatment method.

[6] An apparatus for continuously denitrifying a liquid to be treated containing nitrate nitrogen and / or nitrite nitrogen,
A denitrification treatment unit that biologically denitrifies the liquid to be treated by passing the solution through the interior; the denitrification treatment unit is filled with a filler containing a biodegradable polymer;
The dissolved oxygen concentration of the liquid at the outlet of the denitrification processing unit is monitored, and the flow rate of the processing target liquid at the inlet of the denitrification processing unit is controlled so that the dissolved oxygen concentration is maintained at 5 mg / L or less. A denitrification processing apparatus comprising a mechanism.

  Since this invention has the said structure, removal of a nitrogen compound can be implement | achieved rapidly and stably.

It is the schematic which shows an example of the denitrification process part in the method or apparatus of this invention. It is a figure which shows the image of distribution of the dissolved oxygen concentration in the denitrification process part in the method or apparatus of this invention. It is the schematic of the denitrification processing apparatus produced and used in the Example.

  In order to biologically treat nitrate nitrogen or nitrite nitrogen, which is a kind of nitrogen compound, in general, denitrifying bacteria are used in anaerobic condition, and nitrate nitrogen or nitrite nitrogen is converted to nitrogen gas. The method of reducing to is used. This denitrification reaction utilizes the action of nitrate-respiring bacteria that use nitrate nitrogen as an electron acceptor. As a result, nitrate nitrogen passes through nitrous acid, nitrogen monoxide, and dinitrogen monoxide to nitrogen. As a result, various nitrogen compounds in the liquid to be treated are removed by being diffused into the atmosphere as nitrogen gas.

  This denitrification reaction requires an electron donor, but in the present invention, a biodegradable polymer is used as a solid electron donor. By using the biodegradable polymer, it becomes possible for the microorganism to decompose the biodegradable polymer as necessary, and to proceed the denitrification reaction by using the decomposed product as an electron donor. By using the biodegradable resin in this way, it is unnecessary to add a liquid electron donor such as methanol, and the concentration control, which has been difficult until now, is also unnecessary, and unnecessary facilities can be reduced.

<Denitrification treatment method>
The denitrification treatment method of the present invention continuously denitrifies a liquid to be treated, which is a liquid containing nitrate nitrogen and / or nitrite nitrogen (any one or both of nitrate nitrogen and nitrite nitrogen). And a biological denitrification process by passing the liquid to be treated through a container filled with a biodegradable polymer-containing filler (referred to as a “denitrification process”). In some cases) as an essential step.

[Denitrification process]
In the denitrification process, a container filled with a filler containing a biodegradable polymer is used. Biological denitrification treatment can proceed by passing the liquid to be treated through the vessel. The filler may consist of only one kind of biodegradable polymer, or may contain two or more kinds of biodegradable polymers, or one or more kinds of biodegradable polymers and other components ( For example, it may consist of a composition containing additives and the like.

<Biodegradable polymer>
The biodegradable polymer used in the present invention is applicable as long as it is a biodegradable polymer, but is preferably a biodegradable polyester, more preferably an aliphatic polyester.

  Examples of the aliphatic polyester include polyhydroxyalkanoate (hereinafter abbreviated as PHA) and polyalkylene dicarboxylate. Examples of the biodegradable polyester other than the aliphatic polyester include polybutylene adipate-co-. A terephthalate is mentioned.

  The PHA refers to a polyester having a hydroxyalkanoic acid as a monomer unit. Specific examples include polyglycolic acid, polylactic acid (hereinafter abbreviated as PLA), poly-3-hydroxyalkanoate (hereinafter abbreviated as P3HA), poly-4-hydroxyalkanoate and the like. Among these, PLA and P3HA are preferable and P3HA is more preferable because the removal rate of the nitrogen compound is fast. In addition, when the contaminated water to be treated is derived from water having a high salt concentration such as seawater, P3HA is most preferable from the viewpoint of seawater biodegradability.

