WO2020026924A1 - Water treatment method and water treatment device - Google Patents

Abstract

The present embodiment pertains to a water treatment method that uses a reaction tank (10) and which involves repeatedly performing an operation cycle comprising: an inflow step for causing an inflow of waste water; a biological treatment step for subjecting the waste water to biological treatment using biological sludge; a sedimentation step for causing the biological sludge to settle; and a drainage step for draining biologically-treated water that has undergone the aforementioned biological treatment. The reaction tank (10) is provided with an inflow port (12) that is disposed at a position lower than an interface position of a biological sludge layer formed at the bottom of the reaction tank (10) in the sedimentation step, and an inflow pipe (14) that extends upward in the vertical direction from the inflow port (12). In the inflow step, the waste water is caused to gravitationally flow down in the inflow pipe (14) so as to be fed into the biological sludge layer from the inflow port (12).

Description

Water treatment method and water treatment device

The present invention relates to a technology of a water treatment method and a water treatment device.

活性 Conventionally, an activated sludge method utilizing an aggregate of microorganisms (aerobic biological sludge) called floc is used for biological wastewater treatment. However, in the activated sludge method, when the floc (aerobic biological sludge) and the treated water are separated in the sedimentation basin, the surface area of the sedimentation basin must be very large because the sedimentation speed of the floc is slow. In addition, the processing speed of the activated sludge method depends on the sludge concentration in the biological treatment tank, and the processing speed can be increased by increasing the sludge concentration. However, solid-liquid separation failure such as bulking occurs. May not be able to maintain the processing.

On the other hand, in the treatment of anaerobic organisms, it is common to utilize granular aggregates of microorganisms called granules. Granules have a very high sedimentation velocity and microorganisms are densely gathered, so that the sludge concentration in the biological treatment tank can be increased, and high-speed treatment of wastewater can be realized. However, the anaerobic biological treatment has problems such as the limited number of wastewater to be treated and the necessity of maintaining the temperature of the treated water at 30 to 35 ° C. as compared with the aerobic treatment (activated sludge method, etc.). In some cases. In addition, the anaerobic biological treatment alone has poor water quality, and when 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 is clear that by using a semi-batch treatment device that intermittently flows wastewater into a reaction tank, not only anaerobic biological sludge but also aerobic biological sludge can form highly sedimentable granulated biological sludge. (For example, see Patent Documents 1 to 4). The granulated biological sludge has, for example, an average particle size of 0.2 mm or more and a sedimentation speed of 5 m / h or more. In the semi-batch type biological treatment, one reaction tank has four functions such as (1) inflow of wastewater, (2) biological treatment of a substance to be treated, (3) sedimentation of biological sludge, and (4) discharge of treated water. Generally, the steps are repeated.

In addition, Patent Document 5 discloses a semi-batch type that repeats three steps of (1) inflow of wastewater and discharge of treated water, (2) biological treatment of a substance to be treated, and (3) sedimentation of biological sludge. A biological treatment method is disclosed.

WO 2004/024638 JP 2008-212878 A Japanese Patent No. 4975541 Japanese Patent No. 4804888 JP 2016-77931 A

By the way, in the inflow step of wastewater in the semi-batch type biological treatment, it is common to supply wastewater from the lower part of the tank using a pump. A new method for inflow of wastewater is desired.

Therefore, an object of the present invention is to provide a water treatment method and a water treatment apparatus that can flow wastewater into a reaction tank with a simple configuration without using a pump.

(1) In the present embodiment, an inflow step of inflowing wastewater, a biological treatment step of biologically treating the wastewater with biological sludge, a sedimentation step of sedimentation of the biological sludge, and discharging the biologically treated water subjected to the biological treatment. A water treatment method using a reaction tank that repeatedly performs an operation cycle having a discharging step, wherein the reaction tank has a position lower than an interface position of a biological sludge layer formed at the bottom of the reaction tank in the settling step. Are provided, and an inflow portion extending vertically upward from the inflow port is provided. In the inflow step, the wastewater is caused to flow down in the inflow portion by gravity, and the biological sludge is discharged from the inflow port. This is a method for treating water supplied to the bed.

(2) In the water treatment method according to the above (1), it is preferable that in the operation cycle, the discharge step is performed while the inflow step is performed.

(3) In the water treatment method according to the above (1) or (2), the biological sludge in the reaction tank is supplied to a continuous biological treatment tank that performs biological treatment with biological sludge while continuously flowing wastewater. It is preferable to include at least one of a sludge supply step and a treated water supply step of supplying treated biological water in the reaction tank.

(4) In the water treatment method according to any one of (1) to (3), in the inflow step, the wastewater is caused to flow down in the inflow section by gravity, and the biological sludge layer is discharged from the inflow port. It is preferable to feed in the horizontal direction or below the horizontal direction.

(5) In the water treatment method according to the above (1), in the operation cycle, the discharge step is performed while the inflow step is performed, and the reaction tank is disposed at a water level in the reaction tank. Preferably, an outlet is provided, and the inflow port supplies at least a part of the wastewater horizontally into the biological sludge layer.

(6) In the water treatment method according to the above (5), the inside of the reaction tank is partitioned by a partition into a first chamber into which the wastewater is introduced and a second chamber for performing the operation cycle step. The outlet is provided on the second chamber side, and is disposed at a water level in the second chamber, and the inflow port is provided on the partition wall such that the first chamber and the second chamber communicate with each other. And it is arrange | positioned at the position lower than the interface position of the biological sludge layer formed in the said 2nd chamber bottom part in the said settling process, and supplies the said wastewater in the horizontal direction into the biological sludge layer formed in the said 2nd chamber bottom part. Is preferred.

(7) In the water treatment method according to the above (5) or (6), the reaction tank is a square water tank, and the inflow port and the discharge port are provided on the same surface of the square water tank. Is preferred.

(8) In the water treatment method according to any one of the above (5) to (7), a flow rate v (cm / sec) of drainage water at the inlet and a reaction from the inlet to the inlet. It is preferable that the horizontal distance N (m) to the side surface of the tank satisfies the following expression.
20 ≦ v / N ^1/2 ≦ 80

(9) In the present embodiment, an inflow step of inflowing wastewater, a biological treatment step of biologically treating the wastewater with biological sludge, a sedimentation step of sedimentation of the biological sludge, and discharging the biologically treated biologically treated water. A water treatment apparatus provided with a reaction tank that repeatedly performs an operation cycle having a discharging step, wherein the reaction tank has a position lower than an interface position of a biological sludge layer formed at the bottom of the reaction tank in the settling step. Are provided, and an inflow portion extending vertically upward from the inflow port is provided. In the inflow step, the wastewater is caused to flow down in the inflow portion by gravity, and the biological sludge is discharged from the inflow port. It is a water treatment device that feeds into the bed.

(10) In the water treatment apparatus according to the above (9), it is preferable that in the operation cycle, the discharge step is performed while the inflow step is performed.

(11) In the water treatment apparatus according to the above (9) or (10), the biological sludge in the reaction tank is supplied to a continuous biological treatment tank that performs biological treatment with biological sludge while continuously flowing wastewater. It is preferable to include at least one of a sludge supply unit and a treated water supply unit that supplies treated biological water in the reaction tank.

(12) In the water treatment apparatus according to any one of the above (9) to (11), it is preferable that the inflow port opens in a horizontal direction or a lower direction than the horizontal direction.

(13) In the water treatment apparatus according to the above (9), in the operation cycle, the discharging step is performed while the inflow step is performed, and the reaction tank is disposed at a water level in the reaction tank. Preferably, an outlet is provided, and the inflow port supplies at least a part of the wastewater horizontally into the biological sludge layer.

(14) In the water treatment apparatus according to (13), the reaction tank includes a partition for partitioning the inside of the tank into a first chamber into which the wastewater is introduced and a second chamber for performing the operation cycle process. , The discharge port is provided on the second chamber side, and is disposed at a water surface level in the second chamber, and the inflow port is connected to the partition wall such that the first chamber and the second chamber communicate with each other. And disposed at a position lower than the interface of the biological sludge layer formed at the bottom of the second chamber in the sedimentation step, and the wastewater is disposed horizontally in the biological sludge layer formed at the bottom of the second chamber. Preferably.

(15) In the water treatment device according to the above (13) or (14), the reaction tank is a square water tank, and the inflow port and the discharge port are provided on the same surface of the square water tank. Is preferred.

(16) In the water treatment apparatus according to any one of the above (13) to (15), a flow rate v (cm / sec) of drainage water at the inlet, and a reaction from the inlet to the inlet. It is preferable that the horizontal distance N (m) to the side surface of the tank satisfies the following expression.
20 ≦ v / N ^1/2 ≦ 80

According to the present invention, it is possible to provide a water treatment method and a water treatment apparatus capable of flowing wastewater into a reaction tank with a simple configuration without using a pump.

It is a schematic cross section showing an example of a water treatment device concerning this embodiment. (A)-(C) is a schematic top view of a reaction tank for explaining the example of arrangement of an inflow pipe. It is a schematic cross section which shows an example of the state of the water treatment apparatus at the time of an inflow process. 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. It is a schematic cross section which shows an example of the state of the water treatment apparatus at the time of a sedimentation process. It is a schematic cross section which shows an example of the state of the water treatment apparatus at the time of a discharge process. It is a schematic cross section which shows another example of the water treatment apparatus which concerns on this embodiment. It is a schematic cross section which shows another example of the water treatment apparatus of this embodiment. It is a schematic cross section which shows another example of the water treatment apparatus of this embodiment. It is a schematic cross section which shows another example of the water treatment apparatus of this embodiment. It is a schematic cross section which shows another example of the water treatment apparatus of this embodiment. It is a schematic cross section which shows 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. It is a schematic structure figure showing other examples of the water treatment equipment of this embodiment. (A) is a schematic sectional view showing an example of a water treatment device according to the present embodiment, and (B) is a schematic top view showing an example of the water treatment device according to the present 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. It is a schematic cross section which shows an example of the state of the water treatment apparatus at the time of a sedimentation process. It is a schematic cross section which shows an example of the state of the water treatment apparatus at the time of an inflow / discharge process. It is a schematic top view which shows an example of the square-shaped reaction tank employ | adopted in a large-scale processing plant. It is a schematic top view which shows another example of the square-shaped reaction tank employ | adopted in a large-scale processing plant. (A) is a schematic cross-sectional view showing another example of a square-shaped reaction tank used in a large-scale processing plant, and (B) is a square-shaped reaction tank used in a large-scale processing plant. It is a schematic top view which shows 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 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 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. It is a figure which shows the result of the bromine ion residual rate with respect to the flow velocity of the inflow port in Examples 2 and 3. It is a figure which shows transition of SVI5 and SVI30 which are the sedimentation indexes of reaction tank sludge. It is an input sludge and a sludge observation photograph 50 days after startup.

