Landfill leachate treatment method and treatment system thereof

Abstract

The invention discloses a landfill leachate treatment method and a treatment system thereof, and relates to the technical field of sewage purification systems. The device comprises an adjusting tank mechanism, an anaerobic-aerobic treatment mechanism, a first air stripping treatment mechanism, a biochemical aeration tank mechanism, a filtering mechanism, a nanofiltration membrane mechanism, a second air stripping treatment mechanism and a reverse osmosis treatment mechanism which are connected in sequence, and the anaerobic-aerobic treatment mechanism comprises an anaerobic tank sub-mechanism and an aerobic tank sub-mechanism which are connected in sequence. The invention mainly solves the problem of how to provide a treatment method and a treatment system which are good in purification effect, low in material and operation cost and small in occupied area for the landfill leachate. The method disclosed by the invention has a relatively good treatment effect on pollutants such as various organic matters, amides, nitrides, phosphorus pollutants, monovalent salts and divalent salts in the landfill leachate, and is suitable for being widely applied to refuse landfills.

Description

Technical Field

[0001] This invention relates to the field of wastewater purification system technology, specifically to a method and system for treating landfill leachate. Background Technology

[0002] Landfill leachate specifically refers to a high-concentration organic or inorganic wastewater that originates from the moisture contained in the waste itself in the landfill, rainwater and snowmelt entering the landfill, and other moisture, and passes through the waste layer and the cover soil layer.

[0003] Because landfills contain a wide variety of waste from diverse sources and undergo various biochemical reactions, the leachate they contain also contains a diverse range of pollutants, such as various organic compounds, ammonium compounds, nitrogen compounds, phosphorus pollutants, monovalent salts, and divalent salts (e.g., sodium chloride). + Mg 2+ Ca 2+ ,Cl - SO4 2- It contains heavy metal ions, etc., and the chemical oxygen demand (COD) value can reach 12000 mg / L, the ammonia nitrogen value can reach 2500 mg / L, and the pH value is 6.0-9.0.

[0004] Traditional wastewater treatment systems mainly employ biodegradation processes, anaerobic-aerobic processes (AO), and reverse osmosis (RO). These processes are effective at purifying one or more types of pollutants. However, landfill leachate contains a wide variety of pollutants, and traditional wastewater treatment systems are not suitable for purifying it.

[0005] In conclusion, how to provide a treatment method and system for landfill leachate that offers excellent purification results, low material and operating costs, and a small footprint has become an urgent problem to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide a method and system for treating landfill leachate, which can provide a treatment method and system with good purification effect, low material and operating costs, and small footprint for landfill leachate.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for treating landfill leachate, the method comprising the following steps:

[0008] S1. Introduce the landfill leachate into the equalization tank for preliminary sedimentation, homogenization, equalization and anaerobic pretreatment.

[0009] S2. The landfill leachate treated by the homogenizing tank enters the anaerobic-aerobic treatment unit, where microorganisms in the anaerobic-aerobic treatment unit remove phosphorus pollutants, ammonium compounds, and nitrogen compounds from the landfill leachate, and degrade organic pollutants in the landfill leachate through the microorganisms in the anaerobic-aerobic treatment unit.

[0010] S3. The landfill leachate treated by the anaerobic-aerobic treatment unit enters the first stripping treatment unit to further remove ammonium compounds and nitrogen compounds from the landfill leachate.

[0011] S4. The landfill leachate treated by the first stripping treatment unit enters the biochemical aeration tank unit, so that the microorganisms in the biochemical aeration tank unit can remove phosphorus pollutants, ammonium compounds and nitrogen compounds in the landfill leachate, and degrade organic pollutants in the landfill leachate by the microorganisms in the biochemical aeration tank unit.

[0012] S5. The landfill leachate treated by the biochemical aeration tank enters the filtration mechanism to filter out solid suspended matter, colloids and oil mist in the landfill leachate.

[0013] S6. The landfill leachate treated by the filtration mechanism enters the nanofiltration membrane mechanism to intercept high-valence salt ions, substances with a molecular weight of 200 to 2000 Daltons in the landfill leachate, and further intercept solid suspended matter, colloids and oil mist in the landfill leachate.

[0014] S7. The landfill leachate treated by the nanofiltration membrane mechanism enters the second stripping treatment mechanism to further remove ammonium compounds and nitrogen compounds from the landfill leachate.

