JP7144999B2 - Water treatment method and water treatment equipment - Google Patents

Description

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

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

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

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

In addition, Patent Document 5 describes a semi-batch type in which three processes are repeatedly performed: (1) inflow of wastewater and discharge of treated water, (2) biological treatment of substances to be treated, and (3) sedimentation of biological sludge. A biological treatment method is disclosed.

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

By the way, in the wastewater inflow process in semi-batch type biological treatment, it is common to use a pump to supply wastewater from the bottom of the tank. There is a demand for a more efficient method of inflowing wastewater.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a water treatment method and a water treatment apparatus capable of flowing wastewater into a reaction tank with a simple structure that does not use a pump.

The present invention comprises 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 discharging step of discharging the biologically treated water. A water treatment method using a reaction tank that repeats an operation cycle having a An inflow port and an inflow portion extending vertically upward from the inflow port are provided, and in the inflow step, the waste water is caused to flow down the inflow portion by gravity and is supplied from the inflow port into the biological sludge layer. In the water treatment method, the reaction tank is provided with at least two inlets, and the inlets provided in the at least two inlets face the same direction .

In the operation cycle in the water treatment method, it is preferable to perform the discharge step while performing the inflow step.

In the water treatment method, a sludge supply step of supplying the biological sludge in the reaction tank to a continuous biological treatment tank in which wastewater is continuously inflowed and biologically treated with biological sludge, and biologically treated water in the reaction tank. It is preferable to include at least one of the treated water supply steps for supplying the

Preferably, in the inflow step of the water treatment method, the wastewater is caused to flow downward in the inflow section by gravity, and is supplied horizontally or below the horizontal direction into the biological sludge layer from the inflow port.

The present invention comprises 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 discharging step of discharging the biologically treated water. A water treatment apparatus comprising a reaction tank for repeating an operation cycle with An inflow port and an inflow portion extending vertically upward from the inflow port are provided, and in the inflow step, the waste water is caused to flow down the inflow portion by gravity and is supplied from the inflow port into the biological sludge layer. At least two inlets are provided in the reaction tank, and the inlets provided in the at least two inlets face the same direction .

In the operation cycle of the water treatment apparatus, it is preferable to perform the discharge process while performing the inflow process. .

In the water treatment apparatus, a sludge supply unit that supplies the biological sludge in the reaction tank to a continuous biological treatment tank that performs biological treatment with biological sludge while continuously inflowing wastewater, and biologically treated water in the reaction tank. It is preferable to include at least one of the treated water supply units that supply the

In the water treatment device, it is preferable that the inlet is open in the horizontal direction or downward from the horizontal direction.

ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the water-treatment method and water-treatment apparatus which can flow into a reaction tank by the simple structure which does not use a pump.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic cross section which shows an example of the water treatment apparatus which concerns on this embodiment. (A) to (C) are schematic top views of a reaction vessel for explaining an arrangement example of an inflow pipe. FIG. 4 is a schematic cross-sectional view showing an example of the state of the water treatment device during the 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. FIG. 4 is a schematic cross-sectional view showing an example of the state of the water treatment device during the sedimentation process; FIG. 4 is a schematic cross-sectional view showing an example of the state of the water treatment device during the 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 block diagram which shows another example of the water treatment apparatus of this embodiment.

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

FIG. 1 is a schematic cross-sectional view showing an example of a water treatment device according to this embodiment. As shown in FIG. 1 , the water treatment apparatus 1 includes a reaction tank 10 , an air diffuser having a blower 18 and an air diffuser pipe 20 , a treated water discharge pipe 22 and a control device 24 .

The reaction tank 10 is provided with an inflow port 12 and an inflow pipe 14 through which waste water flows into the tank. The inflow pipe 14 is an inflow part extending vertically upward from the inflow port 12 . As used herein, a vertically extending inlet includes a substantially vertically extending inlet. A substantially vertical direction includes directions 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 inflow port 12 is arranged at a position lower than the interface position of the biological sludge layer formed on the bottom of the reaction tank 10 in the sedimentation process, which will be described later. Note that the inlet 12 shown in FIG. 1 is provided at the lower end of the inlet pipe 14 and opens in the horizontal direction.

