JP2929910B2 - Method for treating phosphorus-containing water - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating phosphorus-containing water, and more particularly, to a method in which phosphorus-containing water discharged from a sewage treatment apparatus is passed through a dephosphorizing agent packed bed mainly composed of iron hydroxide. The present invention relates to a method for treating phosphorus-containing water for adsorbing and removing phosphorus, in which phosphorus-containing water is treated to restore the function of the phosphorus-removing agent having reduced phosphorus removal performance.

[0002]

2. Description of the Related Art In closed water areas such as the Seto Inland Sea, Lake Biwa, and Kasumigaura in recent years, the deterioration of water quality due to the eutrophication phenomenon has further progressed, and obstacles to water use have increased, which has become a major social problem. The causative substances are said to be nitrogen and phosphorus, and in particular, the removal of phosphate ions from wastewater is an important issue to be resolved immediately.

[0003] Conventionally, as a method for removing phosphorus from water, there has been a method using a dephosphorizing agent containing iron hydroxide (iron oxyhydrate) as a main component, and various types of dephosphorizing agents have been proposed. This method utilizes the phenomenon that iron hydroxide adsorbs phosphorus in water, and is generally carried out by passing phosphorus-containing water through a dephosphorization tower or dephosphorization tank filled with a granular dephosphorizing agent. Have been.

[0004]

The use of a dephosphorizing agent causes a decrease in the dephosphorization performance over time. It is necessary to replace the dephosphorizing agent with reduced dephosphorization performance with a new dephosphorizing agent.

[0005] However, there has not been proposed any method for restoring the function of a dephosphorizing agent having a reduced dephosphorizing performance.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional circumstances, and restores the function of a phosphorus-removing agent by treating phosphorus-containing water and backwashing the phosphorus-removing agent having reduced phosphorus-removing performance. An object of the present invention is to provide a method for treating phosphorus-containing water, which improves the dephosphorization efficiency and reduces the dephosphorization cost by effectively reusing the backwash wastewater obtained at this time.

[0007]

According to a first aspect of the present invention, there is provided a method for treating phosphorus-containing water, wherein the phosphorus-containing water discharged from the sewage treatment apparatus is passed through a dephosphorizing agent packed layer mainly composed of iron hydroxide. In the method for treating phosphorus-containing water for adsorbing and removing phosphorus, the function of the phosphorus-removing agent is restored by treating the phosphorus-containing water and backwashing the phosphorus-removing agent having reduced phosphorus-removing performance. The separated matter is returned to the sewage treatment apparatus, and the sewage in the sewage treatment apparatus is dephosphorized.

[0008] The method for treating phosphorus-containing water according to claim 2 is the method for treating phosphorus-containing water according to claim 1, wherein the dephosphorizing agent is backwashed with dephosphorized water, and the backwash wastewater containing the exfoliated product is treated as follows. The raw water tank, the flow control tank, the contact aeration tank, the aeration tank, the sedimentation tank, the sludge concentration tank, and the sludge concentration storage tank of the sewage treatment apparatus are fed to the tank or its inflow pipe.

That is, as a result of various studies on the backwashing of the dephosphorizing agent, the present inventor has found that the dephosphorizing agent causes a very small amount of exfoliation on its surface due to the mechanical impact applied during the backwashing, and thus the phosphorus adsorbing ability is reduced. It has been found that a surface having a new surface has newly appeared to restore the phosphorus adsorption performance, and that the exfoliated product formed at this time still has some phosphorus removal performance. Then, the present inventors completed studies on the recovery of the function of the dephosphorizing agent by this backwashing and the effective use of the exfoliated material having the dephosphorizing performance, and completed the present invention.

It is important that the dephosphorizing agent mainly composed of iron hydroxide used as the dephosphorizing agent in the present invention has such a strength that a part of the surface is peeled off by backwashing.

Although there is no particular limitation on such a dephosphorizing agent, it is preferable that the present applicant has previously filed Japanese Patent Application No. 5-1418.
It is preferable to use those manufactured by the method proposed in No. 60.