  The P3HA is a polymer having 3-hydroxyalkanoic acid as a main monomer unit (referred to as “poly (3-hydroxyalkanoate)”). The 3-hydroxyalkanoic acid monomer unit is not particularly limited. For example, 3-hydroxybutyrate, 3-hydroxypropionate, 3-hydroxyvalerate, 3-hydroxyhexanoate, 3-hydroxyheptanoate, 3 -Monomer units such as hydroxyoctanoate. These polymers may be homopolymers or copolymers containing two or more monomer units. When P3HA is a copolymer, it may be a copolymer of two or more types of 3-hydroxyalkanoic acid, or 4-hydroxy with respect to one or more types of 3-hydroxyalkanoic acid. It may be a copolymer of 4-hydroxyalkanoic acid such as butyrate.

  Among them, a polymer containing 3-hydroxybutyrate as a monomer unit is preferable from the viewpoint of supply, and specific examples thereof include poly-3-hydroxybutyrate homopolymer and poly-3-hydroxybutyrate copolymer. Some poly-3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBH), poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV), poly-3-hydroxybutyrate-co- 4-hydroxybutyrate etc. are mentioned. When using P3HA, only one type of P3HA may be used, or multiple types of P3HA may be used in combination. Of course, other biodegradable polymers, biodegradable polyesters, and biodegradable aliphatic polyesters can be used in combination.

  The polyalkylene dicarboxylate refers to a polycondensate of an aliphatic diol (or a derivative thereof) and an aliphatic dicarboxylic acid (or a derivative thereof). Specific examples include polybutylene succinate (hereinafter abbreviated as PBS), polyethylene succinate, poly (butylene succinate-co-butylene adipate), and the like.

  As the biodegradable polymer used in the present invention, P3HA, PBS and PLA are more preferable, P3HA and PBS are more preferable, and P3HA is particularly preferable from the viewpoint of the processing speed of the nitrogen compound. In addition, when the contaminated water to be treated is derived from water having a high salt concentration such as seawater, P3HA is most preferable from the viewpoint of seawater biodegradability.

  In the present invention, only one type of biodegradable polymer may be used, or multiple types may be used in combination. Moreover, the molded body of each biodegradable polymer may be mixed and used as a filler, or a molded body obtained by mixing and molding each biodegradable polymer in advance may be used as the filler.

  The shape of the filler containing the biodegradable polymer used in the present invention is not particularly limited as long as it is a solid that does not impede liquid flow, and any of powder, pellet, sphere, sheet, coil, string, and net It may be. However, in order to increase the treatment effect and work efficiency, the form is not limited as long as it has a large surface area, a certain degree of physical resistance, and easy handling. In use, each form may be used alone, or a plurality of forms may be mixed and used.

  The vessel used in the denitrification treatment step only needs to biologically denitrify the treatment target liquid by passing the treatment target liquid through the inside thereof, and the shape and the like are not particularly limited. Although the said container has the inlet and outlet of the said process target liquid, the position of the said inlet and outlet is not specifically limited. What is necessary is just to be a container which can be made to contact biologically denitrification processing by making a process target liquid contact with the filler containing a biodegradable polymer inside. For example, a columnar container as shown in FIG. 1 can be used.

  In the denitrification process in the present invention, it is necessary to bring the liquid to be treated into contact with the filler containing the biodegradable polymer in the container. As a method for bringing the liquid to be treated into contact with the filler, it is conceivable to use a method in which the filler is directly added to the liquid to be treated or an apparatus having a columnar structure filled with the filler. Considering the contact frequency of the material, it is preferable to use an apparatus (column-like denitrification processing section) in which a container as shown in FIG. 1 is filled with a filler containing a biodegradable polymer.

  The filling degree (filling rate) of the filler containing the biodegradable polymer in the container is not particularly limited, but is preferably 30 vol% or more with respect to the capacity of the container (100 vol%) from the viewpoint of the processing speed per reaction volume. More preferably, it is 40 vol% or more, and still more preferably 50% or more. On the other hand, the upper limit of the degree of filling is preferably 90 vol% or less, more preferably 80% or less. By setting the filling degree to 90 vol% or less, there is a tendency that blockage by microorganisms or biofilm attached to the biodegradable polymer is suppressed and the denitrification reaction can proceed more efficiently.

