Regulation and control method and regulation and control system for fluorine removal of fluorine-containing underground water

Abstract

The invention belongs to the technical field of fluorine-containing water treatment, and relates to a regulation and control method and a regulation and control system for fluorine removal of fluorine-containing underground water. The regulation and control method comprises the following steps: acquiring the fluorine ion concentration, alkalinity and magnesium ion concentration of actual fluorine-containing underground water; preparing simulated fluorine-containing groundwater and a phosphoric acid solution, and enabling the fluorine concentration of the simulated fluorine-containing groundwater to be the same as the fluorine ion concentration of the actual fluorine-containing groundwater; continuously increasing the alkalinity of the simulated fluorine-containing water until the alkalinity of the simulated fluorine-containing water is the same as the alkalinity of the actual fluorine-containing underground water, and adding an acid agent into the phosphoric acid solution; on the basis that the alkalinity reaches the alkalinity of the actual fluorine-containing underground water, magnesium salt is added into the simulated fluorine-containing water, so that the magnesium ion concentration of the simulated fluorine-containing water is the same as that of the actual fluorine-containing underground water; afterwards, the simulated fluorine-containing water is replaced by the actual fluorine-containing water, so that the fluorine concentration of the effluent can be reduced to 1.0 mg / L or below. The problem that the calcium fluophosphate precipitation reaction fails when the actual fluorine-containing underground water is treated by a calcium fluophosphate precipitation method is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of fluorine-containing water treatment, and specifically relates to a control method and a control system for defluoridating fluorine-containing groundwater. Background Art

[0002] The problem of groundwater fluoride contamination is a recognized public health issue worldwide. According to the requirements of the Drinking Water Quality Standard (GB5749-2022), the fluoride ion concentration in drinking water should be lower than 1.0 mg / L.

[0003] Commonly used defluorination methods include adsorption, ion exchange, electrocoagulation, membrane separation and chemical precipitation. The regeneration cost of adsorbents and ion exchangers is high and their performance deteriorates quickly. The operation of electrocoagulation and membrane separation is complex and costly, which limits their large-scale application. Chemical precipitation is effective in treating high-concentration fluoride-containing water, but the sedimentation tank occupies a large area, the sludge has a high water content, and its application field is limited.

[0004] The calcium fluoride precipitation method can reduce hundreds or thousands of milligrams of fluoride per liter in water to 10-20 mg / L. It is suitable for defluoridation of industrial wastewater, but not for defluoridation of groundwater. In the 1990s, the calcium fluorophosphate precipitation method appeared, which can achieve defluoridation under a higher molar mass ratio of calcium and phosphorus input (several dozen times) and a longer reaction time (72-96h). Subsequently, this method has only been able to treat simulated fluoride-containing water (pure water + NaF), but failed to treat actual fluoride-containing groundwater. Technical personnel in this industry have been unable to find the reason.

[0005] Therefore, a new process is urgently needed to remove fluoride from fluoride-containing groundwater. Summary of the invention

[0006] The purpose of the present invention is to provide a control method for defluoridation of fluoride-containing groundwater, a defluoridation system for implementing the method, and a control system for implementing the method, so as to solve the problem that the calcium fluorophosphate precipitation reaction fails when the calcium fluorophosphate precipitation method is used to treat actual fluoride-containing groundwater.

[0007] The present invention is achieved through the following technical solutions:

[0008] In one aspect, the present invention discloses a method for removing fluorine from fluoride-containing groundwater, comprising the following steps:

[0009] S1. Obtaining the fluoride ion concentration, alkalinity and magnesium ion concentration of the actual fluoride-containing groundwater to be treated;

[0010] S2, preparing simulated fluoride-containing water and phosphoric acid solution; the fluoride concentration of the simulated fluoride-containing water is the same as the fluoride ion concentration of the actual fluoride-containing groundwater;

