JP4883495B2 - Fluorine-containing wastewater treatment method and fluorine-containing wastewater treatment equipment - Google Patents

Description

  The present invention relates to a method for treating fluorine-containing wastewater and an apparatus for carrying out this treatment.

  In semiconductor manufacturing factories and related factories, fluorine-containing wastewater mainly containing hydrofluoric acid or ammonium fluoride is discharged. Conventionally, such fluorine-containing wastewater has been subjected to a treatment such as coagulation precipitation by generating a hardly soluble calcium fluoride by adding calcium salt such as calcium hydroxide several times the equivalent. However, the method of removing fluorine by generating poorly soluble calcium fluoride has a problem that a large amount of sludge having poor sedimentation properties is generated, and reduction of this sludge generation amount is a problem.

On the other hand, as a measure to reduce the amount of sludge generated, the fluorine-containing wastewater is passed through a calcium carbonate packed tower to remove fluorine from the fluorine-containing wastewater by converting fluorine into granular calcium fluoride. A method of recovering calcium fluoride is known. In this method, in order to almost completely convert calcium carbonate to calcium fluoride, it is necessary to continue water flow until the fluorine concentration in the liquid in the calcium carbonate packed tower is substantially the same as the fluorine-containing waste water (raw water). is there. As means for determining changes in fluorine concentration, it is known to install PH meters and fluorine concentration meters at the inlet and outlet of the calcium carbonate packed tower (see, for example, Patent Document 1).
Japanese Patent No. 3466737

  However, fluorine-containing wastewater often contains alkali components (such as ammonium fluoride and ammonia) and acid components (such as sulfuric acid and nitric acid), and the concentration is not constant. Then, the alkaline component destabilizes the quality of the treated water flowing out from the calcium carbonate packed tower, and the acid component dissolves the calcium carbonate in the packed tower. Furthermore, since these acid components and alkali components affect the pH, it becomes an obstacle to detecting changes in the fluorine concentration in the liquid in the calcium carbonate packed tower. That is, the pH of the fluorine-containing waste water varies depending on the contents of acid components and alkali components. For this reason, if the completion of conversion to calcium fluoride is detected by the same pH at the inlet and outlet of the calcium carbonate packed tower, the purity of the recovered calcium fluoride may become unstable. There is. In some cases, even though the conversion from calcium carbonate to calcium fluoride has already been almost completely completed, water may continue to flow more than necessary.

  In contrast, when fluorine concentration meters are installed at the inlet and outlet of the calcium carbonate packed tower, high-purity calcium fluoride can be recovered stably. However, in this case, it cannot be solved that the quality of the treated water flowing out from the calcium carbonate packed tower becomes unstable due to the alkali component or acid component contained in the fluorine-containing waste water.

  Moreover, the carbonate concentration of the treated water stably processed in the calcium carbonate packed tower is high. For this reason, in the merry-go-round system as disclosed in Patent Document 1, there is a problem in that the calcium carbonate that dissolves without contributing to fluorine removal increases in the latter-stage calcium carbonate packed tower, resulting in poor efficiency.

  Therefore, in the present invention, when treating fluorine-containing wastewater, it is possible to stably recover high-purity calcium fluoride, obtain a stable treated water quality, and prevent wasteful discharge of calcium carbonate. It aims at providing the processing method of the fluorine-containing waste water which can perform, and the apparatus for implementing this.

  The fluorine-containing wastewater treatment method according to the present invention for achieving the above object is a fluorine-containing wastewater treatment method using a fluorine-containing wastewater treatment apparatus having a plurality of calcium carbonate packed towers. A pH adjustment step for adjusting the pH to generate raw water, and passing the raw water subjected to PH adjustment to a first calcium carbonate packed tower to remove fluorine from the raw water and discharge it as treated water. After the one tower treatment step and the treated water PH discharged from the first calcium carbonate packed tower is lower than the treated water PH in the initial stage of water flow to become fluorine residual treated water, the first carbonate The treatment in the calcium packed tower is switched to high purity calcium fluoride production, and the fluorine residual treated water is passed through the second calcium carbonate packed tower to remove fluorine from the fluorine residual treated water. A multi-stage tower treatment step for producing treated water, and after the fluorine residual treated water discharged from the first calcium carbonate packed tower is lowered to be close or equal to the pH of the raw water, A secondary single tower treatment step of generating treated water by stopping water flow to the first calcium carbonate packed tower and allowing the raw water to flow to the second calcium carbonate packed tower, After the secondary single tower treatment process, the multistage treatment process using another calcium carbonate packed tower and the secondary single tower treatment process are sequentially repeated, and the water is stopped from the calcium carbonate packed tower where water flow is stopped. It is characterized by extracting calcium calcium and filling calcium carbonate packed tower from which calcium fluoride is extracted with new calcium carbonate.

  Further, in the method for treating fluorine-containing wastewater having the characteristics as described above, the extraction of calcium fluoride from the calcium carbonate packed tower and the filling of calcium carbonate are started during the secondary single tower treatment step, It is preferable to determine the number of calcium carbonate packed towers used for the treatment of fluorine-containing waste water based on the number of the multistage treatment steps repeated until the filling of calcium carbonate is completed. By determining the number of calcium carbonate packed towers used for the treatment of fluorine-containing wastewater by such a method, the treatment of fluorine-containing wastewater is not delayed. Further, by determining the number of calcium carbonate packed towers by such a method, useless calcium carbonate packed towers are eliminated during the treatment process of fluorine-containing waste water.

  Moreover, in the processing method of the fluorine-containing waste water which has the above characteristics, the said calcium carbonate packed tower is made into 2 towers, While the secondary single tower processing process by the said 2nd calcium carbonate packed tower is performed Pulling out calcium fluoride from the first calcium carbonate packed tower and filling calcium carbonate, and the second single tower treatment step by the first calcium carbonate packed tower is being performed. The secondary single tower treatment step and the multistage tower treatment step may be repeated with two calcium carbonate packed towers by extracting calcium fluoride from the calcium carbonate packed tower and filling with calcium carbonate. it can. By treating the fluorine-containing wastewater by such a method, it is possible to efficiently treat the fluorine-containing wastewater with the minimum number of towers packed with calcium carbonate.

