A method for treating landfill leachate concentrate by coagulation with waste incineration flue gas

Abstract

The present application relates to the technical field of high-concentration organic wastewater treatment, and particularly relates to a method for treating landfill leachate concentrate by waste incineration flue gas and coagulation. The pH of the landfill leachate concentrate is adjusted to 8-10, and the waste incineration flue gas is introduced into the concentrate; the CO2 in the flue gas reacts with the concentrate to generate calcium carbonate and magnesium carbonate precipitates, thereby reducing the hardness and salinity of the concentrate and facilitating subsequent coagulation to remove TOC; meanwhile, the introduction of the waste incineration flue gas into the concentrate absorbs the CO2 therein, thereby fixing the CO2 and reducing the greenhouse effect on the environment; after the aeration is stopped, an appropriate amount of PFS is added to the landfill leachate concentrate and stirred; after the stirring is completed, the concentrate is allowed to stand and separate into solid and liquid, the supernatant is subjected to subsequent membrane treatment and recycled, and the precipitate is processed into fertilizer for landscaping. The present application has the beneficial effects of significantly improving the removal rates of TOC, Ca 2+ and Mg 2+ , achieving waste treatment by waste, and realizing clean production and carbon dioxide fixation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-concentration organic wastewater treatment, and particularly relates to a method for treating landfill leachate concentrate by using waste incineration flue gas and coagulation. BACKGROUND

[0002] Whether landfilling or incineration, the disposal of solid waste is always accompanied by the production of leachate. With the process of industrialization and commercialization, the production of municipal solid waste and industrial solid waste is rapidly increasing, and the production of leachate is also increasing day by day. The commonly used leachate treatment method "MBR (+ UF) + NF / RO" will produce 20-30% of the original waste liquid volume of leachate concentrate. The composition of these concentrates is complex, the concentration of organic matter is high, the biodegradability is poor, the color and hardness are high, the inorganic salt ion content is high, the pH is generally alkaline, between 7.5-9.0, but the heavy metal content is basically at a low level.

[0003] The existing treatment process of landfill leachate concentrate mainly includes spraying back, recharging, evaporation, advanced oxidation, membrane treatment and coagulation treatment. Due to the large production of landfill leachate concentrate, the low average heat value, the high inorganic salt content and the poor biodegradability, spraying back and recharging may increase the operation cost, cause damage to the system and equipment, and cause secondary pollution to the environment. For evaporation, the high salt content in the landfill leachate concentrate will also cause equipment corrosion, and the energy consumption and operation cost are very high. The pollutant concentration in the residual liquid is extremely high and needs to be properly treated. The cost of advanced oxidation and membrane treatment is high, and in addition, some advanced oxidation and membrane treatment processes require complex treatment processes and operation procedures.

[0004] Coagulation, as a common method of water treatment, has the advantages of simple operation, high pollutant removal rate, etc., and is often used to reduce the turbidity and color of wastewater, remove suspended particles, dissolved pollutants and pathogens in water, etc. In the treatment of landfill leachate concentrate, coagulation is often used as a pretreatment method to remove a part of refractory dissolved organic matter (such as humic acid) and inorganic salt ions (such as calcium and magnesium ions). Essentially, coagulation is a physical and chemical process that reduces the repulsive potential of the double electric layer by adding various coagulants, so that colloidal particles begin to link, then aggregate into larger particles or flocs, and the formed flocs are finally removed from the water body through solid-liquid separation. The mechanism of coagulation includes charge neutralization, interception, adsorption and complexation with metal ions of coagulants into insoluble aggregates. It is worth noting that a very important finding reported by many researchers: the optimal operating conditions for removing turbidity or color by coagulation are not necessarily the same as those for removing TOC. Therefore, single coagulation treatment cannot achieve ideal treatment effect.

