Landfill leachate wastewater treatment system

Abstract

The invention relates to a landfill leachate wastewater treatment system, and relates to the field of wastewater treatment. By adopting a process route mainly comprising a solid-liquid separator, a comprehensive wastewater regulating tank, a coagulation reaction tank, a primary sedimentation tank, an anaerobic water distribution tank, a CSTR efficient anaerobic reaction tank, an anaerobic sedimentation tank, two-stage nitrification and denitrification, a secondary sedimentation tank, a Fenton reaction tank, a degassing tank, a coagulation reaction tank and an efficient sedimentation tank, the landfill leachate wastewater is thoroughly biochemically degraded; meanwhile, metal ions in water are removed. Biochemical sludge and physicochemical sludge generated in the process are respectively subjected to anaerobic digestion and filter pressing after sludge concentration and reduction, and generated mud cakes can be directly subjected to landfill treatment in a refuse landfill, so that the wastewater treatment cost of enterprises is reduced to the maximum extent.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, in particular to a garbage leachate wastewater treatment system. Background Art

[0002] Landfill leachate wastewater has a series of significant characteristics, which determine the complexity and necessity of its treatment methods. The following are the main characteristics of landfill leachate wastewater:

[0003] 1. The water quality is complex and harmful

[0004] Landfill leachate contains a variety of toxic and hazardous substances, and there are many types of organic pollutants. Through technical testing, it has been found that there are more than 99 types of organic pollutants, of which 22 have been included in the key control lists of my country and the United States. These pollutants include substances that can directly cause cancer and substances that can induce cancer. Leachate also contains compounds that are difficult to biodegrade, such as non-chlorinated aromatic compounds such as naphthalene and phenanthrene, phosphate esters, phenolic compounds and aniline compounds.

[0005] 2. High Pollutant Concentration

[0006] High COD and BOD5 concentrations: The chemical oxygen demand (COD) and biological oxygen demand (BOD5) in the leachate are extremely high, with COD up to 90,000 mg / L and BOD5 up to 38,000 mg / L. High ammonia nitrogen content: The ammonia nitrogen content in the leachate is also high, generally up to 2,000 mg / L or more, and increases with the extension of landfill time, up to 1,700 mg / L. Ammonia nitrogen exists in the leachate in the form of ammonia nitrogen, accounting for about 40% to 50% of the total nitrogen.

[0007] 3. Large changes in water quality and quantity

[0008] The water quality and quantity of landfill leachate will change with changes in external conditions, such as hydrogeological conditions, rainfall, stacking height and method, landfill scale, landfill technology, landfill time, and changes in the composition of the garbage itself. The randomness of these factors leads to great changes in the water quality and quantity of leachate.

[0009] 4. High metal content

[0010] There are more than ten kinds of metal ions in landfill leachate, among which the concentrations of iron, zinc, lead, calcium and other metal ions are relatively high. For example, the concentration of iron can reach about 2000mg / L, the concentration of zinc can reach about 130mg / L, the concentration of lead can reach 12.3mg / L, and the concentration of calcium can even reach 4300mg / L.

[0011] 5. Nutritional imbalance

[0012] For biochemical treatment, the appropriate ratio of nutrients in sewage is BOD5:N:P=100:5:1. However, the ratio of BOD5 to P in general landfill leachate is mostly greater than 300, which is quite different from the ratio of phosphorus required by microorganisms, resulting in an imbalance in nutrient ratios. In summary, landfill leachate wastewater has the characteristics of complex water quality, high harmfulness, high concentration of pollutants, large changes in water quality and quantity, high metal content and imbalance in nutrient ratios. These characteristics make the treatment of landfill leachate particularly complex and difficult, and professional treatment technology and equipment are required to ensure that it meets discharge standards or is safely reused. In order to protect the local environment, a new leachate with a daily treatment capacity of 300m3 is planned to be built. 3 / dSewage treatment station. Summary of the invention

[0013] In order to solve the problems of the prior art, the present invention provides a garbage leachate wastewater treatment system. The garbage leachate flows by gravity through the drainage channel to the comprehensive wastewater regulating tank for collection, and the wastewater is treated by "comprehensive regulating tank + coagulation reaction sedimentation + anaerobic water distribution tank + CSTR anaerobic process + primary nitrification + primary denitrification + secondary nitrification + secondary denitrification + Fenton advanced oxidation decolorization treatment + clear water tank" before reaching the discharge standard. The process technology route with mature and stable technology, low operating cost and low investment cost ensures stable operation and low operating cost after the wastewater station is built. The biochemical and physicochemical sludge generated in the process is treated by sludge landfill after filtration by the screw stacking machine, which minimizes the amount of reagents used and the amount of sludge generated.