(4) An embodiment of the present invention will be described below. The present embodiment is an example for implementing the present invention, and the present invention is not limited to the present embodiment.

FIG. 1 is a schematic sectional view showing an example of the water treatment apparatus according to the present embodiment. As shown in FIG. 1, the water treatment apparatus 1 includes a reaction tank 10, a diffuser including a blower 18 and a diffuser 20, a treated water discharge pipe 22, and a controller 24.

The reaction tank 10 is provided with an inlet 12 and an inflow pipe 14 through which wastewater flows into the tank. The inflow pipe 14 is an inflow portion extending vertically upward from the inflow port 12. In this specification, the inflow portion extending in the vertical direction includes the inflow portion extending in the substantially vertical direction. The substantially vertical direction includes a direction having an inclination angle of 45 ° or less with respect to the vertical direction. An electromagnetic valve 14 a is installed in the inflow pipe 14, and the electromagnetic valve 14 a is electrically connected to the control device 24.

The inlet 12 is disposed 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 step described later. The inflow port 12 shown in FIG. 1 is provided at the lower end of the inflow pipe 14 and opens in the horizontal direction.

FIGS. 2A to 2C are schematic top views of a reaction tank for explaining an example of arrangement of the inflow pipes. The number of the inflow pipes 14 provided with the inflow ports 12 is not particularly limited. Taking a rectangular reactor as an example, the inflow pipe 14 provided with the inflow port 12 is, for example, at least two locations on the diagonal of the reactor 10 as shown in FIG. 2C, or at least one of at least two locations on the same side of the reaction tank as shown in FIG. 2C. desirable.

反 応 Further, the reaction tank 10 is provided with an outlet 16 for discharging treated water biologically treated in the reaction tank 10. A treated water discharge pipe 22 is connected to the discharge port 16. An electromagnetic valve 22 a is installed in the treated water discharge pipe 22, and the electromagnetic valve 22 a is electrically connected to the control device 24.

The blower 18 constituting the air diffuser is connected to the air diffuser 20, and an aerated gas such as oxygen or air is sent to the air diffuser 20 by the blower 18, and the aerated gas is supplied into the reaction tank 10 by the air diffuser 20. Is done. Thereby, the water in the reaction tank 10 flows and is stirred. Although not described in the drawings, for example, a stirring device in which the stirring blades rotate with the rotation of the motor may be installed in the reaction tank 10 to stir the water in the reaction tank 10. The water treatment apparatus 1 shown in FIG. 1 is intended for biological treatment under aerobic conditions, but is also applicable to biological treatment under anaerobic conditions. When processing is performed under anaerobic conditions, a stirring device may be installed without installing a diffuser.

The control device 24 includes, for example, a microcomputer configured with a CPU for calculating a program, a ROM and a RAM for storing the program and the calculation result, and an electronic circuit, and has a function of controlling the opening and closing of the air diffuser and the electromagnetic valve. Have

例 Hereinafter, an example of the operation of the water treatment apparatus 1 of the present embodiment will be described.

FIG. 3 is a schematic cross-sectional view showing an example of the state of the water treatment device during the inflow step. The electromagnetic valve 14 a is opened by the control device 24, and the wastewater flows down the inflow pipe 14 by gravity and is supplied into the reaction tank 10 from the inflow port 12. The inflow port 12 is disposed at a position lower than the interface position of the biological sludge layer 30 formed in the sedimentation step described later, and is open in the horizontal direction. Therefore, as shown in FIG. It is supplied horizontally into the biological sludge layer 30.

FIG. 4 is a schematic cross-sectional view showing an example of the state of the water treatment device during the biological treatment step. When the water level of the waste water in the reaction tank 10 reaches a predetermined water level in the inflow step, the control device 24 closes the electromagnetic valve 14a and operates the blower 18. Thereby, as shown in FIG. 4, aeration gas is supplied into the reaction tank 10 from the air diffuser 20, and the wastewater and biological sludge in the reaction tank 10 are stirred. Then, the wastewater in the reaction tank 10 is biologically treated with biological sludge (biological treatment step), and the substances to be treated (eg, organic substances) in the wastewater are decomposed.

FIG. 5 is a schematic cross-sectional view showing an example of a state of the water treatment device during the settling process. After performing the biological treatment step for a predetermined time, the operation of the blower 18 is stopped by the control device 24, and the stirring and aeration of the wastewater in the reaction tank 10 are stopped. Thereby, as shown in FIG. 5, the settling of the biological sludge is performed (sedimentation step), and the biological sludge layer 30 is formed on the bottom of the reaction tank 10.

FIG. 6 is a schematic cross-sectional view showing an example of the state of the water treatment apparatus during the discharging step. After the settling process is performed for a predetermined time and the biological sludge layer 30 is formed on the bottom of the reaction tank 10, the electromagnetic valve 22a is opened by the control device 24, and as shown in FIG. Is discharged from the discharge port 16 to the treated water discharge pipe 22 (discharge step). The treated water is discharged from the treated water discharge pipe 22 to the outside of the water treatment apparatus 1. Then, after performing the discharge step for a predetermined time, the flow returns to the above-described inflow step.

As described above, in the water treatment apparatus 1 shown in FIG. 1, the operation cycle of repeating the four steps of the inflow step, the biological treatment step, the sedimentation step, and the discharge step is performed. 10 is flowing. That is, in the water treatment apparatus 1 shown in FIG. 1, the drainage can be flowed in by a simple configuration without using a pump, so that an increase in running costs such as facility costs and operation management costs can be suppressed. In particular, it is considered that by applying the water treatment apparatus 1 of the present embodiment as a water treatment apparatus for a large-scale treatment facility, facility costs and operation management costs can be effectively reduced.

Here, it is considered that extracellular matrix (EPS) produced by bacteria influences the formation of highly sedimentable biological sludge (eg, granulated biological sludge) in the operation cycle. In order to form EPS, it is important to form a concentration gradient of the substance to be treated that is biologically treated in 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 a nitrogen-containing substance such as ammonia nitrogen or nitrate nitrogen, a nitrogen-containing substance is required. It is important to form a concentration gradient. The concentration gradient of the substance to be treated is such that, for example, in the inflow step, the concentration of the substance to be treated in the reaction tank 10 is increased (saturated state), and in the biological treatment step, the substance to be treated in the reaction tank 10 is consumed. Is formed by lowering the concentration of the substance to be treated in the reaction tank 10 (starved state). In the present embodiment, in the inflow step, the wastewater is supplied from the inflow port 12 into the biological sludge layer 30, so that the wastewater can be brought into contact with the biological sludge in an anaerobic state. Accordingly, in the present embodiment, in the inflow step, unnecessary consumption of the treatment target substance in the wastewater is suppressed, and the concentration of the treatment target substance remaining in the reaction tank 10 can be efficiently increased. Therefore, 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 having high sedimentation, and it is possible to improve the biological treatment speed.

運 転 The operating conditions and modified examples of the water treatment apparatus of the present embodiment will be described below.

The wastewater applied to the water treatment apparatus 1 of the present embodiment is, for example, a biodegradable substance such as food processing factory wastewater, chemical factory wastewater, semiconductor factory wastewater, machine factory wastewater, sewage, human waste, or river water. Wastewater containing the target substance). The substance having biodegradability is, for example, an organic substance, a nitrogen-containing substance such as ammoniacal nitrogen, nitrate nitrogen, or the like. 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). In addition, for example, when biologically treating wastewater containing a nitrogen-containing substance, the nitrogen-containing substance in the wastewater is decomposed into nitrogen gas by contact with biological sludge (microorganisms).

If the wastewater applied to the water treatment apparatus 1 according to the present embodiment contains a large amount of fats and oils, the biological treatment may be adversely affected. It is preferable to remove oils and fats to about 150 mg / L or less, for example, by an existing method such as coagulation pressure flotation and adsorption.

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

The flow rate at the inlet 12 in the inflow step is appropriately set depending on the structure, size, and the like of the reaction tank 10, and is not particularly limited. For example, the flow rate is 1 cm / sec or more and 200 cm / sec or less. Preferably, it is 10 cm / sec or more and 100 cm / sec or less. If the flow rate at the inflow port 12 is less than 1 cm / sec, the concentration of the substance to be treated remaining in the tank in the inflow step may decrease because the wastewater and the biological sludge do not efficiently contact. If the flow rate at the inlet 12 is larger than 200 cm / sec, the inside of the reaction tank is excessively stirred, and the settled sludge floats again. In some cases, the sludge does not progress, or the re-suspended biological sludge flows out of the outlet, making it impossible to maintain the treatment function.

The installation position of the inlet 12 is not particularly limited as long as it is lower than the interface position of the biological sludge layer 30 formed on the bottom of the reaction tank 10 in the settling step. Assuming that the effective water depth is designed to be 2 m to 8 m and the interface height of the biological sludge layer 30 is operated at 10% to 50% of the height of the reaction tank 10, the inflow port 12 is It is preferably installed at a height within 4 m from the bottom, more preferably at a height within 2 m, even more preferably at a height within 1 m.

