JP2019010625A - PROCESSING METHOD OF LOW-pH STRAIN-KJ CULTURE WATER - Google Patents

Abstract

To decompose a contained organic compound by processing low-pH strain-KJ culture water more inexpensively and more efficiently in comparison with a conventional method, to thereby reutilize the low-pH strain-KJ culture water.SOLUTION: In a processing method of low-pH strain-KJ culture water, an organic compound contained in the culture water is decomposed by processing the low-pH strain-KJ culture water with microorganism. Synthetic waste water is brought into contact with a microorganism holding carrier to allow beforehand microorganism to adhere to the carrier, and thereafter, the low-pH strain-KJ culture water is brought into contact with the microorganism holding carrier to which microorganism adheres.SELECTED DRAWING: None

Description

  The present invention relates to a method for efficiently reusing a low pH KJ strain culture water at a lower cost than in the conventional method.

  Microalgae are unicellular organisms having a size of several μm to several tens of μm. This microalgae efficiently converts solar energy into hydrocarbons and accumulates them, and also contains various minerals and unsaturated fatty acids at high concentrations. Some microalgae contain useful substances such as starch, fats and oils, and so a process for recovering and purifying them and using them as pharmaceuticals, feeds and fuels has been proposed. The KJ strain of the present invention is a strain of Pseudococcomyxa sp. KJ strain (Accession number FERM AP-22254) (Patent Document 1). This KJ strain has a high hydrocarbon production capacity. In addition, this KJ strain has a hydrocarbon-producing ability in a nitrogen-deficient state (for example, a state in which the nitrogen weight in the dry weight of the KJ strain is less than 2 wt%).

  Open ponds called open ponds are widely used for culturing microalgae. In this process, bacteria and other microalgae grow in addition to the target microalgae. There was a problem of lowering productivity. To solve this problem, use the KJ strain, which is a microalgae resistant to low pH, and keep the pH of the culture water low, for example, pH 2-4, using acid agents such as carbonic acid, hydrochloric acid or sulfuric acid. Thus, a process for suppressing the growth of other microalgae and protists has been proposed (Non-Patent Documents 1 and 2).

  However, in this process, not only the acid agent is used for the preparation of the culture solution, but also after culturing the KJ strain, the pH is adjusted by degassing or adding an alkaline agent to discard the acidic waste water. There was a need to neutralize. Here, if the culture water after culturing the KJ strain can be reused without adjusting the pH, this problem can be solved.

  The culture water of the KJ strain contains, for example, about 5 to 15 mg / L of the low concentration organic compound secreted by the KJ strain as the TOC. Thus, when an organic compound is contained in the culture water, by repeating the reuse of the culture water, the TOC concentration in the culture water increases to generate microorganisms and other microalgae, and the productivity of the KJ strain decreases. . In order to prevent this, it is necessary to decompose and remove the organic compounds contained in the KJ strain culture water by some method.

  As a method for treating general waste water containing organic compounds, there is a physicochemical method, for example, a method of decomposing and removing organic compounds in waste water using UV, ozone or hydrogen peroxide, but the energy cost and chemical cost are high, It is not suitable as a decomposition method for reusing KJ strain culture water discharged in large quantities.

  When biological treatment methods are applied to the treatment of organic compounds, it is considered that energy costs and chemical costs can be reduced compared to physicochemical methods.

However, when the low pH KJ strain culture water as described above is treated, there are the following problems.
(1) In order to biologically treat organic compounds in KJ strain culture water, it is necessary to neutralize the target effluent, which requires a degassing process and a large amount of alkaline agent.
(2) In order to reuse the treated water obtained by the method of (1) for cultivation of microalgae, it is necessary to make the pH acidic again, and an acid agent such as carbonic acid, hydrochloric acid or sulfuric acid is added. There is a need.
(3) When the processes of (1) and (2) are repeated, the salt concentration of circulating water increases and the productivity of microalgae decreases.
(4) Since the culture water of KJ strain has a low organic compound concentration, the microorganisms in the tank do not form flocs and show a tendency to disperse. Accordingly, the cells cannot be maintained at a high concentration as in the activated sludge method, and the decomposition of the organic compound proceeds at a very low rate.

JP2015-15918A

Yoshihiko Sumi, Future Opened by Microalgae-Usefulness and Utilization-Science and Technology Trends, Science & Technology Trends September 2009 102, p.11-22. Hiraoka, S., Higuchi, S., Uzuka, A., Nozaki, H., Miyagishima, S. (2014). Acidophilic Green Alga Pseudochlorella sp. YKT1 Accumulates High Amount of Lipid Droplets under a Nitrogen-Depleted Condition at a Low-pH. PloS ONE.9 (9), e107702.

