System for treating leachate from municipal solid waste incineration plants based on direct ammonia oxidation

Abstract

This invention discloses a system for treating leachate from municipal solid waste incineration plants based on direct ammonia oxidation, relating to the field of leachate treatment technology for municipal solid waste incineration plants. The system includes a wastewater outlet connected to the inlet of a first sedimentation tank, the outlet of which is connected to the inlet of a direct ammonia oxidation reactor. The outlet of the direct ammonia oxidation reactor is connected to the inlet of a second sedimentation tank, which is connected to the inlet of a heterotrophic denitrification reactor. The outlet of the heterotrophic denitrification reactor is connected to the inlet of a membrane bioreactor. The membrane outlet of the membrane bioreactor is connected to the inlet of a catalytic ozone oxidation reactor, and the effluent from the catalytic ozone oxidation reactor flows into an effluent tank. This system eliminates the need for expensive carbon sources, simplifies the treatment process, reduces the required floor space, and to some extent lowers construction investment and operating costs.

Description

Technical Field

[0001] This invention relates to the field of leachate treatment technology for municipal solid waste incineration plants, specifically to a system for treating leachate from municipal solid waste incineration plants based on direct ammonia oxidation. Background Technology

[0002] Leachate from municipal solid waste incineration plants primarily originates from the water released from the waste stored in the pit before incineration due to compression, as well as wastewater generated from the acidic fermentation of organic matter within the pit. This type of leachate is characterized by large fluctuations in water quality and quantity, high concentrations of ammonia nitrogen and organic matter, strong toxicity, and complex water composition. Direct discharge without proper treatment will not only pollute rivers and lakes but also indirectly impact the air and soil, severely damaging the ecological environment and even endangering human health. Therefore, achieving the reduction, resource recovery, and harmless treatment of leachate from waste incineration plants has long been a challenging problem for enterprises. Consequently, there is an urgent need to develop a treatment system capable of efficiently removing high concentrations of ammonia nitrogen and organic matter from leachate from municipal solid waste incineration plants.

[0003] Currently, the treatment of leachate from municipal solid waste incineration plants often employs a combined approach: physicochemical pretreatment - anaerobic reactor - pre-denitrification - aerobic nitrification - reverse denitrification - membrane bioreactor - ultrafiltration - reverse osmosis (or nanofiltration). This biological treatment system (anaerobic reactor - pre-denitrification - aerobic nitrification - reverse denitrification - membrane bioreactor) can remove most organic matter and nitrogenous compounds. However, this biological treatment system suffers from problems such as excessively long process flow, complex operation and maintenance, and large footprint. Furthermore, due to the high total nitrogen concentration in the leachate, to ensure that the final effluent meets current emission standards, expensive carbon sources are usually added to the post-denitrification unit, significantly increasing operating costs. In addition, although the final effluent treated by this method meets emission standards, the membrane concentrate produced after deep treatment using membrane separation technology contains even more difficult-to-remove high concentrations of pollutants. If the membrane concentrate is continuously sprayed back into the incinerator, it will not only cause corrosion inside the furnace but also affect the normal operation of the incinerator. Summary of the Invention

[0004] The purpose of this invention is to provide a system for treating leachate from municipal solid waste incineration plants based on direct ammonia oxidation. Specifically, the direct ammonia oxidation technology achieves simultaneous nitrogen and carbon removal while generating only small amounts of nitrite and nitrate nitrogen; the catalytic ozone oxidation technology not only further removes residual organic pollutants from the biochemical effluent but also avoids the generation of membrane concentrate.

[0005] To achieve the above objectives, the technical solution of this application is as follows: a system for treating leachate from a municipal solid waste incineration plant based on direct ammonia oxidation, comprising a main treatment system, wherein the main treatment system includes an anaerobic hydrolysis acidification reactor, a first sedimentation tank, a direct ammonia oxidation reactor, a second sedimentation tank, a heterotrophic denitrification reactor, a membrane bioreactor, and a catalytic ozone oxidation reactor; the wastewater outlet of the anaerobic hydrolysis acidification reactor is connected to the inlet of the first sedimentation tank, and the outlet of the first sedimentation tank is connected to the inlet of the direct ammonia oxidation reactor; the outlet of the direct ammonia oxidation reactor is connected to the inlet of the second sedimentation tank, and the outlet of the second sedimentation tank is connected to the inlet of the heterotrophic denitrification reactor; the outlet of the heterotrophic denitrification reactor is connected to the inlet of the membrane bioreactor; the membrane outlet of the membrane bioreactor is connected to the inlet of the catalytic ozone oxidation reactor, and the effluent from the catalytic ozone oxidation reactor flows into an effluent tank.

