Phosphorus-containing water treatment method and phosphorus-containing water treatment device

Abstract

Provided is a method for treating phosphorus-containing water, which is capable of recovering phosphorus removal performance as early as possible. This method for treating phosphorus-containing water is provided with: a continuous water-passing-type biological treatment step for biologically treating phosphorus-containing water with biological sludge while continuously flowing the phosphorus-containing water into a continuous biological treatment tank (14); a granular sludge formation step in which granular sludge is formed in the semi-batch biological treatment tank (12); and a sludge supply step for supplying the granular sludge formed in the semi-batch biological treatment tank (12) from a sludge supply pipe (40) to the continuous biological treatment tank (14), in which the amount of granular sludge supplied to the continuous biological treatment tank (14) is controlled on the basis of the phosphorus removal performance in the continuous biological treatment tank (14).

Description

Technical Field

[0001] The present invention relates to a method for treating phosphorus-containing water and a technique for a treatment apparatus for phosphorus-containing water. Background Art

[0002] Conventionally, in biological water treatment, the activated sludge method has been used, and this activated sludge method utilizes an aggregate of microorganisms (aerobic biological sludge) called flocs. In the activated sludge method, not only organic matter and nitrogen in water can be removed, but also phosphorus can be removed.

[0003] For example, Patent Document 1 discloses a wastewater treatment apparatus that includes a membrane separation device, and a partition plate is disposed above the membrane separation device. According to Patent Document 1, removal of nitrogen and phosphorus from sewage is disclosed.

[0004] In addition, Patent Document 2 discloses the following method: influent sewage is solid-liquid separated into separated water and separated sludge, the separated water is introduced into a biological treatment tank for treatment, the separated sludge is concentrated by a thickener, and the concentrated separated liquid containing organic matter is transferred to a biological reaction tank.

[0005] Furthermore, Patent Document 3 discloses the following method: intermittent aeration treatment is performed using a first aeration tank and a second aeration tank connected in series, thereby removing nitrogen and phosphorus in the wastewater.

[0006] Prior Art Documents Patent Documents Patent Document 1: Japanese Unexamined Patent Application Publication No. 2022-57310 Patent Document 2: Japanese Unexamined Patent Application Publication No. 2012-24725 Patent Document 3: Japanese Unexamined Patent Application Publication No. 9-94596 Summary of the Invention Technical Problem to be Solved by the Invention However, when biologically treating phosphorus-containing water, if the phosphorus concentration in the phosphorus-containing water fluctuates due to, for example, rainfall, there is a case where the phosphorus removal performance deteriorates, and in this case, there is a problem that it takes a long time until the phosphorus removal performance is restored.

[0007] Therefore, an object of the present invention is to provide a method for treating phosphorus-containing water and a treatment apparatus for phosphorus-containing water that can restore the phosphorus removal performance as soon as possible.

[0008] Technical Solution for Solving the Technical Problem The method for treating phosphorus-containing water of the present invention includes: a continuous water-flowing biological treatment step of biologically treating the phosphorus-containing water with biological sludge while continuously flowing the phosphorus-containing water into a continuous biological treatment tank; a granular sludge formation step of forming granular sludge; and a sludge supply step of supplying the granular sludge formed in the granular sludge formation step to the continuous biological treatment tank. In the sludge supply step, the supply amount of the granular sludge supplied to the continuous biological treatment tank is controlled based on the phosphorus removal performance in the continuous biological treatment tank.

[0009] In addition, in the method for treating phosphorus-containing water, preferably, the average daily supply amount of the granular sludge supplied to the continuous biological treatment tank is determined based on the phosphorus removal performance in the continuous biological treatment tank during a past given period and the average daily supply amount of the granular sludge supplied to the continuous biological treatment tank during the past given period.

[0010] In addition, in the method for treating phosphorus-containing water, preferably, when the phosphorus removal performance in the continuous biological treatment tank deteriorates or is assumed to deteriorate, the supply amount of the granular sludge supplied to the continuous biological treatment tank is increased compared to when the phosphorus removal performance in the continuous biological treatment tank is normal.

[0011] In addition, in the method for treating phosphorus-containing water, preferably, based on the phosphorus removal performance in the continuous biological treatment tank, the average daily supply amount of the granular sludge supplied to the continuous biological treatment tank is set to 0 to 20 times the average daily supply amount of the granular sludge supplied to the continuous biological treatment tank on the previous day.

[0012] In addition, the device for treating phosphorus-containing water of the present invention includes: a continuous biological treatment tank that biologically treats the phosphorus-containing water with biological sludge while continuously flowing the phosphorus-containing water into it; a granular sludge formation unit that forms granular sludge; a sludge supply unit that supplies the granular sludge formed by the granular sludge formation unit to the continuous biological treatment tank; and a control unit that controls the supply amount of the granular sludge supplied to the continuous biological treatment tank by the sludge supply unit based on the phosphorus removal performance in the continuous biological treatment tank.

