Reinforced coagulation method for synergistically removing fluorides and high-toxicity disinfection byproducts in polluted underground water

Abstract

The invention relates to the technical field of water treatment, and discloses a reinforced coagulation method for synergistically removing fluorides and high-toxicity disinfection byproducts in polluted underground water. The method comprises the following steps: (1) taking a water sample to be treated from underground water to be treated, detecting the initial fluorine ion concentration and the initial DOC content of the water sample to be treated, and adjusting the pH value to 4.5-5.5 to obtain a treated water sample; (2) adding a zirconium salt coagulant into the treated water sample, carrying out pre-coagulation treatment, and detecting the pH value of the pre-coagulated effluent; (3) adding lime milk or calcium oxide into the water sample obtained in the step (2) to adjust the pH value of the water sample obtained in the step (2), and recording the addition amount of the lime milk or calcium oxide; and (4) adding the zirconium salt coagulant and the slaked lime solution into the underground water to be treated, and performing coagulation treatment. The method provided by the invention has the advantages of easily available raw materials, high fluoride removal rate, good toxicity reduction effect of high-toxicity disinfection byproducts, high DOC removal rate and good UV254 removal effect.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to an enhanced coagulation method for synergistically removing fluoride and highly toxic disinfection by-products from contaminated groundwater. Background Art

[0002] Groundwater is an important water source, especially in semi-arid regions. However, urbanization, industrialization, and agriculture are seriously threatening the quality and availability of groundwater resources.

[0003] Among them, the important pollutants in groundwater are fluoride and dissolved organic matter (DOM). In the case of complex and hidden groundwater pollution, it is difficult for traditional technologies to treat important pollutants to restore water quality and purify it to its original level. In addition, the concentration of fluoride ions in groundwater and dissolved organic matter in groundwater are also important precursors for the formation of disinfection by-products, which can cause many hazards to human health.

[0004] The common method for treating groundwater containing fluoride and dissolved organic matter is coagulation and sedimentation. The commonly used precipitation method for drinking water is composite polyaluminium chloride (PAC) and polyacrylamide (PAM) coagulation and sedimentation to deeply remove fluorine from fluoride-containing wastewater. This method has problems such as low fluoride removal efficiency, large amount of coagulant used, and high metal concentration in effluent. Therefore, it is necessary to optimize and improve the treatment method of fluoride-containing wastewater to reduce treatment costs and improve treatment effects.

[0005] In recent years, zirconium salt coagulants have received extensive attention as new water treatment coagulants. Studies have shown that zirconium-based materials have great potential for removing turbidity, organic matter, inorganic anions and microorganisms. Zirconium salt coagulants have a high affinity for fluoride, can remove fluoride more effectively than aluminum sulfate under acidic conditions, and show good coagulation performance over a wide pH range. Inorganic zirconium salt coagulants can effectively remove organic matter, thereby minimizing the generation of disinfection by-products.

[0006] Application No. 202210203422.3 discloses a method for preparing a polyzirconium coagulant, which has excellent fluoride removal effect, but the preparation process involves toxic acetylacetone and the preparation process is complicated.

[0007] Application No. 201410647876.5 discloses a method for strengthening coagulation to reduce the generation of disinfection byproducts. This method has excellent disinfection byproduct reduction effects, but the pre-oxidation technology used in it will increase the risk of secondary disinfection when treating highly polluted water. Application No. 201711390548.1 discloses a method for preparing a polyzirconium-aluminum chloride inorganic high-efficiency flocculant. This flocculant has a high efficiency in removing organic matter, but cannot explain the removal effect on highly toxic disinfection byproduct precursors.

[0008] It can be seen that further development of enhanced coagulation application technology of zirconium salt coagulants will be beneficial to solving the existing technical problems of groundwater treatment. Summary of the invention

[0009] The purpose of the present invention is to provide an enhanced coagulation method for synergistically removing fluoride and highly toxic disinfection by-products from contaminated groundwater based on the above technical problems.

