Method for removing manganese in leachate of general industrial solid waste landfill

Abstract

The invention relates to a method for removing manganese in leachate of a general industrial solid waste landfill, which belongs to the technical field of wastewater treatment, and comprises the following steps: S1, primary coagulating sedimentation: regulating the pH value of discharged wastewater to 8-10 by using a pH regulating agent, controlling the reaction stirring speed to 50-120rpm and the reaction time to 5-15min, adding a modified polymer anion flocculant into the wastewater after alkali regulation, and carrying out primary coagulating sedimentation for 5-15min; the flocculation reaction time is 5-10 min, the stirring speed is 20-60 rpm, after the flocculation reaction, standing is conducted, suspended solids are precipitated, first-time solid-liquid settling separation is conducted, and first-time coagulative precipitation supernate is taken out. Coagulating precipitation and oxidation are effectively combined, primary coagulating precipitation, oxidation reaction and secondary coagulating precipitation are used in cooperation with a pH adjusting agent, a modified macromolecule anion flocculating agent and a ferrous sulfate solution, the effect of effectively treating the pollutant manganese is achieved, and the effect is used for meeting the requirement that the content of III-class index manganese in the underground water quality standard is smaller than or equal to 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] With the growth of industrial production capacity, various types of general industrial solid waste are gradually increasing, such as various waste gypsum, metallurgical slag dust, slag, tailings, municipal sludge, etc. Unusable industrial solid waste must be landfilled. The water quality of landfill leachate shows different characteristics depending on the landfill waste. The leachate of industrial solid waste landfill will have high concentrations of some heavy metals and sulfates.

[0003] After industrial solid waste is landfilled, under the combined effects of hypoxia, anaerobic conditions, rainfall, groundwater and other conditions, the original cement will partially dissolve and react, resulting in an acidic pH value of 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. General industrial solid waste landfills are mostly located in remote mountainous areas, surrounded by 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 , which leads to 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 or the 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 "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-mentioned problem.

[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 precipitation: using a pH adjusting agent to adjust the pH of the discharged wastewater to 8-10, the reaction stirring speed is 50-120rpm, the reaction time is 5-15min, and a modified polymer anion flocculant is added to the wastewater after alkali adjustment, the flocculation reaction time is 5-10min, the stirring speed is 20-60rpm, 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 role 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: add ferrous sulfate solution to the primary coagulation precipitation supernatant obtained in step S1, with a stirring speed of 50 to 120 rpm, adjust the pH thereof to 5 to 7, dissolve the ferrous sulfate salt for 30 to 60 min, then add sodium persulfate solution, and control the amount of sodium persulfate to be 0.4 to 0.6 g / L based on the amount of the primary coagulation precipitation supernatant or control the pH of the primary coagulation precipitation supernatant to be reduced by 0.5 to 0.3 pH units after oxidation, and the oxidation reaction time is 90 to 150 min to obtain oxidized wastewater;

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

[0012] As a further optimization scheme 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 scheme of the present invention, in step S2:

[0018] The mass ratio of the primary coagulation precipitation 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 scheme of the present invention, the soluble Mn in the wastewater 2+ Replace Fe 2+ Entering the ferrite lattice, it can be expressed as:

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

[0034] The beneficial effect of the present invention is that coagulation and precipitation are effectively combined with oxidation, and through primary coagulation and precipitation, oxidation reaction and secondary coagulation and precipitation, the pH adjusting agent, modified polymer anion flocculant and ferrous sulfate solution are used in combination to achieve the effect of effectively treating the pollutant manganese, so as to meet the manganese content of Class III indicator ≦0.10 mg / L of the "Groundwater Quality Standard". BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The present invention is a flow chart of the removal of manganese from a general industrial solid waste landfill leachate. 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 in the present invention is prepared by modifying a 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 to 100,000 becquerels and the irradiation time controlled to 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.