[0011] The phosphoric acid solution is mixed with simulated fluoride-containing water, and after calcium precipitation reaction treatment, the fluoride concentration of the effluent water is reduced to less than 1.0 mg / L;

[0012] S3, continuously increasing the alkalinity of the simulated fluoridated water until the alkalinity of the simulated fluoridated water is the same as the alkalinity of the actual fluoridated groundwater;

[0013] Add an acid to the phosphoric acid solution, mix the acidified phosphoric acid solution with alkaline simulated fluoride-containing water, control the pH of the mixed solution to 5.0-6.0, and treat it with calcium precipitation reaction to make the fluoride concentration of the effluent water lower than 1.0 mg / L;

[0014] S4. On the basis of the alkalinity reaching the alkalinity of the actual fluoridated groundwater, magnesium salt is continuously added to the simulated fluoridated water according to the concentration characteristics of magnesium ions in the actual fluoridated groundwater, so that the magnesium ion concentration of the simulated fluoridated water is the same as that of the actual fluoridated groundwater;

[0015] The phosphoric acid solution after acid addition is mixed with the simulated fluoride-containing water after magnesium salt addition, and the pH of the mixed solution is controlled at 5.0-6.0. After calcium precipitation reaction treatment, the fluoride concentration of the effluent is less than 1.0 mg / L;

[0016] S5. Replace the simulated fluoride-containing water with the actual fluoride-containing groundwater to be treated. At this time, the fluoride concentration in the effluent can be guaranteed to drop below 1.0 mg / L.

[0017] Furthermore, the calcium source required for the calcium precipitation reaction treatment is provided by the waste shell particles filled in the reactor.

[0018] Further, in S3, the alkalinity of the simulated fluoridated water is increased by adding bicarbonate;

[0019] In S3, the acid agent is hydrochloric acid or sulfuric acid;

[0020] In S4, the magnesium salt is magnesium chloride or magnesium sulfate.

[0021] Furthermore, in S2, after the phosphoric acid solution is mixed with the simulated fluorine-containing water, the molar ratio of phosphate to fluoride ion in the mixed solution is (2.0-6.0):1.

[0022] Furthermore, in S3, after the acidified phosphoric acid solution is mixed with the alkaline simulated fluoride-containing water, the molar ratio of phosphate to fluoride ion in the mixed solution is (2.0-6.0):1.

[0023] Further, in S4, the phosphoric acid solution after acid addition is mixed with the simulated fluorine-containing water after magnesium salt is added, and the molar ratio of phosphate to fluoride ion in the mixed solution is (2.0-6.0):1.

[0024] On the other hand, the present invention also discloses a control system based on the control method for defluoridation of fluoride-containing groundwater, comprising a raw water tank, a dosing tank, a first water inlet pump, a dosing pump, a pipeline mixer, a mixing water storage tank, a second water inlet pump, a fixed bed reactor and a water outlet tank;

[0025] The simulated fluoride-containing water and actual groundwater are stored in the raw water tank during operation;

[0026] The phosphoric acid solution and the phosphoric acid solution with acid added are added into the dosing box;

[0027] The raw water tank is connected to the No. 1 water inlet pump, and the dosing tank is connected to the dosing pump;

[0028] The No. 1 water inlet pump and the dosing pump are both connected to the pipeline mixer, and the pipeline mixer is connected to the mixing water storage tank;

[0029] The outlet of the mixed water storage tank is connected to the fixed bed reactor through the No. 2 water inlet pump; the effluent after the reaction in the fixed bed reactor is connected to the effluent tank through a pipeline;

[0030] The raw water tank is equipped with a No. 1 fluoride ion concentration real-time monitoring meter and an alkalinity meter;

[0031] A No. 1 pH real-time monitoring meter is installed in the mixed water storage tank;

[0032] The outlet pool is equipped with a No. 2 pH real-time monitoring meter and a No. 2 fluoride ion concentration real-time monitoring meter.

[0033] Furthermore, the fixed bed reactor is filled with waste shell particles having a particle size of 0.5-1 mm.

