JP7262332B2 - Water treatment method and water treatment equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a technology of a water treatment method and a water treatment apparatus.

Conventionally, an activated sludge method utilizing a collection of microorganisms called floc (aerobic biological sludge) has been used for biological wastewater treatment. However, in the activated sludge method, when flocs (aerobic biological sludge) and treated water are separated in a sedimentation basin, the sedimentation velocity of flocs is slow, so the surface area of the sedimentation basin must be made very large in some cases. In addition, the processing speed of the activated sludge method depends on the sludge concentration in the biological treatment tank, and although the processing speed can be increased by increasing the sludge concentration, solid-liquid separation problems such as bulking occur. may make it impossible to maintain processing.

On the other hand, in anaerobic biological treatment, it is common to utilize aggregates called granules, which are densely aggregated aggregates of microorganisms. Since granules have a very high sedimentation rate and microbes are densely aggregated, it is possible to increase the sludge concentration in the biological treatment tank and realize high-speed treatment of wastewater. However, compared to aerobic treatment (activated sludge method, etc.), anaerobic biological treatment has problems such as the limited types of wastewater to be treated and the need to maintain the treated water temperature at 30 to 35°C. may have In addition, if the anaerobic biological treatment alone is used, the quality of the treated water is poor, and when the treated water is discharged into a river or the like, it may be necessary to separately perform an aerobic treatment such as an activated sludge method.

In recent years, it has become clear that by using a semi-batch treatment system that intermittently flows wastewater into a reaction tank, not only anaerobic biological sludge but also aerobic biological sludge can be formed into granulated biological sludge with high sedimentation properties. (see Patent Documents 1 to 4, for example). The granulated biological sludge has, for example, an average particle size of 0.2 mm or more and a settling velocity of 5 m/h or more. In the semi-batch type biological treatment, four processes are performed in one reaction tank: (1) inflow of wastewater, (2) biological treatment of substances to be treated, (3) sedimentation of biological sludge, and (4) discharge of treated water. It is common to repeat the process.

In addition, Patent Document 5 describes a semi-batch type biological system that repeats three processes: (1) inflow of wastewater and discharge of treated water, (2) biological treatment of substances to be treated, and (3) sedimentation of biological sludge. A processing method is disclosed. This makes it possible to obtain biological sludge with high sedimentation properties such as granulated biological sludge.

WO2004/024638 Japanese Patent Application Laid-Open No. 2008-212878 Japanese Patent No. 4975541 Japanese Patent No. 4804888 JP 2016-77931 A

By the way, in the semi-batch type biological treatment, it is necessary to form a concentration gradient of the substance to be treated (for example, organic matter) to be biologically treated in the tank. condition) and starvation condition (state in which the concentration of the substance to be treated in the tank is low) is considered to be an important factor in obtaining biological sludge with high settling property. However, in the semi-batch type biological treatment in which the treated water is discharged together with the inflow of wastewater, the wastewater containing the substances to be treated that flows into the tank is discharged out of the tank together with the treated water without sufficient contact with the biological sludge. It may be done. Therefore, after the inflow of waste water/discharge of treated water, it is difficult to keep the concentration of the substance to be treated remaining in the tank high. As a result, it may be difficult to form biological sludge with high settling property.

In the semi-batch type biological treatment in which the treated water is discharged along with the inflow of the wastewater, a distributor is installed at the bottom of the reaction tank to supply the wastewater in an upward flow. In this case, not only is the installation of a distributor expensive, but there is a concern that the biological sludge will clog the inflow port and cause a short-circuit flow if the distributor is installed, and regular maintenance will be required.

Accordingly, an object of the present invention is to provide a water treatment method and a water treatment apparatus that can efficiently increase the concentration of substances to be treated remaining in a tank after inflow of wastewater/discharge of treated water. That's what it is.

The present invention is a water treatment method for biologically treating wastewater using a reaction tank containing biological sludge in a tank provided with an inlet and an outlet, wherein the an inflow/discharge step of discharging biologically treated water in the reaction tank from the outlet while inflowing wastewater; a biological treatment step of biologically treating the wastewater in the reaction tank with biological sludge; and a settling step for settling the biological sludge, wherein the outlet is arranged at a water level in the reaction tank, and the inlet is configured to absorb at least part of the waste water from the settling step. is a water treatment method in which water is supplied horizontally into the biological sludge layer formed at the bottom of the reaction tank.

Moreover, in the water treatment method, it is preferable that the inlet is arranged at a position lower than the interface position of the biological sludge layer formed on the bottom of the reaction tank in the sedimentation step.

Further, in the water treatment method, it is preferable that a pipe extending in a vertical direction is connected to the inlet, and the waste water is supplied to the inlet from the pipe by gravity.

Further, in the water treatment method, the inside of the reaction tank is divided by a partition wall into a first chamber into which the waste water is introduced and a second chamber in which the operation cycle step is performed, and the outlet is the second chamber. provided on the chamber side and arranged at the water level in the second chamber, the inlet is provided in the partition so that the first chamber and the second chamber communicate, and It is preferably arranged at a position lower than the interface level of the biological sludge layer formed on the bottom of the second chamber, and supplies the waste water horizontally into the biological sludge layer formed on the bottom of the second chamber.

Moreover, in the water treatment method, it is preferable that the reaction tank is a square water tank, and that the inlet and the outlet are provided on the same surface of the square water tank.

Further, in the water treatment method, the flow velocity v (cm/sec) of waste water at the inlet and the horizontal distance N (m) from the inlet to the side surface of the reaction vessel facing the inlet are It is preferable to satisfy the following formula.
20≦v/N ^1/2 ≦80

In addition, the present invention includes a reaction tank for containing biological sludge in a tank provided with an inlet and an outlet, and while wastewater is flowing into the reaction tank from the inlet, the reaction is carried out from the outlet. An inflow/discharge step of discharging biologically treated water in a tank, a biological treatment step of biologically treating the wastewater in the reaction tank with biological sludge, and a sedimentation step of settling the biological sludge in the reaction tank. A water treatment apparatus for performing repeated operation cycle steps, wherein the outlet is installed at a water level in the reaction tank, and the inlet is configured to direct at least part of the waste water to the bottom of the reaction tank in the sedimentation step. It is a water treatment device that feeds horizontally into the formed biological sludge layer.

Moreover, in the water treatment apparatus, the inlet is preferably installed at a position lower than the interface position of the biological sludge layer formed on the bottom of the reaction tank in the sedimentation step.

Moreover, it is preferable that the water treatment apparatus includes a pipe extending in a vertical direction, the pipe being connected to the inlet, and the waste water being supplied to the inlet from the pipe by gravity.

