JP2002219489A - Method for removing and recovering phosphorus using microorganism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop an economical and stable technique to recover phosphorus. SOLUTION: A solid carrier immobilizes mold which can take in and accumulate phosphorus under an aerobic condition and meanwhile can release the accumulated phosphorus under an anaerobic condition. The mold is made to take in and accumulate phosphorus by putting the mold into contact with water containing phosphorus under an aerobic condition and then the accumulated phosphorus by the mold is released and recovered by keeping the mold in an anaerobic condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for removing and recovering phosphorus by utilizing a mold having a phosphorus accumulation ability.

[0002]

2. Description of the Related Art In order to remove phosphorus from wastewater, a coagulation precipitation method using various metal salts, a crystallization phosphorus removal method, or an anaerobic / aerobic activated sludge method is used. But Al, F
e, The coagulation precipitation method using Ca salt has a high chemical cost, and in addition, the generated precipitate is disposed of as industrial waste.

[0003] As one of the crystallization dephosphorization methods, there is known a method of efficiently converting phosphorus to hydroxylapatite using a seed crystal of hydroxylapatite and removing it. However, although the product gluteal was reduced in this way, HCO ₃ in the liquid ^- for ions to inhibit crystallization, HCO ₃ and once acidic ^- After removal, it is necessary to return the pH to a weakly alkaline side . For this reason, there is a problem that the running cost due to the chemical becomes large similarly to the coagulation sedimentation method. In addition, struvite crystallization, which is another crystallization dephosphorization method, can be applied to wastewater having a relatively high phosphorus concentration,
With low-concentration phosphorus drainage, the crystallization efficiency is reduced.

[0004] On the other hand, the anaerobic / aerobic activated sludge method is a method of removing phosphorus by utilizing the phosphorus accumulation ability of living organisms. However, although running costs are low, it is difficult to control the biota.
An unstable phosphorus removal is a major problem.

As described above, the coagulation sedimentation method using a metal salt has a problem in running cost, and the anaerobic / aerobic activated sludge method has a large problem in treatment stability.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to develop an economical and stable phosphorus removal technique.

[0007]

Means for Solving the Problems The present inventor has conventionally proposed:
The present inventors have found that mold used as a research material in the field of genetics has a high phosphorus accumulation ability, and have completed a technique for removing phosphorus by using mold having the phosphorus accumulation ability. Furthermore, among these molds, especially Neuros
pora crassa has the ability to take up and accumulate phosphorus under aerobic conditions, but has the ability to release the accumulated phosphorus under anaerobic conditions, and complete the technology to recover phosphorus by utilizing this mold Reached. in addition,
Since mold has the property of growing by elongating mycelia, it can be easily immobilized by using an appropriate carrier, and thus a phosphorus removing agent and a collecting agent having a high cell density have been completed.

That is, the objects of the present invention are as follows:
This is achieved by (6).

(1) A phosphorus-removing agent obtained by immobilizing a mold capable of taking up and accumulating phosphorus on a solid-phase carrier.

(2) The mold is Aspergillus niger, A
spergillus niger, Neurospora crassa, Neurospora cr
selected from the group consisting of assa and Emericella nidulans (3) A mold capable of taking up and accumulating phosphorus under aerobic conditions and releasing accumulated phosphorus under anaerobic conditions is immobilized on a solid support. Phosphorus recovery agent.

(4) The agent for recovering and removing phosphorus according to claim 3, wherein the mold is Neurospora crassa.

(5) A method for removing phosphorus from a phosphorus-containing aqueous solution, wherein the mold is taken up and accumulated by contacting the phosphorus-containing aqueous solution with the phosphorus-removing agent according to claim 1 or 2. .

(6) By contacting the phosphorus-recovering agent according to claim 3 with an aqueous solution containing phosphorus under aerobic conditions, phosphorus is taken in and accumulated in the mold, and is then subjected to anaerobic conditions. A method for removing phosphorus from a phosphorus-containing aqueous solution, wherein the phosphorus accumulated in the mold is released by holding the phosphorus under the mold.

(7) The method for recovering phosphorus according to claim 6, wherein sugars, organic acids, peptones, amino acids and the like are present when the mold is kept under anaerobic conditions.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail.

The mold used in the present invention is not particularly limited as long as it has a phosphorus accumulation ability.
s niger, Aspergillus niger, Neurospora crassa, Eme
ricella nidulans and the like. this house,
Particularly preferred is Neurosporacrassa. These strains are referred to in the present invention as Pseudomona, a phosphorus-accumulating bacterium.
It has been confirmed that it has the same phosphorus accumulation ability as s sp. Acinetobacter calcoaceticus.

Furthermore, a particularly preferred mold, Neurospora
Crassa has the ability to take up and accumulate phosphorus under aerobic conditions, while releasing accumulated phosphorus under anaerobic conditions. Therefore, if Neurospora crassa is used, it is possible not only to remove phosphorus from wastewater and the like, but also to easily recover the removed phosphorus.

