A method and prevention and control evaluation system for acid wastewater pollution in historical mining areas

Abstract

The present invention relates to a method for the prevention and control of acid wastewater pollution in historical mining areas and a prevention and control evaluation system. The method combines the mutual influence among pH, chromaticity and total iron concentration of water bodies in historical pyrite mining areas to obtain a minimum total iron concentration value as the total iron concentration emission limit of the water body at the mining area outlet, and conducts treatment according to the emission limit so that the total iron concentration, pH and chromaticity of the water body at the water outlet meet the emission requirements. The method can effectively control the pollution control cost on the basis of solving the pollution problem caused by the acid wastewater in the mining area entering the river, and avoid excessive pollution control.

Description

Technical Field

[0001] The present invention relates to the technical field of water pollution control and management in pyrite mining areas, and more specifically to a method for preventing and controlling acid wastewater pollution in historical mining areas and a prevention and control evaluation system. Background Art

[0002] At present, there are two main types of mining areas in my country, namely, producing mining areas and historical mining areas. Among them, historical mining areas refer to abandoned mining areas that are currently abandoned and will no longer be used for mining activities in the future. Abandoned mines and slag form acidic wastewater (untreated, pH value <6) under the action of air oxidation and rainwater leaching. At the same time, because the ore contains heavy metal impurity elements such as Gu, Zn, Pb, and Fe, the wastewater also contains heavy metals. Moreover, most of the historical mining areas are distributed in karst areas such as the southwest area (mostly karst karst landforms), especially in pyrite mining areas, where Fe in the wastewater 2+ Under acidic conditions, it is further oxidized to Fe 3 + , while Fe 3+ Hydrolysis generates iron hydroxide, which further reduces the pH value and increases the acidity of wastewater, while also making the water appear yellow-brown. The acidic water (also known as "sulfur water") from the karst mines in these historical mining areas will enter the karst pipeline through karst depressions, caves, and funnels, mix with karst groundwater, and then flow out through the underground river outlet, and finally flow into the river, which is easy to cause water pollution and damage the water ecological environment of the basin, and also threaten the health of local residents.

[0003] The water quality control standards for the basins and rivers where the mining area is located mainly refer to the "Surface Water Environmental Quality Standard" (GB3838-2002), but this standard only stipulates the water bodies within the drinking water source protection area for heavy metals such as iron and manganese in pyrite acid wastewater, and does not stipulate the indicators such as iron and manganese in non-drinking water source areas. If the pyrite acid wastewater treatment in non-drinking water source areas is controlled according to the requirements of the drinking water source protection area, it is easy to cause excessive treatment. Although the existing "Iron Ore Mining and Dressing Industrial Pollutant Emission Standard" (GB28661-2012) stipulates special emission limits for total iron and total manganese in water pollutants, including the total iron emission limit (5mg / L) in mining acid wastewater, it is for mining acid wastewater or ore dressing wastewater in the production area. There are corresponding governance responsible entities in the production mining area, and generally "repair and plugging" measures are taken for prevention and control after the mine is closed, but the historically missed mining areas often need to be managed by relevant departments. Governance according to the emission limits in the production mining area requires high requirements and is difficult to meet the standards, and is actually a transitional governance. Moreover, the underground rivers in the historical karst mining areas are complex and difficult to repair and seal. Simple covering with soil is not only difficult to neutralize the acidity in the matrix and prevent pyrite oxidation and re-acidification, but will aggravate the degree of soil re-acidification. In addition, the amount of acidic water fluctuates greatly with the combined influence of precipitation, groundwater level, etc. and the causes are complex. As a result, large-scale management of abandoned karst mining areas requires a lot of manpower, material and financial resources. Even if large-scale management is carried out regardless of cost, it is difficult to achieve the management standards of existing mining areas in production.

[0004] It can be seen that in the absence of relevant standards for the discharge of acidic wastewater from historical mining areas, it is difficult to effectively and reasonably control the pollutants in acidic wastewater from historical mining areas based on existing technologies. Therefore, it is of great significance to study an effective and reasonable method for the prevention and control of acidic wastewater pollution in mining areas for the treatment of acidic wastewater from historical mining areas in non-drinking water source areas. Summary of the invention

[0005] In response to the above defects or improvement needs of the prior art, the present invention provides a method for the prevention and control of acidic wastewater pollution in historical mining areas and a prevention and control evaluation system. The purpose is to first determine the prevention and control indicators and their emission limits based on the characteristics of the historical pyrite mining areas, and then carry out treatment in accordance with the determined emission limits. After meeting the emission limit requirements, the wastewater is discharged into the river, thereby solving the technical problems that the prior art lacks effective and reasonable prevention and control methods for historical mining areas, and blindly preventing and controlling pollutants according to the existing emission standards for pyrite mines in production is likely to cause excessive treatment and increase costs.

[0006] To achieve the above object, according to one aspect of the present invention, a method for preventing and controlling acid wastewater pollution in historical mining areas is provided, wherein the mining area is a pyrite mine, and specifically comprises the following steps:

[0007] (1) Determine the total iron discharge concentration limit of the water body at the mine outlet:

[0008] 1-1: Take the untreated acid wastewater from the mining area and dilute it, measure the chromaticity and total iron concentration of the water samples at different dilution times, and analyze the linear relationship between the total iron concentration y1 and the chromaticity x, which is y1=k1*x+b1;

[0009] According to the chromaticity A1 corresponding to when the water color at the mine outlet just turns non-yellow, calculate the total iron concentration B1 corresponding to when the water color is A1;

[0010] 1-2: Take the untreated acidic wastewater from the mining area, add alkali to adjust its pH, measure the chromaticity and total iron concentration of the water sample with a pH range of 6 to 9, take the maximum value, record it as chromaticity A2 and total iron concentration B2 respectively; determine the total iron discharge concentration limit according to the following method:

[0011] The smaller integer value of total iron concentration B1 and B2 is used as the upper limit of total iron concentration in the water body at the mine outlet;

[0012] (2) treating the acidic wastewater from the mining area according to the total iron concentration emission limit determined in step (1) so that its total iron concentration meets the emission limit requirements, and at the same time, the pH value of the water body is 6 to 9 and the color of the water body at the outlet is not yellow.

