Treatment method of household garbage leachate

Abstract

The invention provides a treatment method of household garbage leachate. The treatment method comprises the following steps: measuring index data of to-be-treated garbage leachate; carrying out preliminary filtration on the leachate; the sodium carbonate and sodium hydroxide solution and calcium and magnesium ions are added to achieve the hardness removal effect; adjusting the pH value of the filtrate to 4-6, adding a sodium hypochlorite solution, adjusting the pH value of the solution obtained after bentonite decoloration and sand-water separation to 7-8, and adding polyaluminum ferric chloride and cation PAM; carrying out electrolytic treatment; and adding granular active carbon. In the physicochemical treatment stage, the conductivity of the leachate is remarkably reduced, the water quality is softened, the chromaticity of the leachate and part of water quality indexes are reduced, after physicochemical treatment, a large number of chlorine-containing free radicals, hypochlorous acid and other strong oxidizing substances are generated on the surface of the anode by means of electrochemical oxidation, and the indexes such as COD, ammonia nitrogen and total nitrogen are further controlled; and finally adsorbing by using granular active carbon. The technological process is clear, easy to operate, economical and efficient.

Description

Technical Field

[0001] The invention provides a method for treating domestic garbage leachate, and belongs to the technical field of garbage leachate treatment. Background Art

[0002] There are many methods for treating landfill leachate, mainly including biological treatment, physicochemical treatment, membrane treatment and the combined application of various processes. Among them, biological treatment is one of the most commonly used methods for leachate treatment, with the advantages of low operating costs and high treatment efficiency. Specific process forms include aerobic treatment (such as activated sludge method), anaerobic treatment and membrane bioreactor (MBR). However, the difficulty of this method lies in the cultivation of microorganisms. The physicochemical treatment method uses physical or chemical reactions to treat insoluble components and adsorbable organic matter in landfill leachate. Common physicochemical treatment methods include coagulation and sedimentation, flotation, adsorption, ion exchange, etc. For example, in the leachate treatment example of Longquanshan landfill in Hefei City, the process route of high-efficiency physicochemical pretreatment + biological pretreatment + ILMS high-efficiency bioreactor was adopted. Membrane treatment technology has also been widely used in landfill leachate treatment, mainly divided into four types: microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO). For example, the landfill leachate treatment project in Taizhou, Zhejiang Province adopted the process of anaerobic nitrification reactor combined with ultrafiltration. There are also advanced oxidation technologies, such as the Fenton process and its derivatives, which degrade refractory organic matter by producing strong oxidants, and are suitable for treating high-concentration toxic and hazardous pollutants. In general, the treatment of landfill leachate requires the selection of appropriate treatment methods based on specific water quality characteristics and discharge standards, and may require the combined application of multiple processes to achieve the best treatment effect. Summary of the invention

[0003] The invention provides a method for efficiently treating landfill leachate, which achieves the discharge of landfill leachate up to standard through the steps of hardness removal, decolorization, pre-phosphorus removal, electrocatalytic oxidation, heavy metal ion removal with activated carbon, biochemical treatment and the like.

[0004] The present invention is a method for treating landfill leachate with strong universality, high removal efficiency, simple operation, economy and practicality. The method can be used to deeply treat landfill leachate to meet the discharge requirements of the "Pollution Control Standard for Domestic Waste Landfill" (GB16889-2008).

[0005] The present invention provides a method for treating domestic waste leachate, comprising: physical and chemical treatment, according to the characteristics of the landfill leachate, high concentration of calcium and magnesium ions can be removed at the front end, by adding sodium carbonate and sodium hydroxide solution to form precipitation with calcium and magnesium ions, and filtering and separating. Adjust the pH to 4-6, add sodium hypochlorite solution and bentonite successively to treat the chromaticity of the leachate, and use the strong oxidizing property of the sodium hypochlorite solution and the strong adsorption property of the bentonite for decolorization. After standing, adjust the pH to 7-8, add polyaluminium ferric chloride (PAFC) and PAM for pre-phosphorus removal and turbidity removal. Clean Ti / SnO 2 -RuO 2 Electrode sheet, using the high concentration of chloride ions in the solution to generate strong oxidizing substances such as chlorine by electrolysis, catalytically degrading organic matter in the leachate. Activated carbon is used to adsorb heavy metal ions in the leachate, such as Pb 2+ , Hg 2+ Etc. This method has small site requirements and provides an economical and efficient treatment method for landfill leachate treatment.

[0006] The specific technical solution is:

[0007] The present invention provides a method for treating domestic garbage leachate, which specifically comprises the following steps:

[0008] Step 1: According to the emission requirements of the "Pollution Control Standard for Municipal Waste Landfills" (GB16889-2008), the index data of the leachate to be treated is measured and recorded, and then the leachate is preliminarily filtered.