[0015] S8. The landfill leachate treated by the second stripping treatment unit enters the reverse osmosis treatment unit to intercept monovalent salt ions and small molecule organic pollutants in the landfill leachate.

[0016] S9. The produced water from the reverse osmosis treatment unit meets the discharge standards.

[0017] In the above technical solution, the method further includes: in step S4, the sludge produced by the biochemical aeration tank mechanism is reinjected into the source site of the landfill leachate; in step S6, the concentrate produced by the nanofiltration membrane mechanism is reinjected into the source site of the landfill leachate; in step S8, the concentrate produced by the reverse osmosis treatment mechanism is reinjected into the source site of the landfill leachate.

[0018] In the above technical solution, in step S2, the anaerobic-aerobic treatment mechanism includes an anaerobic tank mechanism and an aerobic tank mechanism connected in sequence.

[0019] In the above technical solution, the removal of phosphorus pollutants in landfill leachate by microorganisms in the anaerobic-aerobic treatment mechanism specifically involves: the microorganisms in the anaerobic-aerobic treatment mechanism carrying phosphorus pollutants in the landfill leachate to form sludge; in step S4, the removal of phosphorus pollutants in landfill leachate by microorganisms in the biochemical aeration tank mechanism specifically involves: the microorganisms in the biochemical aeration tank mechanism carrying phosphorus pollutants in the landfill leachate to form sludge.

[0020] In the above technical solution, step S2, the removal of ammonia and nitrogen oxides from the landfill leachate by microorganisms in the anaerobic-aerobic treatment unit specifically involves: the microorganisms in the anaerobic-aerobic treatment unit decomposing organic nitrogen in the landfill leachate into ammonia and nitrogen oxides; the microorganisms in the anaerobic-aerobic treatment unit oxidizing the ammonia and nitrogen oxides in the landfill leachate into nitrite and / or nitrate through nitrification; and the microorganisms in the anaerobic-aerobic treatment unit denitrifying the nitrite and / or nitrate in the landfill leachate through denitrification. In step S4, the microorganisms in the biological aeration tank remove ammonium compounds and nitrogen compounds from the landfill leachate. Specifically, the microorganisms in the biological aeration tank decompose the organic nitrogen in the landfill leachate into ammonium compounds and nitrogen compounds; the microorganisms in the biological aeration tank oxidize the ammonium compounds and nitrogen compounds in the landfill leachate into nitrite and / or nitrate through nitrification; and the microorganisms in the biological aeration tank reduce the nitrite and / or nitrate in the landfill leachate into nitrogen gas through denitrification.

[0021] In the above technical solution, in step S3, before the landfill leachate enters the first stripping treatment unit, a sodium hypochlorite solution is added to the landfill leachate to carry out the following reaction:

[0022] NH4 + +HOCl→NH2Cl+H2O+H + ;

[0023] NH₂Cl + HOCl → NH₂ + H₂O;

[0024] NHCl2 + HOCl → NCl3 + H2O;

[0025] This increases the content of free ammonia in landfill leachate.

[0026] In the above technical solution, the filtration mechanism is specifically: a sand filter mechanism filled with quartz sand, and / or a precision filter mechanism filled with a wire-wound honeycomb filter element / melt-blown filter element.

[0027] In the above technical solution, in step S6, before the landfill leachate enters the filtration mechanism, concentrated sulfuric acid is added to the landfill leachate to adjust the pH value of the landfill leachate to 6.2-6.5.

[0028] A landfill leachate treatment system employs the aforementioned landfill leachate treatment method; it comprises, in sequence, an equalization tank, an anaerobic-aerobic treatment unit, a first stripping treatment unit, a biochemical aeration tank, a filtration unit, a nanofiltration membrane unit, a second stripping treatment unit, and a reverse osmosis treatment unit; the anaerobic-aerobic treatment unit comprises, in sequence, an anaerobic tank and an aerobic tank.

