A method and system for treating landfill leachate

Abstract

The present invention relates to a method for treating landfill leachate. The steps include: mixing nitrogen-containing landfill leachate and activated sludge and then introducing the mixture into a denitrification tank. Under the condition of inhibiting nitrous oxide reduction, nitrite in the mixture generates nitrous oxide gas dissolved in the sewage under the action of denitrifying bacteria in the denitrification tank; then introducing it into an ammonification tank for gas-liquid separation to collect nitrous oxide gas; and obtaining the sewage after ammonification treatment under the ammonification action of ammonifying functional bacteria in the ammonification tank; further introducing it into a nitrification tank to obtain sewage containing nitrite under the action of nitrosifying bacteria; refluxing to the denitrification tank for cyclic reaction; and then introducing it into a separator for separation to obtain an effluent that can be discharged and sewage that needs to be recycled for treatment. The present invention also relates to a treatment system capable of cooperating with the above treatment method. It changes the existing treatment process of directly discharging nitrogen into the air, turns to collecting nitrous oxide gas, shortens the treatment time, reduces greenhouse gas emissions, and realizes energy recovery.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and particularly relates to a treatment method and a treatment system for landfill leachate. Background Art

[0002] At present, sanitary landfill is still a commonly used method for domestic waste treatment in China, which has the characteristics of low cost, large disposal capacity, simple operation, etc., and is widely used. After domestic waste is anaerobically fermented and degraded, landfill gas and landfill leachate will be generated. The landfill gas can be collected and used for biogas power generation or flare combustion, while the landfill leachate will be collected and treated in a sewage treatment plant.

[0003] Landfill leachate has the characteristics of high organic matter, high ammonia nitrogen, high salinity, etc. Generally, biological nitrogen removal technology is used for treatment. The organic nitrogen and ammonia nitrogen in the sewage are subjected to ammonification, nitrification reaction and denitrification reaction, and finally converted into nitrogen gas and discharged into the air. The reaction steps are in turn NH4 + →NO2 - →NO3 - →NO2 - →NO→N2O→N2. However, the overall time of this reaction is relatively long, and a large amount of carbon source needs to be additionally supplemented during this process, resulting in high costs. Moreover, the greenhouse gas N2O generated during the process will be mixed with N2 and discharged into the air, leading to an exacerbation of global warming.

[0004] The present invention hopes to propose a treatment method and a treatment system for landfill leachate. Without the need to supplement a large amount of reaction raw materials such as carbon source and nitrous oxide reductase, the generation of N2 is avoided, and N2O gas is directly generated as the goal. The N2O is collected and recycled to a biogas power plant as a power generation raw material. While completing the treatment of landfill leachate, the emission reduction of N2O waste gas and energy recovery are realized, changing the traditional treatment method of directly discharging gas into the atmosphere, which has great environmental protection significance. Summary of the Invention

[0005] To overcome the shortcomings and deficiencies of the prior art, change the treatment method of directly discharging gas into the atmosphere, recover N2O gas that can be used as energy, reduce environmental pollution, and optimize the treatment method of landfill leachate. The primary object of the present invention is to provide a treatment method for landfill leachate.

[0006] Another object of the present invention is to provide a treatment system for landfill leachate, which can be applied to the above treatment method for landfill leachate.

[0007] The first aspect of the present invention discloses a treatment method for landfill leachate, and the method includes the following steps:

[0008] Mix the nitrogen-containing landfill leachate and activated sludge and introduce them into the denitrification tank for reaction. The reaction process is as follows: under the condition of inhibiting nitrous oxide reduction, nitrite in the mixture is converted into nitrous oxide gas dissolved in the sewage under the action of denitrifying bacteria in the denitrification tank, and the sewage after denitrification treatment is obtained;

[0009] Introduce the sewage after denitrification treatment into the ammonification tank for gas-liquid separation, separate and collect the nitrous oxide gas in the sewage after denitrification treatment; and obtain the sewage after ammonification treatment under the ammonification action of ammonifying functional bacteria in the ammonification tank;

[0010] Introduce the sewage after ammonification treatment into the nitrification tank for reaction, and obtain the sewage containing nitrite under the action of nitrosifying bacteria in the nitrification tank for the sewage after ammonification treatment;

[0011] Return the sewage containing nitrite to the denitrification tank for cyclic treatment to provide nitrite raw materials for the denitrification tank;

[0012] The sewage after cyclic treatment is introduced into a separator for separation and detection. If the detection result meets the discharge requirements, the separated effluent is discharged; otherwise, the sewage that needs to be recycled is returned to the denitrification tank for cyclic treatment.

[0013] Furthermore, the method for providing the condition of inhibiting N2O reduction includes controlling the hydraulic retention time of the denitrification tank within the range of 30 - 45 min.

[0014] Furthermore, the method for providing the condition of inhibiting N2O reduction includes inhibiting the activity of nitrous oxide reductase.

[0015] Furthermore, the method for inhibiting the activity of nitrous oxide reductase is any one or more of the high salinity inhibition method, the high dissolved oxygen inhibition method, and the low carbon-nitrogen ratio inhibition method;

[0016] Among them: the high salinity inhibition method is to control the salinity within the range of 7000 - 9000 mg / L (calculated as NaCl); the high dissolved oxygen inhibition method is to control the dissolved oxygen concentration within the range of 0.2 - 0.4 mg / L; the low carbon-nitrogen ratio inhibition method is to supplement carbon sources to control the ratio of the biochemical oxygen demand to ammonia nitrogen content of the influent within the range of 1.05 - 1.55.

[0017] Furthermore, the method for providing the condition of inhibiting N2O reduction includes using denitrifying bacteria without a nitrous oxide reductase system.

[0018] Furthermore, the hydraulic retention time of the ammonification tank is controlled within the range of 60 - 150 min, and the dissolved oxygen concentration is controlled within the range of 1.0 - 2.0 mg / L.

[0019] Furthermore, the dissolved oxygen concentration in the nitrification tank is controlled within the range of 0.8 - 1.5 mg / L, and the reflux ratio is controlled within the range of 20 - 35.