[0010] In order to achieve the above-mentioned object, the first aspect of the present invention provides an enhanced coagulation method for synergistically removing fluoride and highly toxic disinfection by-products from contaminated groundwater, the method comprising the following steps:

[0011] (1) Taking a water sample to be treated from the groundwater to be treated, and detecting the initial pH value, initial fluoride ion concentration, initial DOC content, initial UV 254 , and then adjust the pH to 4.5-5.5 to obtain the treated water sample;

[0012] (2) adding a zirconium salt coagulant to the treated water sample for pre-coagulation treatment, and detecting the pH value of the effluent after the pre-coagulation;

[0013] (3) adding lime milk or calcium oxide to the water sample obtained in step (2) to adjust the pH of the water sample obtained in step (2) to 4.5-5.5, and recording the amount of lime milk or calcium oxide added;

[0014] (4) taking a zirconium salt coagulant and a slaked lime solution, adding them to the groundwater to be treated for coagulation treatment; the coagulation treatment is the same as the pre-coagulation treatment in step (2).

[0015] Preferably, in step (1), hydrochloric acid or sulfuric acid is used to adjust the pH value.

[0016] Further preferably, in step (2), the zirconium salt coagulant is selected from at least one of zirconium sulfate, zirconium oxychloride and zirconium chloride, preferably zirconium oxychloride.

[0017] Preferably, in step (2), the ratio of the initial fluoride ion concentration of the water sample to be treated to the added amount of the zirconium salt coagulant is 1:3-5.

[0018] More preferably, the ratio of the initial DOC content of the water sample to be treated to the added amount of the zirconium salt coagulant is 1.2:0.5-5.

[0019] Preferably, in step (2), the zirconium salt coagulant is zirconium oxychloride, and the initial DOC content is related to the amount of Zr in the zirconium oxychloride added. 4+ The content ratio is 1.2:0.5~5.

[0020] Preferably, in step (2), the pre-coagulation treatment includes sequentially performing a first stirring treatment, a second stirring treatment, and a sedimentation treatment.

[0021] Further preferably, in step (2), the conditions for the first stirring treatment meet the following requirements: the rotation speed is 100 to 250 rpm and the time is 15 to 90 s; the conditions for the second stirring treatment meet the following requirements: the rotation speed is 20 to 50 rpm and the time is 7 to 10 min; the conditions for the precipitation treatment meet the following requirements: the time is 10 to 40 min.

[0022] Preferably, in step (4), the amount of the zirconium salt coagulant used is the same as that of the zirconium salt coagulant used in step (2); and the amount of the slaked lime solution used is the same as that of the lime milk or calcium oxide used in step (3).

[0023] The method provided by the present invention has at least the following beneficial effects:

[0024] (1) The coagulation method provided by the present invention has the advantages of easy raw material acquisition, high fluoride removal rate, good disinfection by-product toxicity reduction effect, high DOC removal rate, and good UV254 removal effect.

[0025] (2) The method provided by the present invention is simple, safe and pollution-free. Compared with the traditional coagulation process, it can effectively improve the fluoride removal effect and reduce the toxicity of disinfection by-products.

[0026] (3) In the present invention, the zirconium salt coagulant is an important technical feature, and its function is to remove fluoride in contaminated groundwater and inhibit the formation of highly toxic disinfection by-products; the mechanism of action of the technical solution of the present invention is that the zirconium salt coagulant hydrolyzes and polymerizes to produce hydrolysis products with different polymerization degrees, and there is electrostatic interaction, ion exchange and hydrogen bond formation between the zirconium salt coagulant and the fluoride ion, and the formation of highly toxic disinfection by-products is inhibited under acidic conditions.

