Low-cost treatment method for high-manganese-content difficult-to-treat mine acid wastewater

Abstract

The invention discloses a low-cost treatment method for high-manganese-content difficult-to-treat mine acid wastewater, which is implemented by adopting a graded neutralization treatment process and comprises the following steps: regulating the pH value of the wastewater to be 5-6 in a first-stage neutralization reaction, feeding the wastewater into a first-stage flocculation reaction tank, and agglomerating hydroxide particles to form large flocculate; feeding the wastewater subjected to the primary flocculation reaction into a primary sedimentation tank to precipitate sludge in the wastewater, feeding discharged supernate into a secondary neutralization tank, feeding the discharged supernate into a secondary flocculation reaction tank, feeding the wastewater subjected to the secondary flocculation reaction into a secondary sedimentation tank to precipitate sludge in the wastewater, and taking supernate of the secondary sedimentation tank as qualified effluent; the method disclosed by the invention is simple in process, high in heavy metal removal rate, relatively small in agent use amount and small in sludge generation amount, can overcome the defects that manganese in the effluent of the mine acid wastewater is difficult to reach the standard, the effluent needs acid callback, the agent use amount is large and the sludge generation amount is large, and can efficiently ensure that the effluent of a mine acid wastewater treatment facility stably reaches the standard in an energy-saving manner.

Description

Technical Field

[0001] The invention belongs to the technical field of acid mine wastewater treatment, and specifically relates to a method for treating acid mine wastewater with high manganese content, and is particularly suitable for treating acid mine wastewater with high manganese content and difficult to treat, wherein the Mn content in the acid mine wastewater is 40 to 120 mg / L. Background Art

[0002] my country is one of the countries in the world with vast territory, rich mineral resources, many types of mineral deposits and a complete range of mineral species. However, while developing mineral resources, it also brings about the problem of mine wastewater pollution, among which acidic wastewater is the most serious. The discharge of acidic wastewater leads to water acidification, and acidic wastewater containing heavy metal ions will poison the soil, causing vegetation to wither and die. At present, China produces up to 11 billion tons of acidic mine wastewater every year due to mineral development or tailings dumping. The formation of acidic mine wastewater not only has a serious impact on the surrounding environment and is highly toxic, but also limits or reduces biodiversity and causes serious pollution to the local ecological environment.

[0003] Lime neutralization is the mainstream technology for treating acid mine wastewater. Its principle is to increase the pH value of acid wastewater by adding lime and utilizing acid-base neutralization reaction (if the manganese content in the wastewater is high, the pH value generally needs to be adjusted to above 10.0), while at the same time making heavy metal ions react with OH - Reacts to form insoluble hydroxide precipitates, some SO4 2- With Ca 2+ However, due to the variety of heavy metals in acid mine drainage, some heavy metals (such as Al 3+ 、Zn 2+ , Pb 2+ Alkali reverse dissolution will occur, and Fe(OH)3 / CaSO4 flocculent precipitation will coat the lime, resulting in the traditional lime neutralization method having the disadvantages of low lime neutralization efficiency, large lime consumption, low manganese removal efficiency, large amount of toxic neutralization slag produced, and the need for acid adjustment of the effluent.

[0004] In addition, since the outer electron configuration of manganese is 3d 5 4s 0 The d orbital is half-filled and has high stability. The removal of manganese in polymetallic pollution is difficult and needs to be solved urgently. Summary of the invention

[0005] The purpose of the present invention is to provide a low-cost treatment method for difficult-to-treat acid mine wastewater with high manganese content, in view of the problems existing in the lime neutralization method, such as low neutralization efficiency, large lime consumption, low manganese removal efficiency, large amount of toxic neutralization slag produced, acid adjustment required for effluent, high treatment cost and great difficulty in removing manganese in multi-metal pollution.