That is, those obtained by the following method are preferred.

The precipitate of iron hydroxide obtained by neutralizing the aqueous solution containing iron ions is dried at a product temperature of 120 ° C. or less to obtain a semi-dried product having a water content of 20 to 50% without lowering the water content to less than 20%. After granulating the semi-dried product, it is dried at a product temperature of 120 ° C. or less.

The precipitate of iron hydroxide obtained by neutralizing the aqueous solution containing iron ions is dried at a product temperature of 120 ° C. or less to obtain a dried product having a water content of less than 20%.
Granulation is performed by a centrifugal tumbling type or centrifugal tumbling flow type granulator for 5 minutes or more while spraying water of ~ 300 µm, and then the granulated product is dried at a product temperature of 120 ° C or less.

According to such a method, a granulated product having sufficient strength can be obtained from iron hydroxide alone without using an auxiliary material for securing strength.

The particle size of such a dephosphorizing agent is preferably about 0.3 to 10 mm in terms of handleability and dephosphorization efficiency, and its breaking strength is 8 to 40 kgD.
It is preferably about WL from the viewpoint of handleability and backwashing effect.

As the dephosphorizing agent, those obtained by curing iron hydroxide with an unsaturated polyester resin or a polyurethane resin or the like can be used, but those having a large proportion of the curing agent and having excessively high strength are: Since the effect of the present invention cannot be obtained because the surface cannot be peeled off by backwashing, it is important to use a material that has been cured to such an extent that the surface can be peeled off.

In order to pass the phosphorus-containing water discharged from the sewage treatment apparatus into such a phosphorus-removing agent packed bed, for example, the phosphorus-removing agent is introduced into a phosphorus-removing tower or a phosphorus-removing tank in which the packed bed is formed. What is necessary is just to let the contained water flow by upward flow or downward flow.

In order to backwash the dephosphorizing agent whose dephosphorization performance has been reduced by the treatment of the phosphorus-containing water, for example, washing water (in the usual case, Dephosphorized water is used.)

The backwashing may be backwashing with air or backwashing with water and air in addition to backwashing with water.

[0021]

The present inventor has developed a method for treating a phosphorus-containing water by backwashing a phosphorus-removing agent having a reduced phosphorus-removing performance and peeling off the surface of the phosphorus-removing agent by mechanical impact. It was newly discovered that the phosphorus adsorbing performance of the dephosphorizing agent could be recovered, and that the exfoliated product of the dephosphorizing agent obtained by such backwashing of the dephosphorizing agent still had the adsorbing performance. .

Therefore, the separated product of the dephosphorizing agent is fed to a raw water tank, a flow control tank, an aeration tank, a contact aeration tank, a sedimentation tank, a coagulation treatment tank, a coagulation sedimentation tank, etc. of a sewage treatment apparatus.
Phosphorus in raw water can be removed by adsorption. Then
The exfoliated product of the phosphorus removing agent that has adsorbed phosphorus is taken into sludge and is efficiently discharged out of the system.

Further, when the stripped material of the dephosphorizing agent is returned to the sludge concentration tank and the sludge storage tank, the effect of suppressing scum generation can be obtained together with the removal of phosphorus by adsorption. It is presumed that the mechanism of the effect of suppressing the generation of scum due to the dephosphorization agent exfoliated matter is due to the flocculation effect of sludge by iron hydroxide which is a main component of the dephosphorization agent and the sedimentation effect due to its large specific gravity.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings.

FIGS. 1 to 3 are system diagrams each showing an embodiment of a method for treating phosphorus-containing water according to the present invention.

The method shown in FIG. 1 uses a biological sewage treatment apparatus by a contact aeration method as a sewage treatment apparatus, and removes phosphorus-containing water discharged from the sewage treatment apparatus by forming a packed layer of a dephosphorizing agent. It is treated in a phosphorus tower.