[0034] Furthermore, a water inlet is provided at the bottom of the fixed bed reactor, and a water outlet is provided at the top; the outlet position of the mixing water storage tank is connected to the water inlet of the fixed bed reactor through a No. 2 water inlet pump; the effluent after the reaction in the fixed bed reactor is connected to the water outlet tank through a pipeline through the water outlet;

[0035] A liquid inlet is provided on one side of the raw water tank, and a liquid outlet is provided on the other side;

[0036] The medicine adding box is provided with a medicine inlet on one side and a medicine outlet on the other side;

[0037] A mixed water inlet is arranged on one side of the mixed water storage tank, and a mixed water outlet is arranged on the other side; a drain is arranged on one side of the outlet tank, and a water inlet is arranged on the upper part.

[0038] Furthermore, a water inlet post phase is provided on the fixed bed reactor; a No. 3 water inlet pump is provided between the fixed bed reactor and the water outlet tank;

[0039] When flushing the fixed bed reactor, the effluent collected in the effluent pool is used as flushing water, and the effluent pool is connected to the inlet of the fixed bed reactor through the No. 3 inlet pump.

[0040] Compared with the prior art, the present invention has the following beneficial technical effects:

[0041] The present invention discloses a control method for defluoridation of fluoride-containing groundwater. According to the fluoride ion concentration, alkalinity and magnesium ion concentration in the actual fluoride-containing water, simulated fluoride-containing water is prepared, the start-up period of the defluoridation system is controlled, and the dosage of phosphoric acid and acid agent added corresponding to the actual fluoride-containing groundwater is determined. The method can well cope with the coexistence of high alkalinity and high magnesium ions and fluoride ions in the water, so that after the actual groundwater runs through the system, the fluoride ion concentration of the outlet water is less than 1.0 mg / L. The fluoride-containing water can be either actual fluoride-containing groundwater or low-concentration actual fluoride-containing wastewater. The inlet fluoride concentration ranges from 1 to 20 mg / L, and the application range is wide.

[0042] First, simulated fluoride-containing water is prepared according to the fluoride ion concentration. The fluoride ion concentration of the inlet water is fed back by the fluoride ion real-time monitoring meter, and phosphoric acid solution is prepared. The fluoride-containing water and phosphoric acid enter the pipeline mixer in proportion and are mixed evenly to ensure that the molar ratio of phosphate and fluoride ion in the mixed water tank is (2.0-6.0):1. After the mixed water reacts in the reactor, the fluoride ion concentration of the outlet water can be less than 1.0 mg / L;

[0043] Secondly, simulated fluoride-containing water is prepared according to the fluoride ion concentration and alkalinity, and the alkalinity is continuously increased to make its final alkalinity consistent with the actual groundwater. After the fluoride ion concentration and alkalinity of the inlet water are fed back by the fluoride ion real-time monitoring meter and the alkalinity meter respectively, an acid-added phosphoric acid solution is prepared. The fluoride-containing water and the acid-added phosphoric acid solution enter the pipeline mixer in proportion and are mixed evenly to ensure that the molar ratio of phosphate and fluoride ions in the mixed water storage tank is (2.0-6.0):1, and the pH of the mixed water is between 5.0 and 6.0. After the mixed water reacts in the reactor, the fluoride ion concentration of the outlet water can be less than 1.0 mg / L;

[0044] Then, based on the above-mentioned final alkalinity, fluoride-containing water containing magnesium ions is prepared, and the magnesium ion concentration is continuously increased so that the final magnesium ion concentration is consistent with the actual groundwater. After the fluoride ion concentration and alkalinity of the influent are fed back by the fluoride ion real-time monitoring meter and the alkalinity meter, an acid-added phosphoric acid solution is prepared. The fluoride-containing water and the acid-added phosphoric acid solution enter the pipeline mixer in proportion and are mixed evenly to ensure that the molar ratio of phosphate and fluoride ions in the mixed water storage tank is (2.0-6.0):1, and the pH of the mixed water is between 5.0 and 6.0. After the mixed water reacts in the reactor, the fluoride ion concentration of the effluent can be less than 1.0 mg / L;

[0045] Finally, replace the simulated fluoridated water in the inlet pool with actual fluoridated water, continue to operate under the above conditions, and the fluoride ion concentration in the effluent water will meet the standard.

