JP2622649B2 - Immobilized carrier suitable for sulfur oxidizing bacteria, method of immobilizing sulfur oxidizing bacteria on immobilized carrier, method of acclimating and growing sulfur oxidizing bacteria in fixed bed bioreactor, and biology of wastewater containing reducing sulfur compounds Processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention is directed to biological treatment of wastewater, and more particularly, to sulfur oxidizing bacteria that oxidize reducing sulfur compounds for biological treatment of wastewater containing reducing sulfur compounds. The present invention relates to a method for immobilizing a sulfur-oxidizing bacterium on an immobilized carrier, a method for acclimating and growing sulfur-oxidizing bacteria in a fixed-bed type bioreactor, and a method for biologically treating wastewater containing a reducing sulfur compound.

[0002]

2. Description of the Related Art Wastewater containing reducing sulfur compounds is generated from the photographic industry, petroleum refining industry, chemical industry, metal refining industry, mines, and the like. The reducing sulfur compounds contained in these wastewaters include sulfides (S ²⁻ ) and thiosulfate compounds (S ₂ O ₃
^2- ), polythionic acid compound (S ₃ O ₆ ^2- ), etc.
Wastewater containing these reducing sulfur compounds has a high COD (chemical oxygen demand) value due to the reducing sulfur compounds,
It cannot be discharged into public water bodies as it is.

[0003] As a method for treating this wastewater containing a reducing sulfur compound, a method is known in which a reducing sulfur compound is oxidized using an oxidizing agent such as sodium hypochlorite. There is a fatal drawback that the treatment water quality is not stable because it has not been established, and the treatment cost is high.

[0004] Instead of a chemical method having many of these problems, there is a method of removing COD by oxidizing a reducing sulfur compound by a microorganism, a so-called sulfur-oxidizing bacterium. For example, JP-A-56-67589,
This is the method described in JP-A-7-4296.

[0005] The method described in Japanese Patent Application Laid-Open No. 56-59589 discloses a method in which household wastewater containing S ₂ O ₃ ²⁻ , S ₃ O ₆ ²⁻ , S ₄ O ₈ ²⁻ or similar polythionic acid is added to household wastewater. CO2 of wastewater by adding one or more of wastewater from a septic tank for sewage treatment, aeration tank water from a sewage treatment plant, or metal mine drainage, and blowing oxygen to oxidize sulfur compounds into sulfuric acid
It is a method of removing.

[0006] The method described in Japanese Patent Application Laid-Open No. 57-4296 discloses a method for removing gypsum generated when removing COD in various wastewaters caused by thiosulfuric acid, polythionic acid, dithionic acid or similar sulfur oxides by sulfur oxidation. This is a method of removing COD in wastewater biologically by using a fluidized bed bioreactor, which is repeatedly used after adsorbing and concentrating bacteria grown and cultured on gypsum at the same time as a carrier material for bacteria and using the fluidized bed bioreactor.

[0007] There is also a problem in a method of biologically removing COD caused by sulfur oxides in wastewater using a fluidized bed bioreactor.

It is well known that there are many types of sulfur-oxidizing bacteria that decompose thiocyanate and thiosulfate in sewage or human waste sludge, metal mine wastewater, etc., as disclosed in JP-A-56-67589. The sulfur-oxidizing bacteria described in Japanese Patent Laid-Open Publication No. 57-4296 are thiosulfuric acid, polythionic acid, dithionic acid or the like at a pH as low as 1.9 to 2.0 as described therein. The sulfur oxides are oxidized to sulfuric acid to remove COD from the wastewater. Such a sulfur-oxidizing bacterium that lives or is active at a low pH is described in, for example, Kazumin Imai, “Autotrophic Bacteria” published by Kagaku Doujin at pages 63-67,
It is estimated to be a sulfur-oxidizing bacterium belonging to the genus Thiobacillus.

[0009] The use of such sulfur-oxidizing bacteria which live or are active at low pH for wastewater treatment has many problems. That is, when treating alkaline wastewater having a high pH, it is necessary to adjust the pH of the aeration tank in which low-pH live or active sulfur-oxidizing bacteria are present to a pH suitable for the sulfur-oxidizing bacteria. Has a pH of 1.9 to 2.
If it is low, such as 0, it is necessary to adjust the pH again in order to release this into public waters, and equipment for adjusting pH,
There is a problem that the cost of chemicals and the like is considerably high. In addition, when sulfur-oxidizing bacteria living or active at such a low pH are used for wastewater treatment, it is necessary to make the wastewater treatment equipment acid-resistant, which greatly increases the construction cost of the wastewater treatment equipment. Disadvantages.

[0010] The gypsum formed by the reaction of sulfuric acid and calcium produced by sulfur oxidizing bacteria oxidizing sulfur compounds is very fine, and there is a concern that the gypsum used for aeration in the aeration tank may be blocked. When the trachea is obstructed, the function of the sulfur oxidizing bacteria is reduced, and there is a problem that repairing the sulfur oxidizing bacteria requires much labor and cost.