[0006] To achieve the above-mentioned purpose of the present invention, a low-cost treatment method for high-manganese-containing difficult-to-treat acid mine wastewater of the present invention is implemented by the following technical scheme:

[0007] S1 primary neutralization reaction: add alkaline chemicals to the acidic mine wastewater in the primary neutralization tank and stir evenly to adjust the pH value of the wastewater to between 5 and 6. 3+ 、Al 3+ Hydroxide begins to form; the Mn content in the acid mine wastewater is in the range of 40 to 120 mg / L;

[0008] S2 primary flocculation reaction: the wastewater after neutralization in step S1 is fed into the primary flocculation reaction tank, and flocculants are added to the primary flocculation reaction tank and stirred evenly. The hydroxide particles formed in step S1 in the wastewater are aggregated to form large floccules through the bridging or charge neutralization effect of the flocculants, thereby accelerating the sedimentation and clarification of the suspension;

[0009] S3 primary sedimentation: The wastewater from the flocculation reaction in step S2 is fed into the primary sedimentation tank to precipitate the sludge in the wastewater. The bottom sludge in the primary sedimentation tank is regularly pumped out and collected in the sludge thickening tank for treatment. The supernatant of the primary sedimentation tank enters the next stage of reaction;

[0010] S4 Secondary neutralization reaction: The supernatant discharged from step S3 is fed into the secondary neutralization tank, and an alkaline chemical agent is added to the inlet of the secondary neutralization tank through a dosing pump and stirred evenly, and the pH value is adjusted to between 8.5 and 9. The heavy metal Cu in the wastewater after the pH value is adjusted 2+ 、Zn 2+ Cr 3+ , Fe 2+ 、Cd 2+ , Mn 2+ Hydroxide formation begins;

[0011] S5 Secondary flocculation reaction: The wastewater after neutralization in step S4 is fed into the secondary flocculation reaction tank, and flocculants are added to the inlet of the secondary flocculation reaction tank through a dosing pump and stirred evenly. The hydroxide particles formed in step S4 coagulate to form large floccules through the bridging or charge neutralization effect of the flocculant, thereby accelerating the sedimentation and clarification of the suspension;

[0012] S6 Secondary sedimentation: The wastewater after the flocculation reaction in step S5 is fed into the secondary sedimentation tank to precipitate the sludge in the wastewater. The supernatant of the secondary sedimentation tank is the qualified effluent.

[0013] Research shows that the sedimentation in steps S3 and S6 can be carried out by natural sedimentation / inclined tube / inclined plate and other methods to precipitate the sludge in the wastewater, but it is better to use a non-directional upflow inclined tube sedimentation tank for both the primary and secondary sedimentation tanks.

[0014] Preferably, the alkaline chemical agent is slaked lime, lime milk or sodium hydroxide; and the flocculant is anionic polyacrylamide.

[0015] Preferably, in step S1, the residence time of the acid mine wastewater in the primary neutralization tank is 13 to 18 minutes; in step S2, the residence time of the wastewater in the primary flocculation reaction tank is 13 to 18 minutes; in step S3, the residence time of the wastewater in the primary sedimentation tank is 1.3 to 1.8 hours; in step S4, the residence time of the supernatant to which the alkaline chemical agent is added and stirred evenly in the secondary neutralization tank is 13 to 18 minutes; in step S5, the residence time of the wastewater in the secondary flocculation reaction tank is 13 to 18 minutes; in step S6, the residence time of the wastewater in the secondary sedimentation tank is 1.3 to 1.8 hours.

[0016] Studies have shown that the amount of alkaline chemicals added to the secondary neutralization tank should be 35% to 45% of the amount added in the primary neutralization tank, with 40% being the optimal amount; the amount of flocculant added to the secondary flocculation reaction tank should be equal to the amount added in the primary flocculation reaction tank.

[0017] The low-cost treatment method of the difficult-to-treat acid mine wastewater with high manganese content of the present invention has the following beneficial effects after adopting the above technical scheme:

[0018] (1) The method of the present invention adopts a staged neutralization, flocculation and sedimentation process, which removes the sludge produced in the previous stage before continuing the neutralization reaction in the next stage, thereby avoiding the reverse dissolution of heavy metal alkali caused by the continued increase in pH value, thereby lowering the neutralization endpoint pH value and reducing the consumption of alkaline agents.

