A method for removing manganese from leachate of general industrial solid waste landfill

Abstract

The present invention relates to a method for removing manganese from leachate of a general industrial solid waste landfill, belonging to the technical field of wastewater treatment, and comprising the following steps: Step S1, primary coagulation and sedimentation: using a pH adjusting agent to adjust the pH of the discharged wastewater to 8-10, the reaction stirring speed is 50-120 rpm, the reaction time is 5-15 minutes, a modified polymer anionic flocculant is added to the wastewater after alkali adjustment, the flocculation reaction time is 5-10 minutes, the stirring speed is 20-60 rpm, after the flocculation reaction, the wastewater is allowed to stand to allow the suspended matter to settle, a first solid-liquid sedimentation separation is performed, and the primary coagulation and sedimentation supernatant is taken out. The coagulation and sedimentation are effectively combined with oxidation, and through the primary coagulation and sedimentation, the oxidation reaction and the secondary coagulation and sedimentation, the pH adjusting agent, the modified polymer anionic flocculant and the ferrous sulfate solution are used in combination to achieve the effect of effectively treating the pollutant manganese, so as to meet the Class III indicator of the "Groundwater Quality Standard" manganese content ≤ 0.10 mg / L.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a method for removing manganese from leachate of a general industrial solid waste landfill. Background Art

[0002] Unusable industrial solid waste must be landfilled. The water quality of landfill leachate varies with the type of landfilled waste. The leachate from industrial solid waste landfills may have high concentrations of some heavy metals and sulfates.

[0003] After industrial solid waste is landfilled, under the combined effects of anoxic, anaerobic, rainfall, groundwater and other conditions, the original cement will partially dissolve and react, resulting in an acidic pH value in the landfill leachate and a high content of reducing metal pollutants. The manganese concentration in the leachate of some general industrial solid waste landfills can reach 5 mg / L. Generally, industrial solid waste landfills are located in remote mountainous areas, with surrounding mountains and forests and farmland downstream. There are few drainage facilities that can receive the treated leachate, resulting in obstructed drainage of the landfill leachate. Therefore, the leachate of some landfills refers to the Class III indicators of the "Groundwater Quality Standard" as the basis for pollution judgment;

[0004] The heavy metal treatment technology for leachate from general industrial solid waste landfills is mature, but the reducing pollutant manganese in the leachate from general industrial solid waste landfills is mostly Mn 2+ The manganese exists in the form of , resulting in a low treatment efficiency of manganese in leachate. At present, the common methods for removing manganese from wastewater are mainly chemical coagulation and sedimentation, aeration oxidation, ferrite method, adsorption method, oxidation-electroflocculation method, etc. or a combination of several methods. The manganese concentration in the treated effluent is basically 0.8-1.5 mg / L, which is difficult to meet the Class III indicator of the "Groundwater Quality Standard" manganese content ≤ 0.10 mg / L. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for removing manganese from leachate of a general industrial solid waste landfill in order to solve the above problems.

[0006] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0007] The present invention provides a method for removing manganese from leachate of a general industrial solid waste landfill, comprising the following steps:

[0008] Step S1, primary coagulation and sedimentation: using a pH adjusting agent to adjust the pH of the discharged wastewater to 8-10, the reaction stirring speed is 50-120 rpm, the reaction time is 5-15 minutes, and a modified polymer anionic flocculant is added to the wastewater after alkali adjustment, the flocculation reaction time is 5-10 minutes, the stirring speed is 20-60 rpm, after the flocculation reaction, the suspended matter is allowed to settle, and the first solid-liquid sedimentation separation is performed, and the primary coagulation precipitation supernatant is taken out;

[0009] The function of primary coagulation and sedimentation is: the alkaline agent pre-precipitates some metal ions (such as copper, zinc, arsenic, etc.) and a small amount of manganese ions, reducing the consumption of subsequent oxidizing agents;

