JP4581430B2 - Method and apparatus for treating fluorine-containing wastewater - Google Patents

Description

  The present invention relates to a method and apparatus for treating fluorine-containing wastewater, and in particular, treatment of fluorine-containing wastewater that causes fluorine in the wastewater to crystallize and remove by contacting the fluorine-containing wastewater with a seed crystal composed of fluorine and calcium. The present invention relates to a method and an apparatus.

  Conventionally, treatment of fluorine-containing wastewater has been carried out by adding a calcium compound such as slaked lime to produce calcium fluoride, and crystallization method or coagulation precipitation in which calcium fluoride is deposited on the surface of seed crystals composed of fluorine and calcium. By using this method, a method of removing the fluorine by solid-liquid separation of the generated calcium fluoride from the waste water is often employed. Thereby, the fluorine concentration in the treated water can be reduced to 10 to 15 mg / L.

  However, according to the Enforcement Order of the Water Pollution Control Law revised in 2001, the standard value for drainage into rivers was strengthened to 8 mg / L or less as a regulation related to fluorine. There was a problem that it was difficult to achieve the drainage standard value only by the precipitation method.

  In order to cope with this problem, a method of performing a high-level treatment of fluorine is employed after the crystallization method for separating the produced calcium fluoride or the coagulation precipitation method.

For advanced treatment of fluorine, aluminum compounds such as sulfated clay are added to agglomerate and precipitate fluorine in wastewater, and fluorine in the wastewater is adsorbed and removed using a fluorine adsorption resin. Adsorption removal methods have been proposed. Moreover, like patent document 1, the fluoroapatite containing calcium and phosphorus is formed by adding phosphoric acid and / or a phosphoric acid compound with a calcium compound with respect to fluorine-containing wastewater, and fluorine in wastewater There has been proposed a method for removing the above.
JP 2002-370093 A

  However, in the conventional advanced treatment of fluorine, the aluminum coagulation method has a disadvantage that the amount of sludge generated is larger than the amount of fluorine removed, and a space for the equipment is increased because a sedimentation basin is required. there were.

  In addition, in the adsorption removal method, the treated temporary treated water is usually in a neutral to alkaline range by adding a calcium compound, so the pH must be adjusted to 3 or less before the resin is passed through. Before discharging as treated water, the pH has to be readjusted to neutral, and there is a drawback that complicated operations are required for the entire treatment process.

  Furthermore, the method of Patent Document 1 only discloses that fluoroapatite is formed and fluorine is precipitated and removed, and a specific apparatus configuration is not disclosed. Furthermore, the problem regarding the residue of phosphorus in treated water by adding phosphoric acids and / or phosphoric acid compounds is not solved at all.

  The present invention has been made in view of such circumstances, and it is possible to stably reduce low-concentration wastewater having a fluorine concentration of 10 to 15 mg / L to a wastewater reference value of 8 mg / L or less, and to treat treated water. It is an object of the present invention to provide a method and apparatus for treating fluorine-containing wastewater that can minimize residual phosphorus.

In order to achieve the above object, the invention according to claim 1 is a method for treating fluorine-containing wastewater, in which calcium coexists and fluorine is crystallized and removed from low-concentration wastewater having a fluorine concentration of 10 to 15 mg / L. A crystallization reaction vessel comprising two stages of crystallization reaction tanks provided with a fluidized bed formed of a large number of seed crystals, and containing phosphorus in the crystallization reaction tank while sequentially passing the waste water. When the fluorine in the waste water is crystallized by injecting the liquid, the pH in the preceding crystallization reaction tank is adjusted to a range of 6 to 9, and the pH of the latter crystallization reaction tank is adjusted to the crystallization in the previous stage. For crystallization to be adjusted to 0.2 to 1.5 higher than the reaction tank, and to be injected into the preceding crystallization reaction tank out of the total injection amount to be injected into the preceding and subsequent crystallization reaction tanks The injection rate of the chemical amount is the amount of the crystallization chemical injected into the subsequent crystallization reaction tank. As will be 1 to 2 times the ratio, and wherein the dispensing controls all injection amount of the crystal析用agent.

  According to the present invention, the crystallization agent containing phosphoric acid is added to the low-concentration wastewater with the coexistence of calcium and the fluorine concentration of 10 to 15 mg / L, and in contact with the fluidized bed formed of seed crystals. To do. As a result, calcium and fluorine contained in the waste water react with phosphoric acid contained in the added crystallization agent to precipitate fluoroapatite and crystallize on the surface of the seed crystal. At this time, since the seed crystal is in a fluidized state, it can be efficiently crystallized with respect to fluorine present at a low concentration in the waste water. In this case, if the injection amount of the crystallization agent is too large, excess precipitate exceeding the crystallization on the seed crystal surface becomes a turbid substance containing fluorine or phosphorus and flows into the treated water. It becomes a factor to deteriorate the water quality. In addition, there is a problem that the crystallization reaction is not sufficiently performed within the time passing through the fluidized bed, and unreacted phosphorus remains in the treated water.