[0014] In order to solve the above technical problems, the present invention is implemented by the following technical solutions: a garbage leachate wastewater treatment system, comprising the following steps:

[0015] Step S1: The garbage leachate flows by gravity to the comprehensive regulating tank for collection and regulation, and a solid-liquid separation device is installed at the water inlet of the regulating tank to intercept the suspended garbage;

[0016] Since the landfill leachate is greatly affected by rainfall, a relatively large regulating tank is needed to collect and regulate it to prevent the landfill leachate from overflowing during the rainy season. The landfill leachate flows to the comprehensive regulating tank by gravity, and a solid-liquid separation device is installed at the water inlet of the regulating tank to intercept the suspended garbage in it.

[0017] Step S2: Pumping the effluent from the comprehensive wastewater regulating tank into the coagulation reaction tank and the primary sedimentation tank for treatment to remove metal ions, suspended solids and toxic substances in the wastewater;

[0018] Step S3: The effluent from the primary sedimentation tank enters the anaerobic water distribution tank for mixing, water quality adjustment, and addition of nutrients;

[0019] Step S4: The effluent from the anaerobic water distribution tank is pumped into the CSTR anaerobic reaction tank to convert organic pollutants into CH4, CO2 and H2O under anaerobic conditions;

[0020] The equipment can separate the hydraulic retention time from the sludge retention time, prolong the sludge age, and maximize the sludge concentration in the reactor. It also keeps the sludge in a fluidized state through its own internal circulation, thereby enhancing the mass transfer effect, and ultimately allowing the sludge, wastewater, and gas to fully contact each other and significantly remove organic matter.

[0021] Step S5: The effluent mixed liquid of the CSTR anaerobic reaction tank enters the anaerobic sedimentation tank to separate the mud and water, and the precipitated sludge flows back to the anaerobic tank;

[0022] Step S6: the effluent from the anaerobic sedimentation tank enters a two-stage nitrification-denitrification denitrification process to remove BOD5, SS and nitrogen;

[0023] Step S7: the effluent from the two-stage nitrification-denitrification tank enters the secondary sedimentation tank to precipitate the biochemical sludge, part of which is returned to supplement the bacteria, and the remaining sludge is discharged into the sludge treatment system to maintain the stable operation of the system;

[0024] Step S8: The supernatant in the secondary sedimentation tank enters the decolorization treatment tank for decolorization treatment, and the decolorization treatment tank includes a Fenton reaction tank, a degassing tank, a coagulation reaction tank, and a high-efficiency sedimentation tank connected in sequence;

[0025] Step S9: The physicochemical sludge precipitated in the primary sedimentation tank and the high-efficiency sedimentation tank enters the physicochemical sludge thickening tank, and the remaining biochemical sludge in the secondary sedimentation tank enters the biochemical sludge thickening tank. The physicochemical sludge and biochemical sludge are respectively filtered and reduced in volume and then landfilled. The clear liquid in the thickening tank and the filtrate are returned to the biochemical system for further treatment.

[0026] In a specific embodiment, in step S1, the solid-liquid separation device is an artificial grid; the comprehensive wastewater regulating tank is constructed by using on-site pit digging + HDPE impermeable membrane technology, and is equipped with an aeration and stirring system;

[0027] The solid-liquid separation device is an artificial grid; preferably, the grid spacing is 16-32mm. The comprehensive wastewater regulating tank is constructed by on-site pit digging + HDPE impermeable membrane technology, and the retention time is 8-10 days. A matching aeration and stirring system. Preferably, the aeration and stirring system strength is 2-4m3 / (m2·h).

[0028] In a specific embodiment, in step S2, the coagulation reaction tank is divided into three compartments, and the pH is controlled within the range of 6.5-7.5 by adding alkali, and PAC and PAM are added to perform coagulation reaction to remove SS and some organic pollution;

[0029] The reaction tank is divided into three compartments. The reaction method is to add alkali to control the pH in the range of 6.5-7.5, and add PAC and PAM. PAC, through purification mechanisms such as electrical neutralization, adsorption bridging, net capture and co-precipitation, causes colloids, particulate matter, calcium precipitates, etc. in the wastewater to undergo coagulation reaction, causing the pollutants to settle as sludge. The mud and water are separated in the subsequent primary sedimentation tank, so that SS and some organic pollution are removed.