[0029] In the above technical solution, the sludge produced by the biochemical aeration tank, the concentrate produced by the nanofiltration membrane, and the concentrate produced by the reverse osmosis treatment unit can all be reinjected into the source of the landfill leachate.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows: The landfill leachate treatment method and system of the present invention, wherein the landfill leachate is sequentially treated by an equalization tank, an anaerobic-aerobic treatment unit, a first stripping treatment unit, a biological aeration tank, a filtration unit, a nanofiltration membrane unit, a second stripping treatment unit, and a reverse osmosis treatment unit, achieving good purification effect and good economic efficiency. The effluent water quality parameters are: pH 8, color 8, suspended solids 6 mg / L, chemical oxygen demand 10 mg / L, five-day biochemical oxygen demand 3.1 mg / L, ammonia nitrogen 11 mg / L, total phosphorus 0.01 mg / L, total nitrogen 12.1 mg / L, fecal coliforms <20 CFU / L, and arsenic 1.1 × 10⁻⁶ CFU / L. -3 mg / L, mercury is 9.6×10 -4 The concentrations of pollutants in the effluent were: mg / L for lead, 0.02 mg / L for cadmium, 0.001 mg / L for hexavalent chromium, 0.004 mg / L for total chromium, and 0.004 mg / L for total chromium. All parameters of the effluent quality met the requirements of GB16889-2008 "Standard for Pollution Control of Municipal Solid Waste Landfills," and the daily treatment capacity was 150 m³ / L. 3 / d; The landfill leachate treatment method and system of the present invention have good treatment effects on various organic matter, ammonium compounds, nitrogen compounds, phosphorus pollutants, monovalent salts and divalent salts in landfill leachate, and are suitable for widespread application in landfills. Attached Figure Description

[0031] Figure 1 This is a structural view of the landfill leachate treatment system of the present invention.

[0032] The attached diagram is labeled as follows: 1. Equalization tank; 2. Anaerobic-aerobic treatment system; 21. Anaerobic tank; 22. Aerobic tank; 3. First stripping treatment system; 4. Biological aeration tank; 5. Filtration system; 6. Nanofiltration membrane system; 7. Second stripping treatment system; 8. Reverse osmosis treatment system. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] This embodiment provides a method for treating landfill leachate, which can be used to purify landfill leachate and remove pollutants contained in it.

[0035] Please see Figure 1 The landfill leachate treatment method of this embodiment includes the following steps:

[0036] S1. The landfill leachate is introduced into the equalization tank 1 for preliminary sedimentation, homogenization, equalization and anaerobic pretreatment.

[0037] In this step, the landfill leachate can be treated as follows through the equalization tank mechanism 1:

[0038] Preliminary sedimentation: This process involves the initial sedimentation and separation of suspended solids in landfill leachate, providing a load buffer for the landfill leachate treatment system and preventing drastic changes in the system's load.

[0039] Homogenization: Prevents high concentrations of pollutants from directly entering the landfill leachate treatment system, ensuring the leachate water quality is balanced and facilitating the smooth progress of subsequent processes.

[0040] Equal flow: Adjust the amount of leachate to ensure a balanced flow of leachate into the leachate treatment system.

[0041] Anaerobic pretreatment: Because the landfill leachate stays in the equalization tank 1 for a long time, an anaerobic effect is formed, which can degrade some organic pollutants by anaerobic microorganisms.

[0042] S2. The landfill leachate treated by the homogenization tank enters the anaerobic-aerobic treatment unit 2, where microorganisms in the anaerobic-aerobic treatment unit 2 remove phosphorus pollutants, ammonium compounds, and nitrogen compounds from the landfill leachate, and degrade organic pollutants in the landfill leachate through the microorganisms in the anaerobic-aerobic treatment unit 2.

[0043] This step can effectively reduce the chemical oxygen demand (COD), biochemical oxygen demand (BOD), total nitrogen, ammonia nitrogen, and total phosphorus values ​​of landfill leachate.

[0044] S3. The landfill leachate treated by the anaerobic-aerobic treatment unit 2 enters the first stripping treatment unit 3 to further remove ammonium compounds and nitrogen compounds from the landfill leachate.

[0045] Specifically, the first stripping treatment unit 3 is equipment for performing the stripping denitrification process. In this embodiment, the first stripping treatment unit 3 is a stripping tower. The first stripping treatment unit 3 uses a blower to introduce air into the landfill leachate, allowing the air and leachate to come into full contact. This causes the dissolved gases and volatile solutes in the landfill leachate to pass through the gas-liquid interface and transfer to the gas phase, thereby achieving the purpose of removing pollutants (ammonia and nitrogen oxides). During the stripping denitrification process, the air introduced into the landfill leachate simultaneously plays the roles of oxygenation and chemical oxidation, with the reaction formula being NH3 + H2O → NH4+. 4+ +OH - .