  Furthermore, in the method for treating fluorine-containing wastewater having the above-described features, the fluorine residual treated water is discharged to a fluorine residual treated water storage tank, and the fluorine residual treated water storage tank is transferred to the second calcium carbonate packed tower. It is better to actively carry out water flow. By actively performing water flow to the second calcium carbonate packed tower, it becomes possible to provide fluorine residual treated water directly to the calcium carbonate packed tower or in the immediate vicinity of the calcium carbonate packed tower, An increase in SS (Suspended Solids) due to the aggregation reaction can be suppressed.

  In addition, a fluorine-containing wastewater treatment apparatus according to the present invention for achieving the above object is a fluorine-containing wastewater treatment apparatus having a plurality of calcium carbonate packed towers, and the raw water to be passed through the calcium carbonate packed towers PH adjusting means for adjusting PH, PH meter for measuring PH of treated water discharged from the calcium carbonate packed tower, each provided in each of the plurality of calcium carbonate packed towers, and calcium carbonate packed to supply the raw water A raw water supply valve that defines a tower, a treated water discharge valve that connects a discharge path for discharging treated water to the outside of the system, and a discharge port of the calcium carbonate packed tower, and a residual treatment of fluorine discharged from one calcium carbonate packed tower Based on the value measured by the fluorine residual treatment water discharge valve for supplying water to another calcium carbonate packed tower and the PH meter, the raw water supply valve , Treated water discharge valve, valve control means for controlling the opening and closing of the fluorine residual treated water discharge valve, and raw water supply pump for feeding the raw water to an optional calcium carbonate packed tower, the valve control means, When the raw water supply valve to one calcium carbonate packed tower is open, the treated water discharge valve connected to the one calcium carbonate packed tower is opened, the fluorine residual treated water discharge valve is closed, and the one When the PH value measured by the PH meter connected to the calcium carbonate packed tower is lowered, the treated water discharge valve is closed, the fluorine residual treated water discharge valve is opened, and connected to the other calcium carbonate packed tower The treated water discharge valve is opened, the fluorine residual treated water discharge valve is closed, and measured by a PH meter connected to the one calcium carbonate packed tower. When the PH value is close or equal to the adjusted PH of the raw water, the raw water supply valve to the one calcium carbonate packed tower is closed, and the raw water supply valve to the other calcium carbonate packed tower is closed. It is characterized by controlling to open.

  In addition, the fluorine-containing wastewater treatment apparatus having the above-described features includes a fluorine residual treated water storage tank that stores fluorine residual treated water discharged from the one calcium carbonate packed tower, and the fluorine residual treated water storage tank. A fluorine residual treated water supply valve for supplying the fluorine residual treated water to the other calcium carbonate packed tower, and a pump for feeding the fluorine residual treated water from the fluorine residual treated water storage tank to the other calcium carbonate packed tower The valve control means may open and close the fluorine residual treated water supply valve in synchronization with the opening and closing timing of the fluorine residual treated water discharge valve. By adopting such a configuration, it becomes possible to provide fluorine residual treated water directly to other calcium carbonate packed towers or in the immediate vicinity of other calcium carbonate packed towers, and to increase SS due to agglomeration reaction. Can be suppressed.

  Further, in the fluorine-containing wastewater treatment apparatus having the above-described characteristics, each of the calcium carbonate packed towers circulates water at the upper part of the packed tower and from below the discharge port toward the lower part of the packed tower. A route may be provided. By setting it as such a structure, the particle | grains of the calcium carbonate with which it filled in the calcium carbonate packed tower can be floated, and an expanded bed can be formed. By forming the expanded bed, it is possible to prevent the granular calcium carbonates from sticking to each other and the carbon dioxide gas discharged from the calcium carbonate from being accumulated in the calcium carbonate packed tower, and the reaction stoppage can be suppressed.

  According to the method for treating fluorine-containing wastewater according to the present invention, high-purity calcium fluoride can be stably recovered from fluorine-containing wastewater. Moreover, the treated water of the stable water quality can be obtained. Furthermore, in the latter-stage calcium carbonate packed tower, the amount of calcium carbonate that dissolves without contributing to fluorine removal can be suppressed.

  Further, according to the apparatus for treating fluorine-containing wastewater according to the present invention, the above-described method can be carried out, and high-purity calcium fluoride can be stably recovered from the fluorine-containing wastewater. It is possible to stabilize the water quality of the water, and it is possible to suppress wasteful outflow of calcium carbonate.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a method and apparatus for treating fluorine-containing wastewater of the present invention will be described in detail with reference to the drawings.
First, a configuration of a fluorine-containing wastewater treatment apparatus (hereinafter simply referred to as a treatment apparatus 100) according to the present embodiment will be described with reference to FIG. The processing apparatus 100 according to the present embodiment includes a plurality of (three in the form shown in FIG. 1) calcium carbonate packed towers 30 (first calcium carbonate packed tower 30a to third calcium carbonate packed tower 30c), and PH adjustment. A tank 12 and a fluorine-containing drainage storage tank 10 are provided.

The calcium carbonate packed tower 30 is filled with granular calcium carbonate, and has a pH-adjusted fluorine-containing wastewater (hereinafter referred to as raw water) or a fluorine residual treatment water (a treatment in which fluorine remains). When water) comes into contact with calcium carbonate, a substitution reaction of fluorine and carbonic acid occurs, and fluorine is removed from raw water or fluorine residual wastewater. The substitution reaction of fluorine and carbonic acid proceeds from the surface of granular calcium carbonate and transitions to the inside. For this reason, calcium carbonate is converted into calcium fluoride as time passes through the calcium carbonate packed tower 30. This reaction is represented by a chemical formula as shown in chemical formula 1.