[0041] 2. Embodiment

[0042] Example 1

[0043] The manganese concentration in the leachate of an industrial solid waste landfill is 3.5 mg / L and the pH is 6.8. The steps for water treatment are as follows:

[0044] (1) 2.0 L of wastewater was placed in a beaker, the stirrer was turned on, the stirring speed was maintained at 80 rpm, and a 10% composite alkali emulsion was added to adjust the pH to 9.5, and the reaction time was 15 min;

[0045] (2) adjusting the stirring speed to 50 rpm, adding 2.0 mL of a 0.05% modified polymer anionic flocculant solution, maintaining stirring for 5 min, and then standing for 1 h;

[0046] (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.

[0047] (4) adding 5.0 mL of 15% sodium persulfate solution to the wastewater after adjusting the pH in step (3) and reacting for 120 min;

[0048] (5) Based on step (4), a 10% composite alkali emulsion was added to the wastewater to adjust the pH to 8.5, the stirring speed was adjusted to 80 rpm, and the reaction was carried out for 10 minutes;

[0049] (6) The stirring speed was adjusted to 50 rpm, 4.0 mL of a modified polymer anionic flocculant solution with a concentration of 0.05% was added, stirring was maintained for 10 min, and then the wastewater was allowed to stand for 1 h to allow the sludge to settle.

[0050] 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 reached the manganese requirement in Class III indicators of GB / T 14848-2017 "Groundwater Quality Standard".

[0051] Example 2

[0052] The manganese concentration in the leachate of an industrial solid waste landfill is 2.3 mg / L and the pH is 7.6. The steps for water treatment are as follows:

[0053] (1) 2.0 L of wastewater was placed in a beaker, the stirrer was turned on, the stirring speed was maintained at 120 rpm, and a 10% composite alkali emulsion was added to adjust the pH to 9.5, and the reaction time was 10 min;

[0054] (2) adjusting the stirring speed to 60 rpm, adding 1.5 mL of a 0.05% modified polymer anionic flocculant solution, maintaining stirring for 10 min, and then standing for 1 h;

[0055] (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;

[0056] (4) adding 3.5 mL of 15% sodium persulfate solution to the wastewater after adjusting the pH in step (3) and reacting for 150 min;

[0057] (5) Based on step (4), a 10% composite alkali emulsion was added to the wastewater to adjust the pH to 9.5, the stirring speed was 120 rpm, and the reaction was carried out for 15 minutes;

[0058] (6) In step (5), the stirring speed was adjusted to 30 rpm, 2.5 mL of a modified polymer anionic flocculant solution with a concentration of 0.05% was added, stirring was maintained for 10 min, and then the wastewater was allowed to stand for 1.5 h to allow sludge sedimentation.

[0059] 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 reached the manganese requirement in Class III indicators of GB / T 14848-2017 "Groundwater Quality Standard".

[0060] Example 3

[0061] The manganese concentration in the leachate of an industrial solid waste landfill is 0.62 mg / L and the pH is 8.2. The steps for water treatment are as follows:

[0062] (1) 2.0 L of wastewater was placed in a beaker, the stirrer was turned on, the stirring speed was maintained at 50 rpm, and a 10% composite alkali emulsion was added to adjust the pH to 10.0, and the reaction time was 5 min;

[0063] (2) adjusting the stirring speed to 20 rpm, adding 1.0 mL of a 0.05% modified polymer anionic flocculant solution, maintaining stirring for 6 min, and then standing for 1.5 h;

[0064] (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.

[0065] (4) adding 2.0 mL of 15% sodium persulfate solution to the wastewater after adjusting the pH in step (3) and reacting for 90 minutes;

[0066] (5) Based on step (4), a 10% composite alkali emulsion was added to the wastewater to adjust the pH to 10, the stirring speed was 120 rpm, and the reaction was carried out for 10 minutes;

[0067] (6) In step (5), the stirring speed was adjusted to 40 rpm, 2.0 mL of a modified polymer anionic flocculant solution with a concentration of 0.05% was added, stirring was maintained for 5 min, and then the wastewater was allowed to stand for 1.5 h to allow sludge sedimentation.