Next, when treating wastewater containing sulfur compounds, the oxidation-reduction potential (OR
A method using P) is described in JP-A-58-122093. That is, in this method, a gas containing molecular oxygen or hydrogen peroxide is brought into contact with wastewater containing sulfide such as sodium sulfide and / or sodium hydrosulfide, and the sodium sulfide and / or sodium hydrosulfide in the wastewater is thiolated. When sodium sulfate is converted to sodium thiosulfate by contact with a gas containing molecular oxygen or hydrogen peroxide when the microorganism is treated with white sulfur bacteria, the ORP
Is -550 mV or more (reference electrode unknown), preferably -5
A gas containing molecular oxygen or hydrogen peroxide is supplied until the voltage becomes 00 mV (reference electrode unknown). However, this method does not aerate using ORP as an index at the stage of biological treatment.

[0012]

The conventional biological treatment method for wastewater containing sulfur compounds uses a low pH-resident or active sulfur-oxidizing bacterium, which complicates the treatment process, and the treatment equipment is also acid-resistant. However, there is a disadvantage that the running cost and the equipment cost of the process are increased because of the performance specifications. Also,
Since the index of the amount of aeration in the biological treatment process is not clear, if the amount of aeration is insufficient, the oxidation of the reducing sulfur compound is insufficient, and the unreacted reducing sulfur compound flows into the treated water and the treated water is discharged. There is a concern about increasing COD. Conversely, if the amount of aeration is excessive, the flocs of the sulfur oxidizing bacteria in the aeration tank are mechanically destroyed, which causes the sulfur oxidizing bacteria to flow into the treated water, lowering the concentration of the sulfur oxidizing bacteria in the aeration tank and reducing the quality of the treated water. There is a problem that causes deterioration. Further, when gypsum produced by sulfur-oxidizing bacteria is used as a carrier for immobilizing sulfur-oxidizing bacteria, the particles are too fine, which causes obstruction of the air diffuser.

[0013]

Gist of the present invention SUMMARY OF THE INVENTION are following through <br/> Ride.

[0014] (1) In the immobilization of sulfur-oxidizing bacteria for waste water containing a reducing sulfur compound is treated with a fixed bed bioreactor using sulfur-oxidizing bacteria, Gao
A calcium compound is blended with phosphorus-based clay, and after molding, firing
An immobilized carrier suitable for sulfur-oxidizing bacteria, characterized by using ceramics obtained by the synthesis.

(2) Further, granulated blast furnace slag was blended .
An immobilized carrier suitable for the sulfur-oxidizing bacteria of the above (1) .

( 3 ) The fixed carrier of the above (1) or (2) is filled in a fixed-bed type bioreactor, and an activated sludge mixed solution collected from an aeration tank for sewage activated sludge treatment is put into the bioreactor. After the activated sludge is immobilized on the immobilization carrier, the pH and ORP of the fixed-bed type bioreactor are maintained under predetermined conditions to acclimate and grow the sulfur-oxidizing bacteria, and immobilize the sulfur-oxidizing bacteria on the immobilization carrier. .

( 4 ) In the method of the above ( 3 ), the pH of the fixed bed type bioreactor is controlled and controlled within a range of 4.0 to 7.5, and the aeration of the fixed bed type bioreactor is fixed. A method of acclimating and growing sulfur-oxidizing bacteria in a fixed-bed type bioreactor, wherein the process is performed using the ORP of the treated water at the outlet of the bioreactor as an index.

( 5 ) In the method of the above ( 4 ), the OR
A fixed-bed type biomass characterized in that P is controlled and controlled to an ORP calculated from the amount of change in free reaction energy relating to a reaction in which a reducing sulfur compound contained in wastewater is chemically oxidized to sulfuric acid. A method of acclimating and growing sulfur-oxidizing bacteria in a reactor.

( 6 ) The wastewater containing a reducing sulfur compound is
(1) or (2) of method (3) immobilized carrier or the (4) or (5) treatment in a fixed bed bioreactor with immobilized acclimatization and proliferation and sulfur-oxidizing bacteria according to the method of, A biological treatment method for wastewater containing a reducing sulfur compound.

( 7 ) In the method of the above ( 6 ), the pH of the fixed bed type bioreactor is controlled to a predetermined value, and the amount of aeration supplied to the fixed bed type bioreactor is treated at the outlet of the fixed bed type bioreactor. A biological treatment method for wastewater containing a reducing sulfur compound, wherein the wastewater treatment includes management and control using the ORP of water as an index.

( 8 ) In the method of the above ( 6 ) or ( 7 ), the reducing sulfur compound is hydrogen sulfide and / or a thiosulfate compound, and the pH of the fixed-bed type bioreactor is in the range of 4.0 to 7.5. Biological treatment of wastewater containing reducing sulfur compounds, wherein the ORP of the treated water at the outlet of the fixed-bed type bioreactor is controlled and controlled in the range of +100 to +200 mV (based on silver / silver chloride electrode), respectively. Method.