Therefore, in the present invention, a crystallization reaction tank having a fluidized bed formed of a large number of seed crystals is provided in two stages in series, and the crystallization reaction tank contains phosphorus in the crystallization reaction tank while sequentially passing the waste water. When the fluorine in the waste water is crystallized by injecting a chemical, the pH in the preceding crystallization reaction tank is adjusted to a range of 6 to 9, and the pH in the latter crystallization reaction tank is adjusted to A crystal that is adjusted to be 0.2 to 1.5 higher than the crystallization reaction tank and out of the total injection amount that is injected into the preceding and subsequent crystallization reaction tanks, the crystal that is injected into the preceding crystallization reaction tank. The total injection amount of the crystallization agent is divided so that the injection rate of the crystallization agent amount is 1 to 2 times the injection rate of the crystallization agent amount to be injected into the subsequent crystallization reaction tank. Note to be controlled.

  At this time, the pH of the waste water flowing into the crystallization reaction tank is preferably 9 or more. When adjusting the pH of the wastewater to the alkali side, a sodium compound is added, but the added sodium inhibits the formation of apatite. Therefore, if the pH of the waste water is 9 or more, the amount of sodium added can be reduced, so that the crystallization reaction in the crystallization reaction tank can be performed stably.

In order to achieve the above object, the invention according to claim 3 is a treatment apparatus for fluorine-containing wastewater that coexists with calcium and removes fluorine by crystallization from low-concentration wastewater having a fluorine concentration of 10 to 15 mg / L. In the processing apparatus, a crystallization reaction tank filled with a large number of seed crystals is provided in two stages in series, and the upper surface of the preceding crystallization reaction tank and the bottom of the subsequent crystallization reaction tank are connected by a connecting pipe. In addition to being connected to each of the preceding and subsequent crystallization reaction tanks, the seed crystal flows into the crystallization reaction tank by circulating a part of the treated water introduced from below the crystallization reaction tank. A flow means for forming a bed; a chemical injection means for injecting a crystallization chemical containing phosphoric acid into the crystallization reaction tank; and a pre-stage crystal and a post-stage crystal. Crystallization reaction is provided in each crystallization reaction tank. PH measuring means for measuring the pH of the inside, and based on the measured values of the respective pH measuring means, the pH of the latter crystallization reaction tank is higher than the pH of the preceding crystallization reaction tank by a predetermined pH difference. Of the total injection amount of the pH adjusting means to adjust and the crystallization agent to be injected into the preceding stage and the subsequent stage, the injection ratio of the amount of the crystallization agent injected into the crystallization reaction tank in the preceding stage is the crystallization reaction in the subsequent stage. And a drug adjusting means for dispensing the total injection amount of the crystallization drug so as to be a predetermined amount with respect to the injection ratio of the crystallization drug amount to be injected into the tank .

  Claim 3 constitutes a treatment apparatus for fluorine-containing wastewater. According to the third aspect, by providing the crystallization reaction tank in two stages in series, the processing load applied to the one-stage processing apparatus can be reduced. Moreover, since the maximum amount of the crystallization agent in the whole can be increased more than the equivalent amount corresponding to the reduction of 7 mg / L of fluorine, which is the maximum amount of addition in a single crystallization reaction tank, the phosphorus concentration in the treated water can be reduced. It can be suppressed and the fluorine concentration can be further reduced.
  Further, by adjusting the pH of the subsequent crystallization reaction tank to be higher than the pH of the previous crystallization reaction tank by a predetermined pH difference (for example, 0.2 to 1.5 in claim 5), In this crystallization reaction tank, the concentration of phosphorus remaining without crystallization reaction can be reduced. Thereby, the phosphorus concentration remaining in the treated water can be reduced.
  Moreover, although the maximum addition amount of the crystallization agent in the one-stage crystallization reaction tank is an amount corresponding to reducing fluorine by 7 mg / L, since the crystallization reaction tank is provided in two stages in series, More crystallization agent can be added as a total amount than the amount corresponding to a 7 mg / L reduction in fluorine. In addition, the dispensing means is arranged so that the injection amount of the crystallization agent in the preceding stage is a predetermined magnification (for example, 1 to 2 times that in claim 6) with respect to the injection amount of the crystallization agent in the crystallization reaction tank in the subsequent stage. I tried to control it. That is, the crystallization reaction is carried out at a high phosphorus concentration in the preceding crystallization reaction tank, and the remaining phosphorus is efficiently used for crystallization of fluorine in the latter crystallization reaction tank. Thereby, the phosphorus concentration remaining in the treated water can be minimized, and the fluorine concentration in the treated water can be efficiently reduced to a low concentration of 4 mg / L or less.

  The invention described in claim 4 is characterized in that an adjustment tank for adjusting the fluorine concentration in the waste water to a range of 10 to 15 mg / L is provided upstream of the crystallization reaction tank described in claim 3. Thereby, since the fluorine concentration of the waste_water | drain which flows into a crystallization reaction tank can be stabilized at 10-15 mg / L, the fluorine concentration of a treated water can be stably processed to 8 mg / L or less.