It is preferable that the inflow rate of drainage is, for example, in the range of 10% or more and 200% or less. The inflow rate of the wastewater is a ratio of the inflow amount of the wastewater in one operation cycle to the effective volume in the reaction tank 10. By setting the inflow rate of the wastewater in the above range, it is possible to further increase the concentration of the substance to be treated remaining in the reaction tank 10 in the inflow step, and to more efficiently form the biological sludge with high sedimentation. It becomes possible.

{The sludge concentration in the reaction tank 10 in the biological treatment step is preferably, for example, in the range of 1,500 to 30,000 mg / L from the viewpoint of maintaining the soundness (sedimentation, activity, etc.) of the sludge. Further, the sludge load is preferably in the range of 0.05 to 0.60 kg-BOD / kg-MLSS / day from the viewpoint of maintaining the soundness of the sludge, etc., and 0.1 to 0.5 kg-BOD / day. 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 is in the above range. When the sludge load is higher than the above range or when the sludge concentration is higher than the above range, it is desirable to pull out the biological sludge from the inside of the reaction tank 10.

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

The time of the sedimentation step is not particularly limited as long as it is a time from the end of the biological treatment step to the formation of the biological sludge layer 30 on the bottom of the reaction tank 10. It is preferable that the time is such that the sludge interface height becomes 10% to 50% of the height of the reaction tank 10.

(2) The shape of the reaction tank 10 is not limited to a square shape as shown in FIG. 2, and may be, for example, a cylindrical shape. The square-shaped reaction tank is employed in a large-scale treatment plant such as a sewage treatment plant.

The operation cycle of the present embodiment may have an inflow step, a biological treatment step, a sedimentation step, and a discharge step, and may be an operation cycle in which the above-described four steps of the inflow step, biological treatment step, sedimentation step, and discharge step are repeated. In addition, an operation cycle in which a discharge step is performed while an inflow step is performed (hereinafter referred to as an inflow / discharge step), and a biological treatment step and a sedimentation step are repeated. Hereinafter, a water treatment apparatus that performs the latter operation cycle will be described.

FIG. 7 is a schematic sectional view showing another example of the water treatment apparatus according to the present embodiment. In the water treatment apparatus 2 in FIG. 7, the same components as those in the water treatment apparatus 1 in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In the water treatment apparatus 2 shown in FIG. 7, an outlet 16 is provided on one side surface of the reaction tank. The outlet 16 is arranged at the water level of the reaction tank 10 (substantially, the lower end of the outlet 16 is positioned at the water level of the reaction tank 10). In the present embodiment, as described later, since the treated water is discharged together with the inflow of the wastewater, the water level of the reaction tank 10 does not substantially fluctuate. The water treatment apparatus 2 shown in FIG. 7 includes a treated water collecting channel 32 provided outside the reaction tank 10. The treated water collecting channel 32 communicates with the inside of the reaction tank 10 through a discharge port 16 provided in the reaction tank 10.

例 Hereinafter, an example of the operation of the water treatment apparatus 2 of the present embodiment will be described.

The electromagnetic valve 14 a is opened by the control device 24, and the wastewater passes through the inflow pipe 14 and flows into the reaction tank 10 from the inflow port 12. 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 14a and operates the blower 18. Thereby, the aeration gas is supplied from the air diffuser 20 into the reaction tank 10, and the wastewater and the biological sludge in the reaction tank 10 are stirred. Then, the wastewater in the reaction tank 10 is biologically treated with biological sludge (biological treatment step), and the substances to be treated (eg, organic substances) in the wastewater are decomposed. After performing the biological treatment step for a predetermined time, the operation of the blower 18 is stopped by the control device 24, and the stirring and aeration of the wastewater in the reaction tank 10 are stopped. Thereby, sedimentation of biological sludge is performed (sedimentation step), and a biological sludge layer is formed on the bottom of the reaction tank 10. After the sedimentation step is performed for a predetermined time and the biological sludge layer 30 is formed on the bottom of the reaction tank 10, the electromagnetic valve 14a is opened by the control device 24, and the wastewater flows through the inflow pipe 14 by gravity. It flows down and is supplied from the inflow port 12 into the biological sludge layer, and the biologically treated water biologically treated in the reaction tank 10 is discharged from the discharge port 16 to the treated water collecting channel 32 (inflow / discharge step). The treated water is discharged from the treated water collecting channel 32 to the outside of the water treatment apparatus 1. Then, after performing the inflow / outflow process for a predetermined time, the process returns to the biological treatment process described above.

The inflow / discharge process time is determined according to, for example, the inflow rate of the wastewater and the flow rate of the wastewater to the reaction tank 10. By the way, when the water area load of the reaction tank 10 which is a value obtained by dividing the flow rate of the wastewater to the reaction tank 10 by the horizontal sectional area of the reaction tank 10 is set high, the light sludge fraction in the sludge is selectively removed from the system. It is possible to discharge and leave a highly sedimentable sludge fraction in the tank, which promotes the formation of highly sedimentable biological sludge.However, during the start-up period when the sedimentation of sludge is not high, There is a concern that sludge in the tank will flow out and the biological treatment function will deteriorate. On the other hand, when the water area load of the reaction tank 10 is set low, the selection effect of the sludge decreases, and when the inflow rate of the wastewater is increased, the inflow / discharge process time becomes long, and the formation of sludge having high sedimentation property is formed. There is a concern that this will be difficult. In view of the above circumstances, the water area load on the reaction tank 10 is preferably 0.5 m / h or more and 20 m / h or less, and more preferably 1 m / h or more and 10 m / h or less. If the water area load of the reaction tank 10 can be set high with the improvement of the sedimentation property of the biological sludge in the tank, the water area of the reaction tank 10 may be set according to the sedimentation property of the biological sludge. It is also possible to increase the load and shorten the inflow / drainage process time according to the water area load and the inflow rate of wastewater.

FIG. 8 is a schematic sectional view showing another example of the water treatment apparatus of the present embodiment. In the water treatment apparatus 3 shown in FIG. 8, the same components as those of the water treatment apparatus 1 shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The water treatment device 3 shown in FIG. The partition wall 17 is provided upright in the reaction tank 10 to partition the inside of the reaction tank 10 into a first chamber 10f and a second chamber 10g. An opening communicating the first chamber 10f and the second chamber 10g is provided below the partition 17, and the opening serves as the inflow port 12 described above. The first chamber 10f defined by the partition 17 serves as an inflow section extending vertically upward from the inflow port 12, and the second chamber 10g defined by the partition 17 serves as the above-described operation cycle (inflow step, biological treatment step). , Settling process, discharge process).

In the inflow step of the water treatment device 3 shown in FIG. 8, the electromagnetic valve 34a is opened by the control device 24, and the wastewater is supplied from the raw water introduction pipe 34 to the first chamber 10f. The wastewater flows down in the first chamber 10f by gravity and is supplied from the inflow port 12 into the biological sludge layer formed on the bottom of the second chamber 10g. After the inflow step, a biological treatment step, a sedimentation step, and a discharge step are performed in the second chamber 10g. In addition, as shown in FIG. 7, the discharge port 16 may be arranged at the water level of the reaction tank 10, and the inflow / discharge step, the biological treatment step, and the sedimentation step may be performed.

形状 The shape of the opening (inflow port 12) provided in the partition wall 17 is not particularly limited, and may be a rectangular shape, a circle or an ellipse, or the like. In addition, at least one opening (the inlet 12) may be formed in the partition 17.

The position of the partition wall 17 is not particularly limited. However, the position of the first chamber 10f in the vertical sectional view of the reaction tank 10 is such that the wastewater can be efficiently brought into contact with the biological sludge layer in the second chamber 10g. The partition 17 is preferably installed so that the ratio of the width is に 対 し て or less with respect to the width of the second chamber 10 g, and it is more preferable that the partition 17 is installed so as to be １ ／ or less.

FIG. 9 is a schematic sectional view showing another example of the water treatment apparatus of the present embodiment. In the water treatment apparatus 4 shown in FIG. 9, the same components as those of the water treatment apparatus 1 shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In the water treatment apparatus 4 shown in FIG. 9, the inflow port 12 is provided on the side surface of the reaction vessel 10, and the inflow pipe 14 extending vertically upward from the inflow port 12 is arranged outside the reaction vessel 10. Thus, the inflow pipe 14 may be provided outside the reaction tank 10.

FIGS. 10 to 12 are schematic sectional views showing another example of the water treatment apparatus of the present embodiment. In the water treatment apparatus 5 shown in FIGS. 10 to 12, the same components as those of the water treatment apparatus 1 shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In the water treatment device 5 shown in FIG. 10, an inflow port 12 a is formed at a lower end of the inflow pipe 14. The inflow port 12a shown in FIG. 10 is open downward in the vertical direction, and drainage is supplied vertically downward into the biological sludge layer from the inflow port 12a. In the water treatment apparatus 5 shown in FIG. 11, two inlets 12 b are formed on two side surfaces of the inflow pipe 14. Each of the inlets 12b shown in FIG. 11 is open in the horizontal direction, and drainage is supplied from the respective inlets 12b into the biological sludge layer in the horizontal direction. Further, in the water treatment apparatus 5 shown in FIG. 12, inflow ports 12 a and 12 b are formed at two places at a lower end and a side surface of the inflow pipe 14. The inlet 12a at the lower end shown in FIG. 12 opens vertically, the inlet 12b at the side opens horizontally, and the drainage flows vertically from the lower inlet 12a into the biological sludge layer. And is supplied horizontally into the biological sludge layer from the side inlet 12b.

It is sufficient that at least one inflow port is provided for each inflow pipe, but it is preferable that two or more inflow ports are provided as shown in FIGS. . The opening direction of the inflow port is not particularly limited, but is preferably horizontal or lower than the horizontal direction as shown in FIGS. 11 to 13 in consideration of the diffusibility of drainage. That is, it is preferable that the wastewater is supplied from the inflow port into the biological sludge layer in the horizontal direction or below the horizontal direction.