[0027] (4) In the present invention, slaked lime is an important technical feature, and its function is to maintain the pH of the coagulation process, synergistically remove fluoride, and provide crystal nuclei for floc formation. The mechanism of action of the technical solution of the present invention is that slaked lime maintains the pH required for efficient coagulation of the zirconium salt coagulant, reacts with calcium fluoride to form calcium fluoride precipitation, and provides crystal nuclei for floc formation, combining tiny suspended matter or colloidal particles in the water with crystalline calcium fluoride with extremely small particle size, which is beneficial to the collision and destabilization of calcium fluoride and colloidal particles or suspended particles to form flocs, promotes the aggregation of flocs and improves the ability to capture pollutants. The high relative density of flocs also greatly increases the sedimentation rate, accelerating solid-liquid separation and organic matter removal. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a comparison chart of the removal efficiency of fluoride ions in the embodiment of the present invention and the comparative example;

[0029] Figure 2 It is a comparison chart of the concentration change of dissolved organic carbon (DOC) in the effluent of the embodiment of the present invention and the comparative example;

[0030] Figure 3 UV in the effluent of the embodiments of the present invention and the comparative examples 254 Value change comparison chart;

[0031] Figure 4 is a comparison diagram of turbidity changes in the effluent of the embodiment of the present invention and the comparative example;

[0032] Figure 5 is a comparison chart of metal concentrations in the effluent of the embodiment of the present invention and the comparative example;

[0033] Figure 6 This is a comparison chart of the molecular weight of organic matter in the effluent of the embodiment of the present invention and the comparative example;

[0034] Figure 7 : is a comparison diagram of the generation potential of disinfection by-products in the effluent of the embodiment of the present invention and the comparative example;

[0035] Figure 8 It is a comparison chart of the calculated toxicity results of disinfection by-products in the effluent of the embodiment of the present invention and the comparative example;

[0036] Fig. 9 Graph showing the removal efficiency of fluoride ions in an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0038] The present invention will be described in detail below by way of examples. In the following examples, unless otherwise specified, the raw materials are all commercially available.

[0039] In the following examples, the groundwater to be treated is contaminated groundwater.

[0040] Example 1

[0041] This example is used to provide an enhanced coagulation method for synergistically removing fluoride and highly toxic disinfection by-products from contaminated groundwater. The method includes the following steps:

[0042] (1) Take 500 mL of water sample from the groundwater to be treated and test the initial pH value, initial fluoride ion concentration, initial DOC content, initial UV254 , and then adjust the pH value to 4.5 with 36.5wt% hydrochloric acid to obtain a treated water sample; the initial pH value is 7.81, the initial fluoride ion concentration is 4mg / L, the initial DOC content is 4.24mg / L, and the initial UV 254 It is 0.072.

[0043] (2) adding zirconium oxychloride to the treated water sample for pre-coagulation treatment, and detecting the pH value of the pre-coagulation effluent; Zr in the zirconium oxychloride 4+ The ratio of the content to the initial DOC content is 0.5:1.2, that is, in this embodiment, the amount of zirconium oxychloride used is 3.46 mg / L;

[0044] The pre-coagulation treatment includes a first stirring treatment, a second stirring treatment, and a sedimentation treatment in sequence; the conditions for the first stirring treatment are as follows: a rotation speed of 100 to 250 rpm and a time of 15 to 90 s; the conditions for the second stirring treatment are as follows: a rotation speed of 20 to 50 rpm and a time of 7 to 10 min; the conditions for the sedimentation treatment are as follows: a time of 10 to 40 min.

[0045] (3) Adding a 5 wt % slaked lime solution to the water sample obtained in step (2) to adjust the pH value of the water sample obtained in step (2) to 4.5, and recording the amount of the 5 wt % slaked lime solution added (the amount of the slaked lime solution added in this embodiment is 0.1 mL).

[0046] (4) taking zirconium oxychloride (the amount is the same as the zirconium oxychloride described in step (2)) and 5wt% slaked lime solution (the amount is the same as the slaked lime solution described in step (3)), adding them to the groundwater to be treated for coagulation treatment; the coagulation treatment is the same as the pre-coagulation treatment described in step (2).