FIGS. 2A to 2C are schematic top views of a reaction vessel for explaining an arrangement example of inflow pipes. Although the number of inflow pipes 14 provided with inflow ports 12 is not particularly limited, it is desirable to have a plurality of them in order to increase the diffusibility of waste water. Taking a rectangular reaction tank as an example, the inflow pipes 14 provided with the inflow ports 12 are, for example, at least two locations on the diagonal of the reaction tank 10 as shown in FIG. At least two locations on opposite sides of the reaction vessel 10 as shown in , or at least two locations on the same side of the reaction vessel as shown in FIG. desirable.

Further, the reaction tank 10 is provided with a discharge port 16 for discharging the treated water that has been 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 .

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

The control device 24 is composed of, for example, a CPU for computing programs, a microcomputer composed of a ROM and a RAM for storing programs and computation results, and electronic circuits, etc., and has a function of controlling the opening and closing of the air diffuser and electromagnetic valves. have.

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

FIG. 3 is a schematic cross-sectional view showing an example of the state of the water treatment device during the inflow process. The electromagnetic valve 14 a is opened by the controller 24 , and the waste water flows down the inflow pipe 14 by gravity and is supplied from the inflow port 12 into the reaction vessel 10 . The inflow port 12 is arranged at a position lower than the interface level of the biological sludge layer 30 formed by the sedimentation process described later, and is open in the horizontal direction. Therefore, as shown in FIG. It is fed 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 apparatus during the biological treatment process. When the water level of the waste water in the reaction tank 10 reaches a predetermined level by the inflow process, the control device 24 closes the electromagnetic valve 14a and operates the blower 18 . Thereby, as shown in FIG. 4, the aeration gas is supplied from the air diffuser 20 into the reaction tank 10, and the waste water and biological sludge in the reaction tank 10 are agitated. Then, the wastewater in the reaction tank 10 is biologically treated with biological sludge (biological treatment process), and the substances to be treated (for example, organic matter, etc.) in the wastewater are decomposed.

FIG. 5 is a schematic cross-sectional view showing an example of the state of the water treatment apparatus during the sedimentation process. After the biological treatment process has been carried out for a predetermined period of time, the controller 24 stops the operation of the blower 18 to stop agitation and aeration of the waste water in the reaction tank 10 . As a result, as shown in FIG. 5, the biological sludge is settled (settling step), and a 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 device during the discharge process. After the sedimentation process is carried out for a predetermined time and the biological sludge layer 30 is formed on the bottom of the reaction tank 10, the control device 24 opens the electromagnetic valve 22a, and as shown in FIG. , the biologically treated water is discharged from the discharge port 28 to the treated water discharge pipe 22 (discharge step). The treated water is discharged out of the system of the water treatment apparatus 1 through the treated water discharge pipe 22 . After performing the discharge process for a predetermined time, the process returns to the above-described inflow process.

As described above, in the water treatment apparatus 1 shown in FIG. 1, an operation cycle is performed that repeats the four processes of the inflow process, the biological treatment process, the sedimentation process, and the discharge process. It is flowing into 10. That is, in the water treatment apparatus 1 shown in FIG. 1, it is possible to allow wastewater to flow in with a simple configuration that does not use a pump, so for example, an increase in running costs such as equipment costs and operation management costs can be suppressed. In particular, it is considered that by applying the water treatment apparatus 1 of this embodiment as a water treatment apparatus for large-scale treatment facilities, it is possible to effectively reduce facility costs and operation and management costs.