[0009] Step 2: Based on the data measured in step 1, add appropriate amount of sodium carbonate and sodium hydroxide solution to form precipitation with calcium and magnesium ions, filter and separate to achieve the effect of removing hardness.

[0010] Step 3: Adjust the pH of the filtrate of step 2 to 4-6, first add an appropriate amount of sodium hypochlorite solution, stir and react for 2 hours, then add a certain amount of bentonite in proportion, stir for 1 hour and then let it stand for 1 hour, use the strong oxidizing property of sodium hypochlorite solution and the strong adsorption property of bentonite to decolorize, and perform sand and water separation after standing.

[0011] Step 4: In the solution after the sand and water separation in step 3, first adjust the pH to 7-8, then add polyaluminium ferric chloride (PAFC), stir at a constant speed for 8 minutes, then drop cationic PAM with a molecular weight of 12 million, stir slowly for 2 minutes, let stand for 30 minutes, and then filter and separate.

[0012] Step 5: Ti / SnO 2 -RuO 2 The electrode sheet was washed and dried, and placed in the solution filtered in step 4 to form Ti / SnO 2 -RuO 2The electrode sheet is used as the anode, and a titanium sheet of the same size as the anode is used as the cathode. The optimal degradation efficiency is obtained by controlling key degradation parameters such as current density and electrolysis time.

[0013] Step 6: Add granular activated carbon (iodine value not less than 800 mg / g) to the solution after electrolysis in step 5, control the addition amount to 10-80 mg / L, stir at a constant speed for 12 hours and then filter to adsorb heavy metal ions in the leachate.

[0014] Step 7: Test the solution after filtering in step 6. If it meets the emission requirements of the "Pollution Control Standards for Municipal Waste Landfills" (GB16889-2008), it will be discharged in accordance with the regulations; if it does not meet the requirements, it will flow back to step 3 for further processing.

[0015] Furthermore, the addition amount of sodium hypochlorite is not less than 0.5 wt%, the addition amount of bentonite is not less than 10 g / L, the addition amount of polyaluminium ferric chloride is not less than 0.1 g / L, and the addition amount of PAM is not less than 5 mg / L.

[0016] In step 5, after physical and chemical treatment, the chromaticity removal efficiency is close to 70%, and the total phosphorus removal efficiency is close to 75%. 2 -RuO 2 The electrode sheet was used as the anode, and a titanium sheet of the same size as the anode was used as the cathode. The pH of the leachate was adjusted to about 5, and the current density was controlled to 20 mA / cm under stirring. 2 The landfill leachate is electrolyzed for no less than 90 minutes. During the electrolysis process, samples can be taken in time to determine the treatment effects of ammonia nitrogen, total nitrogen and COD in the leachate. After electrolysis, the removal rates of COD, ammonia nitrogen and total nitrogen are all higher than 80%.

[0017] In step 6, the amount of granular activated carbon added is not less than 60g / L. After activated carbon adsorption, except for total phosphorus, all indicators can meet the emission requirements of the "Pollution Control Standard for Municipal Waste Landfill" (GB16889-2008). The used granular activated carbon can be chemically desorbed and recycled after reaching adsorption saturation.

[0018] The technical effects of the present invention are as follows:

[0019] (1) This method is designed with three steps: physicochemical treatment + electrocatalytic treatment + activated carbon adsorption treatment. The method is simple and easy to operate, economical and efficient, and occupies less space.

[0020] (2) This method combines the high concentration of chloride ions in the leachate with a ruthenium-containing electrode for electrolysis, utilizing the special advantage of the ruthenium electrode in reducing the potential for chlorine evolution to generate a variety of chlorine-containing free radicals and strong oxidizing substances such as hypochlorous acid, thereby improving the degradation efficiency and reducing the cost, and recycling the chloride ions.

[0021] (3) The combination of PAFC and PAM was used in the coagulation process, which not only improved the coagulation treatment effect but also reduced the total phosphorus in the leachate. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the landfill leachate treatment process of the present invention. DETAILED DESCRIPTION

[0023] The specific technical solution of the present invention is explained in conjunction with embodiments.

[0024] Embodiment 1:

[0025] This embodiment uses aged leachate filtered from a landfill in Sichuan, samples the initial index data and numbers it 0, and adds the aged leachate to 1L beakers numbered 1, 2, 3, 4, and 5, respectively. The amount added to each beaker is 1L, and a magnetic stirrer is added and the speed is controlled to 200r / min. Sodium carbonate and sodium hydroxide are added while stirring, and the mass of sodium carbonate and sodium hydroxide added is controlled as shown in Table 1 to explore the optimal ratio of sodium hydroxide and sodium carbonate for combined hardness removal. The table shows that the stock solution has a better hardness removal effect when 3g of sodium hydroxide and 3g of sodium carbonate are added respectively. The conductivity of the stock solution before treatment is 29000 / us cm -1 , after treatment, 3600 / us cm -1 .