[0013] Preferably, the method for the prevention and control of acid wastewater pollution in historical mining areas, in which step 1-2, further comprises supplementing the in-situ monitoring of the water pH and total iron concentration of the water quality at the mine outlet, using a polynomial fitting analysis to determine the mean of the critical values ​​of the total iron concentration within the 90% and 95% confidence intervals when the pH is between 6 and 9, recorded as B3;

[0014] The minimum concentration value among the total iron concentrations B1, B2 and B3 obtained is taken as the upper limit of the total iron concentration discharged from the water body at the mine outlet.

[0015] Preferably, the in-situ monitoring of the method for the prevention and control of acidic wastewater pollution in historical mining areas includes monitoring the pH and total iron concentration of the water quality at the mine outlet during the three phases of flood, normal and drought.

[0016] Preferably, in the method for preventing and controlling the pollution of acidic wastewater in historical mining areas, in step 1-1, after the untreated acidic wastewater in the mining area is diluted, its trivalent iron ion concentration is also measured, and the linear relationship between the trivalent iron ion concentration y2 and the chromaticity x is analyzed to obtain y2=k2*x+b2; and the trivalent iron ion concentration C1 corresponding to the chromaticity of the water body is A1 is calculated;

[0017] In step 1-2, after adjusting the pH, the concentration of trivalent iron ions in the water sample corresponding to a pH range of 6 to 9 is measured, and the maximum value is taken, which is recorded as C2;

[0018] The smaller value of the trivalent iron ion concentrations C1 and C2 is taken as the lower limit of the total iron concentration in the water body at the mine outlet.

[0019] Preferably, in the method for preventing and controlling acid wastewater pollution in historical mining areas, the pyrite is pyrite from historical non-water source areas.

[0020] Preferably, in the method for preventing and controlling acidic wastewater pollution in historical mining areas, the pyrite mine is a karst mine cave.

[0021] Preferably, in the method for prevention and control of acidic wastewater pollution in historical mining areas, the raw water at the pyrite outlet has a pH value of less than 4 and a total iron concentration of more than 300 mg / L, and the determined upper limit of total iron concentration emission is 60 mg / L. The water is treated according to the total iron concentration emission limit, and the pH value of the water quality at the outlet is 6-9 and the color is not yellow, which meets the emission requirements.

[0022] According to another aspect of the present invention, there is also provided a historical pyrite mining area acid wastewater pollution prevention and control assessment system, which includes a data acquisition module, a data analysis and judgment module and a result display module;

[0023] The data acquisition module is used to obtain the pH, chromaticity and total iron concentration of the water body at the outlet after the acid wastewater of the historical pyrite mine cave is treated, and submit it to the data analysis and judgment module;

[0024] The data analysis and judgment module is used to compare the obtained pH, chromaticity and total iron concentration with the corresponding preset emission limits to determine whether the acid wastewater pollution prevention and control in the pyrite mine area meets the standards. The specific judgment is as follows:

[0025] If the pH value, total iron concentration and chromaticity of the water at the outlet meet the corresponding preset emission limits, it is judged that the pollution prevention and control of acid wastewater in the historical pyrite mining area has met the standards;

[0026] If one or more indicators of the pH value, total iron concentration, and chromaticity of the water body at the outlet do not meet the corresponding preset emission limits, it is judged that the anti-pollution treatment of acid wastewater in the historical pyrite mining area does not meet the standards; and the judgment result is submitted to the result display module;

[0027] The result display module displays whether the anti-pollution treatment of acid wastewater in the mining area meets the standard or does not meet the standard according to the received judgment result.

[0028] Preferably, the historical pyrite mining area acid wastewater pollution prevention and control assessment system is characterized in that the preset emission limit is determined according to the method described in the present invention.

[0029] Preferably, in the historical pyrite mine area acidic wastewater pollution prevention and control assessment system, the raw water from the historical pyrite mine outlet has a pH value of less than 4 and a total iron concentration of more than 300 mg / L, a preset pH emission limit of 6 to 9, a preset upper limit emission value of total iron concentration of 60 mg / L, and a preset chromaticity emission limit of 50.

[0030] In general, compared with the prior art, the above technical solution conceived by the present invention combines the relationship between the pH, chromaticity and total iron concentration of the water body at the outlet to determine the total iron discharge concentration limit of the water body at the outlet of the historical pyrite mine, and can achieve the following beneficial effects:

[0031] The method for the prevention and control of pollution of acidic wastewater from historical mining areas provided by the present invention determines the emission limit of the total iron concentration of the water body at the outlet of the historical pyrite mine by combining the mutual influence of pH, chromaticity and total iron concentration of the water outlet of the mine cave, thus filling the gap of the pollution-free control standard such as the main pollution indicators of iron elements and the sensory impact of "sulfur water" in the historical pyrite mine area. According to this method, the treatment of acidic wastewater from historical pyrite mines can achieve the control of "sulfur water" entering the river on the one hand, and the total iron concentration emission requirement is lower than the emission standard requirement in the mining area on the other hand. On the basis of solving the pollution problem caused by the acidic wastewater entering the river in the mining area, the pollution control cost can be effectively controlled. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is the result of analyzing the relationship between the concentration of trivalent iron ions and the chromaticity of the water at the mine outlet;