[0047] Example 2

[0048] The method is similar to that of Example 1, except that in step (2), the zirconium oxychloride Zr 4+ The ratio of the content to the initial DOC content is 1:1.2, that is, the dosage of the zirconium oxychloride is 6.91 mg / L; in step (3), the addition amount of the slaked lime solution is 0.3 mL, and the remaining steps and parameters are the same as in Example 1.

[0049] Example 3

[0050] The method is similar to that of Example 1, except that in step (2), the zirconium oxychloride Zr 4+The ratio of the content to the initial DOC content is 2:1.2, that is, the dosage of the zirconium oxychloride is 13.81 mg / L; in step (3), the addition amount of the slaked lime solution is 0.5 mL, and the remaining steps and parameters are the same as in Example 1.

[0051] Example 4

[0052] The method is similar to that of Example 1, except that in step (2), the zirconium oxychloride Zr 4+ The ratio of the content to the initial DOC content is 3:1.2, that is, the dosage of the zirconium oxychloride is 20.74 mg / L; in step (3), the addition amount of the slaked lime solution is 0.7 mL, and the remaining steps and parameters are the same as in Example 1.

[0053] Example 5

[0054] The method is similar to that of Example 1, except that in step (2), the zirconium oxychloride Zr 4+ The ratio of the content to the initial DOC content is 4:1.2, that is, the amount of zirconium oxychloride used is 27.65 mg / L; in step (3), the amount of slaked lime solution added is 1.0 mL, and the remaining steps and parameters are the same as in Example 1.

[0055] Example 6

[0056] The method is similar to that of Example 1, except that in step (2), the zirconium oxychloride Zr 4+ The ratio of the content to the initial DOC content is 5:1.2, that is, the dosage of the zirconium oxychloride is 34.56 mg / L; in step (3), the addition amount of the slaked lime solution is 1.2 mL, and the remaining steps and parameters are the same as in Example 1.

[0057] Comparative Example 1

[0058] D1: The method is similar to that of Example 1, except that: in step (1), the pH value is adjusted to 6.5 with 5 wt % hydrochloric acid; in step (2), aluminum sulfate is used to replace the zirconium oxychloride; in step (2), Al in the aluminum sulfate is 3+ The ratio of the content to the initial DOC content is 0.5:1.2 (wherein the amount of aluminum sulfate is 4.72 mg / L); in step (3), the amount of slaked lime solution added is 0.3 mL, and the remaining steps and parameters are the same as in Example 1.

[0059] D2: The method is similar to that of Example 1, except that: in step (1), the pH value is adjusted to 6.5 with 5 wt % hydrochloric acid; in step (2), aluminum sulfate is used to replace the zirconium oxychloride; in step (2), Al in the aluminum sulfate is3+ The ratio of the content to the initial DOC content is 1:1.2 (wherein the amount of aluminum sulfate is 9.44 mg / L); in step (3), the amount of slaked lime solution added is 0.5 mL, and the remaining steps and parameters are the same as in Example 1.

[0060] D3: The method is similar to that of Example 1, except that: in step (1), the pH value is adjusted to 6.5 with 5 wt % hydrochloric acid; in step (2), aluminum sulfate is used to replace the zirconium oxychloride; in step (2), Al in the aluminum sulfate is 3+ The content is 2:1.2 (wherein the amount of aluminum sulfate is 18.88 mg / L); in step (3), the amount of slaked lime solution added is 1.0 mL, and the remaining steps and parameters are the same as in Example 1.

[0061] D4: The method is similar to that of Example 1, except that: in step (1), the pH value is adjusted to 6.5 with 5 wt % hydrochloric acid; in step (2), aluminum sulfate is used to replace the zirconium oxychloride; in step (2), Al in the aluminum sulfate is 3+ The ratio of the content to the initial DOC content is 3:1.2 (wherein the amount of aluminum sulfate is 28.32 mg / L); in step (3), the amount of slaked lime solution added is 1.5 mL, and the remaining steps and parameters are the same as in Example 1.

