JP6425469B2 - Method of treating waste water containing reducing sulfur compounds - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a method for treating waste water which uses waste sulfur oxidizing bacteria to treat waste water containing reducing sulfur compounds.

  Waste water containing hydrogen sulfide, elemental sulfur, and reducing sulfur compounds such as thiosulfate is discharged from factories engaged in various chemical industries such as photo industry, petroleum refining industry, metal refining industry, and other chemical industries, or mines etc. Ru. The waste water containing the reducing sulfur compound has to have a high chemical oxygen demand (COD), so it needs to be discharged to the sewage after the purification treatment.

  Conventionally, as a method of treating waste water containing the reducing sulfur compound, for example, a method of oxidizing the reducing sulfur compound using an oxidizing agent such as sodium hypochlorite, hydrogen peroxide and the like, and treating the waste water (Chemical processing methods) are known. The chemical treatment method has an advantage that the waste water can be treated relatively simply by adding the oxidizing agent to the waste water. However, the chemical treatment method has the following problems: 1) the treatment cost is high because the oxidizing agent is expensive, and 2) there is a possibility that treated water containing the oxidizing agent may be discharged to sewage. is there. In particular, in recent years, regulations on chemical substances tend to be strengthened, and a treatment method with a low environmental impact is desired.

  Then, the method (biological treatment method) which oxidizes the said reducible sulfur compound using sulfur oxidizing bacteria, and processes waste water attracts attention. As a biological treatment method, the activated sludge method etc. are mentioned, for example. However, the activated sludge method has a problem that it is necessary to use a large-capacity settling tank, and it can not be implemented in a factory without a large site where the settling tank can be installed.

  As a measure to solve the above problem, the sulfur-oxidizing bacteria are immobilized on a carrier to be immobilized bacteria, the immobilized bacteria are introduced into the drainage, and the sulfur-oxidizing bacteria are maintained at a high concentration in the drainage. Thus, a method has been proposed to improve the treatment efficiency of the drainage. For example, the sulfur-oxidizing bacteria are immobilized on a saddle-type ceramic carrier to be immobilized bacteria, and the immobilized bacteria are packed inside a bioreactor to constitute a fixed-bed bioreactor, and the fixed-bed bioreactor is constructed. A biological treatment method for treating hydrogen sulfide-containing wastewater using the following has been proposed (Patent Document 1). In this method, sulfur-oxidizing bacteria adapted from sewage, activated sludge of industrial waste, using wastewater containing non-volatile reducible sulfur compounds are used.

  In addition, a method is proposed in which the above-mentioned sulfur-oxidizing bacteria are fixed to ground granulated blast furnace slag powder, calcium sulfate fine powder, calcium carbonate fine powder or the like to be immobilized bacteria, and the above-mentioned immobilized bacteria are used to treat the reducing sulfur compound-containing wastewater. (Patent Document 2). In this method, the activated sludge collected from an organic wastewater treatment plant such as municipal wastewater is grown by wastewater mainly composed of thiosulfuric acid which does not contain volatile sulfur compounds such as sulfide ions, and has a sulfur oxidizing function Pseudomonas sp. We use bacteria of genus.

Patent No. 25822695 Patent No. 3241565

It can be said that the method described in Patent Literature 1 or 2 is an effective method in that the treatment efficiency of wastewater is improved as compared with the activated sludge method. However, these methods have left unsolved problems as listed below.
1) It takes a long time until sulfur-oxidizing bacteria settle on the carrier and can stably treat the wastewater (that is, to start up the wastewater treatment).
2) It is necessary to take a long hydraulic retention time (HRT, also referred to as "aeration time") of the waste water, which is insufficient in terms of waste water treatment efficiency.
3) When waste water containing a high concentration of calcium ions in addition to reducing sulfur compounds is treated, calcium carbonate may be deposited on the immobilized bacteria, and the treatment capacity may decrease with time.

  The present invention has been made in view of the above problems. That is, according to the present invention, in addition to the small load on the environment, the waste water treatment can be started in a short time, the treatment efficiency of the waste water is high, and even when the waste water containing high concentration of calcium ions is treated, It is an object of the present invention to provide a waste water treatment method capable of treating waste water stably.