[0046] This step can further reduce the total nitrogen and ammonia nitrogen levels in landfill leachate.

[0047] S4. The landfill leachate treated by the first stripping treatment unit 3 enters the biochemical aeration tank unit 4, where microorganisms in the biochemical aeration tank unit 4 remove phosphorus pollutants, ammonium compounds and nitrogen compounds from the landfill leachate, and degrade organic pollutants in the landfill leachate through the microorganisms in the biochemical aeration tank unit 4.

[0048] It should be noted that the biological aeration tank mechanism 4 is equipped with a blower and an aeration pipe connected to the blower. This aeration pipe is evenly distributed within the biological aeration tank mechanism 4 and is used to aerate the biological aeration tank mechanism 4. Its function is as follows:

[0049] (1) Increase the dissolved oxygen in the landfill leachate to provide oxygen for the microorganisms in the biochemical aeration tank 4.

[0050] (2) Increase the air content in the landfill leachate so that bubbles can be formed on the surface of oil pollutants, and the oil pollutants can be floated to the surface of the landfill leachate for separation and removal.

[0051] (3) Increase the oxygen content in the landfill leachate to prevent the landfill leachate from becoming putrid and to create a certain stirring effect on the landfill leachate to prevent solid matter from settling.

[0052] This step can further reduce the chemical oxygen demand (COD), biochemical oxygen demand (BOD), total nitrogen, ammonia nitrogen, and total phosphorus values ​​of landfill leachate.

[0053] S5. The landfill leachate treated by the biochemical aeration tank 4 enters the filtration unit 5 to filter out suspended solids, colloids and oil mist in the landfill leachate.

[0054] In this step, the filtration mechanism 5 is specifically: a sand filter mechanism filled with quartz sand, and / or a precision filter mechanism filled with a wire-wound honeycomb filter element / melt-blown filter element; in this embodiment, the filtration mechanism 5 includes a sand filter mechanism and a precision filter mechanism connected in sequence.

[0055] Among them, the sand filter mechanism integrates coagulation reaction, filtration and continuous cleaning, which simplifies the process of landfill leachate treatment and has the characteristics of small footprint, simple structure and flexible and convenient installation and operation.

[0056] Among them, the precision filter mechanism can efficiently remove oil mist and suspended solids in landfill leachate. For suspended solid particles with a diameter of 0.01μm and above, the removal rate is 100%, and the oil mist concentration in the effluent can be controlled at 0.01ppm / wt.

[0057] This step can effectively reduce the chemical oxygen demand (COD), biochemical oxygen demand (BOD), and suspended solids (SS) values ​​of landfill leachate.

[0058] S6. The landfill leachate treated by the filtration unit 5 enters the nanofiltration membrane unit 6 to retain high-valence salt ions, substances with a molecular weight of 200 to 2000 Daltons, and further retain suspended solids, colloids and oil mist in the landfill leachate.

[0059] Among them, the nanofiltration membrane structure 6 has a certain rejection rate for inorganic salts, and the rejection rate for anions increases in the following order: NO3 － Cl － OH － SO4 2－ CO3 2－ The rejection rates for cations increase in the following order: H + Na + K + Mg 2+ Ca 2+ Cu 2+ .

[0060] This step can effectively reduce the suspended solids (SS) and conductivity of landfill leachate.

[0061] S7. The landfill leachate treated by the nanofiltration membrane unit 6 enters the second stripping treatment unit 7 to further remove ammonium compounds and nitrogen compounds from the landfill leachate.

[0062] Specifically, the second stripping treatment unit 7 is the equipment for performing the stripping denitrification process. In this embodiment, the second stripping treatment unit 7 is a stripping tower. The second stripping treatment unit 7 uses a blower to introduce air into the landfill leachate, allowing the air and leachate to come into full contact. This causes the dissolved gases and volatile solutes in the landfill leachate to pass through the gas-liquid interface and transfer to the gas phase, thereby achieving the purpose of removing pollutants (ammonia and nitrogen oxides). During the stripping denitrification process, the air introduced into the landfill leachate simultaneously plays the roles of oxygenation and chemical oxidation, with the reaction formula being NH3 + H2O → NH4+. 4+ +OH - .

