JP2000051884A - Method and apparatus for biological treatment of organic waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve water quality by reducing a hardly decomposable substance contained in treated water in an org. waste water treatment method. SOLUTION: In org. waste water treatment method including a biological treatment process (1) for biologically treating waste water, a solid-liquid separation process (2) separating a mixed soln. after biological treatment into treated water and sludge and a process (3) for solubilizing sludge, a hardly decomposable substance treatment process (4) for decomposing a hardly decomposable substance hard to receive the decomposition in the biological treatment process is further included.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for treating sludge sufficiently in a sewage treatment process such as a sewage treatment plant, a human waste treatment plant, or a method for treating organic wastewater discharged from a food factory, a chemical factory, and the like. The present invention relates to a processing method and a processing apparatus for biological digestion and solubilization, and for further improving the quality of treated water.

[0002]

2. Description of the Related Art The above-mentioned method for treating organic wastewater involves excess sludge consisting of microbial biomass mainly composed of microbial cells and untreated residual solid matter, which is produced by biological digestion of organic wastewater. Activated sludge treatment methods in which treated sludge is separated into solid and liquid in a sedimentation tank or the like and then treated water obtained as a supernatant is appropriately discharged, while excess sludge is treated by ocean dumping or land reclamation have been widely adopted. .

[0003] The present applicant has reported an activated sludge treatment method and an apparatus therefor as an invention capable of reducing the amount of excess sludge generated by such a wastewater treatment method (Japanese Patent Application Laid-Open No. Hei 9 (1994)).
-10791). FIG. 4 shows a schematic flow of this method. Here, the organic wastewater is subjected to a treatment in an aeration treatment tank 11 and then separated into treated water A and sludge in a settling tank 12. Part of the sludge is returned to the aeration treatment tank 11 via the circulation path, and the excess sludge as the remaining sludge is solubilized by the thermophilic bacterium in the solubilization treatment tank 13, and the solubilized treatment liquid B is returned via the return path. It is returned to the aeration tank 11. By passing through the solubilization process in this way, the volume of excess sludge is reduced.

[0004]

However, according to the sludge treatment method disclosed in the above-mentioned publication, components which cause deterioration of the treated water quality are released from the sludge during treatment in the solubilization treatment tank 13 to obtain a sludge treatment. In some cases, a large amount of components related to the processing solution to be obtained are contained. In this component, the solubilized solution is returned to the aeration tank 11 by the wastewater treatment method in the circulation system as described above, and even if it is subjected to the decomposition treatment, a hardly decomposable substance which is extremely difficult to be decomposed by the aeration treatment. May remain.
The composition and content of this hardly decomposable substance differ depending on the type of raw wastewater to be treated. For example, a large amount of hardly decomposable organic wastewater (pulp effluent) derived from the treatment process of paper mill wastewater Substances are often produced, resulting in deterioration of treated water quality. In the case of wastewater from paper mills, it is possible that insoluble substances may be generated due to fibrous lignin derivatives and partial degradation products derived from plant cells. It is not clear.

The present invention has been made in the prior art in view of such a problem that the quality of treated water may be deteriorated, and an object of the present invention is to provide an organic wastewater containing a step of solubilizing sludge. In the activated sludge treatment method, decomposable substances are decomposed with good efficiency to improve the quality of treated wastewater,
An object of the present invention is to provide a processing method in which the possibility of causing environmental pollution is reduced.

[0006]

The present invention has been accomplished to achieve the above-mentioned object, and the gist thereof is as follows.

The first invention of the present application relates to (1) a biological treatment step in which wastewater is biologically treated, (2) a solid-liquid separation step in which a mixed liquid after biological treatment is separated into treated water and sludge, and (3)
An organic wastewater treatment method including a solubilization step in which sludge is solubilized, further comprising a hardly decomposable substance treatment step (4) for decomposing a hardly decomposable substance that is not easily decomposed in the biological treatment step (1). It is characterized by including. By providing the hardly decomposable substance treatment step (4), the amount of hardly decomposable substances that had to be disposed of in the state of being undecomposed and mixed in the treated wastewater has been reduced, and the quality of the treated water has been reduced. Can be improved.