[0030] Preferably, the residence time of a single cell in the reaction tank is 60-90 minutes. The stirring method of the reaction tank is paddle-type mechanical stirring, and the power is 120-160 (W / m 3 The diameter of the agitator blade is 0.5D (D is the equivalent diameter of a single-cell reaction cell).

[0031] Specifically, the primary sedimentation tank is a radial flow sedimentation tank with central water inlet and peripheral water outlet, and the scraper adopts a central transmission scraper. Preferably, the surface load of the primary sedimentation tank is 0.3-0.8m3 / (m2·h), the torque of the scraper is 1-3KN·m, and the linear speed of the scraper is

[0032] 2-3m / MIN. PAC agent Al2O3 content ≥26%, PAM agent is anionic (molecular weight 12-18 million). The addition amount of PAC is 0.35-0.45kg / m3 wastewater, and the addition amount of PAM is 0.005-0.01kg / m3 wastewater.

[0033] In a specific embodiment, in step S3, the anaerobic water distribution tank is provided with a perforated stirring device;

[0034] The retention time of the anaerobic water distribution tank is 16-24 hours, and a perforated pipe agitator is provided in the tank. Preferably, the stirring intensity of the perforated pipe agitator is 2-4 m3 / (m2·h).

[0035] In a specific embodiment, in step S4, a submersible flow propeller is provided in the CSTR anaerobic reaction tank to achieve even mixing and internal circulation of wastewater and sludge;

[0036] The CSTR anaerobic reaction tank is equipped with a submersible flow propeller as a power source to fully and evenly mix the wastewater and sludge, realize the internal circulation of the mixed liquid, buffer the impact of the bottom water on the sludge, and at the same time increase the hydraulic load of the reactor, ensuring the full mixing of mud and water, so that the wastewater can obtain a stable treatment effect.

[0037] Specifically: The CSTR anaerobic reaction tank is equipped with an online thermometer, a pH meter and an ORP meter to control the pH at 6.8-7.5 and the ORP between -500mv and -300mv.

[0038] Preferably, the CSTR anaerobic reaction time is 8-12 days, and the anaerobic method is 33-35°C mesophilic anaerobic.

[0039] Preferably, the submersible flow force is 3-6 (W / m 3 Pool body), the water flow velocity in the effective working area of ​​water flow mixing is maintained at ≥0.3m / s.

[0040] In a specific embodiment, in step S5, the anaerobic sedimentation tank is a radial flow sedimentation tank with central water inlet and peripheral water outlet, and the scraper adopts a central transmission scraper; the precipitated sludge is returned to the anaerobic water distribution tank in addition to being returned to the CSTR anaerobic reaction tank;

[0041] The sludge precipitated in the anaerobic sedimentation tank does not need to be discharged externally, and all of it flows back into the system.

[0042] Preferably, the sludge return ratio of the anaerobic sedimentation tank is 100-200%.

[0043] Specifically, the microbial sludge in the anaerobic sedimentation tank is not only returned to the CSTR anaerobic reaction tank to replenish the lost bacteria, but also returned to the anaerobic water distribution tank at a ratio of 11:1. The anaerobic water distribution tank becomes a pre-reaction zone for adsorbing and buffering organic matter and toxic and harmful substances in the incoming water, and can consume dissolved oxygen in the incoming water to ensure a stable anaerobic environment for the subsequent CSTR reaction tank.

[0044] Specifically, the anaerobic sedimentation tank is a radial flow sedimentation tank with central water inlet and peripheral water outlet, and the scraper adopts a central transmission scraper. Preferably, the surface load of the anaerobic sedimentation tank is 0.3-0.8m3 / (m2·h), the scraper torque is 2-3KN·m, and the scraper linear speed is 2-3m / MIN.

[0045] In a specific embodiment, in step S6, the two-stage nitrification-denitrification denitrification process is an inverted A / O process, and a submersible agitator is provided in the anoxic zone to maintain a mixed state;

[0046] The two-stage nitrification-denitrification denitrification process is an inverted A / O process, with the first-stage denitrification tank, the first-stage nitrification tank, the second-stage denitrification tank, and the second-stage nitrification tank operating alternately. The aerobic nitrification zone converts ammonia nitrogen into nitrate nitrogen and nitrite nitrogen; the anoxic zone removes nitrate nitrogen from the mixed liquor to control COD / TN ≥ 4. The return sludge first enters the anoxic zone of the biochemical pool, and uses the carbon source organic matter in the influent to carry out biological denitrification to remove nitrate nitrogen in the return sludge. After denitrification, it enters the aerobic zone to complete the degradation of organic matter and nitrification of nitrogen-containing substances.