[0063] This step can further reduce the total nitrogen and ammonia nitrogen levels in landfill leachate.

[0064] S8. The landfill leachate treated by the second stripping treatment unit 7 enters the reverse osmosis treatment unit 8 to intercept monovalent salt ions and small molecule organic pollutants in the landfill leachate.

[0065] Reverse osmosis is a process that uses pressure to force the solvent in a solution through a reverse osmosis membrane (or semi-permeable membrane) to separate it. Reverse osmosis membranes can retain most of the ions and SiO2 in landfill leachate.

[0066] This step can further reduce the suspended solids (SS) and conductivity of landfill leachate.

[0067] S9 and the reverse osmosis treatment unit 8 produce water that meets the discharge standards.

[0068] Furthermore, the method also includes: in step S4, the sludge produced by the biochemical aeration tank 4 is reinjected into the source site of the landfill leachate (i.e., the landfill); in step S6, the concentrate produced by the nanofiltration membrane 6 is reinjected into the source site of the landfill leachate (i.e., the landfill); in step S8, the concentrate produced by the reverse osmosis treatment unit 8 is reinjected into the source site of the landfill leachate (i.e., the landfill).

[0069] A landfill is essentially a quasi-aerobic bioreactor using waste as a filler. The surface of the waste contains numerous bacterial flocs that can adsorb and degrade organic matter in the water. The waste decomposition process is a highly complex biological, chemical, and physical process. Some intermediate products form landfill gas and are discharged from the landfill, while others are washed away and dissolved by infiltrated rainwater and discharged through a collection system, thus generating landfill leachate. The reinjection of sludge from the biochemical aeration tank 4, concentrate from the nanofiltration membrane 6, and concentrate from the reverse osmosis treatment unit 8 allows the intermediate products that have already flowed out of the landfill leachate treatment system to return to their biological reaction process and continue participating in the biological reaction. Therefore, the reinjection treatment essentially continues the biological reaction process of the landfill and will not have an adverse impact on the landfill. On the contrary, it effectively saves on the secondary treatment costs and / or transportation costs of sludge from the biochemical aeration tank 4, concentrate from the nanofiltration membrane 6, and concentrate from the reverse osmosis treatment unit 8.

[0070] Specifically, in step S2, the anaerobic-aerobic treatment mechanism 2 includes an anaerobic tank mechanism 21 and an aerobic tank mechanism 22 connected in sequence; in fact, the anaerobic tank mechanism 21 and the aerobic tank mechanism 22 can be either metal tanks or civil engineering tanks.

[0071] Specifically, in step S2, the removal of phosphorus pollutants from landfill leachate by microorganisms in the anaerobic-aerobic treatment unit 2 is achieved by: microorganisms in the anaerobic-aerobic treatment unit 2 carrying phosphorus pollutants from the landfill leachate to form sludge; more specifically, under anoxic conditions (i.e., the anaerobic section constructed by the anaerobic tank unit 21), polyphosphate-accumulating bacteria in the anaerobic-aerobic treatment unit 2 decompose the polyphosphates (Poly-P) stored in their cells, releasing inorganic phosphates into the water, while simultaneously absorbing volatile fatty acids (VFA) from the landfill leachate and synthesizing intracellular stored PHB to provide energy for the subsequent aerobic section. Subsequently, under aerobic conditions (i.e., the aerobic section constructed by the aerobic tank unit 22), polyphosphate-accumulating bacteria utilize the stored PHB for metabolic activities, excessively absorbing phosphates in the water to synthesize ATP and new polyphosphates, with the absorption amount reaching 5-10 times the normal physiological requirements. The polyphosphate-accumulating bacteria carry the phosphates from the landfill leachate to form sludge, thus removing phosphorus pollutants from the landfill leachate (which are discharged with the sludge).

