CN100522851C - Anaerobic-aerobic-film processing technique for urban domestic refuse percolate - Google Patents

Abstract

The present invention is the anaerobic treatment, aerobic treatment and membrane treatment process of domestic garbage percolate, and belongs to the field of sewage treating technology. The combined treating process is completed in four units including a two-stage upwards flowing anaerobic sludge bed, an immobilized microbial biological aeration filter, a coagulating and settling pond and a nanometer filtering membrane. The present invention has the advantages of simultaneous elimination of carbon, nitrogen and other pollutants, high treating effect, high load impact resistance and high stability. The present invention may be also applied in treating other waste water with high ammonia nitrogen content, high organic pollutant concentration and great water quality fluctuation.

Description

Anaerobic-aerobic-membrane treatment process of municipal solid waste leachate

technical field

The invention relates to the field of waste water treatment, in particular to an anaerobic-aerobic-membrane treatment process for municipal solid waste leachate, which is a combination of biological-physicochemical-membrane removal of high-concentration organic matter and ammonia nitrogen in the leachate It is suitable for the treatment of municipal solid waste leachate and other industrial wastewater with high ammonia nitrogen and high organic matter, such as aquaculture wastewater, coking wastewater and sludge anaerobic digestion solution.

Background technique

Leachate is produced in the process of waste landfill decay, mainly from the following three aspects: (1) natural rainfall and runoff in the landfill; (2) the original water content of the waste itself; (3) waste landfill Water produced as a result of anaerobic decomposition by microorganisms. Among them, the precipitation in the landfill is the main part. When the water seeps through the garbage with complex components, it will cause the garbage to undergo reactions such as decomposition, dissolution, and fermentation, so that the leachate contains a large amount of organic pollutants, nitrogen and phosphorus substances, and a wide variety. of heavy metals. The change of landfill leachate water quality is affected by factors such as waste composition, waste moisture content, waste body temperature, landfill time, landfill law, landfill process, rainfall infiltration, etc., especially the impact of rainfall and landfill time. big. Landfill leachate is a kind of high-concentration organic wastewater with large changes in water quality and quantity, serious imbalance of microbial nutrition ratio, high ammonia nitrogen content, lack of phosphorus, heavy odor, high chroma, high toxicity, and difficult to treat. As the time increases, the B/C ratio of leachate decreases, the C/N ratio decreases, and the difficulty of treatment increases.

Scholars at home and abroad have done a lot of research on the harmless treatment of leachate. There are three main types of methods: (1) introducing leachate into nearby urban sewage treatment plants for combined treatment; The huge biological filter bed of the filler is sprayed and recharged; (3) Independent on-site treatment. The actual situation is that general waste landfills are far away from urban sewage treatment plants, and the transportation of leachate will cause a large economic burden. Moreover, due to the unique water quality and changing characteristics of leachate, it must be supplemented when adopting this scheme. With corresponding effective control measures, otherwise it will easily cause impact load on the urban sewage treatment plant, affecting or even destroying the normal operation of the urban sewage treatment plant. For the spraying recharge method, although it is economical and simple, it cannot completely eliminate the leachate, and it will also lead to the continuous accumulation of ammonia nitrogen. Therefore, the current solutions for landfill leachate treatment are mainly independent on-site complete treatment, biological methods, physical and chemical methods, constructed wetland methods, and combined treatment processes of various methods. Studies have shown that the physical and chemical method alone is not only costly, complicated to operate, prone to secondary pollution, and difficult to meet the discharge standards; using anaerobic technology alone, although efficient and energy-saving, the quality of the effluent after anaerobic treatment, especially the concentration of ammonia nitrogen, is far away. If the emission standard is exceeded, aerobic method or physicochemical method must be used in combination for deep denitrification and decarbonization treatment. Although the aerobic method alone can remove organic matter and ammonia nitrogen in the leachate at the same time, due to the limitation of D0 transfer in actual engineering, the leachate with too high concentration of organic matter cannot be treated alone. The area occupied by the artificial wetland method alone is too large. Therefore, combined processes such as physicochemical and biological processes are generally used. At present, the existing leachate treatment process has problems such as high investment and operation costs, complicated process flow, etc., and many treatment devices cannot withstand the impact load of strong water quality and quantity of leachate, the operation is unstable, and the treatment efficiency is low.