  In addition, in the inside of the calcium carbonate packed tower 30, together with the substitution reaction of fluorine and carbonic acid, dissolution of calcium carbonate by the acid component in the raw water and precipitation of calcium fluoride due to the reaction of the dissolved calcium carbonate and fluorine occur. it is conceivable that.

Further, according to the above reaction formula, since hydrogen fluoride (HF) is converted into calcium fluoride (CaF ₂ ) and water (H ₂ O), the pH of the treated water rises, but the treatment performance decreases. In other words, the pH of the treated water decreases as the conversion efficiency decreases as the reaction between calcium carbonate and fluorine proceeds into the granular calcium carbonate. For this reason, when the reaction between calcium carbonate and fluorine ends, the pH of the treated water (fluorine residual treated water) becomes substantially the same as the pH of the raw water.

  Note that the higher the concentration of fluorine, the more the fluorine can penetrate into the calcium carbonate grains. That is, as the fluorine concentration in the raw water is higher, the unused calcium carbonate can be reduced, and calcium fluoride with higher purity can be obtained.

  Each of the first calcium carbonate packed tower 30a to the third calcium carbonate packed tower 30c filled with calcium carbonate as described above is provided with a supply port, a discharge port, and a circulation path port. The supply port is provided on the lower side of the calcium carbonate packed tower 30 and is used to supply raw water, fluorine residual treated water, circulating liquid, and the like to the calcium carbonate packed tower 30. The discharge port is provided on the upper side of the calcium carbonate packed tower 30, and is treated water from which fluorine has been removed from raw water, or treated water in which fluorine remains due to a reduction in treatment performance (hereinafter referred to as "fluorine residual treated water"). Used to discharge The circulation path port is provided on the upper side of the calcium carbonate packed tower 30 and below the discharge port. A circulation path 32 (32a to 32c) connected to the above-described supply port is connected to the circulation path port, and a calcium carbonate packed tower 30 is provided by a circulation pump 34 (34a to 34c) provided in the circulation path 32. The internal liquid is sent from the circulation path port to the supply port.

  By the circulating flow (circulating liquid) sent to the supply port through the circulation path 32, the calcium carbonate particles filled in the calcium carbonate packed tower 30 float and an expanded bed is formed. Formation of the expanded bed can prevent adhesion between granular calcium carbonates and accumulation of carbon dioxide gas discharged from calcium carbonate in the calcium carbonate packed tower 30 and can suppress reaction stoppage and the like. .

  The PH adjustment tank 12 plays a role of adjusting the pH of the raw water supplied to the calcium carbonate packed tower 30 described above. A fluorine-containing wastewater storage tank 10 into which fluorine-containing wastewater before PH adjustment (hereinafter referred to as wastewater) flows is connected to the PH adjustment tank 12 to adjust the pH of the wastewater supplied from the fluorine-containing wastewater storage tank 10. PH adjusting means 14 is provided.

  The PH adjusting means 14 in this embodiment includes a PH meter 26, a hydrochloric acid storage tank 16, a sodium hydroxide storage tank 20, a hydrochloric acid supply pump 18, a sodium hydroxide supply pump 22, and a PH adjustment control device 24. The PH meter 26 is a PH measurement unit that measures the PH in the PH adjustment tank 12. The hydrochloric acid storage tank 16 is a storage tank for storing hydrochloric acid as a solution for shifting the pH of raw water stored in the PH adjustment tank 12 to the acidic side, and the hydrochloric acid supply pump 18 is a hydrochloric acid storage tank. 16 is a pump for supplying hydrochloric acid stored in 16 to the PH adjustment tank 12. The sodium hydroxide storage tank 20 is a storage tank that stores sodium hydroxide as a solution for shifting the pH of the raw water stored in the PH adjustment tank 12 to the alkaline side. The sodium hydroxide supply pump 22 Is a pump for supplying sodium hydroxide stored in the sodium hydroxide storage tank 20 to the PH adjustment tank 12. Furthermore, the PH adjustment control device 24 determines to shift the pH of the raw water stored in the PH adjustment tank 12 to either the acidic side or the alkaline side based on the PH value measured by the PH meter 26, Control for operating the hydrochloric acid supply pump 18 or the sodium hydroxide supply pump 22 is performed. The PH adjusting tank 12 may be provided with a stirring means 28 in order to stabilize the PH in the PH adjusting tank 12.

In this embodiment, adjustment is performed so that the PH value in the PH adjustment tank 12 is about 2 to 4. In the fluorine treatment using the calcium carbonate packed tower 30, the hydrofluoric acid is diluted with water so that the fluorine concentration of the hydrofluoric acid (hydrofluoric acid: HF _aq ) as the reagent becomes the same as the fluorine concentration of the waste water. It is known that the fluorine concentration of the treated water can be sufficiently reduced by adjusting the pH of the waste water so as to be the same as that of hydrofluoric acid. In this case, it is also known that the quality of the treated water can be made almost neutral.

  Here, when the pH of the wastewater or raw water is higher than the above range, if the wastewater or raw water is supplied to the calcium carbonate packed tower 30, the quality of the treated water becomes weakly alkaline, and the pH rises at a higher PH. The treatment ends with insufficient fluorine removal. On the other hand, when the pH of the waste water or raw water is lower than the above range, although the fluorine removal is sufficiently performed, the acid component dissolves calcium carbonate and flows out with the treated water without participating in the fluorine removal. Calcium carbonate will increase. Furthermore, an increase in calcium ions in the acidic liquid may cause a coagulation reaction with fluorine in the fluorine-containing wastewater, which may cause a problem that SS (Suspended Solids) increases.