[0033] Figure 2 It is the result of analyzing the relationship between the total iron concentration and chromaticity of the water at the mine outlet;

[0034] Figure 3 It is the result of analyzing the relationship between the concentration of trivalent iron ions and pH in the water body at the mine outlet;

[0035] Figure 4 It is the result of analyzing the relationship between the total iron concentration and pH of the water at the mine outlet;

[0036] Figure 5 It is the comparative analysis result of the supplementary monitoring data (total iron concentration and pH) at the mine outlet;

[0037] Figure 6 It is the comparative analysis result of the supplementary monitoring data (chromaticity and pH) of the mine water outlet;

[0038] Figure 7 is the upper limit of total iron concentration within the 90% confidence interval;

[0039] Figure 8 is the upper limit of the total iron concentration within the 95% confidence interval. DETAILED DESCRIPTION

[0040] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation mode, structure, characteristics and effects of the present invention are described in detail below in combination with the accompanying drawings and preferred embodiments.

[0041] At present, there is no standard for the management of pollutant discharge of acid wastewater from historical mining areas, and the wastewater from historical pyrite mining areas has a high iron content, making the water appear yellow. However, according to the current "Iron Ore Mining and Dressing Industry Pollutant Discharge Standard" (GB28661-2012), the total iron limit is 5mg / L, which is easy to cause excessive pollution prevention, resulting in excessively high costs for pollutant treatment in historical mining areas, especially in historical karst pyrite mining areas.

[0042] The water gushing out of the historical pyrite mine cave is acidic. Considering that the acidic wastewater directly entering the river will have an adverse impact on the original ecology of the river, the pH of the acidic wastewater at the mine outlet is used as one of the prevention and control indicators in the present invention.

[0043] The wastewater from the historical pyrite mine area has a high iron content, which makes the water body appear yellow. Considering coordinated control, the prevention and control indicators also include water color and total iron concentration. However, the pH, color and total iron concentration of mine wastewater affect each other. In order to study the correlation between the pH, color and total iron concentration of the water body at the outlet of the historical pyrite mine. In this experiment, acidic wastewater from the outlet of a historical pyrite mine was collected, diluted with distilled water, and the color, trivalent iron ions and total iron concentration corresponding to the water body at different dilution multiples were measured. The relationship between total iron concentration (y1), trivalent iron ions (y2) and color (x) was established through data analysis, and it was found that they all conform to the linear relationship y=k*x+b, R 2 >0.9, where the iron in the total iron concentration refers to elemental iron.

[0044] According to the water chromaticity requirements specified in the "Iron Ore Mining and Dressing Industry Pollutant Emission Standards", or measure the chromaticity corresponding to the change of the water color at the mine outlet from yellow to non-yellow, recorded as A1, and calculate the total iron concentration and trivalent iron ion concentration corresponding to the time when the water color at the mine outlet just reaches non-yellow according to the above relationship obtained, where the total iron concentration is recorded as B1 and the trivalent iron ion concentration is recorded as C1.

[0045] Furthermore, the pH of the acidic wastewater collected from the mine outlet was adjusted by adding alkali, the chromaticity, trivalent iron ion and total iron concentration corresponding to water bodies with different pH values ​​were determined, and the pH of the acidic wastewater from the mine was controlled between 6 and 9 with reference to the requirements of the surface water quality standard (GB3838-2002) for river pH. The maximum values ​​of the chromaticity, trivalent iron ion concentration and total iron concentration corresponding to the pH of the acidic wastewater from the mine were taken and recorded as chromaticity A2, total iron concentration B2 and trivalent iron ion concentration C2, respectively. The corresponding emission limits were determined specifically according to the following method:

[0046] The smaller value of total iron concentration B1 and B2 is used as the upper limit of total iron concentration in the water body at the mine outlet; the smaller value of trivalent iron ion concentration C1 and C2 is preferably used as the lower limit of total iron concentration in the water body at the mine outlet. When the total iron concentration of the water body at the outlet meets the discharge requirements according to the overall concentration discharge limit determined by this method, the pH of the water body is 6 to 9 and the chromaticity is ≤50, that is, the water body at the outlet also meets the discharge requirements of pH and chromaticity.

[0047] Furthermore, the experimental screening results are supported by supplementary monitoring data, such as the pH and total iron concentration data of the acidic wastewater at the outlet of the three phases of the mine cave in the rich, flat and dry periods, and polynomial fitting analysis is used to calculate the pH of the water body after the mine cave is controlled between 6-9, and the mean of the critical value of the total iron concentration within the 90% and 95% confidence intervals is recorded as B3, and the minimum integer concentration value among the total iron concentrations B1, B2 and B3 is preferably used as the upper limit of the total iron concentration required for the discharge of the water body at the outlet of the legacy pyrite mine cave. When the total iron concentration of the water body at the outlet meets the discharge requirements, its pH and chromaticity also meet the discharge requirements according to the determined total iron concentration limit.

[0048] Based on this, the present invention proposes a method for preventing and controlling acid wastewater pollution in historical mining areas, which comprises the following steps:

[0049] (1) Determine the control indicators and their emission limits: The pH, chromaticity and total iron concentration of acidic wastewater from historical pyrite mining areas were selected as control indicators. The main reason for selecting pH is that the wastewater from pyrite mining areas is acidic. The acidic water directly enters the river, causing the river to lose its self-purification ability and causing a great impact on the river ecology; the chromaticity was selected mainly because the yellow color of pyrite mine wastewater has a great impact on the senses of surrounding residents; the total iron concentration was selected mainly because, on the one hand, iron is the main metal pollutant in pyrite. Although other heavy metals have control target requirements in the surface water quality standard (GB3838-2002), there is no clear requirement for iron; on the other hand, the yellow color of mine acidic wastewater is mainly caused by trivalent iron ions, and the changes in trivalent iron ions in mine acidic wastewater are fluctuating and exist in various forms. In general, heavy metals in surface water are evaluated based on the total amount of metals. Therefore, the total iron concentration was selected as the control indicator, that is, the iron content was measured.