[0013] In addition, in the device for treating phosphorus-containing water, preferably, the control unit determines the average daily supply amount of the granular sludge supplied to the continuous biological treatment tank based on the phosphorus removal performance in the continuous biological treatment tank during a past given period and the average daily supply amount of the granular sludge supplied to the continuous biological treatment tank during the past given period.

[0014] In addition, in the phosphorus-containing water treatment apparatus, preferably, when the phosphorus removal performance in the continuous biological treatment tank deteriorates or is assumed to deteriorate, the control unit increases the supply amount of the granular sludge supplied to the continuous biological treatment tank as compared with when the phosphorus removal performance in the continuous biological treatment tank is normal.

[0015] In addition, in the phosphorus-containing water treatment apparatus, preferably, the control unit sets the average daily supply amount of the granular sludge supplied to the continuous biological treatment tank to 0 to 20 times the average daily supply amount of the granular sludge supplied to the continuous biological treatment tank on the previous day, based on the phosphorus removal performance in the continuous biological treatment tank.

[0016] Advantages of the Invention According to the present invention, it is possible to provide a method for treating phosphorus-containing water and a phosphorus-containing water treatment apparatus that can restore the phosphorus removal performance at an early stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram showing an example of the structure of the phosphorus-containing water treatment apparatus according to the present embodiment.

[0018] Figure 2 is a graph showing the transition of the phosphorus concentration of the simulated wastewater, the phosphorus concentration of the treated water discharged from the continuous biological treatment tank, and the phosphoric acid phosphorus concentration in the anaerobic tank during the test period of the example. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described. It should be noted that the present embodiment is an example of implementing the present invention, and the present invention is not limited to the present embodiment.

[0020] Figure 1 is a schematic diagram showing an example of the structure of the phosphorus-containing water treatment apparatus according to the present embodiment. Figure 1 The shown phosphorus-containing water treatment apparatus 1 includes a raw water tank 10, a semi-batch biological treatment tank 12, a continuous biological treatment tank 14, a sedimentation tank 16, and a control device 18. Here, "continuous" in this specification is a mode relative to the batch mode, and is different from the semi-batch treatment in which the influent water, biological treatment, sedimentation of sludge, and discharge of treated water are performed in one tank, such as the semi-batch type. The phosphorus-containing water is continuously supplied to the continuous biological treatment tank 14, but this mode is not limited to the mode of continuously injecting the phosphorus-containing water into the tank for operation, and may also be a mode of supplying the phosphorus-containing water to the tank for operation using a pump such as a diaphragm pump that utilizes the principle of reciprocating motion, or a simulated continuous water supply mode in which the operation-stop of the pump is controlled according to the water level of the raw water tank 10 provided in the previous stage of the tank (the pump operates when the water level is high and stops when the water level is low), and the phosphorus-containing water is supplied to the tank.

[0021] Figure 1 The phosphorus-containing water treatment apparatus 1 shown includes raw water pipes (20a, 20b), a first treated water pipe 22, a second treated water pipe 24, a third treated water pipe 26, sludge return pipes (28a, 28b, 28c), a sludge discharge pipe 30, a raw water pump 32, sludge return pumps (34a, 34b), electromagnetic valves (36a, 36b, 36c, 36d, 36e), a valve 38, a sludge supply pipe 40, and a sludge supply pump 42.

[0022] One end of the raw water pipe 20a is connected to the raw water tank 10, and the other end is connected to the semi-batch biological treatment tank 12 via the raw water pump 32 and the electromagnetic valve 36a. In addition, one end of the raw water pipe 20b is connected to the raw water pipe 20a, and the other end is connected to the continuous biological treatment tank 14 via the electromagnetic valve 36b. One end of the first treated water pipe 22 is connected to the semi-batch biological treatment tank 12, and the other end is connected to the continuous biological treatment tank 14 via the electromagnetic valve 36e. One end of the second treated water pipe 24 is connected to the continuous biological treatment tank 14, and the other end is connected to the sedimentation tank 16. The third treated water pipe 26 is connected to the sedimentation tank 16. One end of the sludge return pipe 28a is connected to the continuous biological treatment tank 14, and the other end is connected to the semi-batch biological treatment tank 12 via the sludge return pump 34a. One end of the sludge discharge pipe 30 is connected to the sedimentation tank 16. One end of the sludge return pipe 28b is connected to the sludge discharge pipe 30, and the other end is connected to the continuous biological treatment tank 14 via the sludge return pump 34b and the electromagnetic valve 36c. One end of the sludge return pipe 28c is connected to the sludge return pipe 28b, and the other end is connected to the semi-batch biological treatment tank 12 via the electromagnetic valve 36d.

[0023] In addition, one end of the sludge supply pipe 40 is connected to the semi-batch biological treatment tank 12, and the other end is connected to the continuous biological treatment tank 14 via the sludge supply pump 42.

