WO2014094484A1

WO2014094484A1 - Garbage leachate treatment method and system

Info

Publication number: WO2014094484A1
Application number: PCT/CN2013/085029
Authority: WO
Inventors: 徐文军; 兰建伟; 苏志锋; 赵剑锋; 朱春福
Original assignee: 深圳市能源环保有限公司
Priority date: 2012-12-18
Filing date: 2013-10-11
Publication date: 2014-06-26
Also published as: CN102976543A

Abstract

A garbage leachate treatment method, comprising the following processing steps: firstly, adding a coagulant to the leachate, and conducting coagulative precipitation pretreatment; evaporating and concentrating the pretreated leachate to obtain condensed water; distilling the condensed water with ammonia; removing biodegradable organic matter in the water distilled with ammonia, and conducting biological denitrogenation treatment. Also disclosed is a garbage leachate treatment system incorporating the treatment method.

Description

Description Method and system for treating garbage leachate

Technical field

The present invention relates to a sewage treatment method, to a system for carrying out the process, and more particularly to a waste leachate treatment method and system. Background technique

With the rapid development of the economy, the continuous improvement of people's living standards and the rapid development of modern cities, urban domestic garbage has also grown rapidly, and the problem of domestic garbage pollution has become increasingly prominent. At present, domestic waste treatment methods mainly include incineration, composting, mechanical treatment and landfills. The traditional urban domestic waste landfill treatment is subject to more and more restrictions. According to the basic principles of harmlessness, reduction and resource utilization of municipal solid waste disposal, domestic waste incineration power generation has become a way to solve the urban domestic waste in recent years. In the new direction, the construction of waste incineration plants has developed rapidly in recent years. During the storage, transfer, transportation and stacking of garbage, a variety of metabolites and water are produced due to anaerobic fermentation, decomposition of organic matter, rainwater leaching, etc., forming a highly concentrated organic wastewater, garbage leachate. Untreated leachate not only contaminates soil and surface water, but also contaminates water sources through groundwater flows, posing a permanent threat to human health and the environment. Therefore, pollution control of waste leachate has become an important component of waste incineration treatment. The amount of landfill leachate produced and the water quality change vary greatly with the seasons. Leachate composition is complex, and studies have shown that there are 34 organic pollutants in landfill leachate. Among them, there are 6 kinds of alkyl olefins, 19 kinds of carboxylic acids, 5 kinds of esters, 10 kinds of alcohols and phenols, 10 kinds of aldehydes and ketones, 7 kinds of amides, 1 kind of aromatic hydrocarbons, and 5 kinds of other kinds. Among them, there are one type of carcinogen, four kinds of cancer-promoting substances and auxiliary carcinogens, and one type of mutation, which are listed in the "blacklist" of environmental priority pollutants in China. The main characteristics of leachate compared with general urban sewage are as follows:

1. The composition of pollutants is complex and variable, and the water quality changes greatly.

The leachate in the incineration plant is relatively fresh, and most of the organic matter contained in it is humic polymer carbohydrates and medium molecular weight fulvic acid, and contains heterocyclic aromatic hydrocarbon compounds such as benzene, naphthalene and phenanthrene, polycyclic aromatic hydrocarbons, Phenols, alcohols, aniline compounds and other refractory organics, so the water quality is quite complex, there are many types of pollutants, and the concentration has short-term fluctuations and long-term changes of complexity.

2. High concentration of organic pollutants (high COD concentration)

The leachate concentration of the incineration plant is generally around 40,000-8,000 mg/l. It is difficult to process it to the required emission standards using traditional biochemical treatment processes.

3. High ammonia nitrogen concentration

The concentration of ammonia nitrogen in the leachate of the incineration plant is relatively high, generally around 1000-2500 mg/l, requiring a high denitrification capacity in the treatment process.

4. High salt content

Since the waste contains more salt, resulting in a higher salt content in the leachate, leachate high conductivity 30000-40000us / _C m. 5. The leachate of the incineration plant is acidic, and the pH is lower. The incineration plant leachate contains a large amount of organic acid, and the pH value is low, generally around 4-6.

6. Incineration plant leachate water fluctuations are large

Affected by factors such as garbage collection, climate and seasonal changes, the amount of leachate in the waste incineration plant fluctuates greatly. Especially the seasonal changes have a great influence on the change of the leaching liquid. Generally, the summer leachate output is relatively large, while the winter is relatively small.

7. Nutrient imbalance

For biological treatment, the imbalance of nutrients in the leachate of waste incineration power plants is mainly reflected in the low content of pity and high ammonia nitrogen content relative to C0D and BOD indicators. Numerous studies and engineering examples show that the imbalance in nutrient ratio in landfill leachate is an important cause of the difficulty in treating leachate.