[0047] Specifically, in step S6, each pool is equipped with a pH meter and a thermometer, and the temperature of each biological reaction pool is maintained at 24-30° C. The pH of the denitrification pool is controlled at 7.5-7.8, and the pH of the nitrification pool is controlled at 7.3-7.5.

[0048] Specifically, in step S6, the nitrification zone is provided with a dissolved oxygen meter and a membrane aerator to control the dissolved oxygen to 3-5 mg / L. The denitrification zone is provided with an ORP meter to control the ORP to be ≤-200 mv.

[0049] Specifically, in step S6, a submersible agitator is provided in each anoxic denitrification zone to maintain the sewage, sludge and mixed liquid in the anoxic zone in a completely mixed state without precipitation, and to effectively prevent short-circuiting.

[0050] Specifically, the nitrification zone is equipped with a mixed liquid reflux pump to return the mixed liquid from the nitrification zone to the denitrification zone, and the reflux ratio is 400-500%.

[0051] Specifically, the retention time of the primary denitrification tank is 30-32 hours, and the retention time of the primary nitrification tank is 7-9 days; the retention time of the secondary denitrification tank is 3-4 days, and the retention time of the secondary nitrification tank is 5-6 days.

[0052] In a specific implementation, in step S7, the secondary sedimentation tank is a radial flow sedimentation tank with central water inlet and peripheral water outlet, and the scraper is a central transmission scraper;

[0053] The secondary sedimentation tank is a radial flow sedimentation tank with central water inlet and peripheral water outlet, and the scraper adopts a central transmission scraper. Preferably, the surface load of the secondary sedimentation tank is 0.3-0.8m3 / (m2·h), the torque of the scraper is 2-3KN·m, and the linear speed of the scraper is 2-3m / MIN.

[0054] Preferably, the sludge from the secondary sedimentation tank is returned to the primary denitrification tank and the secondary denitrification tank, and the total return ratio is 100-200%, wherein the ratio of the sludge returned to the primary denitrification tank and the secondary denitrification tank is 2-3 / 1.

[0055] In a specific embodiment, in step S8, the Fenton reaction tank adjusts the pH to 3-4, and uses H2O2 and Fe2+ to treat the refractory organic matter; the wastewater after decolorization is separated by coagulation reaction and sedimentation in an efficient sedimentation tank;

[0056] The decolorization treatment tank includes a Fenton reaction tank, a degassing tank, a coagulation reaction tank and a high-efficiency sedimentation tank which are connected in sequence.

[0057] Specifically, the reaction mode of the Fenton reaction tank is: add dilute sulfuric acid, adjust the water pH to acidic 3-4, and use Fenton reagent in which H2O2 is combined with Fe2+ to treat the refractory organic substances in the organic wastewater, especially for the chromogenic groups and substances with poor biochemical properties. The specific principle is that H2O2 decomposes to produce hydroxyl (OH-) under the catalytic action of Fe2+, and its oxidation potential reaches 2.8V. It is the strongest inorganic oxidant except elemental fluorine. It oxidizes and decomposes organic matter into small molecules through pathways such as electron transfer. At the same time, Fe2+ is oxidized to Fe3+ to produce coagulation precipitation, removing a large amount of organic matter. Preferably, the Fenton reaction time is 6-12 hours.

[0058] Specifically, the Fenton reaction uses H2O2 (27%) with a dosage of 0.72-1.44 L / m 3 For sewage, the Fenton reaction uses 7-hydrated ferrous sulfate (prepared into a 20% solution), and the solid dosage of 7-hydrated ferrous sulfate is 1.2-2.4 kg / m 3 Sewage.

[0059] Specifically, after the Fenton reaction is complete, the wastewater enters the degassing tank to remove the remaining hydrogen peroxide. The degassing method is aeration, and the degassing time is 20 hours.

[0060] Specifically, the coagulation reaction tank is divided into two compartments. After adding NaOH to adjust the pH value to 7-7.5, anionic PAM (molecular weight 12 million-18 million) is added to flocculate some organic matter, colloids, suspended matter, etc. that are difficult to dissolve in water to form larger alum flakes. Preferably, the PAM dosage is 0.005-0.01 kg / m3 of wastewater.

[0061] Preferably, the residence time of a single cell in the coagulation reaction tank is 90-120 minutes. The stirring method of the reaction tank is paddle-type mechanical stirring, and the power is 60-90 (W / m 3 The diameter of the agitator blade is 0.5D (D is the equivalent diameter of a single-cell reaction cell).