[0072] Similarly, in step S4, the removal of phosphorus pollutants from landfill leachate by microorganisms in the biochemical aeration tank 4 is specifically achieved by the microorganisms in the biochemical aeration tank 4 carrying phosphorus pollutants from the landfill leachate to form sludge. More specifically, under anoxic conditions, polyphosphate-accumulating bacteria in the anaerobic-aerobic treatment unit 2 decompose the polyphosphates (Poly-P) stored in their cells, releasing inorganic phosphates into the water. At the same time, they absorb volatile fatty acids (VFA) from the landfill leachate and synthesize intracellular stored PHB to provide energy for the subsequent aerobic stage. Subsequently, under aerobic conditions, polyphosphate-accumulating bacteria utilize the stored PHB for metabolic activities, excessively absorbing phosphates in the water to synthesize ATP and new polyphosphates. The absorption amount can reach 5-10 times the normal physiological requirements. The polyphosphate-accumulating bacteria carry the phosphates from the landfill leachate to form sludge, thereby removing phosphorus pollutants from the landfill leachate (which are discharged with the sludge).

[0073] Specifically, in step S2, the microorganisms in the anaerobic-aerobic treatment unit 2 remove ammonium compounds and nitrogen compounds from the landfill leachate. Specifically, the microorganisms in the anaerobic-aerobic treatment unit 2 decompose the organic nitrogen in the landfill leachate into ammonium compounds and nitrogen compounds; the microorganisms in the anaerobic-aerobic treatment unit 2 oxidize the ammonium compounds and nitrogen compounds in the landfill leachate into nitrite and / or nitrate through nitrification; and the microorganisms in the anaerobic-aerobic treatment unit 2 reduce the nitrite and / or nitrate in the landfill leachate into nitrogen gas through denitrification.

[0074] It is understood that the nitrification reaction mentioned above occurs in the anaerobic tank 21 of the anaerobic-aerobic treatment unit 2, while the denitrification reaction mentioned above occurs in the aerobic tank 22 of the anaerobic-aerobic treatment unit 2. The aerobic tank uses aeration equipment to supply oxygen. In addition, the water temperature of the anaerobic-aerobic treatment unit 2 should be controlled at 20℃~38℃ (which can be achieved through a cooling device) to improve the activity of microorganisms.

[0075] Similarly, in step S4, the microorganisms in the biochemical aeration tank 4 remove ammonium compounds and nitrogen compounds from the landfill leachate. Specifically, the microorganisms in the biochemical aeration tank 4 decompose the organic nitrogen in the landfill leachate into ammonium compounds and nitrogen compounds; the microorganisms in the biochemical aeration tank 4 oxidize the ammonium compounds and nitrogen compounds in the landfill leachate into nitrite and / or nitrate through nitrification; and the microorganisms in the biochemical aeration tank 4 reduce the nitrite and / or nitrate in the landfill leachate into nitrogen gas through denitrification.

[0076] As can be seen from the above, the biochemical aeration tank 4 is a system in which anaerobic and aerobic reactions occur simultaneously.

[0077] Furthermore, in step S3, before the landfill leachate enters the first stripping treatment unit 3, a sodium hypochlorite solution is added to the landfill leachate to carry out the following reaction:

[0078] NH4 + +HOCl→NH2Cl+H2O+H + ;

[0079] NH₂Cl + HOCl → NH₂ + H₂O;

[0080] NHCl2 + HOCl → NCl3 + H2O;

[0081] This increases the content of free ammonia in landfill leachate.

[0082] As mentioned above, in the stripping process for nitrogen removal, the air introduced into the landfill leachate simultaneously serves to both oxygenate and chemically oxidize the leachate, with the reaction formula being NH3 + H2O → NH4+. 4+ +OH - By adding sodium hypochlorite solution to landfill leachate, the content of free ammonia in the leachate can be increased. Free ammonia is easy to escape from the water. If aeration is added, the ammonia can be further released from the water. Therefore, adding sodium hypochlorite solution to the landfill leachate before it enters the first stripping treatment unit 3 can improve the efficiency and removal rate of the first stripping treatment unit 3 in removing ammonia and nitrogen oxides from the landfill leachate.

[0083] Furthermore, in step S6, before the landfill leachate enters the filtration unit 5, concentrated sulfuric acid is added to the landfill leachate to adjust its pH value to 6.2-6.5. The reverse osmosis membrane of the reverse osmosis treatment unit 8 has strict requirements on the acidity and alkalinity of the raw water, and the pH value should be controlled at 6.2-6.5. Since the landfill leachate is weakly alkaline after treatment by the first stripping treatment unit 3, it is necessary to add concentrated sulfuric acid to the landfill leachate before it enters the filtration unit 5 to adjust its pH value.

