JPH0798193B2 - Method for suppressing the generation and growth of filamentous fungi - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for suppressing the generation and growth of filamentous fungi, and more specifically, in an organic wastewater treatment method by an activated sludge method, the method for preventing the generation and growth of filamentous fungi by using a flocculant-producing bacterium. The present invention relates to a method for suppressing the generation and growth of filamentous fungi, which enables efficient separation of activated sludge and treated water.

[0002]

2. Description of the Related Art Conventionally, an activated sludge system has been widely used as a method for treating wastewater containing various organic substances. This activated sludge system is a highly efficient treatment method, and is the most widely used treatment method because it produces high quality treated water economically. The most important problem left in the activated sludge system is separation of treated water and activated sludge after treatment, and the treated water and activated sludge quickly settle and separate in the separation area which is a settling tank. However, it is desirable that the flocculation or deflocculation phenomenon occurs due to the generation of filamentous fungi during standing in the separation area, which reduces the flocculating floc action of the activated sludge, resulting in insufficient sedimentation and separation of the activated sludge. The problem arises.

As a method for promoting the separation of activated sludge and treated water, a method using a polymer flocculant such as a cationic polymer or an inorganic flocculant such as a polyvalent metal ion is known. Since its biodegradability is insufficient, the problem of environmental pollution is caused by being discharged together with the treated water. Therefore, an object of the present invention is to provide a method for suppressing the generation and growth of filamentous fungi, which is capable of efficiently separating activated sludge in an organic wastewater treatment method without causing the bulking phenomenon of activated sludge.

[0004]

The above object can be achieved by the present invention described below. That is, the present invention relates to a method for treating organic wastewater by the activated sludge method , wherein
The police flocculant-producing bacteria were placed in an open system in fructose medium.
A method for inhibiting the growth and growth of filamentous fungi in a separation region between activated sludge and treated water, characterized in that a culture obtained by culturing and calcium chloride are present in the treatment system, and
Fragmented Rhodococcus erythropolis flocculant-producing bacteria
A culture obtained by culturing in an open system in a liquid medium of cucrose.
Generation of filamentous fungi characterized by freeze-drying a nutrient solution
It is an inhibitor .

[0005]

[Function] In an organic wastewater treatment method using a flocculant-producing bacterium, by using calcium chloride together with a flocculant-producing bacterium, the generation and growth of filamentous fungi, which is the main cause of the bulking phenomenon, is suppressed, and activated sludge and treated water are treated. The separation of the activated sludge and the treated water is remarkably promoted by controlling the pH of the separation area, the flocculant-producing bacteria and the concentration of calcium chloride in the specific ranges. In addition, Rhodococcus erythropolis is most preferable as the aggregating substance-producing bacterium to be used, and since the aggregating substance-producing bacterium can be efficiently cultured in a fructose liquid medium in an open system, it can be industrialized at a cost. Furthermore, even if the above-mentioned culture solution is freeze-dried and powdered, the viable cell count does not decrease much, and by rapidly reculturing it in condensate, it grows rapidly, so a large-scale culture facility is not required for each treatment facility and aggregation The organic wastewater treatment method using the substance-producing bacteria can be economically implemented.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to the preferred embodiments. The organic wastewater treatment method itself by the activated sludge system used in the present invention is well known,
The present invention can be applied to any of these well-known organic wastewater treatment methods and is not particularly limited. In addition, the aggregate-producing bacteria used in the present invention are
Lord Cocca belonging to the genus Coccus or Nocardia
S. erythropolis , and its representative strains are Rhodococcus erythropolis KR-256-2 and FERM-P.
No. 3923 and Rhodococcus erythropolis KR-S-1, FERM-P No. 3530.
The former name, Nocardia erythropoles, was established in 1980 by the International Committee for the Convention on the Naming of Microorganisms.
Reclassified and reclassified as Erythropolis.