[0019] (2) The method of the present invention adopts a staged neutralization, flocculation and precipitation process, which can remove a large amount of other coexisting metal ions that affect the precipitation of manganese ions during the first stage of neutralization, flocculation and precipitation, which is beneficial to the effect of manganese removal by the second stage of neutralization, flocculation and precipitation. Therefore, the water treatment facility using the process of the present invention is particularly suitable for the treatment of permanganate acid mine wastewater.

[0020] (3) The process endpoint pH value adopted by the method of the present invention is relatively low, which meets the pH value requirements (6 to 9) in the emission standards, and does not require acid adjustment, thereby reducing the reagent consumption of the neutralization process.

[0021] (4) Since the alkaline agent in the method of the present invention has high efficiency and small input amount of alkaline agent, compared with the traditional lime neutralization process, the amount of sludge generated by the water treatment facilities using the process of the present invention is smaller, which reduces the cost of toxic sludge disposal, thereby reducing the operating cost of mine acid wastewater.

[0022] (6) Experimental studies have shown that, compared with a one-stage neutralization, flocculation and sedimentation process, the method of the present invention adopts a two-stage neutralization, flocculation and sedimentation process, which can reduce the consumption of alkaline reagents by about 50%, and can save the addition of acid to the acid adjustment tank. The average contents of Mn, Cu, Fe and Zn in the final effluent are reduced by 60%, 50%, 70% and 90% respectively, the amount of sludge is reduced by more than 35%, and the total cost of reagents and sludge disposal is reduced by more than 45%, achieving unexpected technical and economic effects.

[0023] (7) The method of the present invention is used to treat acid mine wastewater with a pH of 2.65 to 3.88, a Mn content of 60 to 90 mg / L, a Cu content of 10 to 20 mg / L, a Fe content of 0.8 to 90 mg / L, and a Zn content of 1 to 3 mg / L, and the final effluent water quality reaches a pH of 7 to 9, a Mn content of 0.08 to 1.2 mg / L, a Cu content of 0.02 to 0.05 mg / L, a Fe content of 0.04 to 0.2 mg / L, and a Zn content of 0.02 to 0.08 mg / L. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a principle process flow chart of a low-cost treatment method for difficult-to-treat acid mine wastewater with high manganese content.

[0025] Figure 2 The present invention is a process flow chart for treating acid mine wastewater with high manganese content and difficult to treat using the method of the present invention.

[0026] Figure 3 This is a process flow chart for treating permanganate acid mine wastewater using traditional lime neutralization treatment method. DETAILED DESCRIPTION

[0027] To better describe the present invention, a low-cost treatment method for difficult-to-treat acid mine wastewater with high manganese content of the present invention is further described in detail below in conjunction with the accompanying drawings and examples.

[0028] Example

[0029] Example A certain mine acid wastewater is treated. Figure 2 , Figure 1 , the present invention is further described. Figure 2 The process flow chart of the invention for treating acid mine wastewater with high manganese content and difficult to treat is shown in FIG. Figure 1 The present invention provides a low-cost method for treating acid mine wastewater with high manganese content and difficult to treat, which is implemented by the following steps and facilities:

[0030] (1) Inlet pool: used to collect and homogenize acid mine wastewater. The water quality of the wastewater is shown in Table 1. The acid mine wastewater in the inlet pool is pumped to the primary neutralization tank by a water pump. The pumping flow rate is about 0.4m 3 / h.

[0031] (2) Primary neutralization tank: lime milk with a mass concentration of 10% is added to the inlet of the primary neutralization tank through a dosing pump to raise the pH value of the wastewater to about 5. In this example, the dosing amount is set to about 4L / h. The residence time of the neutralization tank is 15 minutes. A stirrer is set on the top with a stirring rate of about 400r / min. The wastewater after lime neutralization flows into the primary flocculation reaction tank by gravity.

[0032] (3) Primary flocculation reaction tank: PAM solution with a mass concentration of 0.1% is added to the inlet of the primary flocculation reaction tank through a dosing pump. In this example, the dosage is set to about 0.4L / h. The residence time of the primary flocculation reaction tank is 15 minutes. A stirrer is set on the top with a stirring rate of about 200r / min. The wastewater after flocculation reaction flows into the primary sedimentation tank by gravity.