[0022]

According to the present invention, in the treatment of wastewater containing a reducing sulfur compound, sulfur-oxidizing bacteria that oxidize the reducing sulfur compound acclimate and proliferate from the activated sludge of the sewage. As a carrier for immobilizing the reactor
Blended calcium compound to Olin Group clay, after molding,
Using the ceramics obtained by calcination, the pH and ORP of the fixed-bed type bioreactor are controlled and controlled within a predetermined range in the adaptation and propagation of sulfur-oxidizing bacteria and in wastewater treatment. To explain .

First, the advantage of acclimating and growing sulfur-oxidizing bacteria that oxidize the most active reducing sulfur compounds in the pH range of 4.0 to 7.5 from activated sludge for treating sewage and industrial wastewater,
The method will be described.

The present inventors have found that activated sludge which is treating sewage and industrial wastewater inhabits sulfur-oxidizing bacteria which oxidize reductive sulfur compounds at pH 4.0 to 7.5. . If active sulfur oxidizing bacteria exist around such neutrality, the conventional problems, namely, pH adjustment of wastewater containing reducing sulfur compounds and treated water treated with sulfur oxidizing bacteria, or of wastewater treatment equipment No need for acid-resistant specifications
Equipment costs and processing costs can be significantly reduced.

[0025] As a result of research on the acclimatization and proliferation method of sulfur-oxidizing bacteria in the vicinity neutral, filled with immobilization carrier below the fixed bed bioreactor 8 shown in FIG. 1,
Activated sludge mixture which is treating sewage is put in this,
The pH of the fixed-bed type bioreactor is adjusted to 4.0 to 7.5.
If the wastewater containing the reducing sulfur compound is supplied while controlling and controlling the aeration of the fixed bed type bioreactor using the ORP obtained by the method described below as an index,
It was found that active sulfur-oxidizing bacteria easily acclimated and proliferated in the range of 4.0 to 7.5.

The ORP assumes a reaction in which a reducing sulfur compound is chemically oxidized to a sulfuric acid compound. The amount of change in free energy in this reaction is obtained from a handbook, a textbook, a literature, and the like. The ORP for causing these reactions may be obtained and set by calculation from the amount of change. Specifically, the thiosulfate compound is about + 140-
160 mV (based on silver / silver chloride electrode), sulfide is about -60
In the case of -80 mV (based on the silver / silver chloride electrode) and the two are mixed, it may be controlled and controlled to the oxidation side, that is, to about +140 to 160 mV.

In this manner, the sulfur-oxidizing bacteria are acclimated and grown from the activated sludge of the sewage, and the activated sludge of the sulfur-oxidizing bacteria is inoculated into a liquid Starkey medium having a different pH, and is then shaken using a shaking incubator. At ℃, the thiosulfate ion concentration of the Starkey medium is from 2200 mg / l to 50 mg.
/ L or less was measured. The result is shown in FIG. The composition of the liquid Starkey medium is shown in Table 1.

[0028]

[Table 1]

The above reagent was dissolved in 1 liter of a buffer solution of each pH to prepare a Starkey liquid medium having a different pH.

From the results shown in FIG. 2, the p
When H is in the range of 2 to 3.5 and 8.0 to 10, thiosulfate ion hardly decreases even when shaken for 20 days or more, but when pH is in the range of 4.0 to 7.5, the number of shaking days is 12 days or less. In particular, it was found that the thiosulfate ion became 50 mg / l or less in 5 days or less especially at pH 5.0 to 6.5. Therefore, it is clear that the sulfur-oxidizing bacteria acclimated and grown from the activated sludge of the sewage by the method of the present invention are active in the pH range of 4.0 to 7.5 and have the ability to oxidize reducing sulfur compounds. Became.

On the other hand, conventional methods for biologically treating wastewater containing reducing sulfur compounds using sulfur-oxidizing bacteria, for example, JP-A-53-59254 and JP-A-56-67.
The sulfur oxidizing bacteria used in the method described in JP-A-589
Although the reducing sulfur compound is oxidized at 1.9 to 2.0, the sulfur-oxidizing bacteria acclimated and cultured by the method of the present invention have no ability to oxidize the reducing sulfur compound at such a low pH. From this, it is clear that the sulfur oxidizing bacteria acclimated and cultured by the method of the present invention are different from the sulfur oxidizing bacteria used in the conventional wastewater treatment.

This is described in D. P. Kelly and
A. P. It is also evident by the Harrison classification. That is, according to their classification shown in FIG. 3, the sulfur oxidizing bacteria active in the range of pH 4.0 to 7.5 acclimated and grown by the method of the present invention belong to Group 2, and Japanese Patent Application Laid-Open No. 53-5 / 1983.
9254 and JP-A-56-67589 are active at pH 1.9 to 2.0.
It is clear that the group belongs to up5 (Title: Berg
eye's Manual of Systematic
Bacteriology Vol. 3, Author: Ja
mes T. Staley, Publisher: Williams
& Wilkins, description: Fi on page 1843
g. 20.47).