Contents of the invention

The purpose of the present invention is to make up for the deficiencies in the prior art, and provide an anaerobic-aerobic-membrane treatment process for leachate of municipal solid waste.

Through an in-depth understanding of the water quality characteristics of municipal solid waste leachate, a comprehensive comparison of landfill leachate treatment processes at home and abroad, and in view of the difficulties in the treatment of landfill leachate, a leachate treatment device and method have been developed, namely two-stage UASB+G-BAF+coagulation Combined process of precipitation + membrane system. This process not only effectively removes organic matter and ammonia nitrogen, but also can achieve a removal rate of more than 85% of total nitrogen. The follow-up membrane system ensures that the effluent meets the first-class discharge standard.

The technical scheme of the present invention is: what adopt is two-stage UASB-G-BAF-coagulation sedimentation-nanofiltration membrane combined process, comprises the steps of following order:

Two-stage UASB anaerobic treatment: Anoxic denitrification and hydrolysis and acidification of organic matter are carried out in the first stage UASB1, which can remove nitrogen oxides, some organic matter and most toxic substances; anaerobic methanogenesis is carried out in the second stage UASB2, Most of the organic matter is removed, and the methane produced can be recycled; the leachate passes through two-stage UASB reactors, so that the COD removal rate reaches 80-90%, and the nitrogen oxide concentration drops below 20mg/L;

G-BAF aerobic treatment: the effluent from the two-stage UASB reactor enters the G-BAF reactor for a thorough nitrification reaction, removes high ammonia nitrogen, and removes a part of total nitrogen and remaining organic matter at the same time, and the effluent returns to the UASB1 reactor. The reflux ratio is based on Depending on the actual water quality, to remove the remaining nitrogen oxides produced by the G-BAF section;

Coagulation and sedimentation treatment: Biodegradable organic matter and high ammonia nitrogen can be completely removed through anaerobic and aerobic biological treatment processes; non-biochemical organic matter and soluble microbial products produced in the biochemical process enter the coagulation sedimentation tank for further treatment Treatment, removal of sulfur and 50-60% of the remaining organic matter, to ensure the quality of water entering the nanofiltration membrane;

Nanofiltration membrane treatment: Nanofiltration membrane filtration is performed on the effluent of coagulation sedimentation, which can remove the remaining organic matter, ammonia nitrogen and various salts, so that the effluent can meet the first-class sewage discharge standard; the resulting concentrated solution is returned to UASB1 for treatment.

The anoxic denitrification is carried out in the first-stage upflow anaerobic sludge bed reactor, so that the alkalinity produced by denitrification will buffer the acidity produced by the acidification and hydrolysis of organic matter in the first-stage anaerobic reactor, and the large Molecular organic matter is converted into small molecular organic matter to remove toxic substances and lay a good foundation for the second-stage anaerobic reactor to produce methane.

The three-phase separator of the two-stage UASB reactor is two or three layers, which is determined according to the actual wastewater quality to avoid the loss of sludge.

The upper part of the two-stage UASB reactor is provided with a gas collection hood to collect the generated methane gas.

The aerobic section adopts immobilized microbial aerated biofilter technology, and the internal filler is a macroporous net-like polyurethane-based carrier, on which microorganisms are immobilized, and the reactor does not need to be backwashed.

In the immobilized microbial aerated biological filter reactor, due to the action of immobilized microorganisms, an anaerobic-facultative-aerobic microenvironment can be formed inside the carrier, and simultaneous nitrification and denitrification reactions occur to remove part of the total nitrogen.

The effluent from the G-BAF reactor is returned to the two-stage anaerobic UASB1 reactor for further removal of residual nitrogen oxides and organic pollutants.

Separately set up a coagulation sedimentation tank, add flocculant and coagulant aid to cause coagulation and sedimentation reaction of pollutants, remove sulfur and 50-60% organic matter in biochemical effluent, to ensure water intake requirements of nanofiltration membrane.