In order to inoculate Rhodococcus erythropolis bacterium when used for preventing bulking of activated sludge, it is generally desirable to pre-culture (including acclimatization) cells in the presence of a target drainage substrate. However, pre-culture is not always necessary. Load Lactococcus, which has been inoculated mixed in this way
It is desirable that the erythropolis bacterium maintain the growth pH of the bacterium and supply a nutrient source, but it can be used for a certain period without adding a nutrient source. Examples of nutrient sources include carbon sources, inorganic salts, inorganic nitrogen sources, organic nitrogen sources, vitamins, agricultural product wastes, food industry wastes, fermentation waste liquids and residues, municipal wastes, and the like. Since this strain can be applied to various substrates such as general organic carbohydrates, municipal wastewater, industrial wastewater, hydrocarbons, pollutants, and environmental pollutants such as phthalates, there is no need for pre-culture. The effect can be exerted only by adding seed bacteria.

The medium of Rhodococcus erythropolis includes fructose as a carbon source.
e) , nitrogen sources such as ammonium sulfate, urea, ammonium salt and peptone, and other nutrient sources such as inorganic salts, vitamins and yeast extract. The culture may be liquid culture or solid culture. In the case of liquid culture, it is carried out by aeration and agitation at a pH of about 4 to 8 and a temperature of 20 to 40 ° C. The culture is completed by culturing for about several days to obtain a culture. In general, the culture broth thus obtained can be added as it is to the settling tank of the activated sludge method equipment. Further, the culture solution may be added by concentrating it or suspending the bacterial cells in the solution.

A first feature of the present invention is that calcium chloride is used in combination with the above-mentioned flocculant-producing bacterium (Rhodococcus erythropolis). By using calcium chloride in combination, activated sludge and treated water in an organic wastewater treatment method are treated. That is, the occurrence and growth of filamentous fungi, which are the main cause of bulking, are suppressed in the separation area of and. Therefore, the present invention is particularly effective for treating wastewater in which filamentous fungi are easily generated in treated water. The second feature of the present invention is that the pH in the separation region where the activated sludge and the treated water are to be separated is preferably 8-9. That is, when the pH is 8 or less, the coagulation and separation of the activated sludge is not so promoted even when calcium chloride is used in combination with the flocculant-producing bacterium. On the other hand, when the pH is 9 or more, the coagulation and separation of the activated sludge also depends on the pH. It is not preferred because it is not promoted and the activity of the activated sludge decreases. The third feature of the present invention is that the concentration of calcium chloride in the separation region is preferably 0.25% by weight or more, more preferably 0.2% by weight or more.
It is set to 5 to 1.0% by weight. Concentration is 0.25%
When the amount is less than the above, the aggregating effect is insufficient even if the amount of the aggregating substance-producing bacterium is increased, and when the amount is 1.0% by weight or more, the aggregating effect is not increased depending on the concentration.

The fourth feature of the present invention is that the amount of the flocculant-producing bacterium added is 0.5% by weight or more, preferably 0.5 to 10% by weight, as a culture solution. If the concentration of the flocculant-producing bacterium is less than 0.5%, a sufficient flocculating effect cannot be obtained.
Further, even if added in excess of 10%, the aggregation effect was not improved depending on the added amount. It is considered that the aggregating substance-producing bacterium used in the present invention produces an aggregating substance, and the product exhibits an aggregating effect.
The same effect can be obtained by using a solution obtained by removing the bacterial cells by filtering with a membrane filter. Suitable p as described above
Experiments were carried out to determine the concentrations of H, flocculant-producing bacteria and calcium chloride, and the results are shown in FIGS. 1, 2 and 3. It is well known that the above-mentioned flocculant-producing bacteria can be cultivated in a sterilized pure culture system, but in order to industrially use these flocculant-producing bacteria, it is an open system in which various bacteria are mixed. It is necessary to be able to culture efficiently. The present inventor has examined these points and found that efficient culture can be performed in an open system in a specific liquid medium.

