JP3136458B2 - How to grow iron-oxidizing bacteria - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biological treatment of wastewater, and more particularly to a method of growing iron-oxidizing bacteria suitable for treating wastewater containing chloride ions and ferrous iron.

[0002]

2. Description of the Related Art Wastewater containing ferrous iron is mainly used in the steel industry,
It is generated from the metal smelting industry and mines. For example, in the steelmaking industry, it is generated in large quantities when manufacturing cold-rolled steel sheets or surface-treated steel sheets by zinc plating, tin plating, or the like. In other words, in order to remove scale, dirt, oxide film, rust, etc. on the steel sheet surface, the steel sheet is washed (pickling treatment) with sulfuric acid or hydrochloric acid, and the pickling treatment is widely used for cleaning steel materials. ing. For pickling treatment of these steel materials, hydrochloric acid, sulfuric acid, etc. having a concentration of about 3 to 20% are often used. These acids are used for a certain period of time or more, and are discarded when the pickling ability decreases. Further, after pickling, the steel material is washed with a large amount of water to remove hydrochloric acid, sulfuric acid and the like adhering to the steel material, and these washing waters are also discarded.

[0003] The pH of these wastewaters is as low as 2 to 3 and contains a large amount of ferrous iron, so that they cannot be discharged into public water bodies as they are. Furthermore, in the case of pickling drainage of a surface-treated steel sheet such as zinc plating or tin plating, metal ions such as zinc, tin, and chromium are contained in addition to divalent iron. Further, it may contain an organic compound used for obtaining good plating properties. Therefore, these metal ions and organic compounds represented by COD need to be removed before being discharged into public water bodies, like ferric iron.

[0004] Such a method for removing ferrous iron in wastewater is roughly classified into a physicochemical method and a biological method.

[0005] As a physicochemical method, there is a method in which ferrous iron is first air-oxidized to ferric iron and removed as ferric hydroxide. However, the rate of oxidation of ferrous iron to ferrous iron is
When the pH is 4 or less, the reaction is extremely slow and the reaction hardly proceeds. For example, only 5% of the reaction progresses in 150 days (eg, W. Stam, JJ Morgan, “General Water Chemistry”, Kyoritsu Shuppan, pp. 500-501). Therefore, usually, an alkaline agent such as calcium hydroxide or calcium carbonate is added to waste water containing ferrous iron to adjust the pH to 9 to 9.
The ferrous hydroxide was maintained at 5, and a large amount of air was blown to oxidize ferric iron to ferric iron, and then removed as ferric hydroxide.
The ferric hydroxide has a low solubility of 5.6 mg / l or less when the pH is 4 or more, and has good sedimentation, so that the outflow into the treated water is small. If the pH is not adjusted to 9 or more, the solubility does not become 5.6 mg / l or less, and the sedimentation speed is low, so that it is hardly used. Furthermore, a method of oxidizing ferric iron contained in wastewater to ferric iron using a chemical such as sodium hypochlorite, hydrogen peroxide, or ozone, and treating it as ferric hydroxide is widely known. ing.

[0006] Next, as a biological method, ferrous iron is added to 3
There is a method using an iron-oxidizing bacterium that grows using energy generated when oxidizing iron. Iron-oxidizing bacteria are roughly classified into neutral and filamentous bacteria and acidic and non-filamentous bacteria. The bacteria used here are the latter acidic and non-filamentous bacteria, and are chemically synthesized independent bacteria, Thiobacillus ferrooxidans (T
hibacillus ferrooxidan
s) is a representative bacterium (for example, “Soil microbial experiment method”, Yokendo, pp. 329-331, 1975). JP-B-47-38981, JP-B-55-18559, JP-B-55-22345, and JP-B-57-44
No. 393 in wastewater described in JP-A-393
Wastewater subject to biological methods that oxidize iron by iron-oxidizing bacteria to iron is mine, coal mine, smelting wastewater, etc., and the bacteria used are iron-oxidizing bacteria present in metal mine wastewater. . Further, the method using an iron oxidizing bacterium described in JP-A-63-51076 is an aggregate of bacteria living in a water collecting pit discharged from a pickling process and a plating process related to steel. This is a method that uses iron-oxidizing bacteria in sludge and slime to oxidize ferrous iron to ferric iron and at the same time remove organic matter.