  By setting the filling degree of the filler containing the biodegradable polymer in the container to 30 vol% or more, it is effective to quickly reduce the concentration of dissolved oxygen present in the liquid to be treated. That is, in the present invention, dissolved oxygen in the treatment target liquid introduced into the container (denitrification processing unit) is quickly consumed by the microorganisms attached to the biodegradable polymer together with the utilization of the biodegradable polymer. The inside shifts to an anaerobic state. Therefore, for example, as shown in FIG. 2, when the liquid to be treated is introduced from the inlet provided in the lower part of the container and discharged from the outlet provided in the upper part of the container, the lower part in the container is in an aerobic state, but the upper part in the container is Become anaerobic. As described above, it is possible to quickly prepare an environment where the denitrification reaction proceeds promptly, and continuous denitrification treatment is possible.

  Of course, in order to advance the biological denitrification reaction in the container, it is necessary to propagate microorganisms in the container in advance before carrying out this method (before operating the apparatus described later in full scale). It goes without saying that there is. Although there are no particular limitations on the breeding method and the acclimatization method, in many cases, by filling the container with the liquid to be treated, microorganisms existing in the environment over time will be propagated and become stable. Of course, it is also possible to add sludge in activated sludge in order to speed up the start-up time.

  In the denitrification method of the present invention, the above-mentioned container (a container filled with a filler containing a biodegradable polymer) in which microorganisms are propagated as described above is used for simple and continuous denitrification. It becomes possible. In addition, about the capacity | capacitance of the said container, since it determines according to the process target load to generate | occur | produce, it does not specifically limit. Also, the material of the container is not particularly limited because it depends on the type of the liquid to be treated. However, if the liquid to be treated is seawater, it is preferably made of SUS if it is made of metal in order to prevent corrosion due to salt. If there is no particular problem in terms of weight, PVC is easy to use because it is inexpensive.

  Further, in order to remove nitrogen compounds stably and with high ability according to the present invention, the presence of phosphorus compounds in the liquid to be treated is important. That is, the liquid to be treated in the method or apparatus of the present invention contains a phosphorus compound. The presence of a phosphorus compound in the liquid to be treated greatly improves the denitrification efficiency. The effect is particularly remarkable in the low to medium temperature range, and in the absence of phosphorus compounds, the presence of phosphorus compounds can greatly improve the reaction rate even in cases where almost no denitrification occurs. It is. In the present invention, the phosphorus compound is a general term for inorganic phosphorus typified by orthophosphoric phosphorus and organic phosphorus typified by phospholipid.

  Basically, the treatment target liquid preferably contains a phosphorus compound at a concentration of 0.5 mg / L or more (more preferably 1.0 mg / L or more, further preferably 2.0 mg / L or more). In the method and apparatus of the present invention, the denitrification ability can be maximized. If the concentration of the phosphorus compound is not sufficient, the dissolved oxygen concentration at the outlet of the container (denitrification treatment unit) becomes high, that is, generally exceeds 5 mg / L, and the efficiency of the denitrification treatment tends to decrease. If it is determined that the concentration of the phosphorus compound is insufficient, it can be dealt with by adding the phosphorus compound to the liquid to be treated. The form of the phosphorus compound at that time is not particularly limited, and a water-soluble phosphorus compound such as phosphoric acid and / or a salt thereof is preferably used from the viewpoint of cost. Although the upper limit of the density | concentration of the phosphorus compound contained in a process target liquid is not specifically limited, From a viewpoint of cost and environmental impact, 10 mg / L or less is preferable, More preferably, it is 5 mg / L or less. In addition, the density | concentration of the phosphorus compound in this invention is made into the total phosphorus description (TP), and can be quantified by the acid hydrolysis-absorbance method. In addition, when a simple measurement is desired, a phosphorus quantification kit (for example, TNT845) manufactured by HACH can be suitably used from the viewpoint of simplicity of operation.