As the culturing method, a flocculant-producing bacterium (Rhodococcus erythropolis) pre-cultured by shaking culture in the following liquid medium was examined as a test bacterium. Composition of liquid medium Fructose 10 g / liter K ₂ HPO ₄ 5 g / liter KH ₂ PO ₄ 2 g / liter MgSO ₄ 0.2 g / liter (NH ₄ ) ₂ SO ₄ 0.5 g / liter Yeast extract 0.5 g / liter NaCl 0.1 g / liter

Next, 150 ml of the above liquid medium is added to 5
The mixture was placed in a 00 ml Erlenmeyer flask, inoculated with 5 ml of inoculum, and cultured at 30 ° C. with shaking. The titer and bacterial growth of the culture solution were as follows: 80 ml of 5,000 mg / liter kaolin solution, 10 ml of 10% CaCl ₂ solution, 0.5 ml of culture solution, and 100 ml graduated cylinder. After stirring, the pH of the reaction solution was adjusted to pH 8 with NaOH, and then the whole was again well stirred and allowed to stand, and after 5 minutes, the turbidity (OD ₅₅₀ ) of the clear water was measured to determine the growth amount of the bacteria OD _660. Sought by. It should be noted that the OD was also obtained when using a well-known phthalic acid medium as a comparative example and when using a pure fructose-based medium.
₅₅₀ and OD ₆₆₀ were calculated. As a result, the result shown in FIG. 4 was obtained. From the results of FIG. 4, the known phthalic acid medium had a titer of 26% of that of the pure culture system, whereas the fructose medium open culture system had a titer of 88%, and the fructose medium had a sufficient titer even in the open system. It was found to be able to grow. The best results were obtained when the pH of the medium was 8-9, especially 8.5. A culture time of about 5 days is sufficient.

In order to facilitate the industrial use of the agglutinating substance-producing bacterium as described above, it is preferable to handle the aggregating substance-producing bacterium as a powder rather than as a culture solution. In the present invention, pulverization of the culture solution of the flocculant-producing bacteria was attempted by the freeze-drying method. That is, 200 ml of the culture solution cultivated in the fructose liquid medium was placed in a 1 liter freeze-drying container, and freeze-dried with a freeze dryer (manufactured by Taihei Kagaku Co., Ltd.) to obtain powder. Sterile distilled water was added to the obtained powder so as to have the same weight as that before freeze-drying, and the mixture was reconstituted to examine the ratio of surviving bacteria. As a result, 57.1% was stored for 1 day and 32.3 was stored for 1 month. %, Storage for 6 months gave a result of 30.6%. In addition, 5 ml of the above-condensed sample was added to 100 ml of fructose liquid medium and shake-cultured at 30 ° C., and the growth amount of the bacteria was examined. As shown in FIG. 5, the titer was freeze-dried on the third day of culture. It proliferated to the same extent as before and had the same aggregating activity. Therefore, according to the present invention, the aggregate-producing bacteria can be sufficiently handled as a powder, and the aggregate-producing bacteria can be restored with a simple culture facility.
It is possible to industrialize an organic wastewater treatment method using a flocculant-producing bacterium.

[0014]

EXAMPLES Next, the present invention will be described more specifically by way of examples. By applying flocculant-producing bacteria to the bulking sludge artificially generated in the continuous mixed culture tank, the addition amount and method of adding calcium chloride and flocculant-producing bacteria were changed, and the effect of suppressing bulking was examined. did. Experimental Method (a) Test Raw Water In the test, concentrated raw water of BOD 100 g / liter having the composition shown in Table 1 below was prepared, and diluted with tap water to a concentration suitable for the treatment conditions.

[Table 1] (Substrate composition of synthetic wastewater) (The unit of the numerical values in the table is mg / liter except pH.) It has been verified that the above synthetic wastewater has a substrate composition that is extremely prone to filamentous bulking, and was selected based on the results.

(B) Activated sludge In the experiment, the activated sludge used in the experiment was the one acclimated in the batch type mixed culture tank using the synthetic wastewater shown in Table 1 above. This activated sludge is an activated sludge having a good sedimentation property. When this activated sludge is continuously cultivated under the treatment conditions shown in Table 2 below, the activated sludge becomes a filamentous bulking state about 6 to 8 days after the start of water passage.

[Table 2] (Processing conditions) Filamentous microorganisms in this activated sludge often had pseudo-branching, cell diameter was 0.8-1.2 μm, cell shape was oval and Gram stain was (-). According to the classification method of Eikelboom and Jenkins, It is classified as Sphoerotilus natans.