[0007] In the biological method using these iron-oxidizing bacteria, when treating wastewater containing ferrous iron with an iron-oxidizing bacterium inhabiting or having a pH of 2 to 3, ferrous iron is removed at a low pH stage. It can be quickly oxidized to trivalent iron, and can be recovered as ferric hydroxide at a pH of about 4. Trivalent iron has a pH of about 4 and can be precipitated and removed as ferric hydroxide, but other metals such as zinc and tin do not form hydroxides. Therefore, there is an advantage that only iron can be separated and collected from other metals.

[0008]

However, these conventional methods for treating wastewater containing ferrous iron have the following problems.

First, as for the physicochemical method, the method of oxidizing ferrous iron to ferric iron by aeration at a low pH stage and recovering it as ferric hydroxide has a very slow processing speed and is not practical. Is almost impossible. An alkaline agent is added to the wastewater containing ferrous iron to maintain the pH at 9 to 9.5, and a large amount of air is blown to air-oxidize the ferric iron to ferric iron. In the method of recovering, metals other than iron also precipitate as hydroxides, so it is not possible to separate and recover only iron, and also a large amount of sludge is generated, and a large amount of calcium compounds, iron, zinc, tin, etc. There is a problem that the effective use of sludge becomes almost impossible because of containing hydroxide. Furthermore, in the method of oxidizing ferrous iron with a chemical, it is difficult to control the amount of the oxidizing agent added, and the quality of treated water is not stable. Further, when the concentration of divalent iron is high, there is a disadvantage that the processing cost becomes extremely high.

[0010] The following problems still remain in conventional biological methods using iron-oxidizing bacteria.

First, usually, iron oxidizing bacteria are often found in places where drainage occurs from mines containing metal sulfide ores, particularly pyrite (FeS ₂ ), and in pickling drainage pits in steel mills. Sludge and sludge are collected from these locations, and iron-oxidizing bacteria are grown using a solution centered on FeSO ₄ (eg, 9K medium, “Soil microbial experiment method”, Yokendo, p. 394). Often used for wastewater treatment. However, the place where such iron-oxidizing bacteria can be obtained is limited to a very special place where the pH is low, ferrous iron is present, and an aerobic atmosphere is maintained. For this reason, without such an environment, it is very difficult to grow iron-oxidizing bacteria. Therefore, it is a practically important task to establish a technique for culturing iron-oxidizing bacteria in large quantities.

Further, such an iron-oxidizing bacterium often lives in an environment containing metal sulfides, as shown in the reaction formula (1).

[0013]

Embedded image 2FeS ₂ + 2H ₂ O + 7O ₂ → 2FeSO ₄
+ 2H ₂ SO ₄ 2FeSO ₄ + 2H ₂ SO ₄ + O ₂ → 2Fe ₂ (S
O ₄ ) ₃ + 2H ₂ O

Therefore, the conventional iron oxidizing bacteria are FeSO
₄ can be oxidized, but when chlorine ions such as FeCl ₂ are present, there is a drawback that chloride ions are easily inhibited. It is widely accepted that chloride ions have an inhibitory effect on the growth of certain bacteria, such as nitrifying bacteria. For steel drainage,
For example, when this iron oxidizing bacterium is used for pickling wastewater using HCl, the chloride ion concentration is 3000 to 4%.
The limit is about 000 mg / l. When the chlorine ion concentration exceeds this, the oxidation rate decreases rapidly. Therefore,
It is extremely important to establish a technique for rapidly and cultivating iron oxidizing bacteria having high chloride ion resistance in a large amount.

[0015]

The method for growing an iron-oxidizing bacterium of the present invention is as follows.

