JP7099265B2 - Wastewater treatment equipment and wastewater treatment method - Google Patents

Description

The present invention relates to a wastewater treatment apparatus and a wastewater treatment method.

In recent years, from the viewpoint of environmental protection and the like, there is a strong demand for a technique for purifying wastewater containing COD (chemical oxygen demand) components such as phenols. The activated sludge method is known as such a technique. In the activated sludge method, wastewater is treated using activated sludge (a microorganism that decomposes COD components in the wastewater). Then, the treated wastewater (treated water) is introduced into the settling tank, and the activated sludge in the treated water is settled in the settling tank. This removes activated sludge from the treated water. Then, the supernatant liquid is discharged from the settling tank and discharged.

Patent Documents 1 to 3 describe a fluidized bed carrier method as a technique related to the activated sludge method. In the fluidized bed carrier method, activated sludge is supported on a carrier that flows in the fluidized bed carrier tank. Then, the wastewater is treated using the activated sludge carried on the carrier. Also in the fluidized bed carrier method, the wastewater (treated water) after treatment contains activated sludge, although it is less than that in the activated sludge method. Therefore, if necessary, the treated water is introduced into the settling tank, and the activated sludge in the treated water is settled in the settling tank. This removes activated sludge from the treated water. Then, the supernatant liquid is discharged from the settling tank and discharged. According to the fluidized bed carrier method, it can be expected that the treatment speed will be higher than that of the activated sludge method.

Japanese Patent No. 3410699 Japanese Unexamined Patent Publication No. 2010-17669 Japanese Patent Application Laid-Open No. 2002-86175

By the way, the fluidized bed carrier method has a problem that activated sludge is difficult to settle in a settling tank. Therefore, there is a possibility that the supernatant liquid contains a large amount of activated sludge. As a method for solving such a problem, a method of adding a precipitating agent to the treated water discharged from the settling tank has been proposed. According to this method, activated sludge in the treated water can be precipitated by the precipitating agent. However, since this method requires a large amount of precipitating agent, it requires a large amount of labor in operation and also increases the cost.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to facilitate the precipitation of activated sludge in the treated water discharged from the fluidized bed carrier tank, and by extension, the present invention. It is an object of the present invention to provide a new and improved wastewater treatment apparatus and wastewater treatment method capable of reducing the amount of precipitant used.

In order to solve the above problems, according to a certain viewpoint of the present invention, it is a wastewater treatment device that purifies the water to be treated, and has an activity of treating the water to be treated and discharging the treated water as the treated water. The sludge tank and the fluidized bed carrier tank, the settling tank that stores the treated water discharged from the activated sludge tank and the fluidized bed carrier tank and precipitates the activated sludge dispersed in the treated water, and the activated sludge that has settled in the settling tank. Provided is a wastewater treatment apparatus comprising, at least, a sludge returning mechanism for returning to a fluidized bed carrier tank.

Here, it is returned to the fluidized bed carrier tank based on the measuring device for measuring at least one of the precipitation property and the concentration of the suspended substance in the treated water discharged from the fluidized bed carrier tank and the measured value by the measuring device. A control device for controlling the amount of active sludge may be provided.

Further, the control device controls the amount of activated sludge returned to the fluidized bed carrier tank so that the value measured by the measuring device becomes a predetermined value, and the precipitation property of suspended solids is indicated by SV30, which is a predetermined value corresponding to SV30. May be less than 100%.

Further, the predetermined value of the concentration of suspended solids may be 1000 mg / L or more.

Further, it is provided with a diversion mechanism for distributing and introducing the water to be treated into the activated sludge tank and the fluidized bed carrier tank, and the diversion mechanism may introduce more water to be treated into the fluidized bed carrier tank than the activated sludge tank. ..

Further, the water to be treated may contain phenols.

Further, the water to be treated may contain coke oven wastewater.

According to another aspect of the present invention, a step of treating water to be treated using an activated sludge tank and a fluidized bed carrier tank and discharging the treated water as treated water, and an activated sludge tank and a fluidized bed carrier. A step of introducing the treated water discharged from the tank into the settling tank and precipitating the activated sludge dispersed in the treated water in the settling tank, and a step of returning the activated sludge settled in the settling tank to at least the fluidized bed carrier tank. , A method of treating wastewater is provided, which comprises.

Here, at least one of the precipitation property and the concentration of the suspended substance in the treated water discharged from the fluidized bed carrier tank is measured, and the fluidized bed is based on the measured value of at least one of the precipitation property and the concentration. The amount of active sludge returned to the carrier tank may be controlled.

Further, the amount of activated sludge returned to the fluidized bed carrier tank is controlled so that the measured value becomes a predetermined value, the precipitation property of suspended solids is indicated by SV30, and the predetermined value corresponding to the SV30 is less than 100%. May be.

Further, the predetermined value of the concentration of suspended solids may be 1000 mg / L or more.

Further, the water to be treated may be distributed and introduced into the activated sludge tank and the fluidized bed carrier tank, and more water to be treated may be introduced into the fluidized bed carrier tank than the activated sludge tank.

Further, the water to be treated may contain phenols.

Further, the water to be treated may contain coke oven wastewater.

As described above, according to the present invention, since the activated sludge settled in the settling tank is returned to at least the fluidized bed carrier tank, it is possible to facilitate the settling of the activated sludge in the treated water discharged from the fluidized bed carrier tank. As a result, it becomes possible to reduce the amount of the precipitant used.

It is explanatory drawing which shows the whole structure of the wastewater treatment apparatus which concerns on embodiment of this invention. It is a graph which shows the correlation between the operation days (days) of a wastewater treatment apparatus, the mass adhering activated sludge to a carrier (g / 10 pieces), or the COD concentration (mg / L) of the treated water of a fluidized bed carrier tank. It is a graph which shows the correlation between the operation day (day) of a wastewater treatment apparatus, and the use amount (L / day) of a coagulant. It is a graph which shows the correlation between the operation days (days) of a wastewater treatment apparatus, and MLSS (mg / L) of the treated water of a fluidized bed carrier tank. It is a graph which shows the correlation between the operation days (days) of a wastewater treatment apparatus, and SV30 (%) of the treated water of a fluidized bed carrier tank. It is a photograph which shows the surface state of the fluidized bed carrier tank when activated sludge is not returned to the fluidized bed carrier tank. It is a photograph which shows the surface state of the fluidized bed carrier tank at the time of returning activated sludge to the fluidized bed carrier tank.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, and duplicate description will be omitted.

