JP3656267B2 - Dephosphorization device - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a dephosphorization apparatus for removing ammonium ions and orthophosphate ions contained in water to be treated (drainage).
[0002]
[Prior art]
There is a dephosphorization device as a device for removing ammonium ions (NH ₄ ⁺ ) and orthophosphate ions (HPO ₄ ²⁻ ) contained in water to be treated (drainage).
[0003]
As shown in FIG. 4, this dephosphorization apparatus introduces waste water into a reaction vessel a through an introduction port g at the bottom, and adds magnesium ions (Mg ²⁺ ) that are insufficient in the waste water into the vessel a. PH is adjusted by injecting an alkaline agent such as NaOH, and a reaction of Mg ²⁺ + NH ₄ ⁺ + HPO ₄ ² + OH ⁻ + 6H ₂ O → MgNH ₄ PO ₄ .6H ₂ O + H ₂ O occurs while blowing air. Thus, NH ₄ ⁺ and HPO ₄ ^2- in the waste water are simultaneously removed and dephosphorization is performed. The treated liquid rises in the container a and is discharged from the large diameter part (sedimentation part) c having the draft tube b through the outlet d. The draft tube b is for preventing the liquid in the sedimentation section c from being disturbed by the injected air, that is, the air is guided into the draft tube b and the liquid in the sedimentation section c outside the tube b. It is exhausted without disturbing.
[0004]
In addition, a pipe f for returning a part of the liquid (treated water) in the sedimentation section c to the bottom of the reaction vessel a by a circulation pump e is provided, whereby the concentration of NH ₄ ⁺ and HPO ₄ ^{2− in} the waste water is high. In particular, in order to improve the treatment efficiency, in particular, a part of the treated water is circulated by using the pipe f and the circulation pump e so that the concentration of HPO ₄ ²⁻ is not more than a certain concentration and mixed with the waste water. Yes.
[0005]
[Means for Solving the Problems]
The dephosphorization apparatus of the present invention introduces water to be treated containing ammonium ions and orthophosphate ions from the bottom, blows air into the water to precipitate MgNH ₄ PO ₄ in the presence of magnesium ions, and performs dephosphorization treatment. In the dephosphorization apparatus provided with a reaction vessel for discharging the treated water from above, a gas recovery device for collecting rising air is provided in the reaction vessel, and a gas-liquid separation tank is provided above the reaction vessel, The gas recovery device and the gas-liquid separation tank are connected by a riser pipe, a downcomer pipe that faces the lower side of the gas recovery apparatus is connected to the gas-liquid separation tank, and the gas recovery apparatus is recovered by the riser pipe A part of the treated water in the gas recovery device is raised to the gas-liquid separation tank by the rising force of the air, and the air is separated from the liquid raised in the gas-liquid separation tank, and the apparent specific gravity is heavy in the downcomer Liquid It is obtained by constituting the circulating means for returning the lower reaction vessel is lowered.
[0006]
Therefore, the present invention has been made in view of such circumstances, and an object of the present invention is to provide a dephosphorization apparatus that can reduce the installation area and save energy by eliminating the need for a circulation pump.
[0007]
[Means for Solving the Problems]
The dephosphorization apparatus of the present invention introduces water to be treated containing ammonium ions and orthophosphate ions from the bottom, blows air into the water to precipitate MgNH ₄ PO ₄ in the presence of magnesium ions, and performs dephosphorization treatment. In the dephosphorization apparatus provided with the reaction vessel for discharging the treated water from the upper part, a gas recovery device for recovering the rising air is provided in the reaction vessel, and the treatment is performed by the rising force of the air recovered by the gas recovery device. A circulating means is provided for raising a part of the water, separating the air from the raised liquid, and lowering the liquid whose apparent specific gravity is heavy and returning it downward in the reaction vessel.
[0008]
[Action]
The water to be treated is introduced into the reaction vessel from the bottom, and while air is blown into the water, ammonium ions and orthophosphate ions in the waste water are removed in the presence of magnesium ions, and the water to be treated is dephosphorized ( Mg ²⁺ + NH ₄ ⁺ + HPO ₄ ²⁻ + OH ⁻ + 6H ₂ O → MgNH ₄ PO ₄ .6H ₂ O + H ₂ O). This liquid rises with the air in the container and reaches the gas recovery device, where the air is recovered and a part is discharged from the upper part. The remainder rises due to the ascending force of the air collected by the gas recovery device, and after rising, the air is separated, the apparent specific gravity becomes heavier, and is returned to the lower part in the reaction vessel and circulated. In this way, since the treated water is circulated using the ascending force of the air, a circulation pump is not required and energy saving can be achieved. Further, since air is recovered by the gas recovery device, the inside of the reaction vessel at the upper part of the gas recovery device is not disturbed by air and can be effectively used as a sedimentation part. Since the pipe for circulating the treated water disposed in the settling portion is smaller in diameter than the draft tube, the effective diameter of the settling portion can be increased, so that the diameter of the settling portion can be reduced, Therefore, it is possible to reduce the space and area.