[0062] Specifically, the high-efficiency sedimentation tank is a radial flow sedimentation tank with central water inlet and peripheral water outlet, and the scraper adopts a central transmission scraper. Preferably, the surface load of the high-efficiency sedimentation tank is 0.3-0.8m3 / (m2·h), the torque of the scraper is 1-2KN·m, and the linear speed of the scraper is 2-3m / MIN.

[0063] Specifically, the high-efficiency sedimentation tank is equipped with inclined tube fillers to precipitate and separate the alum flowers in the effluent from the coagulation reaction tank. The supernatant enters the clear water tank for short-term storage before being discharged.

[0064] In a specific embodiment, in step S9, the filtration method of the physicochemical sludge and the biochemical sludge is a stacked screw filter press;

[0065] The filtration methods for physicochemical sludge and biochemical sludge are both screw filter press. No chemical conditioning is required before filtration for physicochemical sludge, but 0.01kg-0.05kg of cationic PAM / m 3 The sludge is conditioned and then filtered. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 It is a schematic diagram of a process flow of a garbage leachate wastewater treatment system in an embodiment of the present invention. DETAILED DESCRIPTION

[0067] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0068] Example 1, for a 300m 3 / dLeachate wastewater treatment system, comprehensive wastewater quality and quantity table (water quality is sampling test analysis data).

[0069]

[0070] The quality of discharged wastewater can meet local emission requirements.

[0071]

[0072]

[0073] Specific implementation steps:

[0074] Step S1: Since the landfill leachate is greatly affected by rainfall, a relatively large regulating tank is required for collection and regulation to prevent the landfill leachate from overflowing during the rainy season. The landfill leachate flows to the comprehensive regulating tank by gravity, and a solid-liquid separation device is installed at the water inlet of the regulating tank to intercept the suspended garbage therein.

[0075] Step S2: The effluent from the comprehensive wastewater regulating tank is pumped into the coagulation reaction tank and the primary sedimentation tank for treatment to remove metal ions, suspended solids, toxic substances, etc. in the wastewater.

[0076] Step S3: The effluent from the primary sedimentation tank enters the anaerobic water distribution tank: the wastewater is mixed and adjusted, and nutrients are added.

[0077] Step S4: The effluent from the anaerobic water distribution tank is pumped into the CSTR anaerobic reaction tank. With the help of microorganisms, the organic pollutants are converted into CH4, CO2 and H2O under anaerobic conditions. The equipment can separate the hydraulic retention time from the sludge retention time, extend the sludge age, and maximize the sludge concentration in the reactor. The sludge is fluidized through its own internal circulation, which enhances the mass transfer effect, and ultimately allows the sludge, wastewater and gas to fully contact each other and significantly remove organic matter.

[0078] Step S5: The effluent mixed liquid from the CSTR anaerobic reaction tank enters the anaerobic sedimentation tank to achieve mud and water separation, and the precipitated sludge is returned to the anaerobic tank.

[0079] Step S6: The effluent from the anaerobic sedimentation tank enters a two-stage nitrification-denitrification denitrification process, and BOD5, SS and nitrogen in various forms will be removed together.

[0080] Step S7: The effluent from the two-stage nitrification-denitrification tank enters the secondary sedimentation tank to precipitate the biochemical sludge, part of which is refluxed to supplement the bacteria required for biochemical treatment, and the remaining sludge is discharged into the sludge treatment system to maintain the stable operation of the system.

[0081] Step S8: The supernatant in the secondary sedimentation tank is yellow-brown and has a high chroma. The effluent enters the decolorization treatment tank for decolorization. After decolorization, the wastewater meets the discharge standards.

[0082] The decolorization treatment tank includes a Fenton reaction tank, a degassing tank, a coagulation reaction tank, and a high-efficiency sedimentation tank which are connected in sequence.

[0083] Step S9: The physicochemical sludge precipitated in the primary sedimentation tank and the high-efficiency sedimentation tank enters the physicochemical sludge thickening tank, and the remaining biochemical sludge in the secondary sedimentation tank enters the biochemical sludge thickening tank. The physicochemical sludge and biochemical sludge enter the filter press for reduction and then landfill. The clear liquid from the thickening tank and the filtrate return to the biochemical system for further treatment.