[0006] In a preferred embodiment of the present invention, in the anaerobic hydrolysis acidification reactor, the leachate is mixed evenly under the action of the second stirring paddle, and the hydrolytic acidification bacteria decompose the large organic molecules in the leachate into small organic molecules that are easily utilized by secreting extracellular enzymes, thereby increasing the content of volatile fatty acids.

[0007] In a preferred embodiment of the present invention, in the direct ammonia oxidation reactor, the direct ammonia oxidation bacteria convert the ammonia nitrogen in the anaerobic hydrolysis acidification effluent into hydroxylamine, and then further into nitrogen gas, with only a small amount of nitrate nitrogen and nitrite nitrogen generated; at the same time, the organic matter in the anaerobic hydrolysis acidification effluent is used as a carbon source by the direct ammonia oxidation reaction, thereby achieving simultaneous denitrification and carbon removal.

[0008] In a preferred embodiment of the present invention, in the heterotrophic denitrification reactor, nitrate nitrogen and nitrite nitrogen generated in the effluent from direct ammonia oxidation are reduced to nitrogen gas by heterotrophic denitrifying bacteria; then, part of the COD is removed by aerobic bacteria.

[0009] As a preferred embodiment of the present invention, a mixed liquor reflux pump is provided in the membrane bioreactor to reflux the mixed liquor to the front end of the heterotrophic denitrification reactor; this process provides sludge to the heterotrophic denitrification reactor on the one hand, and further removes residual nitrate nitrogen in the membrane bioreactor on the other hand.

[0010] In a preferred embodiment of the present invention, in the catalytic ozone oxidation reactor, recalcitrant organic matter in the biochemical effluent is adsorbed onto the catalyst surface through chemical bonds and further removed by reacting with ozone in the gas or liquid phase.

[0011] As a preferred embodiment of the present invention, a pretreatment system is provided before the main treatment system. The pretreatment system includes a coagulation and stirring tank, an inclined plate sedimentation tank, an intermediate water tank and a multi-media filter connected in sequence. The outlet of the multi-media filter is connected to the inlet of the anaerobic hydrolysis acidification reactor through a first inlet pump.

[0012] In a preferred embodiment of the present invention, leachate is pumped into a coagulation mixing tank and forms flocs under the action of a first stirring paddle; the outlet of the coagulation mixing tank is connected to the inlet of an inclined plate sedimentation tank, and the flocs with higher density are removed in the inclined plate sedimentation tank; the outlet of the inclined plate sedimentation tank is connected to the inlet of an intermediate water tank; the outlet of the intermediate water tank is connected to the inlet of a multi-media filter via a filter pump to remove suspended solids from the wastewater.

[0013] As a preferred embodiment of the present invention, the outlet of the first sedimentation tank is connected to the inlet of the direct ammonia oxidation reactor via a second inlet pump, and the dissolved oxygen required in the direct ammonia oxidation reactor is provided by the first aeration head at the bottom of the reactor under the action of the first aeration pump.

[0014] In a preferred embodiment of the present invention, the outlet of the second sedimentation tank is connected to the inlet of the heterotrophic denitrification reactor via a third inlet pump, and the outlet of the heterotrophic denitrification reactor is connected to the inlet of the membrane bioreactor via a fourth inlet pump for mud-water separation. The membrane module in the membrane bioreactor is fixed on a stainless steel frame, the membrane pressure difference is monitored, and the membrane is cleaned regularly. A second aeration head is provided at the bottom of the membrane bioreactor, and the second aeration head is connected to a second aeration pump.