  In the present invention, the average residence time of the liquid to be treated in the apparatus is extremely important because it affects the denitrification reaction rate (1- (nitrogen compound concentration at the apparatus outlet) / (nitrogen compound concentration at the apparatus inlet)). Factor. The present inventor does not have a residence time in which the denitrification efficiency is remarkably high in the absence of the phosphorus compound, but on the other hand, in the presence of the phosphorus compound, the denitrification reaction depends on the residence time. It has been found that there is a residence time that is particularly high in denitrification efficiency, since the rate changes dramatically. In the present invention, the average residence time is 10 hours or less, and the average residence time in the presence of the phosphorus compound is preferably 5 hours or less, more preferably 4 hours or less, and even more preferably from the viewpoint of the net nitrogen compound removal amount. Preferably it is 3 hours or less. However, as described above, the lower the average residence time, the lower the denitrification reaction rate. Therefore, the lower limit is preferably 15 minutes or more, more preferably 30 minutes or more, and even more preferably 1 hour or more. It is.

  In the present invention, the average residence time is defined as a value obtained by dividing the volume of the treatment part (filling part of the filler containing the biodegradable polymer) by the volume flow rate per unit time.

  In the denitrification processing method of the present invention, the dissolved oxygen concentration of the processing target liquid (processing target liquid near the inlet of the container) to be introduced into the container is not particularly limited.

  In the denitrification method of the present invention, the dissolved oxygen concentration of the liquid after passing through the container (the processed liquid near the outlet of the container) is not particularly limited, but should be maintained at 5 mg / L or less. More preferably, it is 3.5 mg / L or less, More preferably, it is 1 mg / L or less, More preferably, it is 0.5 mg / L or less, More preferably, it is maintained at 0.1 mg / L or less. The lower limit of the dissolved oxygen concentration is not particularly limited, and may be 0 mg / L, for example. By setting the dissolved oxygen concentration to 5 mg / L or less, the denitrification environment in the container is prepared, and the denitrification reaction tends to proceed efficiently. The dissolved oxygen concentration can be maintained in a desired range by controlling the flow rate of the liquid to be treated into the container as described later, or by adjusting the concentration of the phosphorus compound in the liquid to be treated.

  The denitrification treatment method of the present invention is not particularly limited as long as it has the above-described denitrification treatment step, and may have other steps. Examples of other processes include, for example, a pH neutralization process that adjusts the pH of the liquid to be treated, and a process that removes solids using a strainer, a cyclone, or the like.

<Denitrification equipment>
The denitrification apparatus of the present invention is an apparatus for continuously denitrifying a liquid to be treated containing nitrate nitrogen and / or nitrite nitrogen, and the following denitrification processing unit and flow control mechanism are essential. It is an apparatus which has as a structure of.

Denitrification treatment part: A part that biologically denitrifies the liquid to be treated by letting the inside flow. Flow control mechanism: Monitors the dissolved oxygen concentration of the liquid at the outlet of the denitrification treatment part, and the dissolved oxygen concentration. Is maintained at 5 mg / L or less (more preferably 3.5 mg / L or less, more preferably 1 mg / L or less, further preferably 0.5 mg / L or less, more preferably 0.1 mg / L or less). Mechanism for controlling the flow rate of the liquid to be treated at the inlet of the denitrification treatment unit (inflow amount to the denitrification treatment unit) As the denitrification treatment unit in the denitrification treatment apparatus of the present invention, for example, the biodegradable polymer described above is used. Examples include a container filled with the filler.

<Equipment configuration>
In view of the above, the flow control mechanism in the denitrification apparatus of the present invention will be described. In order to make full use of the capacity of the denitrification treatment apparatus using this method, a system for sending the liquid to be treated at a constant flow rate to the denitrification treatment part having the column structure described above is required. A system that can monitor the dissolved oxygen concentration of the treated water (liquid after treatment in the denitrification treatment unit) at the part outlet and can change the flow rate so that the dissolved oxygen concentration is maintained at 5 mg / L or less is desirable. By doing so, the anaerobic state in the denitrification processing unit, that is, the denitrification environment can be monitored, and the flow rate is controlled based on the dissolved oxygen concentration information to maintain the denitrification environment in an optimum state. Can do. Of course, the dissolved oxygen concentration monitor may be analyzed online or may be analyzed offline. What is important is that the flow rate is appropriately controlled based on the dissolved oxygen concentration. Therefore, the flow rate may be controlled automatically, or the flow rate may be controlled manually.