8. Have a stench

The leaching of the incineration plant emits a variety of malodorous gases, requiring deodorization measures in the treatment system to control the fouling of the atmosphere. At present, the most widely used leachate treatment process in domestic waste incineration plants is the "biochemical + membrane" treatment process technology. According to the different types of membrane biochemical reactors, the "biochemical + membrane" treatment process can be subdivided into "regulation tank + pretreatment + anaerobic + SMSBR + NF (nanofiltration) or R0 (reverse osmosis)" and "adjustment" Pool + anaerobic + MBR + NF (nanofiltration) or R0 (reverse osmosis) "two. The main difference between the two is the MBR and SMSBR systems after anaerobic. In the "membrane + biochemical" process, once the NF (or R0) system is put into operation, about 30% of the membrane concentrate is produced. Due to the high organic matter concentration, high salt content, strong fouling and complex pollutant composition of the membrane concentrate, the treatment of the concentrate is quite difficult, and there is no economically reasonable mature treatment process at home and abroad. At present, the final outlet of the concentrate cannot be effectively solved. Therefore, the NF (nanofiltration) or R0 (reverse osmosis) advanced treatment device using the "biochemical + membrane" treatment process cannot be continuously put into operation, and most of the time is not passed. The membrane is directly treated and discharged directly. The effluent can only meet the three-level discharge requirements in the Integrated Wastewater Discharge Standard (GB8978-1996).

In addition, waste leachate is currently treated by a "thermal evaporation" process. The waste leachate is directly treated into the evaporative concentration system for treatment. The ammonia nitrogen and COD content in the condensed water produced by the evaporative concentration system are both high and the nutrient ratio is imbalanced. The ammonia denitrification process is required to reduce the ammonia nitrogen before the biochemical system enters the water. And COD content, in order to reduce the subsequent biochemical system load, so that the system effluent reaches the sewage comprehensive treatment standard (GB8978-1996)-level standard after treatment. At present, the main process for reducing ammonia nitrogen and COD content is ammonia stripping method; ammonia stripping process has low deamination efficiency and unstable operation, and the deamination efficiency of the ammonia stripping tower decreases with the operation of the system, and the ammonia stripping process The problem of ammonia gas going in the process; the unstable operation of the system makes the influent water quality of the biochemical system fluctuate significantly, which seriously affects the stable operation of the biochemical system and the effluent quality.

Summary of the invention

In order to solve the problem of reducing ammonia nitrogen and COD content in the waste leachate treatment process, the ammonia stripping process has low deamination efficiency, unstable operation, ammonia gas outflow during ammonia stripping process, and biochemical system. Water quality fluctuations are obvious, seriously affecting students A series of problems such as stable operation of the system and effluent quality, the present invention provides a method and system for treating waste leachate, which adopts a refined method for deamination of the evaporating condensed water of the waste leachate, thereby effectively solving the current problem. The use of ammonia stripping method in the process of deamination of high concentration ammonia nitrogen wastewater has low deamination efficiency, unstable operation, ammonia gas outflow during ammonia stripping process, and the fluctuation of influent water quality of biochemical system. A series of problems affecting the stable operation of the biochemical system and the quality of the effluent.

One of the technical problems to be solved by the present invention is to provide a leachate treatment method for a waste incineration plant, which can effectively solve the low deamination efficiency and operation existing in the deamination process of the high concentration ammonia nitrogen wastewater by the ammonia stripping method. The problems of instability, ammonia gas loss during the ammonia stripping process, and fluctuations in the influent water quality of the biochemical system, seriously affecting the stable operation of the biochemical system and the quality of the effluent water.

Say

The second technical problem to be solved by the present invention is to provide a waste incineration plant leachate treatment system for carrying out the above-mentioned garbage leachate treatment process. The technical solution adopted by the present invention to solve one of the technical problems is as follows: The book proposes a waste incineration plant leachate treatment method, which is characterized in that it comprises the following process steps:

a, adding a coagulant to the leachate for coagulation and precipitation pretreatment to remove suspended solids;

b. The pretreated leachate is subjected to evaporation concentration treatment to obtain condensed water, and the residual residue and residual liquid are removed;

c. The condensed water is subjected to ammonia distillation to remove ammonia nitrogen;

d. The ammonia-treated water is subjected to the removal of biochemical organic matter and biological nitrogen removal to achieve the “Sewage Integrated Emission Standard” (GB8978-1996)-level emission standard (including total nitrogen index) or industrial use.

In the step b, the pH of the leachate is controlled at 11. 0-11. 5; in the step b, the first evaporation can is controlled. The effluent temperature of the effluent of the evaporating system is controlled at a temperature of 10 to 5 ° C. In the step c, the pH of the inlet water is controlled at 10. 5-11. 0, the pressure at the top of the distillation tower is controlled to be normal pressure, and the reflux ratio of the ammonia column is controlled at 0. 7-0. 8. The temperature of the ammonia water is controlled at 6 CTC. Hereinafter; in the step d, the pH is controlled to be 7-9.

