Device for treating aged landfill leachate by using excess sludge as carbon source

Abstract

The utility model discloses a device for treating aged landfill leachate by taking excess sludge as a carbon source, and belongs to the technical field of sewage treatment. The bottom of the anaerobic reactor I is connected with a feeding box water inlet area through a water inlet pipe and is connected with a feeding box sludge storage area through a sludge inlet pipe, and the upper part of a settling area I of the anaerobic reactor I is connected with the bottom of the anaerobic reactor I through an inner circulating pipe I and is connected with the bottom of the anaerobic reactor II through a water outlet pipe I; the upper part of a settling zone II of the anaerobic reactor II is connected with the bottom of the anaerobic reactor II through an inner circulating pipe II and is connected with the water inlet end of the short-cut nitrification reactor through a water outlet pipe II; the short-cut nitrification reactor is connected with the sedimentation tank through a water outlet pipe III; the sedimentation tank is connected with the water inlet end of the short-cut nitrification reactor through a sludge return pipe, connected with the bottom of the anaerobic reactor I through a nitrification liquid return pipe and connected with the bottom of the electrochemical reaction tank through a water outlet pipe IV; and the electrochemical reaction tank finally discharges water through a water outlet pipe V. The method can be used for efficiently treating the aged landfill leachate and removing organic pollutants and high-concentration ammonia nitrogen.

Description

Technical Field

[0001] The utility model belongs to the technical field of sewage treatment, and particularly relates to a device for treating old garbage leachate by using residual sludge as a carbon source. Specifically, the utility model utilizes residual sludge from the old garbage leachate treatment process as an additional carbon source for denitrification, and can also remove difficult-to-biodegrade organic matter. Background Art

[0002] With the acceleration of urbanization and the increase of human activities, the treatment of landfill leachate has become an environmental problem that needs to be solved urgently. In particular, the leachate of old landfill contains complex organic pollutants, heavy metals and high concentrations of ammonia nitrogen, which are highly toxic, poorly biodegradable, low in carbon-nitrogen ratio and contain a large amount of difficult-to-biodegrade organic matter. Direct discharge will cause serious pollution to the environment. Therefore, it is necessary to adopt appropriate treatment processes for treatment.

[0003] At present, the treatment methods of landfill leachate mainly include physical and chemical methods, biological methods and comprehensive treatment methods. Among them, physical and chemical methods include pretreatment, stripping, advanced oxidation, ultrafiltration, nanofiltration and reverse osmosis. The domestic main process route is "pretreatment + biological treatment + membrane deep treatment". However, the operating cost of membrane treatment technology is high and membrane retention will be generated. These concentrated liquids will contain higher concentrations of highly toxic and carcinogenic pollutants and are difficult to handle. They may be transferred to the environment and endanger human health.

[0004] Since old landfill leachate has the characteristics of high ammonia nitrogen and low carbon-nitrogen ratio, this leads to a serious shortage of carbon sources in the denitrification process. The lack of carbon sources will seriously affect the denitrification efficiency. To maintain a normal denitrification rate, a large amount of carbon source is required, which greatly increases the cost of landfill leachate treatment.

[0005] Carbon sources are divided into external carbon sources and internal carbon sources. Since external carbon sources such as sodium acetate and glucose are easily utilized by microorganisms, have high efficiency and wide applicability, they are widely used as external carbon sources in sewage treatment plants for addition. However, the addition of external carbon sources will increase the operating costs of the treatment plant and increase the sludge production. Subsequent treatment of these residual sludges still requires a lot of financial, human and material resources, which is not conducive to the long-term operation of the treatment plant. However, there are a large number of internal carbon sources in the residual sludge. After being treated with free nitrous acid, the sludge will be cracked to release macromolecular organic matter such as proteins and sugars. After hydrolysis and acidification, macromolecular organic matter will produce biodegradable organic matter and volatile fatty acids (VFA). These biodegradable organic matter and VFA can be used as carbon sources for denitrification. This can not only reduce or replace the addition of external carbon sources, but also effectively reduce the amount of residual sludge, which is a sustainable green technology.