Further, in the water treatment apparatus, the reaction tank has a partition wall that divides the inside of the tank into a first chamber into which the waste water is introduced and a second chamber in which the operation cycle process is performed. provided on the second chamber side and arranged at the water level in the second chamber; It is preferable that, in the sedimentation step, it is arranged at a position lower than the interface level of the biological sludge layer formed on the bottom of the second chamber, and that the waste water is horizontally supplied into the biological sludge layer formed on the bottom of the second chamber. .

Moreover, in the water treatment apparatus, it is preferable that the reaction tank is a square water tank, and that the inlet and the outlet are provided on the same surface of the square water tank.

Further, in the water treatment apparatus, the flow velocity v (cm/sec) of waste water at the inlet and the horizontal distance N (m) from the inlet to the side surface of the reaction vessel facing the inlet are It is preferable to satisfy the following formula.
20≦v/N ^1/2 ≦80

ADVANTAGE OF THE INVENTION According to the present invention, it is possible to provide a water treatment method and a water treatment apparatus that can efficiently increase the concentration of substances to be treated remaining in a tank after inflow of wastewater/discharge of treated water. It becomes possible.

(A) is a schematic cross-sectional view showing an example of a water treatment apparatus according to this embodiment, and (B) is a schematic top view showing an example of a water treatment apparatus according to this embodiment. It is a schematic cross section which shows an example of the state of the water treatment apparatus at the time of a biological treatment process. FIG. 4 is a schematic cross-sectional view showing an example of the state of the water treatment device during the sedimentation process; FIG. 4 is a schematic cross-sectional view showing an example of the state of the water treatment device during the inflow/discharge process. 1 is a schematic top view showing an example of a square-shaped reaction vessel employed in a large-scale treatment plant; FIG. FIG. 4 is a schematic top view showing another example of a square-shaped reaction tank employed in a large-scale treatment plant. (A) is a schematic cross-sectional view showing another example of a square reaction vessel employed in a large-scale treatment plant, and (B) is a square reaction vessel employed in a large-scale treatment plant. It is a schematic top view showing another example of. (A) is a schematic cross-sectional view showing another example of the water treatment apparatus of the present embodiment, and (B) is a schematic top view showing another example of the water treatment apparatus of the present embodiment. (A) is a schematic cross-sectional view showing another example of the water treatment apparatus of the present embodiment, and (B) is a schematic top view showing another example of the water treatment apparatus of the present embodiment. (A) is a cross-sectional view showing another example of the water treatment apparatus of this embodiment, and (B) is a schematic top view showing another example of the water treatment apparatus of this embodiment. (A) is a schematic cross-sectional view showing another example of the water treatment apparatus of the present embodiment, and (B) is a schematic top view showing another example of the water treatment apparatus of the present embodiment. (A) is a schematic cross-sectional view showing another example of the water treatment apparatus of the present embodiment, and (B) is a schematic top view showing another example of the water treatment apparatus of the present embodiment. FIG. 10 is a graph showing the results of the bromide ion residual rate versus the flow velocity at the inlet in Examples 2 and 3; FIG. 4 is a diagram showing changes in SVI5 and SVI30, which are sedimentation indices of sludge in reaction tanks. It is an input sludge and a sludge observation photograph 50 days after start-up.

An embodiment of the present invention will be described below. This embodiment is an example of implementing the present invention, and the present invention is not limited to this embodiment.

FIG. 1(A) is a schematic cross-sectional view showing an example of a water treatment apparatus according to this embodiment, and FIG. 1(B) is a schematic top view showing an example of a water treatment apparatus according to this embodiment. As shown in FIG. 1A, the water treatment apparatus 1 includes a reaction tank 10, a raw water introduction device having a raw water introduction pipe 12, a raw water pump 14 and an electromagnetic valve 16, and an air diffuser having a blower 18 and an air diffuser pipe 20. A device, a treated water collection channel 22 and a control device 24 are provided. It should be noted that FIG. 1B omits the air diffusion device including the blower 18 and the air diffusion pipe 20 and the control device 24 .

The reaction tank 10 of the present embodiment includes an inlet 26 through which waste water flows into the tank. In the reaction tank 10 shown in FIG. 1, a plurality of inlets 26 are installed on one side of the reaction tank 10 . The inflow port 26 is arranged at a position lower than the interface position of the biological sludge layer formed on the bottom of the reaction tank 10 in the sedimentation process described later, and is opened in the horizontal direction, and the waste water flows through the inflow port 26. is fed horizontally into the biological sludge layer from the Here, the horizontal direction defined in the specification of the present application also includes a substantially horizontal direction. A substantially horizontal direction includes a direction having an inclination angle of 10° or less with respect to the horizontal direction (usually the direction parallel to the direction in which the flat surface of the bottom of the reaction vessel extends).

Although the number of inlets 26 is not particularly limited, it is desirable to have a plurality of inlets 26 in order to improve the diffusibility of waste water. When a plurality of inlets 26 are installed, they are preferably arranged at intervals of, for example, 0.5 m to 5 m from the viewpoint of improving the diffusion of waste water. If the inflow port 26 is opened so as to supply the waste water horizontally into the biological sludge layer, it should be positioned higher than the interfacial position of the biological sludge layer formed on the bottom of the reaction tank 10 in the sedimentation process. may

In addition, the reaction tank 10 of this embodiment is provided with a discharge port 28 for discharging the treated water that has been biologically treated in the reaction tank 10 . In the reaction vessel 10 shown in FIG. 1, an outlet 28 is provided on the side opposite to one side of the reaction vessel 10 where the inlet 26 is provided. The outlet 28 is arranged at the water level of the reaction tank 10 (substantially, the lower end of the outlet 28 is positioned at the water level of the reaction tank 10). In this embodiment, as will be described later, the water level in the reaction tank 10 does not substantially fluctuate because the treated water is discharged together with the inflow of the waste water.

A raw water introduction pipe 12 constituting a raw water introduction device is connected to an inlet 26 from the outside of the reaction tank 10 . A raw water pump 14 and an electromagnetic valve 16 constituting a raw water introduction device are installed in the raw water introduction pipe 12 . The raw water pump 14 and the electromagnetic valve 16 are electrically connected to the controller 24 . The raw water introduction device is not limited to the above device configuration as long as it has a function of supplying waste water to the inlet 26 provided in the reaction tank 10 .

A treated water collection channel 22 shown in FIG.

A blower 18 constituting an air diffuser is connected to an air diffusion pipe 20. The blower 18 sends an aeration gas such as oxygen or air to the air diffusion pipe 20, and the aeration gas is supplied into the reaction tank 10 by the air diffusion pipe 20. be done. Thereby, the water in the reaction tank 10 is fluidized and stirred. Although not shown in the drawings, for example, a stirring device may be installed in the reaction vessel 10 such that a stirring blade rotates with rotation of a motor to stir the water in the reaction vessel 10 . Although the water treatment apparatus 1 shown in FIG. 1 is intended for biological treatment under aerobic conditions, it can also be applied to biological treatment under anaerobic conditions. In the case of processing under anaerobic conditions, an agitator may be installed without installing an air diffuser.