[0046] The present invention determines the dosage of phosphoric acid and acid agent added corresponding to the actual fluorine-containing groundwater by regulating the start-up period of the defluorination system, which can effectively cope with the coexistence of high alkalinity and high magnesium ions and fluoride ions in the water, and the fluoride ion concentration of the effluent water is less than 1.0 mg / L.

[0047] Furthermore, the present invention increases the alkalinity of the simulated fluoride-containing water by adding bicarbonate, and bicarbonate and hydrogen ions exist in the form of carbonic acid in the mixed water and participate in the dissolution process of calcium in the subsequent reactor, without the need to add an additional decarbonizer.

[0048] Furthermore, the present invention uses waste shells as fillers for the reactor. The shell particles are both a calcium source and a filter material, saving investment and operating costs. The operation process of this technology is: "contact filtration + water washing" cycle operation. Compared with the existing adsorption method for fluorine removal, there is no need for the regeneration process of solid materials, saving investment and operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 A schematic diagram of a control system for defluoridation of fluoride-containing groundwater according to the present invention;

[0050] Among them, 1. Raw water tank; 1-1. No. 1 fluoride ion concentration real-time monitoring meter; 1-2. Alkalinity meter; 2. Dosing box; 3. No. 1 water inlet pump; 4. Dosing pump; 5. Pipeline mixer; 6. Mixing water storage tank; 6-1. No. 1 pH real-time monitoring meter; 7. No. 2 water inlet pump; 8. Fixed bed reactor; 8-1. Water inlet; 8-2. Water outlet; 9. No. 3 water inlet pump; 10. Water outlet tank; 10-1. No. 2 pH real-time monitoring meter; 10-2. No. 2 fluoride ion concentration real-time monitoring meter.

[0051] Figure 2 The scanning electron microscope morphology of the calcium fluorophosphate precipitate generated in the embodiment;

[0052] Figure 3 The figure is a comparison between the calcium fluorophosphate precipitate generated in the example and the standard card. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solution and advantages of the present invention more clear, the following is further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, not all embodiments.

[0054] The components described and shown in the drawings and embodiments of the present invention may be arranged and designed in various configurations. Therefore, the detailed description of the embodiments of the present invention provided in the following drawings is not intended to limit the scope of the claimed invention, but merely represents a selected embodiment of the present invention. Based on the drawings and embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0055] It should be noted that the terms "comprises", "includes" or any other variations are intended to cover non-exclusive inclusion, so that a process, element, method, article or equipment that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to the process, element, method, article or equipment.

[0056] After research, it was finally found that the existing calcium fluorophosphate precipitation method is ineffective in removing fluoride when high alkalinity, high magnesium ions and fluoride ions coexist.

[0057] The main reason is that the magnesium ions and alkalinity in the water hinder the precipitation reaction of calcium fluorophosphate. When there is only fluorine and alkalinity in the water (in the scope of this specification, alkalinity not specifically noted is expressed as HCO3 - (Calculation), when there are no other coexisting substances, the dosage of the precipitant must be increased several times to achieve fluoride removal. When there are only fluoride and magnesium ions in the water and no other coexisting substances, not only does the dosage of the precipitant increase significantly, but the precipitate is quickly "poisoned", and frequent sludge discharge is required to achieve continuous fluoride removal. The alkalinity in fluoride-containing groundwater is usually above 100 mg / L, and in some areas it is even as high as 1120 mg / L. The magnesium ion concentration in fluoride-containing groundwater is usually above 10 mg / L, and in some areas it is as high as 400 mg / L. Their presence seriously hinders the defluoridation precipitation reaction, making the calcium fluorophosphate precipitation defluoridation method ineffective for actual groundwater fluoride removal.