FIG. 13A is a schematic cross-sectional view illustrating another example of the water treatment apparatus of the present embodiment, and FIG. 13B is a schematic top view illustrating another example of the water treatment apparatus of the present embodiment. is there. In the water treatment device 6 shown in FIG. 13, the same components as those of the water treatment device 1 shown in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted. In FIG. 13B, the air diffuser including the blower 18 and the air diffuser 20 and the controller 24 are omitted. The water treatment apparatus 6 shown in FIG. 13 is provided at an upper part of the reaction tank 10 and extends substantially horizontally, and a drainage inflow trough 36 is provided at a water level in the reaction tank 10 and extends substantially horizontally. 38. A plurality of inflow pipes 14 are connected to the drainage inflow trough 36. Inflow ports 12 a and 12 b are formed at the lower end and side surfaces of the inflow pipe 14.

水 The water treatment apparatus 6 shown in FIG. 13 performs an operation cycle in which the inflow / discharge step, the biological treatment step, and the sedimentation step are repeated. Specifically, in the inflow / outflow process, the wastewater flows from each wastewater inflow trough 36 into each inflow pipe 14, flows down the inflow pipe 14 by gravity, and flows from the inflow ports (12 a, 12 b) into the biological sludge layer. And the biologically treated water in the reaction tank 10 flows over the treated water collecting trough 38 and is discharged from the treated water collecting trough 38 to the outside of the reaction tank 10. After the inflow / outflow process, the biological treatment process and the sedimentation process described above are performed.

生物 The highly sedimentable biological sludge formed by the water treatment apparatus of the present embodiment may be used for its own biological treatment, or may be taken out of the reaction tank 10 and supplied to another biological treatment tank. The other biological treatment tank may be a semi-batch type as in the present embodiment, or a continuous type in which biological treatment is performed while continuously introducing wastewater. Further, the biologically treated water obtained by the water treatment apparatus of the present embodiment may be supplied to another biological treatment tank (continuous or semi-batch type). Hereinafter, a specific description will be given with reference to the drawings.

FIG. 14 is a schematic configuration diagram showing another example of the water treatment device of the present embodiment. The water treatment apparatus 7 shown in FIG. 14 includes a reaction tank 10 and a continuous biological treatment tank 40. The reaction tank 10 is the reaction tank according to the present embodiment, and the specific configuration is the same as described above, and a description thereof will be omitted. The water treatment apparatus 7 shown in FIG. 14 includes raw water introduction pipes 42a and 42b, a treated water supply pipe 44, a biological sludge supply pipe 46, and a treated water discharge pipe 48. The treated water supply pipe 44 is provided with a valve 44a, and the biological sludge supply pipe 46 is provided with a valve 46a.

The raw water introduction pipe 42a is connected to the reaction tank 10 (specifically, the inflow section). The raw water introduction pipe 42b is connected to the continuous biological treatment tank 40. One end of the treated water supply pipe 44 is connected to the reaction tank 10, and the other end is connected to the continuous biological treatment tank 40. Further, one end of the biological sludge supply pipe 46 is connected to the reaction tank 10, and the other end is connected to the continuous biological treatment tank 40. The treated water discharge pipe 48 is connected to the continuous biological treatment tank 40.

The wastewater flowing through the raw water introduction pipe 42a is supplied to the reaction tank 10, and the wastewater flowing through the raw water introduction pipe 42b is supplied to the continuous biological treatment tank 40. In the reaction tank 10, the above-described operation cycle (inflow step (inflow / outflow step), biological treatment step, sedimentation step, and discharge step) is performed. Then, by opening the valve 46 a at an arbitrary timing, the highly sedimentable biological sludge formed in the reaction tank 10 is supplied from the biological sludge supply pipe 46 to the continuous biological treatment tank 40. Further, by opening the valve 44 a at an arbitrary timing, the treated water in the reaction tank 10 is supplied from the treated water supply pipe 44 to the continuous biological treatment tank 40. In the continuous biological treatment tank 40, for example, under aerobic conditions and in the presence of biological sludge supplied from the reaction tank 10, wastewater continuously flowing from the raw water introduction pipe 42 b and treated water from the reaction tank 10 The wastewater that appropriately flows in through the supply pipe 44 is biologically treated. As described above, by supplying the biological sediment with high sedimentation formed in the reaction tank 10 to the continuous biological treatment tank 40, for example, the biological treatment speed of the continuous biological treatment tank 40 can be improved.

FIG. 15A is a schematic cross-sectional view illustrating an example of a water treatment apparatus according to the present embodiment, and FIG. 15B is a schematic top view illustrating an example of the water treatment apparatus according to the present embodiment. As shown in FIG. 15A, the water treatment apparatus 101 includes a reaction tank 110, a raw water introduction apparatus including a raw water introduction pipe 112, a raw water pump 114, and an electromagnetic valve 116, and a diffuser including a blower 118 and an air diffusion pipe 120. An apparatus, a treated water collecting channel 122 and a control device 124 are provided. In FIG. 15B, the air diffuser including the blower 118 and the air diffuser 120 and the control device 124 are omitted.

反 応 The reaction tank 110 of the present embodiment includes an inflow port 126 through which drainage flows into the tank. In the reaction tank 110 shown in FIG. 15, a plurality of inlets 126 are provided on one side of the reaction tank 110. The inflow port 126 is disposed at a position lower than the interface position of the biological sludge layer formed on the bottom of the reaction tank 110 in the sedimentation step described below, and is opened in the horizontal direction. From the biological sludge layer. Here, the horizontal direction defined in the present specification includes a substantially horizontal direction. The substantially horizontal direction includes a direction having an inclination angle of 10 ° or less with respect to a horizontal direction (usually, a direction parallel to a direction in which the flat surface of the bottom of the reaction tank extends).

数 The number of inflow ports 126 is not particularly limited, but is desirably a plurality in order to enhance the diffusibility of drainage. When a plurality of inlets 126 are provided, they are preferably arranged at intervals of, for example, 0.5 m to 5 m from the viewpoint of improving the diffusibility of drainage. If the inlet 126 is opened so as to supply the wastewater into the biological sludge layer in the horizontal direction, the inlet 126 is located at a position higher than the interface position of the biological sludge layer formed on the bottom of the reaction tank 110 in the settling process. You may.

反 応 The reaction tank 110 of the present embodiment includes an outlet 128 for discharging the treated water biologically treated in the reaction tank 110. In the reaction tank 110 shown in FIG. 15, a discharge port 128 is provided on a side surface opposite to one side surface of the reaction tank 110 in which the inflow port 126 is provided. The outlet 128 is arranged at the level of the water surface of the reaction vessel 110 (substantially, the lower end of the outlet 128 is located at the level of the water level of the reaction vessel 110). In the present embodiment, as will be described later, since the treated water is discharged together with the inflow of the waste water, the water level of the reaction tank 110 does not substantially fluctuate.

原 The raw water introduction pipe 112 constituting the raw water introduction device is connected to the inflow port 126 from outside the reaction tank 110. The raw water introduction pipe 112 is provided with a raw water pump 114 and an electromagnetic valve 116 constituting a raw water introduction device. The raw water pump 114 and the electromagnetic valve 116 are electrically connected to the control device 124. The raw water introduction device is not limited to the above device configuration as long as it has a function of supplying drainage to the inflow port 126 provided in the reaction tank 110.

処理 The treated water collecting channel 122 shown in FIG. 15 is provided outside the reaction tank 110 and communicates with the inside of the reaction tank 110 via an outlet 128 provided in the reaction tank 110.

The blower 118 constituting the air diffuser is connected to the air diffuser 120, and an aerated gas such as oxygen or air is sent to the air diffuser 120 by the blower 118, and the aerated gas is supplied into the reaction tank 110 by the air diffuser 120. Is done. Thereby, the water in the reaction tank 110 flows and is stirred. Although description in the drawing is omitted, for example, a stirring device in which a stirring blade rotates with the rotation of the motor may be installed in the reaction tank 110, and the water in the reaction tank 110 may be stirred. The water treatment apparatus 101 shown in FIG. 15 is intended for biological treatment under aerobic conditions, but can also be applied to biological treatment under anaerobic conditions. When processing is performed under anaerobic conditions, a stirring device may be installed without installing a diffuser.

The control device 124 includes, for example, a microcomputer configured with a CPU for calculating a program, a ROM and a RAM for storing the program and the calculation result, and an electronic circuit, and has a function of controlling the operation of the air diffuser and the raw water introduction device. It has.

例 Hereinafter, an example of the operation of the water treatment apparatus 101 of the present embodiment will be described.

The electromagnetic valve 116 is opened by the control device 124, and the raw water pump 114 is operated, so that the wastewater passes through the raw water introduction pipe 112 and flows into the reaction tank 110 from the inlet 126. It is desirable that biological sludge be charged in the reaction tank 110 in advance.

FIG. 16 is a schematic cross-sectional view showing an example of the state of the water treatment device during the biological treatment step. When the water level of the waste water in the reaction tank 110 reaches a predetermined water level, the control device 124 closes the electromagnetic valve 116, stops the operation of the raw water pump 114, and starts the blower 118. Thereby, as shown in FIG. 16, the aeration gas is supplied from the diffuser pipe 120 into the reaction tank 110, and the wastewater and the biological sludge in the reaction tank 110 are stirred. Then, the wastewater in the reaction tank 110 is biologically treated with biological sludge (biological treatment step), and the substances to be treated (for example, organic substances) in the wastewater are decomposed.

FIG. 17 is a schematic cross-sectional view showing an example of the state of the water treatment device during the settling process. After performing the biological treatment process for a predetermined time, the operation of the blower 118 is stopped by the control device 124, and the stirring and aeration of the wastewater in the reaction tank 110 are stopped. Thereby, as shown in FIG. 17, the settling of the biological sludge is performed (settling step), and the biological sludge layer 130 is formed on the bottom of the reaction tank 110.