The control device 24 is composed of, for example, a microcomputer composed of a CPU that calculates programs, a ROM and a RAM that store programs and calculation results, and an electronic circuit, and the like, and has a function of controlling the operation of the air diffuser and the raw water introduction device. It has

An example of the operation of the water treatment device 1 of this embodiment will be described below.

The electromagnetic valve 16 is opened by the control device 24 , and the raw water pump 14 is operated so that the waste water passes through the raw water introduction pipe 12 and flows into the reaction tank 10 from the inlet 26 . It is desirable that biological sludge be charged into the reaction tank 10 in advance.

FIG. 2 is a schematic cross-sectional view showing an example of the state of the water treatment apparatus during the biological treatment process. When the water level of the waste water in the reaction tank 10 reaches a predetermined water level, the control device 24 closes the electromagnetic valve 16, stops the operation of the raw water pump 14, and operates the blower 18. As a result, as shown in FIG. 2, the aeration gas is supplied from the air diffusion pipe 20 into the reaction tank 10, and the waste water and biological sludge in the reaction tank 10 are agitated. Then, the wastewater in the reaction tank 10 is biologically treated with biological sludge (biological treatment process), and the substances to be treated (for example, organic matter, etc.) in the wastewater are decomposed.

FIG. 3 is a schematic cross-sectional view showing an example of the state of the water treatment device during the sedimentation process. After the biological treatment process has been carried out for a predetermined period of time, the controller 24 stops the operation of the blower 18 to stop agitation and aeration of the waste water in the reaction tank 10 . As a result, as shown in FIG. 3, the biological sludge is settled (settling process), and a biological sludge layer 30 is formed on the bottom of the reaction tank 10 .

FIG. 4 is a schematic cross-sectional view showing an example of the state of the water treatment device during the inflow/discharge process. After the sedimentation process is carried out for a predetermined time and the biological sludge layer 30 is formed on the bottom of the reaction tank 10, the control device 24 operates the raw water pump 14 and opens the electromagnetic valve 16 to discharge the waste water. It is supplied from the raw water introduction pipe 12 to the inflow port 26 . As a result, as shown in FIG. 4, wastewater is horizontally supplied into the biological sludge layer 30 from the inlet 26, and the biologically treated water that has been biologically treated in the reaction tank 10 is discharged from the outlet 28. It is discharged to catchment channel 22 (inflow/discharge step). Treated water is discharged out of the system of the water treatment apparatus 1 from the treated water collection channel 22 . After performing the inflow/discharge process for a predetermined time, the process returns to the biological treatment process. That is, an operation cycle is performed in which an inflow/discharge process, a biological treatment process, and a sedimentation process are repeated.

Here, it is believed that extracellular matrix (EPS) produced by bacteria influences the formation of highly sedimentary biological sludge (for example, granulated biological sludge) in the operation cycle. In order to form the EPS, it is important to form a concentration gradient of the substance to be treated that is biologically treated within the reaction tank 10 . For example, when biologically treating organic matter in wastewater, it is important to form a concentration gradient of organic matter, and when biologically treating nitrogen-containing substances such as ammonium nitrogen and nitrate nitrogen, It is important to form a concentration gradient of The concentration gradient of the substance to be treated increases the concentration of the substance to be treated in the reaction tank 10 (satiated state) in the inflow/discharge process, and consumes the substance to be treated in the reaction tank 10 in the biological treatment process. , is formed by lowering the concentration of the substance to be treated in the reaction tank 10 (starvation state). In addition, as in the present embodiment, in the inflow/discharge process, by causing the wastewater to flow horizontally from the inflow port 26 into the biological sludge layer 30, it is possible to sufficiently secure a path for the wastewater to come into contact with the biological sludge. Since this becomes possible, the substances to be treated in the waste water tend to remain in the tank. As a result, the concentration of the substance to be treated remaining in the reaction tank 10 can be efficiently increased in the inflow/discharge process, so that the concentration gradient of the substance to be treated in the reaction tank 10 can be increased. . As a result, it becomes possible to form biological sludge with high sedimentation properties, and as a result, it becomes possible to improve the biological treatment rate. When wastewater is supplied into the biological sludge layer 30 in an upward flow (that is, wastewater is supplied vertically into the biological sludge layer 30), the thickness of the biological sludge layer 30 formed in the reaction tank 10 is Unless the sludge is thick enough, it is difficult to secure a sufficient path for the wastewater to come into contact with the biological sludge, making it difficult to efficiently increase the concentration of the substances to be treated remaining in the reaction tank 10. However, in the case of the horizontal inflow of the present embodiment, even if the thickness of the biological sludge layer 30 formed in the reaction tank 10 is thin, compared to the case of the above-mentioned upward flow, the amount of biological sludge in the wastewater is Since a sufficient path for contact with is ensured, the concentration of the substance to be treated remaining in the reaction tank 10 can be increased. In addition, according to the water treatment apparatus 1 of the present embodiment, unlike the conventional water treatment apparatus, it is not necessary to install a distributor at the inflow of wastewater, so the increase in facility costs, operation and management costs, etc. can be suppressed. be. In particular, it is considered that by applying the water treatment apparatus 1 of this embodiment as a water treatment apparatus for large-scale treatment facilities, it is possible to effectively reduce facility costs and operation and management costs.

The highly sedimentary biological sludge formed by the water treatment apparatus 1 of this embodiment may be used for its own biological treatment, or may be taken out from the reaction tank 10 and supplied to another biological treatment tank. Other biological treatment tanks may be of a semi-batch type as in the present embodiment, or may be of a continuous type in which biological treatment is performed while continuously introducing waste water. This makes it possible, for example, to improve the biological treatment rate in other biological treatment tanks. Moreover, you may supply the biologically treated water obtained by the water treatment apparatus 1 of this embodiment to another biological treatment tank (continuous type or semi-batch type). As a result, for example, the quality of biologically treated water can be improved.

The operating conditions, modifications, and the like of the water treatment apparatus of this embodiment will be described below.

The wastewater applied to the water treatment apparatus 1 of the present embodiment is, for example, biodegradable substances (treated This is wastewater, etc. containing the target substance). Examples of biodegradable substances include organic substances, nitrogen-containing substances such as ammonia nitrogen and nitrate nitrogen. For example, when biologically treating wastewater containing organic matter, the organic matter in the wastewater is decomposed into carbon dioxide by contact with biological sludge (microorganisms). Further, for example, when biologically treating wastewater containing nitrogen-containing substances, the nitrogen-containing substances in the wastewater are decomposed into nitrogen gas by contact with biological sludge (microorganisms).