[0024] In Figure 1 In the phosphorus-containing water treatment apparatus 1 shown, the semi-batch biological treatment tank 12 functions as a granular sludge forming unit for forming granular sludge. In the semi-batch biological treatment tank 12, as described later, granular sludge is formed by performing an operation having an inflow process, a biological treatment process, a sedimentation process, and a discharge process. The granular sludge forming unit in the present embodiment is not limited to the semi-batch biological treatment tank 12 that performs an operation having an inflow process, a biological treatment process, a sedimentation process, and a discharge process, and may be a conventionally known device capable of forming granular sludge.

[0025] In Figure 1In the phosphorus-containing water treatment apparatus 1 shown, a sludge supply pipe 40 and a sludge supply pump 42 provided in the sludge supply pipe 40 function as a sludge supply unit, and the sludge supply pipe 40 and the sludge supply pump 42 supply the granular sludge formed in the semi-batch biological treatment tank 12 to the continuous biological treatment tank 14. It should be noted that a solenoid valve may be provided in the sludge supply pipe 40 as needed.

[0026] The control device 18 is composed of, for example, a microcomputer and an electronic circuit including a CPU for an arithmetic program, a ROM for storing a program and an arithmetic result, and a RAM, reads a given program stored in the ROM or the like, and executes the program to control the operation of the water treatment apparatus 1. The control device 18 is electrically connected to each pump and each solenoid valve by wire or wireless, for example, to control the operation of the pump and the opening and closing of the solenoid valve. In addition, the control device 18 functions as a control unit, and the control device 18 controls the supply amount of the granular sludge supplied to the continuous biological treatment tank 14 based on the phosphorus removal performance in the continuous biological treatment tank 14.

[0027] An example of the operation of the phosphorus-containing water treatment apparatus 1 of the present embodiment will be described. The phosphorus-containing water to be treated may contain not only phosphorus but also organic substances and the like. Examples of the phosphorus-containing water include drainage from food processing factories, chemical factories, semiconductor factories, mechanical factories, sewage, manure, and river water.

[0028] Using the control device 18, the water pump 32 to be treated is operated, and in addition, the solenoid valve 36b is opened, and the phosphorus-containing water in the raw water tank 10 is continuously supplied to the continuous biological treatment tank 14 through the water pipe 20a and 20b to be treated. In the continuous biological treatment tank 14, the phosphorus-containing water is biologically treated by the biological sludge in the tank (continuous water flow biological treatment process). In the continuous biological treatment tank 14, the phosphorus-containing water can be biologically treated under aerobic conditions or under anaerobic conditions. In addition, the continuous biological treatment tank 14 may be a biological treatment tank using the standard activated sludge method, but is not limited thereto. For example, from the viewpoint of effectively performing biological phosphorus removal, it may also be a biological treatment system using the AO method, A 2 O method, etc. (for example, a system composed of an anaerobic tank - aerobic tank, an anaerobic tank - anoxic tank - aerobic tank). In the case of the standard activated sludge method, from the viewpoint of biological phosphorus removal, an operation method of restricting the aeration amount in the upstream part of the continuous biological treatment tank 14 (simulated anaerobic-aerobic method) is preferred.

[0029] In the continuous biological treatment tank 14, the treated water after biological treatment is supplied from the second treated water pipe 24 to the sedimentation tank 16, and biological sludge is separated from the treated water. The treated water from which the biological sludge has been separated is discharged to the outside of the system through the third treated water pipe 26. The biological sludge accumulated at the bottom of the sedimentation tank 16 is discharged to the outside of the system through the sludge discharge pipe 30 when the valve 38 is opened; or when the sludge return pump 34b is operated by the control device 18 and the solenoid valves 36c or 36d are opened additionally, it is sent back to the continuous biological treatment tank 14 through the sludge return pipe 28b, or sent back to the semi-batch biological treatment tank 12 through the sludge return pipe 28c. Additionally, for example, the sludge return pump 34a can be operated by the control device 18 to send the biological sludge in the continuous biological treatment tank 14 back to the semi-batch biological treatment tank 12 through the sludge return pipe 28a.

[0030] When the semi-batch biological treatment tank 12 is operated, the solenoid valve 36a is opened by the control device 18, and a part of the phosphorus-containing water flows into the semi-batch biological treatment tank 12 from the water to be treated pipe 20a ((1) inflow process). After a given amount of phosphorus-containing water has flowed into the semi-batch biological treatment tank 12, the solenoid valve 36a is closed to stop the inflow process. Then, in the semi-batch biological treatment tank 12, the water to be treated is biologically treated with the biological sludge ((2) biological treatment process). For example, in the semi-batch biological treatment tank 12, under aerobic conditions, the organic matter in the phosphorus-containing water is oxidized and decomposed by aerobic biological sludge, or the nitrogen compounds are nitrified by biological sludge containing nitrifying bacteria, or under anaerobic conditions, the nitrogen compounds are denitrified by biological sludge containing denitrifying bacteria. It should be noted that if the biological treatment in the continuous biological treatment tank 14 is aerobic treatment, it is preferred that the biological treatment in the semi-batch biological treatment tank 12 is also aerobic treatment, and if the biological treatment in the continuous biological treatment tank 14 is anaerobic treatment, it is preferred that the biological treatment in the semi-batch biological treatment tank 12 is also anaerobic treatment.