[0020] The second aspect of the present invention discloses a treatment system for landfill leachate, which can be applied to any of the landfill leachate treatment methods in the first aspect of the present invention. The treatment system includes: a denitrification tank, an ammonification tank, a nitrification tank, and a separator;

[0021] The denitrification tank is provided with a water inlet, a carbon source inlet, a circulating water inlet, a first dissolved oxygen meter, an oxidation-reduction potential, and a sewage output end after denitrification treatment; a water inlet flow meter is provided at the water inlet, and a circulating flow meter is provided at the circulating water inlet; the first dissolved oxygen meter is used to detect the concentration of dissolved oxygen in the denitrification tank; the oxidation-reduction potential is used to monitor the denitrification reaction situation;

[0022] The ammonification tank is provided with a sewage input end after denitrification treatment, a nitrous oxide output port, a sewage output end after ammonification treatment, an aeration device, a ventilation system, and a second dissolved oxygen meter; the aeration device is arranged at the bottom of the ammonification tank and is used to separate N2O gas from the water body; the nitrous oxide output port is arranged at the top of the ammonification tank and is coordinated with the ventilation system to extract N2O gas out of the ammonification tank; the second dissolved oxygen meter is used to detect the concentration of dissolved oxygen in the ammonification tank;

[0023] The nitrification tank is provided with a sewage input end after ammonification treatment, a sewage output end containing nitrite, a third dissolved oxygen meter, and a waste liquid output end; the third dissolved oxygen meter is used to detect the concentration of dissolved oxygen in the nitrification tank;

[0024] The separator is provided with a waste liquid input end, a reflux end, and a liquid output end;

[0025] The sewage output end after denitrification treatment is connected to the sewage input end after denitrification treatment, the sewage output end after ammonification treatment is connected to the sewage input end after ammonification treatment, the waste liquid output end is connected to the waste liquid input end, and the sewage output end containing nitrite converges with the reflux end and is connected to the circulating water inlet.

[0026] Furthermore, the aeration device includes any one of a jet aeration device or a pure oxygen aeration device.

[0027] Furthermore, the treatment system further includes a pH meter and a thermometer for monitoring reaction parameters.

[0028] In a landfill leachate treatment method, the mechanism includes the following aspects:

[0029] (1) After the landfill leachate is mixed with activated sludge, under aerobic conditions, the inorganic nitrogen therein can react with aerobic autotrophic microorganisms to generate NH4 + , and then oxidize NH4 + to NO2- , the reaction step is NH4 + →NO2 - ;

[0030] There are denitrifying bacteria in the denitrification tank. Under the condition of inhibiting N2O reduction, NO2 in the mixture - is converted into NO under the action of nitrite reductase in denitrifying bacteria, and NO is converted into N2O under the action of nitric oxide reductase in denitrifying bacteria. At this time, N2O dissolves in the sewage and is no longer reduced to N2.

[0031] (2) The sewage after denitrification treatment is subjected to gas-liquid separation in the ammonification tank to separate and collect N2O. For example, the air flow is violently disturbed by an aeration device, and N2O is carried out of the liquid by the bubbles generated by aeration to achieve gas-liquid separation, and then most of the N2O is evacuated by an exhaust system. The nitrogen-containing organic matter in the remaining sewage is further decomposed and converted into NH4 + under the metabolism of ammonifying functional bacteria, and the sewage after ammonification treatment is obtained.

[0032] (3) The sewage after ammonification treatment reacts with nitrosifying bacteria in the nitrification tank to be converted into NO2 - , and the sewage containing NO2 - is obtained.

[0033] (4) The sewage containing NO2 - is recycled to the denitrification tank for cyclic treatment. The sewage after cyclic treatment is introduced into a separator for separation and detection. If the detection result meets the discharge requirements, the separated effluent is discharged; otherwise, the sewage to be recycled is returned to the denitrification tank for cyclic treatment.

[0034] The present invention has achieved the following beneficial effects:

[0035] (1) The treatment method of landfill leachate disclosed by the present invention utilizes short-cut nitrification reaction to oxidize NH4 + into NO2 - , and then uses the denitrification tank to control the denitrification process of landfill leachate, oxidize NO2 - into N2O and then stop the reaction, inhibit the reduction of N2O, so that it is no longer reduced to N2 in the system, that is, the original denitrification process steps NO3 - →NO2 - →NO→N2O→N2 are shortened to NH4 + →NO2 - →NO→N2O.

[0036] This treatment method mixes landfill leachate with activated sludge, so that the inorganic nitrogen therein can react with aerobic autotrophic microorganisms to generate NH4 +, achieving the purpose of saving reaction time and shortening the reaction process.

[0037] (2) The present invention also completes gas-liquid separation in the ammoniation tank, collecting most of the N2O gas generated in the system in advance. In actual measurement, 80% of the N2O gas generated in the system can be collected in this step; the remaining nitrogen-containing substances are recycled until the effluent meets the wastewater discharge standard, realizing the harmless treatment of landfill leachate. Moreover, the collected N2O gas basically contains no N2, and the impurities can be simply treated with an adsorbent and then used as fuel for a biogas power plant or other purposes, achieving the purpose of energy recovery. The present invention changes the traditional gas treatment method of directly discharging gas into the atmosphere, avoiding potential air pollution hazards. While completing the treatment of landfill leachate, it realizes the reduction of N2O waste gas emissions and energy recovery, having great environmental protection significance. Description of the Drawings

[0038] Figure 1 is a schematic diagram of the steps of a method for treating landfill leachate according to one embodiment of the present invention;

[0039] Figure 2 is a schematic diagram of the structure of a treatment system for landfill leachate according to one embodiment of the present invention.

[0040] Description of the reference numerals: 1 - denitrification tank, 2 - ammoniation tank, 3 - nitrification tank, 4 - separator, 5 - water inlet, 6 - carbon source inlet, 7 - circulating water inlet, 8 - output end of the sewage after denitrification treatment, 9 - input end of the sewage after denitrification treatment, 10 - nitrous oxide output port, 11 - output end of the sewage after ammoniation treatment, 12 - aeration device, 13 - input end of the sewage after ammoniation treatment, 14 - output end of the sewage containing nitrite, 15 - waste liquid output end, 16 - waste liquid input end, 17 - reflux end, 18 - liquid outlet end, 19 - exhaust system, 20 - liquid delivery pipeline. Detailed Embodiments

[0041] The following further describes the present invention with reference to specific embodiments. However, the implementation manners of the present invention are not limited thereto. It should be understood that in the following described embodiments, it is only for illustrative purposes and not for limitation, and does not intend to limit the scope of the claims of the present invention. All the original materials designed in the embodiments can be obtained from commercial channels.

