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Research and application status of self-cleaning automatic filter process for landfill leachate

             阅读:64365 更新时间:2019-12-11 23:07 Source: Beijing Environmental Protection Equipment Co., Ltd. Hengyuan record reading: 64365 Updated: 2019-12-11 23:07

Research and application status of self-cleaning automatic filter process for landfill leachate

Landfill leachate is already the most important pollution source of groundwater. This paper describes the hazards of landfill leachate, analyzes the characteristics of landfill leachate, outlines the main methods and characteristics of landfill leachate, and reviews the application and research progress of SBR process in landfill leachate treatment in recent years. It was reviewed. The SBR combined process is analyzed and compared with engineering examples, and the advantages and disadvantages of various current treatment processes are pointed out. The meaningful research directions of the SBR process in the leachate treatment are briefly explained.

SBR is a single-tank sequential batch operation with high substrate concentration and strong shock load capacity. Through proper adjustment of the operation mode, it is beneficial to remove nitrogen and phosphorus. These characteristics of the SBR method are suitable for the needs of treating landfill leachate.

1.1 Treatment of landfill leachate using only SBR process

The SBR gradual aeration process was used to treat the fresh leachate from a simulated municipal solid waste landfill. The effluent COD concentration was about 500 mg , L-1, and the BOD5 / COD decreased to about 0.14. The COD removal rate was proportional to the volume load, and the volume load It reached the highest at 5.0 kgCOD , mg-1 , d-1, about 95%. The application of SBR to landfill leachate has achieved good results. The removal rates of COD, BOD, NH3-N, and TN are 86.1%, 97.4%, 94.5%, and 81.3% on average;

1.1.1 Anaerobic SBR Process

At present, there are many studies on using ASBR to treat municipal landfill leachate. Treatment of leachate from a landfill in Harmandali, Turkey. The results show that the new organic landfill leachate can be treated with shorter HRT with shorter HRT without pH adjustment or any pretreatment. The COD removal rate is 64% to 85%, and the removed COD 83% is converted to methane. The body yield was 0.12 VSS / gCOD. When the maximum organic load rate is 2.8kgTOC , mg-1 , d-1, the removal rate of TOC reaches 73.9%. The test also shows that the ASBR process is more adaptable to changes in water volume and water quality than other processes and is suitable for new landfill sites. Treatment of leachate.

1.1.2 Anaerobic SBR-Aerobic SBR Process

In addition to the typical characteristics of SBR, the ASBR process also has the advantages of low temperature influence, wide application range, good sludge sedimentation performance, and high activity.

2.1 Treatment of landfill leachate by combination of physicochemical method and SBR process

At present, the simple use of the SBR process to treat refuse infiltration has largely failed to meet the increasingly stringent sewage discharge standards. The combination of the physical and chemical method + SBR process based on the SBR process, supplemented by the chemical process, is effective for treating leachate. Method is also an inevitable trend of development.

2.2 Blow-off, coagulation sedimentation-SBR combined process

The typical process flow is leachate → pH adjustment → ammonia stripping → SBR reactor → adsorption coagulation → effluent. Ammonia stripping has the characteristics of stable operation and high nitrogen removal efficiency (when special chemical fillers are used, the stripping efficiency can reach more than 90%). Coagulation pretreatment can effectively reduce the content of refractory organic matter and improve the biodegradability of the leachate. After the biochemical treatment of the landfill leachate, the coagulation treatment can ensure that the effluent COD reaches the secondary emission standard.

3.1 Ultrasonic-SBR combined process

The typical process flow is leachate → ultrasonic air flotation → SBR biochemical treatment → chlorination disinfection → effluent. Landfill leachate is a high-concentration, difficult-to-degrade organic wastewater. Ultrasound is suitable for treating this wastewater. At the rated oscillation frequency, some organic matter in the wastewater will be broken and open the chain, becoming small biochemical molecules, and the biodegradability of wastewater will be improved. , Easy to be biochemically processed. Therefore, the ultrasonic method is used as a pretreatment or advanced treatment, and combined with the biological method to treat the landfill leachate in the old landfill is a more optimized choice.