  Further, as shown in FIG. 2, the experiment shows that the fluorine removal rate is good when the pH of the wastewater is 2.5 to 3.5. Here, the drainage A, the drainage B, and the drainage C have different concentrations of alkali component and acid component that also contain fluorine concentration. The fluorine concentration of each waste water is higher than that of the waste water C, and the waste water C is a waste water whose fluorine concentration is about one digit lower than that of the waste water A and B. In addition, as a characteristic of drainage, drainage A is drainage having higher electrical conductivity than drainage B. Further, as can be seen from FIG. 2, although the optimum PH for fluorine removal differs depending on the type (characteristics) of fluorine-containing wastewater, as described above, a high fluorine removal rate at a value of approximately PH 2.5 to 3.5. It can be seen that For this reason, it is considered that good fluorine removal can be expected even when the type of wastewater is increased by providing 0.5 buffers on the acidic side and alkaline side as good PH values. Therefore, in this embodiment, the pH of the raw water is 2-4.

  The PH adjusting tank 12 as described above is connected to the downstream side (discharge side) of the circulation pump 34 in the circulation path 32 provided in each calcium carbonate packed tower 30 via the raw water supply path 38. The raw water supply path 38 includes a base pipe 40 and branch pipes 42 (42 a to 42 c), and branch pipes 42 branched from the base pipe 40 connected to the PH adjustment tank 12 are connected to the circulation paths 32. Each branch pipe 42 is provided with a raw water supply pump 46 (46a to 46c) and a raw water supply valve 44 (44a to 44c), respectively, and opens and closes the raw water supply valve 44 and operates the raw water supply pump 46 to the calcium carbonate packed tower 30. The presence or absence of supply of raw water is controlled. In the present embodiment, the raw water supply pump 46 (46a to 46c) is individually provided corresponding to the calcium carbonate packed tower 30 (30a to 30c), but the branch pipe 42 (42a to 42c) of the raw water supply path 38 is provided. In the foreground, the base pipe 40 is provided with a raw water supply pump 46 (representatively), and the raw water supply valve 44 (44a to 44c) is opened and closed to control whether raw water is supplied to the calcium carbonate packed tower 30 (30a to 30c). You can also

  A discharge passage 48 (48a to 48c) is connected to the discharge port of the calcium carbonate packed tower 30, and the discharge passage 48 is connected to the treated water discharge passage 50 (50a to 50c) and the fluorine residual treated water discharge passage 56 (56a to 56c). It is branched. The treated water discharge path 50 is a path for discharging treated water in which the removal of fluorine contained in the raw water is stably performed in the calcium carbonate packed tower 30, and the fluorine residual treated water discharge path 56 is deteriorated in treatment performance. This is a path for discharging the fluorine residual treated water in which fluorine remains in the treated water. The treated water discharge path 50 is connected to the base pipe discharge path 58, and the fluorine residual treated water discharge path 56 is upstream of the circulation pump 34 (suction) in the circulation path 32 provided in the other calcium carbonate packed tower 30. The residual fluorine treated water can be sent to the calcium carbonate packed tower 30 by using the suction pressure of the circulation pump 34. Specifically, the fluorine residual treated water discharge path 56a branched from the discharge path 48a connected to the discharge port of the first calcium carbonate packed tower 30a is connected to the circulation path 32b of the second calcium carbonate packed tower 30b. The fluorine residual treated water discharge path 56b branched from the discharge path 48b connected to the discharge port of the second calcium carbonate packed tower 30b is connected to the circulation path 32c of the third calcium carbonate packed tower 30c. The fluorine residual treated water discharge path 56c branched from the discharge path 48c connected to the discharge port of the third calcium carbonate packed tower 30c is connected to the circulation path 32a of the first calcium carbonate packed tower 30a. In the present embodiment, since the number of the calcium carbonate packed towers 30 is three, such a connection form is adopted, but the connection form of the fluorine residual treated water discharge path differs depending on the number of calcium carbonate packed towers. That is, when the number of the calcium carbonate packed towers 30 increases, it is sequentially connected to the circulation path of the next stage calcium carbonate packed tower 30, and the fluorine residual treated water discharge path of the final stage calcium carbonate packed tower is the first stage (first stage). 1) It should be connected to the circulation path of the calcium carbonate packed tower.

  Each discharge passage 48 is provided with a PH meter 36 (36a to 36c) as a PH measuring means for measuring the pH of treated water or fluorine residual treated water. The treated water discharge passage 50 and the fluorine residual drainage discharge passage 56 are respectively provided with treated water discharge valves 52 (52a to 52c) and fluorine residual treated water discharge valves 54 (54a to 54c).

  The raw water supply valve 44, the treated water discharge valve 52, the fluorine residual treated water discharge valve 54, and the PH meters 36 and 26 described above are connected to the valve control means 60. The valve control means 60 opens and closes the raw water supply valve 44, the treated water discharge valve 52, and the fluorine residual treated water discharge valve 54 based on the PH values measured by the PH meters 36 and 26, respectively, Controls the production of high purity calcium fluoride.

The fluorine-containing wastewater treatment method using the treatment apparatus 100 having the above-described configuration is performed along the following steps (see FIG. 3).
The fluorine-containing wastewater treatment method according to this embodiment includes a PH adjustment step, a primary single tower treatment step, a multistage tower treatment step, and a secondary single tower treatment step.

  The PH adjustment step refers to a step of supplying raw water stored in the storage tank 10 to the PH adjustment tank 12, adjusting the pH of the waste water via the PH adjustment means 14, and generating raw water. As PH of raw | natural water, it is good to set to 2-4 (S10).

  The primary single tower treatment step refers to a step of performing fluorine removal treatment from raw water only by the first calcium carbonate packed tower 30a. Specifically, the raw water supply valve 44a is controlled to be “open” by the valve control means 60, and the raw water supply pump 46a is operated, whereby the supply port is connected to the first calcium carbonate packed tower 30a via the circulation path 32a. And raw water are supplied (S20).