The invention according to claim 7 is the preceding crystallization reaction tank among the crystallization reaction tanks in which the total injection amount of the crystallization drug according to any one of claims 3 to 6 is provided in series in the two stages. And the superficial velocity of the latter crystallization reaction tank is 2 to 6 times the superficial velocity of the preceding crystallization reaction tank.

  The superficial velocity (SV) described here is the amount of wastewater treated relative to the volume of seed crystals charged in the crystallization reaction tank.

According to the seventh aspect of the present invention, a considerable amount of the crystallization drug for reducing fluorine, which is the maximum injection amount per stage, by 7 mg / L is injected only into the preceding crystallization reaction tank by the chemical injection means. Accordingly, fluorine is crystallized at a high phosphorus concentration in the preceding crystallization reaction tank, and the treated water remaining in a state where the fluorine concentration is low and the phosphorus concentration is high flows into the subsequent crystallization reaction tank. In the subsequent crystallization reaction tank, the inflow is set at a superficial velocity of 2 to 6 times the superficial velocity in the previous crystallization reaction tank, so that low-concentration fluorine is efficiently crystallized by the remaining phosphorus. Can be analyzed. Thereby, the phosphorus concentration discharged | emitted from a crystallization reaction tank of a back | latter stage can be reduced.

  As described above, according to the method and apparatus for treating fluorine-containing wastewater according to the present invention, low concentration wastewater having a fluorine concentration of 10 to 15 mg / L can be stably reduced to 8 mg / L or less of the wastewater standard value. In addition, residual phosphorus in the treated water can be minimized.

  Hereinafter, preferred embodiments of a method and apparatus for treating fluorine-containing wastewater according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing the configuration of a fluorine-containing wastewater treatment apparatus 10 according to the first embodiment of the present invention.

  The crystallization reaction tank 12 has a flow means by disposing an inflow pipe 14 on the bottom, an outflow pipe 16 on the top surface, and a return pipe 18 connected to the inflow pipe 14 on the inside upper side. A return pump 20 is provided in the return pipe 18, and a part of the treated water is returned from the upper part of the crystallization reaction tank 12 to the inflow pipe 14 by driving the return pump 20.

  The crystallization reaction tank 12 is provided with a crystallization part 12a having a structure capable of passing water, and the crystallization part 12a is filled with a large number of seed crystals (not shown). The seed crystal used is preferably a pellet obtained by granulating hydroxyapatite, fluoroapatite, and calcium phosphate crystals and powder, but may be any particle capable of forming fluoroapatite, such as calcium fluoride and Silica sand or the like may be used. The seed crystal particle size is preferably 2.0 mm or less.

  In addition, a pH sensor 22 as pH measuring means is installed inside the crystallization reaction tank 12, and a pH adjusting pipe 24 as pH adjusting means is connected to the inflow pipe 14. The pH sensor 22 constantly measures the pH in the tank and transmits the measured value to the attached pH adjustment control unit 26. The pH adjustment control unit 26 controls the driving of the pH adjustment pump 28 attached to the pH adjustment pipe 24 so that the transmitted measurement value is in the range of pH 6 to 9, preferably pH 7 to 8.5, and flows in. The amount of pH adjuster added to the tube 14 is adjusted. As the pH adjuster, hydrochloric acid, sulfuric acid, caustic soda, slaked lime and the like can be used without any particular limitation.

  Further, the outflow pipe 16 is provided with a fluorine sensor 30 as a fluorine concentration measuring means, and the inflow pipe 14 is connected with a medicine injection pipe 32 as a medicine injection means. The fluorine sensor 30 constantly measures the fluorine concentration in the treated water flowing through the outflow pipe 16, and transmits the measured value to the drug injection control unit 34 that is a control means. The drug injection control unit 34 includes a drug injection pump attached to the drug injection pipe 32 so that the difference in the fluorine concentration of the treated water with respect to the fluorine concentration of the waste water does not exceed 7 mg / L based on the transmitted measurement value. The amount of the crystallization agent injected into the inflow pipe 14 is adjusted by controlling the drive 36. As the crystallization agent used in the present invention, phosphoric acids and / or phosphoric acid compounds are preferable.

  Next, the operation of the processing apparatus 10 according to the first embodiment of the present invention configured as described above will be described.

  What should be noted in the present invention is that the wastewater to be treated has a fluorine concentration in the range of 10 to 15 mg / L and contains calcium. That is, since it is the same as the treated water obtained by the treatment by the conventional addition of calcium, by adopting the treatment apparatus 10 of the present invention to treat the treated water again, the fluorine concentration is 8 mg / L or less can be processed efficiently.

  That is, when wastewater containing fluorine in a range of 10 to 15 mg / L and containing calcium is caused to flow from the inflow pipe 14 into the crystallization reaction tank 12, the treated water flows out from the outflow pipe 16, A part is returned to the inflow pipe 14 by the return pipe 18. Thereby, an upward flow can be generated in the crystallization reaction tank 12 to form a fluidized bed of seed crystals filled in the crystallization part 12a.