Next, an immobilized carrier suitable for sulfur-oxidizing bacteria used in a fixed-bed type bioreactor will be described.

From activated sludge of sewage and industrial wastewater, pH 4.0
There are many filamentous bacteria among the sulfur-oxidizing bacteria that have been adapted and grown under neutral or weakly acidic conditions up to 7.0, and wastewater containing reducing sulfur compounds was treated by a fluidized-bed bioreactor using the sulfur-oxidizing bacteria. In this case, bulking is likely to occur, and sludge of sulfur-oxidizing bacteria flows out into the treated water, resulting in deterioration of the treated water quality. In addition, the sulfur-oxidizing bacteria in the bioreactor cannot be maintained at a high concentration, so that high-efficiency treatment is difficult. Further, when the same treatment is performed in a fixed-bed type bioreactor, it is difficult to immobilize sulfur oxidizing bacteria when resin, ordinary ceramics, etc. are used as an immobilization carrier, and the same as in the case of the fluidized-bed type bioreactor described above. Similarly, the outflow of sulfur-oxidizing bacteria occurs, resulting in deterioration of treated water quality, and it is difficult to perform highly efficient treatment.

The present inventors have studied immobilized carriers suitable for sulfur-oxidizing bacteria used in a fixed-bed type bioreactor. As a result, it has been found that the aforementioned problems can be solved by using an immobilized carrier described below .

[0036] Reducing sulfur compounds, such as sulfides, thiosulfate compounds, and thiocyanate compounds, contained in wastewater are oxidized to sulfuric acid when subjected to aerobic biological treatment by sulfur-oxidizing bacteria. This sulfuric acid forms calcium sulfate, or gypsum, when calcium compounds are present. A method of using the gypsum produced by the sulfur-oxidizing bacteria as a carrier for immobilizing the sulfur-oxidizing bacteria in a fluidized bed bioreactor is the method described in the above-mentioned Japanese Patent Application Laid-Open No. 57-4296. This method is not preferable to be applied to a fluidized bed type bioreactor because it may cause clogging.

The present inventors have found that by forming on the surface of the immobilization carrier of the fixed bed type bioreactor gypsum order to solve such a problem, consider a method for immobilizing sulfur oxidizing bacteria to, sulfur An immobilized carrier suitable for oxidizing bacteria was invented.

The immobilized carrier suitable for the sulfur-oxidizing bacteria used in the fixed-bed type bioreactor of the present invention is a kaolin-based viscosifier.
A calcium compound is added to the soil, molded and fired.
The Rukoto using the ceramic, a sulfur oxidizing bacteria reacts with calcium compounds formulated with sulfuric acid produced by oxidizing a reducing sulfur compound, to form particles of fine gypsum on the surface of the immobilizing carrier. Sulfur-oxidizing bacteria adhere to the gypsum and are immobilized, and the outflow of sulfur-oxidizing bacteria from the bioreactor to the treated water is suppressed. As a result, the sulfur-oxidizing bacteria in the bioreactor can be maintained at a high concentration, and reducing sulfur compounds The wastewater containing wastewater can be treated with high efficiency, and the quality of treated water can be improved.

The carrier for immobilizing such sulfur-oxidizing bacteria is as follows:
If calcium is excessively added, calcium is eluted from the immobilization carrier in a large amount. As a result, gypsum on which the sulfur-oxidizing bacteria are immobilized floats in the bioreactor, causing airflow tube obstruction. In addition, when a large amount of calcium is eluted from the immobilized carrier, there is a problem that the strength of the immobilized carrier is insufficient. On the other hand, if the amount of calcium in the immobilization carrier is insufficient, the amount of gypsum formed on the surface of the immobilization carrier is not sufficient, so that the sulfur-oxidizing bacteria are not sufficiently immobilized.
Outflow of sulfur oxidizing bacteria to the treated water is likely to occur, and as a result, the sulfur oxidizing bacteria in the bioreactor cannot be maintained at a high concentration, making it difficult to treat wastewater containing reducing sulfur compounds with high efficiency. There is a problem that decreases.

Therefore, the present inventors have developed an immobilization carrier which has excellent immobilization performance for sulfur-oxidizing bacteria, has sufficient strength as an immobilization carrier for a fixed-bed type bioreactor, and does not cause clogging of a diffuser tube. As a result of research, the immobilized carrier of the present invention has been reached.

As a result of forming an appropriate amount of gypsum on the surface of the immobilized carrier and examining the composition of the immobilized carrier having sufficient strength as the immobilized carrier of the fixed bed type bioreactor, CaO—Al ₂ O ₃ —SiO ₂ is good, SiO ₂ ,
Al ₂ O ₃ retains strength.