When phosphorus is accumulated in organisms and phosphorus in wastewater is removed, it is necessary not only that the organisms have a high phosphorus accumulation ability, but also that the cell density is kept high. Since mold has the property of growing by elongating mycelium, it can be easily immobilized by using an appropriate carrier, and a phosphorus removal facility having a high cell density can be constructed. In that case, as the solid phase carrier used for immobilizing the above-mentioned mold, any porous material having a water retention property and having a gap through which the mold hypha can be extended and serves as an air passage can be used. . As the material, a resin such as polypropylene, ceramics, or any other material that can be processed so as to satisfy the above-described properties as a carrier can be used without any particular limitation.

Examples of the phosphorus-containing aqueous solution to be treated by the method of the present invention include phosphorus-containing wastewater and secondary treatment water with residual phosphorus. When phosphorus is recovered in an aqueous solution by applying the present invention, it can be used as a liquid fertilizer. In some cases, phosphorus can be precipitated and recovered by applying a crystallization dephosphorization method. In this case, since the phosphorus concentration is higher than in the case where the phosphorus-containing wastewater is directly treated by a chemical technique, the recovery rate can be improved by increasing the efficiency of crystal precipitation.

In the present invention, when recovering phosphorus using Neurospora crassa, first, aerobic conditions are maintained in a phosphorus-containing aqueous solution, and phosphorus is taken up and accumulated in Neurospora crassa. To maintain such aerobic conditions, air may be bubbled through the solution if necessary. Once phosphorus is incorporated and accumulated, the solution is then maintained under anaerobic conditions to release the accumulated phosphorus in Neurospora crassa. As means for maintaining the anaerobic condition, means such as bubbling an inert gas such as nitrogen gas into the solution can be used.

[0021] Phosphorus release under anaerobic conditions can be achieved simply by subjecting the reaction tank to anaerobic conditions. However, in order to increase the release rate, sugars such as glucose, amino acids such as peptone, and other amino acids. Is more effective. Therefore, in the phosphorus release step under anaerobic conditions, it is desirable to add the above substances alone or as a mixture. Since these organic substances serve as a biological energy source necessary for the uptake of phosphorus under aerobic conditions, that is, the synthesis of polyphosphate from phosphoric acid in cells, they not only promote phosphorus release but also under aerobic conditions. May also promote phosphorus uptake at

As described above, the phosphorus-containing wastewater is treated under aerobic conditions to remove phosphorus, and when the phosphorus removal rate decreases, phosphoric acid is then released under anaerobic conditions. Since the cells that have released phosphate restore their ability to take up phosphate under aerobic conditions, phosphorus can be removed repeatedly. It is possible to cope with the continuous drainage by preparing two sets of this device and operating them alternately.

Hereinafter, the present invention will be described with reference to Examples.
The technical scope of the present invention is not limited by these examples.

[0024]

EXAMPLE 1 When removing and recovering phosphorus contained in wastewater using microorganisms, it is necessary that the amount of accumulated phosphorus of the microorganisms used is large. Acinetobactor, Arthrobactor, Pse
Microorganisms such as genus udomonas have been isolated as bacteria with high phosphorus accumulation. We know that eukaryotes, molds,
Focusing on the potential of phosphorus uptake and accumulation ability based on the size of the cells, and the characteristics of the life cycle that can grow under oligotrophic conditions, etc., we thought that it could be applied to a phosphorus removal system. Thus, the amount of phosphorus accumulated in molds was compared with the bacteria shown above. The bacteria compared were Acinetobacter ca, a phosphorus-accumulating bacterium.
lcoaceticus, Pseudomonas sp.

The microorganisms shown in Table 1 were cultured in a medium in which potassium hydrogen phosphate was added to the modified Czapek's Dox medium shown in Table 2 so that the phosphoric acid concentration became 60 mg / L. Twenty-four hours after the start of the culture, the cells were collected from each culture solution, and the cell weight was measured. At the start of the culture and at the end of the culture, the total phosphorus concentration in the medium was measured, and the difference was defined as the total phosphorus taken into the cells.

Table 3 shows the results. From these results, Aspergillus niger, Aspergillusniger, Neurospor
It can be seen that both a crassa and Emericella nidulans have the ability to take up and accumulate phosphorus. In particular, N. cra
It can be determined that ssa (III) (hereinafter referred to as N. crassa) has a phosphorus storage ability substantially equal to that of phosphorus storage bacteria. In addition, from the knowledge of phosphorus removal by activated sludge, the accumulated amount of phosphorus in sludge is only about 2 to 2.5%, and the phosphorus accumulation capacity of N. crassa exceeds this. Therefore, N. has the highest phosphate accumulation ability among molds.
crassa strains can be applied to the phosphorus removal and recovery process.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

Example 2 As conditions for biologically removing phosphorus, it is necessary that not only the ability of the organism to accumulate phosphorus be high, but also that the rate of phosphorus uptake be high. For example, when applied to a treatment process with a short water residence time, the ability to accumulate phosphorus is limited by the rate of phosphorus uptake, so it is desirable to use organisms with a high phosphorus uptake rate. Here, as in Example 1, the phosphorus uptake rate of the mold of the present invention was compared with that of the phosphorus-accumulating bacteria.

