Landfill leachate non-membrane treatment process

Abstract

The invention discloses a landfill leachate non-membrane treatment process, and belongs to the technical field of landfill leachate treatment.The landfill leachate non-membrane treatment process comprises pretreatment, primary treatment, secondary treatment, deep treatment and aftertreatment, ozonation and hydrolytic acidification are combined in the primary treatment, organic pollutants in water can be reduced, and biodegradability can be improved; in the secondary treatment, iron-carbon micro-electrolysis and flocculent precipitation are combined, primary battery reaction, physical adsorption and flocculent precipitation have a synergistic effect, the content of organic matters and heavy metals in water is reduced, the pH value of the primary treatment liquid subjected to hydrolytic acidification can meet the water inlet requirement of iron-carbon micro-electrolysis, and the dosage of an adjusting agent is reduced. The short-cut nitrification-denitrification realizes high-efficiency denitrification of the secondary treatment liquid with low C / N ratio, reduces the ammonia nitrogen content of the leachate, the post-treatment effluent of the advanced treatment liquid meets the discharge standard, no concentrated liquid exists in the treatment process, and the operation cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of landfill leachate treatment, and particularly relates to a non-membrane treatment process for landfill leachate. Background Art

[0002] Landfill leachate is generally produced in large quantities and has high pollutant concentrations, posing environmental risks. The treatment and disposal of landfill leachate has always been a pain point and hot issue in landfills.

[0003] The typical method for treating municipal solid waste leachate is to combine biological treatment with membrane deep-drain treatment. The membrane treatment process produces a large amount of concentrate, which is also enriched with high concentrations of organic matter and salt. Currently, this concentrate is typically directly re-injected into the landfill or leachate conditioning tank. However, over time, the concentration of pollutants in the leachate conditioning tank gradually increases, leading to a decrease in the efficiency of the leachate treatment facility. In severe cases, the leachate treatment facility may even operate abnormally. Therefore, the waste concentrate produced by membrane treatment can cause subsequent disposal problems and increase operating costs.

[0004] With the development of water treatment technology, non-membrane technologies such as adsorption, coagulation, Fenton and electrolysis have shown great potential, which makes it possible for them to replace membrane technology and provides more options for the combination of deep treatment technologies. Considering the advantages and disadvantages of different non-membrane technologies, how to balance the removal effect and economic cost so that they can better replace membrane technology has become the key to the problem. Summary of the Invention

[0005] Based on the above technical problems, the purpose of the present invention is to provide a non-membrane treatment process for landfill leachate, which avoids the production of concentrated liquid while ensuring that the treated effluent meets the discharge standards.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] The present invention provides a non-membrane treatment process for landfill leachate, comprising the following steps:

[0008] S1. Pretreatment: The landfill leachate passes through a grease trap, artificial screens, and filters to remove floating oil, suspended solids, and large particles to obtain a pretreated liquid.

[0009] S2. Primary treatment: The pre-treated liquid passes through an ozone contact oxidation tank and a hydrolysis acidification tank to convert refractory macromolecular organic matter into small molecular substances, reducing the BOD and COD in the pre-treated liquid to obtain a primary treated liquid;

[0010] S3, secondary treatment: The primary treatment liquid enters the iron-carbon micro-electrolysis cell, regulating tank and flocculation sedimentation tank to remove some organic pollutants, phosphorus and heavy metal substances in the primary treatment liquid to obtain secondary treatment liquid;

[0011] S4, advanced treatment: The secondary treatment liquid undergoes short-cut nitrification-denitrification treatment to obtain the advanced treatment liquid, which can reduce the ammonia nitrogen content;

[0012] S5. Post-treatment: The treated liquid passes through an activated carbon filter and a UV disinfection tank, ensuring that the effluent meets discharge standards. The activated carbon filter removes residual large particles, heavy metals, and other impurities, and UV disinfection and sterilization ensure that the effluent meets discharge standards.