<1. Configuration of wastewater treatment equipment>
First, the overall configuration of the wastewater treatment apparatus 1 according to the present embodiment will be described with reference to FIG. The wastewater treatment device 1 includes an activated sludge tank 10, a fluidized bed carrier tank 20, a settling tank 30, a diversion mechanism 40, a merging mechanism 50, a measuring device 51, a sludge return mechanism 60, a coagulation settling tank 70, and a control device 100.

The shunt mechanism 40 distributes and introduces the water to be treated into the activated sludge tank 10 and the fluidized bed carrier tank 20. The water to be treated in this embodiment is not particularly limited as long as it contains a COD component. The COD component is, for example, phenols. Examples of the water to be treated containing a COD component include coke oven effluent (cheap water) generated in the coke manufacturing process, coal gasified effluent generated in the coal gasification process, and washing effluent generated in the acetylene refining process. In the present embodiment, it is also possible to use the wastewater diluted with seawater as the water to be treated.

The shunt mechanism 40 has a main pipe 40a that connects the supply source of the water to be treated and the fluidized bed carrier tank 20, and a branch pipe 40b that branches from the main pipe 40a and connects to the activated sludge tank 10. The main pipe 40a introduces the water to be treated into the fluidized bed carrier tank 20, and the branch pipe 40b introduces the water to be treated into the activated sludge tank 10. Here, the main pipe 40a is provided with a valve 41a, and the branch pipe 40b is provided with a valve 41b. By adjusting the opening degrees of these valves 41a and 41b, the flow rate of the water to be treated introduced into the activated sludge tank 10 and the fluidized bed carrier tank 20 is adjusted. The treatment speed (treatment capacity) of the fluidized bed carrier tank 20 is generally higher than the treatment speed of the activated sludge tank 10. Therefore, it is preferable to introduce more water to be treated into the fluidized bed carrier tank 20 than the activated sludge tank 10 during the operation of the wastewater treatment device 1. The flow dividing mechanism 40 is not necessarily limited to the above configuration, and may be any mechanism as long as the water to be treated can be distributed and introduced into the activated sludge tank 10 and the fluidized bed carrier tank 20. Further, the mechanism introduced into the activated sludge tank 10 and the fluidized bed carrier tank 20 is not necessarily limited to the shunt mechanism 40. For example, the piping system for introducing the water to be treated into the activated sludge tank 10 and the piping system for introducing the water to be treated into the fluidized bed carrier tank 20 may be independent of each other.

The activated sludge tank 10 is a tank that decomposes the COD component in the water to be treated by the activated sludge. The specific configuration of the activated sludge tank 10 is not particularly limited, and may be any configuration similar to that of the conventional activated sludge tank. Generally, activated sludge that decomposes COD components is acclimatized in the activated sludge tank 10. Then, after the water to be treated is introduced into the activated sludge tank 10, the water to be treated is aerated. As a result, the activated sludge dispersed in the water to be treated proliferates while decomposing the COD component. The water to be treated, that is, the treated water treated by the activated sludge tank 10 is introduced into the settling tank 30 through a confluence pipe 50a described later. Activated sludge is dispersed in the treated water, and the activated sludge in the treated water precipitates in the settling tank 30. As a result, activated sludge is collected. Hereinafter, the treated water discharged from the activated sludge tank 10 is also referred to as "activated sludge treated water".

The method of introducing the activated sludge into the activated sludge tank 10 is not particularly limited. For example, activated sludge may be collected from another activated sludge tank that has already been treated with the same water to be treated as in the present embodiment, and the activated sludge may be charged into the activated sludge tank 10 as a seed. Then, by introducing the water to be treated into the activated sludge tank 10 and further aerating the water to be treated, the activated sludge as a seed proliferates while decomposing the COD component. As a result, the activated sludge is introduced into the activated sludge tank 10. Activated sludge may be collected from another activated sludge tank treated with water to be treated different from the present embodiment, and the activated sludge may be charged into the activated sludge tank 10 as a seed. However, if the water to be treated is different, since the activated sludge is composed of different microbial species, it may take time for the activated sludge tank 10 to have sufficient treatment capacity. As another method, when the water to be treated contains seawater, a method of introducing the water to be treated into the activated sludge tank 10 and aerating the water to be treated can be mentioned. Since seawater is mixed in the treated water, the treated water contains microorganisms that lived in the seawater. Such microorganisms oxidatively decompose and proliferate COD components by aeration. As a result, the activated sludge is introduced into the activated sludge tank 10. However, in this method, it takes time for the activated sludge tank 10 to have sufficient treatment capacity. Therefore, it is preferable to use the activated sludge collected from another activated sludge tank that is treating the water to be treated as in the present embodiment as a seed and put it into the activated sludge tank 10.

The fluidized bed carrier tank 20 is a tank that decomposes the COD component in the water to be treated by the activated sludge carried on the carrier. The specific configuration of the fluidized bed carrier tank 20 is not particularly limited, and may be any configuration similar to that of the conventional fluidized bed carrier tank 20. For example, in addition to the fluidized bed carrier tank disclosed in Patent Documents 1 to 3, the fluidized bed carrier tank disclosed in Japanese Patent Application Laid-Open No. 2016-11256 may be applied to the present embodiment. Generally, a large number of carriers carrying activated sludge are charged in the fluidized bed carrier tank 20. Then, after the water to be treated is introduced into the fluidized bed carrier tank 20, the water to be treated is aerated. As a result, the carrier dispersed in the water to be treated flows. Further, the activated sludge carried on the carrier proliferates while decomposing the COD component. Further, in the present embodiment, as will be described later, the activated sludge collected in the settling tank 30 is returned to the fluidized bed carrier tank 20. Such activated sludge is dispersed in the fluidized bed carrier tank 20 and decomposes the COD component together with the activated sludge carried on the carrier. The water to be treated, that is, the treated water treated by the fluidized bed carrier tank 20, is introduced into the settling tank 30 through the confluence pipe 50b described later. Hereinafter, the treated water discharged from the fluidized bed carrier tank 20 is also referred to as “fluidized bed treated water”.