  The flow rate control mechanism is preferably feedback control that, for example, if the dissolved oxygen concentration at the denitrification unit outlet increases by 10% from the set value, the flow rate at the denitrification unit inlet is reduced by 10%. Still, if the dissolved oxygen concentration at the denitrification treatment unit outlet is equal to or higher than the set value, it is further reduced by 10%, and the same operation is repeated until the dissolved oxygen concentration at the denitrification treatment unit outlet finally becomes less than the set value. . Of course, for example, if the dissolved oxygen concentration at the denitrification processing unit outlet is 10% lower than the set value, the control of increasing the flow rate at the denitrification processing unit inlet by 10% can be incorporated to make maximum use of the capacity of the apparatus. In order to do so, it is preferable. However, it is necessary to note that the response of the dissolved oxygen concentration in the denitrification unit is slow because of the residence time of the denitrification unit. Of course, feed forward control may be incorporated in consideration of the case where only feedback control is not possible.

  In addition, when the dissolved oxygen concentration at the denitrification processing unit outlet does not decrease easily even if the flow rate at the denitrification processing unit inlet is reduced, the phosphorus compound concentration in the raw water (treatment target liquid) is often insufficient. Therefore, in this case, it is preferable to add a phosphorus compound so that the concentration described above is obtained. The addition method may be mixed immediately before the liquid to be treated flows into the denitrification processing unit, or may be mixed in advance with the liquid to be treated. Of course, it is also possible to provide a system for adding a phosphorus compound in the denitrification processing apparatus and construct a system that can be added intermittently and / or continuously while monitoring the phosphorus concentration in the liquid to be processed.

  By utilizing the denitrification treatment method of the present invention and the denitrification treatment apparatus of the present invention, the removal of nitrogen compounds in the sewage treatment field, aquarium, aquarium fish tank, and aquaculture breeding water that have problems in nitrogen compound treatment Applicable to.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. In the examples, “%” is based on weight.

Example 1 [Denitrification treatment at room temperature (34 ° C.)]
<Assembly of denitrification equipment>
A device for measuring pH and DO near the outlet of the denitrification unit as shown in FIG. 2 by preparing a denitrification unit by filling the container (1 L) with KANEKA Biopolymer PHBH at a density of 60 vol%. (PH meter 4 and DO meter 5) were installed, and further, piping was installed at the inlet and outlet of the denitrification treatment unit to produce the denitrification treatment device shown in FIG.

<Adapting operation of bacteria>
The inside of the denitrification section in the assembled apparatus is filled with an inorganic salt medium containing about 10 mM of 0.1% ammonium sulfate and sodium nitrate as a nitrogen source, and cultured at 34 ° C. for 1 to 3 months to acclimate the complex microbial community. I let you.

<Preparation of liquid to be treated (simulated waste water for experiment)>
10 mM sodium nitrate is dissolved in distilled water, phosphoric acid is added so that the total phosphorus concentration is 0.5 mg / L, and the pH is adjusted to 7 with sodium hydroxide or hydrochloric acid. Was made.

<Analysis method>
For measurement of ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, and phosphorus concentrations, DR6000 manufactured by HACH and corresponding reagents (TNT832, TNT835, TNT840, 843) were used.

<Denitrification treatment>
The simulated waste water produced above was passed through the denitrification treatment section in the above-mentioned acclimatized denitrification treatment apparatus. As shown in Table 1, the flow rate of the simulated waste water was controlled so that the average residence time in the denitrification treatment unit was 1.3 hours. The apparatus temperature was controlled so that the internal temperature was 34 ° C.

  During the denitrification process, the liquid at the exit of the denitrification process unit was sampled, and the concentrations of ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen were analyzed. The total concentration of ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen thus obtained was defined as the total nitrogen concentration, and the net nitrogen removal amount was (net nitrogen removal amount [mg / h]) = (total inlet nitrogen concentration [ mg / L] −total outlet nitrogen concentration [mg / L]) × (flow rate [L / h]). The results are shown in Table 1.

Examples 2-4
A denitrification treatment was performed in the same manner as in Example 1 except that the average residence time in the denitrification treatment section was changed as shown in Table 1. The results are shown in Table 1.

Example 5 [Denitrification treatment at medium temperature (24 ° C.)]
Denitrification treatment was performed in the same manner as in Example 1 except that the internal temperature of the apparatus was changed to 24 ° C. The results are shown in Table 1.