[0013] The pH value of landfill leachate is generally 6-7, which is weakly acidic. As the service life of the landfill increases, it gradually becomes weakly alkaline. The optimal pH of the influent for ozone oxidation is between 6.5 and 8.5. Too low or too high will affect the oxidation efficiency. The high BOD and COD in landfill leachate are

[0014] Preferably, the filter is one of an activated carbon filter and a quartz sand filter.

[0015] Preferably, the SS of the pretreatment liquid is ≤200 mg / L.

[0016] Preferably, the ozone dosage of the ozone contact oxidation tank is 100-200 mg / L, and the contact time is 8-15 minutes. Ozone is a strong oxidant with strong oxidizing ability for organic pollutants and a fast oxidation reaction rate. It can reduce the molecular weight of organic matter, improve biochemical properties, and reduce some BOD and COD in water. After ozone treatment, acidic metabolites are produced, and the water pH will decrease slightly.

[0017] Preferably, the sludge concentration in the hydrolysis and acidification tank is 16-22 g / L, and the hydraulic retention time is 10-16 h. Hydrolysis and acidification can further convert difficult-to-biodegrade macromolecular substances into easily biodegradable small-molecule organic substances, remove COD, BOD5, SS, ammonia nitrogen and total phosphorus in the water, and the pH of the water quality will decrease after hydrolysis and acidification.

[0018] Preferably, the iron filings dosage of the iron-carbon micro-electrolysis cell is 3.5-4.3 g / L, the iron-carbon volume ratio is 1:1, and the hydraulic retention time is 12-18 h. The pH value of the influent to the iron-carbon micro-electrolysis is generally required to be 2-4. The pH of the water quality after hydrolysis and acidification is further reduced to meet the influent requirements of the iron-carbon micro-electrolysis. Iron-carbon micro-electrolysis can reduce COD, BOD5, SS, ammonia nitrogen and total phosphorus in water through the synergistic effects of primary cell reaction, flocculation and precipitation, oxidation-reduction, electrochemical enrichment, and physical adsorption, and undergo redox reactions with heavy metals to reduce the toxicity of heavy metals. The adsorption function of biochar and the flocculation and precipitation of metal ions achieve effective removal of heavy metals, and the pH of the water quality after treatment will increase.

[0019] Preferably, the pH value of the water in the regulating tank is adjusted to 6-7.5.

[0020] Preferably, the flocculant added to the flocculation sedimentation tank is PAM, the flocculation time is 30-45 minutes, and the sedimentation time is 8-12 hours. 2+ The flocculation and sedimentation effect can effectively improve the phosphorus removal effect, and the addition of flocculants can further reduce organic pollutants and suspended matter in the water.

[0021] Preferably, the dissolved oxygen concentration in the short-cut nitrification-denitrification process is controlled at 0.8-1.2 mg / L, and the sludge retention time is 10-15 days. Short-cut nitrification-denitrification can reduce sludge production, is suitable for wastewater with a low C / N ratio, and can efficiently remove ammonia nitrogen.

[0022] Preferably, the effluent water quality is COD<50mg / L, BOD5<20mg / L, ammonia nitrogen<10mg / L, SS<5mg / L, fecal coliform count<5000 / L, and total chromium<0.05mg / L.

[0023] Beneficial effects of the present invention:

[0024] (1) The leachate treatment process rationally combines physical treatment, biochemical treatment and electrochemical treatment. Compared with the membrane treatment process, there is no consumption of membrane materials and production of concentrated liquid, no need for secondary treatment of concentrated liquid, and the effluent can meet the discharge standards, reducing the operating cost.

[0025] (2) Combine ozone oxidation, hydrolysis acidification, micro-electrolysis and nitrification and denitrification treatment to effectively reduce the pollutant content in landfill leachate, and utilize the influence of each stage on the water pH to achieve self-regulation of pH, reduce the amount of acid and alkali used for pH adjustment, and save costs. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only 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 this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0027] Example 1

[0028] The COD of the leachate is 9050 mg / L, BOD5: 4790 mg / L, ammonia nitrogen: 2640 mg / L, SS: 1270 mg / L, and total chromium: 0.75 mg / L.