  The present inventor diligently studied the above-mentioned subject. As a result, sulfur-oxidizing bacteria are fixed to a fluid carrier made of polyurethane resin to be immobilized bacteria, and it is considered that the above-mentioned problems can be solved by carrying out aeration treatment in a fluidized bed system, and the present invention is completed. It reached. That is, according to the present invention, the following method for treating wastewater is provided.

[1] Wastewater treatment method:
According to the present invention, there is provided a method of treating waste water containing reducible sulfur compounds, wherein waste water and sulfur-oxidizing bacteria are introduced into an aeration tank and aeration treatment is carried out, wherein the waste water includes reducible sulfur compounds and calcium. In the aeration tank, the pH of the waste water is 5 or more and 8 or less in the aeration tank, using waste water containing ions, and using the immobilized bacteria in which the sulfur oxidizing bacteria are fixed as the sulfur oxidizing bacteria, as the sulfur oxidizing bacteria. A method of treating wastewater comprising flowing the immobilized bacteria and performing aeration treatment in a fluid bed system while maintaining

The waste water treatment method of the present invention is
Using the SAB-1 strain belonging to the genus Halothiobacillus as said sulfur oxidizing bacteria;
The medium containing the sulfur-oxidizing bacteria is added to the aeration tank so that the concentration of the sulfur-oxidizing bacteria is 10 ³ cfu / mL or more, and the fluid carrier is charged into the aeration tank to perform aeration treatment. Immobilizing said sulfur oxidizing bacteria on the surface of said fluid carrier, thereby obtaining said immobilized bacteria;
Performing the aeration treatment while maintaining the aeration amount at 2 m ³ / m ³ · hr or more;
It is preferable to use, as the waste water, a waste water having a reducing sulfur compound concentration of 30 mg / L or more and a calcium ion concentration of 100 mg / L or more in COD conversion;

  According to the treatment method of the present invention, in addition to the small load to the environment, the waste water treatment can be started in a short time, the treatment efficiency of the waste water is high, and the waste water containing high concentration of calcium ions is treated Waste water can be treated stably.

It is a side view which shows typically the processing apparatus for enforcing the processing method of this invention. It is a graph which shows the COD value in a batch test. It is a graph which shows the COD value in a water flow test. It is a graph which shows the amount of SS attached to the immobilized bacteria.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments, but includes all objects having the invention specific matters.

  The method for treating waste water according to the present invention is a method for treating waste water containing reducing sulfur compounds, in which waste water and sulfur oxidizing bacteria are introduced into an aeration tank and aeration treatment is performed.

[1] drainage:
"Drainage" means water to be subjected to aeration treatment. In the present invention, waste water containing reducing sulfur compounds and calcium ions is used as the waste water. In the following description, water after the aeration treatment may be referred to as "treated water".

[1-1] Reducible Sulfur Compounds:
The reducing sulfur compound means a sulfur compound having higher reducibility than sulfur dioxide (SO ₂ ) (that is, the oxidation number of sulfur is smaller than +4). For example, hydrogen sulfide (H ₂ S), elemental sulfur (S), thiosulfate (salt containing thiosulfate ion <S ₂ O ₃ ²⁻ >) and the like can be mentioned.

  In the present invention, the concentration of the reducing sulfur compound in the waste water is not particularly limited. However, it is preferable to use the waste water whose concentration of a reducible sulfur compound is 30 mg / L or more and 300 mg / L or less as COD conversion as said waste water.

[1-2] Calcium ion:
In the present invention, the concentration of calcium ions in the waste water is also not particularly limited. However, as the drainage, it is preferable to use drainage having a calcium ion concentration of 100 mg / L or more and 1,000 mg / L or less.

[1-3] Specific types of drainage:
There are no particular limitations on the type of waste water containing reducing sulfur compounds and calcium ions. For example, waste water discharged from factories operating various chemical industries such as photographic industry, petroleum refining industry, metal refining industry, and other chemical industries, or waste water discharged from mines, etc., particularly waste water discharged from an iron mill.

  In the above waste water, the concentration of reducing sulfur compounds is about 30 to 300 mg / L in terms of COD, the concentration of calcium ions is about 100 to 1,000 mg / L, and the concentrations of both reducing sulfur compounds and calcium ions are high. There is a feature. Moreover, since the said waste_water | drain may show high alkalinity with pH about 12-13, after performing pH adjustment which is mentioned later, it is preferable to use for an aeration process.