[0058] The present invention discloses a control method for defluoridation of fluoride-containing groundwater, comprising the following process:

[0059] S1. Obtaining the fluoride ion concentration, alkalinity and magnesium ion concentration of the actual fluoride-containing groundwater to be treated;

[0060] S2, preparing simulated fluoride-containing water and phosphoric acid solution; the fluoride concentration of the simulated fluoride-containing water is the same as the fluoride ion concentration of the actual fluoride-containing groundwater;

[0061] The phosphoric acid solution is mixed with simulated fluoride-containing water, and after calcium precipitation reaction treatment, the fluoride concentration of the effluent water is reduced to less than 1.0 mg / L;

[0062] S3, continuously increasing the alkalinity of the simulated fluoridated water by adding bicarbonate until the alkalinity of the simulated fluoridated water is the same as the alkalinity of the actual fluoridated groundwater;

[0063] Add an acid to the phosphoric acid solution, mix the acidified phosphoric acid solution with alkaline simulated fluoride-containing water, control the pH of the mixed solution to 5.0-6.0, and treat it with calcium precipitation reaction to make the fluoride concentration of the effluent water lower than 1.0 mg / L;

[0064] S4. On the basis of the alkalinity reaching the alkalinity of the actual fluoridated groundwater, magnesium salt is continuously added to the simulated fluoridated water according to the concentration characteristics of magnesium ions in the actual fluoridated groundwater, so that the magnesium ion concentration of the simulated fluoridated water is the same as that of the actual fluoridated groundwater;

[0065] The phosphoric acid solution after acid addition is mixed with the simulated fluoride-containing water after magnesium salt addition, and the pH of the mixed solution is controlled at 5.0-6.0. After calcium precipitation reaction treatment, the fluoride concentration of the effluent is less than 1.0 mg / L;

[0066] S5. Replace the simulated fluoride-containing water with the actual fluoride-containing groundwater to be treated. At this time, the fluoride concentration in the effluent can be guaranteed to drop below 1.0 mg / L.

[0067] In S3, the acid agent is hydrochloric acid or sulfuric acid; in S4, the magnesium salt is magnesium chloride or magnesium sulfate.

[0068] In S2-S4, the molar ratio of phosphate to fluoride ion in the mixed solution is (2.0-6.0): 1. This can be obtained by calculation after obtaining the fluoride ion concentration.

[0069] The features and performances of the present invention are further described in detail below in conjunction with specific verification examples.

[0070] The fluorine concentration in groundwater in a certain area is 3.25 mg / L, the alkalinity is 615 mg / L, and the magnesium ion concentration is 25.5 mg / L. Detailed indicators are shown in Table 1. Fluoride removal is performed using the control method and system described in the present invention.

[0071] Use tap water to prepare simulated fluoride-containing water with a fluoride concentration of 3.25 mg / L. Set the ratio of inlet water to drug flow rate to 100:1. Prepare phosphoric acid solution so that after the drug and inlet water are mixed, the molar ratio of phosphorus to fluorine is 4.0:1. Under the above conditions, run continuously until the fluoride concentration of the outlet water is less than 1.0 mg / L.

[0072] Sodium bicarbonate was used to increase the alkalinity of the simulated fluoride-containing water to 600 mg / L, the ratio of the inlet water to the inlet drug flow was set to 100:1, and the phosphoric acid solution was prepared so that after the inlet drug and the inlet water were mixed, the molar ratio of phosphorus to fluorine was 4.0:1. At the same time, hydrochloric acid was added to the prepared phosphoric acid solution so that the pH after mixing with the simulated fluoride-containing water was between 5.0 and 6.0. The process was run under the above conditions until the fluoride concentration of the effluent was less than 1.0 mg / L.