The technical solution adopted by the present invention to solve the second technical problem thereof is as follows: A garbage leachate treatment system is proposed, which comprises a regulating tank connected to the leachate, and sequentially accesses the pretreatment system, the evaporation concentration system after the adjusting tank, An ammonia nitrogen removal system and an MBR system (membrane bioreactor); the leachate after the conditioning tank is connected to a pretreatment system, the effluent of the pretreatment system is connected to an evaporation concentration system, and the condensation water of the evaporation concentration system is connected Into the ammonia nitrogen removal system, the effluent of the ammonia nitrogen removal system is connected to the MBR system to remove biodegradable organic matter and perform biological denitrification, and the effluent is discharged or reused; and a thickener is further provided, the evaporation concentration system The evaporation residual liquid is connected to the thickener for treatment; a sludge concentration tank is also provided and a centrifugal dewatering machine is arranged after the sludge concentration tank; the sludge produced by the pretreatment system and the dirt generated by the MBR system Mud is connected to the sludge concentration tank, the supernatant of the sludge concentration tank and the post-mortem of the centrifugal dewatering machine are connected to the pretreatment system; The sludge treated by the water machine and the concentrated liquid produced by the thickener enter the garbage bin; the characteristic is: the ammonia nitrogen The removal system is a vaporized ammonia system, and the ammonia water produced by the ammoniated system is sent to a power plant denitration device.

The adjusting tank of the present invention mainly comprises adding an automatic grill slag removing device in front of the adjusting tank and setting and operating a submersible mixer in the pool to prevent sludge in the leachate from being deposited in the regulating tank;

The adjusting tank is further provided with an air inlet, and the inlet port of the Roots blower of the subsequent MBR system is connected with the exhaust port of the regulating tank, so that the odor in the regulating tank is introduced into the nitrification reaction tank in the MBR system, and the microorganisms in the pool are passed. Degrade the odor.

The adjustment tank is also connected with the photodecomposition oxidation deodorization system. When the Roots blower is stopped, the odor of the adjustment tank collected by the pipeline is sent to the photolysis catalytic oxidation deodorization system for treatment, and the treated odor is stopped. The pollutants in the indicators have reached the requirements of the "Integrated Emission Standards for Air Pollutants" (GB16297-1996) and the "Emission Standards for Odor Pollutants" (GGB14554-1993). The photocatalytic oxidation and deodorization system mainly comprises a photolysis oxidation device, a reaction box, a water circulation spray tower, a wind machine and the like.

The pretreatment system of the present invention comprises: the pretreatment system comprises a reaction tank provided with a stirring device, a dosing device and a setting for placing a coagulant/coagulant into the reaction cell, and a first-stage machine for coagulation and sedimentation. A stirring book clarifier and a secondary mechanical agitating clarifier, and a sludge concentration dewatering device disposed after the clarifier.

The evaporative concentration system of the present invention comprises a five-stage preheating system, a multi-effect evaporation concentration system, a condensate system, an automatic exhaust system, a vacuum system, an automatic control system, a pickling system, and the like. After the pre-treated waste leachate is preheated in five stages, it is successively entered into a multi-effect evaporation tank for evaporation and concentration. Most of the pollutants are discharged in the form of evaporation residue/residual liquid (the evaporation residue is COD at 300,000 mg/ 1 or more solid-liquid mixture), and sent to the garbage bin to enter the incinerator with garbage to be incinerated.

The ammoniated system of the invention mainly comprises: a ammonia distillation tower (fine tower), a condenser, a reflux tank, a reflux pump, a bottom pump, a reboiler; the condensed water produced by the evaporation concentration system is pre-prepared by the fine tower liquid After the heat enters the fine tower, the bottom liquid is heated by the reboiler to generate steam in the tower. The steam in the tower and the feed liquid are gas-liquid exchanged in the tower. As the steam rises, the liquid is volatile and light. The components are taken away; the bottom liquid of the bottom of the tower is discharged from the condensed water after deamination through the bottom pump, and the secondary steam generated at the top of the tower enters the condenser, and a part of the condensate is refluxed into the ammonia distillation tower, and a part is sent as a distilled ammonia water. To the ammonia tank.

The hydrogenation process proposed by the invention is compared with the prior art ammonia stripping process as shown in Table 1.

Table 1: Comparison table of steam ammonia process and ammonia stripping process of the utility model

The present invention, the steaming ammonia process, the prior art ammonia stripping process

Influent index C0D _Cr =1500-2500mg/l, NH ₃ -N=1000-1500mg/l, total nitrogen (mg/1 ) <200

C0D _Cr < 1000mg/l , NH3- N<80 mg/1 C0D _Cr : 1500-2000mg/l , NH3- N: 400-500 water output index

Total nitrogen < 10003⁄4/1 mg/1 , total nitrogen: 500- 600mg/l

Ammonia nitrogen removal rate >95 % <90%

Approximately 5-10% of dilute ammonia water by-products can be obtained

No by-products, and the tail gas produced by the blow-off requires other ¹ " wide products, which can be used as a denitrification source for waste incineration power plants.

