JP2014200781A - Phosphorus recovery apparatus and phosphorus recovery method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phosphorus recovery apparatus capable of efficiently removing and recovering phosphorus from a phosphorus-containing effluent and of promoting a stable progress of the treatment.SOLUTION: The provided phosphorus recovery apparatus 1 recovers, as apatite crystals, phosphorus within a body of phosphorus-containing effluent 2. This phosphorus recovery apparatus 1 includes a first crystallization tank 5 for performing a crystallizing treatment and a second crystallization tank 7 for performing a filtering/crystallizing treatment at a step posterior to this first crystallization tank 5. The first crystallization tank 5 includes: a mixing segment 25 in which apatite crystals are crystallized/deposited via a crystallizing reaction and then suspended; and a separation segment 26 in which the suspended apatite crystals are precipitated and separated. The apatite crystals are filled into the second crystallization tank 7 as a filter bed 41. The post-crystallization water 6 following the treatment within the first crystallization tank 5 streams into the second crystallization tank 7 as an upward flow.

Description

  The present invention relates to a phosphorus recovery apparatus and a phosphorus recovery method for recovering phosphorus by adding calcium to phosphorus-containing wastewater.

  Conventionally, a phosphorus recovery apparatus that recovers phosphorus by adding calcium to a phosphorus-containing wastewater containing several tens mg / L or more of phosphorus uses a crystallization reaction, so that the concentration of phosphorus in treated water is extremely low. It was difficult to maintain.

  Therefore, equipment such as agglomeration and precipitation is necessary for removing phosphorus after the phosphorus recovery apparatus.

  The phosphorus collection | recovery apparatus of patent document 1 is the structure provided with the two-stage crystallization tank so that the phosphorus density | concentration of process water can be reduced to 1 mg / L or less.

  And the 1st crystallization tank adjusts pH to 6.5 or more and 8.5 or less, and the 2nd crystallization tank adjusts pH to 8.5 or more, and is adjusted to the 1st crystallization tank. Large apatite crystals are grown and fine apatite crystals are produced in the second crystallization tank to improve the recovery rate.

Japanese Patent No. 4223334

  However, since fine apatite crystals produced under high pH conditions have poor sedimentation properties, in the configuration of Patent Document 1 described above, in order to perform solid-liquid separation with the apatite crystals in suspension, the sedimentation time is very long. It is necessary to set the time, and phosphorus cannot be efficiently removed and recovered from the phosphorus-containing wastewater.

  In addition, the fine apatite crystals generated in the second crystallization tank are not easily grown as apatite crystals even if they are returned to the first crystallization tank. If too much is produced, fine apatite crystals will increase and accumulate in the system, and eventually solid-liquid separation will not be possible and fine apatite crystals may flow out, and the process cannot proceed stably. There is a possibility.

  The present invention has been made in view of such points, and an object of the present invention is to provide a phosphorus recovery apparatus and a phosphorus recovery method that can efficiently remove and recover phosphorus from phosphorus-containing wastewater and can proceed with treatment stably. To do.

  The phosphorus recovery apparatus according to claim 1, wherein calcium is added to the phosphorus-containing wastewater, and apatite crystals are crystallized by a crystallization reaction between phosphate ions and the calcium in the phosphorus-containing wastewater, and phosphorus is added to the apatite. A phosphorus recovery device for recovering as crystals, a mixing part for crystallizing apatite crystals by causing a crystallization reaction between the phosphate ions and calcium, and the apatite crystals crystallized in the mixing part from phosphorus-containing wastewater A first reaction tank having a separation unit for precipitation separation, and a second reaction tank filled with apatite crystals as a filter bed, and the second reaction tank is treated in the first reaction tank. After that, phosphorus-containing wastewater is introduced in an upward flow.

  The phosphorus recovery device according to claim 2 is the phosphorus recovery device according to claim 1, wherein the first reaction tank is separated from the mixing portion partitioned by a cylindrical partition member having an open bottom and a ceiling. The mixing section is provided with a draft tube and a stirring means, and the agitating means forms an upward flow in the draft tube so that an apatite crystal as a crystallization material is formed in the mixing section. A circulating flow having a content of 10 g / L or more is generated.

  The phosphorus recovery device according to claim 3 is the phosphorus recovery device according to claim 1 or 2, wherein the second reaction tank is filled with apatite crystals to form a filter bed of 0.5 m or more and less than 2 m. Is.

  The phosphorus recovery apparatus according to claim 4 is the phosphorus recovery apparatus according to any one of claims 1 to 3, wherein at least a part of the washing waste water that has washed the filter bed of the second reaction tank is the first reaction tank. The apatite crystals are recovered from at least one of the first reaction tank and the second reaction tank.

  The phosphorus recovery device according to claim 5 is the phosphorus recovery device according to any one of claims 1 to 4, wherein the pH is adjusted to 7.5 or more and 8.5 or less in the first reaction tank, In the second reaction tank, the pH is adjusted to be higher than the pH in the first reaction tank.

  The phosphorus recovery apparatus according to claim 6 is the phosphorus recovery apparatus according to any one of claims 1 to 5, wherein calcium is added to at least one of the first reaction tank and the second reaction tank. Means, a mixing part of the first reaction tank, a part into which the phosphorus-containing wastewater flows after being treated in the first reaction tank in the second reaction tank, and the second reaction tank Calcium is added to at least one of the bottoms.