[0005] The existing coagulation treatment method of landfill leachate concentrate is to add coagulants such as PAC (polyaluminum chloride), PSAF (polyaluminum ferric silicate), PFS (polyferric sulfate) into the landfill leachate concentrate, and to convert the refractory organic matter in the concentrate into flocculation precipitate by using the mechanism of compressed double electric layer, adsorption electric neutralization, adsorption bridging and precipitate trapping, so as to remove the suspended solids, turbidity, TOC and the like in the wastewater. However, the TOC removal rate of the treatment method is not ideal, and the subsequent treatment still faces the problem of TOC removal.

[0006] On the basis of PFS coagulation, the method introduces landfill incineration flue gas (CO2) into the concentrate, which can not only remove TOC, color and the like in the landfill leachate concentrate, but also remove high-concentration calcium and magnesium ions in the concentrate. In addition, the method can also fix carbon dioxide in the flue gas. The landfill incineration plant needs to treat landfill leachate and landfill incineration flue gas, and the method realizes the collaborative treatment of the two in the same plant, which has a very broad application prospect. SUMMARY

[0007] The purpose of the present application is to provide a method for coagulation treatment of landfill leachate concentrate by landfill incineration flue gas, so as to solve the problem that the existing coagulation treatment method of landfill leachate concentrate has an unsatisfactory TOC removal rate and poor treatment effect.

[0008] To achieve the above-mentioned purpose, the present application adopts the following technical scheme: a method for coagulation treatment of landfill leachate concentrate by landfill incineration flue gas, comprising the following steps:

[0009] S1, adding an alkali solution to adjust the pH of the landfill leachate concentrate;

[0010] S2, introducing landfill incineration flue gas into the concentrate after adjusting the pH in S1;

[0011] S3, after stopping aeration, standing, adding an appropriate amount of PFS to the leachate concentrate for coagulation;

[0012] S4, after coagulation, standing and precipitating, and then separating the solid and liquid to obtain supernatant and precipitate;

[0013] S5, performing membrane deep treatment on the supernatant obtained in S4 to reach the recycling standard, and collecting the precipitate obtained in S4 for preparation of garden greening fertilizer.

[0014] Further, in S1, the alkali solution is NaOH solution with a concentration of 5 mol / L, and the pH of the concentrate is adjusted to 8-10.

[0015] Further, in the S2, the amount of the waste incineration flue gas introduced is 0.1-0.4 L / min, and the introduction time is 5-15 min.

[0016] Further, in the S3, the standing time is 5-10 h.

[0017] Further, in the S3, the amount of the PFS added is 2-7 g / L.

[0018] Further, in the S4, the standing and precipitation time is 10-15 h.

[0019] Further, in the S4, the removal rate of TOC in the supernatant is 74.3-78.7%, the removal rate of Ca 2+ is 88.7-89.7%, and the removal rate of Mg 2+ is 11.0-19.2%.

[0020] The beneficial effects of the present application are:

[0021] 1. The present method uses the waste incineration flue gas to treat the landfill leachate concentrate, which significantly improves the removal rates of TOC, Ca 2+ and Mg 2+ ;

[0022] 2. The initial pH value of the landfill leachate concentrate is alkaline, generally 7.5-9.0, which is not conducive to coagulation treatment, but the CO2 in the flue gas can make the pH of the solution weakly acidic, which is conducive to subsequent coagulation treatment.

[0023] 3. The calcium carbonate and magnesium carbonate precipitates formed by the introduction of the flue gas play a synergistic role in the coagulation process, which accelerates the coagulation and sedimentation speed.

[0024] 4. The carbon dioxide used in the present method comes from the waste incineration flue gas, which realizes clean production and carbon dioxide fixation. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a process flow diagram of the present method;

[0026] Figure 2 is a removal rate diagram of TOC, Ca 2+ and Mg 2+ of each embodiment of the present application. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application.

[0028] The dosage of PFS added in all the following examples and comparative examples is the same, and the time and flow rate of the flue gas in each example are also consistent.