That is, the raw water is supplied from the pipe 11 to the flow control tank 1.
It is introduced into and then aerobic biological treatment is introduced to the contact aeration tank 2 from the pipe 12 with a pump P _1. The effluent from the contact aeration tank 2 is introduced into the sedimentation tank 3 from the pipe 13, and the supernatant water is passed through the pipe 14, the dephosphorization pump tank 4, and the pipe 15 provided with the pump P ₂ to the dephosphorization tower 5, and subjected to dephosphorization treatment. Water is discharged through a pipe 16, a backwash pump tank 6 and a pipe 17. On the other hand, the separated sludge in the sedimentation tank 3 is extracted from the pipe 18, and after the desorbed liquid is separated in the sludge concentration storage tank 7, it is carried out from the pipe 19. The desorbed liquid from the sludge concentration storage tank 7 is returned to the flow rate adjustment tank 1 through the pipe 20. In addition, 1
A and 2A are aeration tubes, 2B is a biofilm, and 5A is a dephosphorizing agent packed layer.

In the present embodiment, in such biological sewage treatment and dephosphorization treatment, if the dephosphorization performance of the dephosphorizing agent in the dephosphorization tower 5 decreases, the pumps P ₁ and P ₂ are stopped, By operating the pump P ₃ , the dephosphorization treatment water in the backwash pump tank 6 is passed upward from the pipe 21 to the dephosphorization tower 5 to backwash the dephosphorizing agent. Then, the backwash drainage discharged from the dephosphorization tower 5 and containing the dephosphorization agent separated by the backwash is returned to the flow control tank 1 through the pipe 22.

As described above, the dephosphorizing agent exfoliated material still has dephosphorization performance. Therefore, the dephosphorized agent exfoliated material in the backwash wastewater returned to the flow rate adjusting tank 1 is removed from the flow adjusting tank. Adsorb phosphorus in raw water in 1.

The exfoliated dephosphorizing agent introduced into the flow control tank 1 is in the form of fine particles and has a low sedimentation speed, but flows into the contact aeration tank 2 and the sedimentation tank 3 together with the raw water. In the process, the sludge is taken into the activated sludge and removed, and is carried out of the system as sludge.

In the method of this embodiment, the same effect can be obtained by returning the backwash wastewater to the contact aeration tank 2 and the sedimentation tank 3 in addition to the flow control tank 1. Further, by returning the sludge to the sludge concentrated storage tank 7, the removal of phosphorus re-released from the sludge in the sludge concentrated storage tank 7 and suppression of scum generation are prevented, and the phosphorus concentration of the desorbed liquid returned to the flow rate adjusting tank 1 is reduced. And the SS and BOD concentrations can be reduced.

In the method shown in FIG. 2, a biological activated sewage treatment apparatus based on a standard activated sludge method was used as a sewage treatment apparatus, and a phosphorus-containing water discharged from the sewage treatment apparatus was formed into a packed layer of a dephosphorizing agent. It is treated in a dephosphorization tank.

That is, the raw water is supplied from the pipe 41 to the flow control tank 3.
Is introduced into the 1, then aerobic biological treatment is introduced into the aeration tank 32 via piping 42 comprising a pump P _4. The effluent from the aeration tank 32 is introduced into the sedimentation tank 33 from the pipe 43, the supernatant water is passed through the pipe 44 to the dephosphorization tank 34, and the dephosphorized water is supplied to the pipe 45, the backwash pump tank 35 and the pipe 46. It is released after passing through. On the other hand, the separated sludge in the sedimentation tank 33 is
A part is returned from the pipe 48 to the aeration tank 32, and the remaining part is sent from the pipe 49 to the sludge concentration tank 36. The desorbed liquid separated in the sludge concentration tank 36 is returned to the aeration tank 32 from the pipe 50, and the separated sludge is carried out of the system via the pipe 51, the sludge storage tank 37, and the pipe 52. In addition, 3
1A and 32A are aeration tubes, and 34A is a dephosphorizing agent packed layer.