[0084] In step S1, the solid-liquid separation device is an artificial grid with a grid spacing of 20 mm. The comprehensive wastewater regulating tank is constructed by on-site pit digging + HDPE impermeable membrane technology, and the residence time is 8 days. A matching aeration and stirring system is provided. Preferably, the aeration and stirring system has an intensity of 2m3 / (m2·h).

[0085] In step S2, the reaction tank is divided into three compartments, and the reaction method is to add alkali to control the pH in the range of 6.5-7.5, and add PAC and PAM. PAC, through purification mechanisms such as electrical neutralization, adsorption bridging, net capture and co-precipitation, causes colloids, particulate matter, calcium precipitates, etc. in the wastewater to undergo coagulation reaction, so that the pollutants are settled as sludge, and the mud and water are separated in the subsequent primary sedimentation tank, so that SS and some organic pollution are removed.

[0086] The single cell residence time of the reaction tank is 72 minutes. The stirring method of the reaction tank is paddle-type mechanical stirring, and the power is 137.5 (W / m 3 The diameter of the agitator blade is 0.5D (D is the equivalent diameter of a single-cell reaction cell).

[0087] The primary sedimentation tank is a radial flow sedimentation tank with central water inlet and peripheral water outlet. The scraper adopts central transmission.

[0088] Scraper. Preferably, the surface load of the primary sedimentation tank is 0.35m3 / (m2·h), the torque of the scraper is 2KN·m, and the linear speed of the scraper is 2-3m / MIN.

[0089] The Al2O3 content of PAC agent is ≥26%, and PAM agent is anion (molecular weight 15 million). The addition amount of PAC is 0.37kg / m3 wastewater, and the addition amount of PAM is 0.0065kg / m3 wastewater.

[0090] In step S3, the retention time of the anaerobic water distribution tank is 20 hours, and a perforated pipe agitator is provided in the tank. Preferably, the stirring intensity of the perforated pipe agitator is 2m3 / (m2·h).

[0091] In step S4, a submersible flow propeller is provided in the CSTR anaerobic reaction tank as a power source to fully and evenly stir and mix the wastewater and sludge, thereby realizing the internal circulation of the mixed liquid, buffering the impact of the bottom water on the sludge, and at the same time increasing the hydraulic load of the reactor, ensuring the full mixing of mud and water, so that the wastewater can obtain a stable treatment effect.

[0092] The CSTR anaerobic reaction tank is equipped with an online thermometer, pH meter and ORP meter to control the pH at 6.8-7.5 and the ORP between -500mv and -300mv.

[0093] The CSTR anaerobic reaction time is 8.6 days, and the anaerobic method is 33-35℃ medium temperature anaerobic. The submersible flow force is 3.07 (W / m 3 Pool body), the water flow velocity in the effective working area of ​​water flow mixing is maintained at ≥0.3m / s.

[0094] In step S5, the sludge precipitated in the anaerobic sedimentation tank does not need to be discharged externally, but all flows back into the system.

[0095] The sludge return ratio of the anaerobic sedimentation tank is 160%.

[0096] In addition to returning to the CSTR anaerobic reaction tank to replenish lost bacteria, the microbial sludge in the anaerobic sedimentation tank also returns to the anaerobic water distribution tank at a ratio of 11:1. The anaerobic water distribution tank becomes a pre-reaction zone for adsorbing and buffering organic matter and toxic and harmful substances in the incoming water, and can consume dissolved oxygen in the incoming water to ensure a stable anaerobic environment for the subsequent CSTR reaction tank.

[0097] The anaerobic sedimentation tank is a radial flow sedimentation tank with central water inlet and peripheral water outlet, and the scraper adopts a central transmission scraper. Preferably, the surface load of the anaerobic sedimentation tank is 0.35m3 / (m2·h), the torque of the scraper is 3KN·m, and the linear speed of the scraper is 2-3m / MIN.

[0098] In step S6, the two-stage nitrification-denitrification denitrification process is an inverted A / O process, and the primary denitrification tank-primary nitrification tank-secondary denitrification tank-secondary nitrification tank are operated alternately. The aerobic nitrification zone converts ammonia nitrogen into nitrate nitrogen and nitrite nitrogen; the anoxic zone removes nitrate nitrogen from the mixed liquid, and controls COD / TN ≥ 4. The return sludge first enters the anoxic zone of the biochemical pool, and uses the carbon source organic matter in the influent to carry out biological denitrification to remove nitrate nitrogen in the return sludge. After denitrification, it enters the aerobic zone to complete the degradation of organic matter and nitrification of nitrogen-containing substances.