  The phosphorus recovery device according to claim 7 is the phosphorus recovery device according to any one of claims 1, 2, 3, 5 and 6, wherein an acid is added to the phosphorus-containing wastewater before the first reaction tank. A decarbonation means for removing carbonate ions by aeration or agitation in a state where the pH is 5.5 or less is provided, and at least a part of the washing waste water that has washed the filter bed of the second reaction tank is returned to the decarbonation means. It is what is done.

  The phosphorus recovery device according to claim 8 is the phosphorus recovery device according to any one of claims 1, 2, 3, 5, 6, and 7, wherein at least the washing waste water that has washed the filter bed of the second reaction tank is used. A cleaning wastewater decarboxylation means for removing carbonate ions by aeration or agitation in a state where the pH is adjusted to 5.5 or less in a state in which acid is partially added is provided. It is returned to at least one of the first reaction tank and the second reaction tank.

  The phosphorus recovery device according to claim 9 is the phosphorus recovery device according to any one of claims 1 to 8, wherein the second reaction tank includes a treated water outlet through which treated water after treatment is discharged, and a filter bed. A cleaning drainage outlet from which the cleaning drainage is washed out, and the treated water outlet is installed at the same height as the cleaning drainage outlet or above the cleaning drainage outlet. is there.

  The phosphorus recovery device according to claim 10 is the phosphorus recovery device according to any one of claims 1 to 9, wherein the sewage is biologically treated, and the biologically treated water after the biological treatment is solid-liquid into phosphorus-containing wastewater and sludge. Pretreatment means for separating is provided, and in this pretreatment means, the sludge is solubilized to elute phosphorus.

  The phosphorus recovery method according to claim 11, wherein calcium is added to phosphorus-containing wastewater, apatite crystals are crystallized by a crystallization reaction between phosphate ions and the calcium in the phosphorus-containing wastewater, and phosphorus is added to the apatite. A phosphorus recovery method for recovering as crystals, supplying phosphorus-containing wastewater and calcium to a first reaction tank, adjusting the pH in the first reaction tank to 7.5 or more and 8.5 or less, Crystallization of phosphate ions and calcium of the phosphorus-containing wastewater by generating an upward flow inside the draft tube in the first reaction tank and generating a circulating flow having an apatite crystal concentration of 10 g / L or more Apatite crystals are crystallized by reaction, and phosphorus-containing wastewater treated in the first reaction tank is supplied in an upward flow from the bottom of the second reaction tank filled with apatite crystals as a filter bed. .

  According to the invention described in claim 1, since the apatite crystals are packed as the filter bed of the second reaction tank, and the fine crystals contained in the phosphorus-containing wastewater can be captured while the apatite crystals are crystallized in the filter bed, Phosphorus can be efficiently removed and recovered from phosphorus-containing wastewater, and the treatment can proceed stably.

  According to the invention described in claim 2, since the upward flow is formed in the draft tube, a circulating flow having an apatite crystal concentration of 10 g / L or more can be generated in the mixing portion. The crystallization reaction tends to proceed at.

  According to the invention described in claim 3, since the apatite crystal filter bed is filled with 0.5 m or more and less than 2 m, phosphorus can be efficiently removed from the phosphorus-containing wastewater, and the treatment can proceed stably. .

  According to the invention described in claim 4, since the washing waste water is returned to the first reaction tank, the fine apatite crystals contained in the washing waste water can be effectively used, and the phosphorus recovery rate can be improved.

  According to the invention described in claim 5, since the pH in the second reaction tank is higher than the pH in the first reaction tank, the crystallization reaction in the filter bed easily proceeds.

  According to the invention described in claim 6, it is easy to optimize the amount of calcium added to the first reaction tank and the second reaction tank.

  According to the invention described in claim 7, in order to remove carbonate ions from the phosphorus-containing wastewater by the decarboxylation means in the first stage of the first reaction tank, crystals due to the formation of calcium carbonate in the first reaction tank. It is possible to prevent a decrease in reactivity of the deposition reaction.

  According to the invention described in claim 8, since carbonate ions are removed from the washing wastewater by the washing wastewater decarboxylation means, it is possible to prevent a decrease in the reactivity of the crystallization reaction due to the formation of calcium carbonate in the washing wastewater, When the first reaction tank cannot be used or when the phosphorus concentration of the phosphorus-containing wastewater is low, the phosphorus-containing wastewater can be treated only with the second reaction tank.

  According to the invention described in claim 9, since the treated water outlet is installed at the same height as the washing drain outlet or above the washing drain outlet, the fine apatite crystals contained in the washing drain are It is possible to prevent the treated water outlet from being clogged with the treated water outlet.

  According to the invention described in claim 10, since the biologically treated water is solid-liquid separated into the phosphorus-containing wastewater and the sludge by the pretreatment means, the quality of the apatite crystals is reduced due to the mixing of the sludge into the phosphorus-containing wastewater. Can be prevented. Moreover, since the pretreatment means elutes the phosphorus contained in the sludge, the phosphorus recovery rate can be improved.

  According to the invention described in claim 11, since the apatite crystals are packed as the filter bed of the second reaction tank, and the fine crystals contained in the phosphorus-containing wastewater can be supplemented while crystallizing the apatite crystals in the filter bed, Phosphorus can be efficiently removed and recovered from phosphorus-containing wastewater, and the treatment can proceed stably.

It is a lineblock diagram showing the phosphorus recovery device concerning a 1st embodiment of the present invention. It is a block diagram which shows the phosphorus collection | recovery apparatus which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the phosphorus collection | recovery apparatus which concerns on the 3rd Embodiment of this invention.