FIG. 18 is a schematic cross-sectional view showing an example of the state of the water treatment device during the inflow / outflow process. After the settling process is performed for a predetermined time and the biological sludge layer 130 is formed on the bottom of the reaction tank 110, the raw water pump 114 is operated by the control device 124, the electromagnetic valve 116 is opened, and the wastewater is discharged. The raw water is supplied from the raw water introduction pipe 112 to the inflow port 126. As a result, as shown in FIG. 18, the wastewater is supplied horizontally into the biological sludge layer 130 from the inlet 126, and the biologically treated water that has been biologically treated in the reaction tank 110 is discharged from the outlet 128. The water is discharged to the water collecting channel 122 (inflow / discharge process). The treated water is discharged from the treated water collecting channel 122 to the outside of the water treatment apparatus 101. Then, after performing the inflow / outflow process for a predetermined time, the process returns to the biological treatment process described above. That is, an operation cycle in which the inflow / discharge process, the biological treatment process, and the sedimentation process are repeated is performed.

Here, it is considered that extracellular matrix (EPS) produced by bacteria influences the formation of highly sedimentable biological sludge (eg, granulated biological sludge) in the operation cycle. In order to form EPS, it is important to form a concentration gradient of the substance to be treated that is biologically treated in the reaction tank 110. For example, when biologically treating organic matter in wastewater, it is important to form a concentration gradient of organic matter, and when biologically treating a nitrogen-containing substance such as ammonia nitrogen or nitrate nitrogen, a nitrogen-containing substance is required. It is important to form a concentration gradient. The concentration gradient of the substance to be treated increases the concentration of the substance to be treated in the reaction tank 110 in the inflow / emission step (saturated state), and causes the substance to be treated in the reaction tank 110 to be consumed in the biological treatment step. Is formed by lowering the concentration of the substance to be treated in the reaction tank 110 (starved state). Then, as in the present embodiment, in the inflow / discharge process, by allowing the wastewater to flow horizontally into the biological sludge layer 130 from the inflow port 126, it is possible to ensure a sufficient path for the wastewater to contact the biological sludge. As a result, the substance to be treated in the wastewater is likely to remain in the tank. Thereby, in the inflow / discharge process, the concentration of the substance to be treated remaining in the reaction tank 110 can be efficiently increased, so that the concentration gradient of the substance to be treated in the reaction tank 110 can be increased. . As a result, it is possible to form biological sludge having high sedimentation, and it is possible to improve the biological treatment speed. When the wastewater is supplied into the biological sludge layer 130 in an upward flow (that is, the wastewater is supplied vertically into the biological sludge layer 130), the thickness of the biological sludge layer 130 formed in the reaction tank 110 is reduced. If the water is not thick to some extent, it is not possible to secure a sufficient route for the wastewater to contact the biological sludge, and it is difficult to efficiently increase the concentration of the substance to be treated remaining in the reaction tank 110. However, in the case of the horizontal inflow of the present embodiment, even if the thickness of the biological sludge layer 130 formed in the reaction tank 110 is thin, compared with the case of the above-mentioned upward flow, the drainage is Since a sufficient path for contacting with the target is ensured, the concentration of the substance to be treated remaining in the reaction tank 110 can be increased. Further, according to the water treatment apparatus 101 of the present embodiment, unlike the conventional water treatment apparatus, it is not necessary to install a distributor at the inflow of wastewater, so that an increase in facility costs and operation management costs is suppressed. You. In particular, by applying the water treatment apparatus 101 of the present embodiment as a water treatment apparatus for a large-scale treatment facility, it is considered that facility costs and operation management costs can be effectively reduced.

生物 The highly sedimentable biological sludge formed by the water treatment apparatus 101 of the present embodiment may be used for its own biological treatment, or may be taken out of the reaction tank 110 and supplied to another biological treatment tank. The other biological treatment tank may be a semi-batch type as in the present embodiment, or a continuous type in which biological treatment is performed while continuously introducing wastewater. Thereby, for example, the biological treatment speed in another biological treatment tank can be improved. Further, the biologically treated water obtained by the water treatment apparatus 101 of the present embodiment may be supplied to another biological treatment tank (continuous or semi-batch type). Thereby, for example, it is possible to improve the quality of the biological treatment water.

運 転 The operating conditions and modified examples of the water treatment apparatus of the present embodiment will be described below.

The wastewater applied to the water treatment apparatus 101 of the present embodiment is, for example, a biodegradable substance such as food processing factory wastewater, chemical factory wastewater, semiconductor factory wastewater, machine factory wastewater, sewage, human waste, or river water. Wastewater containing the target substance). The substance having biodegradability is, for example, an organic substance, a nitrogen-containing substance such as ammoniacal nitrogen, nitrate nitrogen, or the like. 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). In addition, for example, when biologically treating wastewater containing a nitrogen-containing substance, the nitrogen-containing substance in the wastewater is decomposed into nitrogen gas by contact with biological sludge (microorganisms).

If the wastewater applied to the water treatment apparatus 101 of the present embodiment contains a large amount of fats and oils, the biological treatment may be adversely affected. It is preferable to remove oils and fats to about 150 mg / L or less, for example, by an existing method such as coagulation pressure flotation and adsorption.

Ｂ The BOD concentration in the wastewater applied to the water treatment apparatus 101 of the present embodiment is not particularly limited. In general, the BOD concentration in wastewater in which it is difficult to form highly sedimentable biological sludge is in the range of 50 to 200 mg / L. However, according to the water treatment apparatus 101 of the present embodiment, Even in the range of the BOD concentration, it is possible to form a biological sludge having high sedimentation. In addition, in the water treatment apparatus 101 according to the present embodiment, for example, it is possible to form biological sludge having an SVI 30 as a sedimentation index of 50 mL / g or less and an SVI 5 of 70 mL / g or less.

In the inflow / outflow process, increasing the concentration of the substance to be treated in the reaction tank 110 (more increasing the substance to be treated in the reaction tank 110 at the start of the biological treatment step) is effective for forming granules. The residual ratio of the substance to be treated in the reaction tank 110 in the discharge step is preferably 50% or more, more preferably 70% or more. Here, the residual ratio of the substance to be treated in the reaction tank 110 indicates a ratio of the concentration of the substance to be treated in the tank after the inflow / outflow process to the concentration of the substance to be treated in the wastewater.

The installation position of the inlet 126 is not particularly limited as long as it is lower than the interface position of the biological sludge layer 130 formed on the bottom of the reaction tank 110 in the settling step. Assuming that the effective water depth is designed to be 2 m to 8 m and the interface height of the biological sludge layer 130 is operated at 10% to 50% of the height of the reaction tank 110, the inlet 126 is It is preferably installed at a height within 4 m from the bottom, more preferably at a height within 2 m, even more preferably at a height within 1 m.

It is preferable that the inflow rate of drainage is, for example, in a range of 10% or more and 100% or less. The inflow rate of the wastewater is a ratio of the inflow amount of the wastewater in one operation cycle to the effective volume in the reaction tank 110. Here, in order to increase the concentration of the substance to be treated remaining in the reaction tank 110, it is better to set the inflow rate of the wastewater as high as possible. On the other hand, as the inflow rate of the wastewater increases, There is a concern that treated water will deteriorate due to short-circuiting of wastewater. Therefore, in view of these, it is more preferable that the inflow rate of the wastewater 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 at the subsequent stage of the reaction tank 110 and the quality of the final treated water after the latter treatment device is not degraded, there is no particular limitation on the inflow rate of the wastewater. It is also possible to use When the inflow rate of the wastewater exceeds 100%, it is preferable to set the upper limit of the inflow rate of the wastewater to 200% or less in order to suppress a decrease in the number of operation cycles.

The inflow / discharge process time is determined according to, for example, the inflow rate of the wastewater and the flow rate of the wastewater to the reaction tank 110. By the way, when the water area load of the reaction tank 110, which is a value obtained by dividing the flow rate of the wastewater to the reaction tank 110 by the horizontal sectional area of the reaction tank 110, is set high, the light sludge fraction in the sludge is selectively removed from the system. It is possible to discharge and leave a highly sedimentable sludge fraction in the tank, which promotes the formation of highly sedimentable biological sludge.However, during the start-up period when the sedimentation of sludge is not high, There is a concern that sludge in the tank will flow out and the biological treatment function will deteriorate. On the other hand, when the water area load of the reaction tank 110 is set low, the selection effect of the sludge is reduced, and when the inflow rate of the wastewater is increased, the inflow / discharge process time becomes longer, and the formation of sludge having a high sedimentation property is formed. There is a concern that this will be difficult. In view of the above circumstances, the water area load on the reaction tank 110 is preferably 0.5 m / h or more and 20 m / h or less, and more preferably 1 m / h or more and 10 m / h or less. In addition, when the water area load of the reaction tank 110 can be set high with the improvement of the sedimentation property of the biological sludge in the tank, the water area of the reaction tank 110 is set according to the sedimentation property of the biological sludge. It is also possible to increase the load and shorten the inflow / drainage process time according to the water area load and the inflow rate of wastewater.

The concentration of the sludge in the reaction tank 110 in the biological treatment step is preferably, for example, in the range of 1,500 to 30,000 mg / L from the viewpoint of maintaining the integrity of the sludge (sedimentation, activity, etc.). Further, the sludge load is preferably in the range of 0.05 to 0.60 kg-BOD / kg-MLSS / day from the viewpoint of maintaining the soundness of the sludge, etc., and 0.1 to 0.5 kg-BOD / day. 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 is in the above range. When the sludge load is higher than the above range or when the sludge concentration is higher than the above range, it is desirable to extract biological sludge from inside the reaction tank 110.

ＰＨ The pH in the reaction tank 110 is desirably set to a range suitable for general microorganisms, for example, preferably 6 to 9, and more preferably 6.5 to 7.5. When the pH value is out of the above range, it is preferable to add an acid or an alkali to adjust the pH so as to be in the above range. The dissolved oxygen (DO) in the reaction tank 110 is preferably 0.5 mg / L or more, particularly preferably 1 mg / L or more under aerobic conditions.