Examples 6 and 7
The denitrification treatment was performed in the same manner as in Example 1 except that the internal temperature of the apparatus was changed to 24 ° C. and the average residence time in the denitrification treatment section was changed as shown in Table 1. The results are shown in Table 1.

Comparative Example 1 [Denitrification at normal temperature (34 ° C.)]
A denitrification treatment was performed in the same manner as in Example 1 except that phosphoric acid was not added to the treatment target solution. The results are shown in Table 1.

Comparative Examples 2-5
A denitrification treatment was performed in the same manner as in Comparative Example 1 except that the average residence time in the denitrification treatment section was changed as shown in Table 1. The results are shown in Table 1.

Comparative Example 6
A denitrification treatment was performed in the same manner as in Example 1 except that the average residence time in the denitrification treatment section was changed as shown in Table 1. The results are shown in Table 1.

Comparative Example 7 [Denitrification Experiment at Medium Temperature (24 ° C.)]
In the same manner as in Example 1, except that phosphoric acid was not added to the liquid to be treated, the internal temperature was changed to 24 ° C., and the average residence time in the denitrification treatment part was changed as shown in Table 1. Nitrogen treatment was performed. The results are shown in Table 1.

Comparative Examples 8-10
A denitrification treatment was carried out in the same manner as in Comparative Example 7 except that the average residence time in the denitrification treatment section was changed as shown in Table 1. The results are shown in Table 1.

Comparative Example 11
A denitrification treatment was carried out in the same manner as in Example 5 except that the average residence time in the denitrification treatment section was changed as shown in Table 1. The results are shown in Table 1.

  Table 1 also describes the dissolved oxygen concentration of the treatment liquid measured at the denitrification treatment unit outlet. However, the display of “−” indicates that the dissolved oxygen concentration is not measured.

  From Table 1, in Examples 1 to 7 in which the liquid to be treated contains a phosphorus compound and the average residence time of the liquid to be treated is 10 hours or less, the nitrogen compound removal amount per hour is high and the denitrification ability is remarkably high. It turns out that it is excellent in. Especially, although Examples 5-7 were implemented in the intermediate temperature (24 degreeC) area | region where denitrification activity tends to fall comparatively, the outstanding denitrification capability was shown.

  On the other hand, in Comparative Examples 1 to 11 in which the liquid to be treated did not contain a phosphorus compound or the average residence time of the liquid to be treated exceeded 10 hours, the nitrogen compound removal amount per hour was significantly larger than in Examples 1 to 7. It can be seen that the denitrification ability is low.

1 Filler containing biodegradable polymer 2 Inlet 3 Outlet 4 pH meter 5 DO meter (dissolved oxygen concentration meter)
6 Water tank 7 Treated water storage tank

Claims (6)

A method of continuously denitrifying a liquid to be treated containing nitrate nitrogen and / or nitrite nitrogen,
Including a step of biologically performing the denitrification treatment by passing the treatment target liquid through a container filled with a filler containing a biodegradable polymer, and an average residence time of the treatment target liquid in the container For 10 hours or less, and the liquid to be treated contains a phosphorus compound.   The denitrification method according to claim 1, wherein a dissolved oxygen concentration of the liquid after passing through the container is 5 mg / L or less.   The denitrification method according to claim 1 or 2, wherein the biodegradable polymer is an aliphatic polyester.   The denitrification method according to claim 3, wherein the aliphatic polyester is poly (3-hydroxyalkanoate).   The denitrification method according to any one of claims 1 to 4, wherein the container is a container in which the filler is filled at a filling degree of 30 vol% or more with respect to the capacity (100 vol%) of the container. . An apparatus for continuously denitrifying a liquid to be treated containing nitrate nitrogen and / or nitrite nitrogen,
A denitrification treatment unit that biologically denitrifies the liquid to be treated by passing the solution through the interior; the denitrification treatment unit is filled with a filler containing a biodegradable polymer;
The dissolved oxygen concentration of the liquid at the outlet of the denitrification processing unit is monitored, and the flow rate of the processing target liquid at the inlet of the denitrification processing unit is controlled so that the dissolved oxygen concentration is maintained at 5 mg / L or less. A denitrification processing apparatus comprising a mechanism.

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