[0010] Step S2, oxidation reaction: adding ferrous sulfate solution to the primary coagulation precipitation supernatant obtained in step S1, with a stirring speed of 50 to 120 rpm, adjusting the pH thereof to 5 to 7, dissolving the ferrous sulfate salt for 30 to 60 minutes, and then adding sodium persulfate solution, controlling the amount of sodium persulfate to 0.4 to 0.6 g / L based on the amount of the primary coagulation precipitation supernatant or controlling the pH of the primary coagulation precipitation supernatant to decrease by 0.5 to 0.3 pH units after oxidation, and the oxidation reaction time to 90 to 150 minutes, to obtain oxidized wastewater;

[0011] Step S3, secondary coagulation and sedimentation: using a pH adjusting agent to adjust the pH of the oxidized wastewater to 8-10, the stirring speed is 50-120 rpm, the reaction time is 5-15 min, and a modified polymer anion flocculant is added to the oxidized wastewater. The flocculation reaction time is 5-10 min and the stirring speed is 20-60 rpm. After the flocculation reaction, the mixture is allowed to stand to allow the suspended matter to settle, and a second solid-liquid sedimentation separation is performed. The secondary coagulation sedimentation supernatant after precipitation is taken out for testing to determine whether the manganese concentration in the wastewater reaches 0.1 mg / L.

[0012] As a further optimization solution of the present invention, in step S1:

[0013] The pH adjusting agent can be compound alkali or lime milk;

[0014] The mass ratio of the discharged wastewater to the pH adjusting agent is 1:0.01-0.1;

[0015] The mass ratio of the alkali-adjusted wastewater to the modified polymer anionic flocculant is 1:0.001;

[0016] The concentration of the modified polymer anionic flocculant is 0.01% to 0.05%, and the molecular weight of the flocculant is 25 million to 27 million.

[0017] As a further optimization solution of the present invention, in step S2:

[0018] The mass ratio of the primary coagulation sedimentation supernatant, ferrous sulfate solution and sodium sulfate solution is: 1: 0.01-0.04: 0.01-0.04;

[0019] The concentration of the ferrous sulfate solution is 10% to 20%;

[0020] The concentration of the sodium sulfate solution is 10% to 15%.

[0021] As a further optimization solution of the present invention, in step S3:

[0022] The mass ratio of oxidized wastewater and modified polymer anionic flocculant was adjusted to 1:0.001;

[0023] The concentration of the modified polymer anionic flocculant is 0.01% to 0.05%, and the molecular weight of the flocculant is 25 million to 27 million.

[0024] As a further optimization scheme of the present invention, the ferrous iron in the oxidation reaction stage is used as an activator of sodium persulfate, and the main reactions involved in the treatment stage are as follows:

[0025] Fe 2+ +S2O8 2- →Fe 3+ +S2O4 2- + SO4 -

[0026] Mn 2+ + SO4 - →MnO2↓+SO4 2-

[0027] Fe2++2OHˉ→Fe(OH)2

[0028] Fe3++3OHˉ→Fe(OH)3

[0029] Fe(OH)3→FeOOH+H2O

[0030] FeOOH+Fe(OH)2→FeOOH·Fe(OH)2

[0031] FeOOH·Fe(OH)2+FeOOH→ FeO·Fe2O3↓+2H2O.

[0032] As a further optimization solution of the present invention, the soluble Mn 2+ Replace Fe 2+ Entering the ferrite lattice, it can be expressed as:

[0033] Fe 2+ +Fe 3+ +Mn2+ +OHˉ→Mn·Mn(OH)2Fe(OH)3+Fe(OH)2→MnO·Fe2O3↓+H2O.

[0034] The beneficial effects of the present invention are: effectively combining coagulation and precipitation with oxidation, through primary coagulation and precipitation, oxidation reaction and secondary coagulation and precipitation, by using a pH adjusting agent, a modified polymer anion flocculant and a ferrous sulfate solution, an effect of effectively treating the pollutant manganese is achieved, so as to meet the Class III indicator manganese content ≤ 0.10 mg / L of the "Groundwater Quality Standard". BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a flow chart for removing manganese from leachate from a general industrial solid waste landfill according to the present invention. DETAILED DESCRIPTION

[0036] The present application is described in further detail below. It is necessary to point out that the following specific implementation methods are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Technicians in this field can make some non-essential improvements and adjustments to the present application based on the above application content.