[2] Sulfur-oxidizing bacteria:
The treatment method of the present invention is a biological treatment method in which waste water is treated using sulfur oxidizing bacteria. Sulfur-oxidizing bacteria mean bacteria that live by energy obtained by oxidizing sulfur or inorganic sulfur compounds. By using sulfur oxidizing bacteria, reducing sulfur compounds (H ₂ S, S, S ₂ O ₃ ^2- etc.) in waste water can be oxidized to sulfate ion (SO ₄ ^2- ), and COD value of waste water Can be reduced. Such a treatment method is preferable in that the load on the environment is small.

  In the present invention, as sulfur oxidizing bacteria, immobilized bacteria in which sulfur oxidizing bacteria are immobilized are used as a fluid carrier made of polyurethane resin. By fixing the sulfur-oxidizing bacteria to a fluid carrier, it becomes possible to perform aeration treatment in a fluid bed system described later.

[2-1] SAB-1 strain:
In the present invention, the species of sulfur oxidizing bacteria is not particularly limited. However, it is preferable to use a SAB-1 strain belonging to the genus Halothiobacillus as the sulfur-oxidizing bacteria. The SAB-1 strain is a gram-negative, autotrophic bacterium, and as a result of BLAST homology search for its 16S rDNA, it has been found to be a strain belonging to the genus Halothiobacillus. In addition, on February 20, 2013 (the date of deposit), the SAB-1 strain receives a deposit statement at the Patent Microorganisms Depositary Center of the National Institute of Technology and Evaluation, National Institute of Technology and Evaluation, and the accession number "NITE P-1543" It is a given strain. The SAB-1 strain can be fixed on a fluid carrier more easily than other strains, and can shorten the time until the wastewater can be treated stably (that is, until the wastewater treatment is started). it can.

[2-2] Fluid carrier:
By "fluid carrier" is meant a carrier used while flowing in the waste water. In other words, it is different from the fixed carrier used by being fixed in the aeration tank.

  In the present invention, a fluid carrier made of polyurethane resin is used. In the fluid bed system, the flowability of the fluid carrier (and hence the immobilized bacteria) is directly linked to the processing efficiency. The fluid carrier made of polyurethane resin is less likely to deposit calcium carbonate, and the deposited calcium carbonate is likely to be exfoliated. Therefore, the fluid carrier made of polyurethane resin can maintain the fluidity of the fluid carrier, and even when treated with waste water containing calcium ions in high concentration, the processing capacity does not decrease with time, and is stable. It is preferable in that the waste water can be treated. On the other hand, in the fluid carrier made of ceramics, the calcium compound in the raw material may accelerate the deposition of calcium carbonate. In addition, the fluid carrier made of resin other than polyurethane resin (for example, polyolefin resin such as polyethylene resin and polypropylene resin) is less likely to deposit calcium carbonate as compared with the fluid carrier made of ceramic, and calcium carbonate deposited is Although easily exfoliated, its effect does not reach the fluid carrier made of polyurethane resin.

  "Polyurethane resin" is a generic term for resins having a urethane bond. Usually, it is a condensate of a polyisocyanate and a polyol, but a condensate of a polyisocyanate and a polyamine or a polycarboxylic acid is also included. Examples thereof include condensates of alkylene oxide-added polyether polyols having a weight average molecular weight of 3,000 and tolylene diisocyanate (such as 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate).

The shape and structure of the fluid carrier are not particularly limited as long as it has fluidity in waste water. For example, shapes such as cubic, granular, tubular and the like can be mentioned. Among them, a cubic carrier having a side of 5 to 20 mm is preferable. More specifically, product name "AQ-1" (Kanto Inoac, cube-shaped 10 mm side, porosity 97%, number of cells 47/25 mm, cell diameter 0.6 mm, true specific gravity 1.136 g / cm ³ ) etc. can be mentioned.