Activated sludge is dispersed in the fluidized bed treated water. The activated sludge dispersed in the fluidized bed-treated water includes activated sludge peeled off from the carrier, activated sludge having no adhesiveness, and activated sludge returned from the settling tank 30. Therefore, more suspended solids are contained in the fluidized bed treated water than in the case where the activated sludge is not returned to the fluidized bed carrier tank 20. That is, the value of MLSS of the fluidized bed treated water becomes large. However, as described in Examples described later, by returning the activated sludge to the fluidized bed carrier tank 20, the activated sludge in the fluidized bed treated water is likely to settle. It should be noted that such an effect cannot be obtained simply by introducing the activated sludge treated water and the fluidized bed treated water into the settling tank 30. Therefore, in order to facilitate the precipitation of activated sludge, it is important to return the activated sludge to the fluidized bed carrier tank 20. The present inventor considers this reason as follows. The activated sludge that settles in the settling tank 30, that is, the activated sludge that is returned to the fluidized bed carrier tank 20, contains the activated sludge that has been acclimatized in the active sludge tank 10. Such activated sludge tends to settle. Therefore, the activated sludge having good sedimentation property is the activated sludge having poor sedimentation property in the fluidized bed carrier tank 20 (that is, the activated sludge that is peeled off from the carrier and discharged together with the fluidized bed treated water or is non-adhesive and dispersible. It is considered that the sedimentation property of the activated sludge as a whole was improved by involving the activated sludge).

The carrier used in the fluidized bed carrier tank 20 is not particularly limited, and the carrier used in the conventional fluidized bed carrier method can be used. For example, conventionally known carriers that have been used so far in industrial wastewater treatment facilities, food wastewater treatment facilities, industrial water treatment facilities, waste disposal site wastewater treatment facilities, community plants, septic tanks, and the like can be used. More specifically, carriers having various shapes (for example, porous cube, skeleton-like sphere, small cylinder, tube, etc.) are sold by various manufacturers, and these can be used without particular limitation. The carrier preferably has a large specific surface area and a porosity of a size that allows microorganisms to enter (usually, the diameter of the carrier is about 1 μm).

The method of supporting the activated sludge on the carrier is not particularly limited. For example, activated sludge collected in the activated sludge tank 10 or another activated sludge tank (preferably, this activated sludge tank is treated with the same water to be treated as in the present embodiment). May be charged into the sludge carrier tank 20 as a seed. After that, the water to be treated is introduced into the fluidized bed carrier tank 20, and the water to be treated is further aerated, so that the activated sludge as a seed is supported on the carrier while decomposing the COD component. As a result, activated sludge is supported on the carrier. As another method, a method of introducing water to be treated into the fluidized bed carrier tank 20 and aerating the water to be treated can be mentioned. Since seawater is mixed in the treated water, the treated water contains microorganisms that lived in the seawater. Such microorganisms decompose the COD component by aeration and proliferate. Then, the grown microorganisms are supported on the carrier as activated sludge. However, in this method, it takes time for the fluidized bed carrier tank 20 to have sufficient processing capacity. Therefore, a method of charging the activated sludge as a seed into the fluidized bed carrier tank 20 is preferable. In the examples described later, the activated sludge acclimated in the activated sludge tank 10 is charged into the fluidized bed carrier tank 20 as a seed to support the activated sludge on the carrier.

When the activated sludge is supported on the carrier to a certain thickness, the activated sludge existing in the vicinity of the carrier is covered with other activated sludge. Therefore, it is difficult for air to reach the activated sludge existing in the vicinity of the carrier. In other words, it becomes an anaerobic environment. Under such an environment, anaerobic activated sludge can be expected to grow. Therefore, it is considered that not only aerobic activated sludge but also anaerobic activated sludge is acclimatized in the fluidized bed carrier tank 20, so that the fluidized bed carrier tank 20 can decompose more various COD components. You can expect it.

The merging mechanism 50 includes merging pipes 50a and 50b. As described above, the combined pipe 50a introduces the activated sludge treated water into the settling tank 30, and the combined pipe 50b introduces the fluidized bed treated water into the settling tank 30. These treated waters merge in the settling tank 30. However, the liquid bed treated water contains activated sludge that has settled in the settling tank 30 (such activated sludge includes activated sludge that has been acclimatized in the active sludge tank 10, that is, activated sludge that tends to settle). There is.

The settling tank 30 stores treated water (hereinafter, also referred to as “mixed treated water”) in which activated sludge treated water and fluidized bed treated water are mixed. The settling tank 30 precipitates activated sludge in the mixed treatment water. The activated sludge in the mixed-treated water includes activated sludge dispersed in the activated sludge-treated water and activated sludge dispersed in the fluidized bed carrier-treated water. The former activated sludge tends to settle. The latter activated sludge is easily settled by returning the activated sludge settled in the settling tank 30 to the fluidized bed carrier tank 20. Therefore, activated sludge is likely to settle in the settling tank 30 as a whole. That is, it is possible to promote the precipitation of activated sludge in the settling tank 30. The precipitated activated sludge is returned to at least the fluidized bed carrier tank 20 via the sludge return mechanism 60.

The sludge return mechanism 60 returns the activated sludge settled in the settling tank 30 to the activated sludge tank 10 and the fluidized bed carrier tank 20. Specifically, the sludge return mechanism 60 includes a main pipe 60a that connects the lower end of the settling tank 30 and the activated sludge tank 10, and a branch pipe 60b that branches from the main pipe 60a and connects to the fluidized bed carrier tank 20. Has. The main pipe 60a returns the activated sludge (substantially mixed treated water in which the activated sludge is dispersed) to the activated sludge tank 10. The branch pipe 60b returns the activated sludge (substantially mixed treated water in which the activated sludge is dispersed) to the fluidized bed carrier tank 20. Here, the main pipe 60a is provided with a valve 61a, and the branch pipe 60b is provided with a valve 61b. By adjusting the opening degrees of these valves 61a and 61b, the amount of activated sludge returned to the activated sludge tank 10 and the fluidized bed carrier tank 20 (substantially the flow rate of the mixed treated water in which the activated sludge is dispersed) is adjusted. To. The sludge returning mechanism 60 does not necessarily have to return the activated sludge to the activated sludge tank 10 if the amount of activated sludge in the activated sludge tank 10 is sufficient. That is, the sludge returning mechanism 60 may return the activated sludge to at least the fluidized bed carrier tank 20. In addition, activated sludge that cannot be returned and becomes excessive may be treated by incineration or the like.