[0016] Activated sludge collected from a treatment facility for decomposing organic matter in organic wastewater is put into an aeration tank, and wastewater containing ferrous iron is passed through the aeration tank, and a nitrogen compound and a phosphorus compound are added. A method for growing iron-oxidizing bacteria, comprising adjusting the pH of a tank to 1.0 to 3.0 and blowing oxygen-containing gas into an aeration tank to cause iron-oxidizing bacteria to grow from activated sludge.

[0017] Activated sludge collected from a treatment facility for decomposing organic matter in organic wastewater is put into an aeration tank, a wastewater containing ferrous iron and chloride ions is passed through the aeration tank, and a nitrogen compound and a phosphorus compound are added. Then, adjust the pH of the aeration tank to 1.
A method for growing iron-oxidizing bacteria, characterized in that chloride-resistant iron-oxidizing bacteria are grown from activated sludge by adjusting the oxygen-containing gas to 0 to 3.0 and blowing an oxygen-containing gas into an aeration tank.

[0018] A coke plant wastewater of an ironworks is diluted with seawater, and activated sludge having chlorine ion resistance collected from a treatment facility for decomposing organic matter in the seawater-diluted wastewater is charged into an aeration tank. The wastewater containing chlorine ions is passed through, and a nitrogen compound and a phosphorus compound are added, the pH of the aeration tank is adjusted to 1.0 to 3.0, and oxygen-containing gas is blown into the aeration tank to remove chlorine from the activated sludge. A method for growing iron-oxidizing bacteria, comprising growing iron-oxidizing bacteria having ion resistance.

Activated sludge collected from a treatment facility that decomposes organic matter in organic wastewater is put into an aeration tank, effluent containing thiosulfuric acid is passed through the aeration tank, and a nitrogen compound and a phosphorus compound are added. After the oxygen-containing gas is blown into the to grow the sulfur-oxidizing bacteria, the pH of the aeration tank is adjusted to 1.0.
A method for growing iron-oxidizing bacteria, characterized in that chlorine-resistant iron-oxidizing bacteria are grown from sulfur-oxidizing bacteria by blowing oxygen-containing gas into the aeration tank, the iron-oxidizing bacteria being adjusted to -3.0.

When the oxygen-containing gas is blown into the aeration tank, the oxidation / reduction potential (OR
P) is adjusted to +550 mV to +600 mV, and the amount of oxygen-containing gas blown into the aeration tank is adjusted so that the dissolved oxygen (DO) in the aeration tank is adjusted to 1 to 5 mg / l. How to grow iron-oxidizing bacteria.

[0021]

The operation of the present invention will be described below in detail.

[0022] In general, iron oxidizing bacteria represented by Chiobachirasu-ferrooxidans is believed to use CO ₂ in air rather than organic as a carbon source. In addition, the pH at which such iron-oxidizing bacteria can live ranges from 1 to 3.
Therefore, propagation from activated sludge having a pH of 6 to 8, which is generally treating organic matter from municipal sewage or industrial wastewater, has not been attempted. For this reason, iron oxidizing bacteria have been attempted to proliferate mainly from sludge at a pH of 1 to 3, such as pits of mine drainage and steel mill drainage.

The present inventors have found that activated sludge which treats organic matter from municipal sewage and industrial wastewater also inhabits sulfur-oxidizing bacteria that oxidize inorganic substances such as reducing sulfur compounds. Proliferated successfully. This sulfur-oxidizing bacterium is resistant to chloride ions and is considered to be a bacterium of the genus Thiobacillus. Further, as the sulfur-oxidizing bacteria belonging to the genus Thiobacillus, the pH is 1 to 3 such as Thiobacillus thiooxidans.
The active species are also known.

For this reason, activated sludge, which treats organic matter from municipal sewage and industrial wastewater, oxidizes ferrous iron belonging to the same genus Thiobacillus at a pH of 1 to 3 and has resistance to chloride ions. It is presumed that some iron-oxidizing bacteria also inhabit, and it could be easily proliferated from activated sludge that treats organic matter in municipal sewage and industrial wastewater.