[0006] Due to the presence of a large number of recalcitrant organic compounds in aged leachate, such as polycyclic aromatic hydrocarbons, halogenated organic compounds, and humic substances, and the high cost, high energy consumption, and production of concentrated liquid in the membrane treatment process, using membrane treatment for recalcitrant organic compounds is not an energy-saving and green treatment technology. Electrochemical treatment is a multifunctional process suitable for treating recalcitrant organic wastewater. Placing electrochemical treatment after biological treatment to degrade recalcitrant organic compounds in the biological treatment effluent will become a potentially cost-effective technology. Summary of the Invention

[0007] In view of the above technical problems, in order to solve the problems of low carbon-nitrogen ratio in aged landfill leachate, the need for additional large amounts of carbon sources during treatment, excessive production of excess sludge, and the presence of recalcitrant organic compounds in the biological treatment effluent, the present invention provides a device for treating aged landfill leachate using excess sludge as a carbon source. This device integrates various advanced treatment processes such as sludge anaerobic fermentation and denitrification, shortcut nitrification, and electrochemical treatment, aiming to efficiently treat aged landfill leachate, especially to remove complex organic pollutants and high-concentration ammonia nitrogen therein.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] A device for treating aged landfill leachate using excess sludge as a carbon source according to the present invention includes a feed tank, UASB anaerobic reactor I, UASB anaerobic reactor II, shortcut nitrification reactor, sedimentation tank, and electrochemical reaction tank. The feed tank is divided into a sludge storage area and a water inlet area, which are used to store excess sludge and aged landfill leachate respectively. The bottom of UASB anaerobic reactor I for sludge fermentation and denitrification is connected to the water inlet area of the feed tank through a water inlet pipe and to the sludge storage area of the feed tank through a sludge inlet pipe. One way at the upper part of sedimentation area I of UASB anaerobic reactor I is connected to the bottom feed port of UASB anaerobic reactor I through an internal circulation pipe I, and the other way is connected to the bottom feed port of UASB anaerobic reactor II through a water outlet pipe I. One way at the upper part of sedimentation area II of UASB anaerobic reactor II for methane production by fermentation is connected to the bottom feed port of UASB anaerobic reactor II through an internal circulation pipe II, and the other way is connected to the water inlet end of the shortcut nitrification reactor through a water outlet pipe II. The shortcut nitrification reactor is connected to the sedimentation tank through a water outlet pipe III. The sludge at the bottom of the sedimentation tank is connected to the water inlet end of the shortcut nitrification reactor through a sludge return pipe. One way of the upper part of the effluent is connected to the bottom of UASB anaerobic reactor I through a nitrification liquid return pipe to mix with the raw aged landfill leachate, and the other way is connected to the bottom of the electrochemical reaction tank through a water outlet pipe IV. The upper part of the electrochemical reaction tank finally discharges water through a water outlet pipe V. The shortcut nitrification reactor is connected to an air pump through an air pipeline for oxygen supply and aeration. The gases generated by UASB anaerobic reactor I and UASB anaerobic reactor II are respectively connected to gas cylinders through their respective gas collecting pipes and measured by gas meters.

[0010] Furthermore, a constant temperature insulation layer is provided on the outer periphery of the reaction zones of both the UASB anaerobic reactor I and the UASB anaerobic reactor II. The reaction zones are subjected to a constant temperature heat bath through the constant temperature insulation layer outside the reaction zones, and the temperature of the reaction zones is controlled at (35±2)°C by means of the constant temperature heat bath.

[0011] Furthermore, a three-phase separator I and a three-phase separator II are respectively provided on the upper parts of the reaction zones of the UASB anaerobic reactor I and the UASB anaerobic reactor II. The reaction products are separated into gas, liquid and solid through the three-phase separator I and the three-phase separator II; the three-phase separator I and the three-phase separator II are divided into a first separation zone and a second separation zone. The gas in the first separation zone is discharged through the side outlet pipe, and the gas in the second separation zone is discharged through the top gas pipe.