[0050] The emission limit values ​​for total iron concentration are determined as follows:

[0051] ① Dilution experiment: Take the untreated acidic wastewater from the mining area, add distilled water to dilute it, measure the water chromaticity, ferric iron concentration and total iron concentration at different dilution multiples, and analyze the linear relationship between total iron concentration, ferric iron concentration and chromaticity, which are y1=k1*x+b1 and y2=k2*x+b2 respectively; where y1 is the total iron concentration, y2 is the ferric iron concentration, and x is the chromaticity;

[0052] Determine the chromaticity A1 corresponding to the untreated acidic wastewater from the mine when it is diluted until its color changes from yellow to non-yellow, or calculate the corresponding total iron concentration B1 and trivalent iron ion concentration C1 of the water body according to the above formula based on the water chromaticity requirements specified in the "Iron Ore Mining and Dressing Industry Pollutant Emission Standards".

[0053] ② Adjust pH: Take the untreated acidic wastewater from the mining area, add alkali to adjust its pH (such as pH 3-9), measure the chromaticity, ferric iron ion concentration and total iron concentration corresponding to different pH values, determine the chromaticity, ferric iron ion concentration and total iron concentration corresponding to the pH range of 6-9, take the maximum value, record it as chromaticity A2, total iron concentration B2 and ferric iron ion concentration C2 respectively; and determine the discharge concentration limit corresponding to the total iron in the water body according to the following method:

[0054] The smaller integer value of total iron concentration B1 and B2 is used as the upper limit of total iron concentration in the water body at the mine outlet;

[0055] Preferably, the smaller value of the trivalent iron ion concentrations C1 and C2 is used as the lower limit of the total iron concentration discharged in the water body at the mine outlet.

[0056] (2) The total iron concentration in the water at the mine outlet is treated according to the discharge limit value determined in step (1), so that when the total iron concentration in the water at the mine outlet meets the discharge requirements, the pH value of the water is between 6 and 9 and the chromaticity meets the discharge requirements.

[0057] Preferably, step (1) further comprises supplementing the in-situ monitoring data of the untreated acidic wastewater of the mine for comprehensive analysis to determine the appropriate emission limit of total iron; the in-situ monitoring data includes the water quality pH and total iron concentration data of the acidic wastewater monitored in the mine area corresponding to the three periods of abundant, normal and dry seasons, further using a polynomial for fitting analysis, and calculating the mean of the minimum upper limit of the total iron concentration within the 90% and 95% confidence intervals when the pH of the water body at the outlet is controlled between 6 and 9, recorded as B3, and the upper limit of the total iron concentration emission is determined according to the following method:

[0058] The lowest concentration value among the total iron concentrations B1, B2 and B3 obtained is taken as the upper limit of the total iron concentration discharge in the water body at the outlet of the historical pyrite mine area.

[0059] In some embodiments, the mining area is a pyrite mine in a non-water source area left over from history. The acidic wastewater (the total iron concentration of the raw water is greater than 300 mg / L) at the outlet of the mining area is diluted by 1.5 times, 2 times, 3 times, 4 times, 6 times, 8 times and 10 times respectively, and the chromaticity, trivalent iron ion (Fe 3+ ) and total iron concentration, the relationship between total iron and chromaticity was obtained as y1=1.6265*x+50.938, R 2 =0.9225, where y1 is the total iron concentration and x is the chromaticity value;

[0060] The relationship between trivalent iron ions and chromaticity is y2 = 0.9919*x + 18.61, R 2 =0.9221, where y2 is the concentration of trivalent iron ions and x is the chromaticity value.

[0061] According to the requirement that the chromaticity of the water discharged from the outlet should be controlled below 50 degrees (the chromaticity is 50, and the water color is basically not yellow), the corresponding trivalent iron ion (Fe 3+ ) concentration ≤68.21mg / mL, total iron concentration ≤132.26mg / mL, and the integer 130mg / mL is selected as the possible total iron concentration emission limit.

[0062] The acidic wastewater (the pH value of the raw water is 3.14) from the outlet of the mine was taken, and the pH values ​​were adjusted to 4, 5, 6, 7, 8, and 9 respectively by adding alkali. The pH, chromaticity, and trivalent iron (Fe 3+ ) and total iron concentration, determine the pH between 6 and 9, the corresponding color, trivalent iron ion (Fe 3+) and the range of total iron concentration, among which the maximum chromaticity is A2, A2 is 40; the maximum total iron concentration is B2, B2 is 175.13 mg / mL; the maximum trivalent iron ion concentration is C2, C2 is 30 mg / mL.

[0063] Among them, the chromaticity value A2 is less than A1, and the smaller integer value of the total iron concentration B1 and B2 is used as the upper limit of the total iron concentration in the water body at the mine outlet; that is, the upper limit of the total iron concentration in the water body at the mine outlet is preliminarily determined to be 130 mg / mL. According to the treatment of the mine acid wastewater, the total iron concentration of the water body is ≤130 mg / mL, and the pH and chromaticity of the water body can meet the discharge requirements at the same time, wherein the pH of the discharged water body is required to be controlled at 6-9, and the color of the water body is not yellow (chromaticity ≤50). Preferably, the lower limit of the total iron concentration in the water body at the mine outlet is 30 mg / mL.