N. crassa, which has a high phosphorus storage ability, and A. calcoaceticus, a phosphorus storage bacterium, as a control organism
Was inoculated into a modified Czapek's Dox medium supplemented with potassium dihydrogen phosphate at a phosphoric acid concentration of 20 μM, and cultured. The cells were collected and washed with a phosphate uptake test medium (modified Czapek's Dox medium, pH 7.0, containing no carbon source and containing potassium dihydrogen phosphate at 30 mg-PO ₄ / L), Almost 1 g-dry_w in the phosphate uptake test medium
The suspension was resuspended to eight / l, and the suspension was shaken under aerobic conditions to examine the phosphate uptake rate of each strain.

FIG. 1 is a graph showing the rate of phosphate uptake of each strain calculated from the weight of phosphorus taken up per gram of cells during 30 minutes after the start of the test. From this result, N.
crassa is a phosphorus-accumulating bacterium, A. calcoaceticu
s has the same phosphate uptake rate as N. crassa
The strain can be determined to be applicable to the phosphorus removal and recovery process.

Example 3 Modified Czapek's Dox prepared by adding potassium dihydrogen phosphate to N. crassa having a high phosphorus accumulating ability and A. calcoaceticus, which is a phosphorus accumulating bacterium as a control organism, at a phosphoric acid concentration of 20 μM. The medium was inoculated and cultured. The cells were collected, washed with a phosphate uptake test medium, and resuspended in the phosphate uptake test medium so that the cell concentration was approximately 1 g-dry_weight / l. As in Example 2, phosphorus was aerobically incorporated. After a lapse of 3 hours, nitrogen gas was blown into the test medium to forcibly set the medium in an anaerobic condition. As a result, it was found that phosphorus taken in under the aerobic condition was released again. The results are shown in the graph of FIG.

In the same experimental system, when switching to anaerobic conditions, an organic substance is appropriately added to the test medium (in this example,
100 mg-TOC / L of glucose as organic matter)
When the phosphorus was released again,
It was found that the release rate and concentration increased (FIG. 3). In addition, TOC (total organic carbon) represents the total amount of organic carbon.

From the above results, using mold N. crassa,
Builds a biological phosphorus removal and recovery system by removing phosphorus by incorporating phosphorus in phosphorus-containing wastewater into cells under aerobic conditions and releasing the phosphorus accumulated in the cells under anaerobic conditions can do.

[0036]

According to the present invention, the running cost of chemicals and the like is kept to a minimum and a stable phosphorus removal technique is provided. The secondary treatment such as inorganic phosphorus-containing wastewater and conventional activated sludge treatment is provided. Phosphorus can be efficiently removed from water. In addition, it is possible to recover phosphorus, which has been difficult to recover only by removal.

Although the biological phosphorus removal ability depends on the biological concentration in the phosphorus removal tank, it is difficult to maintain a high biological concentration in conventional phosphorus removal using activated sludge. Removal capacity was limited to the activated sludge concentration. In the present invention, the mold is immobilized on an appropriate carrier by utilizing the property of growing by growing the hypha, and therefore, there is a feature that a phosphorus removing facility having a high cell density can be constructed.

[Brief description of the drawings]

FIG. 1 is a graph showing the phosphate uptake rate of each strain.

FIG. 2 is a graph showing the results of a phosphorus uptake / rerelease experiment.

FIG. 3 is a graph showing the effect of adding an organic substance on phosphorus uptake and re-release.

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Claims (7)

[Claims] 1. A phosphorus removing agent obtained by immobilizing a mold capable of taking up and accumulating phosphorus on a solid support. 2. The method according to claim 1, wherein the mold is Aspergillus niger, Asper.
gillus niger, Neurospora crassa, Neurospora crass
a, and selected from the group consisting of Emericella nidulans 3. In aerobic conditions, phosphorus is taken up and accumulated,
A phosphorus recovery agent obtained by immobilizing a mold capable of releasing accumulated phosphorus under anaerobic conditions on a solid support. 4. The agent for recovering and removing phosphorus according to claim 3, wherein the mold is Neurospora crassa. 5. A method for removing phosphorus from a phosphorus-containing aqueous solution, comprising bringing a mold into which phosphorus is incorporated by accumulating the phosphorus-containing aqueous solution with the phosphorus-removing agent according to claim 1 or 2. 6. A method in which phosphorus is taken in and accumulated in the mold by contacting the phosphorus recovery agent according to claim 3 with an aqueous solution containing phosphorus under aerobic conditions, and then the anaerobic condition is applied. Discharging the phosphorus accumulated in the mold by holding the phosphorus in the aqueous solution containing phosphorus. 7. When the mold is kept under anaerobic conditions,
The method for recovering phosphorus according to claim 6, wherein sugars, organic acids, peptone, amino acids and the like are present.