[0073] The magnesium ion concentration in the simulated fluoride-containing water was increased to 25 mg / L by using magnesium salt. The ratio of the inlet water to the inlet drug flow rate was set to 100:1, and the phosphoric acid solution was prepared so that after the inlet drug and the inlet water were mixed, the molar ratio of phosphorus to fluorine was 4.0:1. At the same time, hydrochloric acid was added to the prepared phosphoric acid solution so that the pH after mixing with the simulated fluoride-containing water was between 5.0 and 6.0. The operation was carried out under the above conditions until the fluoride concentration of the effluent was stably lower than 1.0 mg / L.

[0074] After running under the above conditions until the fluoride concentration in the effluent is stably lower than 1.0 mg / L, the actual groundwater in the area is used as raw water, and the drug injection conditions are consistent with those of the simulated fluoride-containing water. At this time, the fluoride ion concentration in the effluent can meet the standard.

[0075] Using the above control method, the fluoride concentration in the effluent can be stabilized below 1.0 mg / L for a long time.

[0076] Through regulation, the parameter relationship between the phosphoric acid and acid agent in the final dosing box and the fluoride ion concentration, alkalinity and magnesium ion concentration of the actual fluoride-containing groundwater is shown in Table 2.

[0077] Table 1: Groundwater quality data in a certain area

[0078] Index (mg / L) Actual groundwater <![CDATA[K + ]]> 17.1±0.5 <![CDATA[Na + ]]> 635.2±0.5 <![CDATA[Ca 2+ ]]> 20.6±0.5 <![CDATA[Mg 2+ ]]> 25.2±0.7 <![CDATA[F - ]]> 3.2±0.05 <![CDATA[Cl - ]]> 330.5±2 Alkalinity 609.2±7.5 <![CDATA[SO4 2- ]]> 365.8±2 pH 8.23±0.5 TDS 1357±15

[0079] Table 2: Parameter relationship between phosphoric acid and acid in the dosing box and the fluoride ion concentration, alkalinity and magnesium ion concentration of actual fluoride-containing groundwater

[0080]

[0081] The products generated by the fixed bed reactor were scanned by electron microscope, and the following results were obtained: Figure 2 The SEM image shown in the figure was tested by XRD and the following results were obtained: Figure 3 The comparison chart shown, Figure 2 and Figure 3 All of these can indicate that the reaction product of the present invention is a calcium fluorophosphate precipitate.

[0082] like Figure 1 As shown, the present invention also designs a control system, which mainly includes a raw water tank 1, a dosing tank 2, a No. 1 water inlet pump 3, a dosing pump 4, a pipeline mixer 5, a mixed water storage tank 6, a No. 2 water inlet pump 7, a fixed bed reactor 8, a No. 3 water inlet pump 9, and a water outlet tank 10;

[0083] The simulated fluoride-containing water and actual groundwater are added into the raw water tank 1 ; the phosphoric acid solution and the phosphoric acid solution with acid added are added into the dosing tank 2 .

[0084] Specifically, the raw water tank 1 and the dosing tank 2 are respectively connected to the No. 1 water inlet pump 3 and the dosing pump 4 through pipelines, and valves are provided on the pipelines; the No. 1 water inlet pump 3 and the dosing pump 4 are connected to the pipeline mixer 5 through pipelines, and the pipeline mixer 5 is connected to the mixing water storage tank 6 through pipelines; the outlet position of the mixing water storage tank 6 is connected to the fixed bed reactor 8 through a pipeline and the No. 2 water inlet pump 7, and a valve is provided on the pipeline; the effluent after the reaction is connected to the effluent tank 10 through a pipeline.

[0085] More preferably, when flushing the reactor, the effluent collected in the effluent pool 10 is used as flushing water, and the effluent pool 10 is connected to the inlet of the fixed bed reactor 8 through the No. 3 inlet pump 9 .