[0042] Specific details such as specific internal procedures and technologies proposed in the following embodiments are also for a thorough understanding of the embodiments of the present invention. Those skilled in the art should understand that the present invention can also be implemented in other embodiments without these specific details. In addition, the following embodiments have omitted the detailed descriptions of well-known systems, devices, circuits, and methods to avoid unnecessary details from interfering with the description of the present invention.

[0043] Reference Figure 1 , a first aspect of the present invention discloses a method for treating landfill leachate, the method comprising the following steps:

[0044] Mix the nitrogen-containing landfill leachate and activated sludge and introduce them into a denitrification tank for reaction. The reaction process is: under the condition of inhibiting N2O reduction, NO2 in the mixture - Under the action of denitrifying bacteria in the denitrification tank, it generates N2O gas dissolved in the sewage, and the sewage after denitrification treatment is obtained;

[0045] Pass the sewage after denitrification treatment into an ammonification tank for gas-liquid separation, separate and collect the N2O gas in the sewage after denitrification treatment; and obtain the sewage after ammonification treatment under the ammonification action of ammonifying functional bacteria in the ammonification tank;

[0046] Pass the sewage after ammonification treatment into a nitrification tank for reaction, so that the sewage after ammonification treatment is obtained containing NO2 under the action of nitrite bacteria in the nitrification tank - sewage;

[0047] Return the sewage containing NO2 - to the denitrification tank for cyclic treatment, and provide NO2 for the denitrification tank - raw material;

[0048] The sewage after cyclic treatment is introduced into a separator for separation and detection. If the detection result meets the discharge requirements, the separated effluent is discharged; otherwise, the sewage to be recycled is returned to the denitrification tank for cyclic treatment.

[0049] The method for treating landfill leachate disclosed by the present invention utilizes the short-cut nitrification reaction to oxidize NH4 + into NO2 - , and then uses the denitrification tank to control the denitrification process of landfill leachate, oxidize NO2 - into N2O and stop the reaction, inhibit N2O reduction, so that it is no longer reduced to N2 in the system, that is, the original denitrification process steps NO3 - →NO2 - →NO→N2O→N2 are shortened to NH4 + →NO2 - →NO→N2O.

[0050] The present invention also completes gas-liquid separation in the ammoniation tank, collecting most of the N2O gas generated in the system in advance. In actual measurement, 80% of the N2O gas generated in the system can be collected in this step; the remaining nitrogen-containing substances are recycled until the effluent meets the wastewater discharge standard, realizing the harmless treatment of landfill leachate. Moreover, the collected N2O gas basically contains no N2, and the impurities in it can be used as fuel for biogas power plants or other purposes after simple treatment with adsorbents, achieving the purpose of energy recovery. The present invention changes the traditional gas treatment method of directly discharging gas into the atmosphere, avoiding potential air pollution hazards, achieving the reduction of N2O waste gas emissions and energy recovery while completing the treatment of landfill leachate, and having great environmental protection significance.

[0051] As an alternative embodiment, the method for providing the conditions for inhibiting N2O reduction includes controlling the hydraulic retention time of the denitrification tank within the range of 30 to 45 minutes.

[0052] By controlling the hydraulic retention time of the denitrification tank within the range of 30 to 45 minutes, the reaction duration of the sewage in the denitrification tank is controlled, so that N2O is introduced into the next reaction tank before it is reduced, achieving the effect of inhibiting N2O reduction. Moreover, the reaction time is reduced by 25 to 50% compared with the traditional denitrification treatment step, improving the sewage treatment efficiency.

[0053] As an alternative embodiment, the method for providing the conditions for inhibiting N2O reduction includes inhibiting the activity of nitrous oxide reductase.

[0054] Nitrous oxide reductase is a key enzyme that regulates the generation and accumulation of N2O in the denitrification process. By inhibiting the activity of nitrous oxide reductase, the reduction of N2O to N2 can be inhibited, thereby inhibiting the generation of N2.

[0055] As an alternative embodiment, the method for inhibiting the activity of nitrous oxide reductase is any one or more of the high salinity inhibition method, the high dissolved oxygen inhibition method, and the low carbon-nitrogen ratio inhibition method;

[0056] Among them: in the high salinity inhibition method, the salinity is controlled within the range of 7000 to 9000 mg / L (calculated as NaCl); in the high dissolved oxygen inhibition method, the dissolved oxygen concentration is controlled within the range of 0.2 to 0.4 mg / L; in the low carbon-nitrogen ratio inhibition method, a carbon source is supplemented to control the ratio of the biochemical oxygen demand and ammonia nitrogen content of the influent within the range of 1.05 to 1.55.

[0057] By increasing the salinity, the subsequent reaction of denitrifying bacteria can be terminated. At the same time, high salinity has an inhibitory effect on the activity of nitrous oxide reductase. By controlling the salinity within the range of 7000 to 9000 mg / L (calculated as NaCl), the denitrifying bacteria can be controlled to convert NO2 -The reduction to N2O stops, and the nitrous oxide reductase is inhibited from reducing N2O to N2. It also has the ability to treat high-salinity sewage. By controlling the dissolved oxygen concentration within the range of 0.2-0.4 mg / L, the nitrous oxide reductase can be inhibited due to the inability to obtain electron donors. The increase of molecular oxygen in the system can also inhibit the synthesis of nitrous oxide reductase. At the same time, biological denitrification requires anaerobic conditions. Increasing the dissolved oxygen concentration can further inhibit the generation of N2 by denitrification. By controlling the ratio of the influent biochemical oxygen demand and the ammonia nitrogen content within the range of 1.05-1.55, the nitrous oxide reductase with a lower affinity for organic electron donors can be inhibited due to the inability to obtain electron donors. While saving the carbon source for the denitrification reaction, the effect of inhibiting the activity of nitrous oxide reductase can also be obtained.