  The raw water passed through the first calcium carbonate packed tower 30a has its fluorine removed by the calcium carbonate filled therein, and is discharged as treated water from the discharge port to the drainage channel 48a. The treated water discharged to the discharge path 48a is measured for PH by the PH meter 36a and compared with the pH of the raw water. The pH of the treated water at the initial stage of water flow is high, and when the raw water subjected to the PH adjustment as described above is passed, it is almost neutral (near PH7). When the measured value by the PH meter 36a shows such a value, the valve control means 60 determines that the treatment is stable, and opens the treated water discharge valve 52a provided in the treated water discharge passage 50a. The treated water passes through the base pipe discharge path 58 and is sent to the advanced treatment (S30: No).

  The multistage tower treatment step refers to a step of performing a fluorine removal treatment from raw water using the first calcium carbonate packed tower 30a and the second calcium carbonate packed tower 30b. If the primary single tower treatment step described above is continued, the treatment performance of the first calcium carbonate packed tower will be lowered. When the treatment performance of the first calcium carbonate packed tower 30a is lowered, the pH of the treated water measured by the PH meter 36a provided in the discharge path 48a is inclined to the value on the raw water side. In the case of this embodiment, since the pH of the raw water is adjusted to an acidity of 2 to 4, the pH of the treated water that has been almost neutral during the stable treatment changes in a decreasing direction. When the valve control means 60 detects this decrease in PH, the valve control means 60 determines that the processing performance of the first calcium carbonate packed tower 30a has deteriorated. The valve control means 60 that has determined that the treatment performance of the first calcium carbonate packed tower 30a has deteriorated is treated water from the first calcium carbonate packed tower 30a (in this case, the concentration of fluorine remaining in the treated water is high). , The residual fluorine treated water discharge valve 54a is set to “open”, and the treated water discharge valve 52a is controlled to be “closed”.

  In the case of this embodiment, valve control is performed in a range from when the PH value of the treated water is lowered by about 1 from the initial stage of water flow to when the PH value of the treated water is lowered to about 1 higher than the pH of the raw water. The means 60 is activated.

  Experiments have shown that when the pH of the treated water is decreased by 1 compared to the stable treatment at the initial stage of water flow, the fluorine concentration in the treated water is clearly higher than the fluorine concentration during the stable treatment. The proportion of the concentration that rises depends on the quality of the wastewater, but when the fluorine concentration of the raw water is low, the fluorine concentration of the treated water rises to about 1.5 times, and the treated water (the treated water in this embodiment) ) Is insufficient for use. On the other hand, when the fluorine concentration of raw water is high, the fluorine concentration of the treated water at the time of the stable treatment is low, and even if the pH of the treated water is decreased by 1, the quality of the treated water is sufficient to be used for the feed water for advanced treatment. Become.

  On the other hand, when the pH of the treated water is lowered to a value one higher than that of the raw water, the treatment performance is lowered to 90% or less of the fluorine removal rate. In this case, when the fluorine concentration of the raw water is high, high concentration fluorine remains in the treated water, which is inappropriate for use in the feed water for advanced treatment. Even when the fluorine concentration of raw water is low, the permeability of the raw water with respect to calcium carbonate is low, so that the quality of the treated water is temporarily insufficient for use in the feed water for advanced treatment. However, when this is mixed with the treated water during the stable treatment and diluted, the influence on the advanced treatment in the subsequent stage can be reduced. For this reason, it can be said that the median value of the above range (the intermediate value between the raw water PH and the treated water PH) is an appropriate set value as the PH threshold range for operating the valve control means 60. The above setting range.

In addition, since the carbonic acid density | concentration of the treated water at this time has fallen to about 1/2 of the time of a stable treatment, melt | dissolution of a calcium carbonate can be reduced even if it connects a treated water to the next tower.
By performing valve control as described above, in the multistage treatment process, the fluorine residual treated water discharged from the first calcium carbonate packed tower 30a is supplied to the second calcium carbonate packed tower 30b. . For this reason, in the multistage treatment process, final fluorine removal is performed in the second calcium carbonate packed tower 30b, and high purity calcium fluoride is effectively generated in the first calcium carbonate packed tower 30a. (S30: Yes, S40, S50).

  The fluorine residual treated water passed through the second calcium carbonate packed tower 30b is discharged to the discharge path 48b as treated water. The treated water discharged to the discharge passage 48b is measured for PH value by the PH meter 36b, and the treated water discharge valve 52b is "opened" by the valve control means 60 during stable treatment, and discharged to the base pipe discharge passage 58. (S50).

  The secondary single tower treatment step refers to a step of performing a fluorine removal treatment from raw water using only a single calcium carbonate packed tower performed after the multistage tower treatment step. Specifically, when the PH value measured by the PH meter 36a is approximately equal to the pH of the raw water, the supply of the raw water to the first calcium carbonate packed tower 30a is stopped and the second calcium carbonate charged The opening and closing of the valve is switched so as to supply the raw water directly to the tower 30b (S60).

  When the measured value of the PH meter 36a becomes equal to that of the raw water, the valve control means 60 determines that the production of high purity calcium fluoride in the first calcium carbonate packed tower 30a has been completed. In this case, the valve control means 60 controls to switch the raw water supply valve 44a and the fluorine residual treated water discharge valve 54a to “closed” and switch the raw water supply valve 44b to “open” (S70). Then, by operating the raw water supply pump 46b, the raw water supplied from the PH adjustment tank 12 is directly supplied to the second calcium carbonate packed tower 30b (S80).

  After the start of water flow to the second calcium carbonate packed tower 30b, when the measured value by the PH meter 36b provided in the discharge channel 48b connected to the second calcium carbonate packed tower 30b is lower than the initial water flow, The valve control means 60 is activated. Specifically, control is performed so that the treated water discharge valve 52b is switched to “closed” and the fluorine residual treated water discharge valve 54b and the treated water discharge valve 52c are switched to “open”. By such valve switching, the fluorine residual treated water discharged from the second calcium carbonate packed tower 30b is transferred to the third calcium carbonate packed tower 30c as another calcium carbonate packed tower. Water is passed (multistage tower treatment process).