After molding a mixture of CaO—Al ₂ O ₃ —SiO ₂ and firing at 900 to 1500 ° C.,
listolite, tridymite, Pse
udowolastonite, Anorthit
e, Gehlenite, Corundum and Li
It is known to form me. Among these, the calcined product suitable for the immobilization carrier for sulfur oxidizing bacteria is Anor
thite (CaO.Al ₂ O ₃ .2SiO ₂ ) and Gehlenite (2CaO.Al ₂ O ₃ .SiO
₂ ) It became clear that CaO of this composition with a composition ratio of 1 to 10% excess and calcined at 900 to 1250 ° C. was optimal. The specific mixing ratio of the immobilized carrier is
CaO is 14~40%, Al ₂ O ₃ is 15-25%, S
iO ₂ from 5 to 20 percent is appropriate.

The raw materials used for the immobilized carrier of the present invention include:
Kaolin group clay minerals for Al ₂ O ₃ -SiO ₂
For CaO—Al ₂ O ₃ —SiO ₂ , granulated blast furnace slag or the like is appropriate, and a calcium compound such as calcium hydroxide may be added to the slag to obtain the above-mentioned composition. The shape of the immobilized carrier is preferably a shape having excellent chemical engineering properties, such as a saddle type, a ring type, a cylindrical type, and a ball type.

Next, the point of performing aeration using the ORP at the outlet of the fixed bed type bioreactor as an index in the present invention will be described.

When the sulfur-oxidizing bacteria immobilized on the immobilization carrier of the present invention oxidize a reducing sulfur compound to sulfuric acid, oxygen is required. That is, the cells grow by immobilizing the carbon dioxide in the aeration air using the oxidation energy when the sulfur-oxidizing bacteria oxidize the reducing sulfur compounds. Therefore, if the amount of aeration is insufficient, the ORP required to oxidize the reducing sulfur compound will not be reached, and the oxidation of the reducing sulfur compound will not be sufficiently performed, so that the concentration of the reducing sulfur compound in the treated water will increase, Further, since the oxidizing energy is not supplied sufficiently, the growth of the sulfur-oxidizing bacteria is not sufficiently performed. On the other hand, when excessive aeration is performed, the sulfur-oxidizing bacteria immobilized on the immobilization carrier are peeled off and flow out into the treated water, causing deterioration of the treated water.

To solve the problem of aeration, the oxidation reaction of reducing sulfur compounds by sulfur-oxidizing bacteria is assumed to be the same as the chemical reaction, and the amount of free reaction energy change at the time of this chemical reaction is determined. The reduction potential was calculated, and the amount of aeration was controlled and controlled using the oxidation-reduction potential as an index.

In the case of a fixed-bed type bioreactor, it is difficult to measure the oxidation-reduction potential inside the bioreactor. Therefore, the aeration amount is controlled and controlled by the ORP of the treated water at the outlet of the bioreactor. went. As a result, the reducing sulfur compounds are completely oxidized and are not detected in the treated water, and the acclimation and growth of sulfur-oxidizing bacteria are sufficiently performed.
In addition, peeling of the sulfur-oxidizing bacteria from the immobilized carrier hardly occurred.

However, when the number of sulfur-oxidizing bacteria in the bioreactor increases due to the growth of sulfur-oxidizing bacteria, the bacteria are separated from the immobilized carrier and flow out into the treated water, causing deterioration of the treated water quality. The exfoliated sulfur-oxidizing bacteria can be removed by sand filtration or the like, but the sand tends to be clogged, and it is necessary to frequently wash the back. If a filtration device filled with saddle-type ceramics is used as a filtration method instead of sand filtration, a good treated water quality with a suspended substance (SS) of 5 mg / l or less can be obtained. The amount is ^{3 to} 7 kg per 1 m ³ of the saddle-type ceramics, so that the filter is hardly clogged, so that the frequency of backwashing can be significantly reduced.

The continuous treatment of wastewater containing a reducing sulfur compound according to the method of the present invention will be described from the stage of acclimation and growth of sulfur-oxidizing bacteria.

[0050] This in ORP controller and pH controller fixed bed bioreactor 8 aerobic having a shown in FIG. 1
The immobilized carrier of the invention is filled. This bioreactor 8
Activated sludge mixed liquid collected from the aeration tank of the activated sludge treatment equipment that treats sewage or industrial wastewater is put into the reactor, and the ORP value of the bioreactor 8 is assumed to be the oxidation reaction of the reducing sulfur compound contained in the wastewater assuming the reduction reaction. ORP value calculated from the amount of change in free energy of, for example, about +140 to 160 mV (Ag when the reducing sulfur compound is a thiosulfate compound)
/ AgCl electrode standard), and wastewater containing a reducing sulfur compound such as a thiosulfate compound or a sulfide as a reducing sulfur compound is supplied to the bioreactor 8 such that the treatment time is 8 hours. Although the ORP does not rise to the set value at the beginning of the supply of the wastewater, it gradually rises and reaches the set value in about 10 to 15 days, and the ORP control is performed. The reducing sulfur compound in the treated water is hardly detected when the ORP is about +100 mV, and the COD of the treated water is significantly reduced. When the ORP reaches the set value, reduce the wastewater supply to 7
Processing time every 6 to 10 days → 6 hours → 3 hours → 3 hours → 2
Increase gradually as time goes on.