[0008] The second invention of the present application relates to the treatment method of the first invention, wherein the treatment solution after the solubilization step (3) is again subjected to the biological treatment step (1), and the treatment is performed by a circulation system. . According to this method, biological digestion of the treatment liquid, solubilization of the sludge, and treatment of the hardly decomposable substance can be continuously performed, so that the volume of the excess sludge is reduced and the quality of the treated water is more reliably improved.

The third invention of the present application is the treatment method according to the first or second invention, wherein the step (4) of treating the hardly decomposable substance is performed on the treatment solution obtained in the solubilization step (3). It is characterized by. Since the hardly decomposable substance is released from the sludge by the treatment in the solubilization step, the treatment liquid contains the hardly decomposable substance at a relatively high concentration. Therefore, when the hardly decomposable substance processing step is performed on such a processing solution, the decomposition efficiency is high. In the circulatory system,
There is an advantage that the amount of the hardly decomposable substance returned to the biological treatment step (1) can be reduced.

[0010] The fourth invention of the present application is the treatment method of the first or second invention, wherein the step (4) of treating the hardly decomposable substance comprises:
It is characterized in that it is performed on the treated water obtained in the solid-liquid separation step (2). The treatment liquid containing a relatively high concentration of the hardly decomposable substance returned from the solubilization step (3) is subjected to the biodegradation treatment in the biological treatment step (1). Preferentially, degradable organic matter undergoes decomposition. Therefore, after the biological treatment step, the concentration of the hardly decomposable substance is increased to some extent, and the treated water obtained as a result of the separation in the solid-liquid separation step (2) is subjected to the hardly decomposable substance treatment step (4). Is effective, and the decomposition efficiency is improved.

The fifth invention of the present application is the treatment method according to the first or second invention, wherein the step (4) of treating the hardly decomposable substance is a treatment liquid obtained by the solubilization step (3) and a solid-liquid separation step (2). )). This combines the advantages of the third invention and the fourth invention, and the decomposition of the hardly decomposable substance is sufficiently achieved.

The sixth invention of the present application is the treatment method according to any one of the third to fifth inventions, wherein the treatment water obtained in the solid-liquid separation step (2) or the treatment liquid obtained in the solubilization step (3) is used. In the step (4) of treating the hardly decomposable substance, the carrier for immobilizing organisms is used. Microorganisms capable of decomposing hardly decomposable substances are sequentially trapped in the bioimmobilized carrier, so that the decomposition efficiency can be gradually increased.

A seventh invention of the present application is the above-mentioned treatment method, wherein the step (4) of treating the hardly decomposable substance is performed by aerobic treatment. The aerobic treatment is preferable to be employed in the hardly decomposable substance treatment step (4) in view of the resolution of the hardly decomposable substance, the complexity of the process, and the required price and scale of the device.

The eighth invention of this application is characterized in that, in the above-mentioned treatment method, the step (4) of treating a hardly decomposable substance is performed by treatment with a familiar microorganism. In the aerobic treatment in the seventh invention, the hardly decomposable substance is suitably treated by the acclimated microorganism.

The ninth invention of the present application is characterized in that in any one of the above-mentioned treatment methods, the solubilizing step (3) is performed by reducing the molecular weight of an insoluble substance by the action of a microorganism. By utilizing microorganisms (especially thermophilic bacteria) in solubilization in this way, there is no need for special equipment or reagents, and therefore, there is no possibility of further contamination by reagents, and solubilization can be performed efficiently in a simple process. The volume of sludge can be reduced.

Finally, a tenth invention of the present application is an organic wastewater treatment apparatus for implementing the treatment methods of the first to ninth inventions of the present invention, wherein a biological treatment tank, solid-liquid separation The present invention relates to a processing apparatus comprising a tank, a solubilizing tank, a tank for treating hardly decomposable substances, and a path for connecting the tanks and transporting liquid and / or sludge. As described above, the sludge amount is reduced by the treatment device, and the hardly decomposable substance is decomposed with good efficiency.
The quality of the generated wastewater can be improved.

[0017]

Embodiments of the present invention will be described below.