  The configuration of the first embodiment of the present invention will be described in detail below with reference to FIG.

  In FIG. 1, reference numeral 1 denotes a phosphorus recovery device. This phosphorus recovery device 1 adds calcium to a phosphorus-containing wastewater 2 containing phosphate ions, and crystallizes phosphate ions and calcium in the phosphorus-containing wastewater 2. Apatite crystals are crystallized by reaction to recover phosphorus as apatite crystals.

  The phosphorus recovery apparatus 1 includes pretreatment means (not shown) that biologically treats sewage such as organic wastewater containing phosphate ions at a high concentration with microorganisms to form phosphorus-containing wastewater 2.

  A decarboxylation tower 3 as a decarboxylation means for removing carbonate ions by decarboxylating the phosphorus-containing wastewater 2 biologically treated by the pretreatment means is disposed downstream of the pretreatment means. Is provided.

  Further, on the downstream side, which is the rear stage of the decarboxylation tower 3, as a first reaction tank for crystallization treatment of decarbonation treated water 4 as phosphorus-containing waste water from which carbonate ions have been removed in the decarbonation tower 3. A first crystallization tank 5 is provided. The crystallization process is a process for separating and separating phosphorus in the decarboxylated water 4 as an apatite crystal by a crystallization reaction.

  Further, crystallization water 6 as phosphorus-containing waste water crystallized in the first crystallization tank 5 flows in an upstream flow downstream of the first crystallization tank 5. A second crystallization tank 7 is provided as a second reaction tank.

  The pretreatment means biologically treats sewage with microorganisms to obtain biologically treated water containing phosphate ions at a high concentration. Moreover, this biologically treated water is solid-liquid separated into phosphorus-containing wastewater 2 and sludge. The pretreatment means preferably has a configuration in which sludge that has been subjected to solid-liquid separation is extracted, and the extracted sludge is solubilized to elute phosphorus contained in the sludge.

  The decarboxylation tower 3 is connected to the pretreatment means via the pipe 11 and the pump 12, and the phosphorus-containing waste water 2 is supplied from the pretreatment means.

  The decarboxylation tower 3 is provided with pH adjusting means (not shown) for adjusting the pH of the phosphorus-containing wastewater 2 to a predetermined value, for example, 5.5 or less, and an aeration means 13 by adding acid.

  The pH adjusting means has, for example, a measuring means for measuring the pH in the tank and an adding means for adding acid, and the acid in the tank is set to a predetermined value by adding acid based on the measurement result of the measuring means. adjust.

  The aeration means 13 has a blower 14 and an air diffuser 15 connected to the blower 14, and air from the blower 14 is supplied into the tank through the air diffuser 15 and aerated from the lower part of the tank.

  In the decarbonation tower 3, the carbon dioxide dissolved in the phosphorus-containing wastewater 2 is removed by aeration or stirring by the aeration means 13 with the pH of the phosphorus-containing wastewater 2 adjusted by the pH adjusting means. I care. That is, by such a decarboxylation treatment, carbonate ions contained in the phosphorus-containing wastewater 2 are removed and the decarboxylation treatment water 4 is obtained. In addition, content of phosphorus in the decarboxylated water 4 is, for example, 50 mg / L or more and 100 mg / L or less.

  The first crystallization tank 5 is connected to the decarbonation tower 3 through a pipe 16, and decarboxylated water 4 is supplied from the decarbonation tower 3 through the pipe 16.

  Inside the first crystallization tank 5, an inner cylinder partition 17 and a stirring means 18 are installed as cylindrical partition members whose bottom and ceiling are open. A draft tube 20 is provided in the inner cylinder partition 17.

  Further, the first crystallization tank 5 is provided with a calcium adding means 19 for supplying a calcium-containing liquid as a calcium source into the inner cylinder partition 17 and adding calcium.

  Further, the first crystallization tank 5 is provided with a pH adjusting means (not shown) for adjusting the pH of the decarboxylated water 4 in the first crystallization tank 5 to a predetermined value, for example, 7.5 to 8.5. It has been.

  The stirring means 18 has a shaft 22 connected to a motor 21, and the shaft 22 is installed so as to extend from the motor 21 into the draft tube 20. Further, fins 23 and 24 are fixed to the shaft 22, the fin 23 is located in the draft tube 20, and the fin 24 is located below the draft tube 20. The shaft 22 and the fins 23 and 24 are rotated by the driving force of the motor 21.

  Inside the inner cylinder partition 17 is formed a mixing unit 25 for crystallizing apatite crystals by causing a crystallization reaction between phosphate ions in the decarboxylated water 4 and calcium added by the calcium addition means 19. Has been. That is, in the mixing unit 25, the decarbonated water 4 and calcium are stirred and mixed by the stirring means 18 to suspend and flow the apatite crystals as the crystallization material in the decarbonated water 4. The crystallization reaction of apatite crystals is advanced.

  Here, since the apatite crystal has a specific gravity of 3.17 and is larger than that of the crystallization treated water 6, it usually does not flow easily and the crystallization reaction does not proceed easily.

  Therefore, the draft tube 20 is installed inside the inner cylinder partition 17. That is, the inner cylinder partition 17 is installed between the inner surface of the first crystallization tank 5 and the outer surface of the draft tube 20. That is, the mixing unit 25 is provided with the draft tube 20 and the stirring means 18.