Activated sludge that treats organic matter from municipal sewage and industrial wastewater is mainly heterotrophic bacteria that decompose and proliferate organic matter. Chlorine ion concentration of about 20
It was thought that even at 000 mg / l, organic substances could be treated.

From the above, the present inventor tried to grow iron-oxidizing bacteria and chloride-resistant iron-oxidizing bacteria from activated sludge which treats organic matter in municipal sewage and industrial wastewater. In other words, iron oxidizing bacteria that have a pH of 6 to 8 and that have a large amount of organic substances and that live in a harsh environment may have stronger resistance than conventional iron oxidizing bacteria, He thought that it was highly resistant to chloride ions.

First, a method of acclimating and growing iron oxidizing bacteria having chlorine ion resistance from activated sludge in an activated sludge treatment plant that treats organic matter from municipal sewage and industrial wastewater will be described.

Activated sludge collected from the aeration tank of the sewage treatment plant is put into the aeration tank of the iron oxidizing bacteria treatment apparatus, and the sludge is settled and the supernatant is discharged. When the returned sludge that has already been concentrated is used, it may be used as it is. Next, an aqueous solution of ferric sulfate having an Fe ²⁺ concentration of 500 to 2000 mg / l, and a nitrogen compound and a phosphorus compound as trace nutrients are added. As the nitrogen compound, ammoniacal nitrogen (NH ₄ −
N) is desirable, and 5 to 20 mg / l is added. Phosphate (PO ₄ -P) is desirable as the phosphorus compound, 1 to 1
Add 0 mg / l. In addition, rice bran or the supernatant of rice bran may be used as the phosphorus compound.

Then, while controlling the pH of the aeration tank to 1 to 3, aeration with an oxygen-containing gas is continuously performed, and it is confirmed by water quality analysis that Fe ^{2+ of} the mixed solution is oxidized to Fe ^3+. . In this case, since the pH of the aeration tank is adjusted to 1 to 3 suitable for iron oxidizing bacteria with an acid or alkali, most of the organic matter decomposing bacteria having a neutral pH and being active are killed. Here, the oxygen-containing gas means that oxygen is 20
It is air or an inert gas containing up to 100%, and sulfuric acid is preferred as the acid for pH adjustment, and sodium hydroxide is preferred as the alkali.

When Fe ²⁺ is oxidized by 90% or more in the aeration tank, the sludge is settled, the supernatant is discharged, and the above-mentioned operation is repeated. Then, when the time during which Fe ²⁺ is oxidized by 90% or more is within 24 hours, it is considered that iron oxidizing bacteria have proliferated to some extent, and the process proceeds to continuous processing.

The amount of the oxygen-containing gas blown into the aeration tank is determined as follows. First, from the experimental results, the ORP in the state where ferrous iron was almost completely oxidized to trivalent iron was about +550 to +550.
It was found that it was about +600 mV (based on the Ag / AgCl electrode). Therefore, the ORP of the aeration tank is increased by +
550 mV to +600 mV (based on Ag / AgCl electrode)
The amount of the oxygen-containing gas may be controlled so as to maintain the pressure.
Maintaining the ORP of the aeration tank at more than +600 mV (based on the Ag / AgCl electrode) is uneconomical due to an excessive amount of aeration. In addition, the processing amount is large, and the
When P does not increase to +550 mV (based on the Ag / AgCl electrode), it is effective to increase the oxygen concentration in the oxygen-containing gas instead of increasing the amount of the oxygen-containing gas. In order to increase the oxygen concentration in the oxygen-containing gas, an oxygen-enriched film, PSA, or the like may be used. Further, pure oxygen gas may be used.