[0084] This embodiment also provides a landfill leachate treatment system that applies the above-described landfill leachate treatment method.

[0085] Please see Figure 1 The landfill leachate treatment system of this embodiment includes an equalization tank 1, an anaerobic-aerobic treatment unit 2, a first stripping treatment unit 3, a biochemical aeration tank 4, a filtration unit 5, a nanofiltration membrane unit 6, a second stripping treatment unit 7, and a reverse osmosis treatment unit 8, which are connected in sequence.

[0086] The anaerobic-aerobic treatment unit 2 includes an anaerobic tank unit 21 and an aerobic tank unit 22 connected in sequence.

[0087] Furthermore, the sludge produced by the biochemical aeration tank 4, the concentrate produced by the nanofiltration membrane 6, and the concentrate produced by the reverse osmosis treatment unit 8 can all be reinjected into the source site of the landfill leachate.

[0088] The landfill leachate treatment method and system of this embodiment involves sequentially treating the leachate through an equalization tank 1, an anaerobic-aerobic treatment unit 2, a first stripping treatment unit 3, a biological aeration tank 4, a filtration unit 5, a nanofiltration membrane unit 6, a second stripping treatment unit 7, and a reverse osmosis treatment unit 8. This achieves good purification results and is economically viable. The effluent water quality parameters are: pH 8, color 8, suspended solids 6 mg / L, chemical oxygen demand 10 mg / L, five-day biochemical oxygen demand 3.1 mg / L, ammonia nitrogen 11 mg / L, total phosphorus 0.01 mg / L, total nitrogen 12.1 mg / L, fecal coliforms <20 CFU / L, and arsenic 1.1 × 10⁻⁶ CFU / L. -3 mg / L, mercury is 9.6×10 -4 The concentrations of pollutants in the effluent were: mg / L for lead, 0.02 mg / L for cadmium, 0.001 mg / L for hexavalent chromium, 0.004 mg / L for total chromium, and 0.004 mg / L for total chromium. All parameters of the effluent quality met the requirements of GB16889-2008 "Standard for Pollution Control of Municipal Solid Waste Landfills," and the daily treatment capacity was 150 m³ / L. 3 / d; The landfill leachate treatment method and system of this embodiment have good treatment effects on various organic matter, ammonium compounds, nitrogen compounds, phosphorus pollutants, monovalent salts and divalent salts in landfill leachate, and are suitable for widespread application in landfills.

[0089] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for treating landfill leachate, characterized in that, The method includes the following steps: S1. Introduce the landfill leachate into the equalization tank for preliminary sedimentation, homogenization, equalization and anaerobic pretreatment. S2. The landfill leachate treated by the homogenizing tank enters the anaerobic-aerobic treatment unit, where microorganisms in the anaerobic-aerobic treatment unit remove phosphorus pollutants, ammonium compounds, and nitrogen compounds from the landfill leachate, and degrade organic pollutants in the landfill leachate through the microorganisms in the anaerobic-aerobic treatment unit. S3. The landfill leachate treated by the anaerobic-aerobic treatment unit enters the first stripping treatment unit to further remove ammonium compounds and nitrogen compounds from the landfill leachate. S4. The landfill leachate treated by the first stripping treatment unit enters the biochemical aeration tank unit, so that the microorganisms in the biochemical aeration tank unit can remove phosphorus pollutants, ammonium compounds and nitrogen compounds in the landfill leachate, and degrade organic pollutants in the landfill leachate by the microorganisms in the biochemical aeration tank unit. S5. The landfill leachate treated by the biochemical aeration tank enters the filtration mechanism to filter out solid suspended matter, colloids and oil mist in the landfill leachate. S6. The landfill leachate treated by the filtration mechanism enters the nanofiltration membrane mechanism to intercept high-valence salt ions, substances with a molecular weight of 200 to 2000 Daltons in the landfill leachate, and further intercept solid suspended matter, colloids and oil mist in the landfill leachate. S7. The landfill leachate treated by the nanofiltration membrane mechanism enters the second stripping treatment mechanism to further remove ammonium compounds and nitrogen compounds from the landfill leachate. S8. The landfill leachate treated by the second stripping treatment unit enters the reverse osmosis treatment unit to intercept monovalent salt ions and small molecule organic pollutants in the landfill leachate. S9. The produced water from the reverse osmosis treatment unit meets the discharge standards.