[0015] In a preferred embodiment of the present invention, the membrane effluent of the membrane bioreactor is connected to the inlet of the catalytic ozone oxidation reactor via a fifth inlet pump, and the effluent of the catalytic ozone oxidation reactor flows into the effluent tank via an outlet pump; a third aeration head is provided at the bottom of the catalytic ozone oxidation reactor, and a catalyst support tray is provided above the third aeration head; the liquid oxygen storage tank is connected to the catalytic ozone oxidation reactor via an evaporator and an ozone generator.

[0016] Compared with existing technologies, this invention has the following advantages: direct ammonia oxidation has a wide range of applications; under aerobic conditions with a C / N ratio of 5-20 and a pH of 7-10, it can convert ammonia nitrogen into hydroxylamine, and then further into nitrogen gas, achieving simultaneous denitrification and carbon removal while generating less nitrate and nitrite nitrogen. It also overcomes the inhibition caused by excessively high organic matter concentrations in traditional treatment processes. The advanced oxidation technology of catalytic ozone oxidation can not only further degrade organic matter in the biochemical effluent but also avoid the generation of membrane concentrate. As a novel leachate treatment system for municipal solid waste incineration plants that couples biochemical treatment and advanced oxidation technologies, it has advantages such as a short process flow, small footprint, simple maintenance and operation, no need for expensive external carbon sources, and low investment and construction costs. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a system for treating leachate from a municipal solid waste incineration plant based on direct ammonia oxidation.

[0018] The numbers in the diagram are as follows: 1. Inlet pump; 2. Coagulation mixing tank; 3. First stirring paddle; 4. Inclined plate sedimentation tank; 5. Intermediate water tank; 6. Filter pump; 7. Multi-media filter; 8. First inlet pump; 9. Anaerobic hydrolysis acidification reactor; 10. Second stirring paddle; 11. First sedimentation tank; 12. Second inlet pump; 13. Direct ammonia oxidation reactor; 14. First aerator; 15. First aeration pump; 16. Second sedimentation tank; 17. Third inlet pump; 18. Heterotrophic denitrification reactor; 19. Fourth inlet pump; 20. Membrane bioreactor; 21. Second aerator; 22. Second aeration pump; 23. Membrane module; 24. Mixed liquor return pump; 25. Fifth inlet pump; 26. Catalytic ozone oxidation reactor; 27. Third aerator; 28. Catalyst support tray; 29. ​​Ozone generator; 30. Liquid oxygen storage tank; 31. Evaporator; 32. Effluent pump. Specific implementation methods

[0019] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the equipment and reagents used in the present invention are commercially available products conventional in this technical field.

[0020] The term "comprising" and its variations, as used in this invention, signify an open-ended inclusion, i.e., "including but not limited to". Unless otherwise stated, the term "or" means "and / or". The term "based on" means "at least partially based on". The terms "first", "second", "third", "fourth", etc., may refer to different or the same objects. Other explicit and implicit definitions may also be included below.

[0021] This embodiment provides a method for treating leachate from a municipal solid waste incineration plant based on direct ammonia oxidation. The method is implemented within the aforementioned system, such as... Figure 1 As shown, this method mainly utilizes a combined process of direct ammonia oxidation for simultaneous denitrification and carbon removal coupled with catalytic ozone oxidation for deep removal of organic matter to treat leachate from municipal solid waste incineration plants; specifically, it includes the following steps:

[0022] (1) Pretreatment to remove solid suspended matter and colloids from leachate from municipal solid waste incineration plant; specifically, flocs are first formed in coagulation mixing tank 2 by first stirring paddle 3, then flocs with higher density (ρ>1) in leachate are removed by inclined plate sedimentation tank 4, and finally solid suspended matter (ρ≤1) in leachate is removed by multi-media filter 7.

[0023] (2) The leachate after being treated by the multi-media filter is fed into the anaerobic hydrolysis acidification reactor 9 for anaerobic hydrolysis acidification treatment. The second stirring paddle 10 is used to make the sludge and leachate mix evenly, thereby increasing the content of volatile fatty acids in the leachate.

[0024] (3) The leachate treated by the anaerobic hydrolysis acidification reactor is fed into the first sedimentation tank 11 to separate the leachate from the sludge and obtain the supernatant.