  At the same time, since the crystallization agent is injected into the waste water passing through the inflow pipe 14 from the chemical injection pipe 32, the fluorine and calcium in the waste water react with the phosphoric acid of the crystallization agent in the crystallization part 12a and precipitate. The formed fluoroapatite is crystallized on the surface of the seed crystal. Since the crystallization of this fluoroapatite is performed on the seed crystal surface in a fluidized bed state, fluorine existing in a relatively low concentration in the waste water can be efficiently crystallized and removed.

  When crystallization of fluorine is performed, if the pH in the crystallization reaction tank 12 is low, the crystallization rate of phosphorus is lowered, so that the phosphorus concentration in the treated water is increased. On the other hand, if the pH in the crystallization reaction tank 12 is high, the precipitated fluoroapatite remains in the treated water without being crystallized on the surface of the seed crystal, so that the treated water becomes cloudy and the water quality deteriorates. .

  Therefore, the crystallization reaction tank 12 is provided with a pH sensor 22 and a pH adjustment pipe 24 equipped with a pH adjustment pump 28 so that the crystallization reaction tank 12 has a pH of 6 to 9, preferably a pH of 7 to 8.5. It was controlled by the pH adjustment control unit 26. Thereby, in the treated water from the crystallization reaction tank 12, an increase in the residual phosphorus concentration and white turbidity due to the precipitated fluoroapatite can be suppressed, and stable crystallization of fluorine can be performed.

  The amount of crystallization of fluorine is proportional to the amount of phosphoric acid in the crystallization agent to be added. However, if the amount of phosphoric acid is excessively increased, the concentration of phosphorus remaining in the treated water increases. May not meet the drainage standards. Therefore, the maximum addition amount of the crystallization agent added to the single-stage crystallization reaction tank 12 is within a range where the difference of the fluorine concentration of the treated water with respect to the fluorine concentration of the waste water does not exceed 7 mg / L, that is, the fluorine removal rate in the treated water Is preferably 50 to 60%.

  Therefore, in the treatment apparatus 10 of the present invention, the crystallization reaction tank 12 is provided with a fluorine sensor 30, and the chemical injection control unit 34 uses the chemical injection pipe 32 so that the fluorine removal rate in the treated water is 50 to 60%. The amount of the crystallization drug injected was adjusted. As a result, the concentration of phosphorus remaining in the treated water can be minimized, and the fluorine concentration in the treated water can be reduced to 8 mg / L or less.

  FIG. 2 is a block diagram showing the configuration of the processing apparatus 40 according to the second embodiment of the present invention. The amount of the crystallization agent dispensed into each tank by providing two tanks in series. This is an example of adjusting.

  In the first and second crystallization reaction tanks 42 and 44, crystallization parts 42a and 44a filled with seed crystals (not shown) are provided.

  An inflow pipe 46 is installed at the bottom of the crystallization reaction tank 42 at the front stage, and an outflow pipe 48 is installed at the upper surface of the crystallization reaction tank 44 at the rear stage. The bottom of the crystallization reaction tank 44 is connected by a connecting pipe 50. The upstream return pipe 52 connects the inside upper side of the upstream crystallization reaction tank 42 and the inflow pipe 46, and a part of the treated water in the upstream crystallization reaction tank 42 flows in by driving the attached upstream return pump 52 a. Return to tube 46. The rear return pipe 54 connects the upper side of the rear stage crystallization reaction tank 44 and the connecting pipe 50, and a part of the treated water in the rear stage crystallization reaction tank 44 is driven by the attached rear return pump 54 a. Is returned to the connecting pipe 50. Thus, an upward flow that flows in the direction indicated by the black arrows in FIG. In addition, it is preferable that the superficial velocity in the crystallization reaction tanks 42 and 44 of the front | former stage and back | latter stage is the range of SV5-20.

  A connection pump 56 is installed in the connection pipe 50, and the flow rate from the preceding crystallization reaction tank 42 to the subsequent crystallization reaction tank 44 can be adjusted by driving thereof.

  The front and rear crystallization reaction tanks 42 and 44 are respectively provided with pH sensors 58 and 60 which are pH measuring means, and the pH of the front and rear crystallization reaction tanks 42 and 44 is constantly measured. Further, pH adjusting pipes 62 and 64, which are pH adjusting means, are connected to the inflow pipe 46 and the connecting pipe 50, respectively, and are injected into the inflow pipe 46 and the connecting pipe 50 by driving the pH adjusting pumps 62a and 64a attached thereto. The amount of pH adjuster is adjusted. As the pH adjuster, hydrochloric acid, sulfuric acid, caustic soda, slaked lime and the like can be used without any particular limitation. The pH adjustment control unit 66 connects the pH sensors 58 and 60 and the pH adjustment pumps 62a and 64a, and receives measurement values measured by the pH sensors 58 and 60. Then, while controlling the driving of the pH adjusting pump 62a at the front stage so that the measured value of the pH sensor 58 at the front stage is pH 6-9, preferably pH 7-8.5, the measured value of the pH sensor 60 at the rear stage is The driving of the pH adjustment pump 64a at the subsequent stage is controlled so that it is 0.2 to 1.5 higher than the measured value of the pH sensor 58.