System processing.

Material (SNCR), the recycling of resources. Economic benefit 10 yuan / ton (waste water)

The measured data of the effluent quality of the waste leachate treated by the process proposed by the present invention is shown in Table 2:

Table 2: Measured data of leachate effluent quality treated by this process

Say

It can be seen from the data of Tables 1 and 2 that the beneficial effects of the method and system for treating the litter leachate proposed by the present invention are to remove ammonia nitrogen by steaming, and the beneficial effects are as follows:

1. The ammoniated system can be operated in a long-term, continuous and stable manner. During normal operation, the ammonia nitrogen removal rate exceeds 95%, which effectively solves the problem of poor ammonia removal efficiency and unstable deamination efficiency during the ammonia stripping process. Dehydration efficiency is obviously insufficient;

2. The dilute ammonia water by-product obtained by the ammonia distillation system with a mass fraction of about 10% can be used as a raw material for the waste incineration power plant SNCR, thereby turning waste into treasure and realizing the comprehensive utilization and recycling of resources.

3. The ammoniated system is highly efficient and stable. When the subsequent MBR treatment is carried out, the MBR residence time can be greatly shortened, which can greatly reduce the project footprint and civil construction investment. At the same time, due to the decrease of ammonia nitrogen in the MBR, the power consumption of the MBR process will be reduced by half compared with the original process, which greatly reduces the operating cost of the biochemical system.

4. Make the whole garbage leachate treatment process more stable, greatly reduce the project's land area and civil construction investment, consume less electricity in daily operation, and have obvious economic benefits.

DRAWINGS

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, in which:

1 is a flow chart of the overall process of the garbage leachate treatment method and system proposed by the present invention.

2 is a process flow diagram of an embodiment of a pretreatment process in a waste leachate treatment method and system according to the present invention.

3 is a process flow diagram of an embodiment of an evaporation and concentration process in a waste leachate treatment method and system according to the present invention.

4 is a process flow diagram of an embodiment of an ammonia removal process in a waste leachate treatment method and system according to the present invention.

FIG. 5 is a process flow diagram of an embodiment of a biochemical treatment process in a waste leachate treatment method and system according to the present invention.

detailed description The garbage leachate treatment method proposed by the invention comprises the following process steps:

b. The pretreated leachate is subjected to evaporation concentration treatment to obtain condensed water to remove contaminant residue and residual liquid; c. pre-treating the condensed water for ammonia distillation to remove ammonia nitrogen;

In the step a, the pH of the leachate is controlled to be 10. 0-10. 5; in the step b, the evaporation temperature of the first evaporation can is controlled to be 105-130 ° C, when multi-effect evaporation is employed , in the step c, the control of the ammonia system is controlled, and the evaporation temperature of the effluent is controlled by the multi-effect evaporation system is 10. 5-11. 0; The control of the ammonia reflux temperature is below 6 CTC; in the above, the pH of the water is at a pressure of 10. 5-11. In step d, the pH is controlled at 7-9.

The present invention also proposes a book system for implementing the above-described garbage leachate treatment method. As shown in FIG. 1, the system includes a conditioning tank connected to the leachate, a pretreatment system, an evaporation concentration system, an ammonia nitrogen removal system, and an MBR system (membrane bioreactor) after the conditioning tank; The leachate after the conditioning tank is connected to the pretreatment system, the effluent of the pretreatment system is connected to the evaporation concentration system, the condensed water of the evaporation concentration system is connected to the ammonia nitrogen removal system, and the effluent access of the ammonia nitrogen removal system The MBR system removes biodegradable organic matter and performs biological nitrogen removal, and the effluent is discharged or reused; and a thickener is disposed, and the evaporated residual liquid of the evaporation concentration system is connected to the thickener for treatment; a sludge concentration tank and a centrifugal dewatering machine after the sludge concentration tank; sludge generated by the pretreatment system and sludge generated by the MBR system are connected to the sludge concentration tank, the sludge concentration tank The supernatant and the post-mortem of the centrifugal dewatering machine are connected to the pretreatment system; the sludge treated by the centrifugal dehydrator and the concentrate produced by the thickener are discharged into the garbage ; Wherein the ammonia removal system for the steam system of the ammonia, aqueous ammonia, the ammonia evaporation system is produced by the power plant sent denitration apparatus.

The specific implementation of each system is as follows:

Regulation pool

The adjustment tank of the present invention mainly comprises adding an automatic grid slag removing device in front of the regulating tank and installing and operating a submersible mixer in the pool to prevent sludge in the leachate from being deposited in the regulating tank;

The adjustment tank is also connected with the photodecomposition oxidation deodorization system. When the Roots blower is stopped, the odor of the adjustment tank collected by the pipeline is sent to the photolysis catalytic oxidation deodorization system for treatment, and the treated odor is stopped. The indicators of various pollutants meet the requirements of the Comprehensive Emission Standards for Air Pollutants (GB16297-1996) and the Emission Standards for Odor Pollutants (GGB14554-1993). The photocatalytic oxidation deodorization system mainly includes a photolysis oxidation device, a reaction box, a water circulation spray tower, a fan and the like.