  Then, by driving the stirring means 18, an upward flow is formed in the draft tube 20, and an upward circulating flow is generated in the mixing unit 25. That is, an upward flow is generated in the draft tube 20 and a downward flow is generated between the draft tube 20 and the inner cylinder partition 17.

  In this way, by generating a circulating flow in the mixing unit 25, the apatite crystals can be flowed, and the concentration of the apatite crystal as a crystallization material can be increased to a high concentration of 10 g / L or more in the mixing unit 25. , Can improve the reactivity.

  The liquid in the mixing unit 25 of the first crystallization tank 5 after the crystallization reaction has, for example, a pH of 8.0 or more and 8.2 or less and a content of several hundred μm apatite crystals of 10,000 mg / L or more and 100,000 mg / L. In the following, the content of fine apatite crystals is 100 mg / L or more and 1000 mg / L or less. Further, the content of soluble phosphorus is several tens mg / L.

  On the other hand, a separation portion 26 is formed between the inner surface of the first crystallization tank 5 and the outer surface of the inner cylinder partition 17. In the separation unit 26, the apatite crystals suspended in the crystallization reaction in the mixing unit 25 are precipitated and separated, and the crystallization treated water 6 and the apatite crystals are separated into solid and liquid.

  A recovery means 27 is provided at the bottom of the first crystallization tank 5 for extracting and recovering the crystallized apatite crystals separated and deposited by the separation unit 26. The recovery means 27 is appropriately configured by a pump, a valve, a pipe, etc. (not shown).

  The first crystallization tank 5 is connected to a crystallization treated water storage tank 29 through a pipe 28. Then, the crystallization treated water 6 after the crystallization treatment in the first crystallization tank 5 flows out through the pipe 28 and is stored in the crystallization treated water storage tank 29.

  The crystallization treated water storage tank 29 is connected to the second crystallization tank 7 via a pipe 31, a pipe 32 and a pump 33. Then, the crystallization treated water 6 is supplied from the crystallization treated water storage tank 29 to the second crystallization tank 7 through the pipe 31, the pipe 32 and the pump 33.

  The crystallization treated water storage tank 29 is provided with crystallization treated water returning means 34 for returning the crystallization treated water 6 to the first crystallization tank 5.

  The crystallization water return means 34 includes a pipe 35 having one end connected to the crystallization water storage tank 29, a pipe 36 having one end connected to the decarboxylation tower 3, and the other end of the pipe 35 and a pipe 36. The other end is connected to a pump 37, and a flow rate adjusting means is provided as appropriate.

  The second crystallization tank 7 is filled with apatite crystals as a crystallization material as a filter bed 41.

  Specifically, the filter bed 41 is preferably configured to be filled with apatite crystals having a particle size of several hundreds of micrometers so that the height is 0.5 m or more and less than 2 m.

  And in the 2nd crystallization tank 7, the crystallization process water 6 which flowed in by the upward flow from the bottom part is filtration-crystallized. That is, the crystallization treated water 6 is filtered through the filter bed 41 to capture fine particles, and the phosphate ions contained in the crystallization treated water 6 form an apatite crystal that forms the filter bed 41 as a crystallization material. Analyze reaction.

  In addition, since the crystallization reaction of the apatite crystal is also performed in the second crystallization tank 7, calcium may be added to the second crystallization tank 7. If only calcium is added and the amount of calcium required for the entire phosphorus recovery apparatus 1 is added in the first crystallization tank 5, the number of calcium adding means 19 is minimized and the apparatus is simplified. This is preferable.

  As a result of the filtration and crystallization treatment by the filter bed 41, the filtration and crystallization treatment water 42 as the treated water from which fine particles are filtered and phosphorus is removed flows out to the upper part of the filter bed 41.

  The second crystallization tank 7 is provided with pH adjusting means (not shown) for adjusting the pH of the crystallization water 6 in the second crystallization tank 7 to a predetermined value.

  Here, when the pH of the second crystallization tank 7 is lower than the pH of the first crystallization tank 5, a reaction in which the apatite crystals dissolve in the second crystallization tank 7 proceeds, and the filtered crystallization treated water The phosphorus concentration of 42 becomes high.

  Therefore, in the 2nd crystallization tank 7, the structure which adjusts so that pH in the 2nd crystallization tank 7 may become higher than pH in the 1st crystallization tank 5 by a pH adjustment means is suitable. .

  Specifically, the pH of the second crystallization tank 7 is preferably about 0.4 higher than the pH of the first crystallization tank 5, for example, and adjusted to around 8.5.

  In addition, since each pH adjustment means adjusts pH by adding a chemical | drug | medicine or a solution, since cost can be restrained by suppressing addition amount as much as possible, it is preferable.

  Thus, the filtered and crystallized water 42 after the filtered and crystallized treatment hardly contains fine apatite crystals.

  Further, since fine apatite crystals are captured in the filter bed 41 after the filtration and crystallization treatment, the washing drainage 43 that has washed the filter bed 41 contains a large amount of fine apatite crystals. .

  The second crystallization tank 7 is provided with a treated water outlet 44 through which the filtered crystallization treated water 42 flows out and a washing drain outlet 45 through which the washed wastewater 43 flows out.

  The treated water outlet 44 and the washing drain outlet 45 are configured such that the treated water outlet 44 is disposed at the same height as the washing drain outlet 45, or the treated water outlet 44 is the washing drain outlet as shown in FIG. A configuration disposed above 45 is preferred.