FIG. 1 shows an apparatus schematically illustrating a preferred embodiment of the method of the present invention. In a wastewater treatment method using this apparatus, raw wastewater is first subjected to a biological treatment step in a biological treatment tank 1, where organic substances in the wastewater are removed by oxidative decomposition based on aerobic microbial digestion, such as carbon dioxide and water. Is converted to Next, the biological treatment liquid is subjected to a solid-liquid separation step in the solid-liquid separation tank 2 and is separated into sludge and treated water A. This sludge is then introduced into the solubilization tank 3, where the sludge is solubilized by thermophilic bacteria at a high temperature. Thus, the solid component of the sludge is converted into a water-soluble component, and the volume of the sludge can be reduced. However, the hardly decomposable substance is eluted from the sludge into the liquid. Treatment liquid B after solubilization, which is relatively rich in hardly decomposable substances obtained by this treatment
Is then introduced into the hardly decomposable substance treatment tank 4, where the hardly decomposable substance undergoes digestion and decomposition by a familiar microorganism under aerobic conditions to be converted to a readily decomposable substance, and a part of carbon,
Converted to water. Thereafter, the treatment liquid C after the decomposition of the hardly decomposable substance is returned to the biological treatment step again, and by performing the same circulating treatment in the same manner as described above, a sufficient sludge volume reduction and a treatment not containing a large amount of the hardly decomposable substance The discharge of water A is achieved. A part of the sludge after the solid-liquid separation tank 2 is returned to the biological treatment 1 step so that the biological digestion can be continuously performed while appropriately maintaining the amount of organic matter in the biological treatment.

In the embodiment of the present invention illustrated in FIG. 1, the respective structures of the biological treatment tank 1, the solid-liquid separation tank 2, and the solubilization tank 3 and the paths connecting these are not particularly limited, but are essential. Conventionally, those conventionally used can be used. Various conditions and the like in each step in these tanks may be performed according to conventionally known biological treatment methods, solid-liquid separation methods, solubilization methods, and the like (see Japanese Patent Application Laid-Open No. 9-10791). .

Briefly, first, the biological treatment step in the biological treatment tank 1 is carried out at room temperature, preferably at a ventilation rate of 0.1 to 0.5 vvm, so that aerobic digestion and decomposition can be tolerated by aeration means. Implemented. However, depending on the load, the treatment may be performed at a higher temperature with an even larger ventilation rate. The preferred temperature range is 10 to
It is 50 degreeC, More preferably, it is 20-30 degreeC. The liquid to be treated is preferably adjusted to near neutrality, that is, to a pH of about 5 to 8, so that aerobic digestion and decomposition can proceed smoothly. The biological treatment tank 1 does not necessarily need to be an aeration tank, but may be another aerobic treatment tank or an anaerobic treatment tank. In this case, in order to perform the biological treatment step anaerobically, the stirring means by circulating the liquid in the tank, the stirring means by circulating aeration of the generated gas, the stirring means by a stirrer such as a stirring blade, or the active microorganism fixing means And so on.

As the solid-liquid separation tank 2, means such as sedimentation by gravity sedimentation, centrifugation or filtration (including membrane separation) is selected. Of these, since specially expensive equipment and labor are not required, sedimentation in a sedimentation tank is most preferable if separation is easy depending on the properties of the treatment liquid.

In the solubilization tank 3, a solid is reduced in molecular weight / solubilized by an anaerobic or aerobic microbial reaction and a physicochemical decomposition reaction by heat under high temperature conditions. The solubilization treatment is preferably operated in a temperature range from 50 to 90C. For example, when using microorganisms separated from excess sewage sludge, the temperature is preferably in the range of 60 to 80 ° C., preferably about 60 to 80 ° C., so that both the solubilization reaction and the physicochemical thermal decomposition by heat can occur efficiently and sufficiently simultaneously. It is good to operate at 65 ° C. Heating may be performed by a heater, steam introduction, or the like. Further, the pH at the time of the solubilization treatment is preferably around neutral to weakly alkaline, and the solubilization may be performed anaerobic or aerobic. The solubilization treatment may be performed while stirring under normal pressure, and a conventional aeration apparatus and stirring means may be provided for aerobic solubilization.
In the case of anaerobic solubilization, a stirring means by circulating the liquid in the tank, a stirring means by circulating aeration of the generated gas, a stirring means by a stirrer such as a stirring blade, or a means for fixing active microorganisms, What has the means for making an organic solid matter contained in a processing object contact microorganisms efficiently can be used.