[0037] 1. Materials

[0038] Unless otherwise specified, the methods used in the present invention are conventional methods known to those skilled in the art, and the reagents and other materials used are commercially available products unless otherwise specified.

[0039] (1) The modified polymer anionic flocculant of the present invention is prepared by modifying sodium polyacrylate flocculant. The specific modification steps are as follows:

[0040] Sodium polyacrylate is irradiated with gamma rays, with the gamma ray radiation intensity controlled at 100,000 becquerels and the irradiation time controlled at 40 hours, to change its molecular structure and properties. Irradiation modification can improve the heat resistance, chemical corrosion resistance and mechanical strength of sodium polyacrylate. Example Example

[0041] The leachate from an industrial solid waste landfill has a manganese concentration of 3.5 mg / L and a pH of 6.8. The following steps are used to treat the water:

[0042] (1) Take 2.0 L of wastewater and put it into a beaker. Turn on the stirrer and maintain the stirring speed at 80 rpm. Add 10% composite alkali emulsion to adjust the pH to 9.5. The reaction time is 15 min.

[0043] (2) Adjust the stirring speed to 50 rpm, add 2.0 mL of 0.05% modified polymer anionic flocculant solution, maintain stirring for 5 min, and then let it stand for 1 h;

[0044] (3) Take 1.6 L of the supernatant after standing in step (2) and transfer it to another beaker. Turn on the stirrer at a stirring speed of 60 rpm, add 20% ferrous sulfate solution to adjust the pH to 5.5, and react for 60 min.

[0045] (4) Add 5.0 mL of 15% sodium persulfate solution to the wastewater after pH adjustment in step (3) and react for 120 minutes;

[0046] (5) Based on step (4), add 10% composite alkali emulsion to the wastewater to adjust the pH to 8.5, adjust the stirring speed to 80 rpm, and react for 10 min;

[0047] (6) Adjust the stirring speed to 50 rpm, add 4.0 mL of a 0.05% modified polymer anionic flocculant solution, maintain stirring for 10 min, and then let the wastewater stand for 1 h to allow sludge sedimentation.

[0048] In this embodiment, the supernatant in step (6) was taken and tested, and the manganese content in the supernatant was 0.085 mg / L. This result has met the manganese requirement of Class III indicators in GB / T 14848-2017 "Groundwater Quality Standard". Example

[0049] The leachate from an industrial solid waste landfill has a manganese concentration of 2.3 mg / L and a pH of 7.6. The following steps are used to treat the water:

[0050] (1) Take 2.0 L of wastewater and put it into a beaker. Turn on the stirrer and maintain the stirring speed at 120 rpm. Add 10% composite alkali emulsion to adjust the pH to 9.5. The reaction time is 10 min.

[0051] (2) Adjust the stirring speed to 60 rpm, add 1.5 mL of 0.05% modified polymer anionic flocculant solution, maintain stirring for 10 min, and then let it stand for 1 h;

[0052] (3) Take 1.8 L of the supernatant after standing in step (2) and transfer it to another beaker. Turn on the stirrer at a stirring speed of 40 rpm, add 20% ferrous sulfate solution to adjust the pH to 6.5, and react for 60 min.

[0053] (4) Add 3.5 mL of 15% sodium persulfate solution to the wastewater after pH adjustment in step (3) and react for 150 min;

[0054] (5) Based on step (4), add 10% composite alkali emulsion to the wastewater to adjust the pH to 9.5, stir at 120 rpm, and react for 15 min;

[0055] (6) In step (5), adjust the stirring speed to 30 rpm, add 2.5 mL of a modified polymer anionic flocculant solution with a concentration of 0.05%, maintain stirring for 10 min, and then let the wastewater stand for 1.5 h to allow sludge sedimentation.