[0025] (4) The supernatant after step (3) is fed into the direct ammonia oxidation reactor 13 for simultaneous denitrification and decarbonization. Air is fed into the direct ammonia oxidation reactor through the aeration pipe, and the dissolved oxygen in the reactor is controlled to be maintained at 6 mg / L.

[0026] (5) The leachate treated by the direct ammonia oxidation reactor is fed into the second sedimentation tank 16, where the leachate is separated from the sludge again to obtain the supernatant.

[0027] (6) The supernatant after step (5) is fed into the heterotrophic denitrification reactor 18 for denitrification treatment, and the residual nitrate nitrogen and nitrite nitrogen in the leachate are converted into nitrogen gas.

[0028] (7) The leachate treated by the heterotrophic denitrification reactor is fed into the membrane bioreactor 20 for sludge-water separation; at the same time, under the action of the mixed liquor return pump 24, part of the mixed liquor is returned to the front end of the heterotrophic denitrification reactor, which can replenish sludge to the heterotrophic denitrification reactor on the one hand, and further remove residual nitrate nitrogen on the other hand.

[0029] (8) The leachate treated by the membrane bioreactor is fed into the catalytic ozone oxidation reactor 26 to further treat the organic matter and reduce the color of the leachate.

[0030] Example 1

[0031] When leachate was treated using the direct ammonia oxidation reactor in the above-mentioned treatment system, with a hydraulic retention time of 8 days, a reactor temperature of 30°C, and dissolved oxygen controlled at 6 mg / L, ammonia nitrogen decreased from 1202.9 mg / L to 104.2 mg / L, a removal rate of approximately 91.3%; total nitrogen (TN) decreased from 1992.2 mg / L to 676.8 mg / L, a removal rate of approximately 66.0%; and carbon dioxide (COD) decreased from 23598.0 mg / L to 6050.2 mg / L, a removal rate of approximately 74.4%.

[0032] Example 2

[0033] When the catalytic ozone oxidation reactor in the above treatment system is used to treat the biological effluent, an aluminum-based catalyst is added. Under the conditions of ozone aeration rate of 1.5 L / min and power of 50% for 2 hours, the COD can be reduced from 566.4 mg / L to 105.6 mg / L, with a removal rate of about 81.4%; at the same time, the color is reduced from 400 times to 40 times, with a removal rate of 90%.

[0034] The leachate treatment system for municipal solid waste incineration plants using this invention can effectively solve the existing problems in leachate treatment, enabling the treated effluent to meet discharge standards. Moreover, it eliminates the need for expensive carbon sources, simplifies the treatment process, reduces the required land area, and to some extent lowers construction investment and operating costs.

[0035] The foregoing description of specific exemplary embodiments of the present invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made to the invention. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A system for treating leachate from municipal solid waste incineration plants based on direct ammonia oxidation, characterized in that, The system includes a main treatment system comprising an anaerobic hydrolysis acidification reactor, a first sedimentation tank, a direct ammonia oxidation reactor, a second sedimentation tank, a heterotrophic denitrification reactor, a membrane bioreactor, and a catalytic ozone oxidation reactor. The wastewater outlet of the anaerobic hydrolysis acidification reactor is connected to the inlet of the first sedimentation tank, and the outlet of the first sedimentation tank is connected to the inlet of the direct ammonia oxidation reactor. The outlet of the direct ammonia oxidation reactor is connected to the inlet of the second sedimentation tank, and the outlet of the second sedimentation tank is connected to the inlet of the heterotrophic denitrification reactor; the outlet of the heterotrophic denitrification reactor is connected to the inlet of the membrane bioreactor; the membrane outlet of the membrane bioreactor is connected to the inlet of the catalytic ozone oxidation reactor, and the effluent from the catalytic ozone oxidation reactor flows into the effluent tank.

2. The system for treating leachate from municipal solid waste incineration plants based on direct ammonia oxidation according to claim 1, characterized in that, In the anaerobic hydrolysis acidification reactor, the leachate is mixed evenly under the action of the second stirring paddle. The hydrolytic acidification bacteria decompose the large organic molecules in the leachate into small organic molecules that are easily utilized by secreting extracellular enzymes, thereby increasing the content of volatile fatty acids.