[0012] Furthermore, the pH of the short-cut nitrification reactor is controlled at 7.9 - 8.6, the dissolved oxygen concentration is controlled at 0.5 - 1.0 mg / L, the free ammonia concentration is controlled at 0.1 - 10 mg / L, and the temperature is controlled at (30±2)°C.

[0013] Furthermore, a water inlet pump, a sludge inlet pump, an internal circulation pump I, an internal circulation pump II, a sludge return pump and a nitrification liquid return pump are respectively provided on the water inlet pipe, the sludge inlet pipe, the internal circulation pipe I, the internal circulation pipe II, the sludge return pipe and the nitrification liquid return pipe.

[0014] Furthermore, an aeration device, a pH detector and a DO detector are provided on the short-cut nitrification reactor.

[0015] Furthermore, the electrochemical reaction cell is equipped with a regulated DC power supply, a tin dioxide anode and a graphite cathode to remove the hardly biodegradable organic matter and the remaining total nitrogen in the nitrification liquid of the sedimentation tank effluent through electrochemical treatment.

[0016] Furthermore, the landfill leachate is the leachate of aged landfills with a landfill time of more than 5 years, and the added sludge is the surplus sludge in the landfill leachate treatment process.

[0017] The beneficial effects of the present utility model are as follows:

[0018] 1. The utility model establishes a device for using excess sludge as an external carbon source for denitrification and removing the refractory biodegradable organic matter in aged landfill leachate. The aged landfill leachate with high-concentration ammonia nitrogen produces nitrite nitrogen after shortcut nitrification. The nitrite nitrogen flows back to the UASB anaerobic reactor I, and the free nitrous acid causes the excess sludge to crack and release macromolecular organic matter, which is hydrolyzed and acidified to generate small-molecular organic matter and VFA. The generated small-molecular organic matter and VFA can be used as carbon sources during denitrification and nitrogen removal. Then, through the fermentation of the UASB anaerobic reactor II, the biodegradable organic matter is completely removed. Finally, within the acceptable range of energy consumption, the refractory biodegradable organic matter and the remaining total nitrogen are removed through electrochemical treatment. It realizes the reduction, harmlessness, and resource utilization of excess sludge, and also removes the refractory biodegradable organic matter, which is a sustainable green and low-carbon technology. It has reference significance for problems such as low denitrification rate, excess sludge disposal, and difficulty in removing refractory biodegradable organic matter when treating aged landfill leachate, and has good application prospects.

[0019] 2. The utility model can effectively release the internal carbon source in excess sludge and can be efficiently used as a denitrification carbon source. The two-stage UASB anaerobic reactor and shortcut nitrification reactor used can efficiently remove biodegradable organic matter and ammonia nitrogen, greatly reducing the cost of the external carbon source in the biological nitrogen removal process.

[0020] 3. The utility model aims to widely apply excess sludge as an external carbon source to treat aged landfill leachate, with significant economic benefits. First, by using the internal carbon source in excess sludge, the addition amount of external carbon sources (such as sodium acetate and glucose) is reduced, and the operation cost of the treatment plant is lowered. Second, the production of excess sludge is effectively reduced, and it is converted into an available carbon source, improving the resource utilization rate. In addition, by combining multi-stage treatment processes, the removal rates of organic pollutants and ammonia nitrogen in aged landfill leachate are significantly increased, ensuring that the effluent quality meets the standards, reducing the environmental pollution risk, and making an important contribution to environmental protection. Finally, by comprehensively using anaerobic fermentation, denitrification, shortcut nitrification, and electrochemical treatment technologies, the treatment process is optimized, and the overall treatment cost is reduced, especially reducing the problems of high energy consumption, high cost, and more difficult treatment of concentrated liquid in membrane treatment technology. Description of the Drawings

[0021] Figure 1 It is the process flow diagram of the utility model.