[0026] Table 1 Effect of sodium carbonate and sodium hydroxide dosage on conductivity

[0027]

[0028] Embodiment 2:

[0029] According to the conclusion of Example 1, the hardness was removed and then filtered. The filtrate was adjusted to pH 7.5 with dilute hydrochloric acid and then added to 1L beakers numbered 6, 7, 8, 9, and 10, with each beaker adding 1L. A magnetic stirrer was added and the speed was controlled to 100r / min. Then sodium hypochlorite (10Wt%) was added, and bentonite was added after stirring for 1h. The speed was adjusted to 200r / min and stirred for 30min, and the leachate was allowed to stand for filtration and detection. By adjusting the addition ratio of sodium hypochlorite and bentonite, the chromaticity change of the leachate before and after the treatment was tested, and the results are shown in Table 2.

[0030] Table 2 Effect of the addition ratio of sodium hypochlorite and bentonite on the removal of chroma

[0031]

[0032]

[0033] According to Table 2, the chromaticity of the original leachate solution after hardening by Example 1 is about 3000 times, and the treatment of the chromaticity of the leachate by the strong oxidizing property of sodium hypochlorite and the strong adsorption property of bentonite has a significant effect. When the addition amount of sodium hypochlorite and bentonite is 4mL and 10g respectively, the chromaticity of the leachate is reduced from 3000 times to 850 times, and the removal rate is 71.6%. When the addition amount of sodium hypochlorite and bentonite is 5mL and 9g respectively, the chromaticity of the leachate is reduced from 3000 times to 820 times, and the removal rate is 72.7%, which is not much different from No. 9. Considering the cost of sodium hypochlorite and bentonite, the optimal choice is when the addition amount of sodium hypochlorite and bentonite is 4mL and 10g respectively.

[0034] Embodiment 3:

[0035] According to the conclusion of Example 2 No. 9, the test was conducted, and the supernatant obtained from the test results was added to 1L beakers No. 11, 12, 13, 14, 15, and 16, and the amount added to each beaker was 1L. A magnetic stirrer was added and the speed was controlled to 150r / min, dilute hydrochloric acid was added to adjust the pH to about 6.8, and then polyaluminium ferric chloride (PAFC) was added. After stirring at a uniform speed for 8min, 3mg / L of cationic PAM with a molecular weight of 12 million was added until large alum flowers appeared, and the speed was controlled to 60r / min and stirred slowly for 2min. After the stirring was finished and the mixture was allowed to stand for 30min, the filtration test was performed. According to Table 3, when the amount of PAFC added was 0.2g / L, the total phosphorus effluent reached the emission standard of the "Standard for Pollution Control of Domestic Waste Landfills" (GB16889-2008), and the total phosphorus was not significantly reduced by continuing to add PAFC to 0.25g / L, so the addition of PAFC was 0.2g / L, which was the most preferred.

[0036] Table 3 Effect of PAFC addition on total phosphorus removal

[0037]

[0038] Embodiment 4:

[0039] According to the conclusion of Example 3 No. 15, the test was conducted, and the supernatant obtained from the test results was added to 1L beakers No. 17, 18, 19, 20, 21, and 22, respectively. The amount added to each beaker was 1L, and the pH was adjusted to 5 with dilute hydrochloric acid. A magnetic stirrer was added and the speed was controlled to 150r / min. Ti / SnO 2 -RuO 2 The electrode sheet is used as the anode, and a titanium sheet of the same size as the anode is used as the cathode. They are placed in beakers numbered 17, 18, 19, 20, 21, and 22, respectively, and connected to the positive and negative electrodes of a DC power supply. The current density is controlled to be 0, 10, 20, 30, 40, and 50 mA / cm 2 After 4 hours of degradation, the sample was tested and the current density was found to be 50 mA / cm2 When the current density increases to 60mA / cm 2 Therefore, the optimal current density is 60mA / cm 2 .

[0040] Table 4 Effect of current density on removal effect

[0041] Beaker No. 17 18 19 20 21 22 23 <![CDATA[Current density (mA cm -2 )]]> 0 10 20 30 40 50 60 <![CDATA[COD / (mgL -1 )]]> 5000 4160 2207 922 493 189 67 <![CDATA[Ammonia nitrogen / (mgL -1 )]]> 2300 1488 621 278 104 22 19 <![CDATA[Total nitrogen / (mgL -1 )]]> 3600 2510 1147 415 178 47 36

[0042] Embodiment 5:

[0043] The effluent after electrolysis in Example 4 was added to 1L beakers numbered 24, 25, 26, 27, and 28, with the amount added to each beaker being 1L. Granular activated carbon with an iodine value of 800mg / g, a particle size of 1mm, and a length of 1cm was added to beakers 24-28, and a magnetic stirrer was added to control the speed to 150r / min. After stirring for 30min, the heavy metal ion content of the effluent was measured. From Table 5, when the amount of activated carbon added was 80mg / L, the heavy metal ion content of the effluent reached the standard.