[0056] In this embodiment, the supernatant in step (6) was taken and tested, and the manganese content in the supernatant was 0.065 mg / L. This result has met the manganese requirement of Class III indicators in GB / T 14848-2017 "Groundwater Quality Standard". Example

[0057] The leachate from an industrial solid waste landfill has a manganese concentration of 0.62 mg / L and a pH of 8.2. The following steps are used to treat the water:

[0058] (1) Take 2.0 L of wastewater and put it into a beaker. Turn on the stirrer and maintain the stirring speed at 50 rpm. Add 10% composite alkali emulsion to adjust the pH to 10.0. The reaction time is 5 min.

[0059] (2) Adjust the stirring speed to 20 rpm, add 1.0 mL of 0.05% modified polymer anionic flocculant solution, maintain stirring for 6 min, and then let it stand for 1.5 h;

[0060] (3) Take 1.8 L of the supernatant after standing in step (2) and transfer it to another beaker. Turn on the stirrer at a stirring speed of 30 rpm, add 20% ferrous sulfate solution to adjust the pH to 5.0, and react for 40 min.

[0061] (4) Add 2.0 mL of 15% sodium persulfate solution to the wastewater after pH adjustment in step (3) and react for 90 min;

[0062] (5) Based on step (4), add 10% composite alkali emulsion to the wastewater to adjust the pH to 10, stir at 120 rpm, and react for 10 min;

[0063] (6) In step (5), adjust the stirring speed to 40 rpm, add 2.0 mL of a modified polymer anionic flocculant solution with a concentration of 0.05%, maintain stirring for 5 min, and then let the wastewater stand for 1.5 h to allow sludge sedimentation.

[0064] In this embodiment, the supernatant in step (6) was taken and tested, and the manganese content in the supernatant was 0.040 mg / L. This result has met the manganese requirement of Class III indicators in GB / T 14848-2017 "Groundwater Quality Standard". Example

[0065] The leachate from an industrial solid waste landfill has a manganese concentration of 6.5 mg / L and a pH of 5.3. The following steps are used to treat the water:

[0066] (1) Take 2.0 L of wastewater and put it into a beaker. Turn on the stirrer and maintain the stirring speed at 120 rpm. Add 10% composite alkali emulsion to adjust the pH to 8.0. The reaction time is 15 min.

[0067] (2) Adjust the stirring speed to 20 rpm, add 5.5 mL of 0.05% modified polymer anionic flocculant solution, maintain stirring for 8 min, and then let it stand for 2.0 h;

[0068] (3) Take 1.5 L of the supernatant after standing in step (2) and transfer it to another beaker. Turn on the stirrer at a stirring speed of 40 rpm, add 20% ferrous sulfate solution to adjust the pH to 7.0, and react for 60 min.

[0069] (4) Add 4.0 mL of 15% sodium persulfate solution to the wastewater after pH adjustment in step (3) and react for 90 min;

[0070] (5) Based on step (4), add 10% composite alkali emulsion to the wastewater to adjust the pH to 9.0, adjust the stirring speed to 120 rpm, and react for 10 min;

[0071] (6) Adjust the stirring speed to 30 rpm, add 2.5 mL of 0.05% modified polymer anionic flocculant solution, maintain stirring for 10 min, and then let the wastewater stand for 2 h to allow sludge sedimentation.

[0072] In this embodiment, the supernatant in step (6) was taken and tested, and the manganese content in the supernatant was 0.092 mg / L. This result also meets the manganese requirement of Class III indicators in GB / T 14848-2017 "Groundwater Quality Standard".