The waste leachate from the garbage incineration bin of the waste incineration plant is lifted to the leachate regulating tank through the lift pump in the leachate collection tank to achieve the purpose of homogenization and equalization of the leachate, and to reduce the hydraulic load and water quality changes for the subsequent treatment facilities. To create pre-conditions for maintaining stable operation of the system, At the same time, some organic substances in the leachate are hydrolyzed, acidified and methanated in the conditioning tank. Adjust the pool hydraulic retention time to 7-10 days. Since the garbage leachate from the garbage bin contains more solid particles, in order to prevent the solid particles from entering the regulating tank, an automatic grill slag removing device is installed in front of the regulating tank, and the leachate is pretreated by the dross before entering the regulating tank. To remove solid particles having a particle size greater than 0.5-lmm. The sludge in the leachate is prevented from depositing in the conditioning tank by setting and operating a submersible mixer in the conditioning tank. For the odor that is dissipated by the regulating tank, the traditional treatment method is to send it to the garbage bin of the garbage power plant as a gas supply to the incinerator. Although this method solves the problem of odor overflow, it affects the air pressure balance of the garbage bin. The innovations of the process here are as follows: The adjustment tank is provided with an air inlet, and the inlet of the Roots blower of the subsequent MBR system is connected with the exhaust port of the regulating tank, thereby introducing the odor in the regulating tank into the nitrification reaction tank in the MBR system. The odor is degraded by microorganisms in the pool. When the Roots blower is out of service, the odor of the adjustment tank collected by the pipeline is sent to a photolysis catalytic oxidation and deodorization system for treatment. The deodorization system mainly includes a photolysis oxidation device, a reaction tank, and a water circulation spray tower. , fans and other equipment.

Pretreatment system

2 is a process flow diagram of an embodiment of a book pretreatment process in a waste leachate treatment method and system according to the present invention. The figure shows that in the present embodiment, the pretreatment system includes a reaction tank provided with a stirring device, a dosing device and a setting for placing a coagulant/coagulant into the reaction cell, and a first-stage mechanical stirring for coagulation and sedimentation. A clarifier and a secondary mechanical agitator clarifier, and a sludge concentration and dewatering device disposed after the clarifier. The pretreatment process improves the existing waste leachate pretreatment process, adopts two-stage coagulation sedimentation to ensure the effluent quality of the pretreatment system, and the Ca ²⁺ , Mg ²⁺ , S0 ₄ ² - etc. in the wastewater The fouling material is treated to ensure long-term, stable operation of the subsequent thermal evaporation system.

1. First-stage coagulation sedimentation

The leachate after the slag removal in the conditioning tank is uniformly sent to the reaction tank by the regulating tank lifting pump, and the lime is added to the tank to adjust the pH thereof to about 10~10. 5, most of the heavy metals, Mg ²⁺ , F ―, S0 ₄ ² —, macromolecular COD and the like react with lime to form a precipitate, which is then pressurized and sent to a first-stage mechanical stirring clarifier to complete solid-liquid separation.

2, secondary coagulation sedimentation

In order to ensure that the suspended solids in the effluent of the pretreatment system meet the requirements of the subsequent evaporation system, the first-stage coagulation sediment supernatant effluent enters the secondary mechanical agitation clarifier for solid-liquid separation. Because lime is added during the first-stage coagulation and sedimentation process, Ca ²⁺ ions are introduced, and other easily fouling substances in the water are present, and calcium sulfate and calcium oxalate are in a saturated state, and it is easy to be on the heat exchange tube after heating. Fouling, in order to ensure the long-term stable operation of the subsequent evaporation system and reduce the number of cleanings, it is necessary to treat the scale-prone materials. Therefore, in the secondary coagulation and sedimentation process, the method of adding Na ₂ C0 ₃ is adopted, so that Ca ²⁺ which is easy to cause scaling of the subsequent evaporation system is removed by CaC0 ₃ precipitation, and at the same time, the co-precipitation of Si is strengthened, and the precipitation is minimized. The content of Ca (C00) ₂ and CaS0 ₄ in the wastewater is to slow down the scaling rate of the subsequent evaporation system and reduce the number of shutdowns and cleaning of the system to ensure continuous and stable operation of the system. The supernatant of the secondary clarifier enters the intermediate pool as the water in the evaporation system;

The sludge generated in the first-stage and second-stage mechanical stirring clarifiers is separately pressurized and transported to the sludge concentration tank through the sludge transfer pump for sludge concentration, and the supernatant in the concentration tank is returned to the secondary mechanical stirring clarifier for further treatment. The concentrated sludge is separated from the solid-liquid by the sludge centrifugal dewatering machine, and the dehydrated clear liquid is also refluxed into the secondary mechanical stirring clarifier for further treatment. After centrifugal dewatering, the dry sludge with a moisture content of about 80% is pressurized and transported to the garbage bin. The garbage enters the furnace and is incinerated. After the two-stage coagulation and sedimentation treatment of the waste leachate, the SS, COD, BOD, etc. in the wastewater are significantly reduced, and the Ca ²⁺ is also reduced to 3⁄4≡100mg/l to ensure the influent water quality requirements of the subsequent evaporation system.