[0086] It is necessary to test the raw water tank 1, the mixed water storage tank 6 and the outlet tank 10, as follows:

[0087] The raw water tank 1 is provided with a No. 1 fluoride ion concentration real-time monitoring meter 1-1 and an alkalinity meter 1-2; the No. 1 fluoride ion concentration real-time monitoring meter 1-1 is used to monitor the fluoride concentration of the simulated fluoride-containing water, and the alkalinity meter 1-2 is used to monitor the alkalinity of the simulated fluoride-containing water;

[0088] A pH real-time monitoring meter 6-1 is provided in the mixing water storage tank 6 for monitoring the pH of the mixing water storage tank 6;

[0089] The outlet pool 10 is provided with a No. 2 pH real-time monitoring meter 10-1 and a No. 2 fluoride ion concentration real-time monitoring meter 10-2. The No. 2 pH real-time monitoring meter 10-1 is used to monitor the pH of the outlet water, and the No. 2 fluoride ion concentration real-time monitoring meter 10-2 is used to monitor the fluoride concentration of the outlet water.

[0090] The fixed bed reactor 8 is provided with a water inlet 8-1 at the bottom and a water outlet 8-2 at the top; the outlet position of the mixing water storage tank 6 is connected to the water inlet 8-1 of the fixed bed reactor 8 through the No. 2 water inlet pump 7; the effluent after the reaction of the fixed bed reactor 8 is connected to the water outlet tank 10 through a pipeline through the water outlet 8-2.

[0091] The raw water tank 1 is provided with a liquid inlet on one side and a liquid outlet on the other side; the drug adding box 2 is provided with a drug inlet on one side and a drug outlet on the other side; the mixing water storage tank 6 is provided with a mixed water inlet on one side and a mixed water outlet on the other side; the water outlet tank 10 is provided with a drain outlet on one side and a water inlet on the upper part.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for defluoridating fluorine-containing groundwater, characterized in that: The process includes: S1. Obtaining the fluoride ion concentration, alkalinity and magnesium ion concentration of the actual fluoride-containing groundwater to be treated; S2, preparing simulated fluoride-containing water and phosphoric acid solution; the fluoride concentration of the simulated fluoride-containing water is the same as the fluoride ion concentration of the actual fluoride-containing groundwater; The phosphoric acid solution is mixed with simulated fluoride-containing water, and after calcium precipitation reaction treatment, the fluoride concentration of the effluent water is reduced to less than 1.0 mg / L; S3, continuously increasing the alkalinity of the simulated fluoridated water until the alkalinity of the simulated fluoridated water is the same as the alkalinity of the actual fluoridated groundwater; Add an acid to the phosphoric acid solution, mix the acidified phosphoric acid solution with alkaline simulated fluoride-containing water, control the pH of the mixed solution to 5.0-6.0, and treat it with calcium precipitation reaction to make the fluoride concentration of the effluent water lower than 1.0 mg / L; S4. On the basis of the alkalinity reaching the alkalinity of the actual fluoridated groundwater, magnesium salt is continuously added to the simulated fluoridated water according to the concentration characteristics of magnesium ions in the actual fluoridated groundwater, so that the magnesium ion concentration of the simulated fluoridated water is the same as that of the actual fluoridated groundwater; The phosphoric acid solution after acid addition is mixed with the simulated fluoride-containing water after magnesium salt addition, and the pH of the mixed solution is controlled at 5.0-6.

0. After calcium precipitation reaction treatment, the fluoride concentration of the effluent is less than 1.0 mg / L; S5. Replace the simulated fluoride-containing water with the actual fluoride-containing groundwater to be treated. At this time, the fluoride concentration in the effluent can be guaranteed to drop below 1.0 mg / L.

2. A control method for defluoridation of fluorine-containing groundwater according to claim 1, characterized in that: The calcium source required for the calcium precipitation reaction treatment is provided by the waste shell particles filled in the reactor.