Here, it is believed that extracellular matrix (EPS) produced by bacteria influences the formation of highly sedimentary biological sludge (for example, granulated biological sludge) in the operation cycle. In order to form the EPS, it is important to form a concentration gradient of the substance to be treated that is biologically treated within the reaction tank 10 . For example, when biologically treating organic matter in wastewater, it is important to form a concentration gradient of organic matter, and when biologically treating nitrogen-containing substances such as ammonium nitrogen and nitrate nitrogen, It is important to form a concentration gradient of Then, the concentration gradient of the substance to be treated is obtained by, for example, increasing the concentration of the substance to be treated in the reaction tank 10 (satiated state) in the inflow process, and by consuming the substance to be treated in the reaction tank 10 in the biological treatment process. , is formed by lowering the concentration of the substance to be treated in the reaction tank 10 (starvation state). In this 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. As a result, in the present embodiment, unnecessary consumption of the target substances in the waste water is suppressed in the inflow process, and the concentration of the target substances remaining in the reaction tank 10 can be efficiently increased. Therefore, it is possible to increase the concentration gradient of the substance to be treated in the reaction tank 10 . As a result, it becomes possible to form biological sludge with high sedimentation properties, and as a result, it becomes possible to improve the biological treatment rate.

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

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

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

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

The flow velocity of the inflow port 12 in the inflow step is appropriately set depending on the structure, size, etc. of the reaction vessel 10, and is not particularly limited. It is preferably 10 cm/sec or more and 100 cm/sec or less. If the flow velocity of the inflow port 12 is less than 1 cm/sec, the wastewater and biological sludge do not come into efficient contact with each other, so the concentration of the substances to be treated remaining in the tank during the inflow process may decrease. In addition, when the flow velocity of the inlet 12 is higher than 200 cm/sec, the inside of the reaction tank is excessively agitated, and the sedimented sludge floats again, preventing efficient contact between waste water and biological sludge. In some cases, the sludge does not progress, or resuspended biological sludge flows out from 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 a position lower than the interface position of the biological sludge layer 30 formed on the bottom of the reaction tank 10 in the sedimentation process. Assuming that the effective water depth is 2 m to 8 m and that the interface height of the biological sludge layer 30 is 10% to 50% of the height of the reaction tank 10, the inflow port 12 is at the height of the reaction tank 10. It is preferably installed at a height of 4 m or less from the bottom, more preferably at a height of 2 m or less, and even more preferably at a height of 1 m or less.

The inflow rate of the waste water is preferably in the range of, for example, 10% or more and 200% or less. The inflow rate of waste water is the ratio of the inflow amount of waste water in one cycle of operation to the effective volume in the reaction tank 10 . By setting the inflow rate of wastewater within the above range, it is possible to further increase the concentration of the substances to be treated remaining in the reaction tank 10 in the inflow process, and to form highly sedimentary biological sludge more efficiently. It becomes possible.

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

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

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

The shape of the reaction vessel 10 is not limited to the rectangular shape shown in FIG. 2, and may be, for example, a cylindrical shape. Rectangular reaction tanks are employed, for example, in large-scale treatment plants such as sewage treatment plants.

The operation cycle of this embodiment may have an inflow process, a biological treatment process, a sedimentation process, and a discharge process, and an operation cycle that repeats the four processes of the above-described inflow process, biological treatment process, sedimentation process, and discharge process. In addition, it also includes an operation cycle in which the three processes of the inflow process and the discharge process (hereinafter referred to as the inflow/discharge process), the biological treatment process, and the sedimentation process are repeated. A water treatment apparatus that performs the latter operation cycle will be described below.

FIG. 7 is a schematic cross-sectional view showing another example of the water treatment device according to this embodiment. In the water treatment apparatus 2 in FIG. 7, the same reference numerals are assigned to the same components as in the water treatment apparatus 1 in FIG. 1, and the description thereof will be omitted. In the water treatment device 2 shown in FIG. 7, a discharge port 16 is provided on one side 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 this embodiment, as will be described later, the water level in the reaction tank 10 does not substantially fluctuate because the treated water is discharged together with the inflow of the waste water. Moreover, the water treatment apparatus 2 shown in FIG. The treated water collection channel 32 communicates with the inside of the reaction tank 10 through the outlet 16 provided in the reaction tank 10 .