[0034] In this embodiment, in such biological sewage treatment and dephosphorization process, After dephosphorization performance of dephosphorization agent dephosphorization tank 34 is lowered, the pump is stopped P _4, pump P ₅ Is operated, the dephosphorization treatment water in the backwash pump tank 35 is passed from the pipe 53 to the dephosphorization tank 34 in an upward flow to backwash the dephosphorizing agent. And dephosphorization tank 3
The backwash wastewater discharged from 4 and containing the phosphorus-removing agent peeled off by backwashing is returned to the sludge concentration tank 36 through the pipe 54.

As described above, since the dephosphorized substance exfoliated still has dephosphorizing performance, the dephosphorized agent exfoliated in the backwashing wastewater returned to the sludge thickening tank 36 is separated from the sludge thickening tank. It adsorbs phosphorus in the liquid water in 36 and effectively acts to remove phosphorus in the system.

That is, the activated sludge has the ability to take in phosphorus, albeit slightly, but when the activated sludge having taken in phosphorus flows into the sludge concentration tank 36 and becomes anaerobic, the activated phosphorus is released. For this reason, the phosphorus concentration of the desorbed liquid increases. When the desorbed liquid having the increased phosphorus concentration is returned to the flow control tank 31, phosphorus is circulated in the system, and the phosphorus is not removed.

However, as in the present embodiment, the backwash wastewater containing the dephosphorized agent is sent to the sludge thickening tank,
Due to the phosphorus adsorption action of the exfoliated product of the phosphorus removing agent, it is possible to prevent an increase in the phosphorus concentration of the desorbed liquid due to the release of phosphorus from the activated sludge. And the exfoliated matter of the phosphorus removing agent which adsorbed phosphorus is taken into sludge and discharged out of the system, so that phosphorus in the system can be efficiently removed.

In the sludge thickening tank 37, scum is usually generated, and the return of the scum to the flow rate adjusting tank 31 together with the desorbed liquid causes an increase in SS and BOD in the system. By the addition of backwash wastewater, such a scum is prevented from being generated due to the coagulation effect and sedimentation effect of the dephosphorization agent mainly composed of iron hydroxide having a large specific gravity, and the SS and BOD in the system are effectively reduced. Reduced.

In this embodiment, the sludge thickening tank may be a sludge thickening storage tank. Also, in the method of the present embodiment, the same dephosphorizing effect as in the embodiment shown in FIG. 1 can be obtained by returning the backwash wastewater to the flow control tank 31, the aeration tank 32, or the sedimentation tank 33. it can.

The method shown in FIG. 3 uses a coagulating sedimentation treatment device as a sewage treatment device, and treats phosphorus-containing water discharged from the sewage treatment device in a dephosphorization tower having a packed layer of a dephosphorizing agent. It is.

That is, the raw water is subjected to a coagulation treatment through a first coagulation treatment tank 62 and a second coagulation treatment tank 63 from a pipe 61, the coagulation treatment water is settled and separated from a pipe 64 in a sedimentation tank 65, and the supernatant water is set in a pipe 66. The water is further passed through the dephosphorization tower 67 to be treated. This treated water is discharged from the pipe 68. Settling tank 65
The separated sludge is discharged from the pipe 69. 62A, 63A
Is a stirrer, and 67A is a dephosphorizing agent packed layer.

In this embodiment, when the dephosphorization performance of the dephosphorizing agent in the dephosphorization tower 67 is reduced in such coagulation sedimentation treatment and dephosphorization treatment, the supply of raw water is stopped to backwash water. Water is passed from the pipe 69 to the dephosphorization tower 67 in an upward flow to backwash the dephosphorizer. Then, the backwash wastewater containing the dephosphorization agent exfoliated from the dephosphorization tower 67 is discharged to the pipe 70.
It is returned to the first coagulation treatment tank 62.