  Further, drug injection pipes 68 and 70, which are drug injection means, are connected to the inflow pipe 46 and the connecting pipe 50, respectively, and the crystallization drug is injected by driving the attached drug injection pumps 68a and 70a. As the crystallization agent, it is preferable to use phosphoric acids or / and phosphoric acid compounds. In each of the chemical injection pumps 66a and 68a, the amount of the crystallization chemical injected into the preceding crystallization reaction tank 42 is 1 to 2 times the amount of the crystallization chemical injected into the subsequent crystallization reaction tank 44. The drive is adjusted so that In addition, if the total amount of the crystallization agent used in the processing apparatus 40 is about 50 mg / L in terms of phosphorus concentration, wastewater having a fluorine concentration of 15 mg / L can be reduced to 6 mg / L or less. Therefore, under the above conditions, the amount of the crystallization drug injected from the preceding drug injection tube 68 is in the range of 25 to 33 mg / L in phosphorus concentration, and the crystal injected from the subsequent drug injection tube 70. The amount of drug for analysis is preferably in the range of 16 to 25 mg / L in terms of phosphorus concentration.

  Next, the operation of the processing apparatus 40 according to the second embodiment of the present invention configured as described above will be described.

  In the processing apparatus 40, the waste water is processed in two stages in series in the crystallization reaction tanks 42 and 44 in the former stage and the latter stage. Thereby, since the processing load concerning each tank 42 and 44 can be reduced, a fluorine can be removed stably.

  By the way, it is preferable that the maximum addition amount of the crystallization agent in the one-stage crystallization reaction tank is an amount corresponding to a 7 mg / L reduction in fluorine considering the concentration of phosphorus remaining in the treated water. Since the treatment apparatus 40 of the present invention is provided in two stages in series, the maximum addition amount of the crystallization agent in the entire treatment apparatus 40 may be made larger than the amount corresponding to reducing fluorine by 7 mg / L. it can. In addition, the crystallization reaction tank 42 in the former stage was injected with an amount of the crystallization agent 1 to 2 times that in the crystallization reaction tank 44 in the subsequent stage.

  For this reason, in the crystallization reaction tank 42 in the previous stage, the crystallization by the phosphorus, fluorine and calcium is positively brought into contact with the fluidized bed of the seed crystal formed in the crystallization part 42a in a state where the phosphorus concentration is 1 to 2 times higher. The reaction takes place and a large amount of fluorine can be crystallized in the seed crystal. At this time, the wastewater treated in the crystallization reaction tank 42 in the former stage is in a state in which unreacted phosphorus remains although the fluorine concentration is lowered. The amount of drug for analysis is reduced. Accordingly, since the phosphorus remaining in the crystallization reaction tank 44 in the subsequent stage can be efficiently used for the crystallization reaction, the concentration of phosphorus remaining in the treated water in the crystallization reaction tank 44 in the subsequent stage is ensured. Can be reduced, and fluorine existing at a low concentration can be efficiently crystallized.

  Further, the pH of the subsequent crystallization reaction tank 44 is set to be 0.2 to 1.5 higher than the pH of the previous crystallization reaction tank 42. Thereby, phosphorus remaining in the preceding crystallization reaction tank 42 can be efficiently crystallized in the subsequent crystallization reaction tank 44, so that the concentration of phosphorus remaining in the treated water can be minimized.

  Therefore, by adopting the treatment apparatus 40 of the present invention, the concentration of phosphorus remaining in the treated water can be minimized with respect to the wastewater containing calcium having a fluorine concentration in the range of 10 to 15 mg / L and containing calcium. At the same time, the fluorine concentration can be efficiently reduced to 4 mg / L or less.

  FIG. 3 is a block diagram showing the configuration of the processing apparatus 90 according to the third embodiment of the present invention, which is an example in which a two-stage crystallization reaction tank is provided in series to adjust the superficial velocity. Note that the same devices and members as those of the processing device 40 according to the second embodiment of the present invention shown in FIG.

  According to the processing apparatus 90 of the present invention, each return pump 52a, so that the superficial velocity in the subsequent crystallization reaction tank 44 is 2 to 6 times the superficial velocity in the previous crystallization reaction tank 42. The drive of 54a and the connection pump 56, the volume of each crystallization part 42a, 44a, and the filling amount of a seed crystal are set. The material and particle size of the seed crystal filled in the latter stage crystallization reaction tank 44 are preferably the same as those in the former stage crystallization reaction tank 42, but are not particularly limited, and those different from the former stage are used. May be. Moreover, although the return pipe 54 and the return pump 54a are provided in the latter stage crystallization reaction tank 44, it is not specifically limited. As long as an upward flow can be generated in the subsequent crystallization reaction tank 44 and the superficial velocity can be maintained under the above-described conditions, it is not necessary to install it. Furthermore, a means for re-adding the required amount of calcium may be provided in the crystallization reaction tanks 42 and 44 in the former stage and the latter stage. Thereby, a more efficient crystallization reaction can be performed.