Sulfur oxidizing bacteria are immobilized on the surface of the fluid carrier. Therefore, the shape with a large specific surface area can increase the amount of fixed sulfur oxidizing bacteria, which is preferable. For example, a porous body such as sponge-like or net-like shape, a shape in which projections and recesses are formed on the surface, and the like can be mentioned. The specific surface area of the fluid carrier is not particularly limited. However, the range of 500 m ² / m ³ or more is preferable. If it is 500 m ² / m ³ or more, the fixed amount of sulfur oxidizing bacteria can be increased. The upper limit is not particularly limited, but is in the range of 5,000 m ² / m ³ or less, preferably 4,000 m ² / m ³ or less, and more preferably 3,000 m ² / m ³ or less.

Further, from the viewpoint of maintaining the treatment efficiency and treatment rate of the drainage, it is preferable that the surface area of the fluid carrier be within a certain range with respect to the volume of the aeration tank. Specifically, it is preferably 50 m ² or more per 1 m ³ of volume of the aeration tank. If it is 50 m ² or more, the treatment efficiency and treatment speed of the drainage can be maintained. Although the upper limit is not particularly limited, it is 1,000 m ² or less, preferably 800 m ² or less, more preferably 600 m ² or less.

In the present invention, the method for obtaining the immobilized bacteria is not particularly limited. However, it is preferable to prepare a culture medium containing the sulfur-oxidizing bacteria in the range of 10 ⁸ cfu / mL or more and 10 ¹² cfu / mL or less by preculturing the sulfur-oxidizing bacteria. In addition, a medium containing the sulfur-oxidizing bacteria is added to the aeration tank such that the concentration of the sulfur-oxidizing bacteria is in the range of 10 ³ cfu / mL or more, and the fluid carrier is charged into the aeration tank. It is preferable to fix the sulfur-oxidizing bacteria on the surface of the fluid carrier (that is, to form a biofilm) by performing aeration treatment to obtain the fixed bacteria.

By setting the concentration of the sulfur-oxidizing bacteria in the medium to 10 ⁸ cfu / mL or more, the concentration of the sulfur-oxidizing bacteria in the aeration layer can be adjusted to 10 ⁶ cfu / mL or more. Further, by setting the concentration of the sulfur-oxidizing bacteria in the aeration tank to 10 ³ cfu / mL or more, preferably 10 ⁴ cfu / mL or more, the treatment efficiency and treatment rate of the waste water can be maintained. The upper limit is not particularly limited, but is in the range of 10 ⁸ cfu / mL or less, preferably 10 ⁷ cfu / mL or less.

[3] Aeration treatment:
In the present invention, while the pH of the waste water is maintained at 5 or more and 8 or less (preferably 6 or more and 7 or less) in the aeration tank, the immobilized bacteria are caused to flow and the aeration treatment is performed in a fluid bed system. . Such a method can increase the contact efficiency between the waste water and the sulfur oxidizing bacteria, and can improve the treatment efficiency of waste water more than the fixed bed method.

[3-1] Fluidized bed method:
In the present invention, the method of causing the immobilized bacteria to flow is not particularly limited. It may be carried out exclusively by aeration, or stirring may be used in combination. The flow state of the immobilized bacteria can be adjusted by, for example, an aeration amount described later. The capacity of the aeration tank may be appropriately determined in accordance with the amount of drainage to be treated and the installation space.

[3-2] pH:
By setting the pH of the waste water to 5 or more, preferably 6 or more, the solubility of hydrogen sulfide in water can be increased, and the problem of releasing hydrogen sulfide gas derived from reducing sulfur compounds can be prevented. On the other hand, by setting the pH of the waste water to 8 or less (acidic to weakly basic region), preferably 7 or less (acidic to neutral region), carbon dioxide in the air supplied during aeration (acidic substance ) Is difficult to dissolve in the drainage. As a result, calcium ions in the waste water react with carbon dioxide to form calcium carbonate, and the calcium carbonate can be prevented from depositing on the fluid carrier, so that the fluidity of the fluid carrier (the ability to process the waste water) Can be maintained. Such a configuration is particularly effective when treating wastewater containing a large amount of calcium ions, such as wastewater discharged from a steel mill.