  The treated water outlet 44 is connected to the treated water storage tank 47 via a pipe 46. Then, the filtered and crystallized treated water 42 after the filtered and crystallized treatment is supplied from the treated water outlet 44 to the treated water storage tank 47 through the pipe 46.

  The filtered crystallization treated water 42 in the treated water storage tank 47 contains almost no fine apatite crystals, and the phosphorus content in the filtered crystallization treated water 42 is 1 mg / L or less.

  The treated water storage tank 47 is provided with treated water returning means 48 for returning the filtered crystallization treated water 42 to the second crystallization tank 7.

  This treated water return means 48 is connected to a pipe 51 having one end connected to the treated water storage tank 47, a pipe 52 having one end connected to the pipe 32, the other end of these pipes 51, and the other end of the pipe 52. And a pump 53.

  A part of the filtered crystallization treated water 42 in the treated water storage tank 47 is returned to the second crystallization tank 7, and the remaining part is discharged out of the phosphorus recovery apparatus 1 such as a river.

  The cleaning drainage outlet 45 is connected to the cleaning drainage storage tank 55 via a pipe 54. Then, the cleaning wastewater 43 after cleaning the filter bed 41 is supplied from the cleaning drainage outlet 45 through the pipe 54 to the cleaning drainage storage tank 55.

  The washing wastewater 43 in the washing drainage storage tank 55 contains a large amount of fine apatite crystals as described above. The content of soluble phosphorus in the cleaning wastewater 43 is less than 1 mg / L, and the pH in the cleaning wastewater storage tank 55 is around 8.

  The cleaning drainage tank 55 is provided with cleaning drainage return means 56 for returning the cleaning drainage 43 to the first crystallization tank 5.

  The cleaning drainage return means 56 includes a pipe 57 having one end connected to the cleaning drainage storage tank 55, a pipe 58 having one end connected to the first crystallization tank 5, and the other end of these pipes 57 and the pipe 58. The pump 59 is connected to the other end.

  The cleaning wastewater 43 containing a large amount of fine apatite crystals is returned from the cleaning wastewater storage tank 55 to the crystallization water storage tank 29 for effective use, and the crystallization water storage tank 29 supplies the first crystallization tank. Returned to 5. That is, the washing waste water 43 is mixed with the crystallization water 6 in the crystallization water storage tank 29, and a part thereof is returned to the first crystallization tank 5 by the crystallization water return means 34. Is supplied to the second crystallization tank 7.

  In the crystallization treated water storage tank 29, by mixing the crystallization treated water 6 and the washing waste water 43, for example, the pH is 7.8 or more and 8.2 or less, and the content of fine apatite crystals is several. At 10 mg / L, the content of soluble phosphorus is around 10 mg / L.

  Next, the operation and effect of the first embodiment will be described.

  When the phosphorus-containing wastewater 2 from the pretreatment means or the like is processed in the phosphorus recovery apparatus 1, first, decarbonation is performed in the decarboxylation tower 3.

  In the decarboxylation treatment, an acid is added to the phosphorus-containing wastewater 2 to remove the carbonate ions from the phosphorus-containing wastewater 2 by aeration or stirring in a state where the pH is 5.5 or lower.

  The decarboxylated water 4 treated in the decarboxylation tower 3 is supplied to the first crystallization tank 5 and crystallized.

  In the crystallization process, the decarboxylated water 4 and calcium supplied to the mixing unit 25 are mixed by the stirring means 18.

  Here, in the mixing unit 25, an upward flow is formed in the draft tube 20 by the stirring means 18, and a circulating flow in which the content of the apatite crystal as the crystallization material is 10 g / L or more is generated. The crystallization reaction is accelerated.

  Further, the phosphate ions and calcium in the decarboxylated water 4 are crystallized and the apatite crystals are suspended in the decarboxylated water 4.

  Further, the apatite crystals are suspended and flow into the separation unit 26 from the mixing unit 25, and the crystallization treated water 6 and the apatite crystals are solid-liquid separated by precipitation separation in the separation unit 26.

  The apatite crystal, which is a solid obtained by solid-liquid separation, precipitates and accumulates at the bottom of the first crystallization tank 5.

  Then, the apatite crystals are flowed out of the first crystallization tank 5 by the collecting means 27 provided at the bottom, drained, and then collected.

  On the other hand, the crystallization treated water 6 which is a liquid separated into solid and liquid flows out to the crystallization treated water storage tank 29.

  The crystallization water 6 stored in the crystallization water storage tank 29 is supplied in an upward flow from the bottom of the second crystallization tank 7 by the driving force of the pump 33.

  Crystallized treated water 6 supplied to the second crystallization tank 7 in an upward flow passes through the filter bed 41 so as to rise from the lower side, and is a fine apatite crystal that has not been separated by the separation unit 26 or others. Fine particles such as impurities are captured and filtered.

  In addition, since the second crystallization tank 7 is filled with apatite crystals as the filter bed 41, the apatite crystals act as a crystallization material when the crystallization treated water 6 passes through the filter bed 41. That is, phosphorus contained in the crystallization treated water 6 crystallizes as apatite crystals, and the content of soluble phosphorus decreases.

  The filtered and crystallized treated water 42 that has been filtered and crystallized in the filter bed 41 flows out to the upper part of the filter bed 41, flows out from the treated water outlet 44 to the treated water storage tank 47, and recovers phosphorus from the treated water storage tank 47. It is discharged out of the device 1.