The continuous processing is performed as follows. First, 2
The wastewater containing ferrous iron is supplied such that the hydraulic residence time (HRT) of the aeration tank of the treatment device is 12 hours. At the beginning of wastewater supply, the ORP of the aeration tank is +550 mV or less (Ag /
AgCl electrode reference), and it is very difficult to maintain it at +550 mV or more. Therefore, the operation is performed such that the DO of the aeration tank is maintained at 1 to 5 mg / l using the DO of the aeration tank as an index. If DO is present at about 1 to 5 mg / l in the aeration tank, iron oxidizing bacteria will not be inhibited by DO deficiency. Further, maintaining the DO in the aeration tank at 5 mg / l or more results in an excessive amount of oxygen-containing gas, which is uneconomical. If the ORP in the aeration tank is rapidly increased at a stage where the iron oxidizing bacteria are not sufficiently grown, the amount of oxygen-containing gas increases, which tends to destroy the flocs of the iron oxidizing bacteria. Initially, it is desirable to control the amount of oxygen-containing gas using the DO of the aeration tank as an index.

After the start of the supply of the wastewater, the fermentation of the iron-oxidizing bacteria progresses, and the oxidation reaction from Fe ²⁺ to Fe ³⁺ progresses, the ORP in the aeration tank gradually rises, and the amount of oxygen-containing gas is adjusted by the ORP. Becomes possible. ORP of aeration tank is + 550mV
(Ag / AgCl electrode reference) or more, the F
e ²⁺ is hardly detected, and CO
D also decreases significantly. Therefore, it is desirable that the lower limit value of the ORP functioning as the wastewater treatment be +550 mV. When the ORP of the aeration tank can be maintained at +550 mV or more, the HRT of the aeration tank is 12 hours, and the chloride ion concentration of the wastewater is 500 to 2000 mg every 7 to 10 days.
/ L, and finally the concentration of chlorine ions in the wastewater. The chlorine ion concentration of the wastewater can be up to about 20,000 mg / l of the chloride ion concentration of seawater.

Further, thereafter, the supply amount of drainage is increased every 7 to 10 days so that the HRT of the aeration tank becomes 12 hours → 8 hours → 6 hours → 4 hours → 3 hours → 2 hours → 1 hour,
The HRT according to the Fe ²⁺ concentration of the wastewater is determined by examining the treatment performance. In this way, it is possible to easily grow iron oxidizing bacteria that are resistant to chloride ions. Even if the chloride ion concentration in the wastewater increases to about 20,000 mg / l, the oxidation rate of ferrous iron to ferric iron can be maintained at 99% or more. Further, in this case, seawater can be used as the diluent as chlorine ions.

In this way, the activated sludge of the municipal sewage treatment plant, which mainly decomposes organic matter, is converted into inorganic F
In addition to oxidizing e ²⁺ , iron-oxidizing bacteria resistant to chloride ions can be grown in large quantities at low cost.

Furthermore, in order to reduce the growth period of iron oxidizing bacteria having chloride ion resistance, it is desirable to use activated sludge from a wastewater treatment plant (aqueous water) at a steelworks coke plant.
That is, since the activated sludge is used after the coke plant wastewater is diluted 3 to 5 times with seawater, the chlorine ion resistance has already reached 20,000 mg / l, which is equivalent to seawater. Therefore, it becomes possible to grow iron-oxidizing bacteria at the same chloride ion concentration as seawater from the beginning. in this case,
It is possible to shorten the growth period of chloride-resistant iron-oxidizing bacteria by 3 to 5 months.

[0037] Further, it is also possible to grow iron oxidizing bacteria resistant to chloride ions by using sulfur oxidizing bacteria grown from activated sludge in municipal sewage treatment plants and ironworks coke plant wastewater treatment plants using thiosulfuric acid. It is. In this case, the growing sulfur oxidizing bacteria are already resistant to chloride ions by 50.
Since it is about 00 to 6000 mg / l, it is possible to shorten the growth period of the iron oxidizing bacteria also having chloride ion resistance by 1 to 2 months.