Mingyuan Kaide processed the leachate from a garbage dump. The raw water has a high ammonia nitrogen concentration. After the FBZ process, the removal rates of BOD5, COD, and ammonia nitrogen were 82.1%, 68.9%, and 53.8%, of which the removal rate of ammonia nitrogen was higher than General denitrification process. Ultrasonic treatment of the leachate in the old landfill site is carried out. When the ultrasonic thermal energy is 63GJ , m-2, the BOD5 / COD value can reach 0.014, and the COD removal rate can reach 70%.

3.2 Coagulation and Adsorption-Two-stage SBR Process

The typical process is leachate → coagulation sedimentation → adsorption → SBR1 → SBR2 → effluent, PAFCS is a coagulant, slag is an adsorbent, and SBR2 is supplemented with carbon source water from the effluent of the adsorption tank. Coagulation adsorption has a great effect on removing organic matter, heavy metal ions and suspended solids from landfill leachate.

3.3 Catalytic electrolytic oxidation-SBR combined process

Electrocatalytic oxidation technology uses the direct oxidation and indirect oxidation of electrodes to oxidatively degrade organic or inorganic substances, making them oxidatively decomposed into easily degradable, non-toxic substances. Wang Deyi and others used a combination of catalytic electrolytic oxidation and SBR to conduct experimental research on the treatment of landfill leachate. The removal rates of the effluent indicators were above 90% of COD, NH3-N99%, TN95% and above, and chroma 99%. Less than 0.001 mg , L-1.

3.4 method-SBR combination process

The typical process is leachate → chemical coagulation → electric Fenton → SBR → water. The Fenton method can generate highly oxidizable OH radicals, decompose difficult-to-degrade organic substances, improve the biodegradability of wastewater, and have low cost and easy operation.

4 Other biological treatment processes and SBR combined processes

4.1 Hydrolytic acidification-SBR method-coagulation sedimentation combined process

The typical process flow is leachate → adjustment pond → hydrolytic acidification pond → SBR reaction pond → add CaO to adjust pH → coagulation sedimentation pond → effluent, SBR pond effluent and CaO adjust pH to perform coagulation precipitation treatment. The hydrolysis and acidification process can degrade some organic compounds in the leachate that are difficult to aerobic degradation under the action of hydrolytic bacteria to different degrees. In addition, the hydrolysis and acidification tank can also avoid the excessive production of NH3-N in the anaerobic process and increase the burden of subsequent biochemical treatment. SBR reactors are widely used in the treatment of small and medium amounts of refractory organic matter.

4.2 Blown-anaerobic UBF-A-SBR combined process

The typical process flow is leachate → storage tank → ammonia water stripping anaerobic biological filter → SBR tank → drainage. This treatment process should have the characteristics of good treatment effect and strong impact load resistance. First, ammonia stripping is used to remove high-concentration ammonia nitrogen to meet the subsequent biochemical needs, and then anaerobic and aerobic processes are used to remove organic matter and residual ammonia nitrogen in the water.

4.3 Coagulation air flotation-UASB-hydrolytic acidification-SBR combined process

The typical process flow is leachate → coagulation air flotation → UASB → hydrolytic acidification → SBR tank → adsorption → drainage. The landfill leachate has a high COD concentration. The UASB anaerobic reactor is a highly efficient anaerobic reactor. The UASB process can significantly degrade COD. Jiang Wei et al. Used coagulation air flotation and activated carbon adsorption to pretreat landfill leachate, and then used UASB + hydrolytic acidification + SBR combined process for biochemical treatment. Using SBR process, BOD5 was more degraded by anaerobic treatment, and increased before SBR process Hydrolysis and acidification can adjust the ratio of BOD5 / COD to improve the biodegradability of wastewater. The COD removal rate of SBR reached 78.2%, the total COD removal rate reached 99.1%, and the ammonia nitrogen removal rate reached 96.6%. Yuan Zhiyu and others used ammonia stripping + UASB + SBR process, COD is 5000 ~ 6000mg , L-1, NH3-N is 600 ~ 1400mg , L-1, COD removal rate of effluent is above 80%, and NH3-N removal rate is above 95%. .