  On the other hand, since fine apatite crystals are attached to the bottom in the second crystallization tank 7 and the filter bed 41 by the filtration crystallization treatment, The crystallization tank 7 and the filter bed 41 are washed.

  This washing wastewater 43 contains a large amount of fine apatite crystals, and flows out from the washing drainage outlet 45 to the washing drainage storage tank 55 and is returned to the crystallization treated water storage tank 29.

  Further, a part of the crystallization treated water 6 in the crystallization treated water storage tank 29 and the returned washing waste water 43 are returned to the first crystallization tank 5 by the crystallization treated water returning means 34, and again the first crystallization treated water 43 is returned to the first crystallization tank 5. Crystallization is performed in the crystallization tank 5.

  And according to the said phosphorus collection | recovery apparatus 1, it passes through the filter bed 41, crystallizing an apatite crystal with the filter bed 41 by being filled with the apatite crystal as the filter bed 41 of the 2nd crystallization tank 7. Fine apatite crystals contained in the crystallization treated water 6 can be captured. That is, a fine apatite crystal that could not be separated in the first crystallization tank 5 can be separated in the second crystallization tank 7 by a synergistic effect of the crystallization action and the trapping action in the filter bed 41.

  Therefore, the phosphorus recovery apparatus 1 can efficiently remove and recover phosphorus from the phosphorus-containing wastewater 2 and can stably proceed with the treatment.

  Moreover, the phosphorus collection | recovery apparatus 1 can carry out solid-liquid separation of the biologically treated water into the phosphorus containing waste water 2 and sludge by installing the pretreatment means. Therefore, it is possible to prevent the quality of the apatite crystals from being deteriorated due to the mixing of sludge into the phosphorus-containing wastewater 2, and the recovered apatite crystals can be easily reused as, for example, fertilizer.

  Moreover, the phosphorus recovery rate can be improved by eluting phosphorus contained in the sludge by the pretreatment means.

  By providing the decarboxylation tower 3 in the previous stage of the first crystallization tank 5, carbonate ions can be removed from the phosphorus-containing wastewater 2 in the previous stage of the first crystallization tank 5. It is possible to prevent a decrease in the reactivity of the crystallization reaction due to the formation of calcium carbonate.

  In the first crystallization tank 5, since the draft tube 20 and the stirring means 18 are provided in the mixing unit 25, an upward flow can be formed in the draft tube 20 by driving the stirring means 18. Therefore, a circulating flow having an apatite crystal concentration of 10 g / L or more can be generated in the mixing unit 25, and the crystallization reaction easily proceeds in the first crystallization tank 5.

  Since the calcium adding means 19 is provided in the first crystallization tank 5 and calcium is added to the mixing unit 25, the amount of calcium added in the first crystallization tank 5 can be easily optimized.

  In the second crystallization tank 7, the filter bed 41 of apatite crystals is filled with 0.5 m or more and less than 2 m, so that the filtration crystallization process can proceed more reliably when passing through the filter bed 41. Therefore, phosphorus can be efficiently removed from the crystallization treated water 6 and the treatment can proceed stably.

  In the second crystallization tank 7, the second crystallization tank 7 is adjusted by adjusting the pH in the second crystallization tank 7 to be higher than the pH in the first crystallization tank 5. 7 can prevent dissolution of the apatite crystals, so that the crystallization reaction in the filter bed 41 easily proceeds.

  In the second crystallization tank 7, the treated water outlet 44 is installed at the same height as the washing drainage outlet 45 or above the washing drainage outlet 45. Since 43 is immersed in the treated water outlet 44, the treated water outlet 44 can be prevented from being clogged with the fine apatite crystals of the washing waste water 43.

  By returning the cleaning wastewater 43 to the first crystallization tank 5, it can be effectively used to re-grow the fine apatite crystals contained in the cleaning wastewater 43, and the phosphorus recovery rate can be improved.

  In addition, the cleaning wastewater 43 is returned to the first crystallization tank 5 through the crystallization treated water storage tank 29, so that the crystallization treated water 6 is returned to the first crystallization tank 5. Since the crystallization treatment water returning means 34 and the returning means for returning the washing waste water 43 to the first crystallization tank 5 can be made common, the configuration of the apparatus can be simplified and the cost can be reduced.

  In addition, in the said 1st Embodiment, although the phosphorus collection | recovery apparatus 1 was set as the structure provided with a pre-processing means, it is not limited to such a structure, For example, the phosphorus containing wastewater pre-processed by the separate installation etc. A configuration in which 2 is supplied or a configuration in which the phosphorus-containing wastewater 2 is supplied as it is may be used.

  In addition, although the decarboxylation tower 3 is installed in the previous stage of the first crystallization tank 5, it is not limited to such a configuration, and the phosphorus-containing waste water 2 may be configured not to be decarboxylated.

  The first crystallization tank 5 has a configuration in which the draft tube 20 is provided in the mixing unit 25, but is not limited to such a configuration, and the crystallization reaction between phosphate ions and calcium in the mixing unit 25. Any structure may be used as long as the apatite crystals crystallized can be solid-liquid separated by the separation unit 26.

  The second crystallization tank 7 has a configuration in which the treated water outlet 44 is provided above the washing drain outlet 45, but is not limited to such a configuration, and the treated water outlet 44 and the washing drain outlet 45 are not limited thereto. The installation position of can be designed as appropriate.