As described above, by returning the backwashing wastewater from the dephosphorization tower 67 to the first flocculation tank 62, the exfoliated product of the dephosphorizing agent adsorbs the phosphorus contained in the raw water, and the exfoliated adsorbed phosphorus. The substance is taken into sludge in the sedimentation tank 65 through the second coagulation tank 63, is coagulated and settled, and is discharged out of the system. Thus, phosphorus in the raw water is removed.

Also in this embodiment, the backwash wastewater may be supplied to the second coagulation treatment tank or the sedimentation tank 65 in addition to the first coagulation treatment tank 62, and a phosphorus removing effect can be similarly obtained. .

The embodiments shown in FIGS. 1 to 3 are all embodiments of the present invention, and the present invention is not limited to the illustrated embodiment unless it exceeds the gist. .
For example, there is no particular limitation on the tank configuration and the like of each sewage treatment apparatus, and the backwash drainage may be returned to any tank of the sewage treatment apparatus or its inflow pipe.

Hereinafter, the present invention will be described in more detail with reference to experimental examples. The dephosphorizing agent used in the experimental examples was manufactured as follows.

That is, first, caustic soda was added to a 10% by weight aqueous solution of iron sulfate to adjust the pH to 7, and the obtained precipitate of iron hydroxide was dehydrated by a filter press to a water content of 61%, and the dehydrated cake was kneaded in a mixer. Water content 38% under reduced pressure at 90 ° C
And semi-dried. The obtained semi-dried product is subjected to centrifugal tumbling fluidized-granulation, and the particle size of 90% or more of the particles is 1-2.
It was granulated to a size in the range of mm. Next, the granulated product is air-dried for 2 days at room temperature to a moisture content of about 5%, and a breaking strength of iron hydroxide of 29 kg DW
L dephosphorizing agent was obtained.

EXPERIMENTAL EXAMPLE 1 The degree of recovery of phosphorus adsorption performance by backwashing was examined using a dephosphorizing agent whose phosphorus adsorption performance was lowered by adsorbing phosphorus to a saturated adsorption amount.

First, two transparent vinyl chloride columns (diameter 16 mm) were filled with a dephosphorizing agent (filling amount 26
ml, filling height 130 mm), 28 mg-P / l Na
_{A 2} HPO ₄ aqueous solution was passed through the solution in a downward flow at SV = 10 hr ⁻¹ for 6 days. After passing water for 6 days, the phosphorus concentration in the effluent is 25m
g-P / l, and it was confirmed that the phosphorus adsorption performance of the dephosphorizing agent was almost lost.

One of the two columns (N
o. For 1), water was flowed in an upward flow to backwash. Due to the water backwashing, the dephosphorizing agents collided with each other and their surfaces were peeled off, so that the obtained backwashing wastewater was colored red due to the delaminated material on the surface of the phosphorus desorbing agent that adsorbed phosphorus.

For the other column (No. 2), water was passed in a downward flow to extrude the aqueous solution of Na ₂ HPO ₄ in the column.

Each column was charged with Na ₂ H under the same conditions as above.
The PO ₄ aqueous solution was passed again, and the time-dependent change in the phosphorus concentration of the effluent was examined. The results are shown in FIG.

From FIG. 4, it can be seen that the surface of the dephosphorizing agent is peeled off by the mechanical shock applied by the backwashing, and the surface is renewed, and a surface having phosphorus adsorption performance is newly exposed. It turns out that the adsorption performance of the phosphorus agent recovers.

On the other hand, in the case of extruding with water without backwashing (No. 2), the phosphorus concentration of the effluent is high because the function of the dephosphorizing agent remains reduced.

Note that this No. N including column 1
o. The reason why the concentration of phosphorus in the effluent water is low in the column 2 in the initial stage of the water flow is that the backwash water or the extrusion water contained in the column initially flows out.

EXPERIMENTAL EXAMPLE 2 It was examined that the delaminated material on the surface of the dephosphorizing agent contained in the backwashing drainage had dephosphorizing performance.