  Further, in the processing apparatus 90, a chemical injection pipe 68 as a chemical injection means is installed only in the inflow pipe 46, which is equivalent to reducing the maximum addition amount in the crystallization reaction tank 42 in the preceding stage, that is, fluorine by 7 mg / L. A sufficient amount of the crystallization agent is injected into the crystallization reaction tank 42 in the previous stage.

  Therefore, in the processing apparatus 90, the crystallization reaction is performed in the upstream crystallization reaction tank 42 at a high phosphorus concentration, and the remaining crystallization in the subsequent crystallization reaction tank 44 is used to crystallize at a high superficial velocity. Reaction takes place. As a result, the fluorine in the waste water can be actively crystallized in the crystallization reaction tank 42 in the former stage to reduce the fluorine concentration, and the phosphorus in which the low concentration of fluorine remains in the crystallization reaction tank 44 in the latter stage. Crystallization can be performed efficiently.

  From these facts, by adopting the treatment apparatus 90 of the present invention, the fluorine concentration is in the range of 10 to 15 mg / L, and the phosphorus concentration remaining in the treated water is minimized with respect to the waste water containing calcium. While being able to suppress, the process which can reduce a fluorine density | concentration to 8 mg / L or less can be performed efficiently.

  In the processing apparatuses 10, 40, and 90 described above, the number, shape, material, and the like of each member and apparatus are not particularly limited.

  Moreover, in the processing apparatus 10, 40, 90, although drainage | emission in the range whose fluorine concentration is 10-15 mg / L was made into object, it does not specifically limit. If an adjustment tank (not shown) for adjusting the fluorine concentration of the wastewater to the range of 10 to 15 mg / L is provided in the uppermost stream, it can be applied to fluorine-containing wastewater of 15 mg / L or more.

  (Example 1) In Example 1, a treatment test of fluorine-containing waste water was conducted using the treatment apparatus 10 shown in FIG.

As the crystallization reaction tank 12, a cylindrical tank having an inner diameter of 750 mm and a height of 4000 mm was used. The crystallization part 12a was filled with 1 m ³ of a seed crystal composed of hydroxyapatite and calcium phosphate and having an average particle diameter of 0.8 mm. And the superficial velocity of the crystallization reaction tank 12 was set to SV5 by adjusting the waste water supply amount of the crystallization reaction tank 12 to 5 m ³ / h and the flow rate of the return pipe 18 to 30 m ³ / h.

  Further, in the drug injection tube 32, the drug injection control unit 34 controlled the driving of the drug injection pump 36 so that the phosphorus concentration in the injected crystallization drug was 19 mg / L with respect to the waste water.

  Further, caustic soda was used as a pH adjusting agent, and the pH adjustment control unit 26 controlled the driving of the pH adjusting pump 28 so that the measured value of the pH sensor 22 became pH 7.0 to 7.5.

  As the waste water to be tested, treated water obtained by treating hydrofluoric acid-containing water generated in the metal surface treatment process by a coagulation precipitation method by adding calcium was used. In addition, the fluorine concentration of the test waste water was in the range of 10 to 12 mg / L, and the calcium concentration was in the range of 300 to 1000 mg / L.

  The results are shown below. Table 1 shows the average pH and concentration of each component in the wastewater and treated water.

表１に示すように、処理水は排水と比べてｐＨやＳＳを特に変動させることなく、リン濃度が０．７ｍｇ／Ｌに抑制されるとともに、フッ素濃度が６．９ｍｇ／Ｌまで低減された。したがって、本発明の処理装置１０を採用することにより、フッ素濃度が１０〜１５ｍｇ／Ｌの範囲であり、かつカルシウムを含有する排水に対して、処理水中のフッ素濃度を排水基準値である８ｍｇ／Ｌ以下に処理できることが判明した。

As shown in Table 1, in the treated water, the phosphorus concentration was suppressed to 0.7 mg / L and the fluorine concentration was reduced to 6.9 mg / L without particularly changing pH and SS as compared with the waste water. . Therefore, by adopting the treatment apparatus 10 of the present invention, the fluorine concentration in the treated water is 8 mg / L, which is the drainage standard value, for the wastewater containing calcium in the range of 10 to 15 mg / L and containing calcium. It turned out that it can process below L.

  (Example 2) In Example 2, a treatment test of fluorine-containing wastewater was conducted using the treatment apparatus 90 shown in FIG.

A cylindrical tank having an inner diameter of 750 mm and a height of 4000 mm is used as the crystallization reaction tank 42 in the previous stage. The seed crystal was filled with 1 m ³ . Then, by adjusting the waste water supply amount of the crystallization reaction tank 42 in the previous stage to 5 m ³ / h and the flow rate of the return pipe 18 to 30 m ³ / h, the superficial velocity in the crystallization reaction tank 42 in the previous stage is set to SV5. Set to.

  In addition, in the former-stage drug injection tube 68, the drive of the previous-stage drug injection pump 68a was adjusted so that the phosphorus concentration in the injected crystallization drug was 30 mg / L with respect to the waste water.