[0033] (4) Primary sedimentation tank: The primary sedimentation tank is a heterogeneous upflow inclined tube sedimentation tank with a retention time of 1.5 hours. The supernatant of the primary sedimentation tank flows into the next stage reaction by gravity, and the sludge at the bottom is regularly pumped out and collected in the sludge thickening tank.

[0034] (5) Secondary neutralization tank: lime milk with a mass concentration of 10% is added to the inlet of the secondary neutralization tank through a dosing pump to raise the pH value of the wastewater to about 9. In this embodiment, the dosage is set to about 1.6L / h. The residence time of the secondary neutralization tank is 15 minutes, and a stirrer is set on the top with a stirring rate of about 400r / min. The wastewater after lime neutralization flows into the secondary flocculation reaction tank by gravity.

[0035] (6) Secondary flocculation reaction tank: PAM solution with a mass concentration of 0.1% is added to the inlet of the secondary flocculation reaction tank through a dosing pump. In this example, the dosage is set to about 0.4L / h. The residence time of the secondary flocculation reaction tank is 15 minutes. A stirrer is set on the top with a stirring rate of about 200r / min. The wastewater after flocculation reaction flows into the secondary sedimentation tank by gravity.

[0036] (7) Secondary sedimentation tank: The secondary sedimentation tank is a heterogeneous upflow inclined tube sedimentation tank with a retention time of 1.5 hours. The supernatant in the secondary sedimentation tank flows into the effluent tank by gravity, and the sludge at the bottom is regularly pumped out and collected in the sludge thickening tank.

[0037] (8) Outlet pool: used to collect the effluent after secondary treatment. The quality of the treated water is shown in Table 1.

[0038] Ancillary facilities used in the embodiment:

[0039] ① Lime milk mixing tank and dosing pump: used to store the prepared lime milk solution (with a stirrer inside to ensure that the lime milk solution is uniform and does not settle), and pump the lime milk to the neutralization tank at a certain flow rate.

[0040] ②PAM stirring tank and dosing pump: used to store the configured PAM solution (with a stirrer inside to ensure that the PAM solution is uniform and does not settle), and pump the PAM solution to the neutralization tank at a certain flow rate.

[0041] ③ Sludge thickening tank and plate-frame filter press: used to collect and filter the sludge in the primary and secondary sedimentation tanks. The mud cake after filtration is outsourced to a qualified enterprise for disposal, and the filtrate is returned to the inlet tank.

[0042] Comparative Example

[0043] In order to better compare the treatment effects, the traditional lime neutralization method was used as a comparative example to treat the acidic mine wastewater. The treatment steps of the comparative example are as follows:

[0044] (1) Regulating tank: used to collect and homogenize acid mine wastewater. The water quality of the wastewater is shown in Table 1. The acid mine wastewater in the inlet tank is pumped to the primary neutralization tank by a water pump. The pumping flow rate is about 0.4m 3 / h.

[0045] (2) Neutralization tank: 10% lime milk is added to the inlet of the neutralization tank through a dosing pump to raise the pH value of the wastewater to 10-11. In this example, the dosing amount is set to about 11.2L / h. The residence time of the neutralization tank is 15 minutes. A stirrer is set on the top with a stirring rate of about 400r / min. The wastewater after lime neutralization flows into the flocculation reaction tank by gravity.

[0046] (3) Flocculation reaction tank: PAM solution with a mass concentration of 0.1% is added to the inlet of the flocculation reaction tank through a dosing pump. In this example, the dosage is set to about 0.8L / h. The residence time of the flocculation reaction tank is 15 minutes. A stirrer is set on the top with a stirring rate of about 200r / min. The wastewater after flocculation reaction flows into the sedimentation tank by gravity.

[0047] (4) Sedimentation tank: The sedimentation tank is a heterogeneous upflow inclined tube sedimentation tank with a retention time of 1.5 hours. The supernatant in the sedimentation tank flows into the next stage of reaction by gravity, and the sludge at the bottom is regularly pumped out and collected in the sludge thickening tank.