The conditions for these solubilization treatments vary depending on the type and concentration of organic solids contained in the sludge to be treated and the optimum solubilization temperature of microorganisms capable of decomposing the solids. It is possible and set so that both the microbial reaction and the physicochemical decomposition reaction proceed well. In order to promote solubilization, thermophilic bacteria such as Bacillus stearothermophilus and enzymes such as protease, lipase and glycosidase may be used alone or in combination. , Thermal alkali decomposition or the like may be used in combination.

The hardly decomposable substance treating tank 4 is provided mainly for decomposing the hardly decomposable substance, which is an organic substance released into the liquid in the solubilizing tank 3, into carbon dioxide and water. As described above, the treatment liquid B after solubilization is in a state in which the hardly decomposable substance is released from the sludge and the liquid contains a large amount of this substance. The liquid in which the hardly decomposable substance is relatively concentrated as described above is preferably subjected to the aerobic decomposition treatment of the hardly decomposable substance. This aerobic treatment is preferably performed by a conditioned microorganism. The acclimated microorganism is
For example, it grows by acclimation of microorganisms contained in wastewater, and can be acclimated in the hardly decomposable substance treatment tank 4.
The processing conditions in the hardly decomposable substance processing tank 4 may be set so as to promote biological digestion and decomposition, and the temperature is usually room temperature, preferably 10 to 50 ° C, more preferably 20 to 30 ° C. The pH is preferably adjusted to 5 to 8, preferably around neutrality. For aerobic treatment, preferably the ventilation rate is between 0.1 and 0.5 vvm. In short, the conditions under which digestion and decomposition by the acclimated microorganisms smoothly proceed are set. Alternatively, microorganisms grown and grown separately may be added.

Furthermore, it is also effective to add microorganisms having the ability to decompose hardly decomposable substances, for example, in the case of cellulose-containing wastewater, addition of cellulolytic bacteria such as Cellulomonas and Cellvibrio, and addition of cellulolytic enzymes such as cellulase. is there. When the raw wastewater is a pulp waste liquid, it may be effective to add a white rot fungus such as basidiomycete or a lignin-degrading enzyme such as lignin peroxidase.

Furthermore, in order to trap the acclimated microorganisms and promote the decomposition reaction efficiently, a bioimmobilized carrier, for example, a carrier composed of a porous ceramic, a plastic molded product, or a fibrous filter medium such as a cellulosic material is charged. Can also. However, when the solubilized solution B contains a large amount of sludge, the sludge component is deposited on the carrier, and therefore, even if the immobilized carrier is used, it may not be very useful. Further, an adsorbent such as activated carbon which can adsorb a hardly decomposable substance may be added.

FIG. 2 schematically shows a second embodiment of the present invention. In this case, the hardly decomposable substance treatment tank 4 is disposed next to the solid-liquid separation tank 2, and undergoes biodegradation, solid-liquid separation, and solubilization by a conventional method to be decomposed in the biological treatment tank 1. The treated water in which the difficult hardly decomposable substance remains is subjected to the hardly decomposable substance treatment. In the second embodiment, since only the liquid substantially not containing the sludge component flows into the hardly decomposable substance treating tank 4, the hardly decomposable substance treating tank 4 is described in the first embodiment. Even if an appropriate amount of the biologically immobilized carrier is introduced, such an inconvenience as deposition of sludge on the immobilized carrier does not occur, as described above. Therefore, the immobilized carrier can be suitably used in the second embodiment. . When such an immobilized carrier is used, as the treated water A sequentially flows in the circulation system, microorganisms having the resolution of the hardly degradable substance contained in the treated water are gradually attached to the carrier and trapped, and the hardly degradable substance is trapped. The decomposition treatment in the treatment tank 4 is promoted. It is also considered preferable to apply an immobilized enzyme or an immobilized microorganism in which the above-mentioned enzyme or microorganism having the ability to decompose a hardly decomposable substance is immobilized on such an immobilized carrier in advance.