[0029] The landfill leachate is treated through the following steps:

[0030] S1. Pretreatment: The landfill leachate is passed through a grease trap, an artificial grid, and an activated carbon filter to obtain a pretreated liquid. The pretreated liquid SS is detected to be 177 mg / L.

[0031] S2. Primary treatment: The pre-treated liquid passes through an ozone contact oxidation tank and a hydrolysis acidification tank. The ozone dosage in the ozone contact oxidation tank is controlled to be 100 mg / L, the contact time is 15 min, the sludge concentration in the hydrolysis acidification tank is controlled to be 16 g / L, and the hydraulic retention time is 16 h. After treatment, a primary treated liquid is obtained.

[0032] S3, secondary treatment: The primary treatment liquid enters the iron-carbon micro-electrolysis cell, the iron filings dosage is controlled at 4.3g / L, the iron-carbon volume ratio is 1:1, the hydraulic retention time is 12h, the effluent enters the regulating tank, the pH is adjusted to 7.5, and then enters the flocculation sedimentation tank. After adding PAM flocculant, the flocculation reaction is carried out for 45min, the sedimentation time is set to 10h, and the effluent is the secondary treatment liquid;

[0033] S4, advanced treatment: The secondary treatment liquid enters the short-cut nitrification-denitrification tank, controls the dissolved oxygen concentration to 1.2 mg / L, and the sludge retention time to 10 days, and obtains the advanced treatment liquid after treatment;

[0034] S5. Post-treatment: The deep-treated liquid enters the activated carbon filter and the ultraviolet disinfection pool in turn. The effluent quality is COD: 32mg / L, BOD5: 11mg / L, ammonia nitrogen: 7mg / L, SS: 3.5mg / L, fecal coliform count: 3510 / L, total chromium: 0.01mg / L, and the effluent meets the discharge standards.

[0035] Example 2

[0036] The difference from Example 1 is that the ozone dosage in the ozone contact tank is controlled at 180 mg / L, and the other steps are the same as Example 1. The effluent water quality is COD: 21 mg / L, BOD5: 5 mg / L, ammonia nitrogen: 6 mg / L, SS: 2.9 mg / L, fecal coliform count: 3405 cells / L, and total chromium: 0.008 mg / L. The effluent meets the discharge standards.

[0037] Example 3

[0038] The difference from Example 1 is that the ozone dosage in the ozone contact tank is controlled at 200 mg / L, and the other steps are the same as Example 1. The effluent water quality is COD: 28 mg / L, BOD5: 9 mg / L, ammonia nitrogen: 7 mg / L, SS: 3.0 mg / L, fecal coliform count: 3380 cells / L, and total chromium: 0.007 mg / L. The effluent meets the discharge standards.

[0039] Example 4

[0040] The difference from Example 1 is that the amount of iron chips added to the iron-carbon micro-electrolysis cell is controlled at 3.8 g / L, and the other steps are the same as Example 1. The effluent water quality is COD: 35 mg / L, BOD5: 12 mg / L, ammonia nitrogen: 7 mg / L, SS: 3.9 mg / L, fecal coliform count: 3546 cells / L, total chromium: 0.01 mg / L, and the effluent meets the discharge standards.

[0041] Example 5

[0042] The difference from Example 1 is that the amount of iron filings added to the iron-carbon micro-electrolysis cell is controlled at 3.5 g / L, and the other steps are the same as Example 1. The effluent water quality is COD: 48 mg / L, BOD5: 16 mg / L, ammonia nitrogen: 9 mg / L, SS: 4.4 mg / L, fecal coliform count: 3590 cells / L, total chromium: 0.03 mg / L, and the effluent meets the discharge standards.