  The present invention has been made in view of the above-described prior art, decomposes organic compounds contained by treating KJ strain culture water having a low pH more efficiently and at a lower cost than conventional methods, It is an object of the present invention to provide a treatment method for low pH KJ strain culture water that enables reuse of low pH culture water.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor, when treating an organic compound in culture water with microorganisms, first, a high concentration of heterotrophic bacteria that decompose carbon sources under low pH conditions as a carrier It was found that the organic compounds in the low-pH KJ strain culture water can be efficiently decomposed by adhering to the KJ strain culture water.

  The present invention has been achieved based on such findings, and the gist thereof is as follows.

[1] A method for treating low pH KJ strain culture water, comprising treating low pH KJ strain culture water with a microorganism to decompose organic compounds in the culture water.

[2] The method for treating low pH KJ strain culture water according to [1], wherein the pH of the low pH KJ strain culture water is 2 to 4.

[3] In [1] or [2], the microorganism may be any one of Acidisoma sp., Acidisphaera sp., Singulisphaera sp., Acidobacterium sp., Dyella sp., Humibacter sp. And Thermosporothrix sp. A method for treating low pH KJ strain culture water, which is a heterotrophic bacterium containing more than one species.

[4] The carrier according to any one of [1] to [3], wherein the microorganism is attached to a microorganism holding carrier of any one of a fluidized bed, a fixed bed, a watering filter bed, and a microfiltration membrane, and the microorganism is attached thereto. And the low pH KJ strain culture water, the method of treating the low pH KJ strain culture water.

[5] In [4], after the synthetic waste water is brought into contact with the microorganism holding carrier and the microorganism is attached to the carrier in advance, the low pH KJ strain culture water is brought into contact with the microorganism holding carrier to which the microorganism is attached. A method for treating a low pH KJ strain culture water.

[6] A method for treating low pH KJ strain culture water according to [4] or [5], wherein the amount of the microorganism attached to the microorganism-supporting carrier is 50 to 1,000 mg / L-carrier .

  According to the present invention, the organic compound in the low pH KJ strain culture water can be efficiently treated at a lower cost while maintaining the low pH value by the microorganism, and the organic compound contained can be decomposed and removed. it can. For this reason, the treated water according to the present invention can be repeatedly reused as it is as low pH KJ strain culture water, and the water cost, culture cost, and waste water treatment cost can be reduced.

  Hereinafter, embodiments of the present invention will be described in detail.

  The present inventor conducted the following studies to decompose organic compounds in the low pH KJ strain culture water with microorganisms.

  In general, in order to attach organic compound-degrading bacteria in wastewater to be treated to the microorganism-supporting carrier, a method of increasing the cell concentration of the carrier by repeatedly supplying wastewater to be treated is often used. In the low pH KJ strain culture water to be treated in the present invention, since the organic compound concentration is low, the biofilm is peeled off before the cells are sufficiently attached to the carrier. A sufficient amount of cells necessary for the treatment could not be attached to and accumulated on the carrier.

  Therefore, the present inventor diligently studied, and first, by supplying synthetic effluent adjusted to pH acidity to the carrier separately from the culture water of KJ strain, it is dependent on decomposing general carbon sources such as glucose under low pH conditions. Vegetative bacteria were attached to the carrier at a high concentration.

  Then, when the supply water was changed to KJ strain culture water and the carrier was acclimatized, the autolysis of microorganisms that could not assimilate organic compounds in the KJ strain culture water occurred for about one week, and the amount of cells attached to the carrier decreased. At the same time, the concentration of dissolved organic substances thought to have been generated by autolysis in the culture water increased, but then the amount of adherent cells on the carrier stabilized, and the organic compounds in the KJ strain culture water could be decomposed at a high rate. Confirmed to be.

  In the present invention, the organic compound in the low pH KJ strain culture water can be efficiently decomposed by microorganisms in this way.

  Here, the pH value of the low pH KJ strain culture water is a pH condition for selectively producing the target microalgae in the culture of the microalgae in the above-mentioned open pound, and usually 1 to 5, preferably in the range of 2-4.

  Although there is no restriction | limiting in particular in the organic compound density | concentration in the low pH KJ strain culture water processed by this invention, It is a comparatively low concentration TOC containing water about 3-20 mg / L normally as a TOC density | concentration.

  As described above, in order to efficiently treat such low TOC concentration low pH KJ strain culture water with microorganisms, a microorganism holding carrier is used, and microorganisms are attached to the microorganism holding carrier at a high concentration in advance. Is preferred.