[0062] D5: The method is similar to that of Example 1, except that: in step (1), the pH value is adjusted to 6.5 with 5 wt % hydrochloric acid; in step (2), aluminum sulfate is used to replace the zirconium oxychloride; in step (2), Al in the aluminum sulfate is 3+ The content is 4:1.2 to the initial DOC content (wherein the amount of aluminum sulfate is 37.76 mg / L); in step (3), the amount of slaked lime solution added is 1.8 mL, and the remaining steps and parameters are the same as in Example 1.

[0063] D6: The method is similar to that of Example 1, except that: in step (1), the pH value is adjusted to 6.5 with 5 wt % hydrochloric acid; in step (2), aluminum sulfate is used to replace the zirconium oxychloride; in step (2), Al in the aluminum sulfate is 3+ The ratio of the content to the initial DOC content is 5:1.2 (wherein the amount of aluminum sulfate is 47.2 mg / L); in step (3), the amount of slaked lime solution added is 2.5 mL, and the remaining steps and parameters are the same as in Example 1.

[0064] Comparative Example 2

[0065] E1: The method disclosed in the prior art is carried out, and the main differences from Example 1 of the present invention are: in step (1), the pH value is not adjusted; in step (2), aluminum sulfate is used as a coagulant; in step (3), slaked lime solution is not used; in step (2), Al in the aluminum sulfate is 3+ The content is ratioed to the initial DOC content of 0.5:1.2 (wherein the amount of aluminum sulfate used is 4.72 mg / L).

[0066] E2: The method disclosed in the prior art is carried out, and the main differences from Example 1 of the present invention are: in step (1), the pH value is not adjusted; in step (2), aluminum sulfate is used as a coagulant; in step (3), slaked lime solution is not used; in step (2), Al in the aluminum sulfate is 3+ The content is 1:1.2 to the initial DOC content (wherein the amount of aluminum sulfate used is 9.44 mg / L).

[0067] E3: The method disclosed in the prior art is carried out, and the main differences from Example 1 of the present invention are: in step (1), the pH value is not adjusted; in step (2), aluminum sulfate is used as a coagulant; in step (3), slaked lime solution is not used; in step (2), Al in the aluminum sulfate is 3+ The content is 2:1.2 compared to the initial DOC content (wherein the amount of aluminum sulfate used is 18.88 mg / L).

[0068] E4: The method disclosed in the prior art is carried out, and the main differences from Example 1 of the present invention are: in step (1), the pH value is not adjusted; in step (2), aluminum sulfate is used as a coagulant; in step (3), slaked lime solution is not used; in step (2), Al in the aluminum sulfate is 3+ The ratio of the content to the initial DOC content is 3:1.2 (wherein the amount of aluminum sulfate used is 28.32 mg / L).

[0069] E5: The method disclosed in the prior art is carried out, and the main differences from Example 1 of the present invention are: in step (1), the pH value is not adjusted; in step (2), aluminum sulfate is used as a coagulant; in step (3), slaked lime solution is not used; in step (2), Al in the aluminum sulfate is 3+ The content is 4:1.2 to the initial DOC content (wherein the amount of aluminum sulfate used is 37.76 mg / L).

[0070] E6: The method disclosed in the prior art is carried out, and the main differences from Example 1 of the present invention are: in step (1), the pH value is not adjusted; in step (2), aluminum sulfate is used as a coagulant; in step (3), slaked lime solution is not used; in step (2), Al in the aluminum sulfate is 3+ The ratio of the content to the initial DOC content is 5:1.2 (wherein the amount of aluminum sulfate used is 47.20 mg / L).

[0071] Among them, the method disclosed in the prior art is the method disclosed in "Journal of Health Research and Reviews|January-April 2014|Volume 1|Issue 1".

[0072] Test Example 1

[0073] Summarize the removal efficiency of fluoride ions in the above examples and comparative examples (results are as follows Figure 1 ), the concentration changes of dissolved organic carbon (DOC) (results as shown Figure 2 As shown), UV 254 Value changes (results such as Figure 3 ), turbidity changes (results as shown Figure 4 ), metal concentration (results as shown Figure 5 shown).