[0058] As an optional embodiment, the method for providing the condition for inhibiting N2O reduction includes using denitrifying bacteria that do not have a nitrous oxide reductase system.

[0059] The products of denitrification can be directly controlled by using denitrifying bacteria that do not have a nitrous oxide reductase system and can only produce N2O, thereby controlling the generation of N2 in the system.

[0060] As an optional embodiment, the hydraulic retention time of the ammonia treatment tank is controlled within the range of 60 to 150 minutes, and the dissolved oxygen concentration is controlled within the range of 1.0 to 2.0 mg / L.

[0061] The main function of the ammoniation tank is to blow out N2O, control the hydraulic retention time within the range of 60-150 minutes, and the dissolved oxygen concentration within the range of 1.0-2.0 mg / L, which can not only ensure that there is enough time to blow out the gas, but also allow the large molecular organic matter that remains after denitrification treatment to be further decomposed in the ammoniation tank. At this point, the organic nitrogen in the water body is completely decomposed into inorganic nitrogen.

[0062] As an optional embodiment, the dissolved oxygen concentration in the nitrification tank is controlled within the range of 0.8-1.5 mg / L, and the reflux ratio is controlled within the range of 20-35.

[0063] Among them, the dissolved oxygen concentration in the nitrification tank is controlled within the range of 0.8-1.5 mg / L, which can reduce the concentration of NH4 + Oxidized to NO2 - , and then limit the nitrification reaction to only NO2 - -N stage, resulting in a large amount of NO2 - -N accumulation. Controlling the reflux ratio within the range of 20 to 35 is beneficial to denitrification and reflux dissolved oxygen.

[0064] Reference Figure 2, the second party of the present invention discloses a treatment system for landfill leachate, including: a denitrification tank 1, an ammonification tank 2, a nitrification tank 3, and a separator 4;

[0065] The denitrification tank 1 is provided with a water inlet 5, a carbon source inlet 6, a circulating water inlet 7, a first dissolved oxygen meter (not shown in the figure), an oxidation-reduction potential (not shown in the figure), and a sewage output end 8 after denitrification treatment; a water inlet flow meter (not shown in the figure) is provided at the water inlet 5, and a circulating water flow meter (not shown in the figure) is provided at the circulating water inlet 7; the oxidation-reduction potential (not shown in the figure) is used to monitor the denitrification reaction situation;

[0066] The ammonification tank 2 is provided with a sewage input end 9 after denitrification treatment, a nitrous oxide output port 10, a sewage output end 11 after ammonification treatment, an aeration device 12, an exhaust system 19, and a second dissolved oxygen meter (not shown in the figure); the aeration device 12 is arranged at the bottom of the ammonification tank 2 and is used to separate N2O gas from the water body; the nitrous oxide output port 10 is arranged at the top of the ammonification tank 2 and is matched with the exhaust system 19 to extract N2O gas out of the ammonification tank 2; the second dissolved oxygen meter (not shown in the figure) is used to detect the concentration of dissolved oxygen in the ammonification tank 2;

[0067] The nitrification tank 3 is provided with a sewage input end 13 after ammonification treatment, a sewage output end 14 containing nitrite, a third dissolved oxygen meter (not shown in the figure), and a waste liquid output end 15; the third dissolved oxygen meter (not shown in the figure) is used to detect the concentration of dissolved oxygen in the nitrification tank 3;

[0068] The separator 4 is provided with a waste liquid input end 16, a reflux end 17, and a liquid output end 18;

[0069] The sewage output end 8 after denitrification treatment is communicated with the sewage input end 9 after denitrification treatment, the sewage output end 11 after ammonification treatment is communicated with the sewage input end 13 after ammonification treatment, the waste liquid output end 15 is communicated with the waste liquid input end 16, and the sewage output end 14 containing nitrite converges with the reflux end 17 and is communicated with the circulating water inlet 7.

[0070] The treatment system for landfill leachate disclosed by the present invention is simple to operate. Through multiple monitoring devices such as the first dissolved oxygen meter (not shown in the figure), the second dissolved oxygen meter (not shown in the figure), the third dissolved oxygen meter (not shown in the figure), the oxidation-reduction potential (not shown in the figure), the water inlet flow meter (not shown in the figure), and the circulating water flow meter (not shown in the figure), the chemical reaction conditions in different treatment tanks of the treatment system are detected. By adjusting the equipment, the hydraulic retention time, the concentration of dissolved oxygen, and the ratio of the influent biochemical oxygen demand to the ammonia nitrogen content can be controlled, and then the action of denitrifying bacteria and the activity of nitrous oxide reductase can be controlled, so as to achieve the effect of controlling the denitrification reaction, ammonification reaction, and nitrification reaction processes.

[0071] Furthermore, through the aeration device at the bottom of the ammoniation tank in cooperation with the top ventilation system, the present invention can bring N2O out of the liquid to the nitrous oxide outlet, collecting most of the N2O gas generated in the system in advance. In actual measurement, 80% of the N2O gas generated in the system can be collected through the nitrous oxide outlet 10, and the collected N2O gas basically does not contain N2. The impurities therein can be simply treated with an adsorbent and then used as fuel for a biogas power plant or for other purposes. Different from the practice of directly discharging N2 in traditional treatment equipment, the treatment system disclosed in the present invention can achieve the reduction of N2O waste gas and energy recovery while completing the treatment of landfill leachate, which has great environmental protection significance.

[0072] In a specific embodiment, the aeration device 12 includes either a jet aeration device or a pure oxygen aeration device.

[0073] In a specific application, the treatment system further includes a pH meter (not shown in the figure) and a thermometer (not shown in the figure) for monitoring reaction parameters.

[0074] It should be noted that in the system of the present invention, a nitrous oxide electrode (not shown in the figure) can also be added to the ventilation system 19 at the top of the ammoniation tank 2 to detect the concentration of the extracted N2O gas, so as to further monitor the progress of the reaction and the recovery amount of N2O gas.