[0073] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that variations and improvements are possible without departing from the scope of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A method for removing manganese from leachate of a general industrial solid waste landfill, characterized in that: The following steps are involved: Step S1, primary coagulation and sedimentation: using a pH adjusting agent to adjust the pH of the discharged wastewater to 8-10, the reaction stirring speed is 50-120 rpm, the reaction time is 5-15 minutes, and a modified polymer anionic flocculant is added to the wastewater after alkali adjustment, the flocculation reaction time is 5-10 minutes, the stirring speed is 20-60 rpm, after the flocculation reaction, the suspended matter is allowed to settle, and the first solid-liquid sedimentation separation is performed, and the primary coagulation precipitation supernatant is taken out; Step S2, oxidation reaction: adding ferrous sulfate solution to the primary coagulation precipitation supernatant obtained in step S1, with a stirring speed of 50 to 120 rpm, adjusting the pH thereof to 5 to 7, dissolving ferrous sulfate salt for 30 to 60 minutes, and then adding sodium persulfate solution, controlling the amount of sodium persulfate solution to 0.4 to 0.6 g / L based on the amount of the primary coagulation precipitation supernatant or controlling the pH of the primary coagulation precipitation supernatant to decrease by 0.5 to 0.3 pH units after oxidation, and the oxidation reaction time to 90 to 150 minutes to obtain oxidized wastewater; the mass ratio of the primary coagulation precipitation supernatant, the ferrous sulfate solution, and the sodium sulfate solution is: 1:0.01-0.04:0.01-0.04; Step S3, secondary coagulation and sedimentation: using a pH adjusting agent to adjust the pH of the oxidized wastewater to 8-10, stirring at a speed of 50-120 rpm, and reacting for 5-15 minutes, adding a modified polymer anionic flocculant to the oxidized wastewater, and performing a flocculation reaction for 5-10 minutes at a stirring speed of 20-60 rpm. After the flocculation reaction, the mixture is allowed to stand to allow the suspended matter to settle, and a second solid-liquid sedimentation separation is performed. The supernatant of the secondary coagulation sedimentation after precipitation is taken out for testing to determine whether the manganese concentration in the wastewater reaches 0.1 mg / L; The soluble Mn in the wastewater 2+ Replace Fe 2+ Entering the ferrite lattice, expressed as:Fe 2+ +Fe 3+ +Mn 2+ +OHˉ→Mn·Mn(OH)2Fe(OH)3+Fe(OH)2→MnO·Fe2O3↓+H2O.

2. The method for removing manganese from leachate of a general industrial solid waste landfill according to claim 1, characterized in that: In the step S1: The pH adjusting agent is compound alkali or lime milk; The mass ratio of the discharged wastewater to the pH adjusting agent is 1:0.01-0.1; The mass ratio of the alkali-adjusted wastewater to the modified polymer anionic flocculant is 1:0.001; The concentration of the modified polymer anionic flocculant is 0.01% to 0.05%, and the molecular weight of the flocculant is 25 million to 27 million.

3. The method for removing manganese from leachate of a general industrial solid waste landfill according to claim 1, characterized in that: In the step S2: The concentration of the ferrous sulfate solution is 10% to 20%; The concentration of the sodium sulfate solution is 10% to 15%.

4. The method for removing manganese from leachate of a general industrial solid waste landfill according to claim 1, characterized in that: In the step S3: The mass ratio of oxidized wastewater and modified polymer anionic flocculant was adjusted to 1:0.001; The concentration of the modified polymer anionic flocculant is 0.01% to 0.05%, and the molecular weight of the flocculant is 25 million to 27 million.

5. The method for removing manganese from leachate of a general industrial solid waste landfill according to claim 1, characterized in that: The ferrous iron in the oxidation reaction stage is used as an activator for sodium persulfate, and the main reactions involved in the treatment stage are as follows: Fe 2+ +S2O8 2- →Fe 3+ +S2O4 2- +·SO4 - Mn 2+ +·SO4 - →MnO2↓+SO4 2- Fe 2+ +2OHˉ→Fe(OH)2 Fe3++3OHˉ→Fe(OH)3 Fe(OH)3→FeOOH+H2O FeOOH+Fe(OH)2→FeOOH·Fe(OH)2 FeOOH·Fe(OH)2+FeOOH→ FeO·Fe2O3↓+2H2O.

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