[0031] After the biological treatment process has been carried out for a given time, the inside of the tank is made to be in a static state, and the biological sludge in the semi-batch biological treatment tank 12 is allowed to settle for a given time ((3) sedimentation process), and is separated into biological sludge and treated water. Then, the solenoid valve 36e is opened by the control device 18, and the supernatant water (treated water) in the semi-batch biological treatment tank 12 is discharged from the semi-batch biological treatment tank 12 ((4) discharge process) and supplied to the continuous biological treatment tank 14 through the first treated water pipe 22. By repeating the processes of (1) to (4) above, the biological sludge in the semi-batch biological treatment tank 12 is granulated to form granular sludge (granular sludge formation process). However, the treatment using the semi-batch biological treatment tank 12 is not limited to the method of separately carrying out the inflow process and the discharge process as described above, and the discharge process can be carried out simultaneously with the inflow process. Figure 1Taking the water treatment apparatus 1 as an example, the control device 18 is used to open the solenoid valve 36a and the solenoid valve 36e, so that a part of the phosphorus-containing water flows from the water to be treated pipe 20a into the semi-batch biological treatment tank 12, and the treated water in the semi-batch biological treatment tank 12 is discharged to the first treated water pipe 22 ((1) inflow process / discharge process). After a given time, the solenoid valve 36a and the solenoid valve 36e are closed, and in the semi-batch biological treatment tank 12, the phosphorus-containing water is biologically treated with biological sludge ((2) biological treatment process). After the biological treatment process, the inside of the tank is in a static state, and the biological sludge in the semi-batch biological treatment tank 12 is allowed to settle for a given time ((3) sedimentation process), and is separated into biological sludge and treated water. By repeating the processes of (1) to (3) above, the biological sludge in the semi-batch biological treatment tank 12 is granulated to form granular sludge (granular sludge formation process). The granular sludge formed in the semi-batch biological treatment tank 12 refers to self-granulated sludge. For example, it refers to biological sludge in which the average particle size of the sludge is 0.2 mm or more and the proportion of sludge with a particle size of 0.2 mm or more is 40% or more. It should be noted that the particle size of the granular sludge can be measured by, for example, a laser diffraction particle size measuring device, a sieve, etc.

[0032] In Figure 1 the water treatment apparatus 1, the treated water discharged from the semi-batch biological treatment tank 12 is supplied from the first treated water pipe 22 into the continuous biological treatment tank 14, but it is not limited thereto. For example, it can be directly discharged outside the system without being supplied to the continuous biological treatment tank 14, or it can be supplied to the sedimentation tank 16.

[0033] In addition, in Figure 1 the water treatment apparatus 1, the control device 18 operates the sludge supply pump 42, and the granular sludge formed in the semi-batch biological treatment tank 12 is supplied from the sludge supply pipe 40 to the continuous biological treatment tank 14 (sludge supply process). In this sludge supply process, based on the phosphorus removal performance in the continuous biological treatment tank 14, the supply amount of the granular sludge supplied to the continuous biological treatment tank 14 is controlled. For example, the control device 18 controls the operation of the sludge supply pump 42 so that when the phosphorus removal performance in the continuous biological treatment tank 14 deteriorates, the supply amount of the granular sludge from the semi-batch biological treatment tank 12 to the continuous biological treatment tank 14 increases compared to the normal time before the deterioration of the phosphorus removal performance. In addition, the control device 18 can also control the operation of the sludge supply pump 42 so that in the continuous biological treatment tank 14, after the phosphorus removal performance is restored (that is, when the phosphorus removal performance is normal), the supply amount of the granular sludge decreases compared to when the phosphorus removal performance deteriorates. Regarding the supply amount of the granular sludge, it is preferably to increase or decrease the supply amount of the granular sludge per day on average, but it is not limited thereto.

[0034] Thus, by controlling the supply amount of granular sludge from the semi-batch biological treatment tank 12 to the continuous biological treatment tank 14 based on the phosphorus removal performance in the continuous biological treatment tank 14, even when the phosphorus removal performance in the continuous biological treatment tank 14 deteriorates, the phosphorus removal performance in the continuous biological treatment tank 14 can be restored as early as possible. The mechanism for exerting the above effect is not very clear, but it is speculated as follows.