[0075] Refer to Figure 1 , which shows a schematic diagram of the steps of a method for treating landfill leachate according to one embodiment of the present invention, including the following steps:

[0076] Mix the nitrogen-containing landfill leachate and activated sludge and introduce them into the denitrification tank 1;

[0077] Under the condition of inhibiting N2O reduction, NO2 in the mixture - Complete the denitrification reaction under the action of denitrifying bacteria in the denitrification tank 1 to generate N2O gas, and obtain the sewage after denitrification treatment;

[0078] Introduce the sewage after denitrification treatment into the ammoniation tank 2 for gas-liquid separation;

[0079] Collect the separated N2O gas in the sewage after denitrification treatment;

[0080] The remaining liquid undergoes an ammonification reaction under the ammonification action of ammonifying functional bacteria in the ammoniation tank 2 to obtain the sewage after ammonification treatment;

[0081] Introduce the sewage after ammonification treatment into the nitrification tank 3 to carry out a nitrification reaction with nitrite bacteria to obtain sewage containing NO2 - ;

[0082] The sewage containing NO2 -The sewage is returned to the denitrification tank 1 for cyclic treatment, providing NO2 for the denitrification tank 1 - raw materials;

[0083] The sewage after cyclic treatment is introduced into the separator 4 for stable separation;

[0084] The sewage after cyclic treatment in the separator 4 is sampled and detected;

[0085] If the detection result does not meet the wastewater discharge standard, the liquid outlet end 18 should be closed, and the reflux end 17 should be continuously opened to return the sewage to be recycled to the denitrification tank 1 for cyclic treatment;

[0086] If the detection result is lower than the wastewater discharge standard, it can be judged that the treatment result is qualified, the treatment is completed, the reflux end 17 is closed, and the liquid outlet end 18 is opened to discharge all the effluent.

[0087] It should be noted that in the present invention, operations such as mixing nitrogen-containing landfill leachate and activated sludge, returning sewage containing nitrite, and cyclically mixing sewage to be recycled do not necessarily directly occur in the denitrification tank 1. They can be carried out in a preparatory tank provided outside the denitrification tank 1 or in the infusion pipeline 20, and finally drained into the denitrification tank 1. There are no excessive restrictions here.

[0088] It should be pointed out that in the present invention, the wastewater discharge standard can be selected with reference to the discharge standards of different countries, provinces or regions, or can be selected with reference to the use of the effluent after discharge. The general detection indicators are total nitrogen content and ammonia nitrogen content. There are no excessive restrictions here;

[0089] Furthermore, the method for detecting the total nitrogen content and ammonia nitrogen content of the sewage after cyclic treatment in the separator 4 needs to be adjusted according to different standard regulations, and there are no excessive restrictions here either.

[0090] In specific applications, the carbon sources supplemented in the low carbon-nitrogen ratio inhibition method can include simple organic substances such as methanol, sodium acetate, flour, glucose, etc., which can be selected according to cost and actual applications. There are no excessive restrictions here.

[0091] Further, the content of the present invention is described in detail in combination with embodiments:

[0092] Embodiment 1

[0093] In this embodiment, the treatment system of landfill leachate is as Figure 1 shown, in which, a pH meter (not shown in the figure) and a thermometer (not shown in the figure) are provided in the denitrification tank 1. The aeration device 12 is composed of a jet aeration device, a jet pump and a blower. The ammonia nitrogen treatment load of the treatment system is set to 2400 kg / d;

[0094] The chemical oxygen demand (COD) of nitrogen-containing landfill leachate is 8300 mg / L, the biochemical oxygen demand (BOD) is 2690 mg / L, the ammonia nitrogen concentration is 3500 mg / L, and the salinity is 7200 mg / L (in terms of NaCl). The specific operation process is as follows: Figure 2 As shown, the following steps are included:

[0095] (1) Mixing nitrogen-containing landfill leachate and activated sludge, and introducing them into denitrification tank 1, controlling the sludge concentration in denitrification tank 1 to 12000 mg / L, the water temperature to 32°C, and the pH to 7.5; then adding methanol as a carbon source into denitrification tank 1 to control the C / N ratio to 1.05, adjusting the hydraulic retention time to 30 min, and adjusting the dissolved oxygen concentration to 0.2 mg / L, to obtain wastewater after denitrification treatment;

[0096] (2) introducing the sewage after denitrification treatment into the ammoniation tank 2, turning on the aeration device 12 and the exhaust system 19 to separate the gas and liquid, separating and collecting the N2O gas, controlling the hydraulic retention time in the ammoniation tank 2 to 60 min, adjusting the dissolved oxygen concentration to 1.2 mg / L, and obtaining sewage after ammoniation treatment;

[0097] (3) introducing the sewage after ammoniation treatment into the nitrification tank 3, controlling the dissolved oxygen concentration in the nitrification tank 3 to 0.8 mg / L, and controlling the reflux ratio to 20, to obtain sewage containing nitrite;

[0098] (4) The nitrite-containing wastewater is returned to the denitrification tank 1 for circulation treatment, and then the wastewater after circulation treatment is introduced into the separator 4. The liquid in the separator 4 is sampled to detect the total nitrogen content and ammonia nitrogen content. If the test result is lower than the wastewater discharge standard, the effluent can be discharged and the treatment is completed.

[0099] The discharged effluent was tested, and the results showed that the total nitrogen content was less than 40 mg / L, and the ammonia nitrogen content was less than 5 mg / L, which was far lower than the 10 mg / L stipulated in the first-level wastewater discharge standard. It met the wastewater discharge standard and completed the leachate treatment. The nitrogen recovery rate converted into N2O gas by the system was 82%, achieving the purpose of N2O waste gas emission reduction and energy recovery.