After the waste leachate is treated by two-stage coagulation and sedimentation, the main indicators of the water quality of the inlet and outlet water are shown in Table 3 below:

Table 3 Main indicators of water quality of inlet and outlet water after two-stage coagulation and sedimentation treatment

Say

Evaporation system

3 is a process flow diagram of an embodiment of an evaporation and concentration process in a waste leachate treatment method and system according to the present invention. This embodiment is specifically as follows:

1. Influent water quality and effluent quality

According to the effluent discharge requirements of the pretreatment system and the characteristics of the evaporative concentration system, determine the influent water quality of the multi-effect evaporative concentration system, see Table 4: Table 4 Multi-effect evaporation system influent water quality

2. Evaporation system efficiency and choice of evaporator form

Considering the combination of investment and operating costs, the waste leachate evaporation and concentration system after two-stage coagulation and sedimentation uses a multi-effect evaporation system. For different water inflows, there are different options for three-, four-, and five-effect evaporation systems. This embodiment is described in terms of a four-effect evaporation system.

Regarding the evaporator form, a combination of a natural circulation evaporator and an external thermal forced circulation evaporator is selected. 3, multi-effect evaporation system process

The evaporation system includes a five-stage preheating system, a four-effect evaporation system, a condensate system, an automatic exhaust system, an evacuation system, an automatic control system, a pickling system, and the like. After the pre-treated waste leachate is preheated in five stages, it is sequentially introduced into the I~IV effect evaporation tank for evaporation concentration. Most of the pollutants are discharged in the form of evaporation residue/residual liquid (the evaporation residue is COD at 300,000). Mg/1 or more solid-liquid mixture), and sent to the garbage bin to enter the incinerator for incineration with waste; the leachate is evaporated and condensed to become a colorless and transparent liquid, the concentration of which is greatly reduced, COD and NH ₃ - N is basically below 2500 mg/l. The system realizes automatic operation without manual intervention under normal working conditions.

Ammonia system

4 is a process flow diagram of an embodiment of a process for treating waste water in a garbage leachate according to the present invention.

At present, the deamination process for nitrogen wastewater from high-concentration ammonia such as landfill leachate is based on ammonia stripping. In the process of ammonia stripping, there are usually insufficient ammonia stripping efficiency, large external conditions (such as inlet water temperature and ra value), and significant deamination efficiency. The finely-applied device commonly used in petroleum and chemical industries has been successfully applied to the deamination process of high-concentration ammonia-nitrogen wastewater such as waste leaching liquid, which can effectively solve the problem of ammonia stripping in the process of deamination of high-concentration ammonia-nitrogen wastewater. The efficiency is not good, and the efficiency of deamination is reduced.

1. Water quality of effluent ammonia system and effluent:

The influent of the ammoniated system is the condensed water produced by the waste leachate treated by the evaporation concentration system. The main indicators of the inflow and outflow of the system are shown in Table 5:

Table 5 Water quality indicators of the ammonia system

2, the working principle and type of fine equipment

In the process of the ammonia-smelting system, a unit operation (fine column/steaming tower) which is very common and important in the petrochemical, pharmaceutical and other industries is adopted. The basic principle of fine smelting is that the vapor enters from the bottom of the tower and is in countercurrent contact with the descending liquid. The mass transfer is achieved in the two-phase contact, and the volatile (low-boiling) component in the descending liquid is continuously transferred to the vapor, which is difficult in the vapor. The volatile (high boiling point) component is continuously transferred to the falling liquid. The closer the vapor is to the top of the column, the higher the concentration of the volatile component, and the closer the falling liquid is to the bottom of the column, the more the volatile component is enriched and reaches the composition. The purpose of separation. The vapor rising from the top of the column enters the condenser, and a portion of the condensed liquid is returned as reflux to the top of the column into the fine column, and the remaining portion is taken as the eluate. The liquid flowing out from the bottom of the column, a part of which is sent to the reboiler, after the heat is evaporated, the vapor is returned to the column, and the other part of the liquid is taken out as a residue.