[0064] Furthermore, taking into account the complexity of the acidic wastewater in the historical pyrite mines, the in-situ monitoring data (pH, total iron concentration) of the acidic wastewater at multiple outlets corresponding to the three periods of abundance, normality and drought in the mining area were supplemented with the pH adjustment experiment to perform polynomial fitting analysis. It was analyzed that when the pH was between 6 and 9, the critical values ​​of the total iron concentration within the 90% and 95% confidence intervals were 62 mg / mL and 57.5 mg / mL, respectively. The average of the two (60 mg / mL) was preferred and recorded as B3.

[0065] According to the above screening results, the minimum total iron concentration value among B1, B2, and B3 is used as the upper limit of the total iron concentration of acidic wastewater discharged from the mine outlet, that is, the upper limit of the total iron concentration in the water body at the mine outlet is 60 mg / mL. According to the total iron discharge limit, the water body is treated. When the total iron concentration of the water body is ≤60 mg / mL after treatment, the water body chromaticity is ≤50, and the pH is between 6 and 9. All three meet the discharge requirements. After treatment, it can be discharged into rivers when it meets the discharge requirements. It is preferred to carry out anti-pollution control according to 30 mg / L≤total iron concentration≤60 mg / L.

[0066] In addition, the present invention also proposes a historical pyrite mining area acid wastewater pollution prevention and control assessment system, which includes a data acquisition module, a data analysis and judgment module and a result display module;

[0067] The data acquisition module is used to obtain the pH value, total iron concentration and chromaticity of the water sample at the outlet of the historical pyrite mine area after treatment, and submit it to the data analysis and judgment module;

[0068] The data analysis and judgment module compares the obtained pH value, total iron concentration and chromaticity with the corresponding preset limit values ​​to determine whether the acid wastewater pollution prevention and control in the pyrite mine area meets the standards. The specific judgment is as follows:

[0069] If the pH value, total iron concentration and chromaticity of the water at the outlet meet the corresponding preset emission limits, it is judged that the iron pollution prevention and control of the acid wastewater in the historical pyrite mining area has met the standards;

[0070] If at least one of the pH value, total iron concentration, and chromaticity of the water body at the outlet does not meet the corresponding preset emission limit, it is judged that the iron pollution prevention and control of the acid wastewater in the historical pyrite mine area does not meet the standard; and the judgment result is submitted to the result display module;

[0071] The result display module displays whether the iron pollution prevention and control meets the standard or not according to the result judged by the received data analysis and judgment module.

[0072] The preset limit value is analyzed and determined according to the method provided by the present invention.

[0073] In some embodiments, the pH of the raw water at the outlet is less than 4, and the preset emission limit of the total iron concentration is 60 mg / L, preferably 30 mg / L≤total iron concentration≤60 mg / L. The water body at the outlet is treated to make the total iron concentration meet the emission requirements. After treatment, the pH value of the water body is 6-9 and the chroma is ≤50.

[0074] The following are examples

[0075] Example 1

[0076] (1) Screening of the main pollution prevention and control indicators for the water outlets of karst pyrite mines in historical mining areas

[0077] This example uses a pyrite mine (karst mine cave) in a historical non-water source area in the southwest region as the research area. The water gushing from the mine cave in the pyrite mine area is acidic and yellow in color, and the main pollution indicator is heavy metals. The water gushing from the mine cave is acidic, and the direct entry of acidic water into the river will cause the microorganisms in the water body to be unable to reproduce normally, and the water body will gradually lose its self-purification ability. In addition, it will cause great harm to organisms such as fish, pollute the soil, acidify the soil, and kill plants. According to the requirements for the pH of discharged water quality in the "Surface Water Environmental Quality Standard" (GB3838-2002), the pH control requirements for the outlet of the mine cave are determined to be controlled at a pH of 6 to 9 for the outlet water quality.

[0078] Since the color of the mine water is obviously yellow, the yellow wastewater flowing into the river will have a greater visual impact. Although there are a lot of heavy metals in the mine water, considering that the "Surface Water Environmental Quality Standard" (GB3838-2002) Table 1 (Basic Item Standard Limits of Surface Water Environmental Quality Standards) has put forward control requirements for surface water quality, the emission limits corresponding to most heavy metals (but not iron and manganese) in the mine outlet can be calculated through the corresponding standard limits of surface water during the treatment process. Therefore, such heavy metals do not require additional discharge requirements and can be treated according to the existing emission requirements. However, iron and manganese heavy metals have a strong correlation, and the yellow color of the mine water is mainly caused by iron. Therefore, controlling the discharge concentration of iron in the water quality of the mine outlet is the key to the treatment of acidic wastewater. However, prevention and control according to the existing emission standards for iron in the producing mining area is likely to lead to excessive treatment of pyrite in non-water source areas left over from history, greatly increasing the cost of treatment. Therefore, for the pyrite mines left over from history in non-water source areas, the key to this method is to control the iron concentration of the water quality at its outlet within a range that can effectively control iron pollution while meeting the requirements for chromaticity and pH of the discharged water quality.

[0079] (2) Determine the chromaticity and iron ion (Fe 3+ ) and total iron concentration

[0080] The yellow color of the water at the outlet is related to the iron ion concentration and is also affected by the pH. In order to ensure that the chromaticity and pH of the water quality at the outlet meet the standards when the iron concentration at the outlet meets the standards, this embodiment studies the relationship between the chromaticity of the water body, pH, and the concentrations of trivalent iron ions and total iron. Specifically, the untreated acidic wastewater from the pyrite mine in the non-water source area left over from history is collected and diluted, and the corresponding water chromaticity, iron ion (Fe 3+ ), total iron concentration; specifically as follows:

[0081] The acidic wastewater collected from the mine outlet was diluted 1.5 times, 2 times, 3 times, 4 times, 6 times, 8 times and 10 times with distilled water, and the pH, chromaticity, iron ion (Fe 3+ ) and total iron concentration, wherein pH was determined using a pH meter, colorimetry was used for determination, and trivalent iron ion concentration was determined using the o-phenanthroline spectrophotometry (trial). The results are shown in the following table.