[0100] Example 2

[0101] In this embodiment, the treatment system of landfill leachate is as follows: Figure 1 As shown, a pH meter (not shown in the figure) and a thermometer (not shown in the figure) are provided in the denitrification tank 1, and the aeration device 12 is composed of a jet aeration device, a jet pump and a blower. The ammonia nitrogen treatment load of the treatment system is set to 2400 kg / d;

[0102] The COD of the nitrogen-containing landfill leachate is 8300 mg / L, the BOD is 2690 mg / L, the ammonia nitrogen concentration is 3500 mg / L, and the salinity is 7200 mg / L (calculated as NaCl). The specific operation process is as Figure 2 shown and includes the following steps:

[0103] (1) After mixing the nitrogen-containing landfill leachate and activated sludge, introduce them into denitrification tank 1. Control the sludge concentration in denitrification tank 1 within 13500 mg / L, the water temperature at 34 °C, and the pH at 8.0; then add methanol into denitrification tank 1 as a carbon source to control the C / N at 1.25, adjust the hydraulic retention time to 35 min, and adjust the dissolved oxygen concentration to 0.3 mg / L to obtain the sewage after denitrification treatment;

[0104] (2) Introduce the sewage after denitrification treatment into ammonification tank 2, turn on the aeration device 12 and the exhaust system 19 for gas-liquid separation, separate and collect N2O gas, control the hydraulic retention time in ammonification tank 2 at 105 min, and adjust the dissolved oxygen concentration to 1.6 mg / L to obtain the sewage after ammonification treatment;

[0105] (3) Introduce the sewage after ammonification treatment into nitrification tank 3, control the dissolved oxygen concentration in nitrification tank 3 at 1.15 mg / L, and control the reflux ratio at 25 to obtain the sewage containing nitrite;

[0106] (4) Return the sewage containing nitrite to denitrification tank 1 for cyclic treatment, and then introduce the sewage after cyclic treatment into separator 4. Take a sample of the liquid in separator 4 and detect the total nitrogen content and ammonia nitrogen content therein. If the detection results are lower than the wastewater discharge standard, the effluent can be discharged, and the treatment is completed.

[0107] Detect the discharged effluent. The results show that the total nitrogen content is less than 40 mg / L, the ammonia nitrogen content is less than 5 mg / L and far lower than the 10 mg / L stipulated by the first-class wastewater discharge standard, meeting the wastewater discharge standard. The treatment of the landfill leachate is completed. The nitrogen recovery rate of the system converted into N2O gas is 82%, achieving the purpose of reducing N2O waste gas emissions and energy recovery.

[0108] Example 3

[0109] In this example, the treatment system of the landfill leachate is as Figure 1 shown. Among them, a pH meter (not shown in the figure) and a thermometer (not shown in the figure) are provided in denitrification tank 1. The aeration device 12 is composed of a jet aeration device, a jet pump, and a blower. The ammonia nitrogen treatment load of the treatment system is set at 2400 kg / d;

[0110] The COD of the nitrogen-containing landfill leachate is 8300 mg / L, the BOD is 2690 mg / L, the ammonia nitrogen concentration is 3500 mg / L, and the salinity is 7200 mg / L (calculated as NaCl). The specific operation process is as Figure 2 shown, including the following steps:

[0111] (1) After mixing the nitrogen-containing landfill leachate and activated sludge, introduce them into denitrification tank 1. Control the sludge concentration in denitrification tank 1 within 15000 mg / L, the water temperature at 36 °C, and the pH at 8.5. Then add methanol into denitrification tank 1 as a carbon source to control the C / N at 1.45, adjust the hydraulic retention time to 40 min, and adjust the dissolved oxygen concentration to 0.4 mg / L to obtain the sewage after denitrification treatment;

[0112] (2) Introduce the sewage after denitrification treatment into ammonification tank 2. Turn on the aeration device 12 and the exhaust system 19 for gas-liquid separation, separate and collect N2O gas. Control the hydraulic retention time in ammonification tank 2 at 150 min, and adjust the dissolved oxygen concentration to 2.0 mg / L to obtain the sewage after ammonification treatment;

[0113] (3) Introduce the sewage after ammonification treatment into nitrification tank 3. Control the dissolved oxygen concentration in nitrification tank 3 at 1.5 mg / L and the reflux ratio at 30 to obtain the sewage containing nitrite;

[0114] (4) Return the sewage containing nitrite to denitrification tank 1 for cyclic treatment. Then introduce the sewage after cyclic treatment into separator 4, take a sample of the liquid in separator 4, and detect the total nitrogen content and ammonia nitrogen content therein. If the detection results are lower than the wastewater discharge standard, the effluent can be discharged, and the treatment is completed.

[0115] Detect the discharged effluent. The results show that the total nitrogen content is less than 40 mg / L, the ammonia nitrogen content is less than 5 mg / L and far lower than the 10 mg / L stipulated by the first-class wastewater discharge standard, meeting the wastewater discharge standard. The treatment of the landfill leachate is completed. The nitrogen recovery rate of the system converted into N2O gas is 82%, achieving the purpose of reducing N2O waste gas emissions and energy recovery.

[0116] Example 4

[0117] In this example, the treatment system of the landfill leachate is as Figure 1 shown. Among them, a pH meter (not shown in the figure) and a thermometer (not shown in the figure) are provided in denitrification tank 1. The aeration device 12 is composed of a pure oxygen aeration device, a jet pump, and a blower. The ammonia nitrogen treatment load of the treatment system is set at 2400 kg / d;

[0118] The COD of nitrogen-containing landfill leachate is 5500 mg / L, BOD is 1265 mg / L, ammonia nitrogen concentration is 3450 mg / L, and salinity is 8800 mg / L (in terms of NaCl). The specific operation process is as follows: Figure 2 As shown, the following steps are included:

[0119] (1) Mixing nitrogen-containing landfill leachate and activated sludge, and introducing them into denitrification tank 1, controlling the sludge concentration in denitrification tank 1 to be within 15000 mg / L, the water temperature to be 30°C, and the pH to be 7.5; then adding methanol as a carbon source into denitrification tank 1 to control the C / N ratio to be 1.05, adjusting the hydraulic retention time to 30 min, and adjusting the dissolved oxygen concentration to be 0.2 mg / L, to obtain wastewater after denitrification treatment;

[0120] (2) introducing the sewage after denitrification treatment into the ammoniation tank 2, turning on the aeration device 12 and the exhaust system 19 to separate the gas and liquid, separating and collecting the N2O gas, controlling the hydraulic retention time in the ammoniation tank 2 to 60 minutes, adjusting the dissolved oxygen concentration to 1.0 mg / L, and obtaining sewage after ammoniation treatment;

[0121] (3) introducing the sewage after ammoniation treatment into the nitrification tank 3, controlling the dissolved oxygen concentration in the nitrification tank 3 to 0.8 mg / L, and controlling the reflux ratio to 20, to obtain sewage containing nitrite;

[0122] (4) The nitrite-containing wastewater is returned to the denitrification tank 1 for circulation treatment, and then the wastewater after circulation treatment is introduced into the separator 4. The liquid in the separator 4 is sampled to detect the total nitrogen content and ammonia nitrogen content. If the test result is lower than the wastewater discharge standard, the effluent can be discharged and the treatment is completed.