The supernatant liquid of the settling tank 30 is introduced into the coagulation settling tank 70. Activated sludge is slightly dispersed in the treated water introduced into the coagulation sedimentation tank 70. Such activated sludge can reduce the quality of treated water. Therefore, in the coagulation settling tank 70, such activated sludge is settled with a coagulant. The amount of the flocculant input is not particularly limited, and may be appropriately adjusted according to the quality required for the treated water discharged from the wastewater treatment device 1. According to the present embodiment, by returning the activated sludge to the fluidized bed carrier tank 20, it is possible to promote the precipitation of the activated sludge in the settling tank 30. Therefore, the amount of activated sludge contained in the treated water introduced into the coagulation sedimentation tank 70 is small. Therefore, the amount of the flocculant input can be reduced. The type of the flocculant is not particularly limited, and may be, for example, an iron-based inorganic flocculant, an organic polymer flocculant, or the like. The supernatant liquid of the coagulation sedimentation tank 70 is discharged to the outside of the wastewater treatment apparatus 1 as the final treatment water.

As described above, in the present embodiment, by returning the activated sludge to the fluidized bed carrier tank 20, the activated sludge in the fluidized bed treated water is likely to settle. Therefore, it is possible to promote the precipitation of activated sludge in the settling tank 30. Further, by returning the activated sludge to the fluidized bed carrier tank 20, the foaming generated in the fluidized bed carrier tank 20 can be eliminated. For example, the non-patent literature "Colic, M., Morse, W., Lechter, A., Hicks, J., Holley, S., & Mattia, C. (2008). As disclosed in "wastewater. Patenting's of the Water Environment Federation, 2008 (13), 3358-3374", it is known that foaming also occurs in the fluidized bed carrier tank 20. Although the cause of foaming is not clear, the present inventor speculates that foaming occurs when the carriers rub against each other. Such foaming may reduce the quality of the treated water finally discharged from the wastewater treatment device 1. That is, the foaming itself may deteriorate the quality of the treated water. Further, in the coagulation sedimentation tank 70, since the coagulant is charged from above the foaming, it may be difficult for the coagulant to permeate into the treated water. Therefore, the sedimentation efficiency in the coagulation sedimentation tank 70 may decrease. Therefore, it is preferable that foaming is suppressed as much as possible. As shown in Examples described later, by returning the activated sludge to the fluidized bed carrier tank 20, the foaming generated in the fluidized bed carrier tank 20 can be eliminated. It is presumed that the returned activated sludge suppressed the rubbing between the carriers.

Here, a configuration for promoting the precipitation of activated sludge in the settling tank 30 will be described in more detail. That is, the confluence pipe 50b is provided with a measuring device 51. The measuring device 51 measures the concentration of suspended solids in the fluidized bed treated water. Here, the suspended solids include activated sludge. More specifically, the measuring device 51 measures the MLSS (mg / L) of the fluidized bed treated water. The measuring device 51 may be, for example, a commercially available MLSS meter. MLSS is measured by a method according to JIS K 0102. The MLSS measured by the measuring device 51 is input to the control device 100.

The control device 100 has a hardware configuration such as a CPU, a ROM, a RAM, a communication device (a device capable of receiving information from the measuring device 51), and a drive device for valves 61 and 62. A program or the like necessary for performing the following processing is recorded in the ROM, and the CPU reads and executes the program. As a result, the control device 100 performs the following processing.

That is, the control device 100 controls the amount of activated sludge returned to the fluidized bed carrier tank 20 based on the value measured by the measuring device 51, that is, the MLSS of the fluidized bed treated water. More specifically, the control device 100 controls the amount of activated sludge returned to the fluidized bed carrier tank 20 so that the MLSS of the fluidized bed treated water becomes a predetermined value. Here, the predetermined value is the MLSS of the fluidized bed treated water when the SV30 of the fluidized bed treated water is less than 100%. SV30 (%) is a precipitate, that is, an index indicating how much precipitation occurs, and the value becomes smaller as the amount of precipitation increases. Therefore, if no precipitation occurs after the fluidized bed treated water is allowed to stand for 30 minutes, the SV30 becomes 100%, and if even a small amount of precipitation occurs, the SV30 becomes less than 100%. The larger the amount of precipitation, the smaller the SV30. SV30 is a value measured by 5.6 of JIS B 9944.

As shown in Examples described later, the larger the MLSS of the fluidized bed treated water, the smaller the SV30 tends to be. If SV30 is less than 100%, precipitation is promoted, so the predetermined value may be MLSS when SV30 is less than 100%. Then, the control device 100 controls the amount of activated sludge returned to the fluidized bed carrier tank 20 so that the MLSS of the fluidized bed treated water becomes a predetermined value. Specifically, the control device 100 adjusts the opening degrees of the valves 61 and 62. Here, the predetermined value is preferably 1000 mg / L or more. When the MLSS is 1000 mg / L or more, the SV30 becomes very small (specifically, less than 30%), so that the precipitation of activated sludge can be more strongly promoted in the settling tank 30.

As described in detail above, according to the present embodiment, the activated sludge settled in the settling tank 30 is returned to the fluidized bed carrier tank 20 to promote the settling of the activated sludge in the settling tank 30 and to promote the settling of the activated sludge in the fluidized bed 30. Foaming in the carrier tank 20 can be suppressed. Further, since the settling of activated sludge in the settling tank 30 can be promoted, the treatment capacity of the wastewater treatment device 1 can be easily increased. That is, in order to increase the treatment capacity of the wastewater treatment device 1, a large amount of water to be treated may be introduced into the fluidized bed carrier tank 20. However, simply introducing a large amount of water to be treated into the fluidized bed carrier tank 20 requires a large amount of coagulant in the coagulation sedimentation tank 70. This is because when a large amount of water to be treated is introduced into the fluidized bed carrier tank 20, the fluidized bed treated water contains a large amount of activated sludge that is difficult to settle. Since these activated sludges do not sufficiently settle in the settling tank 30, a large amount of activated sludge will be introduced into the coagulation and settling tank 70. Therefore, many flocculants are needed. On the other hand, according to the present embodiment, since the activated sludge settled in the settling tank 30 is returned to the fluidized bed carrier tank 20, it is possible to promote the settling of the activated sludge in the settling tank 30. Therefore, even when a large amount of water to be treated is introduced into the fluidized bed carrier tank 20, a large amount of activated sludge can be settled in the settling tank 30. That is, the amount of activated sludge introduced into the coagulation sedimentation tank 70 can be reduced, and the amount of the coagulant used can be reduced. Therefore, the treatment capacity of the wastewater treatment device 1 can be easily increased.