The time of the sedimentation step is not particularly limited as long as the time is from the end of the biological treatment step to the time when the biological sludge layer 130 is formed on the bottom of the reaction tank 110. It is preferable that the time is such that the sludge interface height becomes 10% to 50% of the height of the reaction tank 110.

形状 The shape of the reaction tank 110 is not limited to a square shape as shown in FIG. 15, but may be, for example, a cylindrical shape. The square-shaped reaction tank 110 is employed in a large-scale treatment plant such as a sewage treatment plant. Hereinafter, an example of a square reaction tank used in a large-scale treatment plant will be described.

FIG. 19 is a schematic top view showing an example of a square reaction tank used in a large-scale treatment plant. The rectangular reaction vessel 110 shown in FIG. 19 is a rectangular reaction vessel having a pair of opposed long side walls (110a, 110b) and a pair of opposed short side walls (110c, 110d) in a horizontal sectional view. It is. A plurality of inlets 126 are provided on one long side wall 110 a of the reaction tank 110, and an outlet 128 is provided on the other long side wall 110 b of the reaction tank 110. Further, a treated water collecting channel 122 is provided outside the other long side wall 110b, and the treated water collecting channel 122 communicates with the inside of the reaction tank 110 via a discharge port 128. Although not described in the drawings, the outlet 128 is disposed at the water level in the reaction tank 110, and the inlet 126 is lower than the interface position of the biological sludge layer formed at the bottom of the reaction tank 110 in the settling process. Is located in the position. Then, the waste water is supplied from the inlet 126 into the biological sludge layer in the horizontal direction.

反 応 In the case of the reaction tank 110 employed in a large-scale treatment plant, the ratio of the horizontal cross-sectional area of the reaction tank 110 to the effective water depth of the reaction tank 110 tends to increase. As a square-shaped 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 or more. However, in a conventional water treatment apparatus in which wastewater flows into the reaction tank 110 in an upward flow by a distributor, [(long side wall length + short side wall length) / effective water depth] is 1 m / m or more. The use of a reaction tank may significantly increase facility costs and operation management costs in terms of drainage diffusivity and distributor maintenance. On the other hand, if the water treatment apparatus of the present embodiment employs a reaction tank having [(long side wall length + short side wall length) / effective water depth] of 1 m / m or more, no distributor is required. Therefore, the increase in facility costs and operation management costs can be suppressed as compared with the above-described conventional water treatment apparatus. Therefore, the water treatment device of the present embodiment is particularly suitable as a water treatment device for a large-scale treatment facility.

は Regarding the installation location of the inflow port 126 and the discharge port 128, it is preferable that the inflow port 126 is provided on one long side wall 110a and the discharge port 128 is provided on the other long side wall 110b. When the inlet 126 is installed on one short side wall 110c and the outlet 128 is installed on the other short side wall 110d, compared with the case where the inlet 126 and the outlet 128 are installed on the long side walls (110a, 110b). Therefore, since the horizontal distance from the inlet 126 to the outlet 128 becomes longer, the contact efficiency between the wastewater and the biological sludge layer decreases, and the concentration of the target substance remaining in the reaction tank 110 may decrease. .

水平 The horizontal distance from the inlet 126 to the outlet 128 is, for example, preferably within 10 m, more preferably within 6 m, from the viewpoint of suppressing a decrease in the concentration of the substance to be treated remaining in the reaction tank 110. If the horizontal distance from the inlet 126 to the outlet 128 exceeds 10 m, it becomes difficult to efficiently contact the wastewater with the biological sludge layer, and the concentration of the substance to be treated remaining in the reaction tank 110 is reduced. There are cases.

FIG. 20 is a schematic top view showing another example of the rectangular reaction tank employed in a large-scale treatment plant. The reaction tank 110 shown in FIG. 20 has a first inlet 126a provided on one side of the reaction tank 110, and a second inlet 126b provided between the first inlet 126a and the outlet 128. . Each of the inlets (126a, 126b) is arranged at a position lower than the interface position of the biological sludge layer formed on the bottom of the reaction tank 110 in the settling process.

FIG. 21 (A) is a schematic cross-sectional view showing another example of a square-shaped reaction tank employed in a large-scale processing plant, and FIG. 21 (B) is a square-shaped reaction tank employed in a large-scale processing plant. FIG. 4 is a schematic top view showing another example of the reaction tank having the shape of a circle. The reaction tank 110 shown in FIG. 21 includes the first inlet 126a and the second inlet 126b described above. In the reaction tank 110, a first treated water collecting channel 122a and a second treated water collecting channel 122b are provided. The first treated water collecting channel 122a is installed inside a side surface opposite to one side surface of the reaction tank 110 in which the first inlet 126a is provided, and the second treated water collecting passage 122b is connected to the first treated water collecting passage 122b. It is provided between 122a and the first inlet 126a. The treated water in the reaction tank 110 shown in FIG. It flows inside and is discharged out of the reaction tank 110. That is, the first treated water collecting passage 122a and the second treated water collecting passage 122b shown in FIG. 21 function as the outlet 128 described above.

When the horizontal distance between the inflow port provided on one side of the reaction tank and the discharge port provided on the side opposite to the one side becomes long, the reaction tank 110 shown in FIGS. As described above, it is preferable to provide one or more inlets and outlets between the inlet provided on one side of the reaction tank and the outlet provided on the side opposite to the one side. As a result, the contact efficiency between the wastewater and the biological sludge layer increases, and the concentration of the target substance remaining in the reaction tank tends to increase.

FIG. 24A is a cross-sectional view illustrating another example of the water treatment apparatus of the present embodiment, and FIG. 24B is a schematic top view illustrating another example of the water treatment apparatus of the present embodiment. . In FIG. 24B, the air diffuser including the blower 118 and the air diffuser 120 and the control device 124 are omitted. In FIG. 24, a raw water introduction pipe 112 is introduced into the center of the reaction tank 110, and is branched into a plurality of drainage inlets (126a, 126b) in the reaction tank 110. The treated water collecting channels (122a, 122b) are installed on two opposite sides of the reaction tank 110. The outlets of the drainage inlets (126a, 126b) are installed toward the respective treated water collecting channels (122a, 122b). In order to increase the residual ratio of the substance to be treated during the inflow / outflow process, it is preferable that the flow velocity at the inflow port calculated from the distance between the inflow port and the side face of the reaction tank is not less than a certain value. On the other hand, when the distance from the inlet to the side of the reaction tank facing the tank is long and it is difficult to keep the flow velocity high, by employing this embodiment, the distance from the inlet to the outlet is reduced, Even when the flow velocity at the inflow port is low, it is possible to increase the residual ratio of the substance to be treated during the inflow / outflow process.

FIG. 22A is a schematic cross-sectional view illustrating another example of the water treatment apparatus of the present embodiment, and FIG. 22B is a schematic top view illustrating another example of the water treatment apparatus of the present embodiment. is there. In FIG. 22B, the air diffuser including the blower 118 and the air diffuser 120 and the control device 124 are omitted. In the water treatment apparatus 102 shown in FIG. 22, the same components as those of the water treatment apparatus 101 shown in FIG. 15 are denoted by the same reference numerals, and description thereof will be omitted. The water treatment apparatus 102 illustrated in FIG. 22 includes a distribution path 113 and a raw water pipe 115. The raw water introduction pipe 112 is connected to an upper end of a raw water pipe 115 via a distribution path 113. The raw water pipe 115 is a pipe extending in the vertical direction, and its upper end is located above the water level in the reaction tank 110, and its lower end is connected to the inflow port 126. In the present specification, the pipe extending in the vertical direction includes a pipe extending in the substantially vertical direction. The substantially vertical direction includes a direction having an inclination angle of 30 ° or less with respect to the vertical direction. Note that the raw water pipe 115 may be provided outside the reaction tank 110.

In the inflow / outflow process of the water treatment apparatus 102 shown in FIG. 22, the electromagnetic valve 116 is opened by the control device 124, and the wastewater is supplied from the raw water introduction pipe 112 to the raw water pipe 115 via the distribution path 113. Then, the wastewater flows down in the raw water pipe 115 by gravity and is supplied in a horizontal direction from the inlet 126 into the biological sludge layer formed in the reaction tank 110. In addition, when the wastewater flows into the reaction tank 110, the biologically treated water in the reaction tank 110 is discharged from the discharge port 128 to the treated water collecting channel 122. As described above, in the water treatment apparatus 102 illustrated in FIG. 22, the drainage can be caused to flow into the reaction tank 110 by gravity without using a pump, so that it is possible to reduce the cost of operation. For example, it is suitable for a sewage treatment plant having a large amount of treated water.

FIG. 23A is a schematic cross-sectional view illustrating another example of the water treatment apparatus of the present embodiment, and FIG. 23B is a schematic top view illustrating another example of the water treatment apparatus of the present embodiment. is there. In FIG. 23B, the air diffuser including the blower 118 and the air diffuser 120 and the control device 124 are omitted. In the water treatment apparatus 103 shown in FIG. 23, the same components as those of the water treatment apparatus 101 shown in FIG. 15 are denoted by the same reference numerals, and description thereof will be omitted. The water treatment apparatus 103 shown in FIG. 23 has a distribution channel 113 and a partition wall 117. The partition wall 117 stands vertically in the reaction tank 110, and partitions the inside of the reaction tank 110 into a first chamber 110f and a second chamber 110g. An opening communicating the first chamber 110f and the second chamber 110g is provided below the partition 117, and the opening serves as the inflow port 126 described above. The discharge port 128 is provided on the side surface on the second chamber 110g side, and communicates with the treated water collecting channel 122 provided outside the second chamber 110g.

In the reaction tank 110 shown in FIG. 23, the first chamber 110f defined by the partition 117 is a room for receiving drainage, and the second chamber 110g defined by the partition 117 is used for the above-described operation cycle (inflow / outflow process, biological This is the room where the processing step and the sedimentation step are performed.