If the wastewater applied to the water treatment apparatus 1 of the present embodiment contains a large amount of oil and fat, it may adversely affect biological treatment. It is preferable to remove fats and oils to, for example, about 150 mg/L or less by an existing technique such as aggregation pressurized floatation or adsorption.

The BOD concentration in the wastewater applied to the water treatment apparatus 1 of this embodiment is not particularly limited. In general, the BOD concentration in wastewater, which makes it difficult to form highly sedimentary biological sludge, is in the range of 50 to 200 mg / L, but according to the water treatment device 1 according to the present embodiment, Even within the above BOD concentration range, it is possible to form biological sludge with high sedimentation properties. In addition, in the water treatment apparatus 1 according to the present embodiment, for example, it is possible to form biological sludge having a sedimentation index SVI30 of 50 mL/g or less and an SVI5 of 70 mL/g or less.

Increasing the concentration of the substance to be treated in the reaction tank 10 in the inflow/discharge process (increasing the concentration of the substance to be treated in the reaction tank 10 at the start of the biological treatment process) is effective for granule formation. In the /discharging step, the residual rate of the substance to be treated in the reaction tank 10 is preferably 50% or more, more preferably 70% or more. Here, the residual ratio of the target substance in the reaction tank 10 indicates the ratio of the concentration of the target substance in the tank after the completion of the inflow/discharge process to the concentration of the target substance in the waste water.

The installation position of the inlet 26 is not particularly limited as long as it is a position lower than the interface position of the biological sludge layer 30 formed on the bottom of the reaction tank 10 in the sedimentation process. Assuming that the effective water depth is 2 m to 8 m and that the interface height of the biological sludge layer 30 is 10% to 50% of the height of the reaction tank 10, the inflow port 26 is at the height of the reaction tank 10. It is preferably installed at a height of 4 m or less from the bottom, more preferably at a height of 2 m or less, and even more preferably at a height of 1 m or less.

The inflow rate of the waste water is preferably in the range of, for example, 10% or more and 100% or less. The inflow rate of waste water is the ratio of the inflow amount of waste water in one cycle of operation to the effective volume in the reaction tank 10 . Here, in order to increase the concentration of the substance to be treated remaining in the reaction tank 10, it is better to set the inflow rate of the waste water as high as possible. There is a concern that the treated water will deteriorate due to a short circuit. Therefore, in view of these factors, it is more preferable that the inflow rate of waste water be in the range of 20% or more and 80% or less. However, as long as a treatment device such as an activated sludge tank is installed in the latter stage of the reaction tank 10 and the water quality of the final treated water after the latter treatment device does not deteriorate, the inflow rate of wastewater is not particularly limited, for example, more than 100%. It is also possible to When the waste water inflow rate exceeds 100%, it is preferable to set the upper limit of the waste water inflow rate to 200% or less in order to suppress a decrease in the number of operation cycles.

The inflow/outflow process time is determined according to, for example, the inflow rate of the waste water and the flow rate of the waste water to the reactor 10 . By the way, when the water area load of the reaction tank 10, which is the value obtained by dividing the flow rate of waste water to the reaction tank 10 by the horizontal cross-sectional area of the reaction tank 10, is set high, the light sludge fraction in the sludge is selectively discharged out of the system. Since it is possible to discharge and leave a highly sedimentary sludge fraction in the tank, the formation of highly sedimentary biological sludge is promoted. , the sludge in the tank will flow out, and there is concern that the biological treatment function will deteriorate. On the other hand, if the water surface load of the reaction tank 10 is set low, the sludge selection effect will be low, and if the inflow rate of the waste water is increased, the inflow/discharge process time will be long, forming sludge with high sedimentation. It is feared that it will become difficult to In view of the above circumstances, the water area load to the reaction tank 10 is preferably 0.5 m/h or more and 20 m/h or less, and preferably in the range of 1 m/h or more and 10 m/h or less. In addition, when it becomes possible to set the water area load of the reaction tank 10 higher due to the improvement of the settling property of the biological sludge in the tank, the water area of the reaction tank 10 can be increased according to the settling property of the biological sludge. It is also possible to increase the load and decrease the time of the filling/discharging process depending on the water area load and the rate of wastewater inflow.

The sludge concentration in the reaction tank 10 in the biological treatment process is preferably in the range of 1,500 to 30,000 mg/L, for example, from the viewpoint of maintaining soundness (sedimentation, activity, etc.) of the sludge. In addition, the sludge load is preferably in the range of 0.05 to 0.60 kg-BOD/kg-MLSS/day in terms of maintaining the soundness of the sludge, etc., and 0.1 to 0.5 kg-BOD/ More preferably, it is in the range of kg-MLSS/day. The biological treatment process time is set, for example, so that the sludge load falls within the above range. When the sludge load is higher than the above range or the sludge concentration is higher than the above range, it is desirable to withdraw biological sludge from the reaction tank 10 .

The pH in the reaction tank 10 is desirably set within a range suitable for common microorganisms, preferably 6 to 9, more preferably 6.5 to 7.5. If the pH value is out of the above range, it is preferable to add an acid or an alkali to adjust the pH so that it falls within the above range. The dissolved oxygen (DO) in the reaction tank 10 is desirably 0.5 mg/L or more, particularly 1 mg/L or more under aerobic conditions.

The time of the sedimentation process is not particularly limited as long as it is the time from the end of the biological treatment process to the formation of the biological sludge layer 30 on the bottom of the reaction tank 10, but the biological sludge layer 30 is formed. The time required for the sludge interface height to reach 10% to 50% of the height of the reaction tank 10 is preferred.

The shape of the reaction vessel 10 is not limited to the rectangular shape shown in FIG. 1, and may be, for example, a cylindrical shape. The rectangular reaction tank 10 is employed in large-scale treatment plants such as sewage treatment plants, for example. An example of a rectangular reaction tank employed in a large-scale treatment plant will be described below.

FIG. 5 is a schematic top view showing an example of a square reaction vessel employed in a large-scale treatment plant. The rectangular reaction vessel 10 shown in FIG. 5 is a rectangular reaction vessel having a pair of opposing long side walls (10a, 10b) and a pair of opposing short side walls (10c, 10d) in a horizontal cross-sectional view. is. A plurality of inlets 26 are provided on one long side wall 10a of the reaction tank 10, and an outlet 28 is provided on the other long side wall 10b of the reaction tank 10. As shown in FIG. A treated water collection channel 22 is provided outside the other long side wall 10 b , and the treated water collection channel 22 communicates with the inside of the reaction vessel 10 through an outlet 28 . Although not shown in the drawings, the outlet 28 is arranged at the water level in the reaction tank 10, and the inlet 26 is lower than the interface position of the biological sludge layer formed at the bottom of the reaction tank 10 in the sedimentation process. placed in position. Then, the waste water is horizontally supplied from the inflow port 26 into the biological sludge layer.