[0035] Phosphorus in the phosphorus-containing water is treated by bacteria with a high phosphorus accumulation ability contained in the sludge (hereinafter referred to as phosphorus-accumulating bacteria). For example, phosphorus-accumulating bacteria excrete phosphorus while taking in organic matter under anaerobic conditions, and remove phosphorus from the phosphorus-containing water by taking in more phosphorus than the excreted amount under aerobic conditions. Usually, a large number of phosphorus-accumulating bacteria exist in the granular sludge. In particular, in the semi-batch biological treatment tank 12, since the conditions required for the phosphorus-accumulating bacteria to excrete and take in phosphorus can be created in the biological treatment process, it is considered that more phosphorus-accumulating bacteria exist in the granular sludge formed in the semi-batch biological treatment tank 12. In particular, by setting the aerobic conditions using aeration in the biological treatment process, more phosphorus-accumulating bacteria can exist in the granular sludge. In addition, the average particle size of the granular sludge is large (for example, 0.2 mm or more), and the center of the granular sludge becomes anaerobic. Therefore, compared with ordinary activated sludge, the granular sludge is an environment in which phosphorus-accumulating bacteria can easily release and take in phosphorus.

[0036] However, the deterioration of phosphorus removal performance usually becomes significant when the phosphorus concentration of the phosphorus-containing water decreases due to rainfall or the like. This is because the amount of phosphorus excreted by the phosphorus-accumulating bacteria in the tank decreases, and the phosphorus removal activity of the phosphorus-accumulating bacteria decreases. Therefore, if the phosphorus concentration of the phosphorus-containing water decreases, there is a case where the phosphorus removal performance in the continuous biological treatment tank 14 deteriorates. On the other hand, in the semi-batch biological treatment tank 12, as described above, since it is an environment where phosphorus-accumulating bacteria are likely to exist, even if the phosphorus concentration of the phosphorus-containing water decreases, the impact on the phosphorus removal performance is slight, and granular sludge with high phosphorus removal activity can be formed. Therefore, when the phosphorus removal performance in the continuous biological treatment tank 14 deteriorates due to a change in the phosphorus concentration in the phosphorus-containing water, compared with the normal situation before the deterioration of the phosphorus removal performance, by increasing the supply amount of granular sludge from the semi-batch biological treatment tank 12 to the continuous biological treatment tank 14, the phosphorus removal performance in the continuous biological treatment tank 14 can be restored as early as possible. After the phosphorus removal performance in the continuous biological treatment tank 14 is restored, it is preferable to reduce the supply amount of granular sludge compared with when the phosphorus removal performance deteriorates.

[0037] The judgment of the phosphorus removal performance in the continuous biological treatment tank 14 can be made, for example, based on the phosphorus concentration in the treated water. In Figure 1In the phosphorus-containing water treatment apparatus 1, for example, a phosphorus concentration sensor is provided in the second treated water pipe 24, and the phosphorus concentration in the treated water passing through the second treated water pipe 24 is measured by the phosphorus concentration sensor. Moreover, when the phosphorus concentration measured by the phosphorus concentration sensor is below a predetermined reference value, the control device 18 determines that the phosphorus removal performance is normal, and when the phosphorus concentration measured by the phosphorus concentration sensor exceeds the predetermined reference value, the control device 18 determines that the phosphorus removal performance has deteriorated, and controls the supply amount of the granular sludge as described above.

[0038] In addition, for the judgment of the phosphorus removal performance in the continuous biological treatment tank 14, for example, from the viewpoint of being able to quickly grasp the phosphorus removal performance in the continuous biological treatment tank 14, it is preferably judged based on the oxidation-reduction potential (hereinafter, ORP) at a given position in the continuous biological treatment tank 14, or based on the anaerobic discharge concentration of phosphorus. Regarding the measurement point of ORP, it is preferable to first grasp the ORP curve in the continuous biological treatment tank 14 in a state where phosphorus removal is carried out well (for example, the phosphoric acid phosphorus concentration in the treated water is 1 mgP / L or less, or the removal rate of all phosphorus is 90% or more), and set it at the position where the ORP is the lowest. Then, when the ORP measured at the above-mentioned position is below a given reference value, the control device 18 determines that the phosphorus removal performance is normal; when the ORP measured at the above-mentioned position exceeds the given reference value, the control device 18 determines that the phosphorus removal performance has deteriorated, and controls the supply amount of the granular sludge as described above. It should be noted that when the continuous biological treatment tank 14 is equipped with an anaerobic tank, the ORP in the anaerobic tank can also be measured. In addition, regarding the measurement point of the anaerobic discharge concentration of phosphorus, it is preferable to first grasp the curve of the phosphoric acid phosphorus concentration in the continuous biological treatment tank 14 in a state where phosphorus removal is carried out well, and set it at the position where the phosphoric acid phosphorus concentration is the highest (that is, the position where the increase in phosphorus concentration caused by the discharge of phosphorus is the highest). Then, when the phosphoric acid phosphorus concentration measured at the above-mentioned position exceeds a given reference value, the control device 18 determines that the phosphorus removal performance is normal, and when the phosphoric acid phosphorus concentration measured at the above-mentioned position is below the given reference value, the control device 18 determines that the phosphorus removal performance has deteriorated, and controls the supply amount of the above-mentioned particles. It should be noted that when the continuous biological treatment tank 14 is equipped with an anaerobic tank, the phosphoric acid phosphorus concentration in the anaerobic tank can also be measured.