  In the present invention, it is also preferable to carry out the neutralization treatment of the waste water and adjust the pH thereof to 5 or more and 8 or less before introducing the waste water into the aeration tank. As described above, the waste water and the like discharged from a steelmaking plant may exhibit high alkalinity such as pH 12-13. In such a case, in the neutralization tank, a neutralizing agent such as hydrochloric acid or sulfuric acid may be added to the waste water, and the pH may be adjusted to the above range before applying the treatment method of the present invention. preferable. In addition, pH, such as waste water, can be detected, for example using pH sensor (brand name "portable ion * pH meter IM-32P", Toa DK make) which measures pH by a glass electrode method.

[3-3] Oxidation-reduction Potential (ORP):
In the present invention, the redox potential of the waste water at the time of aeration treatment is not particularly limited. However, it is preferable to perform the aeration treatment while maintaining the redox potential at -60 mV or more (more preferably -50 mV or more). The upper limit of the redox potential is not particularly limited, but is preferably +150 mV or less (more preferably +0 mV or less). In addition, ORP can be measured using the ORP sensor (brand name "portable ORP meter RM-30P", Toa DK make) which measures ORP by a platinum electrode method.

[3-4] Aeration amount:
In the present invention, the aeration amount at the time of performing the aeration treatment is not particularly limited. However, it is preferable to carry out the aeration treatment while maintaining the aeration amount at 2 m ³ / m ³ · hr or more and 10 m ³ / m ³ · hr or less. By setting the aeration amount to 2 m ³ / m ³ · hr or more, the waste water appropriately flows in the aeration tank, and the waste water and the immobilized bacteria come into good contact, so that a sufficient treatment capacity is secured. On the other hand, by setting the aeration amount to 10 m ³ / m ³ · hr or less, the flow of immobilized bacteria becomes excessive, effectively causing the biofilm formed on the surface of the fluid carrier to exfoliate or fall off. It can be prevented.

[3-5] Processing flow:
The aeration process can be performed, for example, by the following process flow. Hereinafter, the present invention will be specifically described by way of the example of the processing apparatus shown in FIG.
(1) The drainage in the drainage tank 1 is sent to the neutralization tank 3 by the feed pump 2.
(2) The pH of the waste water in the neutralization tank 3 is confirmed by the pH sensor 5.
(3) When the pH of the waste water is out of the range of 5 or more and 8 or less, the hydrochloric acid in the HCl tank 7 is fed by the feed pump 6 while the waste water in the neutralization tank 3 is stirred by the stirrer 4 The solution is sent to the neutralization tank 3 to adjust the pH of the waste water to 5 or more and 8 or less.
(4) The pH-adjusted drainage in the neutralization tank 3 is transferred to the aeration tank 18.
(5) The drainage carrier in the aeration tank 18 is charged with a fluid carrier and a medium for sulfur oxidizing bacteria.
(6) Air is sent from the blower 17 into the aeration tank 18 through the aeration pipe 8 to perform aeration processing. As a result, immobilized bacteria in which sulfur-oxidizing bacteria are immobilized on the surface of the fluid carrier are obtained, and aeration of the waste water is performed. At this time, the state of the drainage is checked at any time by the pH sensor 12, the ORP sensor 15, and the DO sensor 16 (DO: Dissolved Oxygen; the amount of dissolved oxygen). When the pH of the waste water is out of the range of 5 or more and 8 or less, the hydrochloric acid in the HCl tank 11 is sent to the aeration tank 18 by the feed pump 10, or the sodium hydroxide aqueous solution in the NaOH tank 14 is The liquid is fed to the aeration tank 18 by the feed pump 13 to adjust the pH of the waste water to 5 or more and 8 or less.
(7) The treated water after the aeration treatment is discharged from the water outlet 22.

  Hereinafter, the processing method of the present invention will be more specifically described by examples and comparative examples. In the following examples and the like, the processing apparatus shown in FIG. 1 was used. The volume of the aeration tank 18 was 520 L, and the volume of the neutralization tank 3 was 24 L.

<Batch test>
In Example 1 and Comparative Examples 1 and 2 below, the treatment method was evaluated by a batch test. The "batch test" is a test in which the aeration tank is filled with drainage at the start of the test, and thereafter aeration treatment is performed without introducing new drainage into the aeration tank to evaluate the quality of treated water.