In the case of the reaction tank 10 employed in large-scale treatment plants, the ratio of the horizontal cross-sectional area of the reaction tank 10 to the effective water depth of the reaction tank 10 tends to increase. For a square reaction tank employed in a large-scale treatment plant, for example, [(long side wall length + short side wall length) / effective water depth] is preferably 1 m / m or more, More preferably, it is 1.8 m/m 2 or more. However, in a conventional water treatment apparatus in which waste water flows upward into the reaction tank 10 by a distributor, [(length of long side wall + length of short side wall) / effective water depth] is 1 m / m or more If a reaction tank is used, there is a risk that equipment costs and operation and management costs will increase remarkably in terms of diffusibility of waste water, maintenance of distributors, and the like. On the other hand, in the water treatment apparatus of the present embodiment, when a reaction tank having a [(long side wall length + short side wall length) / effective water depth] of 1 m / m or more is adopted, a distributor is not installed. Therefore, compared with the case of the above-mentioned conventional water treatment apparatus, increases in equipment costs and operation and management costs can be suppressed. Therefore, the water treatment apparatus of this embodiment is particularly suitable as a water treatment apparatus for large-scale treatment facilities.

As for the installation locations of the inlet 26 and the outlet 28, it is preferable to install the inlet 26 on one of the long side walls 10a and install the outlet 28 on the other long side wall 10b. When the inlet 26 is installed on one short side wall 10c and the outlet 28 is installed on the other short side wall 10d, compared to the case where the inlet 26 and the outlet 28 are installed on the long side walls (10a, 10b), As a result, the horizontal distance from the inflow port 26 to the discharge port 28 becomes long, so the contact efficiency between the waste water and the biological sludge layer decreases, which may cause a decrease in the concentration of the substances to be treated remaining in the reaction tank 10. .

The horizontal distance from the inlet 26 to the outlet 28 is preferably, for example, 10 m or less, more preferably 6 m or less, in order to suppress a decrease in the concentration of the substance to be treated remaining in the reaction tank 10 . If the horizontal distance from the inflow port 26 to the discharge port 28 exceeds 10 m, it becomes difficult to bring the waste water into contact with the biological sludge layer efficiently, causing a decrease in the concentration of the substances to be treated remaining in the reaction tank 10. Sometimes.

FIG. 6 is a schematic top view showing another example of a square reaction tank employed in a large-scale treatment plant. The reaction vessel 10 shown in FIG. 6 has a first inlet 26a provided on one side of the reaction vessel 10 and a second inlet 26b provided between the first inlet 26a and the outlet 28. . Both inlets (26a, 26b) are located at a position lower than the interfacial position of the biological sludge layer formed on the bottom of the reaction vessel 10 during the sedimentation process.

FIG. 7(A) is a schematic cross-sectional view showing another example of a square-shaped reaction tank employed in a large-scale treatment plant, and FIG. FIG. 10 is a schematic top view showing another example of a reaction tank having a shape of . The reaction tank 10 shown in FIG. 7 has the first inlet 26a and the second inlet 26b described above. A first treated water collection channel 22a and a second treated water collection channel 22b are installed in the reaction tank 10 . The first treated water collecting channel 22a is installed on the inner side of the side opposite to the one side of the reaction tank 10 where the first inlet 26a is provided, and the second treated water collecting channel 22b is the first treated water collecting channel. 22a and the first inlet 26a. The treated water in the reaction tank 10 shown in FIG. 7 overflows the sidewalls of the first treated water collecting channel 22a and the second treated water collecting channel 22b, and flows into the first treated water collecting channel 22a and the second treated water collecting channel 22b. inside and discharged to the outside of the reaction tank 10 . That is, the first treated water collection channel 22a and the second treated water collection channel 22b shown in FIG. 7 function as the outlet 28 described above.

When the horizontal distance between the inlet provided on one side of the reaction vessel and the outlet provided on the side opposite to the one side is long, the reaction vessel 10 shown in FIGS. Thus, it is preferable to provide one or more inlets and outlets between the inlet provided on one side of the reactor and the outlet provided on the side opposite to the one side. As a result, the contact efficiency between the waste water and the biological sludge layer is increased, so that the concentration of the substances to be treated remaining in the reaction tank tends to increase.

FIG. 10(A) is a cross-sectional view showing another example of the water treatment apparatus of this embodiment, and FIG. 10(B) is a schematic top view showing another example of the water treatment apparatus of this embodiment. . 10(A) and 10(B) omit the air diffusion device including the blower 18 and the air diffusion pipe 20 and the control device 24. As shown in FIG. In FIG. 10, the raw water inlet pipe 12 is introduced into the central portion of the reaction tank 10 and is branched into a plurality of waste water inlets (26a, 26b) within the reaction tank 10. In FIG. The treated water collection channels (22a, 22b) are installed on two sides of the reaction tank 10 facing each other. The spouts of the waste water inlets (26a, 26b) are installed toward the respective treated water collection channels (22a, 22b). In order to increase the residual rate of the substances to be treated during the inflow/discharge process, it is preferable to set the flow velocity at the inflow port, which is calculated from the distance between the inflow port and the side of the reaction vessel opposite to the inflow port, to a certain value or higher. On the other hand, when the distance from the inlet to the opposite side of the reaction vessel is long and it is difficult to keep the flow velocity high, by adopting this embodiment, the distance from the inlet to the outlet can be shortened, Even when the flow velocity at the inflow port is low, it is possible to increase the residual rate of the substances to be treated during the inflow/discharge process.

FIG. 8(A) is a schematic cross-sectional view showing another example of the water treatment apparatus of this embodiment, and FIG. 8(B) is a schematic top view showing another example of the water treatment apparatus of this embodiment. be. It should be noted that FIG. 8B omits the air diffusion device including the blower 18 and the air diffusion pipe 20 and the control device 24 . In the water treatment apparatus 2 shown in FIG. 8, the same reference numerals are assigned to the same components as in the water treatment apparatus 1 shown in FIG. 1, and the description thereof will be omitted. The water treatment device 2 shown in FIG. 8 includes a distribution channel 13 and raw water pipes 15 . The raw water introduction pipe 12 is connected to the upper end of the raw water pipe 15 via the distribution passage 13 . The raw water pipe 15 is a pipe extending vertically, and its upper end is positioned above the water level in the reaction tank 10 and its lower end is connected to the inlet 26 . In this specification, vertically extending piping also includes substantially vertically extending piping. A substantially vertical direction includes directions having an inclination angle of 30° or less with respect to the vertical direction. Note that the raw water pipe 15 may be provided outside the reaction tank 10 .