[0022] In the figure: 1. Feed box, 2. UASB anaerobic reactor I, 3. UASB anaerobic reactor II, 4. Short-cut nitrification reactor, 5. Sedimentation tank, 6. Electrochemical reaction cell, 7. Sludge storage area, 8. Water inlet area, 9. Water inlet pipe, 10. Sludge inlet pipe, 11. Internal circulation pipe I, 12. Outlet pipe I, 13. Internal circulation pipe II, 14. Outlet pipe II, 15. Outlet pipe III, 16. Sludge return pipe, 17. Nitrification liquid return pipe, 18. Outlet pipe IV, 19. Outlet pipe V, 20. Air pump, 21. Gas collecting pipe I, 22. Gas collecting pipe II, 23. Gas meter, 24. Three-phase separator I, 25. First separation area, 26. Second separation area, 27. Feed water pump, 28. Sludge inlet pump, 29. Internal circulation pump I, 30. Internal circulation pump II, 31. Sludge return pump, 32. Nitrification liquid return pump, 33. pH detector, 34. DO detector, 35. Regulated DC power supply, 36. Tin dioxide anode, 37. Graphite cathode, 38. Three-phase separator II, 39. Sedimentation area I, 40. Sedimentation area II, 41. Constant temperature insulation layer I, 42. Constant temperature insulation layer II. Detailed implementation mode

[0023] The present utility model will be described in detail below in conjunction with the accompanying drawings and embodiments.

[0024] Embodiment: As Figure 1 shown, a device for treating aged landfill leachate with surplus sludge as a carbon source according to the present utility model sequentially includes a feed box 1, a UASB anaerobic reactor I 2, a UASB anaerobic reactor II 3, a short-cut nitrification reactor 4, a sedimentation tank 5 and an electrochemical reaction cell 6 along the water flow direction. The feed box 1 is divided into a sludge storage area 7 and a water inlet area 8, which are respectively used for storing surplus sludge and aged landfill leachate. The bottom of the UASB anaerobic reactor I 2 for sludge fermentation and denitrification is connected to the water inlet area 8 of the feed box 1 through a water inlet pipe 9 and to the sludge storage area 7 of the feed box 1 through a sludge inlet pipe 10. One way at the upper part of the sedimentation area I 39 of the UASB anaerobic reactor I 2 is connected to the bottom feed port of the UASB anaerobic reactor I 2 through an internal circulation pipe I 11, and the other way is connected to the bottom feed port of the UASB anaerobic reactor II 3 through an outlet pipe

[0025] I 12. One way at the upper part of the sedimentation area II 40 of the UASB anaerobic reactor II 3 for methane fermentation is connected to the bottom feed port of the UASB anaerobic reactor II 3 through an internal circulation pipe II 13, and the other way is connected to the water inlet end of the short-cut nitrification reactor 4 through an outlet pipe II 14. The short-cut nitrification reactor 4 is connected to the sedimentation tank 5 through an outlet pipe III 15. The sludge at the bottom of the sedimentation tank 5 is connected to the water inlet end of the short-cut nitrification reactor 4 through a sludge return pipe 16. One way of the upper part of the outlet water is connected to the bottom of the UASB anaerobic reactor I 2 through a nitrification liquid return pipe 17 to mix with the original aged landfill leachate water, and the other way is through an outlet pipe

[0026] Ⅳ18 is connected to the bottom of the electro-chemical reaction cell 6; the upper part of the electro-chemical reaction cell 6 finally discharges water through the water outlet pipe Ⅴ19; the shortcut nitrification reactor 4 is connected to an air pump 20 through an air pipeline for oxygen supply and aeration; the gases generated by the UASB anaerobic reactor Ⅰ2 and the UASB anaerobic reactor Ⅱ3 are respectively connected to a gas collecting bottle through their respective gas collecting pipes Ⅰ21 and gas collecting pipes Ⅱ22, and are measured by a gas meter 23.