[0039] In addition, in Figure 1In the phosphorus-containing water treatment apparatus 1 shown, the control device 18 can also control the operation of the sludge supply pump 42 so that when the phosphorus removal performance in the continuous biological treatment tank 14 is assumed to deteriorate, the supply amount of granular sludge from the semi-batch biological treatment tank 12 to the continuous biological treatment tank 14 increases compared to before the phosphorus removal performance is assumed to deteriorate (compared to normal). The deterioration of the phosphorus removal performance can also be assumed, for example, based on the precipitation forecast in the weather forecast. For example, the control device 18 communicates with a weather information server of an organization that processes meteorological information such as a meteorological bureau via a wired or wireless communication network to obtain the future precipitation forecast in the area where the phosphorus-containing water to be treated is discharged. Moreover, when the rainfall amount from the original time to a given time later (for example, 1 hour later) in the obtained precipitation forecast exceeds a preset reference value, the control device 18 assumes that the phosphorus removal performance deteriorates and increases the supply amount of granular sludge. By such control, it is possible to prevent the deterioration of the phosphorus removal performance of the continuous biological treatment tank 14 in advance and perform stable phosphorus treatment.

[0040] When the phosphorus removal performance in the continuous biological treatment tank 14 deteriorates or is assumed to deteriorate, the supply amount of granular sludge supplied to the continuous biological treatment tank 14 is preferably increased to more than twice the supply amount of granular sludge in the normal state, or preferably increased so that the proportion of granular sludge in the continuous biological treatment tank 14 in the normal state increases by more than 4%.

[0041] The average daily supply amount of granular sludge supplied to the continuous biological treatment tank 14 is preferably determined based on the phosphorus removal performance in the continuous biological treatment tank 14 during a past given period (the past given period is a past given period starting from the present (for example, one week)) and the average daily supply amount of granular sludge supplied to the continuous biological treatment tank 14 during the past given period. For example, when the phosphorus removal performance was good and the average daily supply amount of granular sludge did not change during the past week, the supply of granular sludge to the continuous biological treatment tank may not be performed. The daily supply amount of granular sludge is preferably 0.2% or more with respect to the sludge amount in the continuous biological treatment tank 14. In order to further stabilize the phosphorus removal performance, it is more preferably supplied so that the occupancy rate of granular sludge in the sludge in the continuous biological treatment tank 14 is 2% or more.

[0042] Regarding the average daily supply amount of granular sludge supplied to the continuous biological treatment tank 14, for example, from the viewpoint of suppressing the deterioration of the sludge properties in the continuous biological treatment tank 14, it is preferably set to 0 to 20 times the average daily supply amount of granular sludge supplied to the continuous biological treatment tank 14 the previous day based on the phosphorus removal performance in the continuous biological treatment tank 14. For example, when the phosphorus removal performance in the continuous biological treatment tank 14 deteriorates or is envisaged to deteriorate, the average daily supply amount of granular sludge supplied to the continuous biological treatment tank 14 is preferably set in the range of 1 time or more and 20 times or less the average daily supply amount of granular sludge supplied to the continuous biological treatment tank the previous day, and more preferably set in the range of 2 times or more and 20 times or less. In addition, for example, when the phosphorus removal performance in the continuous biological treatment tank 14 is normal, the average daily supply amount of granular sludge supplied to the continuous biological treatment tank 14 is preferably set to 0 times or more and 1 time or less the average daily supply amount of granular sludge supplied to the continuous biological treatment tank 14 the previous day. Such a setting is performed by the control device 18, for example.

[0043] After increasing the supply amount of granular sludge supplied to the continuous biological treatment tank 14, when the phosphorus removal performance in the continuous biological treatment tank 14 shows a tendency to recover, the supply amount of granular sludge can be restored. For example, in the continuous biological treatment tank 14, the increased amount of granular sludge is continuously supplied until an increase in the concentration of phosphoric acid phosphorus measured at the above measurement point is confirmed. Then, when an increase in the concentration of phosphoric acid phosphorus is confirmed, it is assumed that the phosphorus removal performance tends to recover, and the supply amount of granular sludge is restored. The judgment of the recovery tendency of the phosphorus removal performance is not limited to the concentration of phosphoric acid phosphorus. For example, it can be the above ORP, or the phosphorus concentration in the treated water.