(C) Experimental apparatus As shown in FIG. 6, a continuous mixing culture tank made of transparent vinyl chloride resin having an aeration tank capacity of 8 liters and a sedimentation separation tank of 2 liters was used for the experiment. The raw water to be tested was continuously supplied to the aeration tank at a predetermined concentration and water amount by a metering pump. Air stones were used for aeration so that DO would always rise in the aeration tank by air. The water temperature was room temperature and was 22 to 25 ° C. during the experiment. (D) Addition conditions When activated sludge became bulking state (SVI 400 ml / g or more) from the start of water flow, calcium chloride and flocculant-producing bacterial culture solution were added under the addition conditions shown in Table 3 below to activate the sludge. The effect of suppressing bulking was examined by the daily change of SVI of sludge. As the addition method, a 25% calcium chloride solution and a culture solution of a flocculant-producing bacterium were mixed in an amount suitable for the addition conditions, and the mixture was put into an aeration tank and pH was adjusted to 8.5 with 1N NaOH.
It was adjusted to 9.0. Culture medium is fructose liquid medium 5
What was shake-cultured for a day was used. The titer of this culture was 2.2-2.5.

[0017]

[Table 3] (Additional conditions) * After adding the amount shown on the left once, 0.25% of calcium chloride was added for 5 days from the next day. (E) Analysis The items shown in Table 4 below were measured daily.

[Table 4] (Samples and analysis items)

Results and Consideration (b) Examination of Calcium Chloride Addition The amount of calcium chloride added was 0.062, 0.25, 0.
It was changed to 62% and added once a day for 5 days, and the effect of suppressing bulking was examined. Figure 7 shows SV ₃₀ , MLSS, SV
It shows the change with time of I. Calcium chloride 0.
Under the condition of adding 062 to 0.25%, the effect of improving the settling compaction of activated sludge was not recognized, but under the condition of adding 0.62%, the SV started to decrease from the 3rd day of addition and the settling property was good until the 9th day. , And then SV rose again. In addition, according to the decrease in SV, microscopic observation revealed that filamentous microorganisms (S
phoerotilus natans) is decreased, it seems that the addition of a large amount of calcium chloride has the effect of inhibiting the growth of filamentous microorganisms. (B) Bulking inhibitory effect of flocculant-producing bacteria The amount of calcium chloride added was fixed at 0.62%, and the flocculant-producing bacterial culture solution was added at 2, 5, or 10%, and the bulking inhibitory effect was added. It was investigated. The results are shown in Fig. 8. The effects of improving sedimentation compaction and maintaining bulking were shown depending on the amount of culture medium added.

FIG. 9 shows the results of comparison of the time-dependent change in SVI between the case where raw water is continuously flowed in and the state of air aeration when 0.62% of calcium chloride and 5% of culture solution are added. Immediately after the addition, the SVI decreases from 500 ml / g to 100 ml / g due to the aggregating action of the culture solution. After that, the agglomeration effect continues even after 24 hours in the air aeration state, but the cohesive force decreases with the passage of time in raw water inflow, and after 24 hours, the SVI is 400 ml / g and the sludge sedimentation property is close to the original state. I will return until. The pH also drops from 8.8 immediately after the addition to 7.6 after 24 hours. The causes of the decrease in the coagulation effect in the case of inflow of raw water are (1) growth of filamentous bacteria (2) disassembly of flocs by aeration (3) decrease in pH (4) outflow of calcium ions out of the aeration tank system (5) ) It is possible that the coagulation culture fluid is diluted and flows out of the system.