[0123] The discharged effluent was tested, and the results showed that the total nitrogen content was less than 40 mg / L, and the ammonia nitrogen content was less than 5 mg / L, which was far lower than the 10 mg / L stipulated in the first-level wastewater discharge standard. It met the wastewater discharge standard and completed the leachate treatment. The nitrogen recovery rate converted into N2O gas by the system was 85%, achieving the purpose of N2O waste gas emission reduction and energy recovery.

[0124] Example 5

[0125] In this embodiment, the treatment system of landfill leachate is as follows: Figure 1 As shown, a pH meter (not shown in the figure) and a thermometer (not shown in the figure) are provided in the denitrification tank 1, and the aeration device 12 is composed of a pure oxygen aeration device, a jet pump and a blower, and the ammonia nitrogen treatment load of the treatment system is set to 2400 kg / d;

[0126] The COD of nitrogen-containing landfill leachate is 5500 mg / L, BOD is 1265 mg / L, ammonia nitrogen concentration is 3450 mg / L, and salinity is 8800 mg / L (in terms of NaCl). The specific operation process is as follows: Figure 2 As shown, the following steps are included:

[0127] (1) Mixing nitrogen-containing landfill leachate and activated sludge, and introducing them into denitrification tank 1, controlling the sludge concentration in denitrification tank 1 to be within 16500 mg / L, the water temperature to be 31.5°C, and the pH to be 7.85; then adding methanol as a carbon source into denitrification tank 1 to control the C / N ratio to be 1.2, adjusting the hydraulic retention time to 37.5 min, and adjusting the dissolved oxygen concentration to be 0.3 mg / L, to obtain wastewater after denitrification treatment;

[0128] (2) introducing the sewage after denitrification treatment into the ammoniation tank 2, turning on the aeration device 12 and the exhaust system 19 to separate the gas and liquid, separating and collecting the N2O gas, controlling the hydraulic retention time in the ammoniation tank 2 to 105 min, adjusting the dissolved oxygen concentration to 1.5 mg / L, and obtaining sewage after ammoniation treatment;

[0129] (3) introducing the sewage after ammoniation treatment into the nitrification tank 3, controlling the dissolved oxygen concentration in the nitrification tank 3 to be 1.15 mg / L, and controlling the reflux ratio to be 27.5, to obtain sewage containing nitrite;

[0130] (4) The nitrite-containing wastewater is returned to the denitrification tank 1 for circulation treatment, and then the wastewater after circulation treatment is introduced into the separator 4. The liquid in the separator 4 is sampled to detect the total nitrogen content and ammonia nitrogen content. If the test result is lower than the wastewater discharge standard, the effluent can be discharged and the treatment is completed.

[0131] The discharged effluent was tested, and the results showed that the total nitrogen content was less than 40 mg / L, and the ammonia nitrogen content was less than 5 mg / L, which was far lower than the 10 mg / L stipulated in the first-level wastewater discharge standard. It met the wastewater discharge standard and completed the leachate treatment. The nitrogen recovery rate converted into N2O gas by the system was 85%, achieving the purpose of N2O waste gas emission reduction and energy recovery.

[0132] Example 6

[0133] In this embodiment, the treatment system of landfill leachate is as follows: Figure 1 As shown, a pH meter (not shown in the figure) and a thermometer (not shown in the figure) are provided in the denitrification tank 1, and the aeration device 12 is composed of a pure oxygen aeration device, a jet pump and a blower, and the ammonia nitrogen treatment load of the treatment system is set to 2400 kg / d;

[0134] The COD of nitrogen-containing landfill leachate is 5500 mg / L, the BOD is 1265 mg / L, the ammonia nitrogen concentration is 3450 mg / L, and the salinity is 8800 mg / L (calculated as NaCl). The specific operation process is as Figure 2 shown, including the following steps:

[0135] (1) Mix the nitrogen-containing landfill leachate and activated sludge and introduce them into denitrification tank 1. Control the sludge concentration in denitrification tank 1 within 18000 mg / L, the water temperature at 33 °C, and the pH at 8.2; then put methanol into denitrification tank 1 as a carbon source to control the C / N at 1.35, adjust the hydraulic retention time to 45 min, and adjust the dissolved oxygen concentration to 0.4 mg / L to obtain the sewage after denitrification treatment;

[0136] (2) Introduce the sewage after denitrification treatment into ammonification tank 2, turn on the aeration device 12 and the exhaust system 19 for gas-liquid separation, separate and collect N2O gas, control the hydraulic retention time in ammonification tank 2 at 150 min, and adjust the dissolved oxygen concentration to 2.0 mg / L to obtain the sewage after ammonification treatment;

[0137] (3) Introduce the sewage after ammonification treatment into nitrification tank 3, control the dissolved oxygen concentration in nitrification tank 3 at 1.5 mg / L, and control the reflux ratio at 35 to obtain sewage containing nitrite;

[0138] (4) Return the sewage containing nitrite to denitrification tank 1 for cyclic treatment, then introduce the sewage after cyclic treatment into separator 4, sample the liquid in separator 4, and detect the total nitrogen content and ammonia nitrogen content therein. If the detection results are lower than the wastewater discharge standard, the effluent can be discharged, and the treatment is completed.

[0139] Detect the discharged effluent. The results show that the total nitrogen content is less than 40 mg / L, the ammonia nitrogen content is less than 5 mg / L and far lower than the 10 mg / L specified by the first-class wastewater discharge standard, meeting the wastewater discharge standard. The landfill leachate treatment is completed. The nitrogen recovery rate of the system converted into N2O gas is 85%, achieving the purpose of reducing N2O waste gas emissions and energy recovery.