[0099] In step S6, each pool is equipped with a pH meter and a thermometer, and the temperature of each biological reaction pool is maintained at 24-30° C. The pH of the denitrification pool is controlled at 7.5-7.8, and the pH of the nitrification pool is controlled at 7.3-7.5.

[0100] In step S6, the nitrification zone is equipped with a dissolved oxygen meter and a membrane aerator to control the dissolved oxygen to 3-5 mg / L. The denitrification zone is equipped with an ORP meter to control the ORP to ≤-200 mv.

[0101] In step S6, a submersible agitator is provided in each anoxic denitrification zone to maintain the sewage, sludge and mixed liquid in the anoxic zone in a completely mixed state without precipitation, and to effectively prevent short-circuiting.

[0102] The nitrification zone is equipped with a mixed liquid reflux pump to return the mixed liquid from the nitrification zone to the denitrification zone, with a reflux ratio of 500%.

[0103] The retention time of the primary denitrification tank is 31.2 hours, and that of the primary nitrification tank is 8 days; the retention time of the secondary denitrification tank is 3.3 days, and that of the secondary nitrification tank is 5 days.

[0104] In step S7, the secondary sedimentation tank is a radial flow sedimentation tank with central water inlet and peripheral water outlet, and the scraper adopts a central transmission scraper. The surface load of the secondary sedimentation tank is 0.35m3 / (m2·h), the torque of the scraper is 2KN·m, and the linear speed of the scraper is 2-3m / MIN.

[0105] The sludge from the secondary sedimentation tank is returned to the primary denitrification tank and the secondary denitrification tank, with a total return ratio of 160%, of which the ratio of sludge returned to the primary denitrification tank and the secondary denitrification tank is 3 / 1.

[0106] In step S8, the decolorization treatment tank includes a Fenton reaction tank, a degassing tank, a coagulation reaction tank, and a high-efficiency sedimentation tank connected in sequence.

[0107] The reaction mode of the Fenton reaction tank is: add dilute sulfuric acid, adjust the water pH to acidic 3-4, and use Fenton reagent in which H2O2 is combined with Fe2+ to treat the refractory organic substances in the organic wastewater, especially for the chromogenic groups and substances with poor biochemical properties. The specific principle is that H2O2 decomposes to produce hydroxyl (OH-) under the catalytic action of Fe2+, and its oxidation potential reaches 2.8V. It is the strongest inorganic oxidant except elemental fluorine. It oxidizes and decomposes organic matter into small molecules through pathways such as electron transfer. At the same time, Fe2+ is oxidized to Fe3+ to produce coagulation precipitation, removing a large amount of organic matter. Preferably, the Fenton reaction time is 6.5 hours.

[0108] The Fenton reaction uses H2O2 (27%) with a dosage of 0.72 L / m 3 Sewage, Fenton reaction uses 7-hydrated ferrous sulfate (prepared into 20% solution), and the solid dosage of 7-hydrated ferrous sulfate is 1.2kg / m 3 Sewage.

[0109] After the Fenton reaction is complete, the wastewater enters the degassing tank to remove the remaining hydrogen peroxide. The degassing method is aeration, and the degassing time is 20 hours.

[0110] The coagulation reaction tank is divided into two compartments. After adding NaOH to adjust the pH value to 7-7.5, anionic PAM (molecular weight 15 million) is added to flocculate some organic matter, colloids, suspended matter, etc. that are difficult to dissolve in water to form larger alum flakes. The PAM dosage is 0.0065kg / m3 of wastewater.

[0111] The residence time of a single cell in the coagulation reaction tank is 108 minutes. The stirring method of the reaction tank is paddle-type mechanical stirring, with a power of 77 (W / m 3 The diameter of the agitator blade is 0.5D (D is the equivalent diameter of a single-cell reaction cell).

[0112] The high-efficiency sedimentation tank is a radial flow sedimentation tank with central water inlet and peripheral water outlet, and the scraper adopts a central transmission scraper. Preferably, the surface load of the high-efficiency sedimentation tank is 0.35m3 / (m2·h), the torque of the scraper is 2KN·m, and the linear speed of the scraper is 2-3m / MIN.

[0113] The high-efficiency sedimentation tank is equipped with inclined tube fillers to precipitate and separate the alum flowers in the effluent from the coagulation reaction tank. The supernatant enters the clear water tank for short-term storage before being discharged.

[0114] In step S9, both the physicochemical sludge and the biochemical sludge are filtered by screw filter press. No chemical conditioning is required before filtration of the physicochemical sludge. 0.04 kg cationic PAM / m 3 The sludge is conditioned and then filtered.