In the inflow/outflow process of the water treatment device 2 shown in FIG. 8, the electromagnetic valve 16 is opened by the control device 24, and waste water is supplied from the raw water introduction pipe 12 to the raw water pipe 15 via the distribution passage 13. Then, the waste water flows down inside the raw water pipe 15 by gravity and is horizontally supplied from the inflow port 26 into the biological sludge layer formed in the reaction tank 10 . In addition, the biologically treated water in the reaction tank 10 is discharged from the discharge port 28 to the treated water collection channel 22 by the inflow of waste water into the reaction tank 10 . As described above, in the water treatment apparatus 2 shown in FIG. 8, the waste water can flow into the reaction tank 10 by gravity without using a pump, so it is possible to reduce the cost of operation. For example, it is suitable for a sewage treatment plant with a large amount of treated water.

FIG. 9A is a schematic cross-sectional view showing another example of the water treatment apparatus of this embodiment, and FIG. 9B is a schematic top view showing another example of the water treatment apparatus of this embodiment. be. It should be noted that FIG. 9B omits the air diffusion device including the blower 18 and the air diffusion pipe 20 and the control device 24 . In the water treatment apparatus 3 shown in FIG. 9, the same components as those of the water treatment apparatus 1 shown in FIG. A water treatment device 3 shown in FIG. 9 has a distribution channel 13 and a partition wall 17 . The partition wall 17 is erected vertically in the reaction tank 10 and partitions the inside of the reaction tank 10 into a first chamber 10f and a second chamber 10g. Below the partition wall 17, there is provided an opening that communicates the first chamber 10f and the second chamber 10g, and this opening serves as the inflow port 26 described above. The discharge port 28 is provided on the side surface of the second chamber 10g and communicates with the treated water collection channel 22 provided outside the second chamber 10g.

In the reaction tank 10 shown in FIG. 9, the first chamber 10f partitioned by the partition wall 17 is a chamber for receiving waste water, and the second chamber 10g partitioned by the partition wall 17 is the operation cycle (inflow/discharge process, biological This is the room where the treatment process and sedimentation process are performed.

In the inflow/outflow process of the water treatment device 3 shown in FIG. 9, the electromagnetic valve 16 is opened by the control device 24, and waste water is supplied from the raw water introduction pipe 12 through the distribution passage 13 to the first chamber 10f. Then, the waste water passes through the first chamber 10f and is horizontally supplied from the inlet 26 into the biological sludge layer formed on the bottom of the second chamber 10g. In addition, the biologically treated water in the second chamber 10g is discharged from the discharge port 28 to the treated water collection channel 22 by the waste water flowing into the second chamber 10g. After this inflow/discharge process, a biological treatment process and a sedimentation process are performed in the second chamber 10g.

The shape of the opening (inflow port 26) provided in the partition wall 17 is not particularly limited, and may be rectangular, circular, elliptical, or the like. One or more openings (inflow ports 26 ) may be formed in the partition wall 17 .

Although the installation position of the partition wall 17 is not particularly limited, the position of the first chamber 10f in the vertical cross-sectional view of the reaction tank 10 is preferable in that the wastewater can be efficiently brought into contact with the biological sludge layer in the second chamber 10g. The partition wall 17 is preferably installed so that the ratio of the width thereof is 1/2 or less, more preferably 1/5 or less, of the width of the second chamber 10g.

FIG. 11(A) is a schematic cross-sectional view showing another example of the water treatment apparatus of this embodiment, and FIG. 11(B) is a schematic top view showing another example of the water treatment apparatus of this embodiment. be. In addition, in FIG. 11(B), the air diffusion device including the blower 18 and the air diffusion pipe 20 and the control device 24 are omitted. In the water treatment device 4 shown in FIG. 11, the same reference numerals are assigned to the same components as in the water treatment device 1 shown in FIG. 1, and the description thereof will be omitted. The reaction vessel 10 shown in FIG. 11 is a rectangular reaction vessel having a pair of opposing walls (10a, 10b) and a pair of opposing walls (10c, 10d) in a horizontal sectional view. A plurality of inlets 26 and an outlet 28 are provided on one long side wall 10a of the reaction tank 10 . The outlet 28 is arranged at the water level in the reaction tank 10, and the inlet 26 is arranged at a position lower than the interface position of the biological sludge layer formed at the bottom of the reaction tank 10 in the sedimentation process. Wastewater is then fed horizontally from the inlet 26 into the biological sludge tank. Since the inflow port 26 and the discharge port 28 are installed on the same wall surface, when the wastewater ejected from the inflow port 26 into the deposited sludge with a flow rate of more than a certain level reaches the wall surface on the opposite side of the inflow port. In addition, since the material does not rise toward the outlet as an upward flow, it is possible to prevent short-passing of the material to be treated.

FIG. 12(A) is a schematic cross-sectional view showing another example of the water treatment apparatus of this embodiment, and FIG. 12(B) is a schematic top view showing another example of the water treatment apparatus of this embodiment. be. In addition, in FIG. 12(B), the air diffusion device including the blower 18 and the air diffusion pipe 20 and the control device 24 are omitted. In the water treatment apparatus 5 shown in FIG. 12, the same components as those of the water treatment apparatus 1 shown in FIG. A water treatment device 5 shown in FIG. 12 includes a distribution channel 13 and raw water pipes 15 . The raw water introduction pipe 12 is connected to the upper end of the raw water pipe 15 via the distribution passage 13 . The raw water pipe 15 is a pipe extending vertically, and its upper end is positioned above the water level in the reaction tank 10 and its lower end is connected to the inlet 26 . In this specification, vertically extending piping also includes substantially vertically extending piping. A substantially vertical direction includes directions having an inclination angle of 30° or less with respect to the vertical direction. Note that the raw water pipe 15 may be provided outside the reaction tank 10 . Also in the water treatment device 5, the inflow port 26 and the discharge port 28 are installed on the same wall surface as in the water treatment device 4 described above.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples.

(Example 1)
Using the reactor shown in FIG. 9, the following tests were conducted. As a reaction tank, a reaction tank having a length of 146 mm (L), a width of 208 mm (W), a height of 300 mm (effective water depth of 200 mm (H)) and an effective volume of 6.1 L was used. A partition was installed at a position 25 mm away from one side of the reaction tank, and an inlet (opening) was provided at the lower end of the partition. An outlet was provided on one side and the opposite side of the reactor. The position of the outlet was set at the water level in the reactor.

A sodium bromide solution (40 mgBr/L) was used as waste water used in the test. Wastewater and activated sludge were put into the second chamber of the reaction tank and aerated and stirred for a predetermined time (biological treatment process). After the biological treatment step, the reaction tank was allowed to stand for a predetermined time (sedimentation step). After the sedimentation process, wastewater was supplied to the first chamber, and while the wastewater was supplied horizontally from the inlet into the biological sludge layer in the second chamber, the biologically treated water in the second chamber was discharged from the outlet (inflow / discharge process). The flow rate of the waste water was 0.6 m/h as the water area load, and the inflow/discharge process time was 32 minutes (150% of the water tank effective volume as the waste water inflow rate).