[0029] As shown in the process flow of the present application is: Figure 1

[0030] The initial pH of the leachate concentrate is 7.86, and an alkali solution is added thereto, wherein the alkali solution is a 5 mol / L sodium hydroxide solution, and the pH of the leachate concentrate is adjusted to 8-10; then the flue gas of waste incineration is slowly introduced into the concentrated solution after adjusting the pH, and the amount of flue gas introduced is 0.1-0.4 L / min, and the introduction time is 5-15 min; after stopping the aeration, the CO2 in the flue gas of waste incineration reacts with Ca 2+ and Mg 2+ to generate precipitates, which helps to remove Ca 2+ and Mg 2+ , and helps to remove TOC in the subsequent coagulation.

[0031] Then, a proper amount of PFS is added to the leachate concentrate for coagulation, and the calcium carbonate and magnesium carbonate precipitates generated in the above process play a synergistic sedimentation role in the coagulation process, which speeds up the coagulation and sedimentation speed; after standing and sedimentation, solid-liquid separation is performed to obtain supernatant and precipitate; the supernatant is subjected to membrane deep treatment to reach the recycling standard, and the obtained precipitate can be used for the preparation of landscaping fertilizer.

[0032] Through the method of the present application, the TOC removal rate in the leachate concentrate reaches 74.3-78.7%, the removal rate of Ca 2+ reaches 88.7-89.7%, and the removal rate of Mg 2+ reaches 11.0-19.2%, which improves the removal rates of Ca 2+ and Mg 2+ , significantly improves the TOC removal rate, has a positive and beneficial technical effect on the treatment of leachate concentrate, and further fixes the carbon dioxide in the flue gas, reduces the greenhouse effect on the environment, and helps to protect the environment.

[0033] Example 1

[0034] The initial pH of the leachate concentrate is not adjusted (7.86), and CO2 is introduced.

[0035] The pH of the leachate concentrate is not adjusted, and the flue gas of waste incineration is introduced into the concentrate; after stopping the aeration, the leachate concentrate is allowed to stand for 5-10 h, and a proper amount of PFS is added to the leachate concentrate for coagulation; after the coagulation is completed, the leachate concentrate is allowed to stand and sediment for 10-15 h, and solid-liquid separation is performed to form supernatant and precipitate, and the supernatant is subjected to detection and analysis.​

[0036] Example 2

[0037] Adjusting the initial pH of the leachate concentrate to 8, and passing CO2.

[0038] Adjusting the initial pH of the leachate concentrate to 8 with NaOH, and passing waste incineration flue gas into the concentrate; after stopping the aeration, standing for 5-10 h, adding an appropriate amount of PFS into the waste leachate concentrate for coagulation; after the coagulation is completed, standing for 10-15 h of precipitation, solid-liquid separation to form supernatant and precipitate, and detecting and analyzing the supernatant.

[0039] Example 3

[0040] Adjusting the initial pH of the leachate concentrate to 8.5, and passing CO2.

[0041] Adjusting the initial pH of the leachate concentrate to 8.5 with NaOH, and passing waste incineration flue gas into the concentrate; after stopping the aeration, standing for 5-10 h, adding an appropriate amount of PFS into the waste leachate concentrate for coagulation; after the coagulation is completed, standing for 10-15 h of precipitation, solid-liquid separation to form supernatant and precipitate, and detecting and analyzing the supernatant.

[0042] Example 4

[0043] Adjusting the initial pH of the leachate concentrate to 9, and passing CO2.

[0044] Adjusting the initial pH of the leachate concentrate to 9 with NaOH, and passing waste incineration flue gas into the concentrate; after stopping the aeration, standing for 5-10 h, adding an appropriate amount of PFS into the waste leachate concentrate for coagulation; after the coagulation is completed, standing for 10-15 h of precipitation, solid-liquid separation to form supernatant and precipitate, and detecting and analyzing the supernatant.

[0045] Example 5

[0046] Adjusting the initial pH of the leachate concentrate to 9.5, and passing CO2.