An example of the operation of the water treatment device 2 of this embodiment will be described below.

The electromagnetic valve 14 a is opened by the controller 24 , and the waste water flows through the inflow pipe 14 and into the reaction vessel 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 diffusion pipe 20 into the reaction tank 10, and the waste water and biological sludge in the reaction tank 10 are agitated. Then, the wastewater in the reaction tank 10 is biologically treated with biological sludge (biological treatment process), and the substances to be treated (for example, organic matter, etc.) in the wastewater are decomposed. After the biological treatment process has been carried out for a predetermined period of time, the controller 24 stops the operation of the blower 18 to stop agitation and aeration of the waste water in the reaction tank 10 . 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 process is carried out for a predetermined time and the biological sludge layer 30 is formed on the bottom of the reaction tank 10, the electromagnetic valve 14a is opened by the control device 24, and the waste water flows through the inflow pipe 14 by gravity. The biologically treated water that has been biologically treated in the reaction tank 10 is discharged from the outlet 16 to the treated water collecting channel 32 (inflow/discharge step). Treated water is discharged out of the system of the water treatment apparatus 1 from the treated water collection channel 32 . After performing the inflow/discharge process for a predetermined time, the process returns to the biological treatment process.

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

FIG. 8 is a schematic cross-sectional view showing another example of the water treatment device of this embodiment. In the water treatment device 3 shown in FIG. 8, the same reference numerals are assigned to the same components as in the water treatment device 1 shown in FIG. 1, and the description thereof will be omitted. The water treatment device 3 shown in FIG. 8 has a partition wall 17 . The partition wall 17 is erected vertically in the reaction tank 10 and partitions the inside of the reaction tank 10 into a first chamber 10f and a second chamber 10g. Below the partition wall 17, there is provided an opening that communicates the first chamber 10f and the second chamber 10g, and the opening serves as the inflow port 12 described above. The first chamber 10f partitioned by the partition wall 17 serves as an inflow portion extending vertically upward from the inflow port 12, and the second chamber 10g partitioned by the partition wall 17 serves as the above operation cycle (inflow step, biological treatment step). , sedimentation process, discharge process).

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

The shape of the opening (inflow port 12) provided in the partition wall 17 is not particularly limited, and may be rectangular, circular, elliptical, or the like. One or more openings (inflow ports 12 ) may be formed in the partition wall 17 .

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

FIG. 9 is a schematic cross-sectional view showing another example of the water treatment apparatus of this embodiment. In the water treatment device 4 shown in FIG. 9, the same reference numerals are assigned to the same components as in the water treatment device 1 shown in FIG. 1, and the description thereof is omitted. In the water treatment apparatus 4 shown in FIG. 9 , an inlet 12 is provided on the side of the reaction tank 10 , and an inlet pipe 14 extending vertically upward from the inlet 12 is arranged outside the reaction tank 10 . Thus, the inflow pipe 14 may be provided outside the reaction vessel 10 .

10 to 12 are schematic cross-sectional views showing another example of the water treatment apparatus of this 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. In the water treatment device 5 shown in FIG. 10, an inflow port 12a is formed at the lower end of the inflow pipe 14 . The inlet 12a shown in FIG. 10 is open vertically downward, and waste water is supplied vertically downward from the inlet 12a into the biological sludge layer. In addition, in the water treatment device 5 shown in FIG. 11, the inflow port 12b is formed at two locations on the side surface of the inflow pipe 14. As shown in FIG. Each inflow port 12b shown in FIG. 11 is opened in the horizontal direction, and waste water is horizontally supplied into the biological sludge layer from each inflow port 12b. Further, in the water treatment device 5 shown in FIG. 12, the inflow pipe 14 has two inflow ports 12a and 12b formed at the lower end and the side surface thereof. The inlet 12a at the lower end shown in FIG. 12 opens in the vertical direction, the inlet 12b on the side opens in the horizontal direction, and the waste water flows vertically into the biological sludge layer from the inlet 12a at the lower end. and horizontally into the biological sludge layer from the side inlet 12b.