FIG. 10 shows changes with time in the residual calcium ion concentration in the aeration tank when 0.62% of calcium chloride and 5% of the culture solution were added. About 25% is accumulated in sludge, and the remaining 75
It was found that the% was discharged out of the system together with the treated water. In a continuous mixed culture tank, calcium ion is present in the system and
Since it is necessary to adjust the pH of the raw water to 8.0 or more, the pH of the raw water was adjusted to 8.5 and the effect of inhibiting the bulking substance-producing bacteria from bulking was examined under the condition of supplementing with calcium chloride. Figures 11 and 12 show that the amount of calcium chloride added was kept constant at 0.62%, the flocculant-producing bacterial culture solution was added once, and then 0.25% calcium chloride alone was added for 5 days, followed by bulking. This is the result of examining the suppression effect. In the condition of adding 2% of culture solution (titer 2.2-2.5), the inhibitory-lasting effect did not appear, but in the condition of adding 5% and 10%, the SV started to decrease 5 days after the addition, and the sludge for 20 days or more thereafter. The sedimentation property of No. 2 was good, and a sustained effect was observed. However, it goes without saying that the added amount of the culture solution largely depends on the aggregation titer of the culture solution. Therefore, it goes without saying that the amount of the culture solution added is not necessarily 5% or more. With respect to the effect on the treatment function of FIG. 12, the reason that the treatability deteriorates when the amount of the flocculant-producing bacterium added is 2% or less is that the MLSS concentration is decreased due to the outflow of sludge.
Therefore, when the sedimentation of sludge was improved by adding 5% or more of the flocculant-producing bacteria, the processability was maintained in a good state. However, as mentioned above, the amount of culture solution added was 5
It is not limited to% or more. The above results indicate that the sedimentation compaction property of the bulking sludge was improved by the synergistic effect of the growth inhibitory effect of the filamentous microorganisms by calcium chloride and the aggregation promoting effect by the aggregate-producing bacteria.

[0021]

According to the present invention as described above, the road cot
In an organic wastewater treatment method using a Cass erythropolis flocculant-producing bacterium, by using this flocculant-producing bacterium and calcium chloride in combination, the generation of filamentous fungi, which is the main cause of the bulking phenomenon, is suppressed, and activated sludge and treated water Of the activated sludge and treated water are further remarkably promoted by controlling the pH of the separation area, the flocculant-producing bacteria and the concentration of calcium chloride within a specific range. Also, the Road Coccus erythropol to be used
Since the flocculant-producing bacterium can be efficiently cultured in a fructose liquid medium in an open system, it can be industrialized at a cost. Furthermore, even if the above culture solution is freeze-dried and pulverized, the number of viable cells is not significantly reduced, and by reculturing in condensate, it rapidly proliferates and exerts a coagulation titer. Cultivation equipment is not required, and the organic wastewater treatment method using the flocculant-producing bacteria can be economically implemented.

[0022]

[Brief description of drawings]

FIG. 1 is a diagram showing a result of an example of the present invention.

FIG. 2 is a diagram showing a result of an example of the present invention.

FIG. 3 is a diagram showing a result of an example of the present invention.

FIG. 4 is a diagram showing a result of an example of the present invention.

FIG. 5 is a diagram showing a result of an example of the present invention.

FIG. 6 is a diagram showing an apparatus used in the present invention.

FIG. 7 is a diagram showing a result of an example of the present invention.

FIG. 8 is a diagram showing a result of an example of the present invention.

FIG. 9 is a diagram showing a result of an example of the present invention.

FIG. 10 is a diagram showing a result of an example of the present invention.

FIG. 11 is a diagram showing a result of an example of the present invention.

FIG. 12 is a diagram showing a result of an example of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naofumi Hachimachi 4-25-25 Minamikoyasu Kimitsu City, Chiba Examiner Koichi Nakano (56) References JP-A-54-31965 (JP, A) JP-A-58 -183910 (JP, A) JP-A-63-126597 (JP, A)

Claims (2)

[Claims] 1. A method for producing Rhodococcus erythropolis flocculant in an organic wastewater treatment method using an activated sludge method.
Cultures obtained by culturing in an open system in fructose medium
A method for suppressing the generation and growth of filamentous fungi in a separation area between activated sludge and treated water, which comprises allowing a nutrient and calcium chloride to exist in the treatment system. 2. A Rhodococcus erythropolis aggregate
Of quality-producing bacteria in fructose liquid medium in an open system
Characterized in that it is obtained by freeze-drying the culture solution obtained by
Generation inhibitor of filamentous fungi that.