As shown in FIG. 1, in the present embodiment, the activated sludge tank 10 and the fluidized bed carrier tank 20 are arranged in parallel, and the activated sludge settled in the settling tank 30 is returned to the fluidized bed carrier tank 20. Will be done. As a result, the above-mentioned effect can be obtained. Patent Document 1 discloses a technique in which an activated sludge tank is arranged in the subsequent stage of a fluidized bed carrier tank, and a settling tank is further arranged in the subsequent stage. The activated sludge settled in the settling tank is returned to the activated sludge tank. Patent Document 2 also discloses a similar technique. However, the effect of this embodiment cannot be obtained by this technique. First, since the activated sludge is not returned to the fluidized bed carrier tank, the activated sludge is unlikely to settle in the settling tank. Furthermore, foaming of the fluidized bed carrier tank cannot be suppressed. As a result, a large amount of foam flows into the activated sludge tank. Further, since the water to be treated introduced into the activated sludge tank has already been treated in the fluidized bed carrier tank, its components may vary. As described above, the water to be treated introduced into the activated sludge tank contains a large amount of foaming and its composition varies. Therefore, it may be difficult to control the activated sludge tank. In Patent Document 3, activated sludge is returned to the fluidized bed carrier tank when the wastewater treatment device is started up, but this technique is only related to the start-up time of the wastewater treatment device. Further, the activated sludge returned to the fluidized bed carrier tank is generated in the fluidized bed carrier tank, and the amount of activated sludge is very small in the first place. Therefore, even in Patent Document 3, the effect of this embodiment cannot be obtained.

<2. Wastewater treatment method using wastewater treatment equipment>
(2-1. Preparation stage)
Next, a wastewater treatment method using the wastewater treatment device 1 will be described. In the preparatory stage, first, the activated sludge is sufficiently acclimatized in the activated sludge tank 10 (specifically, to the extent that the treated water of a desired quality can be obtained only in the activated sludge tank 10). The method of acclimatization is as described above.

Then, the operation of the wastewater treatment device 1 is started. Specifically, first, the water to be treated is introduced into each of the activated sludge tank 10 and the fluidized bed carrier tank 20 by using the shunting mechanism 40. Here, a desired amount of carrier and activated sludge as a seed are charged into the fluidized bed carrier tank 20 in advance. The source of this activated sludge is not particularly limited, and may be, for example, one acclimatized in the activated sludge tank 10, or another activated sludge tank (this activated sludge tank uses the same water to be treated as in the present embodiment). It may be collected from (preferably processed) or returned from the settling tank 30. Although such pre-filling of activated sludge may be omitted, it is preferable to pre-fill the activated sludge in order to enable the fluidized bed carrier tank 20 to operate at an early stage. Since the activated sludge is not supported on the carrier at this point, it is preferable that the amount of sludge returned from the settling tank 30 is about the same as that of the activated sludge tank 10, as will be described later. Further, more water to be treated may be introduced into the activated sludge tank 10 than the fluidized bed carrier tank 20. The valves 41a and 41b may be adjusted artificially or automatically by using the control device 100.

Then, the water to be treated is treated in the activated sludge tank 10. Specifically, the water to be treated is aerated in the activated sludge tank 10. As a result, the activated sludge dispersed in the water to be treated proliferates while decomposing the COD component. The water to be treated by the activated sludge tank 10, that is, the activated sludge treated water is introduced into the settling tank 30 through the confluence pipe 50a. On the other hand, the water to be treated is also treated in the fluidized bed carrier tank 20. Specifically, the water to be treated is aerated in the fluidized bed carrier tank 20. At this point, almost no activated sludge is carried on the carrier, but the activated sludge previously charged into the fluidized bed carrier tank 20, the activated sludge that is settled in the settling tank 30 and returned via the sludge returning mechanism 60, and the subject. Microorganisms (that is, activated sludge) contained in the treated water decompose the COD component and adhere to the carrier. The water to be treated by the fluidized bed carrier tank 20, that is, the fluidized bed treated water is introduced into the settling tank 30 through the confluence pipe 50b.

In the settling tank 30, treated water in which activated sludge treated water and fluidized bed treated water are mixed, that is, mixed treated water is stored. The settling tank 30 precipitates activated sludge in the mixed treatment water. The precipitated activated sludge is returned to the activated sludge tank 10 and the fluidized bed carrier tank 20 via the sludge return mechanism 60. Here, by adjusting the opening degrees of the valves 61 and 62, the amount of activated sludge returned to the activated sludge tank 10 and the fluidized bed carrier tank 20 (substantially the mixed treated water in which the activated sludge is dispersed) is adjusted. Will be done. The valves 61 and 62 may be adjusted artificially or automatically by using the control device 100. In the early stages of the preparatory stage, the amount of activated sludge carried on the carrier is small. Therefore, it is preferable to increase the amount of activated sludge returned to the fluidized bed carrier tank 20 (for example, the amount returned to the activated sludge tank 10 is about the same). The activated sludge returned to the fluidized bed carrier tank 20 is supported on the carrier.

On the other hand, the supernatant liquid of the settling tank 30 is introduced into the coagulation settling tank 70. In the coagulation sedimentation tank 70, the coagulant is added to the treated water. As a result, the activated sludge remaining in the treated water precipitates. The supernatant liquid of the coagulation sedimentation tank 70 is discharged to the outside of the wastewater treatment apparatus 1 as the final treatment water.

In the preparation stage, the operation of the wastewater treatment device 1 is continuously performed. As a result, the amount of activated sludge carried on the carrier of the fluidized bed carrier tank 20 gradually increases. That is, the activated sludge is acclimatized in the fluidized bed carrier tank 20. Here, the processing capacity of the fluidized bed carrier tank 20 is higher than the processing capacity of the activated sludge tank 10. Therefore, as the amount of activated sludge carried on the carrier of the fluidized bed carrier tank 20 increases, the amount of water to be treated to be introduced into the activated sludge tank 10 is reduced, and the amount of water to be treated to be introduced into the fluidized bed carrier tank 20 is increased. Is preferable. Further, it is preferable to gradually reduce the amount of activated sludge returned to the fluidized bed carrier tank 20. Here, it is particularly preferable to adjust the amount of activated sludge returned to the fluidized bed carrier tank 20 so that the MLSS of the fluidized bed treated water becomes a predetermined value or more.