  Further, caustic soda was used as a pH adjuster, and the pH adjustment control unit 26 controlled the drive of the previous pH adjustment pump 28 so that the measured value of the previous pH sensor 22 was pH 7.0 to 7.5.

  On the other hand, a vinyl chloride column having an inner diameter of 50 mm and a height of 1000 mm is used as the latter stage crystallization reaction tank 44, and the latter stage crystallization part 44a is filled with 1 L of the same seed crystal as the former stage crystallization part 42a. It was done. Moreover, the superficial velocity in the latter crystallization reaction tank 44 is set to SV20 by adjusting the waste water supply amount of the latter crystallization reaction tank 44 to 20 L / h and the flow rate of the return pipe 18 to 160 L / h. did.

  As the waste water to be tested, treated water obtained by treating hydrofluoric acid-containing water generated in the metal surface treatment process by a coagulation precipitation method by adding calcium was used. In addition, the fluorine concentration of the test waste water was in the range of 10 to 12 mg / L, and the calcium concentration was in the range of 300 to 1000 mg / L.

  Caustic soda was used as the pH adjusting agent, and the pH adjustment control unit 66 controlled the driving of the pH adjusting pump 62a so that the measured value of the pH sensor 58 at the previous stage was pH 7.0 to 7.5.

  The results are shown in Table 2. Table 2 shows drainage, treated water in the preceding crystallization reaction tank 42 (hereinafter referred to as the treated water in the preceding stage), treated water in the subsequent crystallization reaction tank 44 (hereinafter referred to as the treated water in the subsequent stage). The average water quality is shown.

表２に示すように、フッ素濃度は前段及び後段の晶析反応槽４２，４４に差が見られなかったものの、リン濃度は後段の晶析反応槽４４において低下した。したがって、本発明の処理装置９０を採用することにより、フッ素濃度が１０〜１５ｍｇ／Ｌの範囲であり、かつカルシウムを含有する排水に対し、処理水中に残存するリン濃度を最小限に抑制できるとともに、フッ素濃度を排水基準値である８ｍｇ／Ｌ以下に安定して処理できることが判明した。

As shown in Table 2, although there was no difference in the fluorine concentration between the first and second crystallization reaction tanks 42 and 44, the phosphorus concentration decreased in the second crystallization reaction tank 44. Therefore, by adopting the treatment apparatus 90 of the present invention, the concentration of phosphorus remaining in the treated water can be minimized with respect to the wastewater containing calcium having a fluorine concentration in the range of 10 to 15 mg / L and containing calcium. It has been found that the fluorine concentration can be stably treated to the drainage standard value of 8 mg / L or less.

  (Example 3) In Example 3, in order to investigate the relationship between the phosphorus removal rate and the superficial velocity, a treatment test of fluorine-containing wastewater was conducted using the treatment device 90 of FIG.

  The drainage used was one containing calcium and having a fluorine concentration in the range of 10 to 15 mg / L. In the crystallization reaction tank 42 in the previous stage, the superficial velocity is set to SV5, the pH is set to 7.5 ± 0.5, and the injection amount of the crystallization drug injected from the drug injection pipe 68 is 35 mg / day in the phosphorus concentration. L. On the other hand, in the latter stage crystallization reaction tank 44, the treated water in the former stage had a fluorine concentration of 8 mg / L or less and the remaining phosphorus concentration was 3 mg / L at the maximum. Then, by changing the amount of inflow of the treated water in the former stage into the crystallization reaction tank 44 in the latter stage, the empty space in the crystallization reaction tank 44 in the latter stage with respect to the superficial velocity (SV) of the crystallization reaction tank 42 in the former stage. The rate of removal of phosphorus was measured by changing the rate (SV) ratio to 2 to 10 times. Other conditions are the same as in Example 2.

  The result is shown in FIG. FIG. 4 is a graph showing the phosphorus removal rate in the treated water with respect to the ratio of the superficial velocity (SV) in the subsequent crystallization reaction tank 44.

  As can be seen from FIG. 4, when the superficial velocity (SV) of the latter crystallization reaction tank 44 is 2 to 6 times the superficial velocity (SV) of the former crystallization reaction tank, the phosphorus removal rate is high. Although it was 80% or more, when it exceeded 6 times, the phosphorus removal rate decreased rapidly.

  From this, the superficial velocity in the latter stage crystallization reaction tank remains in the treated water by performing treatment in the range of 2 to 6 times the superficial velocity (SV) of the former stage crystallization reaction tank. It has been found that the treatment can be performed with the phosphorus concentration suppressed to a minimum.