The concentrate produced by the nanofiltration membrane system is returned to UASB1 for processing.

Compared with the prior art, the present invention has the following advantages: it can simultaneously remove pollution such as carbon and nitrogen in the leachate, and at the same time can also decolorize and deodorize, and treat the effluent to meet the first-level discharge standard; the denitrification efficiency is high, and no external organic carbon source is needed; Due to the adoption of immobilized microorganism technology, the biomass in the system is very large, and the biological species are rich, including short bacillus, long bacillus and coccus, etc., and there are a large number of bacterial micelles. At the same time, nitrifying bacteria and denitrifying bacteria with long generation time can effectively Fixed on the carrier, avoiding the loss of bacteria in the traditional method; using nanofiltration technology, compared with ultrafiltration, it has higher filtration efficiency and selective permeability, and the required filtration pressure (0.5-1.0Mpa) is less than that of reverse Osmotic system (1.2-1.8Mpa), the same effect can be achieved by using a booster pump with a lower head, saving energy consumption; the ability to withstand the change of pollutant load in the influent is very strong, and it has the ability to resist the impact of the system. It is a kind of Efficient combined biological reaction system.

The technical principle of the present invention is as follows: first, two-stage UASB is used to remove most of the organic matters and nitrogen oxides through denitrification, hydrolysis acidification and anaerobic methanogenesis, and recover methane at the same time. The high-concentration ammonia nitrogen and residual organic matter in the anaerobic effluent are further degraded in the subsequent G-BAF process to remove high ammonia nitrogen, and at the same time remove part of the total nitrogen and the remaining organic matter, and the effluent returns to the UASB1 reactor (the reflux ratio depends on the actual Depending on the water quality), remove the remaining nitrogen oxides produced by the G-BAF section; biodegradable organic matter and high ammonia nitrogen can be completely removed through anaerobic and aerobic biological treatment processes. Non-biochemical organic matter and soluble microbial products produced in the biochemical process enter the coagulation sedimentation tank for further treatment to ensure the water quality entering the nanofiltration membrane. After passing through the membrane treatment unit, the effluent is better than the first-level discharge standard.

Municipal solid waste leachate is treated by using a two-stage UASB-G-BAF-coagulation sedimentation-nanofiltration membrane combination process. The specific steps are as follows:

The landfill leachate adjusts the pH to about 7 in the adjustment tank, and enters the two-stage UASB to remove most organic matter, nitrogen oxides and toxic substances;

The anaerobic effluent enters the BAF reactor to completely nitrify and remove ammonia nitrogen, and at the same time remove part of the total nitrogen and the remaining biodegradable organic matter;

The aerobic effluent enters the coagulation sedimentation tank to remove SS and about 50% organic matter in the biochemical effluent to ensure the requirements of nanofiltration influent;

The effluent of the coagulation sedimentation tank enters the nanofiltration membrane system for filtration, and the effluent index reaches the first-level discharge standard.

in:

In the adjustment tank, the pH value of the landfill leachate is adjusted to about 7.0. The fresh landfill leachate is generally acidic, and the middle-aged and old landfill leachate is generally alkaline. The regulating agent used is acetic acid or hydrochloric acid.

The UASB1 reactor was started with denitrification sludge plus anaerobic sludge; the UASB2 reactor was started with anaerobic sludge.

The two-stage UASB reactor first uses artificial water distribution after adjusting the pH value to domesticate, and gradually increases the proportion of leachate in the artificial water distribution until the leachate is completely infiltrated. The COD _Cr concentration of domestication sewage is between 2000-10000mg/L; the reactor temperature is 35±2°C. After the anaerobic reactor is started, the hydraulic retention time is 48-72h, the COD volume load can reach 5-20kg/(m ³ ·d), and the removal rate is 80-90%. Among them, the domesticated sewage of UASB1 reactor also contains 500-2000mg/L nitrogen oxides, and after domestication, the concentration of nitrogen oxides in the effluent of UASB1 reactor is less than 20mg/L.

