System for treating leachate of household garbage incineration plant based on direct ammoxidation

Abstract

The invention discloses a system for treating leachate of a household garbage incineration plant based on direct ammoxidation, and relates to the technical field of treatment of the leachate of the household garbage incineration plant. A wastewater outlet of an anaerobic hydrolysis acidification reactor is connected to a water inlet of a first sedimentation tank, and a water outlet of the first sedimentation tank is connected to a water inlet of a direct ammoxidation reactor; a water outlet of the direct ammoxidation reactor is connected with a water inlet of the second sedimentation tank; a water outlet of the second sedimentation tank is connected with a water inlet of the heterotrophic denitrification reactor; a water outlet of the heterotrophic denitrification reactor is connected to a water inlet of the membrane bioreactor; a membrane water outlet of the membrane bioreactor is connected to a water inlet of the catalytic ozonation reactor, and effluent of the catalytic ozonation reactor flows into a water outlet barrel. The system does not need to add an expensive carbon source, so that the treatment process is simplified, the occupied area is reduced, and the construction investment and the operation cost are reduced to a certain extent.

Description

Technical Field

[0001] The present invention relates to the technical field of leachate treatment in domestic waste incineration plants, and in particular to a system for treating leachate in domestic waste incineration plants based on direct ammonia oxidation. Background Art

[0002] Leachate from municipal solid waste incineration plants mainly comes from the water discharged from the garbage stored in the storage pit before incineration after being squeezed, and the wastewater produced by the acidic fermentation of organic matter in the garbage in the storage pit. This type of leachate has the characteristics of large fluctuations in water quality and quantity, high concentrations of ammonia nitrogen and organic matter, strong toxicity, and complex water quality components. If it is discharged directly without proper treatment, it will not only cause pollution to water sources such as rivers and lakes, but also have indirect effects on the air, soil and other environments, seriously damage the ecological environment, and even endanger human health. Therefore, how to achieve the reduction, resource utilization and harmless treatment of garbage incineration leachate has long been a problem that has plagued enterprises. To this end, it is urgent to develop a treatment system that can efficiently remove high concentrations of ammonia nitrogen and organic matter in the leachate of municipal solid waste incineration plants.

[0003] At present, the combination of "physical and chemical pretreatment-anaerobic reactor-pre-denitrification-aerobic nitrification-reverse denitrification-membrane bioreactor-ultrafiltration-reverse osmosis (or nanofiltration)" is often used to treat leachate from domestic waste incineration plants. The biochemical treatment system in this method (anaerobic reactor-pre-denitrification-aerobic nitrification-reverse denitrification-membrane bioreactor) can remove most organic matter and nitrogen-containing compounds. However, the biochemical treatment system has problems such as long process, complex operation and maintenance, and large facility footprint. At the same time, due to the high total nitrogen concentration in the leachate, in order to ensure that the total nitrogen in the final effluent meets the current emission standards, it is usually necessary to supplement the post-denitrification unit with expensive carbon sources, which greatly increases the operating cost. In addition, although the final effluent treated by this method can meet the emission standards, the membrane concentrate produced after deep treatment with membrane separation technology contains high-concentration pollutants that are more difficult to remove. If the membrane concentrate is sprayed back to the incinerator for a long time, it will not only cause corrosion in the furnace, but also affect the normal operation of the incinerator. Summary of the invention

[0004] The purpose of the present invention is to provide a system for treating leachate from a domestic waste incineration plant based on direct ammonia oxidation. The direct ammonia oxidation technology generates only a small amount of nitrite and nitric nitrogen while achieving simultaneous denitrification and carbon removal; the catalytic ozone oxidation technology can not only further remove the residual organic pollutants in the biochemical effluent, but also avoid the generation of membrane concentrate.

[0005] To achieve the above-mentioned purpose, the technical solution of the present application is: 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 comprises 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 water inlet of the first sedimentation tank, and the water outlet of the first sedimentation tank is connected to the water inlet of the direct ammonia oxidation reactor; the water outlet of the direct ammonia oxidation reactor is connected to the water inlet of the second sedimentation tank, and the water outlet of the second sedimentation tank is connected to the water inlet of the heterotrophic denitrification reactor; the water outlet of the heterotrophic denitrification reactor is connected to the water inlet of the membrane bioreactor; the membrane water outlet of the membrane bioreactor is connected to the water inlet of the catalytic ozone oxidation reactor, and the effluent of the catalytic ozone oxidation reactor flows into a water outlet bucket.

[0006] As 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 hydrolysis acidification bacteria decompose the macromolecular organic matter in the leachate into easily usable small molecular organic matter by secreting extracellular enzymes, thereby increasing the content of volatile fatty acids.