[0038]

EXAMPLE 1 The method of the present invention was applied to the growth of iron-oxidizing bacteria for treating surface treated steel plate wastewater generated from an ironworks.
The treated wastewater has a pH of 2 to 3 and an Fe ²⁺ concentration of 500 to 200.
0 mg / l, Cl ^- concentration of 1000-15000 mg /
1 and the fluctuation range of the Cl ^- concentration is large, so that the conventional treatment method using iron oxidizing bacteria cannot be used as it is. In addition, 2000-3000mg of zinc ions
/ L, 50 to 100 mg / l of tin ion and about 50 to 100 mg / l of trivalent chromium ion. The water temperature of the waste water is 10 to 35 ° C.

FIG. 1 shows an apparatus for growing iron-oxidizing bacteria. The apparatus comprises an aeration tank 3 for growing iron oxidizing bacteria, a sludge settling tank 5 for separating iron oxidizing bacteria and treated water, a blower 14 for blowing oxygen-containing gas, and the like. In the lower part of the aeration tank 3, a fine bubble type diffuser 4 made of ceramics having a pore diameter of 0.5 mm is provided.

First, an activated sludge mixed solution (activated sludge concentration: 1000 mg / l) from a sewage treatment plant that treats organic matter in municipal sewage is charged into the aeration tank 3 and the sludge settling tank 5.
The precipitate was allowed to settle and the supernatant was discarded. In order to acclimate iron oxidizing bacteria, the pH of the aeration tank 3 is adjusted to 2 with an acid or an alkali, and the Fe ²⁺ concentration is 1500 mg / l and zinc ions are 30
An artificial drainage of 00 mg / l, tin ion of 100 mg / l, trivalent chromium ion of 100 mg / l was added.

The aeration tank 3 has an ORP sensor 10 and a DO
A sensor 12 is installed, and the fermentation period of iron-oxidizing bacteria is set in the aeration tank 3
Is set to 3 mg / l, and blower 1 is set by DO.
Aeration was performed by controlling the number of rotations of No. 4. When the ORP (Ag / AgCl reference) of the aeration tank 3 rises to +550 mV or more, the control is changed to the ORP (Ag / AgCl reference) control, and the blower 14 is controlled by the ORP (Ag / AgCl reference).
The number of rotations was controlled, and aeration with air was performed. The pH of the aeration tank 3 is 10% sulfuric acid or 10%
It was controlled at 2.0 as before by an aqueous NaOH solution. Ammonium sulfate and phosphoric acid were added at 10 mg / l each as a nitrogen compound and a phosphorus compound. Water temperature was controlled at 20 ° C.

14 days after supplying the wastewater to the aeration tank 3, the ORP of the aeration tank 3 became +550 mV or more, and the Fe ^{2+ of} the treated water became 10 mg / l or less. At this stage, the sludge in the aeration tank 3 was precipitated again, the supernatant was removed, and the same artificial drainage was supplied. By repeating this operation, as shown in FIG. 2, the Fe ²⁺ of the treated water became 10 mg / l or less within 24 hours.

At this stage, the operation was shifted to a continuous operation. That is, the HRT of the aeration tank 3 was shortened every 8 days from 8 hours → 6 hours → 4 hours → 3 hours → 2 hours → 1.5 hours. Under any conditions, the amount of Fe ²⁺ in the treated water was 10 mg.
/ L or less, and it was judged that the adaptation of the iron-oxidizing bacteria was completed.

After the fermentation of the iron-oxidizing bacteria is completed, the aeration tank 3
HRT supplies artificial wastewater under the condition of 2 hours, and increases the chloride ion concentration from 1000 mg / l to 1 every 7 days.
It was increased with sodium chloride (NaCl) in 1 000 mg / l increments to 15000 mg / l. Under any of the conditions, Fe ²⁺ of the treated water was removed to 10 mg / l or less, and it was determined that the iron-oxidizing bacteria had resistance to chloride ions.