[0044] The MLSS concentration of the semi-batch biological treatment tank 12 is preferably operated in the range of 2000 to 20000 mg / L. In addition, in order to maintain the soundness (settling property, activity, etc.) of the biological sludge, it is preferably maintained at an appropriate sludge load, and preferably the granular sludge is withdrawn from the tank in such a way that it is maintained in the range of 0.05 to 0.60 kgBOD / MLSS / day, and more preferably maintained in the range of 0.1 to 0.5 kgBOD / MLSS / day.

[0045] In the process of forming granular sludge using the semi-batch biological treatment tank 12, it is preferable to appropriately control the management of the sedimentation time and the drainage inflow rate per batch. The sedimentation time of the biological sludge is calculated based on the distance from the water surface to the target sludge interface position and the sedimentation rate of the biological sludge. For example, it can be set between 4 minutes / m and 15 minutes / m, or it can also be set between 5 minutes / m and 10 minutes / m. In addition, the drainage inflow rate (the ratio of the inflow water to the effective volume during the reaction) can be, for example, in the range of 20% or more and 120% or less, or it can also be in the range of 40% or more and 120% or less.

[0046] The pH in the semi-batch biological treatment tank 12 is preferably adjusted to the range of 6 to 9 suitable for general biological treatment, and more preferably adjusted to the range of 6.5 to 7.5. When the pH value is outside the above range, it is preferable to adjust the pH using an acid or a base. The dissolved oxygen (DO) in the semi-batch biological treatment tank 12 is preferably set to 0.5 mg / L or more suitable for general biological treatment, and more preferably set to 1 mg / L or more.

[0047] In the continuous biological treatment tank 14, for example, it can be a method of performing biological treatment using the standard activated sludge method, or it can be a system such as the A2O method (Anaerobic - Anoxic - Oxic Process) or the AO method (Anaerobic - Oxic Process) (a system provided with an anaerobic treatment tank and an anoxic treatment tank), or it can also be a device for performing biological treatment using a system such as the oxidation ditch method or the discontinuous supply type multi-step activated sludge method. In addition, in the presence of carriers such as polyurethane, plastic, and resin, it can be a device for performing biological treatment.

[0048] The continuous biological treatment tank 14 is preferably operated in a range where the sludge concentration in the tank is, for example, 2000 to 20000 mg / L. In addition, in order to maintain the soundness (sedimentation property, activity, etc.) of the biological sludge, the sludge load is preferably set to the range of 0.05 to 0.6 kgBOD / MLSS / day, and more preferably set to the range of 0.1 to 0.5 kgBOD / MLSS / day.

[0049] In the present embodiment, as the solid-liquid separation device for separating biological sludge from the treated water, a sedimentation tank 16 is used, but it is not limited thereto. For example, it can also be a pressurized floating device, a filtration device, a membrane separation device, etc.

[0050] Examples Hereinafter, examples are given to more specifically illustrate the present invention, but the present invention is not limited to the following examples.

[0051] Use Figure 1The shown device is used for simulated drainage treatment. The simulated drainage uses simulated sewage (organic matter concentration: 100 - 150 mg / L, total phosphorus concentration: 4 - 6 mg / L) with skipjack extract and peptone as the main components. The continuous biological treatment tank uses a system of the AO method composed of an anaerobic tank and an aerobic tank.

[0052] The volume load of the continuous biological treatment tank is set to 0.4 - 0.7 kg / (m 3 ·d), the SRT of the continuous biological treatment tank is set to 20 days, and the simulated drainage is continuously passed through the continuous biological treatment tank. The return sludge from the sedimentation tank to the continuous biological treatment tank has a flow rate of 30% of the flow rate of the simulated drainage. In addition, as the initial input sludge of the continuous biological treatment tank, floating activated sludge is used. In addition, the granular sludge formed by the semi-batch biological treatment tank is supplied to the continuous biological treatment tank at an average daily amount of 0.24 g, and the presence rate of the granules is 2.3% relative to the sludge in the continuous biological treatment tank.

[0053] Figure 2 It is a graph showing the changes in the phosphorus concentration of the simulated drainage, the phosphorus concentration of the treated water discharged from the continuous biological treatment tank, and the phosphate phosphorus concentration in the anaerobic tank during the test period of the example. However, Figure 2 It shows the concentration changes after the 644th day after the start of water passing. From the 644th day to the 653rd day after the start of continuous water passing of the simulated drainage, the phosphate phosphorus concentration in the anaerobic tank changes at a value close to twice the phosphorus concentration in the simulated drainage. In addition, the phosphorus concentration in the treated water changes at a low concentration. It should be noted that although not shown in the figure, the ORP in the anaerobic tank during this period changes within the range of -150 mV to -200 mV. For two days starting from the 654th day after the start of continuous water passing of the simulated drainage, the supply of the simulated drainage is stopped, and instead well water (organic matter concentration: 0 mg / L, total phosphorus concentration: 0 mg / L) is continuously passed through. When the continuous passing of well water into the continuous biological treatment tank starts, the phosphate phosphorus concentration in the anaerobic tank drops sharply and becomes 0 mg / L on the 2nd day after the start of well water passing. It should be noted that although not shown in the figure, the ORP in the anaerobic tank during this period rises to 0 mV - 90 mV.