[0074] Depend on Figure 1 It can be seen that when the coagulant dosage is 5:1.2: the fluoride ion removal efficiency in Example 6 of the present invention using zirconium oxychloride is 80.0%, while the fluoride ion removal efficiency in Comparative Example 1 after using aluminum sulfate coagulant is 60.5%. At the same coagulant dosage, the fluoride ion removal efficiency in Comparative Example 2 is 46.0%.

[0075] Depend on Figure 2 It can be seen that after the contaminated groundwater was treated with zirconium oxychloride and slaked lime for enhanced coagulation in Examples 1 to 6 of the present invention, the concentration of dissolved organic carbon (DOC) decreased from 4.24 mg / L to 2.69 mg / L. After the contaminated groundwater was treated with zirconium oxychloride and slaked lime in Comparative Example 1, the DOC concentration decreased from 4.24 mg / L to 3.47 mg / L. Under the same coagulant dosage, the DOC concentration in Comparative Example 2 decreased from 4.24 mg / L to 2.96 mg / L.

[0076] Depend on Figure 3 It can be seen that after the contaminated groundwater is subjected to enhanced coagulation treatment using zirconium oxychloride and slaked lime in Examples 1 to 6 of the present invention, UV 254 From 0.072 to 0.034. In comparative example 1, after aluminum sulfate and slaked lime were used to treat the contaminated groundwater, UV254 From 0.072 to 0.049. Under the same coagulant dosage, UV 254 Reduced from 0.072 to 0.054.

[0077] Depend on Figure 4 It can be seen that after the contaminated groundwater was treated with zirconium oxychloride and slaked lime for enhanced coagulation in Examples 1 to 6 of the present invention, the turbidity was reduced from 8.61 NTU to 0.72 NTU. After the contaminated groundwater was treated with aluminum sulfate and slaked lime in Comparative Example 1, the turbidity was reduced from 8.61 NTU to 0.78 NTU. At the same amount of coagulant, the turbidity in Comparative Example 2 was reduced from 8.61 NTU to 1.21 NTU.

[0078] Depend on Figure 5 It can be seen that after the contaminated groundwater was treated with zirconium oxychloride and slaked lime for enhanced coagulation in Examples 1 to 6 of the present invention, the metal concentration of the effluent was lower than 0.2 mg / L. However, after the contaminated groundwater was treated with aluminum sulfate and slaked lime in Comparative Example 1, there was a risk of exceeding the standard for the metal concentration of the effluent. Under the same coagulant dosage, the metal concentration of the effluent in Comparative Example 2 was higher than that in Example 1.

[0079] Test Example 2

[0080] Summarizing the molecular weight of organic matter in the above examples and comparative examples, the results are as follows Figure 6 shown.

[0081] Depend on Figure 6 It can be seen that under the same coagulant dosage, the reduction range of each molecular weight in Examples 1 to 6 of the present invention is higher than that in Comparative Examples 1 and 2.

[0082] Test Example 3

[0083] Summarizing the potential for generation of disinfection byproducts in the effluent of the above embodiments and comparative examples, the results are as follows Figure 7 shown.

[0084] Depend on Figure 7 It can be seen that after the contaminated groundwater is subjected to enhanced coagulation treatment by zirconium oxychloride and slaked lime in Examples 1 to 6 of the present invention, the generation potential of disinfection byproducts in the effluent can be reduced from 672.10 μg / L to 361.25 μg / L. In Comparative Example 1, the generation potential of disinfection byproducts in the effluent is reduced from 672.10 μg / L to 407.68 μg / L after the contaminated groundwater is treated by aluminum sulfate and slaked lime. Under the same coagulant dosage, the generation potential of disinfection byproducts in Comparative Example 2 is reduced from 672.10 μg / L to 516.59 μg / L.