A part of the backwash wastewater obtained in Experimental Example 1 (water quality is as shown in Table 1) was used as the raw water: the residential wastewater having the water quality shown in Table 1 was used as raw water: 9: The mixture was mixed at a ratio of 1 (volume ratio), the quality of the mixed water was examined, and the results are shown in Table 1.

[0058]

[Table 1]

The following is clear from Table 1.

That is, PO ₄ mixed water of raw water and backwash wastewater
^The concentration of ^3-- P is about 2.7 mg when calculated from the mixture ratio.
/ L (≒ 3.0 × 0.9), but in practice it has been greatly reduced to 0.5 mg / l, and phosphorus has been removed by removing the phosphorus removal agent. I understand. Since this mixed water does not remove the precipitate,
-P concentration is calculated value (4.0 × 0.9 + 14 × 0.1 =
5.0). That is, since the stripped material of the dephosphorizing agent is in the form of fine particles and has a low sedimentation speed, the TP concentration does not change.

From these results, it is found that the backwash wastewater containing the dephosphorizing agent exfoliated material is supplied to the raw water side (raw water tank, flow rate adjusting tank,
It can be understood that the dephosphorization treatment of the sewage in the sewage treatment apparatus can be performed by returning to the sedimentation separation tank or the like).

Experimental Example 3 It was examined that the exfoliated product of the dephosphorizing agent contained in the backwash wastewater had a dephosphorizing property, and that the exfoliated product was taken into activated sludge and removed.

The activated sludge mixture (collected from the aeration tank of the standard activated sludge method; the quality of the supernatant water obtained by standing for 60 minutes is shown in Table 2) was used as raw water and obtained in Experimental Example 1. A part of the backwash wastewater (the quality of the supernatant water obtained by standing for 60 minutes is shown in Table 2) was mixed with sufficient mixing at a ratio of raw water: backwash wastewater = 9: 1 (volume ratio). Then, the mixture is allowed to stand for 60 minutes, and the obtained supernatant water (hereinafter, referred to as “mixed supernatant water”).
And the results are shown in Table 2.

[0064]

[Table 2]

The following is clear from Table 2.

That is, the TP concentration and the PO ₄ ^3- -P concentration calculated from the mixture ratio of the raw water and the backwash wastewater were respectively TP = 4 × 0.1 + 2.8 × 0.9. ≒ 2.9m
g / l, PO ₄ ^3- -P ≒ 2.5 × 0.9 ≒ 2.25 mg
/ L, but the resulting mixed supernatant water has TP = 0.3
mg / l, PO ₄ ^3- -P = 0.1 mg / l, and it is clear that phosphorus is removed by mixing backwash wastewater.

The calculated value of SS is 13.9 m.
g / l (= 49 × 0.1 + 10 × 0.9) is SS = 10 mg / l in the mixed supernatant water, and the SS in the backwash wastewater is the activated sludge mixture. It can be seen that by mixing with the activated sludge, it was taken into the activated sludge and removed.

From these results, it is possible to return the backwash wastewater containing the dephosphorization agent to the tank containing activated sludge (contact aeration tank, aeration tank, sedimentation tank, etc.) of the sewage treatment apparatus, and to remove phosphorus from the wastewater. It can be seen that the separated product of the phosphorus removing agent in the backwash wastewater containing phosphorus can be separated and removed.

EXPERIMENTAL EXAMPLE 4 It was examined that the dephosphorization product contained in the backwash wastewater had dephosphorization performance and also had an effect of suppressing scum generation.

Experimental sludge (excess sludge by the activated sludge method. Scum comes up after standing for 2 days. The quality of the intermediate water under the scum is as shown in Table 3).
A part of the backwash wastewater obtained in the above (the quality of the supernatant water after standing for 2 days is as shown in Table 3) was converted into a ratio of raw sludge: backwash wastewater = 1: 1 (volume ratio). Table 3 shows the water quality of the supernatant water (hereinafter referred to as "mixed supernatant water") obtained by allowing the mixture to stand for 2 days.