The types of fine towers are divided into plate towers and packed towers according to structure; atmospheric pressure towers, pressure towers and vacuum towers are divided according to working pressure; combined with treatment load, operating cost and ease of operation, the process adopts It is a constant pressure - single effect - plate type fine tower. The ammonia distillation system mainly includes: an ammonia distillation tower (fine tower), a condenser, a reflux tank, a reflux pump, a bottom pump, and a reboiler; the condensed water produced by the evaporation concentration system is preheated by the fine tower liquid to enter the fine In the tower, the bottom liquid is heated by the reboiler to generate steam in the tower. The steam in the tower and the feed liquid are gas-liquid exchanged in the tower, and the volatile light components in the liquid are continuously taken away as the steam rises. The bottom liquid is discharged from the bottom of the bottom by the bottom pump, and the secondary steam generated at the top of the tower enters the condenser. A part of the condensate is refluxed into the ammonia tower, and a part of the condensed water is sent to the ammonia tank as distilled water.

3. Process of ammonia distillation system

The ammonia distillation system adopts the atmospheric pressure single-effect fine-tuning process, and the process flow chart is shown in Figure 4. The condensed water produced by the evaporative concentration system is preheated through the fine column liquid to the fine column. The bottom liquid is heated by the reboiler to generate steam in the tower, and the steam in the tower is exchanged with the feed liquid in the tower, and the volatile components in the liquid are continuously taken away as the steam rises; The bottom kettle liquid discharges the decondensed condensed water through the bottom pump, and the secondary steam generated at the top of the tower enters the condenser. A part of the condensate flows back into the ammonia tower, and a part of the condensed water is sent to the ammonia tank as distilled hydrogenated water. After evaporating the condensed water through the ammonia distillation system, the ammonia nitrogen is reduced from about 1500 mg/l to less than 80 mg/l, and the C-book OD is also reduced from 2500 mg/l to less than 1000 mg/l; at the same time, the mass fraction obtained by the ammonia distillation system is 5- 10% dilute ammonia water by-product, can be used as raw material for SNCR of waste incineration power plant, thus turning waste into treasure and realizing the comprehensive utilization and recycling of resources.

MBR system

Fig. 5 is a process flow diagram showing an embodiment of a biochemical treatment process of an MBR system (membrane bioreactor) in a waste leachate treatment method and system according to the present invention.

In this process, the MBR system is used to replace the traditional biochemical system. Compared with the traditional biochemical process system, it has the characteristics of stable operation, excellent effluent quality, high volume load, small floor space and low investment cost.

1. MBR system inlet and outlet water quality

The main indicators of MBR inlet and outlet water quality are shown in Table 4:

Table 6 Main indicators of water quality of MBR system

2, MBR system process

After the effluent of the ammonia system is cooled to 35 °C, it enters the MBR (membrane bioreactor) through the lift pump, biochemically removes biodegradable organic matter and performs biological nitrogen removal to achieve the Integrated Wastewater Discharge Standard (GB8978-1996). Emissions (including total nitrogen indicators) or industrial reuse standards. The membrane biochemical reactor configures and controls suitable reaction conditions according to the influent water quantity and water quality conditions to achieve efficient denitrification and nitrification reactions and simultaneously degrade organic pollutants. In order to make full use of the carbon source in the influent to carry out the denitrification reaction, the membrane biochemical reactor adopts denitrification pre-position. The form of post-nitration can also reduce the amount of oxygen required to degrade organic pollutants in the nitrification tank. The nitrification tank of the membrane biochemical reactor is equipped with special aeration equipment according to the needs, and can culture high-activity aerobic microorganisms, so that the biodegradable organic pollutants in the sewage are almost completely degraded in the nitrification tank, and ammonia nitrogen and organic nitrogen are simultaneously oxidized. It is a nitrate; then, it enters the denitrification tank and is reduced to nitrogen in an anoxic environment to achieve the purpose of denitrification. Due to the low ammonia nitrogen and COD of the effluent quality of the ammoniated system, the microbial flora that has been continuously acclimated in the biochemical system can be propagated, and the organic matter which is difficult to degrade in the garbage leachate can be gradually degraded compared with the common sewage treatment process. High quality effluent quality can be obtained. The membrane biochemical reactor replaces the traditional secondary sedimentation tank by ultrafiltration, completely realizes the separation of mud and water, and makes the sludge concentration in the biochemical system reach 10-15g/l. The ultrafiltration membrane in the membrane biochemical reactor can be an external tubular ultrafiltration membrane or a built-in immersion plate.

Membrane.

The advantages of the MBR system in this process are:

1. The MBR system is used to replace the traditional biochemical system, and the solid-liquid separation of the book can be carried out efficiently. The separation effect is much better than the traditional sedimentation tank. The effluent water quality is good, and the effluent suspended matter and turbidity are close to zero, which can be directly reused. Realized the recycling of sewage

2. The volumetric load of the MBR system is 2 to 3 times higher than that of the traditional biochemical system; the aeration tank of the traditional sewage treatment is combined with the secondary sedimentation tank, and replaces all the process facilities of the tertiary treatment, thereby greatly reducing the land occupation. Area, saving civil construction investment.