At least one inflow port may be provided for each inflow pipe, but two or more are preferably provided as shown in FIGS. . The opening direction of the inlet is not particularly limited, but is preferably horizontal or below the horizontal, as shown in FIGS. That is, the waste water is preferably supplied horizontally or below the horizontal direction into the biological sludge layer from the inlet.

FIG. 13(A) is a schematic cross-sectional view showing another example of the water treatment apparatus of this embodiment, and FIG. 13(B) is a schematic top view showing another example of the water treatment apparatus of this embodiment. be. In the water treatment device 6 shown in FIG. 13, the same reference numerals are assigned to the same components as in the water treatment device 1 shown in FIG. 1, and the description thereof will be omitted. In addition, in FIG. 13(B), an air diffusion device including the blower 18 and the air diffusion pipe 20 and the control device 24 are omitted. The water treatment apparatus 6 shown in FIG. 13 includes a wastewater inflow trough 36 which is provided above the reaction tank 10 and extends in a substantially horizontal direction, and a treated water collection trough which is provided at the water level in the reaction tank 10 and extends in a substantially horizontal direction. 38. A plurality of inflow pipes 14 are connected to the wastewater inflow trough 36 . Inflow ports 12 a and 12 b are formed at the lower end and side surfaces of the inflow pipe 14 .

The water treatment device 6 shown in FIG. 13 performs an operation cycle that repeats an inflow/discharge process, a biological treatment process, and a sedimentation process. Specifically, in the inflow/discharge process, wastewater flows from each wastewater inflow trough 36 into each inflow pipe 14, flows down the inflow pipe 14 due to gravity, and enters the biological sludge layer from the inflow ports (12a, 12b). , the biologically treated water in the reaction tank 10 overflows the treated water collecting trough 38 and is discharged out of the reaction tank 10 from the treated water collecting trough 38 . After the inflow/exhaust process, the biological treatment process and sedimentation process described above are carried out.

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

FIG. 14 is a schematic configuration diagram showing another example of the water treatment apparatus of this embodiment. A 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 of the present embodiment, and the specific configuration is as described above, so a description thereof will be omitted. A water treatment apparatus 7 shown in FIG. 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 portion). The raw water introduction pipe 42 b 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 . 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 . A treated water discharge pipe 48 is connected to the continuous biological treatment tank 40 .

Waste water flowing through the raw water introduction pipe 42 a is supplied to the reaction tank 10 , and waste water flowing through the raw water introduction pipe 42 b is supplied to the continuous biological treatment tank 40 . In the reaction tank 10, the operation cycle described above (inflow process (inflow/discharge process), biological treatment process, sedimentation process, and discharge process) is performed. By opening the valve 46 a at an arbitrary timing, the biological sludge with high sedimentation properties formed in the reaction tank 10 is supplied from the biological sludge supply pipe 46 to the continuous biological treatment tank 40 . Moreover, the treated water in the reaction tank 10 is supplied from the treated water supply pipe 44 to the continuous biological treatment tank 40 by opening the valve 44 a at an arbitrary timing. 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 in from the raw water introduction pipe 42b and treated water from the reaction tank 10 The wastewater flowing appropriately through the supply pipe 44 is biologically treated. By supplying the highly sedimentary biological sludge formed in the reaction tank 10 to the continuous biological treatment tank 40 in this manner, the biological treatment speed of the continuous biological treatment tank 40 can be improved, for example.