  After the multistage tower processing step by the second calcium carbonate packed tower 30b and the third calcium carbonate packed tower 30c, the valves are switched based on the measured value of the PH meter 36b, and the third calcium carbonate packed tower 30c A secondary single column processing step is performed. Thereafter, the process shifts to a multistage tower treatment step using the third calcium carbonate packed tower 30c and the first calcium carbonate packed tower 30a, and the secondary single tower treatment step and the multistage between the next stage calcium carbonate packed tower. By removing the tower treatment process, the raw water is subjected to fluorine removal treatment.

  Here, when the secondary single tower processing step is performed by the second calcium carbonate packed tower 30b, or the multistage tower processing step is performed by the second calcium carbonate packed tower 30b and the third calcium carbonate packed tower 30c. The first calcium carbonate packed tower 30a, in which water flow is stopped when it is performed, pulls out the produced high-purity calcium fluoride and charges new calcium carbonate particles. It is because it is not necessary to stop a processing apparatus by carrying out extraction of calcium fluoride and filling with calcium carbonate in such a procedure, and the raw water treatment is not delayed (S90).

  When the above treatment method is carried out using the treatment apparatus 100 as described above, water is passed until the fluorine concentration in the liquid in the calcium carbonate packed tower 30 (30a to 30c) is substantially the same as the fluorine-containing waste water. Therefore, the fluorine penetrates to the deep part of the granular calcium carbonate to cause the reaction. For this reason, high purity calcium fluoride can be stably recovered.

Moreover, the quality of the treated water discharged out of the system can be stabilized by adjusting the pH of the raw water.
Furthermore, since the processing apparatus 100 is operated by sequentially switching between the single tower treatment process (primary and secondary) and the multistage tower treatment process based on the value of PH, it is included in the fluorine residual treated water flowing into the subsequent stage. The concentration of an acid component such as carbonic acid can be lowered, the amount of calcium carbonate flowing out from the calcium carbonate packed tower 30 without contributing to fluorine removal can be suppressed, and wasteful outflow of calcium carbonate can be prevented.

Next, a second embodiment of the method and apparatus for treating fluorine-containing wastewater according to the present invention will be described with reference to FIG.
Most of the configuration of the processing apparatus according to this embodiment is the same as that of the processing apparatus 100 according to the first embodiment shown in FIG. Therefore, portions having the same configuration are denoted by the same reference numerals in the drawings, and detailed description thereof is omitted. In addition, in the form shown in FIG. 4, in order to simplify description, two calcium carbonate packed towers are used.

  The difference from the treatment apparatus 100 according to the first embodiment is that the first calcium carbonate packed tower 30 a and the second calcium carbonate packed tower 30 b are directly connected by the fluorine residual treated water discharge path 56. Instead, a fluorine residual treated water storage tank 55 is provided.

  By providing the fluorine residual treated water storage tank 55, the first calcium carbonate packed tower 30a and the second calcium carbonate packed tower 30b are separated from each other. Specifically, the fluorine residual treated water stored in the fluorine residual treated water storage tank 55 is connected to the fluorine residual treated water storage tank 55 and the circulation path 32 of the calcium carbonate packed tower 30. (59a, 59b) and the raw water / fluorine residual treated water supply passage 43 (43a, 43b) and the fluorine residual treated water supply valve 57 (57a, 57b) provided in the fluorine residual treated water supply passage 59 and the raw water / fluorine It is possible to feed water to an arbitrary calcium carbonate packed tower 30 through the raw water / fluorine residual treated water supply pump 47 (47a, 47b) provided in the residual treated water supply passage 43.

  Here, in the treatment apparatus 100a of the present embodiment, since the fluorine residual treated water is supplied through the raw water / fluorine residual treated water supply pump 47, the connection of the raw water / fluorine residual treated water supply path 43 to the circulation path 32 is performed. Can be the downstream side (discharge side) of the circulation pump 34. In the calcium carbonate packed tower 30, the calcium carbonate in the packed tower is partially dissolved by treating fluorine. For this reason, calcium ions are contained in the circulating liquid (water fed through the circulation path) for forming the expanded bed. When raw water containing fluorine or treated water containing fluorine is mixed with such a circulating liquid, SS is generated by an agglomeration reaction.

  However, the occurrence of SS can be reduced by bringing raw water or fluorine residual treated water into contact with calcium carbonate immediately after mixing with circulating fluid. In order to practice this, it is important to connect the supply destination of raw water or fluorine residual treated water as close to the calcium carbonate packed tower 30 as possible.

  In the treatment apparatus 100 according to the first embodiment, the fluorine residual treated water discharge path 56 is connected to the suction side of the circulation pump 32 and the suction pressure of the circulation pump 32 is used to supply the fluorine residual treated water to the calcium carbonate packed tower 30. Was to supply. In contrast, in the treatment apparatus 100a according to the present embodiment, the residual fluorine treated water is supplied from the residual fluorine treated water storage tank 55 to the calcium carbonate packed tower 30 via the raw water / residual fluorine treated water supply pump 47. As a result, the raw water / fluorine residual treated water supply path 43 can be connected to the discharge side of the circulation pump 34. By adopting such a configuration, the above measures can be practiced, and the occurrence of SS can be reduced.

The flow of treatment of fluorine-containing wastewater by the treatment apparatus 100a according to this embodiment having such a configuration is almost the same as the method for treating fluorine-containing wastewater according to the first embodiment described above.
The difference is that the destination of fluorine residual treated water when the measured values of the PH meters 36a, 36b are reduced is the fluorine residual treated water storage tank 55, and the raw water / fluorine residual treated water is taken from the fluorine residual treated water storage tank 55. This is a point in which the fluorine residual treated water is supplied to the next stage calcium carbonate packed tower 30 through the supply path 43.