In the second embodiment, since a treatment tank for a hardly decomposable substance is added to a path for discharging treated water of an existing apparatus, it is considered that it is relatively easy to adopt and easy to maintain. Can be

FIG. 3 schematically shows an organic wastewater treatment apparatus according to still another embodiment of the present invention. The embodiment shown here is based on the embodiment in which the embodiments of the present invention shown in FIGS. 1 and 2 are combined, and it can be expected that reduction of the most hardly decomposable substances is expected, and therefore the quality of treated water A is improved. Conceivable.

The respective steps of the wastewater treatment method of the present invention described above may be performed in any of a batch system and a continuous system, and the overall treatment time is determined by the physical properties of the wastewater to be treated and the size and shape of each treatment tank. Is set appropriately in view of the above.

[0031]

EXAMPLES Examples of the present invention will be described below. However, the scope of the present invention should not be construed as being limited by these examples.

Example 1 Wastewater discharged from a petrochemical factory was treated according to the treatment method of the present invention including the step of treating a hardly decomposable substance shown in FIG. The wastewater had a water quality shown in Table 1 below.

The waste water is transferred to the biological treatment tank 1 (with a capacity of 40 L).
0.3vv in a square aeration tank made of transparent vinyl chloride
The temperature was maintained at room temperature (25 ° C.) with aeration at a rate of m. Volume load, was at 0.8kg-BOD / m ³ / day. The liquid after the biological treatment was separated into sludge and treated water by using a transparent vinyl chloride rectangular sedimentation tank 2 having a content of 10 L as described below. The precipitated sludge concentration was 6000 mg / L.
Next, the obtained sludge was introduced into a solubilization tank 3 (a cylindrical cylindrical tank having an internal volume of 2 L), and a ventilation rate of 0.5 vvm and 65 ° C.
Aerobically solubilized. Then, the solubilized solution B
Was subjected to decomposition treatment in a hardly decomposable substance treatment tank 4 (a transparent vinyl chloride square tank having an internal capacity of 4 L). here,
Room temperature (25 ° C) while aerating with a ventilation volume of 0.3 vvm
The treatment liquid C is returned to the biological treatment tank 1 via a return route, and a part of the sludge from the sedimentation tank is returned to the biological treatment tank 1 for 100 days in the circulation system. The treatment was performed, and treated water A was collected from the solid-liquid separation tank 2.

Example 2 Wastewater treatment was carried out in the same manner as in Example 1 according to the treatment method of the present invention including the treatment step for a hardly decomposable substance shown in FIG.

Except that the treatment liquid from the solubilization tank 3 is directly returned to the biological treatment tank 1, and the treatment with the hardly decomposable substance treatment tank 4 is performed on the treated water from the solid-liquid separation tank 2. The processing was continued substantially as in the example. However, about 4 L of a porous filter material (coal ash sintered filter material) was charged into the hardly decomposable substance treatment tank 4 as a bioimmobilization carrier.

From the hardly decomposable substance treatment tank 4, treated water A
Was collected.

Comparative Example 1 The same circulation treatment as in Example 1 was performed in accordance with the conventional treatment method shown in FIG. 4, except that the treatment with a hardly decomposable substance was not performed.

[Comparative Example 2] Although not shown, the same circulation treatment was carried out by the treatment method without the solubilization step in the method of Comparative Example 1, that is, in both biological treatment and solid-liquid separation steps.

The treated water A and the solubilized treatment liquid B in Examples 1 and 2 and the treated liquid C for the treatment with hardly decomposable substances in Example 1, and the quality of each treated water in Comparative Examples 1 and 2 were as follows. Was examined. Table 1 shows the results.