3. The activated sludge in the MBR system can have a longer residence time, thereby greatly improving the degradation efficiency of the refractory organic matter, and the remaining sludge amount is one third less than the conventional biochemical system.

Claims

Claim

A method for treating leachate in a waste incineration plant, characterized in that it comprises the following process steps:

b. The pretreated leachate is subjected to evaporation concentration treatment to obtain condensed water, and the residual residue and residual liquid are removed; c. the condensed water is subjected to ammonia distillation treatment to remove ammonia nitrogen;

In the step a, the pH of the leachate is controlled at 11. 0-11. 5; in the step b, the evaporation temperature of the first evaporation can is controlled to be 105-130 ° C, when multi-effect evaporation is employed 5-11 The control of the influent pH is 10. 5-11. 0, controlling the reflux pressure of the ammonia column to a normal pressure, controlling the reflux ratio of the ammonia column at 0. 7-0. 8, controlling the ammonia water outlet temperature below 6 CTC; in the step d, controlling the pH value at 7- 9.

2. A landfill leachate treatment system according to claim 1, comprising a conditioning tank connected to the leachate, followed by a pretreatment system, an evaporation concentration system, an ammonia nitrogen removal system, and an MBR system (membrane organism) a leachate after the conditioning tank is connected to a pretreatment system, the effluent of the pretreatment system is connected to an evaporation concentration system, and the condensate of the evaporation concentration system is connected to the ammonia nitrogen removal system, The effluent of the ammonia nitrogen removal system is connected to the MBR system to remove biodegradable organic matter and to perform biological denitrification, and the effluent is discharged or reused; and a thickener is provided, and the evaporation residual liquid of the evaporation concentration system is connected to the thickener Processing, further comprising a sludge concentration tank and setting a centrifugal dewatering machine after the sludge concentration tank; sludge generated by the pretreatment system and sludge generated by the MBR system are connected to the sludge concentration tank , the supernatant of the sludge concentration tank and the post-mortem of the centrifugal dewatering machine are connected to the pretreatment system; the sludge treated by the centrifugal dewatering machine and the The concentrate was condensed into the garbage bins generated; wherein the ammonia removal system for the steam system of the ammonia, aqueous ammonia, the ammonia evaporation system is produced by the power plant sent denitration apparatus.

3. The refuse leachate treatment system according to claim 2, wherein the adjustment tank mainly comprises an automatic grill slag removing device installed in front of the regulating pool and a diving agitator is arranged and operated in the pool to prevent leaching. The sludge in the filtrate is deposited in the regulating tank; the regulating tank is further provided with an air inlet, and the inlet of the Roots blower of the subsequent MBR system is connected with the exhaust port of the regulating tank, thereby introducing the odor in the regulating tank into the MBR system. The nitrification reaction tank degrades the odor through microorganisms in the tank.

4. The refuse leachate treatment system according to claim 2, wherein the adjustment tank is further connected to the photodecomposition oxidation deodorization system, and when the Roots blower is stopped, the adjustment pool collected by the pipeline is The odor is sent to a photolysis catalytic oxidation deodorization system for treatment.

The waste leachate treatment system according to claim 4, wherein the photodecomposition oxidation deodorization system mainly comprises a photolysis oxidation device, a reaction tank, a water circulation spray tower, a fan and the like.

6. The garbage leachate treatment system according to claim 2, wherein the pretreatment system comprises a reaction tank provided with a stirring device, and a dosing device for applying a coagulant/coagulant to the reaction cell. And a first-stage mechanical agitation clarifier and a secondary mechanical agitation clarifier for setting and coagulation sedimentation, and a sludge concentration dewatering device disposed after the clarifier.

7. The waste leachate treatment system according to claim 2, wherein the evaporation concentration system comprises a five-stage preheating system, and multiple effects Claim

The evaporative concentration system, the condensate system, the automatic exhaust system, the vacuum system, the automatic control system, the pickling system, etc., after the pre-treated waste leachate is preheated in five stages, sequentially enters the multi-effect evaporation tank for evaporation and concentration. Most of the pollutants are discharged in the form of evaporation residue/residual liquid, and are sent to the garbage bin to enter the incinerator with the garbage for incineration.

8. The waste leachate treatment system according to claim 2, wherein the ammonia distillation system mainly comprises a ammonia distillation tower, a condenser, a reflux tank, a reflux pump, a bottom pump, a reboiler; and an evaporation concentration system. The generated condensed water is preheated by the ammonia liquid to the ammonia distillation tower, and the bottom liquid is heated by the reboiler to generate steam in the tower, and the steam in the tower is exchanged with the feed liquid in the tower, with steam. The rise continuously keeps the volatile light components in the feed liquid away; the bottom liquid of the bottom of the tower discharges the condensed water after deamination through the bottom pump, the secondary steam generated at the top of the tower enters the condenser, and a part of the condensate flows back into the steam. The ammonia tower is partially sent to the ammonia tank as dilute ammonia water.