2. The landfill leachate treatment method according to claim 1, characterized in that, The method also includes: In step S4, the sludge produced by the biochemical aeration tank is reinjected into the source of the landfill leachate. In step S6, the concentrate produced by the nanofiltration membrane mechanism is reinjected back to the source of the landfill leachate; In step S8, the concentrated liquid produced by the reverse osmosis treatment unit is reinjected into the source site of the landfill leachate.

3. The landfill leachate treatment method according to claim 1, characterized in that, In step S2, the anaerobic-aerobic treatment mechanism includes an anaerobic tank mechanism and an aerobic tank mechanism connected in sequence.

4. The landfill leachate treatment method according to claim 1, characterized in that, In step S2, phosphorus pollutants in landfill leachate are removed by microorganisms in the anaerobic-aerobic treatment unit, specifically as follows: Microorganisms in the anaerobic-aerobic treatment unit carry phosphorus pollutants from landfill leachate to form sludge; In step S4, phosphorus pollutants in landfill leachate are removed by microorganisms within the biochemical aeration tank, specifically as follows: Microorganisms in the biochemical aeration tank carry phosphorus pollutants from landfill leachate to form sludge.

5. The landfill leachate treatment method according to claim 1 or 4, characterized in that, In step S2, the ammonia and nitrogen oxides in the landfill leachate are removed by microorganisms in the anaerobic-aerobic treatment unit, specifically as follows: The microorganisms in the anaerobic-aerobic treatment unit decompose the organic nitrogen in the landfill leachate into ammonium compounds and nitrogen compounds; The microorganisms in the anaerobic-aerobic treatment unit oxidize the ammonium and nitrogen compounds in the landfill leachate into nitrite and / or nitrate through nitrification, and the microorganisms in the anaerobic-aerobic treatment unit reduce the nitrite and / or nitrate in the landfill leachate into nitrogen gas through denitrification. In step S4, the ammonia and nitrogen oxides in the landfill leachate are removed by microorganisms in the biochemical aeration tank, specifically as follows: The microorganisms in the biochemical aeration tank decompose the organic nitrogen in the landfill leachate into ammonium compounds and nitrogen compounds. The microorganisms in the biochemical aeration tank oxidize ammonium compounds and nitrogen compounds in the landfill leachate into nitrite and / or nitrate through nitrification, and reduce nitrite and / or nitrate in the landfill leachate into nitrogen gas through denitrification.

6. The landfill leachate treatment method according to claim 1, characterized in that, In step S3, before the landfill leachate enters the first stripping treatment unit, a sodium hypochlorite solution is added to the landfill leachate to carry out the following reaction: NH4+HOCl→NH2Cl+H2O+H + ; NH₂Cl + HOCl → NH₂ + H₂O; NHCl2 + HOCl → NCl3 + H2O; This increases the content of free ammonia in landfill leachate.

7. The landfill leachate treatment method according to claim 1, characterized in that, In step S5, the filtration mechanism is specifically: a sand filter mechanism filled with quartz sand, and / or a precision filter mechanism filled with a wire-wound honeycomb filter element / melt-blown filter element.

8. The landfill leachate treatment method according to claim 1 or 7, characterized in that, In step S6, before the landfill leachate enters the filtration mechanism, concentrated sulfuric acid is added to the landfill leachate to adjust the pH value of the landfill leachate to 6.2-6.

5.

9. A landfill leachate treatment system, characterized in that, The landfill leachate treatment method according to any one of claims 1-8 is applied; It includes a regulating tank, an anaerobic-aerobic treatment unit, a first stripping treatment unit, a biological aeration tank, a filtration unit, a nanofiltration membrane unit, a second stripping treatment unit, and a reverse osmosis treatment unit connected in sequence. The anaerobic-aerobic treatment mechanism includes an anaerobic tank and an aerobic tank connected in sequence.

10. The landfill leachate treatment system according to claim 9, characterized in that, The sludge produced by the biochemical aeration tank, the concentrate produced by the nanofiltration membrane, and the concentrate produced by the reverse osmosis treatment unit can all be reinjected into the source of the landfill leachate.

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