Thereafter, for about one year, the HRT of the aeration tank 3 was maintained for 2 hours, the water temperature was 10 to 35 ° C., and the chlorine ion concentration was 15,000.
Continuous treatment was performed under the condition of mg / l. As a result, as shown in Table 1, an example of the quality of the treated water, Fe ²⁺ was removed to 15 mg / l or less and COD was 15 mg / l or less as shown in Table 1. Met. As a result, it was presumed that the iron-oxidizing bacteria were also resistant to fluctuations in water temperature.

[0046]

[Table 1] (Data; average value of 10 to 12 pieces)

The concentration of the iron-oxidizing bacteria in the aeration tank 3 rapidly increased after shifting to the continuous experiment, and was 50,000 to 100,000 m
g / l. However, the sedimentability did not deteriorate, and as shown in FIG. 3, it was confirmed that the SVI, which is an index of the sedimentability, was 10 to 50, which was extremely good. Therefore, it is easy to maintain the iron oxidizing bacteria in the aeration tank 3 at a high concentration, and by using this method, the aeration tank 3 and the sludge settling tank 5
Can be made more compact.

[0048]

Embodiment 2 An activated sludge mixed solution (activated sludge concentration: 500) of a treatment plant in which an aeration tank 3 and a sludge settling tank 5 of the apparatus shown in FIG.
0 mg / l), and iron-oxidizing bacteria were acclimated in the same manner as in Example 1. However, the coke plant wastewater is 4
Since the artificial wastewater is diluted and treated twice, the artificial wastewater has a Cl ^- concentration of 15000 mg / l and an Fe ²⁺ concentration of 20 from the beginning.
00 mg / l, zinc ion 3000 mg / l, tin ion 100 mg / l, trivalent chromium ion 100 mg / l
1 composition.

As a result, the acclimatization period of the iron-oxidizing bacteria could be shortened by about 4 months as compared with Example 1. Furthermore, as a result of performing continuous treatment under the conditions of HRT of the aeration tank 3 for 2 hours, water temperature of 10 to 35 ° C., and chloride ion concentration of 15000 mg / l,
In the treated water of the continuous treatment, Fe ²⁺ was removed to 15 mg / l or less at any water temperature, and COD was 15 m / l.
g / l or less, a good result was obtained. In this way, using activated sludge that is resistant to seawater, such as activated sludge at a treatment plant that treats organic matter from the effluent of a steel mill coke plant, can acclimate chloride-resistant iron-oxidizing bacteria in a shorter period of time. It became clear what we could do.

[0050]

Example 3 A sulfur-oxidizing bacterium (concentration: 3500 mg / l) from a treatment plant for treating thiosulfuric acid-containing wastewater was introduced into the aeration tank 3 and the sludge settling tank 5 of the apparatus shown in FIG. Iron-oxidizing bacteria were acclimated from sulfur-oxidizing bacteria in the same manner as described above. Since this sulfur-oxidizing bacterium was acclimated from activated sludge and had a Cl ^- resistance of 5000 to 6000 mg / l, the artificial wastewater had a Cl ^- concentration of 5000 mg / l from the beginning.
l, Fe ²⁺ concentration 2000 mg / l, zinc ion 30
The composition was adjusted to 00 mg / l, tin ion to 100 mg / l, and trivalent chromium ion to 100 mg / l.

As a result, the acclimatization period of the iron-oxidizing bacteria could be shortened by about one month as compared with Example 1. Furthermore, as a result of performing continuous treatment under the conditions of HRT of the aeration tank 3 for 2 hours, water temperature of 10 to 35 ° C., and chloride ion concentration of 15000 mg / l,
In the treated water of the continuous treatment, Fe ²⁺ was removed to 15 mg / l or less at any water temperature, and COD was 15 m / l.
g / l or less, a good result was obtained. Thus, it was revealed that the use of sulfur oxidizing bacteria in a treatment plant that treats hydrogen sulfide wastewater allows the fermentation of iron oxidizing bacteria having chloride ion resistance in a shorter period of time.