The preparation stage is completed when the activated sludge is sufficiently acclimatized in the fluidized bed carrier tank 20 (specifically, to the extent that the treated water of a desired quality can be obtained only in the fluidized bed carrier tank 20).

(2-2. Steady operation)
After the preparatory stage is completed, the wastewater treatment device 1 is operated in a steady state. First, the water to be treated is introduced into each of the activated sludge tank 10 and the fluidized bed carrier tank 20 by using the shunting mechanism 40. Here, the flow rate of the water to be treated to be introduced into the activated sludge tank 10 and the fluidized bed carrier tank 20 is adjusted by adjusting the opening degrees of the valves 41a and 41b. Since the treatment capacity of the fluidized bed carrier tank 20 is higher than the treatment capacity of the activated sludge tank 10, it is preferable to introduce more water to be treated into the fluidized bed carrier tank 20 than the activated sludge tank 10. For example, the activated sludge tank 10 may be introduced with water to be treated to the extent that the activated sludge returned to the fluidized bed carrier tank 20 can be acclimatized, and most of the water to be treated may be introduced into the fluidized bed carrier tank 20. That is, if the activated sludge acclimatized in the activated sludge tank 10 is considered as a coagulant, the activated sludge tank 10 in the present embodiment can be considered as a tank that produces activated sludge as a coagulant. In the present embodiment, since the water to be treated is introduced into the activated sludge tank 10, activated sludge serving as a flocculant can be stably produced.

Then, the water to be treated is treated in the activated sludge tank 10. Specifically, the water to be treated is aerated in the activated sludge tank 10. As a result, the activated sludge dispersed in the water to be treated proliferates while decomposing the COD component. The water to be treated by the activated sludge tank 10, that is, the activated sludge treated water is introduced into the settling tank 30 through the confluence pipe 50a. On the other hand, the water to be treated is also treated in the fluidized bed carrier tank 20. Specifically, after the water to be treated is introduced into the fluidized bed carrier tank 20, the water to be treated is aerated. As a result, the carrier dispersed in the water to be treated flows. Further, the activated sludge carried on the carrier proliferates while decomposing the COD component. The activated sludge settled in the settling tank 30 is returned to the fluidized bed carrier tank 20. The activated sludge returned from the settling tank 30 is dispersed in the fluidized bed carrier tank 20 and decomposes the COD component together with the activated sludge carried on the carrier. Further, the activated sludge returned from the settling tank 30 suppresses foaming of the fluidized bed carrier tank 20. The water to be treated by the fluidized bed carrier tank 20, that is, the fluidized bed treated water is introduced into the settling tank 30 through the confluence pipe 50b.

In the settling tank 30, treated water in which activated sludge treated water and fluidized bed treated water are mixed, that is, mixed treated water is stored. The settling tank 30 precipitates activated sludge in the mixed treatment water. Here, since the activated sludge settled in the settling tank 30 is returned to the fluidized bed carrier tank 20, the activated sludge is very likely to settle in the settling tank 30. The precipitated activated sludge is returned to the activated sludge tank 10 and the fluidized bed carrier tank 20 via the sludge return mechanism 60. Here, by adjusting the opening degrees of the valves 61 and 62, the amount of activated sludge returned to the activated sludge tank 10 and the fluidized bed carrier tank 20 (substantially the mixed treated water in which the activated sludge is dispersed) is adjusted. Will be done.

Specifically, the measuring device 51 measures the MLSS (mg / L) of the fluidized bed treated water. The MLSS measured by the measuring device 51 is input to the control device 100. The control device 100 controls the amount of activated sludge returned to the fluidized bed carrier tank 20 based on the value measured by the measuring device 51, that is, the MLSS of the fluidized bed treated water. More specifically, the control device 100 controls the amount of activated sludge returned to the fluidized bed carrier tank 20 so that the MLSS of the fluidized bed treated water becomes a predetermined value. Here, the predetermined value is the MLSS of the fluidized bed treated water when the SV30 of the fluidized bed treated water is less than 100%. The predetermined value is preferably 1000 mg / L or more. In this case, since the SV 30 becomes very small (specifically, less than 30%), the precipitation of activated sludge in the settling tank 30 can be more strongly promoted.

On the other hand, the supernatant liquid of the settling tank 30 is introduced into the coagulation settling tank 70. In the coagulation sedimentation tank 70, the coagulant is added to the treated water. As a result, the activated sludge remaining in the treated water precipitates. In the present embodiment, the activated sludge is returned to the fluidized bed carrier tank 20 to promote the precipitation of the activated sludge in the settling tank 30. Therefore, the amount of activated sludge contained in the treated water introduced into the coagulation sedimentation tank 70 is small. Therefore, the amount of the flocculant input can be reduced. The supernatant liquid of the coagulation sedimentation tank 70 is discharged to the outside of the wastewater treatment apparatus 1 as the final treatment water. After that, the above-mentioned steady operation is repeated.

The wastewater treatment method described above is merely an example, and the wastewater treatment device 1 may be operated by another method. For example, in the above-mentioned example, the activated sludge was returned to the fluidized bed carrier tank 20 in the preparation stage, but such return may be omitted in the preparation stage. In this case, the activated sludge charged in advance into the fluidized bed carrier tank 20 and the microorganisms contained in the water to be treated gradually adhere to the carrier and proliferate. Further, the processing performed by the control device 100 may be performed artificially. That is, the manager of the wastewater treatment device 1 may check the measured value by the measuring device 51 and adjust the opening degrees of the valves 61 and 62 according to the result. As described above, SV30 is mentioned as a parameter corresponding to MLSS. Therefore, the administrator of the wastewater treatment device 1 may perform the following processing in parallel with or in place of the processing for adjusting the opening degree of the valves 61 and 62 according to the measured value by the measuring device 51. good. That is, the manager measures the SV30 of the fluidized bed treated water by hand analysis. The measuring method may be any method conforming to JIS B 9944 5.6. The administrator adjusts the opening degrees of the valves 61 and 62 so that the SV 30 becomes a predetermined value. That is, the manager adjusts the amount of activated sludge to be returned to the activated sludge tank 10 and the fluidized bed carrier tank 20. Here, as described above, if even a small amount of precipitation occurs, the SV30 becomes less than 100%. Therefore, the predetermined value corresponding to SV30 is less than 100%. The predetermined value is preferably less than 70%, more preferably less than 30%. In this case, more activated sludge precipitates from the fluidized bed treated water. Such processing may be performed automatically (that is, the SV 30 may be measured by the measuring device, and the control device 100 may adjust the opening degrees of the valves 61 and 62 according to the value).