[0068] 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 reached the manganese requirement in Class III indicators of GB / T 14848-2017 "Groundwater Quality Standard".

[0069] Example 4

[0070] The manganese concentration in the leachate of an industrial solid waste landfill is 6.5 mg / L and the pH is 5.3. The steps for water treatment are as follows:

[0071] (1) 2.0 L of wastewater was placed in a beaker, the stirrer was turned on, the stirring speed was maintained at 120 rpm, and a 10% composite alkali emulsion was added to adjust the pH to 8.0, and the reaction time was 15 min;

[0072] (2) adjusting the stirring speed to 20 rpm, adding 5.5 mL of a 0.05% modified polymer anionic flocculant solution, maintaining stirring for 8 min, and then standing for 2.0 h;

[0073] (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;

[0074] (4) adding 4.0 mL of 15% sodium persulfate solution to the wastewater after adjusting the pH in step (3) and reacting for 90 minutes;

[0075] (5) Based on step (4), a 10% composite alkali emulsion was added to the wastewater to adjust the pH to 9.0, the stirring speed was adjusted to 120 rpm, and the reaction was carried out for 10 minutes;

[0076] (6) The stirring speed was adjusted to 30 rpm, 2.5 mL of a modified polymer anionic flocculant solution with a concentration of 0.05% was added, stirring was maintained for 10 min, and then the wastewater was allowed to stand for 2 h to allow the sludge to settle.

[0077] 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 can also meet the manganese requirements in Class III indicators of GB / T 14848-2017 "Groundwater Quality Standard".

[0078] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope 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 precipitation: using a pH adjusting agent to adjust the pH of the discharged wastewater to 8-10, the reaction stirring speed is 50-120rpm, the reaction time is 5-15min, and a modified polymer anion flocculant is added to the wastewater after alkali adjustment, the flocculation reaction time is 5-10min, the stirring speed is 20-60rpm, 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: add ferrous sulfate solution to the primary coagulation precipitation supernatant obtained in step S1, with a stirring speed of 50 to 120 rpm, adjust the pH thereof to 5 to 7, dissolve the ferrous sulfate salt for 30 to 60 min, then add sodium persulfate solution, and control 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 control the pH of the primary coagulation precipitation supernatant after oxidation to decrease by 0.5 to 0.3 pH units, and the oxidation reaction time to 90 to 150 min, to obtain oxidized wastewater; Step S3, secondary coagulation and precipitation: use a pH adjusting agent to adjust the pH of the oxidized wastewater to 8-10, the stirring speed is 50-120rpm, the reaction time is 5-15min, and a modified polymer anion flocculant is added to the oxidized wastewater. The flocculation reaction time is 5-10min and the stirring speed is 20-60rpm. After the flocculation reaction, let it stand to allow the suspended matter to settle, and perform a second solid-liquid sedimentation separation. Take out the secondary coagulation precipitation supernatant after precipitation for detection to determine whether the manganese concentration in the wastewater reaches 0.1mg / L.

2. The method for removing manganese from leachate of a general industrial solid waste landfill according to claim 1, characterized in that: In step S1: The pH adjusting agent can be 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 step S2: The mass ratio of the primary coagulation precipitation supernatant, ferrous sulfate solution and sodium sulfate solution is: 1: 0.01-0.04: 0.01-0.04; 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 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 of 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.

6. The method for removing manganese from leachate of a general industrial solid waste landfill according to claim 1, characterized in that: The soluble Mn in the wastewater 2+ Replace Fe 2+ Entering the ferrite lattice, it can be expressed as: Fe 2+ +Fe 3+ +Mn 2+ +OHˉ→Mn·Mn(OH)2Fe(OH)3+Fe(OH)2→MnO·Fe2O3↓+H2O。

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