[0052]

According to the present invention, it becomes possible to adapt and multiply chloride-resistant iron-oxidizing bacteria from activated sludge of municipal sewage and industrial wastewater. As a result, it is possible to maintain a high concentration of chloride-resistant iron-oxidizing bacteria in the aeration tank,
Effluent treatment efficiency and treated water quality are improved, and stable treatment of wastewater containing Fe ²⁺ and Cl ⁻ becomes possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an apparatus for implementing the present invention.

FIG. 2 is a diagram showing an example of acclimation of iron oxidizing bacteria from municipal sewage treatment plant activated sludge.

FIG. 3 is a view showing an example of the sedimentation of iron oxidizing bacteria acclimated from activated sludge of an urban sewage treatment plant.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drainage tank 2 Drainage supply pump 3 Aeration tank 4 Aeration tube 5 Sludge settling tank 6 Rake 7 Treated water 8 pH sensor 9 pH control device 10 ORP sensor 11 ORP control device 12 DO sensor 13 DO control device 14 Blower 15 Sludge return pump 16 Timer 17 Treated water tank 19 Sulfuric acid tank 20 NaOH tank 21 Sulfuric acid pump 22 NaOH pump

────────────────────────────────────────────────── ─── Continued from the front page (72) Inventor Yukihiro Nomura 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (56) References JP-A-8-24894 (JP, A) JP-A-63-49298 (JP, A) JP-A-60-7994 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C02F 3/34 C12N 1/20

Claims (5)

(57) [Claims] 1. Activated sludge collected from a treatment facility for decomposing organic substances in organic wastewater is introduced into an aeration tank, and the activated sludge is added to the aeration tank.
While passing through the wastewater containing valent iron, the nitrogen compound and the phosphorus compound are added, the pH of the aeration tank is adjusted to 1.0 to 3.0, and oxygen-containing gas is blown into the aeration tank to remove iron from the activated sludge. A method for growing iron oxidizing bacteria, comprising growing oxidizing bacteria. 2. Activated sludge collected from a treatment facility for decomposing organic matter in organic wastewater is introduced into an aeration tank, and the activated sludge is added to the aeration tank.
The wastewater containing valent iron and chlorine ions is passed through, and a nitrogen compound and a phosphorus compound are added.
A method for growing iron-oxidizing bacteria, characterized in that chloride-resistant iron-oxidizing bacteria are grown from activated sludge by adjusting the pH to -3.0 and blowing an oxygen-containing gas into an aeration tank. 3. An activated sludge having chlorine ion resistance collected from a treatment facility for diluting organic matter in seawater-diluted wastewater by diluting seawater from a coke plant wastewater of a steelworks into an aeration tank, and then divalent into the aeration tank. The wastewater containing iron and chlorine ions is passed through, and a nitrogen compound and a phosphorus compound are added, the pH of the aeration tank is adjusted to 1.0 to 3.0, and an oxygen-containing gas is blown into the aeration tank to cause the activated sludge. A method for growing iron-oxidizing bacteria, comprising growing chloride-resistant iron-oxidizing bacteria from a microorganism. 4. Activated sludge collected from a treatment facility for decomposing organic matter in organic wastewater is introduced into an aeration tank, and wastewater containing thiosulfuric acid is passed through the aeration tank, and a nitrogen compound and a phosphorus compound are added. After the oxygen-containing gas is blown into the aeration tank to grow the sulfur-oxidizing bacteria, the pH of the aeration tank is adjusted to 1.0 to 1.0.
A method for growing iron-oxidizing bacteria, comprising adjusting the pH to 3.0 and blowing an oxygen-containing gas into an aeration tank to grow iron-oxidizing bacteria having chlorine ion resistance from sulfur-oxidizing bacteria. 5. When blowing an oxygen-containing gas into an aeration tank,
Redox potential (ORP) based on Ag / AgCl of aeration tank
5 is set to +550 mV to +600 mV, and the amount of oxygen-containing gas blown into the aeration tank is adjusted so that the dissolved oxygen (DO) in the aeration tank is 1 to 5 mg / l. The method for growing iron-oxidizing bacteria according to item 1.