[0009]
【Example】
Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
[0010]
In FIG. 1, reference numeral 1 denotes a reaction vessel. The reaction vessel is formed in a bowl shape with a bottomed cylinder and the top is sealed.
[0011]
The bottom of the reaction vessel 1 is provided with an inlet 4 to which a drain pipe 3 having a raw water pump 2 for supplying water to be treated (drainage) containing ammonium ions and orthophosphate ions is connected. The overflow weir 5 overflows the treated water, and an overflow pipe 6 for discharging the treated water is connected to the overflow weir 5.
[0012]
Below the inside of the reaction vessel 1, a water distributor 7 is provided for uniformly distributing the wastewater introduced from the inlet 4 into the vessel 1. The water distribution device 7 can uniformly distribute the wastewater into the container 1, and has an umbrella structure, for example. Below the water distributor 7, an air blowing portion 8 for dispersing air in the container 1 is provided, and an air supply pipe 10 having a blower 9 having a variable air supply amount is connected to the air blowing portion 8. The interior of the container 1 is agitated by the air dispersed from the air blowing section 8.
[0013]
In addition, an alkali tube 12 having a variable flow rate pump 11 for supplying an alkaline agent such as NaOH is connected below the reaction vessel 1, and the pH in the vessel 1 becomes a pH condition in which MgNH ₄ PO ₄ is precipitated. Thus, for example, NaOH is injected appropriately (for example, so that the pH in the container 1 becomes a predetermined value) so as to be 7.7 to 9.5, preferably 8.1. Also, below the reaction vessel 1, a variable flow rate pump for supplying a magnesium salt solution in which magnesium is ionized in an aqueous solution such as magnesium chloride (MgCl ₂ ), magnesium acetate, magnesium hydroxide or the like containing magnesium ions. 13 is connected, and when magnesium is insufficient for precipitation of MgNH ₄ PO ₄ (for example, ammonium ions (NH ₄ ⁺ ) or orthophosphate ions (HPO ₄ ² contained in the treated water from the vessel). ^-) is to be equal to or less than the predetermined value) so that the MgCl ₂ solution is injected.
[0014]
A gas recovery device 15 is provided above the center of the reaction vessel 1 so as to partition the vessel 1 up and down into a settling portion 1a and a reaction portion 1b where MgNH ₄ PO ₄ precipitates and granulates. The gas recovery device 15 recovers air blown from the air blowing section 8 and may have any structure as long as it can recover air. For example, a gas-solid-liquid separator having the same structure as the three-phase separator used in the UASB method or a similar structure may be used. The gas-solid liquid separation apparatus collects air and settles MgNH ₄ PO ₄ particles rising with the air to separate the air, MgNH ₄ PO ₄ particles and waste water into gas-solid liquid. For example, as shown in FIGS. 2 and 3, the gas hood 16 is provided in one stage or two stages in the illustrated example so that the rising air is guided into the gas hood 16, and one end of each gas hood 16 is provided. A gas inlet 18 is provided so that the air accumulated in the hood 16 is guided to the gas recovery unit 17, and the air collected and recovered from the gas inlet 18 to the gas recovery unit 17 is discharged to the air pipe 19. The structure to be made may be sufficient. In this way, the air is collected by the gas hood 16 and then flows into the gas collecting unit 17 where it is collected and then flows into the air pipe 19. At this time, the MgNH ₄ PO ₄ particles that have risen as the air rises collide with the inner surface of the gas hood 16 and settle.
[0015]
As shown in FIG. 1, the gas recovery device 15 is connected to a riser pipe 20 through which the liquid in the gas recovery device 15 (or a liquid containing MgNH ₄ PO ₄ particles) flows as an upward flow by the recovered air, This ascending pipe 20 is connected to a gas-liquid separation tank 21 provided above the reaction vessel 1. The gas-liquid separation tank 21 separates air from the liquid introduced from the ascending pipe 20, and a part of the treated water is conveyed to the gas-liquid separation tank 21 by using the lift effect of the air. In the tank 21, vigorous stirring occurs.
[0016]
An air inflow pipe 22 into which separated air flows is connected to the upper portion of the gas-liquid separation tank 21, and an air trap 23 is interposed in the air inflow pipe 22, and a small amount of internal pressure is contained in the gas-liquid separation tank 21. It has come to take. In addition, a lower pipe 24 is connected to the lower part of the gas-liquid separation tank 21, and the liquid in which the apparent specific gravity is increased due to the separation of air flows downward. The outlet of the lower pipe 24 is connected to the reaction vessel 1. Ru is disposed between the water distributor 7 and the air blower unit 8 of the inner. The ascending pipe 21, the gas-liquid separation tank 22 and the descending pipe 24 constitute a circulation means 25, and the liquid in the gas-liquid separation tank 21 is returned downward in the reaction vessel 1, that is, a part of the treated water is circulated. It has become. Further, the reaction vessel 1 is connected to a discharge pipe (not shown) for discharging MgNH ₄ PO ₄ particles that have become large in the reaction unit 1b, and the increased amount of MgNH ₄ PO ₄ particles in the reaction unit 1a is appropriately discharged. It has come to be.