Next, an embodiment of the present embodiment will be described. In this embodiment, in order to confirm that the effect of this embodiment is obtained, the wastewater treatment apparatus 1 is operated as follows, and each parameter is measured and verified at that time.

<1. Operation of wastewater treatment equipment>
The wastewater treatment device 1 was operated as follows. First, the water to be treated was prepared. The water to be treated was coke oven wastewater diluted with seawater. The coke oven wastewater is a coke oven wastewater containing about 2000 to 8000 mg / L of COD component, and the coke oven wastewater diluted with seawater was used as the treated water. Here, the concentration of the COD component was measured based on "oxygen consumption by potassium permanganate at 100 ° C." specified in JIS K 0102.

Then, the activated sludge was put into the activated sludge tank 10. Here, the volume of the activated sludge tank 10 is about 2000 m ³ . The activated sludge to be put into the activated sludge tank 10 is collected from the activated sludge tank that has already been treated with the water to be treated. On the other hand, a commercially available carrier was charged into the fluidized bed carrier tank 20 at a ratio of approximately 10% by volume with respect to the volume of the fluidized bed carrier tank 20 (first loading). Here, the volume of the fluidized bed carrier tank 20 is about 2000 m ³ . The carrier was charged again 95 days after the start date of operation (second loading), and finally the volume% of the carrier was approximately 16% by volume with respect to the volume of the fluidized bed carrier tank 20.

Then, the operation of the wastewater treatment device 1 was started. The specific operation method was the same as the operation method in the preparation stage described above. Here, on the operation start date (operation days = 0), the flow rate to the activated sludge tank 10 (drainage inflow load) was set to 110 m ³ / hr, and the flow rate to the fluidized bed carrier tank 20 was set to 100 m ³ / hr. Then, as the number of operating days elapsed, the flow rate to the activated sludge tank 10 was decreased, and the flow rate to the fluidized bed carrier tank 20 was increased. Then, at the last _day of the following period T6, the flow rate to the activated sludge tank 10 was set to 89 m ³ / hr, and the flow rate to the fluidized bed carrier tank 20 was set to 121 m ³ / hr. After that, the flow rate to the fluidized bed carrier tank 20 was gradually increased. That is, when the number of operating days reached the 233rd day, the flow rate to the activated sludge tank 10 / the flow rate to the fluidized bed carrier tank 20 was set to 95 m ³ / hr / 130 m ³ / hr, and the number of operating days became the 258th day. The flow rate to the activated sludge tank 10 / the flow rate to the fluidized bed carrier tank 20 was set to 90 m ³ / hr / 135 m ³ / hr. Further, when the number of operating days reached the 265th day, the flow rate to the activated sludge tank 10 / the flow rate to the fluidized bed carrier tank 20 was set to 85 m ³ / hr / 140 m ³ / hr, and the number of operating days became 288 days. The flow rate to the activated sludge tank 10 / the flow rate to the fluidized bed carrier tank 20 was set to 80 m ³ / hr / 145 m ³ / hr.

The amount of activated sludge returned to the activated sludge tank 10 (specifically, the flow rate of the mixed treated water in which the activated sludge was dispersed) was fixed at 90 m ³ / hr. On the other hand, the amount of activated sludge returned to the fluidized bed carrier tank 20 (specifically, the flow rate of the mixed treated water in which the activated sludge was dispersed) was reduced as the number of operating days elapsed. Specifically, 90 m ³ / hr from the operation start date (number of operating days = 0) to 69 days (period T ₁ ), and 70 m ³ / hr, 84 from 70 days to 83 days (period T ₂ ). 50m ³ / hr from day to 94th (period T ₃ ), 30m ³ / hr from 95th to 109th (period T ₄ ), 110th to 130th (period T ₅ ) Was 10 m ³ / hr. Then, it was set to 0 m ³ / hr from the 131st day to the 221st day (period T ₆ ). That is, during the period _T6 , the activated sludge was not returned to the fluidized bed carrier tank 20. After the 221st day (period T ₇ ), it was set to 20 m ³ / hr. That is, in period _T7 , the return of activated sludge to the fluidized bed carrier tank 20 was resumed.

<2. Changes in the mass of activated sludge attached to the carrier>
The adhered weight (adhered mass) (g / 10 pieces) of the activated sludge to the carrier was measured at _any timing within the above period T1 to _T7 , and the transition of the adhered mass was evaluated. The measurement was performed by the following method. That is, 10 carriers were arbitrarily collected from the fluidized bed carrier tank 20. Then, these carriers and 50 ml of pure water were put into a plastic bag with a zipper to prepare a test sample. Then, the test sample was charged into an ultrasonic washer (AS ONE manufactured by AS ONE), and ultrasonic treatment was performed at output High for 5 minutes. Then, the dispersion liquid in the test sample was put into a drying dish. This operation was repeated until the deposits on the carrier became invisible, and the dispersion was added to the drying dish each time. Then, the dispersion was dried at 100 ° C., and the dry mass of the residue was measured. This was taken as the adhesion mass. After the second loading of the carrier, the adhered mass was measured for each of the carrier of the first loading and the carrier of the second loading. In addition, the carrier of the first charge and the carrier of the second charge can be distinguished by their appearance. The graph on the upper side of FIG. 2 shows the measurement result. For the carrier added for the second time, only the measurement results for a predetermined period after the addition are shown. The point P1 indicates the adhered mass of the carrier of the first charge, and the point P2 indicates the adhered mass of the carrier of the second charge. As is clear from this graph, it can be seen that the adhered mass of activated sludge increases with the lapse of operating days. In addition, the adhered mass became almost stable after the end of the period _T6 .

<3. Changes in COD concentration>
The COD concentration of the fluidized bed drainage was measured at _any timing within the above period T1 to _T7 , and the transition of the COD concentration was evaluated. The concentration of the COD component was measured based on "oxygen consumption by potassium permanganate at 100 ° C." specified in JIS K 0102. The lower graph in FIG. 2 shows the measurement results. Specifically, the point P3 in the graph indicates the COD concentration. As is clear from this graph, it can be seen that the COD component is decomposed by the fluidized bed carrier tank 20. The COD concentration temporarily increased during the period _T6 , because the activated sludge was not returned. During the period _T7 when the return of activated sludge was resumed, the COD concentration decreased again. Further, in the period _T7 , the flow rate of the water to be treated to the fluidized bed carrier tank 20 was increased, but the water to be treated could be treated without any problem.