[0048] (5) Acid adjustment tank: Oxalic acid with a mass concentration of 30% is added to the inlet of the acid adjustment tank through a dosing pump. In this example, the dosage is set to about 0.02L / h. The residence time of the acid adjustment tank is 15 minutes. A stirrer is set on the top with a stirring rate of about 400r / min. The wastewater after oxalic acid neutralization flows into the effluent tank by gravity.

[0049] (6) Outlet pool: used to collect treated effluent. The quality of the treated water is shown in Table 1.

[0050] Additional facilities:

[0051] ① Lime milk mixing tank and dosing pump: used to store the prepared lime milk solution (with a stirrer inside to ensure that the lime milk solution is uniform and does not settle), and pump the lime milk to the neutralization tank at a certain flow rate.

[0052] ②PAM stirring tank and dosing pump: used to store the configured PAM solution (with a stirrer inside to ensure that the PAM solution is uniform and does not settle), and pump the PAM solution to the neutralization tank at a certain flow rate.

[0053] ③ Oxalic acid mixing tank and dosing tank: used to store the prepared oxalic acid solution (with a stirrer inside to ensure that the oxalic acid solution is uniform and does not precipitate), and pump the oxalic acid solution to the neutralization tank at a certain flow rate.

[0054] ④ Sludge thickening tank and plate-frame filter press: used to collect and filter the sludge in the sedimentation tank. The mud cake after filtration is outsourced to a qualified enterprise for disposal, and the filtrate is returned to the water inlet tank.

[0055] Table 1 Inlet and outlet water quality of the embodiment and the comparative example

[0056]

[0057]

[0058] Table 2: Table of the use of reagents and sludge production in the examples and comparative examples

[0059]

[0060] Table 3 Unit price list of chemicals and sludge disposal costs

[0061]

[0062] Table 4 Statistics of reagents and sludge disposal costs for the examples and comparative examples

[0063]

[0064] The above test results show that compared with the comparative example and other common mine acid wastewater treatment processes, the graded neutralization treatment of high manganese mine acid wastewater provided by the present invention has obvious advantages:

[0065] (1) The method of the present invention can avoid the phenomenon of heavy metal alkali reverse dissolution caused by the continuous increase of pH value during the neutralization reaction, thereby lowering the neutralization endpoint pH value and reducing the consumption of alkaline reagents.

[0066] (2) Since the method of the present invention removes a large amount of other coexisting metal ions that affect the precipitation of manganese ions during the first stage of neutralization flocculation precipitation, it is beneficial to the effect of manganese removal by the second stage of neutralization flocculation. Therefore, the water treatment facility using the process of the present invention is particularly suitable for the treatment of permanganate acid mine wastewater.

[0067] (3) The process endpoint pH value adopted by the method of the present invention is relatively low, which meets the pH value requirements (6 to 9) in the emission standards, and does not require acid adjustment, thereby reducing the reagent consumption of the neutralization process.

[0068] (4) Since the alkaline agent in the method of the present invention has high efficiency and small input amount of alkaline agent, compared with the traditional lime neutralization process, the amount of sludge generated by the water treatment facilities using the process of the present invention is smaller, which reduces the cost of toxic sludge disposal, thereby reducing the operating cost of mine acid wastewater.

[0069] The method of the present invention adopts a staged neutralization, flocculation and precipitation process, which is a revolution in the traditional one-stage neutralization, flocculation and precipitation process, and ultimately achieves unexpected technical and economic effects.

[0070] The above is only a preferred specific implementation of the present invention, but it is obvious that the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work inspired by them, and any technicians familiar with the technical field within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, are equivalently replaced or changed, and should be covered within the protection scope of the present invention.