  The calcium adding means 19 is provided only in the first crystallization tank 5 and calcium is added only to the mixing section 25. However, the present invention is not limited to such a structure, and the first crystallization tank 5 and the first crystallization tank 5 are not limited thereto. A configuration in which the calcium addition means 19 is provided in both the two crystallization tanks 7 or a configuration in which the calcium addition means 19 is provided only in the second crystallization tank 7 may be adopted.

  When the second crystallization tank 7 is provided with the calcium addition means 19, the crystallization treated water after being treated in the first crystallization tank 5 in the second crystallization tank 7. A configuration in which calcium is added to the portion into which 6 flows or the bottom of the second crystallization tank 7 is preferable.

  Thus, by providing the calcium addition means 19 in the 2nd crystallization tank 7, it is easy to optimize the addition amount of the calcium in the 2nd crystallization tank 7. FIG. In particular, by providing calcium addition means 19 in both the first crystallization tank 5 and the second crystallization tank 7, the amount of calcium added to the first crystallization tank 5 and the second crystallization tank 7 can be reduced. It is easy to optimize, and calcium can be efficiently added as the entire phosphorus recovery apparatus 1.

  Although the apatite crystals are recovered from the first crystallization tank 5, the present invention is not limited to such a configuration, and the apatite crystals may be recovered from the second crystallization tank 7.

  In the configuration for recovering the apatite crystals from the second crystallization tank 7, a recovery means including a valve and a slurry pump is provided at the bottom of the second crystallization tank 7.

  Then, while allowing the crystallization treated water 6 to flow into the second crystallization tank 7 in an upward flow, the valve at the bottom of the second crystallization tank 7 is opened, and the apatite is driven by natural flow or driving of the slurry pump. Pull out the crystals and collect them.

  The phosphorus recovery apparatus 1 is configured to include the crystallization treated water returning means 34, the treated water returning means 48, and the washing waste water returning means 56. However, the present invention is not limited to such a configuration, and each returning means is appropriately designed. This is possible, and each return means may not be provided.

  Further, when the cleaning waste water returning means 56 is provided, the cleaning waste water 43 is not limited to the configuration in which the cleaning waste water 43 is returned to the first crystallization tank 5 via the crystallization treated water storage tank 29. You may make it the structure returned to the 1st crystallization tank 5 directly.

  Further, the cleaning drainage returning means 56 is not limited to the configuration in which the cleaning drainage 43 is returned to the first crystallization tank 5. For example, the cleaning drainage 43 is returned to the second crystallization tank 7. May be.

  Further, before returning to the first crystallization tank 5 or the second crystallization tank 7, for example, a washing drainage decarboxylation means is installed, and an acid is added to the washing drainage 43 by the washing drainage decarboxylation means. Then, it may be configured such that the carbonate ions are removed by aeration or stirring while the pH is 5.5 or less and fine apatite crystals are dissolved.

  In the case where the cleaning wastewater 43 is decarboxylated by the cleaning wastewater decarboxylation means and then returned to the second crystallization tank 7, the recovery means for recovering the apatite crystals is used as the second crystallization tank. 7 for example, when the first crystallization tank 5 cannot be used due to maintenance, for example, or when the phosphate ion concentration of the phosphorus-containing wastewater 2 is low, the processing proceeds only in the second crystallization tank 7. It becomes possible to do.

  Next, a second embodiment will be described with reference to FIG. In addition, about the structure and effect | action same as the said 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  In the second embodiment, the crystallization water return means 34 provided in the crystallization water storage tank 29 is connected to the decarboxylation tower 3 as compared with the first embodiment. . That is, the washing waste water 43 and the crystallization treated water 6 are returned to the decarboxylation tower 3 by the crystallization treated water returning means 34.

  In this way, the cleaning wastewater 43 is returned to the decarbonation tower 3, and the decarbonation treatment is performed by aeration in a state where the pH is 5.5 or less in the decarbonation tower 3, so that the fineness contained in the cleaning wastewater 43 is reduced. Since the apatite crystal is once dissolved and re-precipitated with the seed crystal flowing at the time of crystallization treatment as a nucleus, the phosphorus recovery rate can be improved.

  Next, a third embodiment will be described with reference to FIG. In addition, about the structure and effect | action same as the said embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  This third embodiment includes a raw water tank 61 that stores phosphorus-containing wastewater 2 from pretreatment means or the like.

  The raw water tank 61 includes a pipe 62 having one end connected to the raw water tank 61, a pipe 63 having one end connected to the decarbonation tower 3, a pump 64 to which the other end of the pipe 62 and the other end of the pipe 63 are connected. Are connected to the decarbonation tower 3.

  The raw water tank 61 is connected to a pipe 65 connected to the washing drainage outlet 45 of the second crystallization tank 7. Then, the cleaning waste water 43 is returned from the second crystallization tank 7 through the pipe 65.

  That is, in the raw water tank 61, the biologically treated water and the washing wastewater 43 are mixed, and the phosphorus-containing wastewater containing a large amount of phosphate ions contained in the biologically treated water and fine apatite crystals contained in the washing wastewater 43. 66.

  Then, this phosphorus-containing wastewater 66 is supplied from the raw water tank 61 to the decarbonation tower 3 and subjected to decarbonation treatment. That is, in the decarboxylation tower 3, aeration is performed in a state where the acid is added and the pH is set to 5.5 or less to remove carbonate ions, and fine apatite crystals derived from the washing waste water 43 are dissolved.