[0140] The above embodiments only represent several implementation manners of the present invention. The technical features of the present invention can be arbitrarily combined. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combinations of these technical features do not conflict, they should all be considered as the scope recorded in this specification.

Claims

1. A method for treating landfill leachate, characterized in that, The method comprises the following steps: Mix the nitrogen-containing landfill leachate and activated sludge and introduce them into the denitrification tank for reaction. The reaction process is as follows: under the condition of inhibiting the reduction of nitrous oxide, nitrite in the mixture is converted into nitrous oxide gas dissolved in the sewage under the action of denitrifying bacteria in the denitrification tank, and the sewage after denitrification treatment is obtained; under the condition of inhibiting the reduction of N2O, NO2 in the mixture is converted into NO under the action of nitrite reductase in denitrifying bacteria, and NO is converted into N2O under the action of nitric oxide reductase in denitrifying bacteria. At this time, N2O is dissolved in the sewage and is no longer reduced to N2; - Under the action of nitrite reductase in denitrifying bacteria, it is converted into NO, and NO is converted into N2O under the action of nitric oxide reductase in denitrifying bacteria. At this time, N2O is dissolved in the sewage and is no longer reduced to N2; The sewage after denitrification treatment is introduced into an ammonification tank for gas-liquid separation, and nitrous oxide gas in the sewage after denitrification treatment is separated and collected; and the sewage after ammonification treatment is obtained under the ammonification effect of ammonifying functional bacteria in the ammonification tank; The sewage after ammonification treatment is introduced into a nitrification tank for reaction, so that the sewage after ammonification treatment is converted into sewage containing nitrite under the action of nitrosifying bacteria in the nitrification tank; The sewage containing nitrite is refluxed to the denitrification tank for cyclic treatment to provide nitrite raw materials for the denitrification tank; The sewage after cyclic treatment is introduced into a separator for separation and detection. If the detection result meets the discharge requirements, the separated effluent is discharged; otherwise, the sewage to be recycled is refluxed to the denitrification tank for cyclic treatment; The dissolved oxygen concentration in the nitrification tank is controlled within the range of 0.8-1.5 mg / L, and the reflux ratio is controlled within the range of 20-35.

2. The treatment method of landfill leachate according to claim 1, characterized in that The method for providing the conditions for inhibiting nitrous oxide reduction includes controlling the hydraulic retention time of the denitrification tank within the range of 30-45 min.

3. The treatment method of landfill leachate according to claim 1, characterized in that The method for providing the conditions for inhibiting nitrous oxide reduction includes inhibiting the activity of nitrous oxide reductase.

4. The method for treating landfill leachate according to claim 3, characterized in that, The method for inhibiting the activity of nitrous oxide reductase is any one or more of a high salinity inhibition method, a high dissolved oxygen inhibition method, and a low carbon-nitrogen ratio inhibition method; Wherein: in the high salinity inhibition method, the salinity is controlled within the range of 7000-9000 mg / L in terms of NaCl; in the high dissolved oxygen inhibition method, the dissolved oxygen concentration is controlled within the range of 0.2-0.4 mg / L; in the low carbon-nitrogen ratio inhibition method, a carbon source is supplemented to control the ratio of the biochemical oxygen demand to ammonia nitrogen content of the influent within the range of 1.05-1.

55.

5. The treatment method of landfill leachate according to claim 1, wherein The method for providing the conditions for inhibiting nitrous oxide reduction includes using denitrifying bacteria without a nitrous oxide reductase system.

6. The treatment method of landfill leachate according to claim 1, characterized in that, The hydraulic retention time of the ammonification tank is controlled within the range of 60-150 min, and the dissolved oxygen concentration is controlled within the range of 1.0-2.0 mg / L.

7. The treatment method of landfill leachate according to claim 1, characterized in that, It is treated by a treatment system, and the treatment system includes: a denitrification tank, an ammonification tank, a nitrification tank, and a separator; The denitrification tank is provided with an inlet, a carbon source inlet, a circulating water inlet, a first dissolved oxygen meter, an oxidation-reduction potential, and an output end for the sewage after denitrification treatment; an influent flowmeter is provided at the inlet, and a circulating flowmeter is provided at the circulating water inlet; the first dissolved oxygen meter is used to detect the dissolved oxygen concentration in the denitrification tank; the oxidation-reduction potential is used to monitor the denitrification reaction condition; The ammonification tank is provided with an input end for the sewage after denitrification treatment, a nitrous oxide output port, an output end for the sewage after ammonification treatment, an aeration device, a ventilation system, and a second dissolved oxygen meter; the aeration device is arranged at the bottom of the ammonification tank and is used for separating nitrous oxide gas from the water body; the nitrous oxide output port is arranged at the top of the ammonification tank and cooperates with the ventilation system to extract nitrous oxide gas out of the ammonification tank; the second dissolved oxygen meter is used to detect the dissolved oxygen concentration in the ammonification tank; The nitrification tank is provided with an input end for sewage after ammonification treatment, an output end for sewage containing nitrite, a third dissolved oxygen meter, and a waste liquid output end; the third dissolved oxygen meter is used to detect the concentration of dissolved oxygen in the nitrification tank; The separator is provided with a waste liquid input end, a reflux end, and a liquid output end; The output end of the sewage after denitrification treatment is communicated with the input end of the sewage after denitrification treatment, the output end of the sewage after ammonification treatment is communicated with the input end of the sewage after ammonification treatment, the waste liquid output end is communicated with the waste liquid input end, and the output end of the sewage containing nitrite converges with the reflux end and is communicated with the circulating water inlet.

8. The treatment method of landfill leachate according to claim 7, characterized in that, The aeration device includes a jet aeration device.

9. The treatment method of landfill leachate according to claim 7, characterized in that, The aeration device includes a pure oxygen aeration device.

10. The treatment method of landfill leachate according to claim 7, characterized in that, The treatment system further includes a pH meter and a thermometer for monitoring reaction parameters.

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