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

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

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

Further, on the 1st, 31st and 172nd days of operation, the biological sludge in the reaction tank was sampled and the SVI of the biological sludge was measured. SVI is a sedimentation index of biological sludge, and is obtained by the following method. First, 1 L of sludge is put into a 1 L graduated cylinder, gently stirred so that the sludge concentration becomes as uniform as possible, and then the sludge interface is measured after 5 minutes and 30 minutes of standing still. Then, the volume ratio (%) occupied by the sludge in the graduated cylinder is calculated. Next, the MLSS (mg/L) of the sludge is measured. These are applied to the following formulas to calculate SVI5 and SVI30.
SVI (mL/g) = volume ratio of sludge x 10,000/MLSS

On the first day of operation, the SVI5 of the biological sludge was 221 mL/g and the SVI30 was 96 mL/g. In the biological sludge, SVI5 was 46 mg/L and SVI30 was 36 mg/L. From these results, it was found that biological sludge with high sedimentation property was obtained even by a water treatment method in which waste water was introduced without using a pump.

Three months after the start of operation, 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 were measured. BOD concentration was 19 mg/L. That is, since the treated water BOD concentration was about 18% of the wastewater BOD concentration, the BOD concentration remaining in the reactor after the inflow/discharge process was about 82% of the wastewater BOD concentration. As can be seen, it was confirmed that the BOD concentration in the reaction tank could be efficiently increased even with the water treatment method in which waste water is supplied by gravity.

1 to 7 water treatment equipment, 10 reaction tank, 12, 12a, 12b inlet, 14 inlet pipe, 14a electromagnetic valve, 16 outlet, 17 partition, 18 blower, 20 air diffuser, 22 treated water discharge pipe, 22a electromagnetic valve , 24 control device, 28 outlet, 30 biological sludge layer, 32 treated water collecting channel, 34, 42a, 42b raw water introduction pipe, 34a electromagnetic valve, 36 wastewater inflow trough, 38 treated water collecting trough, 40 continuous biological treatment Tank, 44 treated water supply pipe, 44a, 46a valve, 46 biological sludge supply pipe, 48 treated water discharge pipe.

Claims (8)

An operation cycle having an inflow step for inflowing wastewater, a biological treatment step for biologically treating the wastewater with biological sludge, a sedimentation step for settling the biological sludge, and a discharge step for discharging the biologically treated biologically treated water. A water treatment method using a reaction tank that is repeatedly performed,
The reaction tank is provided with an inlet arranged at a position lower than the interface position of the biological sludge layer formed at the bottom of the reaction tank in the sedimentation step, and an inlet extending vertically upward from the inlet. be
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 ;
The water treatment method , wherein the reaction tank is provided with at least two inlets, and the inlets provided in the at least two inlets face the same direction . 2. The water treatment method according to claim 1, wherein the discharge step is performed while the inflow step is performed in the operation cycle. A sludge supply step of supplying the biological sludge in the reaction tank to a continuous biological treatment tank in which wastewater is continuously inflowed and biologically treated with the biological sludge, and a treated water supply step of supplying the biologically treated water in the reaction tank. The water treatment method according to claim 1 or 2, comprising at least one of 4. The method according to any one of claims 1 to 3, wherein in the inflow step, the wastewater is caused to flow downward in the inflow portion by gravity, and is supplied from the inflow port horizontally or downwardly into the biological sludge layer. 1. The water treatment method according to 1. An operation cycle having an inflow step for inflowing wastewater, a biological treatment step for biologically treating the wastewater with biological sludge, a sedimentation step for settling the biological sludge, and a discharge step for discharging the biologically treated biologically treated water. A water treatment apparatus comprising a repetitive reaction tank,
The reaction tank is provided with an inlet arranged at a position lower than the interface position of the biological sludge layer formed at the bottom of the reaction tank in the sedimentation step, and an inlet extending vertically upward from the inlet. be
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 ;
A water treatment apparatus , wherein the reaction tank is provided with at least two inlets, and the inlets provided in the at least two inlets face the same direction . 6. The water treatment apparatus according to claim 5, wherein in the operation cycle, the discharge process is performed while the inflow process 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 inflowing wastewater, and a treated water supply unit that supplies biologically treated water in the reaction tank. The water treatment device according to claim 5 or 6, comprising at least one of 8. The water treatment apparatus according to any one of claims 5 to 7, wherein the inlet opens in the horizontal direction or downward from the horizontal direction.

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