The block diagram which showed the structure of the processing apparatus which is the 1st Embodiment of this invention The block diagram which showed the structure of the processing apparatus which is the 2nd Embodiment of this invention. The block diagram which showed the structure of the processing apparatus which is the 3rd Embodiment of this invention. Graph showing the ratio of superficial velocity to phosphorus removal rate in treated water in the latter crystallization reaction tank

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10,40,90 ... Processing apparatus, 12 ... Crystallization reaction tank, 12a ... Crystallization part, 14 ... Inflow pipe, 16 ... Outflow pipe, 18 ... Return pipe, 20 ... Return pump, 22 ... pH sensor, 24 ... pH Adjustment pipe, 26 ... pH adjustment control unit, 28 ... pH adjustment pump, 30 ... Fluorine sensor, 32 ... Drug injection pipe, 34 ... Drug injection control unit, 36 ... Drug injection pump, 42 ... Preliminary crystallization reaction tank, 44 ... latter stage crystallization reaction tank, 46 ... inflow pipe, 48 ... outflow pipe, 50 ... connecting pipe, 52 ... front stage return pipe, 52a ... front stage return pump, 54 ... rear stage return pipe, 54a ... rear stage return pump , 56 ... connection pump, 58 ... front-stage pH sensor, 60 ... rear-stage pH sensor, 62 ... front-stage pH adjustment pipe, 62a ... front-stage pH adjustment pump, 64 ... rear-stage pH adjustment pipe, 64a ... rear-stage pH adjustment Pump, 66... PH adjustment control unit, 68 Preceding drug infusion tubes, 68a ... front of the infusion pump, 70 ... subsequent drug infusion tubes, 70a ... subsequent infusion pump

Claims (7)

A method for treating fluorine-containing wastewater, in which calcium coexists and fluorine is crystallized and removed from wastewater having a low concentration of 10 to 15 mg / L.
A crystallization reaction tank having a fluidized bed formed of a large number of seed crystals is provided in two stages in series, and a crystallization agent containing phosphorus is injected into the crystallization reaction tank while sequentially passing the waste water. When crystallization of fluorine in the waste water by
The pH in the preceding crystallization reaction tank is adjusted to a range of 6 to 9, and the pH in the subsequent crystallization reaction tank is adjusted to be 0.2 to 1.5 higher than that in the previous crystallization reaction tank. With
Of the total injection amount injected into the preceding and subsequent crystallization reaction tanks, the injection ratio of the amount of crystallization agent injected into the preceding crystallization reaction tank is for crystallization injected into the subsequent crystallization reaction tank. A method for treating fluorine-containing wastewater , wherein the total injection amount of the crystallization drug is controlled to be 1 to 2 times the injection rate of the drug amount .   The method for treating fluorine-containing wastewater according to claim 1, wherein the pH of the wastewater flowing into the crystallization reaction tank is 9 or more. A treatment apparatus for fluorine-containing wastewater that coexists with calcium and removes fluorine by crystallization from low-concentration wastewater having a fluorine concentration of 10 to 15 mg / L,
In the processing apparatus, crystallization reaction tanks filled with a large number of seed crystals are provided in two stages in series, and the upper surface of the preceding crystallization reaction tank and the bottom of the subsequent crystallization reaction tank are connected by a connecting pipe. ,
A flow that is provided in each of the preceding and subsequent crystallization reaction tanks, and forms a fluidized bed of seed crystals in the crystallization reaction tank by circulating a part of the water treated by flowing in from below the crystallization reaction tank. Means,
A chemical injection means for injecting a crystallization chemical containing phosphoric acid into the crystallization reaction tank;
PH measurement means for measuring pH in the crystallization reaction tank provided in the crystallization reaction tank in the former stage and the latter stage, respectively.
PH adjusting means for adjusting the pH of the subsequent crystallization reaction tank based on the measured values of the respective pH measuring means so as to be higher than the pH of the preceding crystallization reaction tank by a predetermined pH,
Of the total injection amount of the crystallization agent to be injected into the preceding stage and the subsequent stage, the injection ratio of the amount of the crystallization agent to be injected into the preceding crystallization reaction tank is used for the crystallization to be injected into the subsequent crystallization reaction tank. A fluorine-containing wastewater treatment apparatus , comprising: a medicine adjusting unit that dispenses a total amount of the crystallization drug to be injected in a predetermined amount with respect to an injection ratio of the drug amount .   The apparatus for treating fluorine-containing wastewater according to claim 3, wherein an adjustment tank for adjusting the fluorine concentration in the wastewater to a range of 10 to 15 mg / L is provided upstream of the crystallization reaction tank. The pH adjusting means is such that the measured value of the pH measuring means in the subsequent crystallization reaction tank is 0.2 to 1.5 higher than the measured value of the pH measuring means in the preceding crystallization reaction tank . The apparatus for treating fluorine-containing wastewater according to claim 3 or 4 , wherein the pH adjustment control means is adjusted . Wherein the agent adjusting means, injection rate of crystallization析用agent to be injected into the crystallization reaction tank of the previous stage, one to two times the injection rate of crystallization析用agent to be injected into the crystallization reaction tank of the subsequent The apparatus for treating fluorine-containing wastewater according to any one of claims 3 to 5, wherein the total injection amount is dispensed . The total injection amount of the crystallization agent is injected into the preceding crystallization reaction tank in the crystallization reaction tank provided in two stages in series, and the superficial velocity of the latter crystallization reaction tank is The apparatus for treating fluorine-containing wastewater according to any one of claims 3 to 6, wherein the treatment rate is 2 to 6 times the superficial velocity of the crystallization reaction tank.

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