[0007] As a preferred embodiment of the present invention, in the direct ammonia oxidation reactor, direct ammonia oxidizing bacteria convert ammonia nitrogen in the anaerobic hydrolysis acidification effluent into hydroxylamine, and then further convert it into nitrogen gas, with only a small amount of nitrate nitrogen and nitrite nitrogen generated; at the same time, 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] As a preferred embodiment of the present invention, in the heterotrophic denitrification reactor, nitrate nitrogen and nitrite nitrogen generated in the effluent of direct ammonia oxidation are reduced to nitrogen gas under the action of heterotrophic denitrifying bacteria; and then part of COD is removed under the action of aerobic bacteria.

[0009] As a preferred embodiment of the present invention, a mixed liquor reflux pump is arranged 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 the residual nitric nitrogen in the membrane bioreactor on the other hand.

[0010] As a preferred embodiment of the present invention, in the catalytic ozone oxidation reactor, the refractory organic matter in the biochemical effluent is adsorbed on the catalyst surface through chemical bonds and further reacts with ozone in the gas phase or liquid phase to be removed.

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

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

[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 through a second water 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] As a preferred embodiment of the present invention, the water outlet of the second sedimentation tank is connected to the water inlet of the heterotrophic denitrification reactor through a third water inlet pump, and the water outlet of the heterotrophic denitrification reactor is connected to the water inlet of the membrane bioreactor through a fourth water inlet pump for mud-water separation. The membrane assembly 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 the second aeration pump.

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

[0016] Compared with the prior art, the present invention has the following advantages: direct ammonia oxidation has a wide range of action, and can convert ammonia nitrogen into hydroxylamine under aerobic conditions of C / N 5-20 and pH 7-10, and further convert it into nitrogen, achieving less nitrate nitrogen and nitrite nitrogen in the process of simultaneous denitrification and carbon removal, and can also overcome the inhibition of excessive organic matter concentration in traditional treatment processes; the advanced oxidation technology of catalytic ozone oxidation can not only further degrade organic matter in biochemical effluent, but also avoid the generation of membrane concentrate. As a new type of leachate treatment system for domestic waste incineration plants that couples biochemical treatment and advanced oxidation technology, it has the advantages of short process, small footprint, simple maintenance and operation, no need for expensive external carbon source, and low investment and construction cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the system for treating leachate from municipal solid waste incineration plants based on direct ammonia oxidation.

[0018] Explanation of the serial numbers in the figure: 1 water inlet pump; 2 coagulation stirring tank; 3 the first stirring paddle; 4 inclined plate sedimentation tank; 5 intermediate water tank; 6 filter pump; 7 multi-media filter; 8 the first water inlet pump; 9 anaerobic hydrolysis acidification reactor; 10 the second stirring paddle; 11 the first sedimentation tank; 12 the second water inlet pump; 13 direct ammonia oxidation reactor; 14 the first aeration head; 15 the first aeration pump; 16 the second sedimentation tank; 17 the third water inlet pump; 18 heterotrophic denitrification reactor; 19 the fourth water inlet pump; 20 membrane bioreactor; 21 the second aeration head; 22 the second aeration pump; 23 membrane module; 24 mixed liquor reflux pump; 25 the fifth water inlet pump; 26 catalytic ozone oxidation reactor; 27 the third aeration head; 28 catalyst tray; 29 ozone generator; 30 liquid oxygen storage tank; 31 evaporator; 32 water outlet pump. Specific implementation methods

[0020] Below in conjunction with the embodiment of the present invention, the technical scheme of the present invention is clearly and completely described, it is obvious that the described embodiment is only a part of the embodiment in the present invention, rather than all the embodiments. Based on the embodiment in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the scope of protection of the present invention. Unless otherwise specified, the equipment and reagents used in the present invention are conventional commercial products in the field of the present technology.

[0021] The term "including" and its variations used in the present invention represent open inclusion, that is, "including but not limited to". Unless otherwise stated, the term "or" means "and / or". The term "based on" means "based at least in part 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.

[0022] This embodiment provides a method for treating leachate from a domestic waste incineration plant based on direct ammonia oxidation, the method being implemented in the above-mentioned system, such as Figure 1 As shown, the 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 a municipal solid waste incineration plant; specifically, the method comprises the following steps:

[0023] (1) Pretreatment to remove suspended solids and colloids in leachate from a municipal solid waste incineration plant; specifically, firstly, flocs are formed in a coagulation and stirring tank 2 by a first stirring paddle 3, and then flocs with a relatively large density (ρ>1) in the leachate are removed by an inclined plate sedimentation tank 4, and finally, suspended solids (ρ≤1) in the leachate are removed by a multi-media filter 7;

[0024] (2) the leachate treated by the multi-media filter enters the anaerobic hydrolysis acidification reactor 9 for anaerobic hydrolysis acidification treatment, and the sludge and the leachate are mixed evenly by the second stirring paddle 10 to increase the content of volatile fatty acids in the leachate;

[0025] (3) the leachate after being treated by the anaerobic hydrolysis acidification reactor enters the first sedimentation tank 11, the leachate is separated from the sludge to obtain a supernatant;