Claims

1. A low-cost treatment method for difficult-to-treat acid mine wastewater with high manganese content, characterized in that Adopt graded neutralization treatment process to implement: S1 primary neutralization reaction: add alkaline chemicals to the acidic mine wastewater in the primary neutralization tank and stir evenly to adjust the pH value of the wastewater to between 5 and 6. 3+ 、Al 3+ Hydroxide begins to form; the Mn content in the acid mine wastewater is in the range of 40 to 120 mg / L; S2 primary flocculation reaction: the wastewater after neutralization in step S1 is fed into the primary flocculation reaction tank, and flocculants are added to the primary flocculation reaction tank and stirred evenly. The hydroxide particles formed in step S1 in the wastewater are aggregated to form large floccules through the bridging or charge neutralization effect of the flocculants, thereby accelerating the sedimentation and clarification of the suspension; S3 primary sedimentation: The wastewater from the flocculation reaction in step S2 is fed into the primary sedimentation tank to precipitate the sludge in the wastewater. The bottom sludge in the primary sedimentation tank is regularly pumped out and collected in the sludge thickening tank for treatment. The supernatant of the primary sedimentation tank enters the next stage of reaction; S4 Secondary neutralization reaction: The supernatant discharged from step S3 is fed into the secondary neutralization tank, and an alkaline chemical agent is added to the inlet of the secondary neutralization tank through a dosing pump and stirred evenly, and the pH value is adjusted to between 8.5 and 9. The heavy metal Cu in the wastewater after the pH value is adjusted 2+ 、Zn 2+ Cr 3+ , Fe 2+ 、Cd 2+ , Mn 2+ Hydroxide formation begins; S5 Secondary flocculation reaction: The wastewater after neutralization in step S4 is fed into the secondary flocculation reaction tank, and flocculants are added to the inlet of the secondary flocculation reaction tank through a dosing pump and stirred evenly. The hydroxide particles formed in step S4 coagulate to form large floccules through the bridging or charge neutralization effect of the flocculant, thereby accelerating the sedimentation and clarification of the suspension; S6 Secondary sedimentation: The wastewater after the flocculation reaction in step S5 is fed into the secondary sedimentation tank to precipitate the sludge in the wastewater. The supernatant of the secondary sedimentation tank is the qualified effluent.

2. A low-cost treatment method for high-manganese-containing difficult-to-treat acid mine wastewater as claimed in claim 1, characterized in that: The primary sedimentation tank and the secondary sedimentation tank both adopt heterogeneous upflow inclined tube sedimentation tanks.

3. A low-cost treatment method for high-manganese-containing difficult-to-treat acid mine wastewater according to claim 1, characterized in that: The alkaline chemical agent is slaked lime, lime milk or sodium hydroxide.

4. A low-cost treatment method for high-manganese-containing difficult-to-treat acid mine wastewater as claimed in claim 1, characterized in that: The flocculant is anionic polyacrylamide.

5. A low-cost method for treating acid mine wastewater with high manganese content and difficult to treat as claimed in claim 1, 2, 3 or 4, characterized in that: In step S1, the residence time of the acid mine wastewater in the primary neutralization tank is 13-18 minutes.

6. A low-cost method for treating acid mine wastewater with high manganese content and difficult to treat as claimed in claim 1, 2, 3 or 4, characterized in that: In step S2, the residence time of the wastewater in the primary flocculation reaction tank is 13 to 18 minutes.

7. A low-cost method for treating acid mine wastewater with high manganese content and difficult to treat as claimed in claim 1, 2, 3 or 4, characterized in that: In step S3, the residence time of the wastewater in the primary sedimentation tank is 1.3 to 1.8 hours.

8. A low-cost method for treating acid mine wastewater with high manganese content and difficult to treat as claimed in claim 1, 2, 3 or 4, characterized in that: In step S4, the supernatant liquid after adding the alkaline chemical agent and stirring evenly stays in the secondary neutralization tank for 13 to 18 minutes.

9. A low-cost method for treating acid mine wastewater with high manganese content and difficult to treat according to claim 1, 2, 3 or 4, characterized in that: In step S5, the residence time of the wastewater in the secondary flocculation reaction tank is 13 to 18 minutes.

10. A low-cost method for treating acid mine wastewater with high manganese content and difficult to treat according to claim 1, 2, 3 or 4, characterized in that: In step S6, the residence time of the wastewater in the secondary sedimentation tank is 1.3 to 1.8 hours.

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