  Specifically, when the measured value of the PH meter 36a provided in the discharge path 48a connected to the discharge port of the first calcium carbonate packed tower 30a decreases, the valve control means 60 sets the treated water discharge valve 52 to “ “Closed”, the fluorine residual treated water discharge valve 54a and the fluorine residual treated water supply valve 57b are switched to “open”. Then, by operating the raw water / fluorine residual treated water supply pump 47b provided in the raw water / fluorine residual treated water supply path 43b, the fluorine residual treated water is supplied to the second calcium carbonate packed tower 30b. (Formally, multistage tower processing step).

  At the time of shifting to the single tower treatment step (secondary single tower treatment step) by the second calcium carbonate packed tower 30b, the valve control means 60 uses the raw water supply valve 44a, the fluorine-containing treated water discharge valve 54a, and the fluorine-containing treatment. The treated water supply valve 57b is controlled to be “closed” and the raw water supply valve 44b is controlled to be “open”. In this state, the raw water / fluorine residual treated water supply pump 47a is stopped and the raw water / fluorine residual treated water supply pump 47b is operated, whereby the raw water is supplied to the second calcium carbonate packed tower 30b.

  According to the fluorine-containing wastewater treatment method and apparatus having such characteristics, as described above, it is possible to reduce the occurrence of SS due to the aggregation reaction. In addition, about another effect, it is the same as that of the processing method and apparatus of the fluorine-containing waste_water | drain which concern on 1st Embodiment mentioned above.

  In addition, in both the processing apparatuses 100 and 100a which concern on the said embodiment, although the fluorine-containing waste water storage tank 10 and the PH adjustment tank 12 are provided as another tank, it is good also considering these as one tank. Even in this case, there is no trouble in carrying out the method for treating fluorine-containing wastewater according to the present invention, and the installation space for the treatment apparatuses 100 and 100a can be reduced by combining the tanks into one. .

  Moreover, in the said embodiment, it showed that PH adjustment of fluorine-containing wastewater was performed with the PH adjustment tank 12. FIG. However, the pH may be adjusted by directly injecting hydrochloric acid, sodium hydroxide, or the like into the water supply line (raw water supply path 38). It is because the space which arrange | positions PH adjustment tank 12 can be reduced by setting it as such a structure.

  Furthermore, in the above embodiment, it has been shown that the pH adjustment of fluorine-containing wastewater is performed only in the PH adjustment tank 12. However, the PH may be adjusted as follows. That is, in a method of performing stepwise PH adjustment in which the primary pH adjustment is performed in the fluorine-containing drainage storage tank 10 that also serves as the PH adjustment tank 12, and the secondary PH adjustment is performed in the water supply line to the calcium carbonate packed tower 30. is there. When such a method is adopted, the arrangement space of the PH adjustment tank 12 and the fluorine-containing drainage storage tank 10 can be reduced, and the PH adjustment can be performed with high accuracy.

  Moreover, the method for treating fluorine-containing wastewater according to the present invention can be implemented by providing at least two calcium carbonate packed towers 30 as shown in FIG. In this case, while one calcium carbonate packed tower (for example, the second calcium carbonate packed tower 30b) is performing the single tower treatment step (secondary), the other calcium carbonate packed tower (for example, the first carbonate The high-purity calcium fluoride may be drawn from the calcium packed tower 30a) and filled with new calcium carbonate. By repeating the extraction of calcium fluoride and the filling of calcium carbonate at such timing, the space required for the processing apparatus can be minimized.

  If the time required for drawing calcium fluoride from the calcium carbonate packed tower 30 and filling the calcium carbonate is long, and it does not end within the time for performing one secondary single tower treatment step, When the number of the calcium carbonate packed towers 30 is determined based on the time required for drawing out calcium chloride and filling the calcium carbonate, or the number of times the multistage tower processing step and the secondary single tower processing step are repeated. good. This is because, by determining the number of calcium carbonate packed towers 30 in this way, it is possible to continuously carry out the treatment of the fluorine-containing waste water.

  Further, when the number of columns of the calcium carbonate packed tower 30 is more than twice the number of towers required for the cycle for treating fluorine-containing wastewater, it is possible to carry out two fluorine removal cycles in parallel. Become. Specifically, in the case where the fluorine-containing wastewater is treated in the two towers filled with calcium carbonate 30, there are four towers filled with calcium carbonate (the first calcium carbonate packed tower to the fourth calcium carbonate packed tower). It is. In this case, the primary single tower treatment step is the first calcium carbonate packed tower and the third calcium carbonate packed tower, the multistage tower treatment step is the combination of the first calcium carbonate packed tower and the second calcium carbonate packed tower and the first 3 combined with a calcium carbonate packed tower and a fourth calcium carbonate packed tower, and a secondary single tower treatment step is performed in parallel as two cycles, such as a second calcium carbonate packed tower and a fourth calcium carbonate packed tower. Can be implemented. By performing such treatment, the treatment efficiency of fluorine-containing wastewater can be improved.