Example 1
In Example 1, factory drainage discharged from a steel mill was used as drainage. This waste water contains S ²⁻ and S ₂ O ₃ ²⁻ as components derived from reducing sulfur compounds, and also contains Ca ^{2+ in a} large amount. The water quality was as shown in Table 1. In the table, "S ₂ O ₃ ^2- -S" represents thiosulfuric acid sulfur, "SO ₄ ^2- -S" represents sulfuric acid sulfur, and "T-S" represents total sulfur. Show.

The waste water was sent to the neutralization tank 3 of the treatment apparatus shown in FIG. 1 to adjust the pH of the waste water to 8.0, and then sent to the aeration tank 18. Next, the fluid carrier was charged into the aeration tank 18. As the fluid carrier, a fluid carrier made of polyurethane (trade name "AQ-1", manufactured by Kanto Inoac) was used. The fluid carrier had a cubic shape of 10 mm × 10 mm × 10 mm and a specific surface area of 3,000 m ² / m ³ . The fluid carrier was introduced into the aeration tank 18 so that the surface area was 600 m ² per 1 m ³ of volume of the aeration tank 18.

Furthermore, the culture medium of the SAB-1 strain pre-cultured in advance was charged into the aeration tank 18. The medium was a medium containing the SAB-1 strain at a concentration of 10 ¹⁰ cfu / mL. The medium was introduced into the aeration tank 18 such that the concentration of the SAB-1 strain was 10 ⁷ cfu / mL, and aeration treatment was performed. The drainage in the aeration tank 18 was controlled such that the pH was 6 or more and 7 or less, and the redox potential (ORP) was -50 mV or more and +0 mV or less. Also, the aeration amount was controlled to 2 m ³ / m ³ · hr or more and 6 m ³ / m ³ · hr or less. In the process of aeration treatment, the SAB-1 strain and the inorganic substance were gradually attached to the surface of the fluid carrier to form a biofilm. In other words, immobilized bacteria in which the SAB-1 strain was immobilized on the surface of the fluid carrier were obtained.

  After the aeration treatment was started, the COD value of the treated water was periodically measured to confirm the change with time of the COD value. The results are shown in FIG. As shown in FIG. 2, the COD value of the treated water continued to decrease after the aeration treatment started, and fell to about 10 mg / L in about one hour after the aeration treatment started, and became a steady state.

Comparative Example 1
The aeration was carried out in the same manner as in Example 1, except that the activated sludge mixed solution of the sewage treatment plant of municipal sewage was introduced instead of the culture medium of the SAB-1 strain pre-cultured in advance into the aeration tank 18. I did the processing. The activated sludge was introduced into the aeration tank 18 such that the concentration of the activated sludge was 1,000 mg / L. Similar to Example 1, the results of confirming the change with time of the COD value are shown in FIG. As shown in FIG. 2, the COD value of the treated water was slower to lower than in Example 1, and reached a steady state after 20 hours, about 20 times that of Example 1.

Comparative Example 2
The aeration treatment was performed in the same manner as in Example 1 except that the fixed carrier was charged instead of the fluid carrier being charged into the aeration tank 18. As the fixed carrier, a fixed carrier made of polypropylene was used. The fixed carrier was a corrugated plate having a wave pitch of 320 mm (the distance between the wave top and the top) and a plate thickness of 4 mm, and had a specific surface area of 100 m ² / m ³ . The fixed carrier was introduced into the aeration tank 18 so as to have a surface area of 60 m ² per 1 m ³ of volume of the aeration tank 18. Similar to Example 1, the results of confirming the change with time of the COD value are shown in FIG. As shown in FIG. 2, the COD value of the treated water was slower to lower than that of Example 1, and reached a steady state after about 3 times of that of Example 1.

From the above results, it can be said that waste water treatment can be started in a short time by carrying out the aeration treatment by the fluidized bed method using the immobilized bacteria on which the SAB-1 strain is fixed.
<Water flow test>

  In Example 2 and Comparative Example 3 below, the treatment method was evaluated by a water flow test. The "water flow test" is a test to evaluate the water quality of treated water by performing aeration treatment while continuously introducing drainage into the system of the treatment apparatus. In the water passing test, the aerated water (treated water) is continuously discharged out of the system of the treatment apparatus.