The G-BAF reactor is filled with FPUFS polyurethane-based biological carrier, and at the same time, high-efficiency microorganisms are added to fix them on the surface and inside of the carrier. Due to the action of immobilized microorganisms, an anaerobic-facultative-aerobic microenvironment can be formed inside the carrier. Nitrifying bacteria are fixed on the surface of the carrier, and denitrifying bacteria are fixed inside the carrier, creating an environment for the occurrence of simultaneous nitrification and denitrification reactions. , which is conducive to the removal of total nitrogen. Use UBF anaerobic reactor effluent to domesticate microorganisms; G-BAF reactor temperature is room temperature, residence time is 24-36h, dissolved oxygen (DO) concentration is 2-6mg/L, effluent pH value is 7.6-8.1; COD The volume load can reach 2-10kg/(m ³ ·d), and the removal rate is 65-90%; the volume load of ammonia nitrogen can reach 0.5-2.0kg/(m ³ ·d), and the removal rate is 92-99%; Carbon source, the total nitrogen removal rate of G-BAF can reach about 50%. The effluent from the G-BAF reactor is returned to the two-stage anaerobic UASB1 reactor for further removal of residual nitrogen oxides and organic pollutants.

Biodegradable organic matter and high ammonia nitrogen can be completely removed through anaerobic and aerobic biological treatment processes. Non-biochemical organic matter and soluble microbial products produced in the biochemical process enter the coagulation sedimentation tank for further treatment, adding flocculant and coagulant aid to cause coagulation and precipitation of pollutants, and remove sulfur and about 50% of the remaining Organic matter, to ensure the quality of water entering the nanofiltration membrane.

Finally, nanofiltration membrane filtration is performed on the effluent of coagulation and sedimentation, which can remove the remaining organic matter, ammonia nitrogen and various salts, so that the effluent can meet the first-class standard for sewage discharge. The resulting concentrate is returned to UASB1 for processing.

The invention is a combined process for efficiently treating leachate of municipal domestic garbage, which is not only suitable for the treatment of leachate, but also can be applied to the treatment of any waste water with high organic concentration, high ammonia nitrogen concentration, and large water quality fluctuations.

The process of the embodiment of the present invention is: use fresh landfill leachate and middle-aged and old landfill leachate respectively to enter the adjustment tank, adjust the pH value to about 7.0, and then enter the two-stage UASB reactor for anaerobic degradation of pollutants, mainly to remove organic matter and nitrogen Oxide, the effluent enters the G-BAF reactor to further remove ammonia nitrogen and remaining biochemical organic pollutants in the water, and then enters the nanofiltration membrane system after coagulation and precipitation, and the effluent meets the standard discharge.

Description of drawings

Fig. 1 is a process flow diagram of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the embodiments of Fig. 1 and Fig. 2, but the present invention is not limited to these embodiments.

Example 1:

Using the combined process of the present invention to treat fresh landfill leachate, the concentration of COD _Cr in raw water is 12000-24000mg/L, the concentration of NH ₄ ⁺ -N is 1050-1800mg/L, the concentration of TIN (total inorganic nitrogen) is 1180-1910mg/L, UASB The water temperature of the reactor and G-BAF reactor is controlled at 35±2°C and 28±2°C respectively, the residence time is 72h and 36h respectively, the concentration of COD _Cr in the final effluent is 10-50mg/L, and the concentration of NH ₄ ⁺ -N is 1.0 -12.0mg/L, TN concentration is 10-150mg/L, the COD _Cr and NH ₄ ⁺ -N TN removal rates both reach 99%, and the TN removal rates also reach over 90%.

Example 2:

Using the combined process of the present invention to treat middle-aged and old landfill leachate, the concentration of COD _Cr in the raw water is 3850-6500 mg/L, the concentration of NH ₄ ⁺ -N is 1400-2100 mg/L, and the water temperature of the UASB reactor and the G-BAF reactor are respectively controlled at 35 ±2°C and 28±2°C, the residence time is 60h and 36h respectively, the final effluent COD _Cr concentration is 20-50mg/L, NH ₄ ⁺ -N concentration is 2.5-15.0mg/L, COD _Cr and NH ₄ ⁺ - The removal rate of N can reach more than 98%.