<4. Changes in the amount of coagulant used>
The transition of the amount of the flocculant used was evaluated at any timing within the above period _T1 to _T7 . Here, in this embodiment, a commercially available iron-based inorganic coagulant is used as the coagulant, and the coagulant is used so that the transparency of the treatment liquid discharged from the coagulation sedimentation tank 70 becomes equal to or higher than a preset control value. Adjusted usage. Here, the transparency was measured based _on the "transparency" specified in JIS K 0102, and the control value was kept constant within the above period T1 to _T7 . The results are shown in FIG. As is clear from FIG. 3, during the period T ₁ to T ₅ and T ₇ in which the activated sludge is returned to the fluidized bed carrier tank 20, the amount of the flocculant used decreases, whereas the activated sludge is used as the fluidized bed carrier. During the period _T6 when the sludge was not returned to the tank 20, the amount of the flocculant used increased. Therefore, it can be seen that a large amount of activated sludge is settled in the settling tank 30 by returning the activated sludge to the fluidized bed carrier tank 20.

<5. Correlation between MLSS and SV30>
The MLSS (mg / L) and SV30 (%) of the fluidized bed treatment liquid were measured at any timing within the above period T ₆ to T ₇ . The measurement method of each parameter is as described above. The results are shown in FIGS. 4 and 5. As is clear from FIGS. 4 and ₅ , the MLSS is approximately less than 1000 mg / L and the SV30 is 100 (%) during the period T6 in which the activated sludge is not returned to the fluidized bed carrier tank 20. On the other hand, during the period T7 in which the activated sludge is returned to the fluidized bed carrier tank 20, the _MLSS rises to about 1000 mg / L or more. Further, in the period when the MLSS is 1000 mg / L or more, the SV30 is less than 100%, particularly less than 30%. That is, activated sludge in the fluidized bed treated water is likely to settle. Above <4. Based on the transition of the amount of coagulant used> and the result of this test, it can be seen that the predetermined value to be compared with the value measured by the measuring device 51 is preferably 1000 mg / L or more.

<6. Correlation between the return of activated sludge to the fluidized bed carrier tank and foaming>
FIG. ₆ is a photograph showing the surface state of the fluidized bed carrier tank 20 in the period T6, and FIG. ₇ is a photograph showing the surface state of the fluidized bed carrier tank 20 in the period T7. As is clear from FIGS. 6 and 7, it can be seen that foaming is greatly suppressed by returning the activated sludge to the fluidized bed carrier tank 20.

Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person having ordinary knowledge in the field of the art to which the present invention belongs can come up with various modifications or modifications within the scope of the technical idea described in the claims. , These are also naturally understood to belong to the technical scope of the present invention.

1 Wastewater treatment equipment 10 Activated sludge tank 20 Fluidized bed carrier tank 30 Sedimentation tank 40 Dividing mechanism 50 Confluence mechanism 51 Measuring device 60 Sludge return mechanism 70 Coagulation sedimentation tank 100 Control device

Claims (14)

A wastewater treatment device that purifies the water to be treated.
An activated sludge tank and a fluidized bed carrier tank that treat the treated water and discharge the treated water as treated water.
A settling tank that stores the treated water discharged from the activated sludge tank and the fluidized bed carrier tank and precipitates the activated sludge dispersed in the treated water.
A wastewater treatment apparatus comprising: a sludge returning mechanism for returning activated sludge settled in the settling tank to at least the fluidized bed carrier tank. A measuring device for measuring at least one of the precipitation property and the concentration of suspended solids in the treated water discharged from the fluidized bed carrier tank.
The wastewater treatment device according to claim 1, further comprising a control device for controlling the amount of activated sludge returned to the fluidized bed carrier tank based on the measured values by the measuring device. The control device controls the amount of activated sludge returned to the fluidized bed carrier tank so that the value measured by the measuring device becomes a predetermined value.
The wastewater treatment apparatus according to claim 2, wherein the precipitation property of the suspended solid is indicated by SV30, and the predetermined value corresponding to the SV30 is less than 100%. The wastewater treatment apparatus according to claim 3, wherein the predetermined value of the concentration of the suspended solid is 1000 mg / L or more. A shunt mechanism for distributing and introducing the water to be treated into the activated sludge tank and the fluidized bed carrier tank is provided.
The wastewater treatment apparatus according to any one of claims 1 to 4, wherein the shunting mechanism introduces a larger amount of the water to be treated into the fluidized bed carrier tank than the activated sludge tank. The wastewater treatment apparatus according to any one of claims 1 to 5, wherein the water to be treated contains phenols. The wastewater treatment apparatus according to claim 6, wherein the treated water contains coke oven wastewater. A step of treating water to be treated using an activated sludge tank and a fluidized bed carrier tank, and discharging the treated water as treated water.
A step of introducing the treated water discharged from the activated sludge tank and the fluidized bed carrier tank into the settling tank and precipitating the activated sludge dispersed in the treated water in the settling tank.
A wastewater treatment method comprising a step of returning the activated sludge settled in the settling tank to at least the fluidized bed carrier tank. At least one of the precipitation property and the concentration of suspended solids in the treated water discharged from the fluidized bed carrier tank was measured.
The wastewater treatment method according to claim 8, wherein the amount of activated sludge returned to the fluidized bed carrier tank is controlled based on the measured value of at least one of the precipitability and the concentration. The amount of activated sludge returned to the fluidized bed carrier tank is controlled so that the measured value becomes a predetermined value.
The wastewater treatment method according to claim 9, wherein the precipitation property of the suspended solid is indicated by SV30, and the predetermined value corresponding to the SV30 is less than 100%. The wastewater treatment method according to claim 10, wherein the predetermined value of the concentration of the suspended solid is 1000 mg / L or more. The water to be treated is distributed and introduced into the activated sludge tank and the fluidized bed carrier tank.
The wastewater treatment method according to any one of claims 8 to 11, wherein a larger amount of the water to be treated is introduced into the fluidized bed carrier tank than the activated sludge tank. The wastewater treatment method according to any one of claims 8 to 12, wherein the water to be treated contains phenols. 13. The wastewater treatment method according to claim 13, wherein the water to be treated contains coke oven wastewater.

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