[0044] Table 5 Effect of activated carbon addition on heavy metal ion removal

[0045] Beaker No. 24 25 26 27 28 <![CDATA[Activated carbon / (mg L -1 )]]> 0 20 40 60 80 <![CDATA[Total mercury / (mgL -1 )]]> 0.002 0.002 0.002 0.001 0.001 <![CDATA[Total chromium / (mgL -1 )]]> 0.15 0.1 0.1 0.006 0.005 <![CDATA[Total Cadmium / (mgL -1 )]]> 0.2 0.1 0.04 0.01 0.008 <![CDATA[Total lead / (mgL -1 )]]> 4 1 0.2 0.12 0.08 <![CDATA[Total Arsenic / (mgL -1 )]]> 0.2 0.12 0.07 0.05 0.05

[0046] The process of the present invention combines simple processes such as physical and chemical de-hardening, chemical decolorization, adsorption coagulation, etc., and significantly reduces the conductivity of the leachate in the physical and chemical treatment stage, softens the water quality, and reduces the chromaticity of the leachate and some water quality indicators, such as COD, total phosphorus, ammonia nitrogen, and total nitrogen. After the physical and chemical treatment, electrochemical oxidation is used to remove the Ti / SnO 2 -RuO 2 A large number of chlorine-containing free radicals and strong oxidizing substances such as hypochlorous acid are generated on the anode surface, which further control indicators such as COD, ammonia nitrogen, and total nitrogen. Finally, granular activated carbon adsorption is used to monitor heavy metal ions, as well as COD, ammonia nitrogen, total nitrogen and other indicators in real time to ensure that the effluent water quality meets the emission standards of the "Pollution Control Standards for Domestic Waste Landfills" (GB16889-2008). The process is clear, simple to operate, economical and efficient, and is a leachate treatment solution worthy of widespread application.

Claims

1. A method for treating domestic waste leachate, characterized in that: The following steps are involved: Step 1: According to the discharge requirements, measure and record the index data of the landfill leachate to be treated, and then perform preliminary filtration on the leachate; Step 2: According to the data measured in step 1, sodium carbonate and sodium hydroxide solution are added to generate precipitation with calcium and magnesium ions, and filtered and separated to achieve the effect of removing hardness; Step 3: The pH of the filtrate of step 2 is adjusted to 4-6, sodium hypochlorite solution is added first, stirred for reaction for 2 hours, and then bentonite is added, stirred for 1 hour and then allowed to stand for 1 hour, and the strong oxidizing property of the sodium hypochlorite solution and the strong adsorption property of the bentonite are used for decolorization, and after standing, sand and water are separated; Step 4: In the solution after the sand and water separation in step 3, first adjust the pH to 7-8, then add polyaluminium ferric chloride, stir at a constant speed for 8 minutes, then drop cationic PAM with a molecular weight of 12 million, stir slowly for 2 minutes, let stand for 30 minutes, and then filter and separate; Step 5: Wash and dry the Ti / SnO2-RuO2 electrode sheet, place it in the solution filtered in step 4, and perform electrolysis treatment; Step 6: Add granular activated carbon to the solution after electrolysis in step 5, stir at a constant speed for 12 hours and then filter to adsorb heavy metal ions in the leachate; Step 7: Test the solution after filtering in step 6. If it meets the discharge requirements, discharge it according to regulations; if it does not meet the standards, return it to step 3 for further processing.

2. The method for treating domestic waste leachate according to claim 1, characterized in that: In step 3, the amount of sodium hypochlorite added is not less than 0.5 wt%, and the amount of bentonite added is not less than 10 g / L.

3. The method for treating domestic waste leachate according to claim 1, characterized in that: In step 4, the amount of polyaluminium ferric chloride added is not less than 0.1 g / L and the amount of PAM added is 5 mg / L.

4. The method for treating domestic waste leachate according to claim 1, characterized in that: In step 5, the Ti / SnO2-RuO2 electrode sheet is used as the anode, and the titanium sheet of the same size as the anode is used as the cathode. The pH of the leachate is adjusted to 5, and the current density is controlled to 20 mA / cm under stirring. 2 The landfill leachate is electrolyzed for a period of not less than 90 minutes.

5. The method for treating domestic waste leachate according to claim 1, characterized in that: In step 6, the amount of granular activated carbon added is not less than 90 g / L.

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