[0071]

[Table 3]

The following is clear from Table 3.

That is, since phosphorus is released from raw sludge (excess sludge), the phosphorus concentration of the intermediate water obtained by allowing the excess sludge to stand still is considerably high. Then, T-P concentration and PO ₄ ^3- obtained by calculation from the mixing ratio of the raw sludge and the backwash waste water -
The P concentration was TP = 54 × 0.5 + 2 × 0.
5 = 28 mg / l, PO ₄ ^3- −P ≒ 20 × 0.5 = 10
mg / l, but the resulting mixed supernatant was TP = 4 m
g / l, PO ₄ ^3- -P = 3 mg / l, and it is clear that the adsorbed and removed phosphorus released is mixed with the backwash wastewater.

In the intermediate water of the raw sludge (excess sludge), SS = 100 mg / l and BOD = 20 due to the floating of the scum.
0 mg / l, which is extremely high, but in the mixed supernatant water, the SS, BOD
Are significantly reduced, and it can be seen that the occurrence of scum is suppressed.

From these results, it is possible to prevent the generation of scum and an increase in the phosphorus concentration due to the release of phosphorus by returning the backwashing wastewater containing the dephosphorized substance to the sludge concentration tank and the sludge concentration storage tank of the sewage treatment apparatus. You can see that it can be done.

[0076]

As described above in detail, according to the method for treating phosphorus-containing water of the present invention, the phosphorus-containing water discharged from the sewage treatment apparatus is passed through a dephosphorizing agent packed bed mainly composed of iron hydroxide. In the treatment method of phosphorus-containing water that absorbs and removes phosphorus by water, by effectively utilizing the exfoliated product of the dephosphorizing agent obtained by backwashing the dephosphorizing agent, the treatment efficiency of the sewage treatment apparatus in the former stage is increased,
High-quality treated water can be efficiently and inexpensively obtained.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a method for treating phosphorus-containing water according to an embodiment of the present invention.

FIG. 2 is a system diagram showing another embodiment of the method for treating phosphorus-containing water according to the present invention.

FIG. 3 is a system diagram showing another embodiment of the method for treating phosphorus-containing water of the present invention.

FIG. 4 is a graph showing the results of Experimental Example 1.

[Explanation of symbols]

 1,31 Flow control tank 2 Contact aeration tank 3,33,65 Settling tank 4 Dephosphorization pump tank 5,67 Dephosphorization tower 6,35 Backwash pump tank 7 Sludge concentration storage tank 32 Aeration tank 34 Dephosphorization tank 36 Sludge concentration tank 37 Sludge storage tank 62 First coagulation treatment tank 63 Second coagulation treatment tank

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C02F 1/28 C02F 1/58-1/64

Claims (2)

(57) [Claims] 1. A method for treating phosphorus-containing water, wherein phosphorus-containing water discharged from a sewage treatment apparatus is passed through a dephosphorizing agent-packed layer mainly composed of iron hydroxide to adsorb and remove phosphorus. By backwashing the dephosphorizing agent whose dephosphorizing performance has been reduced to remove the surface portion of the dephosphorizing agent,
Recovering the function of the dephosphorizing agent, returning the exfoliated material from the surface of the dephosphorizing agent to the sewage treatment apparatus, and subjecting the sewage in the sewage treatment apparatus to dephosphorization treatment. . 2. The method for treating phosphorus-containing water according to claim 1, wherein the dephosphorizing agent is backwashed with dephosphorized water, and the backwash wastewater containing the exfoliated material is supplied to a raw water tank of the sewage treatment apparatus, and a flow rate adjustment. A method for treating phosphorus-containing water, wherein the phosphorus-containing water is fed to any one of a tank, a contact aeration tank, an aeration tank, a sedimentation tank, a sludge concentration tank, and a sludge concentration storage tank or an inflow pipe thereof.