[0115] Attached (removal rate table):

[0116]

[0117]

[0118] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A landfill leachate wastewater treatment system, characterized in that: The following steps are involved: Step S1: The garbage leachate flows by gravity to the comprehensive regulating tank for collection and regulation, and a solid-liquid separation device is installed at the water inlet of the regulating tank to intercept the suspended garbage; Step S2: Pumping the effluent from the comprehensive wastewater regulating tank into the coagulation reaction tank and the primary sedimentation tank for treatment to remove metal ions, suspended solids and toxic substances in the wastewater; Step S3: The effluent from the primary sedimentation tank enters the anaerobic water distribution tank for mixing, water quality adjustment, and addition of nutrients; Step S4: The effluent from the anaerobic water distribution tank is pumped into the CSTR anaerobic reaction tank to convert organic pollutants into CH4, CO2 and H2O under anaerobic conditions; Step S5: The effluent mixed liquid of the CSTR anaerobic reaction tank enters the anaerobic sedimentation tank to separate the mud and water, and the precipitated sludge flows back to the anaerobic tank; Step S6: the effluent from the anaerobic sedimentation tank enters a two-stage nitrification-denitrification denitrification process to remove BOD5, SS and nitrogen; Step S7: the effluent from the two-stage nitrification-denitrification tank enters the secondary sedimentation tank to precipitate the biochemical sludge, part of which is returned to supplement the bacteria, and the remaining sludge is discharged into the sludge treatment system; Step S8: The supernatant in the secondary sedimentation tank enters the decolorization treatment tank for decolorization treatment, and the decolorization treatment tank includes a Fenton reaction tank, a degassing tank, a coagulation reaction tank, and a high-efficiency sedimentation tank connected in sequence; Step S9: The physicochemical sludge precipitated in the primary sedimentation tank and the high-efficiency sedimentation tank enters the physicochemical sludge thickening tank, and the remaining biochemical sludge in the secondary sedimentation tank enters the biochemical sludge thickening tank. The physicochemical sludge and biochemical sludge are respectively filtered and reduced in volume and then landfilled. The clear liquid in the thickening tank and the filtrate are returned to the biochemical system for further treatment.

2. A landfill leachate wastewater treatment system according to claim 1, characterized in that: In the step S1, the solid-liquid separation device is an artificial grid; the comprehensive wastewater regulating tank is constructed by using on-site pit digging + HDPE anti-seepage membrane technology, and is equipped with an aeration and stirring system.

3. A landfill leachate wastewater treatment system according to claim 1, characterized in that: In step S2, the coagulation reaction tank is divided into three compartments, and the pH is controlled within the range of 6.5-7.5 by adding alkali, and PAC and PAM are added to perform coagulation reaction to remove SS and some organic pollution.

4. A landfill leachate wastewater treatment system according to claim 1, characterized in that: In step S3, the anaerobic water distribution tank is provided with a perforated stirring device.

5. The landfill leachate wastewater treatment system according to claim 1, characterized in that: In step S4, a submersible flow propeller is provided in the CSTR anaerobic reaction tank to achieve even mixing and internal circulation of wastewater and sludge.

6. A landfill leachate wastewater treatment system according to claim 1, characterized in that: In step S5, the anaerobic sedimentation tank is a radial flow sedimentation tank with central water inlet and peripheral water outlet, and the scraper adopts a central transmission scraper; the precipitated sludge is returned to the CSTR anaerobic reaction tank and also to the anaerobic water distribution tank.

7. The landfill leachate wastewater treatment system according to claim 1, characterized in that: In step S6, the two-stage nitrification-denitrification denitrification process is an inverted A / O process, and a submersible agitator is arranged in the anoxic zone to maintain a mixed state.

8. The landfill leachate wastewater treatment system according to claim 1, characterized in that: In step S7, the secondary sedimentation tank is a radial flow sedimentation tank with central water inlet and peripheral water outlet, and the sludge scraper adopts a central transmission sludge scraper.

9. The landfill leachate wastewater treatment system according to claim 1, characterized in that: In step S8, the Fenton reaction tank adjusts the pH to 3-4 and uses H2O2 and Fe2+ to treat the refractory organic matter; the wastewater after decolorization is separated by coagulation reaction and sedimentation in an efficient sedimentation tank.

10. The landfill leachate wastewater treatment system according to claim 1, characterized in that: In step S9, the filtration method of the physicochemical sludge and the biochemical sludge is screw filter press.

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