[0054] When the concentration of phosphorus in phosphorus in the anaerobic tank decreases to 0 mg / L, the supply of well water is stopped, continuous water flow of simulated drainage is restarted, and the average daily supply amount of granular sludge supplied to the continuous biological treatment tank is increased to twice (0.48 g). Due to the restart of the continuous water flow of simulated drainage, the phosphorus concentration in the treated water temporarily rises to 5.8 mg / L, and the phosphorus removal performance of the continuous biological treatment tank deteriorates. However, by continuously supplying the increased amount of granular sludge, the phosphorus concentration in the treated water rapidly decreases to below 1 mg / L thereafter. After the phosphorus concentration in the treated water decreases to below 1 mg / L, the average daily supply amount of granular sludge supplied to the continuous biological treatment tank is restored to 0.24 g, but the phosphorus concentration in the treated water also remains below 1 mg / L thereafter.

[0055] The recovery rate of phosphorus removal performance shown in the examples is a result that cannot be obtained when the supply amount of granular sludge is not increased and is continuously supplied in a normal amount.

[0056] Reference numeral description 1 Phosphorus-containing water treatment device, 10 Raw water tank, 12 Semi-batch biological treatment tank, 14 Continuous biological treatment tank, 16 Sedimentation tank, 18 Control device, 20a, 20b Treated water pipe, 22 First treated water pipe, 24 Second treated water pipe, 26 Third treated water pipe, 28a to 28c Sludge return pipe, 30 Sludge discharge pipe, 32 Treated water pump, 34a, 34b Sludge return pump, 36a to 36e Electromagnetic valve, 38 Valve, 40 Sludge supply pipe, 42 Sludge supply pump.

Claims

1. A method for treating phosphorus-containing water, characterized in that: The method for treating phosphorus-containing water comprises: A continuous water flow biological treatment process, in which the phosphorus-containing water is continuously flowed into a continuous biological treatment tank while the phosphorus-containing water is biologically treated using biological sludge; a granular sludge forming step for forming granular sludge; and a sludge supplying step of supplying the granular sludge formed in the granular sludge forming step to the continuous biological treatment tank, In the sludge supply step, the amount of granular sludge supplied to the continuous biological treatment tank is controlled based on the phosphorus removal performance in the continuous biological treatment tank.

2. The method for treating phosphorus-containing water according to claim 1, characterized in that: The average daily supply amount of the granular sludge to the continuous biological treatment tank is determined based on the phosphorus removal performance in the continuous biological treatment tank during a given past period and the average daily supply amount of the granular sludge to the continuous biological treatment tank during the given past period.

3. The method for treating phosphorus-containing water according to claim 1, characterized in that: When the phosphorus removal performance in the continuous biological treatment tank deteriorates or is expected to deteriorate, the amount of the granular sludge supplied to the continuous biological treatment tank is increased compared to when the phosphorus removal performance in the continuous biological treatment tank is normal.

4. The method for treating phosphorus-containing water according to claim 1, characterized in that: Based on the phosphorus removal performance in the continuous biological treatment tank, the average daily supply amount of the granular sludge to the continuous biological treatment tank is set to 0 to 20 times the average daily supply amount of the granular sludge to the continuous biological treatment tank on the previous day.

5. A treatment device for phosphorus-containing water, characterized in that: The phosphorus-containing water treatment device comprises: A continuous biological treatment tank that allows phosphorus-containing water to flow continuously and biologically treats the phosphorus-containing water using biological sludge; a granular sludge forming unit, which forms granular sludge; a sludge supply unit that supplies the granular sludge formed by the granular sludge forming unit to the continuous biological treatment tank; as well as A control unit controls the amount of granular sludge supplied from the sludge supply unit to the continuous biological treatment tank based on the phosphorus removal performance in the continuous biological treatment tank.

6. The phosphorus-containing water treatment device according to claim 5, characterized in that: The control unit determines an average daily supply amount of the granular sludge to the continuous biological treatment tank based on the phosphorus removal performance in the continuous biological treatment tank during a given past period and an average daily supply amount of the granular sludge to the continuous biological treatment tank during the given past period.

7. The phosphorus-containing water treatment device according to claim 5, characterized in that: When the phosphorus removal performance in the continuous biological treatment tank deteriorates or is expected to deteriorate, the control unit increases the amount of the granular sludge supplied to the continuous biological treatment tank compared to when the phosphorus removal performance in the continuous biological treatment tank is normal.

8. The phosphorus-containing water treatment device according to claim 5, characterized in that: The control unit sets the average daily supply amount of the granular sludge to the continuous biological treatment tank to 0 to 20 times the average daily supply amount of the granular sludge to the continuous biological treatment tank on the previous day based on the phosphorus removal performance in the continuous biological treatment tank.

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