  Thereafter, the crystallization process and the filtration crystallization process are performed as in the above embodiment.

Thus, by providing the raw water tank 61 and returning the cleaning waste water 43 to the raw water tank 61, the fine apatite crystals derived from the cleaning waste water 43 are dissolved by the decarboxylation treatment, and again the first crystallization tank 5 Since the crystallization treatment is performed at, the phosphorus recovery rate can be improved.

DESCRIPTION OF SYMBOLS 1 Phosphorus recovery apparatus 2 Phosphorus containing waste water 3 Decarbonation tower as decarbonation means 4 Decarboxylation treated water as phosphorus containing waste water 5 First crystallization tank as first reaction tank 6 Crystallization treatment as phosphorus containing waste water Water 7 Second crystallization tank as second reaction tank
17 Inner cylinder partition as partition member
18 Stirring means
19 Calcium addition means
20 Draft tube
25 Mixing section
26 Separation part
41 Filter bed
42 Filtered crystallization treated water as treated water
43 Cleaning drainage
44 Treated water outlet
45 Wash drain outlet
66 Wastewater containing phosphorus

Claims (11)

A phosphorus recovery device that adds calcium to phosphorus-containing wastewater, crystallizes apatite crystals by a crystallization reaction between phosphate ions in the phosphorus-containing wastewater and the calcium, and recovers phosphorus as the apatite crystals,
A first part having a mixing part for crystallizing apatite crystals by crystallization reaction of the phosphate ions and calcium, and a separation part for precipitating and separating the apatite crystals crystallized in the mixing part from phosphorus-containing wastewater. A reaction vessel;
A second reaction tank filled with apatite crystals as a filter bed,
In the second reaction tank, the phosphorus-containing wastewater treated in the first reaction tank is introduced in an upward flow. The first reaction tank has a mixing portion and a separation portion that are partitioned by a cylindrical partition member having an open bottom and a ceiling,
The mixing part is provided with a draft tube and a stirring means, and the stirring means forms an upward flow in the draft tube so that the content of the apatite crystal as a crystallization material in the mixing part is 10 g / The phosphorus recovery apparatus according to claim 1, wherein a circulation flow of L or more is generated. The phosphorus recovery apparatus according to claim 1 or 2, wherein the second reaction tank is filled with apatite crystals to form a filter bed of 0.5 m or more and less than 2 m. At least a part of the washing waste water that washed the filter bed of the second reaction tank is returned to the first reaction tank,
The phosphorus recovery apparatus according to any one of claims 1 to 3, wherein apatite crystals are recovered from at least one of the first reaction tank and the second reaction tank. In the first reaction tank, the pH is adjusted to 7.5 or more and 8.5 or less,
The phosphorus recovery apparatus according to any one of claims 1 to 4, wherein the pH in the second reaction tank is adjusted to be higher than the pH in the first reaction tank. At least one of the first reaction tank and the second reaction tank is provided with calcium addition means for adding calcium,
At least any one of the mixing part of the first reaction tank, the part into which the phosphorus-containing wastewater flows after being processed in the first reaction tank in the second reaction tank, and the bottom part of the second reaction tank The phosphorus recovery apparatus according to any one of claims 1 to 5, wherein calcium is added. The first stage of the first reaction tank is equipped with a decarboxylation means for removing carbonate ions by aeration or stirring in a state where acid is added to the phosphorus-containing wastewater and the pH is 5.5 or less,
The phosphorus recovery apparatus according to any one of claims 1, 2, 3, 5 and 6, wherein at least a part of the washing waste water that has washed the filter bed of the second reaction tank is returned to the decarbonation means. . A cleaning wastewater decarboxylation means for removing carbonate ions by aeration or stirring in a state where acid is added to at least a part of the cleaning wastewater that has washed the filter bed of the second reaction tank and the pH is 5.5 or less,
The cleaning wastewater after being treated by the cleaning wastewater decarboxylation means is returned to at least one of the first reaction tank and the second reaction tank. 8. The phosphorus recovery apparatus according to any one of 7 and 7. The second reaction tank has a treated water outlet from which treated water after treatment flows out, and a washing drain outlet from which washing waste water that has washed the filter bed is discharged,
The phosphorus recovery apparatus according to any one of claims 1 to 8, wherein the treated water outlet is installed at the same height as the washing drain outlet or above the washing drain outlet. Biological treatment of sewage, equipped with pretreatment means for solid-liquid separation of biologically treated water after biological treatment into phosphorus-containing wastewater and sludge,
The phosphorus recovery apparatus according to any one of claims 1 to 9, wherein the pretreatment means solubilizes the sludge to elute phosphorus. A phosphorus recovery method for adding calcium to phosphorus-containing wastewater, crystallizing apatite crystals by a crystallization reaction between phosphate ions and calcium in the phosphorus-containing wastewater, and recovering phosphorus as the apatite crystals,
Supplying phosphorus-containing wastewater and calcium to the first reactor;
The pH in the first reaction tank is adjusted to 7.5 or more and 8.5 or less,
Forming an upward flow inside the draft tube in the first reaction tank to generate a circulating flow having an apatite crystal concentration of 10 g / L or more, thereby producing crystals of phosphate ions and calcium of the phosphorus-containing wastewater. Apatite crystals are crystallized by the precipitation reaction,
Phosphorus-containing wastewater treated in the first reaction tank is supplied in an upward flow from the bottom of a second reaction tank filled with apatite crystals as a filter bed.

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