The bromide ion concentration in the reaction tank after the inflow/discharge process was measured, and the bromide ion residual rate in the reaction tank at the end of the inflow/discharge process was evaluated by the following formula. Table 1 shows the results. Bromine ions are substances that are not easily affected by adsorption to biological sludge and biological reactions. can be said to be high.
Bromine ion residual ratio = (bromine ion concentration in reaction tank/hydrogen ion concentration in wastewater) x 100

(Comparative example 1)
A reaction vessel similar to that of Example 1 was used, except that a current plate was installed in the second chamber of the reaction vessel. The straightening plate is a rectangular plate (120 mm×208 mm) of 250 cm ² , and a plurality of holes with a diameter of 4 mm are formed in the whole plate. The rectifying plate was installed horizontally at a height of 6 mm from the bottom of the second chamber (a position higher than the inlet of the partition wall). That is, the waste water (sodium bromide solution) flows into the lower side of the rectifying plate of the second chamber through the inlet, and then is supplied upward through the holes of the rectifying plate. Furthermore, since the biological sludge layer formed by the sedimentation process is formed on the rectifying plate, waste water is supplied upward into the biological sludge layer through the holes.

Similarly, in Comparative Example 1, the bromide ion concentration in the reaction tank after the inflow/discharge process was measured, and the bromide ion residual rate in the reaction tank at the end of the inflow/discharge process was evaluated. Table 1 shows the results.

In Comparative Example 1, the bromide ion residual rate was 70%, whereas in Example 1, the bromide ion residual rate was improved to 82%. From the above, it can be seen that the example in which the wastewater is fed horizontally from the inlet into the biological treatment tank on the bottom of the reaction tank has a higher inflow/discharge process than the comparative example in which the wastewater is supplied in an upward flow into the biological treatment tank. , it can be said that the concentration of the substance to be treated remaining in the reaction tank can be increased to the same or higher efficiency.

(Example 2 and Example 3)
Using the reactor shown in FIG. 8, the following tests were conducted. As a reaction tank, a reaction tank having a length of 438 mm (L), a width of 125 mm (W), a height of 750 mm (effective water depth of 600 mm), and an effective volume of 33 L was used. An inlet was provided at the bottom of the side surface of the reactor (125×750 surface). However, in Example 2, the outlet was provided on the side opposite to the side on which the inlet was provided, and in Example 3, the outlet was provided on the same side as the side on which the inlet was provided. The position of the outlet in Examples 2 and 3 was set at the water level in the reactor.

A sodium bromide solution (40 mgBr/L) was used as the waste water used in the test. Waste water and activated sludge were put into the reaction tank and aerated and stirred for a predetermined time (biological treatment process). After the biological treatment step, the reaction tank was allowed to stand for a predetermined time (sedimentation step). After the sedimentation process, waste water was supplied through the waste water inlet so as to hit the settled sludge in the horizontal direction, and the biologically treated water in the reaction tank was discharged from the outlet (inflow/discharge process). At that time, the flow rate of the waste water at the inlet was varied within the range of the conditions shown in Table 2, and supplied. The amount supplied was 100% of the effective volume of the reactor. N in the table is the horizontal distance N (m) from the inlet to the side of the reactor facing the inlet.

The bromide ion concentration in the reaction tank after the inflow/discharge process was measured, and the bromide ion residual rate in the reaction tank at the end of the inflow/discharge process was evaluated by the above formula. The results are shown in FIG.

FIG. 13 is a diagram showing the results of the bromide ion residual rate versus the flow velocity at the inlet in Examples 2 and 3. FIG. As shown in FIG. 13, the residual ratio of bromide ions was 50% or more under any condition. Among the implemented conditions, the highest residual rate was obtained under the condition that the flow velocity at the inlet was 37.8 cm/sec. From the above, in the range of [N ^1/2 × 20] ≤ v ≤ [N ^1/2 × 80] as the flow velocity v at the inlet, the residual rate of the target substance in the wastewater in the inflow/discharge process is 50%. It was confirmed that the above was the case. In addition, when the inlet and outlet were placed on the same and opposite sides of the reaction tank, the bromide ion residual rate was higher when both were installed on the same side. It has been confirmed that it is preferable that the outlet and the outlet are installed on the same side.

(Example 4)
Next, a test was conducted using the reactor shown in FIG. A reaction tank having a length of 3 m, a width of 1 m, an effective water depth of 5 m, and an effective volume of 15 m ³ was used. An inlet was installed at the bottom of the side of the reactor, and an outlet was installed on the same side as the side on which the inlet was installed. In addition, the position of the outlet was set at the water surface position in the reaction tank. The test method was the same as in Example 3, except that the flow velocity conditions at the inlet were set to the conditions shown in Table 3.

The bromide ion residual rate was 91% under condition 7, 76% under condition 8, and 86% under condition 9, all of which were 70% or more.

(Example 5)
Using the reactor shown in FIG. 8, the following granule forming test was conducted. As a reaction tank, a reaction tank having a length of 220 mm (L), a width of 125 mm (W), a height of 400 mm (effective water depth of 300 mm), and an effective volume of 33 L was used. An inlet was provided at the bottom of the reactor side surface (125×220 surface). An outlet was provided on the side opposite to the side on which the inlet was provided. The position of the outlet was set at the water level in the reactor. N in this reactor was 0.22 m.

The operation process was an operation in which the inflow/discharge process, the aeration process, and the sedimentation process were repeated. Activated sludge from a sewage treatment plant was put into the reaction tank as the initial sludge, and the change in the properties of the sludge in the reaction tank was investigated. Simulated sewage containing bonito extract and peptone as main components was used as the influent, and BOD was set to 100 mg/L. In the inflow/discharge process, the simulated sewage was inflowed from the inlet installed on the side of the reaction tank so as to come into contact with the sludge, and the flow velocity at the inlet was in the range of 11-28 cm / sec (v / N ^1/2 values range from 23.5 to 60). The amount of wastewater inflow in one inflow/outflow process was 100% of the effective volume of the reactor.

FIG. 14 shows changes in SVI5 and SVI30, which are sedimentation indices of sludge in the reaction tank. SVI5 is a sedimentation index of biological sludge, and is obtained by the following. First, 1 L of sludge is put into a 1 L graduated cylinder, stirred, and then left to stand for 5 minutes or 30 minutes, and the sludge interface is measured. Then, the volume ratio (%) occupied by the sludge in the graduated cylinder is calculated. Next, the MLSS (mg/L) of the sludge is measured. These are applied to the following formula to calculate SVI5 or SVI30. The smaller the value of SVI5 or SVI30, the higher the settling property of the sludge.
SVI (mL/g) = volume ratio of sludge x 10,000/MLSS

As shown in FIG. 14, no change was observed in SVI during the initial 15 days after starting, and both SVI5 and SVI30 remained at 300-350 mL/g. After that, a rapid decrease in SVI was confirmed, and formation of sludge having a good settling property of 20 mL/g was confirmed for both SVI5 and SVI30 35 days after start-up.