Example 2
After a batch test for 48 hours was performed under the same conditions as in Example 1, a water flow test was subsequently performed. In other words, the immobilized bacteria obtained in Example 1 were used as they were. As wastewater introduced continuously, factory wastewater discharged from a steel mill was used. The water quality was as shown in Table 2.

  Similar to the batch test of Example 1, the waste water was sent to the neutralization tank 3 of the treatment apparatus shown in FIG. 1, and the pH of the waste water was adjusted to 8.0, and then sent to the aeration tank 18 . The hydraulic retention time (HRT) of the waste water in the aeration tank 18 is initially set to 12 hours, shortened to 6 hours, 4 hours, 2 hours, 1 hour every day, and thereafter HRT is fixed to 1 hour Then, I did water supply for one week. After the aeration treatment was started, the COD value of the treated water was periodically measured to confirm the change with time of the COD value. The results are shown in FIG. As shown in FIG. 3, the COD value remained at 10 mg / L or less even after 5 days after setting HRT to 1 hour, and the water treatment could be performed stably.

Comparative Example 3
After performing a batch test for 48 hours under the same conditions as Comparative Example 1, the aeration treatment was performed in the same manner as Comparative Example 2 except that a water flow test was subsequently performed. As in Example 2, the results of confirming the change with time of the COD value are shown in FIG. As shown in FIG. 3, the COD value increased after 5 days when HRT was 1 hour, and it remained at 19 to 37 mg / L.

  From the above results, it is possible to improve the treatment efficiency of the waste water by using the immobilized bacteria fixed with the SAB-1 strain and carrying out the aeration treatment by the fluidized bed method, and the waste water can be treated stably. It can be said.

<Evaluation of material of carrier>
In the following Example 3 and Comparative Examples 4 to 6, the material of the fluid carrier was evaluated.

[Example 3]
In Example 3, factory drainage discharged from a steel mill was used as drainage. The water quality was as shown in Table 1 above.

The waste water was sent to the neutralization tank 3 of the treatment apparatus shown in FIG. 1 to adjust the pH of the waste water to 8.0, and then sent to the aeration tank 18. Next, the fluid carrier was charged into the aeration tank 18. As the fluid carrier, the same polyurethane fluid carrier (trade name "AQ-1", manufactured by Kanto Inoac Co., Ltd.) as used in Example 1 was used. The fluid carrier was introduced into the aeration tank 18 so that the surface area was 600 m ² per 1 m ³ of volume of the aeration tank 18.

Furthermore, the culture medium of the SAB-1 strain pre-cultured in advance was charged into the aeration tank 18. The medium was a medium containing the SAB-1 strain at a concentration of 10 ¹⁰ cfu / mL. The medium was introduced into the aeration tank 18 such that the concentration of the SAB-1 strain was 10 ⁷ cfu / mL, and aeration treatment was performed. The drainage in the aeration tank 18 was controlled to have a pH of 6 or more and 7 or less. Then, a batch test for 48 hours was performed under the same conditions as in Example 1.

  Thereafter, the introduction of the drainage shown in Table 2 was started. At this time, while controlling the introduction amount of the drainage such that the ORP in the aeration tank 18 is +100 mV or more, the introduction amount of the drainage was gradually increased until the HRT becomes 1 hour. During this time, SAB-1 strain and calcium-derived inorganic substances were gradually attached to the fluid carrier to form a biofilm. In other words, immobilized bacteria in which the SAB-1 strain was immobilized on the surface of the fluid carrier were obtained. After the aeration treatment was started, the average COD of the treated water from day 1 to day 20 was 9 mg / L.

  After one week from the start of the aeration treatment, HRT was allowed to flow for 1 month and water was allowed to flow for 2 months, then the fluid carrier was recovered, and the amount of SS attached to the fluid carrier, the amount of organic components and the amount of inorganic components in SS were measured . The results are shown in Table 3 and FIG. In addition, when microorganisms were isolated from the biological membrane of a fluid carrier and 16S RNA analysis was performed, it was confirmed that the SAB-1 strain mainly exists.