In the inflow / drainage process of the water treatment device 103 shown in FIG. 23, the electromagnetic valve 116 is opened by the control device 124, and the wastewater is supplied from the raw water introduction pipe 112 to the first chamber 110f via the distribution path 113. Then, the wastewater passes through the first chamber 110f and is supplied in a horizontal direction from the inflow port 126 into the biological sludge layer formed on the bottom of the second chamber 110g. In addition, when the wastewater flows into the second chamber 110g, the biologically treated water in the second chamber 110g is discharged from the discharge port 128 to the treated water collecting channel 122. After the inflow / outflow process, a biological treatment process and a sedimentation process are performed in the second chamber 110g.

形状 The shape of the opening (inflow port 126) provided in the partition wall 117 is not particularly limited, and may be a rectangular shape, a circle or an ellipse, or the like. In addition, at least one opening (inflow port 126) may be formed in the partition wall 117.

The position of the partition 117 is not particularly limited, but in terms of allowing the waste water to efficiently contact the biological sludge layer in the second chamber 110g, the position of the first chamber 110f in the vertical cross section of the reaction tank 110 is considered. It is preferable that the partition wall 117 be installed so that the width ratio is 1/2 or less with respect to the width of the second chamber 110g, and it is more preferable that the partition wall 117 be installed so that it becomes 1/5 or less.

FIG. 25A is a schematic cross-sectional view illustrating another example of the water treatment apparatus of the present embodiment, and FIG. 25B is a schematic top view illustrating another example of the water treatment apparatus of the present embodiment. is there. In FIG. 25B, the air diffuser including the blower 118 and the air diffuser 120 and the control device 124 are omitted. In the water treatment apparatus 104 shown in FIG. 25, the same components as those of the water treatment apparatus 101 shown in FIG. 15 are denoted by the same reference numerals, and description thereof will be omitted. The reaction tank 110 shown in FIG. 25 is a rectangular reaction tank having a pair of opposed walls (110a, 110b) and a pair of opposed walls (110c, 110d) in a horizontal sectional view. A plurality of inlets 126 are provided on one long side wall 110a of the reaction tank 110, and an outlet 128 is also provided. The discharge port 128 is disposed at the water level in the reaction tank 110, and the inflow port 126 is disposed at a position lower than the interface position of the biological sludge layer formed at the bottom of the reaction tank 110 in the settling process. Then, the wastewater is supplied from the inlet 126 into the biological sludge tank in the horizontal direction. Since the inlet 126 and the outlet 128 are provided on the same wall surface, when the drainage is ejected from the inlet 126 into the sediment with a certain flow rate or more and the drainage reaches the wall surface opposite to the inlet. In addition, since it does not rise as it is toward the discharge port as an upward flow, it is possible to prevent a short path of the substance to be treated.

FIG. 26A is a schematic cross-sectional view illustrating another example of the water treatment apparatus of the present embodiment, and FIG. 26B is a schematic top view illustrating another example of the water treatment apparatus of the present embodiment. is there. In FIG. 26B, the air diffuser including the blower 118 and the air diffuser 120 and the control device 124 are omitted. In the water treatment apparatus 105 shown in FIG. 26, the same components as those of the water treatment apparatus 101 shown in FIG. 15 are denoted by the same reference numerals, and description thereof will be omitted. The water treatment apparatus 105 shown in FIG. 26 includes a distribution path 113 and a raw water pipe 115. The raw water introduction pipe 112 is connected to an upper end of the raw water pipe 115 via a distribution path 113. The raw water pipe 115 is a pipe extending in the vertical direction. The upper end of the raw water pipe 115 is located above the water level in the reaction tank 110, and the lower end is connected to the inflow port 126. In the present specification, the pipe extending in the vertical direction includes a pipe extending in a substantially vertical direction. The substantially vertical direction includes a direction having an inclination angle of 30 ° or less with respect to the vertical direction. Note that the raw water pipe 115 may be provided outside the reaction tank 110. In the water treatment device 105, similarly to the above-described water treatment device 104, the inlet 126 and the outlet 128 are installed on the same wall surface.

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)
The test was performed using a reaction vessel having an effective volume of 1.4 m ³ . As shown in FIG. 2 (B), two inflow pipes were provided on opposite sides of the reaction tank. The inflow port is an opening formed in the inflow pipe, and opens substantially horizontally toward the center of the reaction vessel. The opening area of the inflow port was 0.15 m ² . The outlet was formed on the side of the reactor. The position of the outlet was set at the water level in the reaction tank.

都市 Municipal sewage was used as the wastewater used for the test. Drainage water and activated sludge were charged into the reaction tank and aerated and stirred for a predetermined time (biological treatment step). After the biological treatment step, the reaction tank was allowed to stand for a predetermined time (settling step). After the settling process, the wastewater is supplied to the inflow pipe, caused to flow down by gravity in the inflow pipe, supplied horizontally from the inlet into the biological sludge layer in the reaction tank, and discharged from the discharge port into the biologically treated water in the reaction tank. Was discharged (inflow / outflow step). The flow rate of the wastewater was set to 8 L / min per one inlet pipe, the flow rate per one inlet was set to about 3.2 m / h, and the drainage inflow rate was set to 100%. The above operation was performed for 200 days.

On the first, 31st, and 172th days of the operation, biological sludge in the reaction tank was collected, and the SVI of the biological sludge was measured. SVI is an index of sedimentation of biological sludge, and is determined by the following method. First, 1 L of sludge is put into a 1 L graduated cylinder, and the mixture is gently stirred so that the sludge concentration is as uniform as possible. Then, the sludge interface is measured after 5 minutes and 30 minutes of standing. Then, the volume ratio (%) of the sludge in the measuring cylinder is calculated. Next, the MLSS (mg / L) of the sludge is measured. These are applied to the following equation to calculate SVI5 and SVI30.
SVI (mL / g) = Volume ratio occupied by sludge × 10,000 / MLSS

On the first day of operation, SVI5 of the biological sludge was 221 mL / g, and SVI30 was 96 mL / g. Then, SVI5 of biological sludge was 46 mg / L, and SVI30 was 36 mg / L. From this result, a highly sedimentable biological sludge was obtained also by a water treatment method in which wastewater was introduced without using a pump.

When the BOD concentration of the wastewater before flowing into the reaction tank and the BOD concentration of the treated water discharged from the reaction tank three months after the start of operation were measured, the BOD concentration of the wastewater before flowing into the reaction tank was 103 mg / L. The BOD concentration was 19 mg / L. That is, since the BOD concentration of the treated water was about 18% of the BOD concentration of the wastewater, the BOD concentration remaining in the reaction tank after the inflow / outflow step was about 82% of the BOD concentration of the wastewater. It was confirmed that even in the water treatment method of supplying wastewater by gravity, the BOD concentration in the reaction tank could be efficiently increased.

(Example 2)
The following test was performed using the reaction tank shown in FIG. As the 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. The outlet was provided on the side opposite to one side of the reaction tank. The position of the outlet was set at the water level in the reaction tank.

ナ ト リ ウ ム Sodium bromide solution (40 mgBr / L) was used as waste water used in the test. Drainage and activated sludge were charged into the second chamber of the reaction tank and aerated and stirred for a predetermined time (biological treatment step). After the biological treatment step, the reaction tank was allowed to stand for a predetermined time (settling step). After the settling process, wastewater is supplied to the first chamber, and the biologically treated water in the second chamber is discharged from the discharge port while the wastewater is supplied horizontally from the inflow port into the biological sludge layer in the second chamber (inflow). / Discharge process). The flow rate of the wastewater was 0.6 m / h as a water area load, and the inflow / drainage process time was 32 minutes (the wastewater inflow amount was 150% of the effective volume of the water tank).

The bromine ion concentration in the reaction vessel after the inflow / outflow step was measured, and the residual bromine ion rate in the reaction vessel at the end of the inflow / outflow step was evaluated by the following equation. Table 1 shows the results. Since bromine ions are substances that are not easily affected by adsorption to biological sludge or biological reactions, if the residual ratio of bromine ions in the reaction tank shows a high value, the concentration of the target substance remaining in the reaction tank Is also high.
Bromine ion remaining rate = (bromine ion concentration in reaction tank / hydrogen ion concentration in wastewater) × 100

(Comparative Example 1)
The same reaction tank as in Example 2 was used except that a current plate was installed in the second chamber of the reaction tank. The current plate is a rectangular plate of 250 cm ² (120 mm × 208 mm), and a plurality of holes having a diameter of 4 mm are formed in the entire plate. The rectifying plate was horizontally installed at a position 6 mm above the bottom of the second chamber (a position higher than the inlet of the partition). That is, the wastewater (sodium bromide solution) flows into the lower part of the current plate in the second chamber from the inflow port, and is then supplied upward from the holes in the current plate. Furthermore, since the biological sludge layer formed by the sedimentation step is formed on the current plate, the wastewater is supplied from the holes into the biological sludge layer in an upward flow.

に お い て Similarly, in Comparative Example 1, the bromine ion concentration in the reaction tank after the inflow / discharge step was measured, and the bromine ion remaining rate in the reaction tank at the end of the inflow / discharge step was evaluated. Table 1 shows the results.

Comparative Example 1 had a bromine ion residual ratio of 70%, whereas Example 2 improved the bromine ion residual ratio to 82%. As described above, the embodiment in which the wastewater was supplied from the inlet into the biological treatment tank on the bottom of the reaction tank in the horizontal direction was compared with the comparative example in which the wastewater was supplied in the biological treatment tank in the upward flow, and Thus, it can be said that the concentration of the substance to be treated remaining in the reaction tank can be efficiently increased to the same level or more.

(Examples 3 and 4)
The following test was performed using the reaction tank shown in FIG. As the 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 reaction tank (a surface of 125 × 750). However, in Example 3, the outlet was provided on the side opposite to the side on which the inflow port was installed, and in Example 4, the outlet was provided on the same side as the side on which the inflow was installed. The positions of the outlets in Examples 3 and 4 were set at the water level in the reaction tank.