FIG. 15 shows the input sludge and the sludge observation photograph 50 days after start-up. All bars indicate 500 μm. As shown in FIG. 15, the input sludge consisted of dispersed sludge, while the sludge after 50 days consisted of good granular sludge of about 200-300 μm.

1 to 5 water treatment equipment, 10 reaction tank, 10a, 10b long side wall, 10c, 10d short side wall, 10f first chamber, 10g second chamber, 12 raw water introduction pipe, 13 distribution path, 14 raw water pump, 15 raw water Piping, 16 electromagnetic valve, 17 partition, 18 blower, 20 air diffuser, 22 treated water collecting channel, 24 control device, 26 inlet, 28 outlet, 30 biological sludge layer.

Claims (14)

A water treatment method for biologically treating wastewater using a reaction tank containing biological sludge in a tank provided with an inlet and an outlet,
an inflow/discharge step of discharging the biologically treated water in the reaction tank from the outlet while flowing the waste water into the reaction tank from the inlet; and biologically treating the waste water in the reaction tank with biological sludge. and an operation cycle step of repeating a biological treatment step and a sedimentation step of sedimenting the biological sludge in the reaction tank,
The outlet is arranged at a water level in the reaction tank,
A plurality of the inlets are provided in the reaction vessel, and at least part of the waste water is horizontally supplied into the biological sludge layer formed at the bottom of the reaction vessel in the sedimentation step , and A water treatment method , wherein the direction of the discharged wastewater is not opposite . A water treatment method for biologically treating wastewater using a reaction tank containing biological sludge in a tank provided with an inlet and an outlet,
an inflow/discharge step of discharging the biologically treated water in the reaction tank from the outlet while flowing the waste water into the reaction tank from the inlet; and biologically treating the waste water in the reaction tank with biological sludge. and an operation cycle step of repeating a biological treatment step and a sedimentation step of sedimenting the biological sludge in the reaction tank,
The outlet is arranged at a water level in the reaction tank,
the inlet horizontally supplies at least part of the waste water into the biological sludge layer formed at the bottom of the reaction tank in the sedimentation step;
Water treatment characterized in that the water area load of the reaction tank, which is the value obtained by dividing the flow rate of the waste water to the reaction tank by the horizontal cross-sectional area of the reaction tank, is 0.5 m / h or more and 20 m / h or less. Method. 3. The water treatment method according to claim 1 , wherein the inflow port is located at a position lower than the interface position of the biological sludge layer formed at the bottom of the reaction tank in the sedimentation step. A pipe extending in a vertical direction is connected to the inlet,
4. The water treatment method according to any one of claims 1 to 3, wherein the waste water is supplied to the inflow port by gravity from the pipe. The inside of the reaction vessel is partitioned by a partition wall into a first chamber into which the waste water is introduced and a second chamber in which the operation cycle process is performed,
The outlet is provided on the second chamber side and is arranged at the water level in the second chamber,
The inlet is provided in the partition wall so that the first chamber and the second chamber communicate with each other, and is positioned lower than the interface level of the biological sludge layer formed on the bottom of the second chamber in the sedimentation step. 4. The water treatment method according to any one of claims 1 to 3, wherein the waste water is horizontally supplied into the biological sludge layer formed at the bottom of the second chamber. The water treatment according to any one of claims 1 to 4 , wherein the reaction tank is a square water tank, and the inlet and the outlet are provided on the same side of the square water tank. Method. The flow velocity v (cm/sec) of the waste water at the inlet and the horizontal distance N (m) from the inlet to the side of the reaction vessel facing the inlet satisfy the following equation. The water treatment method according to any one of claims 1 to 6 .
20≦v/N ^1/2 ≦80 Equipped with a reaction tank containing biological sludge in a tank with an inlet and an outlet,
an inflow/discharge step of discharging biologically treated water in the reaction tank from the outlet while flowing waste water into the reaction tank from the inlet; and biologically treating the waste water in the reaction tank with biological sludge. A water treatment apparatus that performs an operation cycle process that repeats a biological treatment process and a sedimentation process for sedimenting the biological sludge in the reaction tank,
The outlet is installed at a water level in the reaction tank,
A plurality of the inlets are provided in the reaction tank, and at least a part of the waste water is horizontally supplied into the biological sludge layer formed at the bottom of the reaction tank in the sedimentation step , and from each outlet A water treatment apparatus , wherein the directions of the discharged wastewater are not opposite to each other . Equipped with a reaction tank containing biological sludge in a tank with an inlet and an outlet,
an inflow/discharge step of discharging biologically treated water in the reaction tank from the outlet while flowing waste water into the reaction tank from the inlet; and biologically treating the waste water in the reaction tank with biological sludge. A water treatment apparatus that performs an operation cycle process that repeats a biological treatment process and a sedimentation process for sedimenting the biological sludge in the reaction tank,
The outlet is installed at a water level in the reaction tank,
the inlet horizontally supplies at least part of the waste water into the biological sludge layer formed at the bottom of the reaction tank in the sedimentation step;
Water treatment characterized in that the water area load of the reaction tank, which is the value obtained by dividing the flow rate of the waste water to the reaction tank by the horizontal cross-sectional area of the reaction tank, is 0.5 m / h or more and 20 m / h or less. Device. 10. The water treatment apparatus according to claim 9 , wherein the inlet is located at a position lower than the interface position of the biological sludge layer formed on the bottom of the reaction tank in the sedimentation step. Equipped with vertically extending piping,
11. The water treatment apparatus according to claim 9, wherein the pipe is connected to the inlet, and the waste water is supplied to the inlet from the pipe by gravity. The reaction tank has a partition wall that divides the inside of the tank into a first chamber into which the waste water is introduced and a second chamber in which the operation cycle process is performed,
The outlet is provided on the second chamber side and is arranged at the water level in the second chamber,
The inlet is provided in the partition wall so that the first chamber and the second chamber communicate with each other, and is positioned lower than the interface level of the biological sludge layer formed on the bottom of the second chamber in the sedimentation step. 11. The water treatment apparatus according to claim 9 or 10, wherein the waste water is horizontally supplied into the biological sludge layer formed at the bottom of the second chamber. The water treatment according to any one of claims 9 to 11 , wherein the reaction tank is a square water tank, and the inlet and the outlet are provided on the same surface of the square water tank. Device. The flow velocity v (cm/sec) of the waste water at the inlet and the horizontal distance N (m) from the inlet to the side of the reaction vessel facing the inlet satisfy the following equation. The water treatment device according to any one of claims 9-13 .
20≦v/N ^1/2 ≦80

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