3. The system for treating leachate from municipal solid waste incineration plants based on direct ammonia oxidation according to claim 1, characterized in that, In the direct ammonia oxidation reactor, direct ammonia oxidizing bacteria convert ammonia nitrogen in the anaerobic hydrolysis acidification effluent into hydroxylamine, which is then further converted into nitrogen gas, with only a small amount of nitrate nitrogen and nitrite nitrogen generated. At the same time, the organic matter in the anaerobic hydrolysis acidification effluent is used as a carbon source by the direct ammonia oxidation reaction, thereby achieving simultaneous denitrification and carbon removal.

4. The system for treating leachate from municipal solid waste incineration plants based on direct ammonia oxidation according to claim 1, characterized in that, In the heterotrophic denitrification reactor, nitrate nitrogen and nitrite nitrogen generated in the effluent from direct ammonia oxidation are reduced to nitrogen gas by heterotrophic denitrifying bacteria; then, some COD is removed by aerobic bacteria.

5. The system for treating leachate from municipal solid waste incineration plants based on direct ammonia oxidation according to claim 1, characterized in that, The membrane bioreactor is equipped with a mixed liquor reflux pump to return the mixed liquor to the front end of the heterotrophic denitrification reactor; This process provides sludge to the heterotrophic denitrification reactor on the one hand, and further removes residual nitrate nitrogen from the membrane bioreactor on the other.

6. The system for treating leachate from municipal solid waste incineration plants based on direct ammonia oxidation according to claim 1, characterized in that, In the catalytic ozone oxidation reactor, recalcitrant organic matter in the biochemical effluent is adsorbed onto the catalyst surface through chemical bonds and further removed by reacting with ozone in the gas or liquid phase.

7. The system for treating leachate from municipal solid waste incineration plants based on direct ammonia oxidation according to claim 1, characterized in that, A pretreatment system is set up before the main treatment system. The pretreatment system includes a coagulation and stirring tank, an inclined plate sedimentation tank, an intermediate water tank and a multi-media filter connected in sequence. The outlet of the multi-media filter is connected to the inlet of the anaerobic hydrolysis acidification reactor through a first inlet pump.

8. The system for treating leachate from municipal solid waste incineration plants based on direct ammonia oxidation according to claim 7, characterized in that, Leachate enters the coagulation mixing tank through an inlet pump and forms flocs under the action of the first stirring paddle. The outlet of the coagulation mixing tank is connected to the inlet of the inclined plate sedimentation tank. The flocs with higher density are removed in the inclined plate sedimentation tank. The outlet of the inclined plate sedimentation tank is connected to the inlet of the intermediate water tank. The outlet of the intermediate water tank is connected to the inlet of the multi-media filter through a filter pump to remove suspended solids from the wastewater.

9. The system for treating leachate from municipal solid waste incineration plants based on direct ammonia oxidation according to claim 1, characterized in that, The outlet of the second sedimentation tank is connected to the inlet of the heterotrophic denitrification reactor via a third inlet pump. The outlet of the heterotrophic denitrification reactor is connected to the inlet of the membrane bioreactor via a fourth inlet pump for mud-water separation. The membrane module in the membrane bioreactor is fixed on a stainless steel frame, the membrane pressure difference is monitored, and the membrane is cleaned regularly. A second aeration head is provided at the bottom of the membrane bioreactor, which is connected to a second aeration pump.

10. The system for treating leachate from municipal solid waste incineration plants based on direct ammonia oxidation according to claim 1, characterized in that, The membrane effluent from the membrane bioreactor is connected to the inlet of the catalytic ozone oxidation reactor via a fifth inlet pump. The effluent from the catalytic ozone oxidation reactor flows into the effluent tank via an outlet pump. A third aeration head is provided at the bottom of the catalytic ozone oxidation reactor, and a catalyst support tray is provided above the third aeration head. The liquid oxygen storage tank is connected to the catalytic ozone oxidation reactor via an evaporator and an ozone generator.

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