[0027] The landfill leachate used in the present utility model is the leachate of aged landfills with a landfill time of more than 5 years, and the added sludge is the surplus sludge of the landfill leachate treatment process. The used aged landfill leachate has a low carbon-nitrogen ratio, a high ammonia-nitrogen concentration, and poor biodegradability; the used surplus sludge is the sludge produced by the activated sludge process and stored in the sludge storage tank for disposal. After cracking, it is hydrolyzed and fermented as a denitrification carbon source. The surplus sludge added to the UASB anaerobic reactor Ⅰ2 is cracked by the free nitrous acid contained in the shortcut nitrification liquid refluxed through the sedimentation tank 5 to release macromolecular organic matter. After hydrolysis and acidification of the macromolecular organic matter, it is used as an external carbon source required for denitrification to realize sludge fermentation and denitrification.

[0028] The UASB anaerobic reactor Ⅱ3 completely removes biodegradable organic matter through fermentation to produce methane. The shortcut nitrification reactor 4 mainly controls conditions such as DO, pH, and free ammonia (FA) to stably convert ammonia nitrogen into nitrite nitrogen, which is refluxed to the UASB anaerobic reactor Ⅰ2 to crack the sludge and carry out denitrification. The sedimentation tank 5 is used for separating mud and water. The sludge is refluxed to the inlet end of the shortcut nitrification reactor 4, and part of the nitrification liquid is refluxed, and the other part flows to the subsequent electro-chemical reaction cell 6. The electro-chemical reaction cell 6 degrades the refractory biodegradable organic matter and the remaining total nitrogen existing in the nitrification liquid through electro-chemical treatment.

[0029] Furthermore, a constant temperature insulation layer Ⅰ41 and a constant temperature insulation layer Ⅱ42 are respectively arranged on the outer periphery of the reaction zones of the UASB anaerobic reactor Ⅰ2 and the UASB anaerobic reactor Ⅱ3. The reaction zones are subjected to constant temperature hot bath through the constant temperature insulation layer Ⅰ41 and the constant temperature insulation layer Ⅱ42 outside the reaction zones, and the temperature of the reaction zones is controlled at (35±2)°C by using the constant temperature hot bath.

[0030] Furthermore, a three-phase separator Ⅰ24 and a three-phase separator Ⅱ38 are respectively arranged on the upper parts of the reaction zones of the UASB anaerobic reactor Ⅰ2 and the UASB anaerobic reactor Ⅱ3. The reaction products separate gas, liquid, and solid through the three-phase separator Ⅰ24 and the three-phase separator Ⅱ38. Both the three-phase separator Ⅰ24 and the three-phase separator Ⅱ38 are divided into a first separation zone 25 and a second separation zone 26. The gas in the first separation zone 25 is discharged through the side gas outlet pipe, and the gas in the second separation zone 26 is discharged through the top gas pipe to achieve a better separation effect. And the generated gas is connected to a gas collecting bottle through the gas collecting pipe Ⅰ21 and the gas collecting pipe Ⅱ22 and is measured by a gas meter 23.

[0031] Furthermore, an aeration device, a pH detector 33 and a DO detector 34 are provided on the short-cut nitrification reactor 4 for monitoring indexes such as DO, pH and temperature. The pH of the short-cut nitrification reactor 4 is controlled at 7.9 - 8.6, the dissolved oxygen (DO) concentration is controlled at 0.5 - 1.0 mg / L, the free ammonia (FA) concentration is controlled at 0.1 - 10 mg / L, and the temperature is controlled at (30 ± 2) °C to ensure stable short-cut nitrification and nitrite nitrogen yield.

[0032] Furthermore, a water inlet pump 27, a sludge inlet pump 28, an internal circulation pump I 29, an internal circulation pump II 30, a sludge return pump 31 and a nitrification liquid return pump 32 are respectively arranged on the water inlet pipe 9, the sludge inlet pipe 10, the internal circulation pipe I 11, the internal circulation pipe II 13, the sludge return pipe 16 and the nitrification liquid return pipe 17.