  As the microorganism-supporting carrier, a microfiltration membrane or the like can be used in addition to a fluidized bed, a fixed bed, a watering filter bed.

  In the case of using a fluidized bed carrier, the shape thereof is arbitrary such as a spherical shape, a pellet shape, a hollow cylindrical shape, and a thread shape, and the size is a diameter of about 0.1 to 10 mm. The material is arbitrary, such as a natural material, an inorganic material, or a polymer material, and a gel material may be used. A foamed resin carrier such as polyurethane foam (polyurethane sponge) is preferable.

  As for the fixed bed carrier, the shape thereof is arbitrary such as a thread shape, a plate shape, and a strip shape, and the material may be a natural material, an inorganic material, a polymer material, etc., and a gel material may be used. For the fixed bed carrier, it is preferable to use a foamed resin carrier such as polyurethane foam.

  As the sprinkling filter bed, a plastic filter material of 20 to 60 mm or a polyurethane filter material is preferable. A hollow fiber membrane is preferred as the microfiltration membrane.

  In order to attach microorganisms to such a microorganism-supporting carrier, organic substances such as glucose and yeast extract are contained, and the TOC concentration is higher than the TOC of KJ strain culture water having a low pH and is about 50 to 1000 mg / L, and the pH is treated. A synthetic wastewater having a pH value equivalent to that of the low pH KJ culture water is prepared, and this synthetic wastewater is brought into contact with a microorganism-supporting carrier, so that bacteria belonging to the family Acetobacteraceae such as Acidisoma sp. Bacteria belonging to the family Rhodanobacteraceae such as Dyella sp., Bacteria belonging to the family Conexibacteraceae such as Conexibacter sp., Bacteria belonging to the family Isosphaeraceae such as Singulisphaera sp., Bacteria belonging to the family Microbacteriaceae such as ix sp ., Bacteria belonging to the family Acididoacteriaceae such as Acidobacterium sp., Bacteria belonging to the family Patulibacteraceae such as P atulibacter sp., bacteria belonging to the family Microbacteriaceae such as Curtobacterium sp., bacteria belonging to the family Legionellaceae such as Legionella sp., bacteria belonging to the family Patulibacteraceae such as Patulibacter sp. Attach heterotrophic bacteria with the resolution of a typical carbon source. In this case, if the amount of heterotrophic bacteria adhering to the microorganism-supporting carrier is too small, the bacteria to be prioritized do not adhere sufficiently, and the organic compound is efficiently removed in subsequent contact with the low pH KJ strain culture water. The amount of heterotrophic bacteria adhering to the carrier may be 50 mg / L-carrier or more, preferably 100 mg / L-carrier or more, more preferably 300 mg / L-carrier. Try to be above. The higher the amount of heterotrophic bacteria adhering to the carrier, the higher the decomposition rate of organic compounds in the treatment of KJ strain culture water at a low pH, but the longer the treatment with synthetic waste water to increase the amount of attachment. Accordingly, the amount of heterotrophic bacteria attached may be 1000 mg / L-carrier or less, or 50 mg / L-carrier or less.

  After the synthetic waste water is brought into contact with the microorganism-supporting carrier and heterotrophic bacteria are attached to the carrier at a high concentration, the carrier is switched to contact with the low pH KJ strain culture water. At the beginning of switching to contact with low pH KJ strain culture water, once the microorganisms cannot assimilate organic compounds in the KJ strain culture water, the amount of cells attached to the carrier decreases, and this occurs due to the self-degradation of microorganisms. As the dissolved organic matter increases, the TOC concentration of the treated water becomes higher than the TOC of the KJ strain culture water. However, if contact is continued, the amount of bacterial cells attached to the carrier becomes stable, and the KJ strain culture water is stabilized at high speed. The TOC concentration of treated water is reduced. Thereafter, organic compounds in the KJ strain culture water can be stably decomposed by heterotrophic bacteria attached to the carrier.

  Specifically, in this treatment, the reaction vessel is filled with the above-mentioned microorganism-supporting carrier, and the above-mentioned synthetic waste water is passed through the reaction vessel so as to have a predetermined cell adhesion amount. This can be done by switching to water.

  Thus, the treated water obtained by decomposing the organic compound can be effectively reused as KJ strain culture water. In addition, it is preferable to reduce the organic compound in the treated water to a TOC concentration of 5 mg / L or less for reuse as KJ strain culture water.

  Hereinafter, the present invention will be described more specifically with reference to examples.