3. A control method for defluoridation of fluorine-containing groundwater according to claim 1, characterized in that: In S3, the alkalinity of simulated fluoridated water was increased by adding bicarbonate; In S3, the acid agent is hydrochloric acid or sulfuric acid; In S4, the magnesium salt is magnesium chloride or magnesium sulfate.

4. A control method for defluoridation of fluorine-containing groundwater according to claim 1, characterized in that: In S2, after the phosphoric acid solution is mixed with the simulated fluoride-containing water, the molar ratio of phosphate to fluoride ion in the mixed solution is (2.0-6.0):

1.

5. A control method for defluoridation of fluorine-containing groundwater according to claim 1, characterized in that: In S3, after the acidified phosphoric acid solution is mixed with the alkaline simulated fluoride-containing water, the molar ratio of phosphate to fluoride ion in the mixed solution is (2.0-6.0):

1.

6. A control method for defluoridation of fluorine-containing groundwater according to claim 1, characterized in that: In S4, the phosphoric acid solution after acid addition is mixed with the simulated fluoride-containing water after magnesium salt is added, and the molar ratio of phosphate to fluoride ion in the mixed solution is (2.0-6.0):

1.

7. A control system for the control method for defluoridation of fluoride-containing groundwater according to any one of claims 1 to 6, characterized in that: It comprises a raw water tank (1), a dosing tank (2), a No. 1 water inlet pump (3), a dosing pump (4), a pipeline mixer (5), a mixed water storage tank (6), a No. 2 water inlet pump (7), a fixed bed reactor (8) and a water outlet tank (10); The simulated fluoride-containing water and actual groundwater are stored in the raw water tank (1) during operation; The phosphoric acid solution and the phosphoric acid solution with acid added are added into the drug adding box (2); The raw water tank (1) is connected to the first water inlet pump (3), and the dosing box (2) is connected to the dosing pump (4); The first water inlet pump (3) and the dosing pump (4) are both connected to a pipeline mixer (5), and the pipeline mixer is connected to a mixing water storage tank (6); The outlet of the mixing water storage tank (6) is connected to the fixed bed reactor (8) via a No. 2 water inlet pump (7); The effluent after the reaction in the fixed bed reactor (8) is connected to the effluent pool (10) through a pipeline; A No. 1 fluoride ion concentration real-time monitoring meter (1-1) and an alkalinity meter (1-2) are provided in the raw water tank (1); A No. 1 pH real-time monitoring meter (6-1) is provided in the mixing water storage tank (6); A No. 2 pH real-time monitoring meter (10-1) and a No. 2 fluoride ion concentration real-time monitoring meter (10-2) are provided in the water outlet pool (10).

8. The control system according to claim 7, characterized in that: The fixed bed reactor is filled with waste shell particles with a particle size of 0.5-1 mm.

9. The control system according to claim 7, characterized in that: The fixed bed reactor (8) is provided with a water inlet (8-1) at the bottom and a water outlet (8-2) at the top; the outlet of the mixing water storage tank (6) is connected to the water inlet (8-1) of the fixed bed reactor (8) via a second water inlet pump (7); The effluent after the reaction in the fixed bed reactor (8) is connected to the effluent pool (10) through a pipeline via the effluent outlet (8-2); A raw water tank (1) is provided with a liquid inlet on one side and a liquid outlet on the other side; The medicine adding box (2) is provided with a medicine inlet on one side and a medicine outlet on the other side; A mixed water inlet is provided on one side of the mixed water storage tank (6), and a mixed water outlet is provided on the other side; a water outlet is provided on one side of the water outlet tank (10), and a water inlet is provided on the upper part.

10. The control system according to any one of claims 7 to 9, characterized in that: The fixed bed reactor (8) is also provided with a water inlet phase; a third water inlet pump (9) is provided between the fixed bed reactor (8) and the water outlet tank (10); When flushing the fixed bed reactor (8), the effluent collected in the effluent pool (10) is used as flushing water, and the effluent pool (10) is connected to the inlet of the fixed bed reactor (8) via the No. 3 inlet pump (9).

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