It is a figure which shows the structure of the processing apparatus of the fluorine-containing waste_water | drain which concerns on 1st Embodiment. It is a graph which shows the relationship between PH of fluorine-containing wastewater, and the fluorine removal rate when this is passed through a calcium carbonate packed tower. It is a flowchart which shows the flow of the processing method of the fluorine-containing waste_water | drain which concerns on invention. It is a figure which shows the structure of the processing apparatus of the fluorine-containing waste_water | drain which concerns on 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ......... Fluorine containing waste water storage tank, 12 ......... PH adjustment tank, 14 ......... PH adjustment means, 16 ......... Hydrochloric acid storage tank, 18 ......... Hydrochloric acid supply pump, 20 ......... Sodium hydroxide storage Tank, 22 ......... Sodium hydroxide supply pump, 24 ......... PH adjustment controller, 26 ......... PH meter, 28 ......... Stirring means, 30 (30a-30c) ......... Calcium carbonate packed tower (No. 1) 1 (calcium carbonate packed tower to third calcium carbonate packed tower), 32 (32a to 32c) ......... circulation path, 34 (34a to 34c) ......... circulation pump, 36 (36a to 36c) ......... PH Total: 38 ... Raw water supply path, 40 ... Base pipe, 42 (42a-42c) ... Branch pipe, 44 (44a-44c) ... Raw water supply valve, 46 (46a-46c) ... ... Raw water supply pump, 48 (48a-48 ) ... Discharge passage, 50 (50a-50c) ......... Treatment water discharge passage, 52 (52a-52c) ......... Treatment water discharge valve, 54 (54a-54c) ......... Fluorine residual treated water discharge valve 56 (56a to 56c) ... fluorine residual treated water discharge path, 58 ... base pipe discharge path, 60 ... valve control means, 100 ... fluorine treatment wastewater treatment equipment (treatment equipment).

Claims (6)

A fluorine-containing wastewater treatment method using a fluorine-containing wastewater treatment apparatus having a plurality of calcium carbonate packed towers,
PH adjustment step for adjusting raw material wastewater by adjusting PH of fluorine-containing wastewater;
A primary single tower treatment step of passing the raw water adjusted for pH through a first calcium carbonate packed tower, removing the fluorine of the raw water and discharging it as treated water;
After the treated water PH discharged from the first calcium carbonate packed tower is lower than the treated water PH in the initial stage of water flow to become fluorine residual treated water, the treatment in the first calcium carbonate packed tower is performed. Switching to high-purity calcium fluoride production, passing the fluorine residual treated water through a second calcium carbonate packed tower and removing fluorine from the fluorine residual treated water to produce treated water,
After the pH of the fluorine residual treated water discharged from the first calcium carbonate packed tower decreases and becomes close to or equal to the pH of the raw water, the water flow to the first calcium carbonate packed tower is stopped. And having a secondary single tower treatment step of generating treated water by passing the raw water through the second calcium carbonate packed tower,
After the secondary single tower treatment step, the multistage treatment step using another calcium carbonate packed tower and the secondary single tower treatment step are sequentially repeated, and from the calcium carbonate packed tower in which water flow is stopped. A method for treating fluorine-containing wastewater, wherein calcium fluoride is pulled out and new calcium carbonate is filled in a calcium carbonate packed tower from which calcium fluoride has been pulled out. Withdrawing calcium fluoride and filling with calcium carbonate from the calcium carbonate packed tower begins during the secondary single tower treatment step,
2. The fluorine according to claim 1, wherein the number of towers filled with calcium carbonate used for the treatment of fluorine-containing wastewater is determined based on the number of the multistage treatment steps repeated until the filling of the calcium carbonate is completed. Treatment method of contained wastewater. The calcium carbonate packed tower is two towers,
While the secondary single tower treatment step by the second calcium carbonate packed tower is being performed, drawing out calcium fluoride from the first calcium carbonate packed tower and filling with calcium carbonate,
By performing extraction of calcium fluoride from the second calcium carbonate packed tower and filling of calcium carbonate while the secondary single tower treatment step by the first calcium carbonate packed tower is performed,
The method for treating fluorine-containing wastewater according to claim 1, wherein the secondary single tower treatment step and the multistage tower treatment step are repeated by two calcium carbonate packed towers.   2. The fluorine residual treated water is discharged into a fluorine residual treated water storage tank, and water is actively passed from the fluorine residual treated water storage tank to the second calcium carbonate packed tower. The processing method of the fluorine-containing waste water of any one of Claim 3. A fluorine-containing wastewater treatment apparatus having a plurality of calcium carbonate packed towers,
PH adjusting means for adjusting the pH of raw water to be passed through the calcium carbonate packed tower;
A PH meter that is provided in each of the plurality of calcium carbonate packed towers and measures the PH of treated water discharged from the calcium carbonate packed tower;
A raw water supply valve for defining a calcium carbonate packed tower for supplying the raw water;
A treated water discharge valve for connecting a discharge path for discharging treated water out of the system and a discharge port of the calcium carbonate packed tower;
A fluorine residual treated water discharge valve for supplying residual fluorine treated water discharged from one calcium carbonate packed tower to another calcium carbonate packed tower;
Valve control means for controlling the opening and closing of the raw water supply valve, the treated water discharge valve, and the fluorine residual treated water discharge valve based on the value measured by the PH meter;
A raw water supply pump for feeding the raw water to an optional calcium carbonate packed tower,
When the raw water supply valve to the one calcium carbonate packed tower is opened, the valve control means opens the treated water discharge valve connected to the one calcium carbonate packed tower, and discharges the fluorine residual treated water. The valve is closed, and when the PH value measured by the PH meter connected to the one calcium carbonate packed tower is lowered, the treated water discharge valve is closed, the fluorine residual treated water discharge valve is opened, the other The treated water discharge valve connected to the calcium carbonate packed tower is opened, the residual fluorine treated water discharge valve is closed, and the PH value measured by the PH meter connected to the one calcium carbonate packed tower is adjusted. The raw water supply valve to the one calcium carbonate packed tower is closed when the PH of the raw water is close to or the same as the PH of the raw water, Processor of fluorine-containing waste water and controlling the raw water supply valve to open. A fluorine residual treated water storage tank for storing fluorine residual treated water discharged from the one calcium carbonate packed tower;
A fluorine residual treated water supply valve for supplying the fluorine residual treated water from the fluorine residual treated water storage tank to the other calcium carbonate packed tower;
A pump for feeding the fluorine residual treated water from the fluorine residual treated water storage tank to the other calcium carbonate packed tower;
6. The fluorine-containing wastewater treatment apparatus according to claim 5, wherein the valve control means opens and closes the fluorine residual treated water supply valve in synchronization with the opening and closing timing of the fluorine residual treated water discharge valve.

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