At this time, as the acclimatization and growth of the sulfur-oxidizing bacteria progress, the oxidation of the reducing sulfur compound proceeds to generate sulfuric acid, so that the pH of the aeration tank decreases. As described in JP-A-57-4296, the pH decreases to 1.9 to 2.0. Sulfur-oxidizing bacteria acclimated and grown in a state where the pH is lowered as described above are strongly acidic and active Thiobacill.
The genus us becomes the priority species, and the problems described above occur. For this reason, the pH of the bioreactor is 4.0 to 4.0.
It is necessary to control and control with an alkaline agent so as to be in the range of 7.5. By controlling and controlling the pH of the aeration tank in this way, sulfur-oxidizing bacteria that oxidize active reducing sulfur compounds in the pH range of 4.0 to 7.5 can be acclimated and propagated, as described above. It is possible to solve the problems of the sulfur-oxidizing bacteria belonging to the genus Thiobacillus.

In this wastewater treatment, when the ORP at the outlet of the bioreactor 8 falls below a set value, the ORP sensor 13 (gold-silver / silver chloride composite electrode) catches the aeration of the bioreactor 8 and the ORP controller 14 The rotation rate of the roots blower 15 is increased to increase the amount of aeration. When the set value is restored, control is performed by a proportional control method in which the rotation number of the roots blower 15 is reduced to reduce the amount of aeration. Also,
The pH of the bioreactor 8 is measured by a pH sensor 16
The control unit 17 controls and controls with an alkali agent and an acid so that the pH is in the range of 4.0 to 7.5.

Since the gypsum on which the sulfur-oxidizing bacteria are immobilized is separated from the immobilization carrier and slightly flows out from the bioreactor 8, if the gypsum flows directly into the treated water, the quality of the treated water deteriorates. In order to remove the gypsum, a ceramic filtration device 11 filled with saddle-type ceramics or the like is installed after the bioreactor to remove the gypsum, whereby good treated water can be obtained.

[0054]

EXAMPLE Next, the method of the present invention was carried out at a high concentration of reducing sulfur compounds such as thiosulfate compounds and sulfides generated from a slag aging yard of an ironworks, and when the pH was 12 or less.
~ 14 and highly alkaline, COD 300 ~ 600mg
/ L high wastewater (blast furnace slag wastewater) treatment, pH of 12-14 used for corrosion test of steel pipe, high alkalinity, CO2
An example in which D is applied to the treatment of wastewater containing hydrogen sulfide as high as 300 to 600 mg / l and drain water of blast furnace gas containing a thiocyanate compound will be described. In addition, the following
In Examples, kaolin-based clay was used as an immobilization carrier.
However, the addition of granulated blast furnace slag to this also has the same effect.
Efficient wastewater treatment was possible.

[0055]

Example 1 38 parts by weight of calcium hydroxide was mixed with 100 parts by weight of kaolin clay in an ORP control fixed bed type bioreactor 8 of FIG. 1 and the mixture was molded into a 1-inch saddle mold. Then, the immobilized carrier obtained by calcination was filled, and a bioreactor 8 was charged with an activated sludge mixed solution having a treated sewage concentration of 1500 to 2000 mg / l, and immobilized. The ORP of the treated water at the outlet of the bioreactor 8 was set to about +150 mV (based on the Ag / AgCl electrode), and aeration was performed from the bottom of the bioreactor 8. While controlling the pH to 6.0 to 6.5, blast furnace slag wastewater whose properties are shown in Table 2 was supplied such that the residence time in the bioreactor 8 was 8 hours.

[0056]

[Table 2] Example of blast furnace slag wastewater and treated water quality (Water quality: mg / l except pH) (Note) ND: Not detected

After supplying the blast furnace slag wastewater, about 7 to 10
After a day, no thiosulfate compound or sulfide was detected in the treated water, and the COD was reduced to about 50 mg / l. Next, if the treatment time is reduced from 6 hours → 4 hours → 3 hours → 2 hours every 7 to 10 days, no reducing sulfur compounds such as thiosulfate compounds and sulfides are detected in the treated water,
D was removed to 10 mg / l or less, and the adaptation of sulfur-oxidizing bacteria from activated sludge of sewage was completed. When the acclimation of the sulfur-oxidizing bacteria was completed, the blast furnace slag wastewater was supplied so that the treatment time became 2 to 3 hours, and the blast furnace slag wastewater could be continuously treated.