Comparative Example 4
The aeration treatment was performed in the same manner as in Example 3 except that a fluid carrier made of polyester was used instead of the fluid carrier made of polyurethane. The fluid carrier was in the form of granules having a diameter of 8 mm. The fluid carrier was introduced into the aeration tank 18 so that the surface area was 600 m ² per 1 m ³ of volume of the aeration tank 18. After the aeration treatment was initiated, the average COD of treated water from day 1 to day 20 was 13 mg / L. Thereafter, in the same manner as in Example 3, the fluid carrier was recovered, and the amount of SS attached to the fluid carrier, the amount of organic components and the amount of inorganic components in the SS were measured. The results are shown in Table 3 and FIG.

Comparative Example 5
The aeration treatment was performed in the same manner as in Example 3 except that a fluid carrier made of polypropylene was used instead of the fluid carrier made of polyurethane. The fluid carrier was a cube of 10 mm × 10 mm × 10 mm. The fluid carrier was introduced into the aeration tank 18 so that the surface area was 600 m ² per 1 m ³ of volume of the aeration tank 18. After the aeration treatment was initiated, the average COD of treated water from day 1 to day 20 was 13 mg / L. Thereafter, in the same manner as in Example 3, the fluid carrier was recovered, and the amount of SS attached to the fluid carrier, the amount of organic components and the amount of inorganic components in the SS were measured. The results are shown in Table 3 and FIG.

Comparative Example 6
The aeration treatment was performed in the same manner as in Example 3 except that instead of the fluid carrier made of polyurethane, a fluid carrier made of polyethylene was used. The fluid carrier was a cube of 10 mm × 10 mm × 10 mm. The fluid carrier was introduced into the aeration tank 18 so that the surface area was 600 m ² per 1 m ³ of volume of the aeration tank 18. After the aeration treatment was started, the average COD of the treated water from day 1 to day 20 was 11 mg / L. Thereafter, in the same manner as in Example 3, the fluid carrier was recovered, and the amount of SS attached to the fluid carrier, the amount of organic components and the amount of inorganic components in the SS were measured. The results are shown in Table 3 and FIG.

  From the above results, it can be said that by using a fluid carrier made of polyurethane, waste water can be treated stably even when waste water containing calcium ions in high concentration is treated. In addition, the fluid carrier made of polyurethane has the smallest amount of SS derived from the inorganic component and the largest amount of SS derived from the organic component. In other words, because it was possible to fix a large amount of SAB-1 strain with little calcium deposition, it is considered that the waste water could be treated stably even when treated with waste water containing a high concentration of calcium ions. .

  On the other hand, the fluid carrier composed of a resin other than polyurethane has a large amount of SS derived from the inorganic component, and as a result, the amount of SS derived from the organic component is reduced. This is considered to be due to the inability to fix a large amount of SAB-1 strain due to high calcium deposition.

  The treatment method of the present invention can be used in treating waste water containing reducing sulfur compounds and calcium ions. In particular, the present invention can be suitably used particularly in a factory where the area of the site is narrow and a large scale sedimentation tank can not be installed.

1: Drainage tank, 2: Transport pump, 3: Neutralization tank, 4: Stirrer, 5: pH sensor, 6: Transport pump, 7: HCl tank, 8: Diffuser, 10: Transport pump, 11: HCl tank, 12: pH sensor, 13: feed pump, 14: NaOH tank, 15: ORP sensor, 16: DO sensor, 17: blower, 18: aeration tank, 22: water outlet.

  NITE P-1543

Claims (3)

A method for treating wastewater containing reducible sulfur compounds, comprising: discharging wastewater and sulfur oxidizing bacteria into an aeration tank and performing aeration treatment,
As the waste water, waste water containing reducing sulfur compounds and calcium ions is used,
As the sulfur-oxidizing bacteria, an immobilized bacterium in which the sulfur-oxidizing bacteria are immobilized is used as a polyurethane resin fluid carrier,
A method for treating wastewater, comprising allowing the immobilized bacteria to flow while maintaining the pH of the wastewater at 5 or more and 8 or less in the aeration tank, and performing aeration treatment in a fluid bed system. The treatment method according to claim 1, wherein the aeration treatment is performed while maintaining the aeration amount at 2 m ³ / m ³ · hr or more. The treatment method according to claim 1 or 2 , wherein the waste water has a concentration of reducible sulfur compound of 30 mg / L or more and a calcium ion concentration of 100 mg / L or more in COD conversion.

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