[0033] Furthermore, the electrochemical reaction cell 6 is equipped with a regulated DC power supply 35, a tin dioxide anode 36 and a graphite cathode 37 to remove the hardly biodegradable organic matter and the remaining total nitrogen in the nitrification liquid of the sedimentation tank effluent through electrochemical treatment.

[0034] The UASB anaerobic reactor I 2 and the UASB anaerobic reactor II 3 of the present utility model use anaerobic nitrification sludge as the bacterial source, and aged landfill leachate and excess sludge are added into the feed tank 1. The raw leachate water is continuously fed, and the excess sludge is added into the reactor once every 24 hours. The short-cut nitrification reactor 4 uses aerobic sludge as the bacterial source to continuously treat the influent water, converting the ammonia nitrogen therein into nitrite nitrogen, thereby saving about 20% of the aeration volume, and about 40% of the organic carbon source can be saved during the denitrification process.

[0035] To ensure the stable operation of the system, the entire device needs to be monitored, the corresponding data is measured every day, and the system is regulated to maintain its operation under the optimal conditions.

[0036] The specific control method for starting the UASB anaerobic reactor I 2 and the UASB anaerobic reactor II 3 of the present utility model is as follows:

[0037] This example relates to the start-up of the UASB anaerobic reactor I 2 and the UASB anaerobic reactor II 3. As Figure 1As shown, the outlet pipe II 14 is directly used as the outlet pipe, and the nitrification liquid reflux pipe 17 and subsequent devices are not connected. The activated sludge inoculated in the UASB anaerobic reactor I 2 and the UASB anaerobic reactor II 3 is the anaerobic nitrification sludge in the landfill leachate treatment process. The leachate is diluted 3 times with tap water, and nitrite nitrogen with an appropriate concentration is added to simulate the dilution of the original leachate by the nitrification liquid reflux and the nitrite nitrogen brought by the reflux. Initially, nitrite nitrogen with a concentration of 200 mg / L is added to the diluted leachate, and the mixed liquid is filled into the feed tank 1 and enters the water inlet area 8. A certain amount of excess sludge is regularly added to the UASB anaerobic reactor I 2 from the sludge storage area 7 every 24 h. Start the constant temperature water bath to maintain a constant temperature, and control the reaction zone temperature at (35 ± 2) °C. In the initial stage, increase the circulation flow rates of the internal circulation pump I 29 and the internal circulation pump II 30 to ensure sufficient mixing of the mud and water. When the sludge is fully adapted to the water quality at this time and the gas production gradually increases, the internal circulation flow rate can be reduced to ensure 3 times the influent flow rate. When the COD removal rate in the UASB anaerobic reactor II 2 reaches 75% and the nitrite nitrogen removal rate reaches over 85%, further increase the nitrite nitrogen concentration in the influent and increase the excess sludge dosage until the nitrite nitrogen concentration is 600 mg / L and this removal rate is still maintained, indicating the successful startup of the UASB anaerobic reactor I 2 and the UASB anaerobic reactor II 3. The UASB anaerobic reactor I 2 and the UASB anaerobic reactor II 3 of this project have been successfully started after 90 days of operation. The influent and effluent water quality of the UASB anaerobic reactor I 2 and the UASB anaerobic reactor II 3 are shown in Table 1.

[0038] Table 1 Influent and Effluent Water Quality of the Reaction

[0039]

[0040] The specific control method for starting the short-cut nitrification reactor 4 of the present utility model is as follows:

[0041] This example relates to the startup of the short-cut nitrification reactor 4. As Figure 1 shown, the outlet pipe II is used as the inlet pipe of the short-cut nitrification reactor 4, and the nitrification liquid reflux pipe 17 is closed. The device discharges water from the outlet pipe IV 18. The inoculated activated sludge is the aerobic activated sludge in the landfill leachate treatment process, and the inoculated sludge concentration is (5000 ± 500) mg MLSS / L. The leachate is diluted with tap water. Initially, it is diluted to an ammonia nitrogen concentration of 250 mg / L, and the diluted leachate is adjusted with NaHCO 3After adjusting the pH to 8.4, it is used as the influent. Start the air pump 20, control the aeration pipeline of the reactor to aerate through the gas flowmeter, and control the DO at about 0.8 mg / L to carry out shortcut nitrification of the ammonia nitrogen in the landfill leachate. At the same time, maintain the temperature of the mixed liquid of mud and water in the shortcut nitrification reactor 4 at (30±2) °C, adjust the ammonia nitrogen concentration at a certain temperature and pH, so that the FA concentration is 0.1-10 mg / L. Operate the shortcut nitrification reactor 4 under the above conditions of DO, pH, temperature and FA concentration. When the accumulation rate of nitrite nitrogen reaches more than 90%, gradually reduce the dilution multiple of the landfill leachate so that the influent ammonia nitrogen concentration remains at this accumulation rate when it reaches 750 mg / L. This indicates that the shortcut nitrification reactor 4 is successfully started. After 100 days of operation of the shortcut nitrification reactor 4 in this project, the start-up is successfully achieved. The influent and effluent water quality of the shortcut nitrification reactor 4 are shown in Table 2.

[0042] Table 2 Influent and effluent water quality of the reaction

[0043]

[0044] The specific control method of the present utility model is as follows:

[0045] This example relates to the control method of the utility model device. As Figure 1 shown, after the UASB anaerobic reactor I 2, the UASB anaerobic reactor II 3 and the shortcut nitrification reactor 4 are successfully started, they are operated in series with the electro-chemical reaction cell 6. Load the original landfill leachate into the water inlet area 8 of the feed tank 1 for water inlet. After sludge fermentation and denitrification in the UASB anaerobic reactor I 2, it flows into the UASB anaerobic reactor II 3. After fermentation in the UASB anaerobic reactor II 3, the biodegradable organic matter is completely removed, and then it flows into the shortcut nitrification reactor 4. After shortcut nitrification in the shortcut nitrification reactor 4, the effluent is precipitated in the sedimentation tank 5, and the sludge is refluxed to the water inlet end of the shortcut nitrification reactor 4. A part of the effluent is refluxed to the UASB anaerobic reactor I 2 for denitrification, and the other part flows into the electro-chemical reaction cell 6 for final nitrogen removal and removal of refractory biodegradable organic matter. The specific control methods such as pH and temperature in this example are the same as the optimal control conditions during the above start-up. The electro-chemical reaction cell uses a tin dioxide anode and a graphite cathode, and adjusts the voltage so that the current density is 10 mA / cm 2 . The influent and effluent water quality are shown in Table 3.

[0046] Table 3 Influent and effluent water quality of the reaction

[0047]

[0048] The components not described in detail in this application are all conventional existing technologies and will not be elaborated here.

[0049] It is understandable that the above specific description of the present utility model is only for explaining the present utility model and is not limited to the technical solutions described in the embodiments of the present utility model. Those of ordinary skill in the art should understand that the present utility model can still be modified or equivalently replaced to achieve the same technical effect; as long as the use requirements are met, they are all within the protection scope of the present utility model.