[0043] Example 6

[0044] The COD of the leachate is 9050 mg / L, BOD5: 4790 mg / L, ammonia nitrogen: 2640 mg / L, SS: 1270 mg / L, and total chromium: 0.75 mg / L.

[0045] The landfill leachate is treated through the following steps:

[0046] S1. Pretreatment: The landfill leachate is passed through a grease trap, an artificial grid, and an activated carbon filter to obtain a pretreated liquid. The pretreated liquid SS is tested to be 175 mg / L.

[0047] S2. Primary treatment: The pre-treated liquid passes through an ozone contact oxidation tank and a hydrolysis acidification tank. The ozone dosage in the ozone contact oxidation tank is controlled to be 180 mg / L, the contact time is 8 minutes, the sludge concentration in the hydrolysis acidification tank is controlled to be 22 g / L, and the hydraulic retention time is 10 hours. After treatment, a primary treated liquid is obtained.

[0048] S3, secondary treatment: The primary treatment liquid enters the iron-carbon micro-electrolysis cell, the iron filings dosage is controlled at 4.3g / L, the iron-carbon volume ratio is 1:1, the hydraulic retention time is 18h, the effluent enters the regulating tank, the pH is adjusted to 7.5, and then enters the flocculation sedimentation tank. After adding PAM flocculant, the flocculation reaction is carried out for 30min, the sedimentation time is set to 8h, and the effluent is the secondary treatment liquid;

[0049] S4, advanced treatment: The secondary treatment liquid enters the short-cut nitrification-denitrification tank, controls the dissolved oxygen concentration to 0.8 mg / L, and the sludge retention time to 15 days, and obtains the advanced treatment liquid after treatment;

[0050] S5. Post-treatment: The deep-treated liquid enters the activated carbon filter and the ultraviolet disinfection pool in turn. The effluent quality is COD: 34mg / L, BOD5: 15mg / L, ammonia nitrogen: 9mg / L, SS: 4.1mg / L, fecal coliform count: 3730 / L, total chromium: 0.02mg / L, and the effluent meets the discharge standards.

[0051] Example 7

[0052] The COD of the leachate is 9050 mg / L, BOD5: 4790 mg / L, ammonia nitrogen: 2640 mg / L, SS: 1270 mg / L, and total chromium: 0.75 mg / L.

[0053] The landfill leachate is treated through the following steps:

[0054] S1. Pretreatment: The landfill leachate is passed through a grease trap, an artificial grid, and an activated carbon filter to obtain a pretreated liquid. The pretreated liquid SS is detected to be 176 mg / L.

[0055] S2. Primary treatment: The pre-treated liquid passes through an ozone contact oxidation tank and a hydrolysis acidification tank. The ozone dosage in the ozone contact oxidation tank is controlled to be 180 mg / L, the contact time is 12 minutes, the sludge concentration in the hydrolysis acidification tank is controlled to be 20 g / L, and the hydraulic retention time is 13 hours. After treatment, a primary treated liquid is obtained.

[0056] S3, secondary treatment: The primary treatment liquid enters the iron-carbon micro-electrolysis cell, the iron filings dosage is controlled at 4.3g / L, the iron-carbon volume ratio is 1:1, the hydraulic retention time is 15h, the effluent enters the regulating tank, the pH is adjusted to 7.5, and then enters the flocculation sedimentation tank. After adding PAM flocculant, the flocculation reaction is 35min, the sedimentation time is set to 12h, and the effluent is the secondary treatment liquid;

[0057] S4, advanced treatment: The secondary treatment liquid enters the short-cut nitrification-denitrification tank, controls the dissolved oxygen concentration to 1.0 mg / L, and the sludge retention time to 12 days, and obtains the advanced treatment liquid after treatment;

[0058] S5. Post-treatment: The deep-treated liquid enters the activated carbon filter and the ultraviolet disinfection pool in turn. The effluent quality is COD: 33mg / L, BOD5: 14mg / L, ammonia nitrogen: 9mg / L, SS: 4.2mg / L, fecal coliform count: 3675 / L, total chromium: 0.02mg / L, and the effluent meets the discharge standards.