[0082] Table 1 Results of dilution test at the outlet of a pyrite mine in a historical non-water source area

[0083] Dilution multiple Chroma pH Ferric ion (mg / L) Total Iron (mg / L) Original solution 250 3.14 248.56 428.36 1.5 200 3.22 161.51 280.82 3 30 3.28 47.50 114.56 5 20 3.41 34.44 68.25 8 10 3.38 16.63 50.44 10 5 3.60 4.75 21.94

[0084] According to the test results in Table 1, the relationship between the chromaticity of the water at the mine outlet and the concentration of trivalent iron ions and total iron was analyzed. The results are as follows: Figure 1 and Figure 2 shown.

[0085] Depend on Figure 1 and Figure 2 It can be seen that the chromaticity of the mine outlet has a high correlation with both trivalent iron ions and total iron concentrations. The total iron concentration and the chromaticity of the water at the mine outlet satisfy the relationship: y1 = 1.6265x + 50.938, R 2 =0.9225, where y1 is the "total iron concentration" and x is the "color of the water at the mine outlet";

[0086] The concentration of trivalent iron ions and the chromaticity of the water at the mine outlet satisfy the relationship: y2 = 0.9919x + 18.61, R 2 =0.9221, where y2 is the "ferric ion concentration" and x is the "chromaticity of the water at the mine outlet".

[0087] The acidic wastewater collected from the mine outlet was diluted until it was just not yellow, and the corresponding chromaticity was measured. The results showed that the chromaticity corresponding to the acidic wastewater changing from yellow to not yellow was 50. According to the above relationship, the water body chromaticity was calculated to be ≤50, and the corresponding upper limits of the concentrations of trivalent iron ions and total iron in the water were rounded to the integers, that is, the concentration of trivalent iron ions was ≤68 mg / L and the concentration of total iron was ≤132 mg / L. Generally, the element concentration is used as the basis for water quality evaluation. Therefore, the total iron concentration is preferably selected as the prevention and control indicator. The total iron concentration refers to the concentration of the iron element. The more preferred limit value of the total iron concentration in the water quality of the mine outlet is 130 mg / L.

[0088] (3) Determine the relationship between pH, chromaticity and ferric iron and total iron concentrations at the mine outlet

[0089] Sodium hydroxide solution was added dropwise to the acidic wastewater sample collected from the mine outlet, and the solution was added and adjusted according to the pH value of the water sample of 3, 4, 5, 6, 7, 8, and 9. After standing, the chromaticity, trivalent iron ion and total iron concentration of the supernatant of the water sample at each pH value were measured. Since the amount of sodium hydroxide solution added was very small, the dilution caused by the addition of alkaline solution could be ignored. It can be considered that the changes in the chromaticity, trivalent iron ion and total iron concentration of the water sample were caused by the change in its pH. The specific measurement results are shown in Table 2.

[0090] Table 2 The results of pH, chromaticity, ferric iron and total iron concentration at the outlet of a mine

[0091]

[0092] According to the data in Table 2, the relationship between the pH of the water sample after alkali treatment and the concentration of trivalent iron ions and total iron was analyzed. The results are as follows: Figure 3 and Figure 4 shown.

[0093] Figure 3 This is a trend chart showing the concentration of trivalent iron ions in the water at the mine outlet as the pH of the water changes; Figure 4 This is a trend chart showing the total iron concentration in the water at the mine outlet as the pH of the water changes.

[0094] Depend on Figure 3 and Figure 4 It can be seen that with the increase of water pH, the concentrations of trivalent iron ions and total iron gradually decrease. When the pH is greater than 5, the concentrations of trivalent iron ions and total iron both decrease significantly. Referring to the surface water control requirements, the pH of the acidic wastewater at the mine outlet is controlled between 6 and 9, the concentration of trivalent iron ions is lower than 30 mg / L, and the total iron concentration is basically lower than 175 mg / L.

[0095] The smaller total iron concentration value screened out above is used as the upper limit of total iron concentration emission, that is, the total iron concentration is controlled below 130 mg / L when the acidic wastewater from the mine outlet is discharged, the water chromaticity is ≤49, and the water pH is between 7 and 9, which meets the requirements that the pH of the water at the outlet is 6 to 9 and the water color is basically not yellow (chromaticity is 50). This means that the acidic mine wastewater is treated according to the total iron concentration emission limit of 130 mg / L, and it can also meet the requirements for water chromaticity and pH when the wastewater is discharged.

[0096] Preferably, the minimum trivalent iron ion concentration value obtained is used as the lower limit of total iron concentration emission (i.e. 30 mg / L), and prevention and control management is carried out according to the total iron concentration limit determined by this method, so that the total iron concentration, chromaticity and pH of the treated water body meet the emission requirements, and excessive pollution treatment can be avoided.