[0017]
Next, the operation of this embodiment will be described.
[0018]
Waste water containing ammonium ions and orthophosphate ions is introduced into the reaction vessel 1 from the introduction port 4 and is uniformly distributed in the vessel 1 by the water distributor 7, and then rises in the reaction unit 1 b. The reaction vessel 1, insufficient when the pH in the vessel 1 with NaOH is injected as MgNH ₄ PO ₄ is the pH for precipitation, insufficient magnesium ions to deposition of MgNH ₄ PO ₄ An amount of MgCl ₂ solution to be injected is injected, and air is dispersed from the air blowing section 8 to sufficiently agitate the inside of the reaction section 1b. As a result, a reaction of Mg ²⁺ + NH ₄ ⁺ + HPO ₄ ² + OH ⁻ + 6H ₂ O → MgNH ₄ PO ₄ .6H ₂ O + H ₂ O occurs, and NH ₄ ⁺ and HPO ₄ ²⁻ in the waste water are simultaneously removed. Waste water is dephosphorized. The produced MgNH ₄ PO ₄ adheres to the surface of the MgNH ₄ PO ₄ particles and is granulated. The treated water rises and is discharged to the outflow pipe 6 through the gas recovery device 15, the settling part 1 a, and the overflow weir 5.
[0019]
Since the air blown from the air blowing unit 8 is collected in the gas recovery device 15, since there is no turbulence due to air in the settling portion 1 a on the upper side of the gas recovery device 15, the whole can be effectively used as the settling portion 1 a. it can. Pipes for circulating the treated water (rising pipe 20 and descending pipe 24) disposed in the settling portion 1a may be smaller in diameter than the draft tube (see FIG. 4). Thus, since the effective diameter of the sedimentation part 1a can be taken, the internal diameter of the sedimentation part 1a is the same as the internal diameter of the reaction part 1b, or only needs to be expanded a little, and the space and area for installation can be reduced. . At this time, if the gas recovery device 15 is a gas-solid-liquid separation device, the inflow of the solid content (MgNH ₄ PO ₄ particles) into the sedimentation section 1a is further suppressed, so that treated water containing almost no solid content can be obtained. It will be discharged from the reaction vessel 1.
[0020]
Further, a part of the liquid (or liquid containing MgNH ₄ PO ₄ particles) in the gas recovery device 15 rises in the ascending pipe 20 by the ascending force of the air recovered by the gas recovery device 15, and the gas-liquid separation tank 21. In the gas-liquid separation tank 21, vigorous agitation occurs, and the air that has raised the liquid is separated from the liquid. The separated air enters the air inflow pipe 22 and is released to the atmosphere through the air trap 23. The liquid whose apparent specific gravity is increased due to the separation of the air in the gas-liquid separation tank 21 descends in the downcomer 24 and is returned between the water distributor 7 and the air blowing unit 8 through the discharge port. Circulate and mix. At this time, since a small amount of internal pressure is applied to the gas-liquid separation tank 21 by the air trap 23 of the air inflow pipe 22, water flows into the reaction vessel 1 from the separation tank 21 with a strong stirring force. Thereby, circulation and mixing of treated water can be performed without a circulation pump, and energy saving can be achieved. Moreover, the circulation of the treated water, and the phosphorus concentration in the reaction portion 1b lowered, because the degree of supersaturation of MgNH ₄ PO ₄ is lowered, since MgNH ₄ PO ₄ is precipitated only on the surface of MgNH ₄ PO ₄ particles, MgNH ₄ PO ₄ particles become large. For this reason, MgNH ₄ PO ₄ particles and treated water can be efficiently separated.
[Brief description of the drawings]
In short, according to the present invention, there is an excellent effect that the installation area can be reduced and energy saving can be achieved.
FIG. 1 is a configuration diagram showing an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing an example of a gas-solid-liquid separator.
3 is a perspective view showing a main part of the gas-solid-liquid separator shown in FIG.
FIG. 4 is a configuration diagram showing an example of a conventional dephosphorization apparatus.
[Explanation of symbols]
1 Reaction vessel 15 Gas recovery device 25 Circulation means

Claims (1)

Water to be treated containing ammonium ions and orthophosphate ions is introduced from the bottom, air is blown into this to deposit MgNH ₄ PO ₄ in the presence of magnesium ions, dephosphorization treatment, and this treated water is discharged from the top. In a dephosphorization apparatus equipped with a reaction vessel
A gas recovery device for recovering rising air is provided in the reaction vessel,
A gas-liquid separation tank is provided above the reaction vessel, the gas recovery device and the gas-liquid separation tank are connected by an ascending pipe, and a downcomer pipe facing the gas recovery apparatus is connected to the gas-liquid separation tank Then, with the riser pipe, a part of the treated water in the gas recovery device is raised to the gas-liquid separation tank by the rising force of the air recovered by the gas recovery apparatus, and from the liquid raised in the gas-liquid separation tank A dephosphorization apparatus comprising a circulation means for separating air and lowering a liquid whose apparent specific gravity is increased by the downcomer pipe and returning the liquid downward in the reaction vessel.

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