[0026] (4) the supernatant after the treatment in step (3) enters the direct ammonia oxidation reactor 13 for simultaneous denitrification and carbon removal, and air enters the direct ammonia oxidation reactor through an aeration pipe, and the dissolved oxygen in the reactor is controlled to be maintained at 6 mg / L;

[0027] (5) the leachate after being treated by the direct ammonia oxidation reactor enters the second sedimentation tank 16, and the leachate and the sludge are separated again to obtain a supernatant;

[0028] (6) the supernatant after the treatment in step (5) enters the heterotrophic denitrification reactor 18 for denitrification treatment, and the nitrate nitrogen and nitrite nitrogen remaining in the leachate are converted into nitrogen gas;

[0029] (7) The leachate after being treated by the heterotrophic denitrification reactor enters the membrane bioreactor 20 for mud-water separation; at the same time, under the action of the mixed liquid reflux pump 24, part of the mixed liquid is refluxed to the front end of the heterotrophic denitrification reactor, which can replenish sludge for the heterotrophic denitrification reactor on the one hand, and further remove residual nitric nitrogen on the other hand;

[0030] (8) The leachate treated by the membrane bioreactor enters the catalytic ozone oxidation reactor 26 to deeply treat the organic matter and reduce the chromaticity of the leachate.

[0031] Example 1

[0032] The leachate was treated by direct ammonia oxidation reactor in the above treatment system. When the hydraulic retention time was 8 days, the reactor temperature was 30°C, and the dissolved oxygen was controlled at 6 mg / L, ammonia nitrogen was reduced from 1202.9 mg / L to 104.2 mg / L, and the removal rate was about 91.3%; TN was reduced from 1992.2 mg / L to 676.8 mg / L, and the removal rate was about 66.0%; COD was reduced from 23598.0 mg / L to 6050.2 mg / L, and the removal rate was about 74.4%.

[0033] Example 2

[0034] The catalytic ozone oxidation reactor in the above treatment system was used to treat the biochemical effluent. An aluminum-based catalyst was added and the ozone aeration volume was 1.5L / min and the power was 50% for 2 hours. The COD was reduced from 566.4mg / L to 105.6mg / L, and the removal rate was about 81.4%. At the same time, the chromaticity was reduced from 400 times to 40 times, and the removal rate was 90%.

[0035] The leachate treatment system for a domestic waste incineration plant of the present invention can effectively solve the existing problems of leachate treatment and make the treated effluent meet the emission standards; and there is no need to add expensive carbon sources, which simplifies the treatment process, reduces the floor space, and reduces the construction investment and operating costs to a certain extent.

[0036] The above description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is obvious that the above invention can be subjected to many changes and variations. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A system for treating leachate from a municipal solid waste incineration plant based on direct ammonia oxidation, characterized in that: It comprises a main treatment system, which comprises 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 water inlet of the first sedimentation tank, and the water outlet of the first sedimentation tank is connected to the water inlet of the direct ammonia oxidation reactor; The water outlet of the direct ammonia oxidation reactor is connected to the water inlet of the second sedimentation tank, and the water outlet of the second sedimentation tank is connected to the water inlet of the heterotrophic denitrification reactor; the water outlet of the heterotrophic denitrification reactor is connected to the water inlet of the membrane bioreactor; the membrane water outlet of the membrane bioreactor is connected to the water inlet of the catalytic ozone oxidation reactor, and the effluent of the catalytic ozone oxidation reactor flows into the water outlet bucket.

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

3. The system for treating leachate from a municipal solid waste incineration plant 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, and further convert it into nitrogen gas, with only a small amount of nitrate nitrogen and nitrite nitrogen generated; at the same time, 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 a municipal solid waste incineration plant 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 direct ammonia oxidation effluent are reduced to nitrogen gas under the action of heterotrophic denitrifying bacteria; and then part of COD is removed under the action of aerobic bacteria.

5. The system for treating leachate from a municipal solid waste incineration plant based on direct ammonia oxidation according to claim 1, characterized in that: A mixed liquid reflux pump is arranged in the membrane bioreactor to reflux the mixed liquid to the front end of the heterotrophic denitrification reactor; On the one hand, this process provides sludge for the heterotrophic denitrification reactor, and on the other hand, it further removes the residual nitric nitrogen in the membrane bioreactor.

6. The system for treating leachate from a municipal solid waste incineration plant based on direct ammonia oxidation according to claim 1, characterized in that: In the catalytic ozone oxidation reactor, the refractory organic matter in the biochemical effluent is adsorbed on the catalyst surface through the action of chemical bonds, and further reacts with ozone in the gas phase or liquid phase to be removed.

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

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

9. The system for treating leachate from a municipal solid waste incineration plant based on direct ammonia oxidation according to claim 1, characterized in that: The water outlet of the second sedimentation tank is connected to the water inlet of the heterotrophic denitrification reactor through the third water inlet pump, and the water outlet of the heterotrophic denitrification reactor is connected to the water inlet of the membrane bioreactor through the fourth water inlet pump for mud and water separation. The membrane assembly 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 the second aeration pump.

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

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