[0059] It can be seen from the above embodiments that the embodiment treatment method provided by the present invention can ensure that the landfill leachate meets the discharge standards. In Examples 1 to 3, the appropriate increase in the amount of ozone added can improve the degradation rate of organic pollutants, but excessive addition of ozone will increase costs on the one hand, and on the other hand, excess ozone will be reduced to oxygen, increasing the dissolved oxygen in the water, affecting the sludge activity in the subsequent hydrolysis and acidification process, and reducing the degradation rate of organic pollutants. On the basis of Example 1, Examples 4 and 5 reduce the amount of iron filings added in the iron-carbon micro-electrolysis. The reduction in the amount of iron filings added reduces the Fe participating in the primary cell reaction, reduces the organic matter and heavy metal removal rate, and the pH value of the effluent is acidic. The amount of medicine used to adjust the pH in the regulating tank will increase, and the cost will increase; a small amount of reduction will have a small impact, and can reduce the amount of iron filings and reduce costs. In Examples 6 and 7, other parameters in the treatment process are adjusted. Appropriate adjustments have a certain impact on the effluent water quality, but the effluent water quality can be controlled to meet the discharge standards.

[0060] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0061] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A non-membrane treatment process for landfill leachate, characterized in that: Including the following ingredients: S1. Pretreatment: The landfill leachate passes through a grease trap, an artificial grid and a filter to obtain a pretreated liquid; S2, primary treatment: the pre-treated liquid passes through an ozone contact oxidation tank and a hydrolysis acidification tank to obtain a primary treated liquid; S3, secondary treatment: the primary treatment liquid enters the iron-carbon micro-electrolysis cell, the regulating tank and the flocculation sedimentation tank to obtain the secondary treatment liquid; S4, deep treatment: the secondary treatment liquid is subjected to short-range nitrification-denitrification treatment to obtain deep treatment liquid; S5. Post-treatment: The deep-treated liquid passes through an activated carbon filter and an ultraviolet disinfection pool, and the effluent meets discharge standards.

2. A non-membrane treatment process for landfill leachate according to claim 1, characterized in that: The filter is one of an activated carbon filter and a quartz sand filter.

3. The non-membrane treatment process for landfill leachate according to claim 1, characterized in that: The pretreatment liquid SS≤200mg / L.

4. The non-membrane treatment process for landfill leachate according to claim 1, characterized in that: The ozone dosage of the ozone contact oxidation tank is 100-200 mg / L, and the contact time is 8-15 minutes.

5. The non-membrane treatment process for landfill leachate according to claim 1, characterized in that: The sludge concentration in the hydrolysis acidification tank is 16-22 g / L, and the hydraulic retention time is 10-16 h.

6. The non-membrane treatment process for landfill leachate according to claim 1, characterized in that: The iron filings dosage of the iron-carbon micro-electrolysis cell is 3.5-4.3 g / L, the iron-carbon volume ratio is 1:1, and the hydraulic retention time is 12-18 h.

7. The non-membrane treatment process for landfill leachate according to claim 1, characterized in that: The pH value of the water in the regulating pool is regulated to be 6-7.

5.

8. The non-membrane treatment process for landfill leachate according to claim 1, characterized in that: The flocculant added in the flocculation sedimentation tank is PAM, the flocculation time is 30-45 minutes, and the sedimentation time is 8-12 hours.

9. The non-membrane treatment process for landfill leachate according to claim 1, characterized in that: The effluent water quality is COD<50mg / L, BOD5<20mg / L, ammonia nitrogen<10mg / L, SS<5mg / L, fecal coliform count<5000 / L, and total chromium<0.05mg / L.