[0097] Example 2

[0098] On the basis of Example 1, taking into account the complexity of the actual situation of mine acidic wastewater, statistical analysis was performed using supplementary monitoring data to further optimize the emission limit of total iron concentration, so that when the total iron concentration emission meets the standard, the pH and chromaticity of the water body at the mine outlet also meet the standard, as follows:

[0099] Taking the pyrite in Example 1 as the research object, the water quality monitoring of the mine outlet in the study area is carried out, and the monitoring covers each water period as much as possible. Under limited conditions, the monitoring of the flood season and the flat water season is carried out as much as possible, and factors such as rainfall and non-rainfall need to be considered. Sampling is carried out according to the monitoring plan, and the existing unmanaged water quality samples of the outlet are analyzed to obtain supplementary monitoring data of the mine outlet. In this embodiment, the monitoring time is from August to December 2023, covering the three periods of flood, flat and dry, of which September is the rainfall period monitoring.

[0100] This embodiment adds the water outlet monitoring data from August to December to step (3) in embodiment 1.

[0101] A comparative analysis was conducted to determine the relationship between the pH and chromaticity of the water at the mine outlet and the concentration of trivalent iron ions and total iron. The results are as follows Figure 5 and Figure 6 shown.

[0102] Depend on Figure 5 As a result, according to the total iron concentration of the water quality at the outlet ≤130mg / L, the pH of the water body at the mine outlet is between 3 and 9, and the pH of some of the water bodies is <6. Although the total iron concentration meets the discharge standard, the pH of the water quality at the outlet is partially substandard. We found that when the pH value of the water body at the mine outlet is controlled in the range of 6-9, the total iron concentration of most of the water bodies at the outlet is stable within 50mg / L, which meets the above-mentioned total iron concentration limit requirements of Example 1 and the water quality pH also meets the discharge requirements.

[0103] Depend on Figure 6 The results show that according to the outlet water quality chromaticity ≤50, the pH of the water body at the mine outlet is between 3 and 9. Although the water quality chromaticity meets the standard, there are some water quality pH <6, which does not meet the discharge requirements. We found that when the pH value of the mine outlet water body is controlled in the range of 6-9, the chromaticity of most outlets can be stabilized within 50 degrees. It is speculated that the total iron concentration at the outlet is stably controlled in an appropriate range, which can simultaneously meet the discharge standards of the water quality pH, chromaticity and total iron concentration at the outlet.

[0104] The pH and total iron concentration in the supplementary monitoring data were further fitted with polynomials, and the critical values ​​of total iron concentration within the 90% and 95% confidence intervals when the pH was controlled between 6 and 9 were calculated. Figure 7 and Figure 8 shown.

[0105] Depend on Figure 7 and Figure 8 It can be seen that the critical values ​​of total iron concentration within the 90% and 95% confidence intervals are 62 mg / L and 57.5 mg / L, respectively, and the average of the two is 60 mg / L. It can be seen that when the pH value of the water body at the mine outlet is controlled between 6 and 9, the total iron concentration can basically be controlled below 60 mg / L, and the water body chromaticity is within 50. Taking all factors into consideration, the minimum total iron concentration value of 60 mg / L is used as the upper limit of the total iron concentration discharge when the water body at the pyrite outlet is discharged; preferably, the minimum trivalent iron ion concentration value is used as the lower limit of the total iron concentration discharge (that is, 30 mg / L).

[0106] In summary, the pH, chromaticity and total iron concentration were selected as the prevention and control indicators for the water outlet of the pyrite mine cave in the historical non-water source area of ​​the study area; the total iron concentration of the water at the outlet was controlled at 30-60 mg / L, the pH of the water was between 6 and 9, and the chromaticity was below 50, all three meeting the discharge requirements.

[0107] This embodiment starts from the actual water outlet of the pyrite mine cave in the historical non-water source area to solve the problems of yellow color, acidity and iron pollution index of the "sulfur water" at the outlet. Through experiments, supplementary monitoring, statistical analysis, etc., the relevance and controllability of the main prevention and control indicators are determined, and the control requirements of the prevention and control indicators are finally determined. After analysis, the upper limit of the total iron concentration of the water body at the outlet of the pyrite mine cave in the historical non-water source area karst mining area is 60mg / L for treatment, which can simultaneously meet the discharge requirements of the water body pH of the outlet water body between 6 and 9 and chroma ≤50.

[0108] It can be seen that the control standard of acidic wastewater at the outlet of the pyrite mine determined by this method can be used to control the total iron concentration at the outlet while meeting the discharge standard. It can also meet the discharge standard requirements of water quality pH and chromaticity; that is, after the treatment is carried out according to the upper limit of the total iron concentration in the acidic wastewater at the outlet of the pyrite mine, which is 60mg / L, the chromaticity of the water body meets ≤50 and the pH is 6-9, and it can be directly discharged into the river after treatment; preferably, the control is carried out according to 30mg / L≤total iron concentration≤60mg / L. It can be seen that for the historical karst mine caves (pyrite mines) in the southwest area where pollution control is difficult to implement, the prevention and control according to this method can not only achieve the purpose of pollution control, but also significantly reduce the capital investment in pollution control, and avoid the high cost of treatment caused by excessive pollution control.

[0109] It should be noted that although there is mutual influence between pH, chromaticity and total iron concentration, such as when adjusting pH, its corresponding chromaticity and total iron concentration will also change, and the total iron concentration may also be reduced while adjusting pH value, but if only considering controlling the pH of the water body at 6 to 9, its corresponding total iron concentration may not meet the standard (such as controlled below 60 mg / L), and the chromaticity may not meet the standard (such as controlled below 50). Therefore, the three need to be comprehensively considered for control. In fact, according to the method provided by the present invention for different historical pyrite mining areas, the control requirements of the corresponding total iron concentration are first determined, and then treated according to the control requirements, which can be conducive to the reasonable and effective prevention and control of acidic wastewater in historical non-water source mining areas.