It can be seen from the above examples that the combined process of the present invention has a good treatment effect on the leachate of different landfill time periods, and the final effluent meets the first-class standard for comprehensive sewage discharge (GB8978-1996).

Claims (7)

1. The anaerobic-aerobic-membrane treatment process of municipal solid waste leachate is characterized in that it adopts a two-stage UASB-G-BAF-coagulation sedimentation-nanofiltration membrane combination process, including the following steps: Two-stage UASB anaerobic treatment: Anoxic denitrification and hydrolysis and acidification of organic matter are carried out in the first stage UASB1 to remove nitrogen oxides, some organic matter and most toxic substances; anaerobic methanogenesis reaction is carried out in the second stage UASB2 to remove Most of the organic matter, the methane produced is recycled; the leachate passes through two-stage UASB reactors, so that the COD removal rate reaches 80-90%, and the nitrogen oxide concentration drops below 20mg/L; G-BAF aerobic treatment: the effluent from the two-stage UASB reactor enters the G-BAF reactor for a thorough nitrification reaction, removes high ammonia nitrogen, and removes a part of total nitrogen and remaining organic matter at the same time, and the effluent returns to the UASB1 reactor. The reflux ratio is based on Depending on the actual water quality, to remove the remaining nitrogen oxides produced by the G-BAF section; Coagulation and sedimentation treatment: Biodegradable organic matter and high ammonia nitrogen are completely removed through anaerobic and aerobic biological treatment processes; non-biochemical organic matter and soluble microbial products produced during the biochemical process enter the coagulation sedimentation tank for further treatment , remove sulfur and 50-60% of the remaining organic matter, and ensure the water quality entering the nanofiltration membrane; Nanofiltration membrane treatment: Nanofiltration membrane filtration is performed on the coagulation sediment effluent to remove the remaining organic matter, ammonia nitrogen and various salts, so that the effluent meets the first-class sewage discharge standard; the resulting concentrated solution is returned to UASB1 for treatment. 2. The municipal solid waste leachate anaerobic-aerobic-membrane treatment process according to claim 1 is characterized in that anoxic denitrification is placed in the first-stage upflow anaerobic sludge bed reactor; like this The alkalinity produced by denitrification will buffer the acidity produced by the acidification and hydrolysis of organic matter in the first-stage anaerobic reactor, convert large-molecular organic matter into small-molecular organic matter, remove toxic substances, and generate methane for the second-stage anaerobic reactor. Lay a good foundation. 3. The anaerobic-aerobic-membrane treatment process for municipal solid waste leachate according to claim 1 or 2, characterized in that the three-phase separator of the two-stage UASB reactor is two or three layers, which is based on the actual waste water The water quality is determined to avoid the loss of sludge. 4. The anaerobic-aerobic-membrane treatment process for municipal solid waste leachate according to claim 1 or 2, characterized in that a gas collecting hood is arranged on the upper part of the two-stage UASB reactor to collect the generated methane gas. 5. The anaerobic-aerobic-membrane treatment process for municipal solid waste leachate according to claim 1, characterized in that the aerobic stage treatment part adopts immobilized microbial aerated biological filter technology, and the internal filler is macropore Reticulated polyurethane-based carrier, on which microorganisms are immobilized, the reactor does not require backwashing. 6. The anaerobic-aerobic-membrane treatment process for municipal solid waste leachate according to claim 5, characterized in that in the bioaerated biofilter reactor of the immobilized microorganisms, due to the action of the immobilized microorganisms, the inside of the carrier forms In an anaerobic-facultative-aerobic microenvironment, simultaneous nitrification and denitrification reactions occur to remove part of the total nitrogen. 7. The anaerobic-aerobic-membrane treatment process for municipal solid waste leachate according to claim 1, characterized in that a coagulation sedimentation tank is set up separately, and flocculants and coagulant aids are added to cause the pollutants to produce coagulation and sedimentation reactions , to remove sulfur and 50-60% of organic matter in the biochemical effluent to ensure the water inflow requirements of the nanofiltration membrane.

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