ナ ト リ ウ ム Sodium bromide solution (40 mgBr / L) was used as waste water used in the test. Drainage and activated sludge were charged into the reaction tank and aerated and stirred for a predetermined time (biological treatment step). After the biological treatment step, the reaction tank was allowed to stand for a predetermined time (settling step). After the sedimentation step, wastewater was supplied through the drainage 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 discharge port (inflow / drainage step). At that time, the flow rate of the wastewater at the inlet was changed and supplied within the range of the conditions shown in Table 2. The supply amount was 100% of the effective volume of the reaction tank. N in the table is a horizontal distance N (m) from the inlet to the side surface of the reaction tank facing the inlet.

(4) The bromine ion concentration in the reaction tank after the inflow / outflow step was measured, and the bromine ion remaining rate in the reaction tank at the end of the inflow / outflow step was evaluated by the above equation. FIG. 27 shows the result.

FIG. 27 is a diagram showing the results of the bromine ion residual ratio with respect to the flow velocity at the inlet in Examples 3 and 4. As shown in FIG. 27, the residual ratio of bromine ions was 50% or more under any of the conditions. Among the implemented conditions, the highest residual rate was obtained under the condition of a flow velocity of 37.8 cm / sec at the inlet. From the above, when the flow velocity v at the inlet is in the range of [N ^1/2 × 20] ≦ v ≦ [N ^1/2 × 80], the residual ratio of the substance to be treated in the wastewater in the inflow / outflow process is 50%. It was confirmed that this was the case. When the inlet and outlet were installed on the same side and the opposite side of the reaction tank, the condition where both were installed on the same side showed that the residual ratio of bromine ions was higher. It was confirmed that the discharge port was preferably installed on the same side.

(Example 5)
Next, a test was performed using the reaction tank shown in FIG. As the reaction tank, 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 lower part of the side of the reaction tank, and an outlet was installed on the same side as the side where the inlet was installed. The outlet was located at the surface of the water in the reactor. The test method was the same as that in Example 4 except that the flow velocity conditions at the inlet were as shown in Table 3.

結果 The results of the bromine ion residual ratio were 91% under the condition 7, 76% under the condition 8, and 86% under the condition 9, and the residual ratio was 70% or more in each case.

(Example 6)
The following granule formation test was performed using the reaction tank shown in FIG. As the 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 side surface of the reaction tank (125 × 220 surface). An outlet was provided on the side opposite to the side where the inlet was installed. The position of the outlet was set at the water level in the reaction tank. 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 introduced into the reaction tank as 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 influent water, and the BOD was 100 mg / L. In the inflow / outflow process, the simulated sewage was introduced from the inlet provided on the side of the reaction tank so as to come into contact with the sludge, and the flow rate at the inlet was set to the range of 11-28 cm / sec (v / N ^1/2 The value ranges from 23.5 to 60). The inflow amount of the wastewater in one inflow / outflow process was set to 100% of the effective volume of the reaction tank.

FIG. 28 shows the transition of SVI5 and SVI30 which are the sedimentation index of the sludge in the reaction tank. In addition, SVI5 is a sedimentation index of biological sludge, and is determined as follows. First, 1 L of sludge is put into a 1 L measuring cylinder, and after stirring, the sludge interface is measured when the sludge is allowed to stand for 5 minutes or 30 minutes. Then, the volume ratio (%) of the sludge in the measuring cylinder is calculated. Next, the MLSS (mg / L) of the sludge is measured. These are applied to the following equation to calculate SVI5 or SVI30. The smaller the value of SVI5 or SVI30, the higher the sedimentation property of the sludge.
SVI (mL / g) = Volume ratio occupied by sludge × 10,000 / MLSS

ＳAs shown in FIG. 28, no change was observed in SVI during the first 15 days of startup, and both SVI5 and SVI30 changed at 300-350 mL / g. Thereafter, a sharp decrease in SVI was confirmed, and formation of sludge having a good sedimentation property of 20 mL / g in both SVI5 and SVI30 was confirmed 35 days after startup.

Fig. 29 shows the input sludge and a photograph of the sludge observed 50 days after startup. Each bar indicates 500 μm. As shown in FIG. 29, the input sludge was composed of dispersed sludge, whereas the sludge after 50 days was composed of good granular sludge of about 200 to 300 μm.

1-7 water treatment apparatus, 10 reaction tank, 12, 12a, 12b inlet, 14 inlet pipe, 14a, 22a electromagnetic valve, 16 outlet, 17 partition wall, 18 blower, 20 diffuser pipe, 22 treated water discharge pipe, 24 Control device, 30 biological sludge layer, 32 treated water collection channel, 34, 42a, 42b raw water introduction pipe, 34a electromagnetic valve, 36 wastewater inflow trough, 38 treated water collection trough, 40 continuous biological treatment tank, 44 treated water supply Pipes, 44a, 46a valves, 46 biological sludge supply pipes, 48 treated water discharge pipes, 101-105 water treatment equipment, 110 reaction tanks, 110a, 110b long side walls, 110c, 110d short side walls, 110f first chamber, 110g 2nd room, 112 raw water introduction pipe, 113 distribution line, 114 raw water pump, 115 raw water pipe, 116 electricity Valve, 117 partition wall, 118 blower 120 diffusing pipe, 122 process water collection waterways, 124 controller, 126 an inlet, 128 outlet 130 biological sludge layer.

Claims (16)

An operation cycle including an inflow step of inflowing wastewater, a biological treatment step of biologically treating the wastewater with biological sludge, a sedimentation step of settling the biological sludge, and a discharge step of discharging the biologically treated biologically treated water. A water treatment method using a repeatedly performed reaction tank,
The reaction tank is provided with an inlet arranged at a position lower than an interface position of the biological sludge layer formed at the bottom of the reaction tank in the settling step, and an inflow portion extending vertically upward from the inlet. And
The water treatment method according to claim 1, wherein, in the inflow step, the wastewater is caused to flow down in the inflow portion by gravity, and supplied from the inflow port into the biological sludge layer. The water treatment method according to claim 1, wherein in the operation cycle, the discharging step is performed while the inflow step is performed. A sludge supply step of supplying biological sludge in the reaction tank to a continuous biological treatment tank for biological treatment with biological sludge while continuously flowing wastewater, and a treated water supply step of supplying biological treatment water in the reaction tank The water treatment method according to claim 1, further comprising at least one of the following. The method according to any one of claims 1 to 3, wherein, in the inflow step, the wastewater is caused to flow down in the inflow section by gravity, and is supplied from the inflow port into the biological sludge layer in a horizontal direction or below the horizontal direction. Or the water treatment method according to claim 1. In the operation cycle, while performing the inflow step, performing the discharge step,
The reaction vessel includes an outlet disposed at a water level in the reaction vessel,
The water treatment method according to claim 1, wherein the inflow port supplies at least a part of the wastewater in a horizontal direction into the biological sludge layer. The reaction tank is partitioned by a partition into a first chamber into which the wastewater is introduced and a second chamber for performing the operation cycle step,
The outlet is provided on the second chamber side, and is disposed at a water level in the second chamber,
The inflow port is provided in the partition so that the first chamber and the second chamber communicate with each other, and is located at a position lower than an interface position of a biological sludge layer formed in the bottom of the second chamber in the settling step. The water treatment method according to claim 5, wherein the wastewater is supplied in a horizontal direction into a biological sludge layer formed at the bottom of the second chamber. The water treatment method according to claim 5, wherein the reaction tank is a square water tank, and the inflow port and the discharge port are provided on the same surface of the square water tank. The flow velocity v (cm / sec) of the drainage water at the inlet and a horizontal distance N (m) from the inlet to the side surface of the reaction tank facing the inlet satisfy the following expression. The water treatment method according to any one of claims 5 to 7.
20 ≦ v / N ^1/2 ≦ 80 An operation cycle including an inflow step of inflowing wastewater, a biological treatment step of biologically treating the wastewater with biological sludge, a sedimentation step of settling the biological sludge, and a discharge step of discharging the biologically treated biologically treated water. A water treatment apparatus having a reaction tank that is repeatedly performed,
The reaction tank is provided with an inlet disposed at a position lower than the interface position of the biological sludge layer formed at the bottom of the reaction tank in the settling step, and an inflow portion extending vertically upward from the inlet. And
The water treatment apparatus according to claim 1, wherein, in the inflow step, the wastewater is caused to flow down in the inflow portion by gravity, and is supplied from the inflow port into the biological sludge layer. The water treatment apparatus according to claim 9, wherein, in the operation cycle, the discharging step is performed while the inflow step is performed. A sludge supply unit that supplies biological sludge in the reaction tank to a continuous biological treatment tank that performs biological treatment with biological sludge while continuously introducing wastewater, and a treated water supply unit that supplies biological treatment water in the reaction tank. The water treatment apparatus according to claim 9, further comprising at least one of the following. The water treatment apparatus according to any one of claims 9 to 11, wherein the inflow opening is opened in a horizontal direction or downward from the horizontal direction. In the operation cycle, while performing the inflow step, performing the discharge step,
The reaction tank has an outlet installed at a water level in the reaction tank,
The water treatment apparatus according to claim 9, wherein the inflow port supplies at least a part of the wastewater in the biological sludge layer in a horizontal direction. The reaction tank includes a partition that partitions the inside of the tank into a first chamber into which the wastewater 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 disposed at a water level in the second chamber,
The inflow port is provided in the partition so that the first chamber and the second chamber communicate with each other, and is located at a position lower than an interface position of a biological sludge layer formed in the bottom of the second chamber in the settling step. The water treatment apparatus according to claim 13, wherein the wastewater is horizontally supplied to a biological sludge layer formed at the bottom of the second chamber. The water treatment apparatus according to claim 13, wherein the reaction tank is a square water tank, and the inflow port and the discharge port are provided on the same surface of the square water tank. The flow velocity v (cm / sec) of the drainage water at the inlet and a horizontal distance N (m) from the inlet to the side surface of the reaction tank facing the inlet satisfy the following expression. The water treatment apparatus according to any one of claims 13 to 15.
20 ≦ v / N ^1/2 ≦ 80

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