[0110] Comparative Example 1

[0111] According to the pollutant emission standard for mining areas in production, "Iron Ore Mining and Dressing Industry Pollutant Emission Standard" (GB28661-2012), the direct emission concentration limit of iron is 5 mg / L. It can be seen that compared with the treatment according to the total iron emission concentration limit in Example 1 and Example 2, the treatment according to the iron pollutant emission standard in the mining area will obviously greatly increase the treatment cost of the historical mining area, which is easy to cause the transitional treatment of the mining area.

[0112] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preventing and controlling acid wastewater pollution in historical mining areas, characterized in that: The mining area is pyrite, which specifically includes the following steps: (1) Determine the total iron discharge concentration limit of the water body at the mine outlet: 1-1: Take the untreated acid wastewater from the mining area and dilute it, measure the chromaticity and total iron concentration of the water samples at different dilution times, and analyze the linear relationship between the total iron concentration y1 and the chromaticity x, which is y1=k1*x+b1; According to the chromaticity A1 corresponding to when the water color at the outlet of the mining area just turns non-yellow, calculate the total iron concentration B1 corresponding to when the water color is A1; 1-2: Take the untreated acidic wastewater from the mining area, add alkali to adjust its pH, measure the chromaticity and total iron concentration of the water sample with a pH range of 6 to 9, take the maximum value, record it as chromaticity A2 and total iron concentration B2 respectively; determine the total iron discharge concentration limit according to the following method: The smaller integer value of total iron concentration B1 and B2 is used as the upper limit of total iron concentration in the water body at the mine outlet; (2) treating the acidic wastewater from the mining area according to the total iron concentration emission limit determined in step (1) so that its total iron concentration meets the emission limit requirements, and at the same time, the pH value of the water body is 6 to 9 and the color of the water body at the outlet is not yellow.

2. The method for preventing and controlling acid wastewater pollution in historical mining areas as claimed in claim 1, characterized in that: The step 1-2 further includes supplementing the in-situ monitoring of the water quality of the mine outlet, pH and total iron concentration, using a polynomial fitting analysis to determine the mean of the critical values ​​of total iron concentration within the 90% and 95% confidence intervals when the pH is between 6 and 9, recorded as B3; The minimum concentration value among the total iron concentrations B1, B2 and B3 obtained is taken as the upper limit of the total iron concentration discharged from the water body at the mine outlet.

3. The method for preventing and controlling acid wastewater pollution in historical mining areas as claimed in claim 2, characterized in that: The in-situ monitoring includes monitoring the pH and total iron concentration of the water quality at the mine outlet during the three phases of flood, normal and drought.

4. The method for preventing and controlling acid wastewater pollution in historical mining areas according to any one of claims 1 to 3, characterized in that: In the step 1-1, after the untreated acidic wastewater in the mining area is diluted, the concentration of trivalent iron ions is also measured, and the linear relationship between the concentration of trivalent iron ions y2 and the chromaticity x is obtained by analysis: y2=k2*x+b2; and the corresponding trivalent iron ion concentration C1 when the chromaticity of the water body is A1 is calculated; In step 1-2, after adjusting the pH, the concentration of trivalent iron ions in the water sample corresponding to a pH range of 6 to 9 is measured, and the maximum value is taken, which is recorded as C2; The smaller value of the trivalent iron ion concentrations C1 and C2 is taken as the lower limit of the total iron concentration in the water body at the mine outlet.

5. The method for preventing and controlling acid wastewater pollution in historical mining areas as claimed in claim 4, characterized in that: The pyrite is pyrite from the non-water source area left over from history.

6. The method for preventing and controlling acid wastewater pollution in historical mining areas as claimed in claim 5, characterized in that: The pyrite is a karst type mine.

7. The method for preventing and controlling acid wastewater pollution in historical mining areas as claimed in claim 6, characterized in that: The raw water at the pyrite outlet has a pH value of less than 4 and a total iron concentration of more than 300 mg / L. The upper limit of the total iron concentration emission is determined to be 60 mg / L. The water is treated according to the total iron concentration emission limit so that the water quality at the outlet meets the emission requirements of a pH value of 6 to 9 and a non-yellow color.

8. A historical pyrite mining area acid wastewater pollution prevention and control assessment system, characterized in that: It includes a data acquisition module, a data analysis and judgment module, and a result display module; The data acquisition module is used to obtain the pH, chromaticity and total iron concentration of the water body at the outlet after the acid wastewater of the historical pyrite mine cave is treated, and submit it to the data analysis and judgment module; The data analysis and judgment module is used to compare the obtained pH, chromaticity and total iron concentration with the corresponding preset emission limits to determine whether the acid wastewater pollution prevention and control in the pyrite mine area meets the standards. The specific judgment is as follows: If the pH value, total iron concentration and chromaticity of the water at the outlet meet the corresponding preset emission limits, it is judged that the pollution prevention and control of acid wastewater in the historical pyrite mining area has met the standards; If one or more indicators of the pH value, total iron concentration, and chromaticity of the water body at the outlet do not meet the corresponding preset emission limits, it is judged that the anti-pollution treatment of acid wastewater in the historical pyrite mining area does not meet the standards; and the judgment result is submitted to the result display module; The preset emission limit is determined according to the method according to any one of claims 1 to 4; The result display module displays whether the anti-pollution treatment of acid wastewater in the mining area meets the standard or does not meet the standard according to the received judgment result.

9. The historical pyrite mine acid wastewater pollution prevention and control assessment system as claimed in claim 8, characterized in that: The raw water from the historical pyrite mine outlet has a pH value of less than 4 and a total iron concentration of more than 300 mg / L. The preset pH emission limit is 6-9, the preset upper limit of the total iron concentration emission is 60 mg / L, and the preset chromaticity emission limit is 50.

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