Claims

1. A device for treating old landfill leachate using excess sludge as a carbon source, characterized in that: The invention comprises a feed box, an anaerobic UASB reactor I, an anaerobic UASB reactor II, a short-range nitrification reactor, a sedimentation tank and an electrochemical reaction tank, wherein the feed box is divided into a sludge storage area and a water inlet area, which are respectively used to store residual sludge and leachate from aged garbage; the bottom of the anaerobic UASB reactor I used for sludge fermentation and denitrification is connected to the water inlet area of ​​the feed box through a water inlet pipe, and is connected to the sludge storage area of ​​the feed box through a sludge inlet pipe; the upper part of the sedimentation area I of the anaerobic UASB reactor I is connected to the bottom feed port of the anaerobic UASB reactor I through an internal circulation pipe I, and the other part is connected to the bottom feed port of the anaerobic UASB reactor II through an outlet pipe I; the upper part of the sedimentation area II of the anaerobic UASB reactor II used for fermentation and methane production is connected to the UASB reactor I through an internal circulation pipe II through a water outlet pipe I; the upper part of the sedimentation area II of the anaerobic UASB reactor II ... The bottom feed port of SB anaerobic reactor II is connected, and the other route is connected to the water inlet of short-range nitrification reactor through outlet pipe II; the short-range nitrification reactor is connected to the sedimentation tank through outlet pipe III; the sludge at the bottom of the sedimentation tank is connected to the water inlet of the short-range nitrification reactor through the sludge return pipe, and the upper effluent is connected to the bottom of UASB anaerobic reactor I through the nitrification liquid return pipe, mixed with the raw water of old garbage leachate, and the other route is connected to the bottom of the electrochemical reaction tank through outlet pipe IV; the upper part of the electrochemical reaction tank is finally effluent through outlet pipe V; the short-range nitrification reactor is connected to the air pump for oxygen aeration through an air pipeline; the gases produced by UASB anaerobic reactor I and UASB anaerobic reactor II are connected to the gas collecting bottles through their respective gas collecting pipes, and are measured by gas meters.

2. The device for treating old landfill leachate using excess sludge as a carbon source according to claim 1, characterized in that: The outer periphery of the reaction zone of the UASB anaerobic reactor I and the UASB anaerobic reactor II is provided with a constant temperature insulation layer, and the reaction zone is subjected to a constant temperature heat bath through the constant temperature insulation layer outside the reaction zone, and the temperature of the reaction zone is controlled at (35±2)°C by the constant temperature heat bath.

3. The device for treating old landfill leachate using excess sludge as a carbon source according to claim 1, characterized in that: The upper part of the reaction zone of the UASB anaerobic reactor I and the UASB anaerobic reactor II is respectively provided with a three-phase separator I and a three-phase separator II, and the reaction product is separated into gas, liquid and solid by the three-phase separator I and the three-phase separator II; the three-phase separator I and the three-phase separator II are divided into a first separation zone and a second separation zone, the gas in the first separation zone is discharged through the side outlet pipe, and the gas in the second separation zone is discharged through the top air pipe.

4. The device for treating old landfill leachate using excess sludge as a carbon source according to claim 1, characterized in that: The pH of the short-range nitrification reactor is controlled at 7.9-8.6, the dissolved oxygen concentration is controlled at 0.5-1.0 mg / L, the free ammonia concentration is controlled at 0.1-10 mg / L, and the temperature is controlled at (30±2)°C.

5. The device for treating old landfill leachate using excess sludge as a carbon source according to claim 1, characterized in that: A water inlet pump, a mud inlet pump, an internal circulation pump I, an internal circulation pump II, a sludge return pump and a nitrification liquid return pump are respectively arranged on the water inlet pipe, the mud inlet pipe, the internal circulation pipe I, the internal circulation pipe II, the sludge return pipe and the nitrification liquid return pipe.

6. The device for treating old landfill leachate using excess sludge as a carbon source according to claim 1, characterized in that: The short-range nitrification reactor is provided with an aeration device, a pH detector and a DO detector.

7. The device for treating old landfill leachate using excess sludge as a carbon source according to claim 1, characterized in that: The electrochemical reaction cell is equipped with a voltage-stabilized DC power supply, a tin dioxide anode and a graphite cathode, so as to remove the difficult-to-biodegrade organic matter and the remaining total nitrogen in the nitrified liquid of the sedimentation tank effluent through electrochemical treatment.

8. The device for treating old landfill leachate using excess sludge as a carbon source according to claim 1, characterized in that: The landfill leachate is aged landfill leachate that has been landfilled for more than 5 years, and the added sludge is residual sludge in the landfill leachate treatment process.

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