4.4UASBF-SBR combined process

The typical process flow is leachate → mediation tank → UASBF → intermediate water tank → SBR tank → coagulation sedimentation tank → external discharge. Upstream anaerobic sludge filter reactor (UASBF) has the advantages of both anaerobic sludge bed and anaerobic filter bed, with strong sludge interception capacity and impact load capacity, and high sludge concentration. Its function is not only to remove organic matter in the leachate, but also to convert difficult-to-degrade organic matter into easily degradable organic matter through hydrolysis and acidification, and improve the removal efficiency of organic matter by the subsequent processing device.

5SBR process example of landfill leachate project

In laboratory tests, there are also many SBR and other processes that jointly treat landfill leachate in the actual project. The landfill leachate effluent treated by the SBR combined process has reached the national secondary leachate discharge standard (GB1688921997). 6SBR new biological nitrogen removal technology in landfill leaching

development trend

6.1 SBR short-range nitrification and denitrification biological nitrogen removal technology

Short-range nitrification and denitrification is a new technology in the current research field of biological denitrification. The key is to control the nitrification in the biochemical denitrification to nitrite type nitrification. It does not go through the traditional NO3-stage during denitrification, which reduces the oxygen demand and The amount of external carbon source required for denitrification greatly reduces operating costs and saves carbon sources. There are many conditions for the treatment of landfill leachate to form short-range nitrification and denitrification, including temperature, pH, free ammonia FA, dissolved oxygen, and sludge age. Higher FA is the main reason for the accumulation of NO2--N, and DO is an important promoting factor. Within a certain range of free ammonia, the mutual conversion between short-range nitrification and global nitrification can be promoted by adjusting the dissolved oxygen. In addition, ALR, pH, alkalinity, and temperature directly or indirectly affect the concentration of free ammonia, thereby affecting the NO2--N accumulation rate.

Sludge concentration is also an important factor to achieve short-range nitrification. Due to the presence of FA gradient in the sludge floc, higher sludge concentration can weaken and weaken the inhibitory effect of FA on it.

6.2 Simultaneous nitrification and denitrification biological nitrogen removal technology

Compared with the traditional biological denitrification process, the simultaneous nitrification and denitrification (SND) process has the advantages of saving reactor volume, shortening the reaction time, and eliminating the need for acid-base neutralization. It is suitable for denitrification of low COD / NH4 + -N landfill leachate. . Using the SND process, by controlling the oxygen supply and regulating the nutritional ratio, the high-concentration ammonia nitrogen of the landfill leachate is simultaneously nitrated and denitrified through the NO2-path to achieve an efficient and economical nitrogen removal effect.

6.3 Ammonia oxidation biological nitrogen removal technology

Anaerobic ammoxidation is the conversion of NH3-N and NOx--N to N2 and other gaseous states by using NH3 as an electron donor and NO2- and NO3- as electron acceptors under anaerobic conditions. Physical process. Compared with the traditional denitrification process, anaerobic ammoxidation has the advantages of no need for oxygen, no additional carbon source, low biological yield, and low sludge volume. SBR reactor's own operating characteristics determine its ability to retain microorganisms, which can effectively reduce sludge loss, so it is conducive to long-term microorganism growth.

6.4 CANON process

The principle of the CANON process is that under the condition that both nitrite and ammonia nitrogen are present, by controlling dissolved oxygen, the autotrophic ANAMMOX bacteria are used to remove ammonia and nitrite at the same time. The product is nitrogen, and a small amount of nitrate is also accompanied. Because the microorganisms involved in the reaction are autotrophic, the CANON process does not require a carbon source. In addition, the CANON process only needs to nitrate 50% of the ammonia nitrogen, and the nitrification step only needs to be controlled to the nitrosation stage, so 50% of alkalinity can be saved. The CANON process is performed under oxygen-limited conditions, so it can save oxygen supply and theoretically save 62.5% of oxygen supply.

7 conclusion

A large number of landfills are currently under construction, and landfill will be the main method for a long time to come. However, sanitary landfill technology is not perfect and needs to be improved to a large extent. Due to the complex variability and uniqueness of landfill leachate water quality, there is currently no all-round leachate treatment technology that can be suitable for all landfills and for the entire operation and supervision period of a landfill. The landfill leachate treatment process and facilities must be adapted to local conditions and time. Specific leachate characteristics are discussed in detail for different landfills. Long-term consideration should be given to the choice of leachate treatment scheme and treatment technology. The successful application of SBR in the treatment of landfill leachate provides new ideas for the treatment of landfill leachate.

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