BOD: 2 according to JIS K 0102
Biological oxygen consumption measurement based on the amount of dissolved oxygen consumed after leaving the diluent at 0 ° C. for 5 days CODMn: based on the oxygen consumption by potassium permanganate at 100 ° C. according to JIS K 0102,
Chemical Oxygen Consumption Measurement S-TOC: The filtrate filtered through a glass fiber filter paper having a pore size of 1 μm according to JIS K 0102 is also JIS K
Combustion oxidation according to 0102-measured by infrared TOC analysis method SS: Residue on filter paper filtered through a glass fiber filter paper having a pore size of 1 μm according to JIS K 0102 is 105 to 110 ° C.
Dry and weigh

[0041]

[Table 1]

As is clear from Table 1, the treated water of Examples 1 and 2 has CODMn, ST
Both OC and SS were low, and the water quality was clearly improved. In addition, the water quality indicated by the treated water in these examples was almost the same as the result in Comparative Example 2;
Although a large amount of sludge is generated in this example, no sludge was generated in the examples, and it was clarified that the method of the present invention was a preferable treatment method.

[0043]

According to the method for treating organic wastewater of the present invention, by providing a process for treating a hardly decomposable substance, the hardly decomposable material which had to be discarded in the state of being undecomposed into the treated wastewater until now is provided. The amount of toxic substances can be reduced, and the quality of treated wastewater can be improved. Therefore, the method and apparatus of the present invention have the effects of stabilizing the efficiency of solubilizing excess sludge and reducing the cause of environmental pollution by improving the quality of treated water.

[Brief description of the drawings]

FIG. 1 is a view schematically showing an organic wastewater treatment apparatus according to one embodiment of the present invention.

FIG. 2 is a view schematically showing an organic wastewater treatment apparatus according to another embodiment of the present invention.

FIG. 3 is a view schematically showing an organic wastewater treatment apparatus according to still another embodiment of the present invention.

FIG. 4 is a view schematically showing a conventional method for treating organic wastewater.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Biological treatment tank 2 ... Solid-liquid separation tank 3 ... Solubilization tank 4 ... Persistent substance treatment tank

Continued on the front page F term (reference) 4D003 AA12 AB02 BA02 CA03 CA07 EA01 EA22 FA07 4D028 AB00 AB03 BC18 BD11 BD12 BD16 4D040 DD03 DD11 DD31

Claims (10)

[Claims] 1. The following steps: (1) a biological treatment step in which wastewater is biologically treated; (2) a solid-liquid separation step in which a mixed liquid after biological treatment is separated into treated water and sludge; And (3) an organic wastewater treatment method including a solubilization step in which sludge is solubilized, wherein a recalcitrant substance treatment step for decomposing a refractory substance that is not easily decomposed in the biological treatment step (1) ( A processing method further comprising: 4). 2. The treatment method according to claim 1, wherein the treatment liquid after the solubilization step (3) is again subjected to the biological treatment step (1), and the treatment is performed by a circulation system. 3. The processing method according to claim 1, wherein the step (4) for treating the hardly decomposable substance is performed on the processing solution obtained in the solubilizing step (3). 4. The treatment method according to claim 1, wherein the step (4) for treating the hardly decomposable substance is performed on the treated water obtained in the solid-liquid separation step (2). 5. The method according to claim 1, wherein the step (4) of treating the hardly decomposable substance is performed on the treatment liquid obtained by the solubilization step (3) and the treatment water obtained by the solid-liquid separation step (2). Or the processing method of 2. 6. An organism is immobilized in the hardly decomposable substance treating step (4) performed on the treated water obtained in the solid-liquid separating step (2) or the treating solution obtained in the solubilizing step (3). The method according to any one of claims 3 to 5, wherein a carrier for conversion is used. 7. The processing method according to claim 1, wherein the hardly decomposable substance processing step (4) is performed by aerobic processing. 8. The treatment method according to claim 7, wherein the step (4) of treating the hardly decomposable substance is performed by treatment with a familiar microorganism. 9. The treatment method according to claim 1, wherein the solubilizing step (3) is performed by the action of a microorganism. 10. An organic wastewater treatment apparatus for performing the treatment method according to any one of claims 1 to 9, comprising a biological treatment tank, a solid-liquid separation tank, a solubilization tank, and a hardly decomposable substance. A processing apparatus comprising: a processing tank; and a path for connecting the tanks to transport liquid and / or sludge.