The 10% sulfuric acid used for controlling the pH of the aeration tank is as follows:
As the acclimation of the sulfur-oxidizing bacteria progresses, the consumption decreases, and the acclimation of the sulfur-oxidizing bacteria is completed, and the consumption is hardly consumed in the stage of the continuous treatment in which the treatment time is 2 to 3 hours. this is,
This is because reducing sulfur compounds such as thiosulfate compounds and sulfides are oxidized to sulfuric acid, and the sulfuric acid can maintain the pH of the aeration tank at an appropriate value without adding an acid from the outside.

Examples of the water quality of the treated blast furnace slag wastewater, the processing time during the acclimatization period of the sulfur-oxidizing bacteria, and the example of the treated water quality when the continuous processing is performed for a subsequent processing time of 2 to 3 hours are also described. The results are shown in Table 2. As a result, reducing sulfur compounds such as thiosulfate compounds and sulfides were not detected from the treated water of the continuous treatment, and the COD was 10 mg / l or less and the pH was 6.0 to 6.5. Can be released.

According to the method of the present invention, acclimation of sulfur-oxidizing bacteria was completed in 7 to 10 days by using blast-furnace slag wastewater from activated sludge that is undergoing sewage treatment. That is, it is considered that the habituation of the sulfur-oxidizing bacteria was completed when the reducing sulfur compounds such as thiosulfate compounds and sulfides were not detected in the treated water, and thereafter, the treatment load of the reducing sulfur compounds was increased. That is, the processing time is changed every 6 to 10 days from 6 hours to 4 hours.
The growth of sulfur oxidizing bacteria was measured by successively shortening to 3 hours. No reducing sulfur compounds were detected in the treated water even during the growth period of the sulfur-oxidizing bacteria, and the COD was as good as 10 mg / l or less. After the completion of the growth of the sulfur-oxidizing bacteria, even if the blast furnace slag wastewater is treated with high efficiency for a treatment time of 2 to 3 hours, no reducing sulfur compound is detected in the treated water, and the COD of the treated water is 10%.
mg / l or less was good.

[0061]

Example 2 The pH used in the corrosion test of steel pipe was 12-14.
And highly alkaline, with a COD of 600-1200 mg /
1, wastewater containing 300 to 600 mg / l hydrogen sulfide was treated.

First, sulfur-oxidizing bacteria that oxidize hydrogen sulfide were acclimated and grown by the method of Example 1. The blast furnace slag wastewater of Example 1 was used for the stage of acclimation and propagation of the sulfur-oxidizing bacteria. When the blast furnace slag wastewater could be treated in 2 to 3 hours, the corrosion test wastewater adjusted to pH 8 to 9 was supplied to the bioreactor so that the treatment time was 8 hours. When the COD of the treated water becomes 10 to 20 mg / l or less, 7
Every 10 to 10 days, the treatment time was gradually reduced from 6 hours to 4 hours to 3 hours, and the sulfur-oxidizing bacteria were adapted to the corrosion test wastewater. When the acclimation of the sulfur oxidizing bacteria to the corrosive waste liquid is completed, the treatment time
When continuous treatment is performed for 3 hours, hydrogen sulfide is not detected in the treated water, and the pH is 6.0 to 6.5 and the COD is 10 mg.
/ L, treated water with SS of 5 mg / l or less was obtained.

In the treatment of the corrosion test waste liquid, the pH of the bioreactor was adjusted to 6.0 to 6.5, and the aeration of the bioreactor was carried out when the ORP of the biological treatment water at the outlet of the bioreactor was 100 to 150 mV (silver). / Silver chloride electrode reference) from the bottom of the bioreactor.

When the acclimatization and propagation of sulfur oxidizing bacteria from activated sludge of sewage are directly performed in the wastewater from the corrosion test, the sulfur oxidizing bacteria are not sufficiently grown, and the exhaust gas containing high concentration hydrogen sulfide is discharged from the bioreactor. , Which is not preferable because it deteriorates the surrounding environment. Therefore, it is better to use blast furnace slag wastewater for acclimation and propagation of sulfur oxidizing bacteria. In addition, hydrogen sulfide may leak from the pH adjustment tank that adjusts the corrosion test wastewater to pH 8 to 9 in front of the bioreactor, so the suction port of the aeration blower of the bioreactor is connected to the pH adjustment tank, When air containing hydrogen is used for aeration of the bioreactor, leakage of hydrogen sulfide from the pH adjustment tank can be prevented.

The treatment of the waste liquid containing hydrogen sulfide according to the method of the present invention is excellent in treated water quality because the treatment is more stable than the chemical treatment, and the running cost can be greatly reduced. it can.

[0066]

Embodiment 3 Drain water of a blast furnace gas contains 10 to 500 mg / l of a thiocyan compound, and since the COD caused by the thiocyan compound is high, it is necessary to treat the thiocyan compound. Then, as a result of treating this drain water with a bioreactor of sulfur oxidizing bacteria acclimated and grown by the method of Example 1, the thiocyan compound was reduced to 1 mg / l or less and COD in a treatment time of 2 to 3 hours. Is 15m
g / l or less.