[0085] Test Example 4

[0086] Summarizing the above examples and comparative examples, the toxicity of disinfection by-product generation potential in the effluent water was calculated. The results are as follows Figure 8 shown.

[0087] Depend on Figure 8 It can be seen that after the contaminated groundwater is subjected to enhanced coagulation treatment using zirconium oxychloride and slaked lime in Examples 1 to 6 of the present invention, the calculated toxicity of the disinfection byproduct formation potential of the effluent can be increased from 20.36×10 -3 Cut to 11.08×10 -3 In Comparative Example 1, the toxicity of the disinfection by-product formation potential of the effluent after the contaminated groundwater was treated with aluminum sulfate and slaked lime was calculated from 20.36×10 -3 Cut to 19.59×10 -3 At the same coagulant dosage, the calculated toxicity of the disinfection by-product generation potential in Comparative Example 2 increased from 20.36×10 -3 Increased to 20.99×10 -3 .

[0088] In order to more clearly express the method of the present invention, the present invention is Fig. 9 The fluoride ion removal efficiency results of the embodiment of the present invention are shown in FIG. Fig. 9 It can be seen that with the increase in the dosage of zirconium oxychloride, the fluoride ion concentration in the effluent water decreased continuously from 4.0 mg / L to a minimum of 0.8 mg / L.

[0089] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. An enhanced coagulation method for synergistically removing fluoride and highly toxic disinfection by-products from contaminated groundwater, characterized in that: The method comprises the following steps: (1) Taking a water sample to be treated from the groundwater to be treated, and detecting the initial pH value, initial fluoride ion concentration, initial DOC content, initial UV 254 , and then adjust the pH to 4.5-5.5 to obtain the treated water sample; (2) adding a zirconium salt coagulant to the treated water sample for pre-coagulation treatment, and detecting the pH value of the effluent after the pre-coagulation; (3) adding lime milk or calcium oxide to the water sample obtained in step (2) to adjust the pH of the water sample obtained in step (2) to 4.5-5.5, and recording the amount of lime milk or calcium oxide added; (4) taking a zirconium salt coagulant and a slaked lime solution, adding them to the groundwater to be treated for coagulation treatment; the coagulation treatment is the same as the pre-coagulation treatment in step (2).

2. The method according to claim 1, wherein: In step (1), hydrochloric acid or sulfuric acid is used to adjust the pH value.

3. The method according to claim 1 or 2, wherein: In step (2), the zirconium salt coagulant is selected from at least one of zirconium sulfate, zirconium oxychloride and zirconium chloride, preferably zirconium oxychloride.

4. The method according to claim 1 or 2, wherein: In step (2), the ratio of the initial fluoride ion concentration of the water sample to be treated to the amount of the zirconium salt coagulant added is 1:3-5; And / or, the ratio of the initial DOC content of the water sample to be treated to the added amount of the zirconium salt coagulant is 1.2:0.5-5.

5. The method according to claim 3 or 4, wherein: In step (2), the zirconium salt coagulant is zirconium oxychloride, and the initial DOC content is related to the amount of Zr in the zirconium oxychloride added. 4+ The content ratio is 1.2:0.5~5.

6. The method according to claim 1 or 2, wherein: In step (2), the pre-coagulation treatment includes sequentially performing a first stirring treatment, a second stirring treatment, and a sedimentation treatment.

7. The method according to claim 6, wherein: In step (2), the conditions for the first stirring treatment are as follows: the rotation speed is 100 to 250 rpm and the time is 15 to 90 s; the conditions for the second stirring treatment are as follows: the rotation speed is 20 to 50 rpm and the time is 7 to 10 min; the conditions for the precipitation treatment are as follows: the time is 10 to 40 min.

8. The method according to claim 1 or 2, wherein: In step (4), the amount of the zirconium salt coagulant used is the same as that of the zirconium salt coagulant used in step (2); the amount of the slaked lime solution used is the same as that of the lime milk or calcium oxide used in step (3).

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