[0047] Adjusting the initial pH of the leachate concentrate to 9.5 with NaOH, and passing waste incineration flue gas into the concentrate; after stopping the aeration, standing for 5-10 h, adding an appropriate amount of PFS into the waste leachate concentrate for coagulation; after the coagulation is completed, standing for 10-15 h of precipitation, solid-liquid separation to form supernatant and precipitate, and detecting and analyzing the supernatant.

[0048] Example 6

[0049] Adjusting the initial pH of the leachate concentrate to 10, and passing CO2.

[0050] The initial pH of the concentrated leachate is adjusted to 10 by NaOH, and waste incineration flue gas is introduced into the concentrated leachate; after the introduction is stopped, the concentrated leachate is allowed to stand for 5-10 hours, and an appropriate amount of PFS is added to the concentrated leachate for coagulation; after the coagulation is completed, the concentrated leachate is allowed to stand for 10-15 hours, and the supernatant and the precipitate are separated by solid-liquid separation, and the supernatant is detected and analyzed.

[0051] Comparative example

[0052] Only coagulation treatment is performed.

[0053] An appropriate amount of PFS is added to the concentrated leachate for coagulation; after the coagulation is completed, the concentrated leachate is allowed to stand for 10-15 hours, and the supernatant and the precipitate are separated by solid-liquid separation, and the supernatant is detected and analyzed.

[0054] The TOC, Ca 2+ and Mg 2+ removal rates of examples 1-6 and the comparative example are shown in the following figure (solid line and dotted line for examples 1-6, and dashed straight line for the comparative example).

[0055] The TOC removal rate of examples 1-6 is 74.3-78.7%, the Ca 2+ removal rate is 88.7-89.7%, and the Mg 2+ removal rate is 11.0-19.2%; the TOC removal rate of the comparative example is 40.01%, and the Ca 2+ and Mg 2+ removal rates are 88.08% and 10.03%, respectively.

[0056] It can be found from the comparison that the introduction of waste incineration flue gas makes the solution present a weak acid environment, which is helpful for coagulation, significantly improves the TOC removal rate, which is 1.9 times that of only coagulation treatment, and the Ca 2+ and Mg 2+ removal rates are also improved; on the other hand, the method fixes carbon dioxide in the flue gas, reduces the greenhouse effect on the environment, and treats waste with waste.

[0057] The present application is not limited to the above best mode, and anyone can derive other various forms of products under the inspiration of the present application, but regardless of any changes in shape or structure, any technical solution with the same or similar technical solutions as the present application falls within the protection scope of the present application.

Claims

1. A method for treating landfill leachate concentrate by coagulation with waste incineration flue gas, characterized in that, The method comprises the following steps: S1, adding an alkali solution to adjust the pH of the landfill leachate concentrate; The alkali solution is NaOH solution with a concentration of 5 mol / L, and the pH of the concentrate is adjusted to 8-10; S2, passing landfill incineration flue gas into the concentrate after pH adjustment in S1 to make the solution present a weak acid environment; After the flue gas is passed in, CO2 in the flue gas will make the pH of the solution present a weak acidity, which is helpful for subsequent coagulation treatment; The passing-in amount of the landfill incineration flue gas is 0.1-0.4 L / min, and the passing-in time is 5-15 min; S3, after stopping aeration, standing, and adding an appropriate amount of PFS into the leachate concentrate for coagulation, the calcium carbonate and magnesium carbonate precipitates formed by the passing-in of the flue gas play a synergistic role in the coagulation process; The standing time is 5-10 h, and the adding amount of PFS is 2-7 g / L; S4, after the coagulation is completed, standing and precipitation, and then solid-liquid separation, supernatant and precipitate are obtained; The standing precipitation time was 10-15 h; the removal rate of TOC in the supernatant was 74.3-78.7%, the removal rate of Ca 2+ was 88.7-89.7%, and the removal rate of Mg 2+ was 11.0-19.2%. S5, the supernatant obtained in S4 is subjected to membrane deep treatment to reach a recycling standard, and the precipitate obtained in S4 is collected and used for preparation of a landscaping fertilizer.

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