In the following examples, KJ strain was used as the microalgae. To the medium for culturing the KJ strain, ammonium sulfate and potassium hydrogen phosphate were added to pure water so that the concentrations of NH ₄ -N and PO ₄ -P were 10 mg / L and 0.5 mg / L, respectively. The pH was adjusted to 3.0. After sufficiently growing the cells, the obtained culture solution was filtered with a 0.45 μm filter to obtain KJ strain culture water. The TOC concentration of this KJ strain culture water was 10 mg / L.

  As the synthetic wastewater, a synthetic medium in which glucose and yeast extract were diluted with ultrapure water and the pH was adjusted to 3.0 was used. The TOC concentration of this synthetic waste water was adjusted to 100 mg / L.

  Polyurethane sponge (0.3 cm × 0.3 cm × 0.3 cm cube) was used as the microorganism holding carrier.

[Example 1]
300 mL of microorganism holding carrier was placed in a 1 L graduated cylinder, and synthetic waste water was dispensed to 1 L. The TOC concentration was measured over time, and after the TOC concentration decreased gradually, the synthetic wastewater in the graduated cylinder was discarded and replaced with new synthetic wastewater. After replacing the synthetic wastewater 10 times, KJ strain culture water was dispensed to 1 L in a graduated cylinder, and the TOC concentration was measured over time. As a result, the TOC concentration increased from 10 mg / L to 100 mg / L. The KJ strain culture water in the graduated cylinder was discarded, and fresh KJ strain culture water was dispensed. When this operation was repeated, the TOC concentration decreased with time after the KJ strain culture water was exchanged twice. The rate of decrease in the TOC concentration increased each time the KJ strain culture water was replaced. When the KJ strain culture water was replaced three times, 10 mg / L TOC could be decomposed in 4 hours.

[Comparative Example 1]
300 mL of a microorganism holding carrier was placed in a 1 L graduated cylinder, and KJ strain culture water was dispensed to 1 L. The TOC concentration was measured over time, and after the TOC concentration decreased gradually, the KJ strain culture water in the graduated cylinder was discarded and replaced with new KJ strain culture water. The rate of decrease in TOC increased slightly every time KJ strain culture water was replaced, but the time required for 10 mg / L TOC degradation after 10 times of KJ strain culture water replacement was about 500 hours. The time required for 10 mg / L TOC decomposition after 100 times of replacement of the culture water was about 250 hours.

  From the above results, the pH-trophic synthetic waste water is contacted in advance to attach the heterotrophic bacteria to the microorganism-supporting carrier at a high concentration, and then used for the treatment of the KJ strain culture water. It can be seen that the organic compound can be efficiently decomposed, and the treated water obtained by decomposing and removing the organic compound can be reused as culture water.

  In Example 1, microorganisms adhering to the microorganism-supporting carrier before switching from synthetic wastewater to KJ strain culture water were examined by the clone library method. As a result, the carrier contained general carbon such as glucose under low pH conditions. It is confirmed that about 10 mg / L-carrier of heterotrophic bacteria Acidisoma sp., Acidisphaera sp., Singulishaera sp., Acidobacterium sp., Dyella sp., Humibacter sp., Termosporothrix sp. It was done.

Claims (6)

  A method for treating low pH KJ strain culture water, comprising treating low pH KJ strain culture water with microorganisms to decompose organic compounds in the culture water.   The method of treating low pH KJ strain culture water according to claim 1, wherein the pH of the low pH KJ strain culture water is 2 to 4.   3. The subordinate according to claim 1 or 2, wherein the microorganism comprises one or more of Acidisoma sp., Acidisphaera sp., Singulisphaera sp., Acidobacterium sp., Dyella sp., Humibacter sp., And Thermosporothrix sp. A method for treating a low pH KJ strain culture water, which is a vegetative bacterium.   In any one of Claims 1 thru | or 3, the said microorganisms are made to adhere to the microorganisms holding support | carrier in any one of a fluidized bed, a fixed bed, a watering filter bed, and a microfiltration membrane, The carrier to which this microorganism was made to adhere, A method for treating low pH KJ strain culture water, comprising contacting low pH KJ strain culture water.   5. The method according to claim 4, wherein the microorganism holding carrier is brought into contact with synthetic waste water to cause the microorganism to adhere to the carrier in advance, and then the low pH KJ strain culture water is brought into contact with the microorganism holding carrier to which the microorganism has adhered. A method for treating low pH KJ strain culture water.   6. The method for treating low pH KJ strain culture water according to claim 4 or 5, wherein the amount of the microorganism attached to the microorganism-supporting carrier is 50 to 1,000 mg / L-carrier.