[0067]

According to the present invention, a reducing sulfur compound having a pH of 4.0 to 4.0 can be obtained from activated sludge which is treating sewage and industrial wastewater.
The acclimation and growth of sulfur-oxidizing bacteria that oxidize around 7.5 are remarkably promoted, and the acclimation and growth of the sulfur-oxidizing bacteria can be performed in a short period of time. In addition, the use of sulfur-oxidizing bacteria facilitates the treatment of wastewater containing a reducing sulfur compound, thereby reducing treatment equipment and treatment costs.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an ORP-controlled fixed-bed bioreactor used for treating wastewater containing a reducing sulfur compound using sulfur-oxidizing bacteria.

FIG. 2 is a graph showing the relationship between thiosulfate ion oxidation rate (activity) and pH of sulfur-oxidizing bacteria acclimated by the method of the present invention.

FIG. 3 is a diagram showing classification of sulfur-oxidizing bacteria.

[Explanation of symbols]

 Reference Signs List 1 wastewater tank 2 wastewater supply pump 3 pH adjustment tank 4 pH sensor 5 pH controller 6 acid supply pump 7 alkali supply pump 8 fixed-bed type bioreactor 9 diffuser 10 ORP measurement tank 11 ceramics filtration device 12 treated water 13 ORP sensor 14 ORP controller 15 Roots blower 16 pH sensor 17 pH controller 18 Alkaline supply pump

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-4296 (JP, A) JP-A-62-106822 (JP, A) JP-A-63-236596 (JP, A) JP-A-4- 16297 (JP, A) (54) [Title of the Invention] Immobilized carrier suitable for sulfur oxidizing bacteria, method for immobilizing sulfur oxidizing bacteria on immobilized carrier, acclimation of sulfur oxidizing bacteria to fixed bed type bioreactor Propagation method and biological treatment method for wastewater containing reducing sulfur compounds

Claims (8)

(57) [Claims] 1. A fixed carrier for sulfur-oxidizing bacteria for treating wastewater containing a reducing sulfur compound by a fixed-bed type bioreactor using sulfur-oxidizing bacteria, comprising a kaolin family.
Blend the calcium compound into the clay, fire after molding
An immobilized carrier suitable for sulfur-oxidizing bacteria, characterized by using the obtained ceramics . 2. A method according to claim, further formulated with water-granulated blast furnace slag
An immobilized carrier suitable for the sulfur-oxidizing bacteria according to 1 . 3. The immobilized carrier according to claim 1 or 2 is filled in a fixed-bed type bioreactor, and an activated sludge mixed solution collected from an aeration tank for sewage activated sludge treatment is added thereto. A method in which, after immobilization on an immobilization carrier, the pH and ORP of the fixed-bed type bioreactor are maintained under predetermined conditions to acclimate and grow the sulfur-oxidizing bacteria, and immobilize the sulfur-oxidizing bacteria on the immobilization carrier. 4. The method according to claim 3 , wherein the pH of the fixed-bed type bioreactor is controlled and controlled in a range of 4.0 to 7.5, and the aeration of the fixed-bed type bioreactor is controlled by a fixed-bed type bioreactor. A method for acclimating and growing sulfur-oxidizing bacteria in a fixed-bed type bioreactor, wherein the process is performed using the ORP of the treated water at the outlet of the reactor as an index. 5. The method of claim 4 , wherein the ORP
A fixed-bed type bioreactor, wherein the ORP calculated and calculated from the amount of change in free reaction energy relating to the reaction in which the reducing sulfur compound contained in the wastewater is chemically oxidized to sulfuric acid is controlled and controlled. A method of acclimating and growing sulfur-oxidizing bacteria. 6. A method according to claim 3 , wherein the wastewater containing a reducing sulfur compound is applied to the immobilization carrier according to claim 1 or 2 , and the sulfur-oxidizing bacteria acclimated and grown by the method according to claim 4 or 5. A biological treatment method for wastewater containing a reducing sulfur compound, which is treated in an immobilized fixed-bed bioreactor. 7. The method according to claim 6 , wherein the pH of the fixed-bed bioreactor is controlled to a predetermined value, and the amount of aeration supplied to the fixed-bed bioreactor is treated water at the outlet of the fixed-bed bioreactor. A biological treatment method for wastewater containing a reducible sulfur compound, wherein the wastewater treatment includes control and control using the ORP as an index. 8. The method of claim 6 or 7, wherein,
The reducing sulfur compound is a hydrogen sulfide and / or thiosulfate compound, and the pH of the fixed-bed type bioreactor is adjusted to 4.0 to 4.0.
Wastewater containing a reducing sulfur compound, wherein the ORP of the treated water at the outlet of the fixed-bed type bioreactor is controlled and controlled within a range of 7.5 to +100 to +200 mV (based on a silver / silver chloride electrode), respectively. Biological treatment method.