LU504592B1

LU504592B1 - Flexible treatment method of landfill leachate

Info

Publication number: LU504592B1
Application number: LU504592A
Authority: LU
Inventors: Haihua Min; Song Wang; Lejun Zhao; Xinxin Song; Kun Yang; Wenhui Xia; Zhili Shi
Original assignee: Tianjin Municipal Engineering Design & Res Institute Co Ltd
Priority date: 2022-12-09
Filing date: 2023-06-27
Publication date: 2024-01-09
Also published as: CN116081861A; CN116081861B

Abstract

The invention including : flowing the leachate into a regulating tank for regulating a pH value; flowing into a rotating biological contactor unit to remove organic pollutants and achieve nitrification; flowing by gravity into a bottom of an anoxic denitrification reaction tank to remove nitrate nitrogen and the organic pollutants; flowing by gravity into a shortcut nitrification reaction tank to convert part of ammonia nitrogen into nitrite nitrogen; flowing into an anaerobic ammonia oxidation reaction tank to convert the nitrate nitrogen and nitrate nitrogen into nitrogen; flowing by gravity into a primary coagulating sedimentation tank; flowing into a Fenton-persulfate catalytic oxidation reaction tank to degrade organic pollutants in wastewater; flowing into an ozone catalytic oxidation reaction tank to treat the organic pollutants by ozone; and flowing into a secondary coagulating sedimentation tank for adsorption by activated carbon and sedimentation separation by the coagulant in sequence to obtain treated effluent water.

Description

DESCRIPTION LU504592

FLEXIBLE TREATMENT METHOD OF LANDFILL LEACHATE

FIELD OF THE APPLICATION

[0001] The present invention belongs to the field of environmental pollution control, and particularly relates to a flexible treatment method of an aged leachate from a landfill site of municipal solid wastes/a mixed leachate from municipal solid wastes and food wastes.

BACKGROUND ART

[0002] At present, sanitary landfill is one of the most important disposal ways for municipal solid wastes in China. The landfill leachate will be generated in a landfill process or after landfill closure, and currently, the yield of the landfill leachate in China has reached 30 million tons above every year. The landfill leachate is complex in wastewater components and high in pollution load, which contains high-concentration organic matter, high-concentration ammonia nitrogen, heavy metal ions and other pollutants. The leachate may cause severe pollution to surrounding environment if it is directly discharged. Thus, the leachate needs to be treated by specific process units, and is allowed to be discharged into sewers or water bodies after meeting emission standards.

[0003] Though the concentration of organic matter in the aged leachate generated in a sanitary landfill site (or a closed landfill site) of municipal solid wastes is not high, most of the organic matter is biorefractory, contains a large number of humic acids, fulvic acids and other biorefractory components, and low in BODs/CODer and poor in biodegradability. Meanwhile, the leachate is high in concentration of ammonia nitrogen, which is between 1000 and 5000 mg-L™!, and high in salinity and contents of heavy metal ions and other toxic substances; and the heavy metal ions are enriched in the aged leachate after a long-time accumulation, which has a great influence on environment. A conventional denitrification process needs a large number of additional carbon sources, and is low in treatment efficiency and high in cost. The existing treatment technologies for such landfill leachate mainly include multistage anoxic-oxic biological-biomass membrane bioreactors, and an ultrafiltration filter-reverse osmosis or nanofiltration technological method is adopted for advanced treatment. Though a higher quality of effluent water is achieved by such technological method, the process is complex, a large number of additional carbon sources is required, and microfiltration membranes for membrane bioreactors, ultrafiltration membranes for an ultrafiltration stage and reverse osmosis membranes have high pollution resistance requirements and short service life. More concentrated liquids hard to treat are generated in a reverse osmosis stage, which need to be treated by evaporation hy 904598 meet relevant emission standards. These conventional processes are high in investment costs and treatment costs, and complex in facilities and operation management.

[0004] Therefore, it is important to develop a flexible treatment method suitable for treating an aged leachate from a landfill site of municipal solid wastes/a mixed leachate from municipal solid wastes and food wastes.

BRIEF SUMMARY OF THE INVENTION

[0005] The present invention aims to overcome the shortcomings in the prior art, and provides a flexible treatment method suitable for an aged leachate from an aged (especially closed) landfill site of municipal solid wastes or a mixed leachate from municipal solid wastes and food wastes.

According to the method, advanced biofilm anoxic denitrification, biofilm shortcut nitrification and biofilm anaerobic ammonium oxidation technologies are combined with a multistage high- efficiency catalytic oxidation technology to effectively remove COD, nitrogen and phosphorus pollutants and heavy metals from the leachate without using a membrane treatment technology.

The method is suitable for treating a biorefractory aged leachate containing low-concentration organic matter and high-concentration ammonia nitrogen, as well as a mixed leachate containing oil.

[0006] A flexible treatment method of a landfill leachate applies a wastewater treatment system which includes the following units: a regulating tank, a rotating biological contactor unit, an anoxic denitrification reaction tank, a shortcut nitrification reaction tank, an anaerobic ammonia oxidation reaction tank, a primary coagulating sedimentation tank, a Fenton-persulfate catalytic oxidation reaction tank, an ozone catalytic oxidation reaction tank and a secondary coagulating sedimentation tank.

[0007] The method includes the following steps:

[0008] step 1: flowing the leachate by gravity into or pumping the leachate into the regulating tank, and regulating a pH value of wastewater, wherein retention time of the leachate in the regulating tank is greater than 48 hours, and a pH value of effluent water is controlled at 7-9;

[0009] step 2: flowing wastewater discharged from a water outlet in a bottom of the regulating tank into the rotating biological contactor unit through a pipeline to remove organic pollutants from the leachate and achieve nitrification, wherein contact time of the wastewater with an oxidation tank in the rotating biological contactor unit is greater than or equal to 6 hours, and hydraulic loads of surfaces of discs are less than or equal to 0.08 m°/(m°.d); after the wastewater. 904598 passes through the rotating biological contactor unit, a removal rate of CODer therein ranges from 20% to 30%, and a degradation rate of ammonia nitrogen ranges from 60% to 80%;

[0010] step 3: flowing wastewater discharged from a water outlet of the rotating biological contactor unit by gravity into a bottom of the anoxic denitrification reaction tank through a pipeline to remove nitrate nitrogen and organic pollutants from effluent water from the rotating biological contactor unit, wherein hydraulic retention time in the anoxic denitrification reaction tank is greater than 3 days, and a concentration of dissolved oxygen is controlled below 0.5 mg/L; a removal rate of COD; by the anoxic denitrification reaction tank is 60%, and a removal rate of total nitrogen (TN) ranges from 60% to 70%;

[0011] step 4flowing wastewater discharged from the anoxic denitrification reaction tank by gravity into the shortcut nitrification reaction tank for converting residual unconverted ammonia nitrogen in effluent water from the anoxic denitrification reaction tank into nitrite nitrogen, wherein hydraulic retention time in the shortcut nitrification reaction tank is controlled at 2-3 days;

[0012] step 5: flowing wastewater discharged from the shortcut nitrification reaction tank by gravity into a bottom of the anaerobic ammonia oxidation reaction tank for converting ammonia nitrogen and nitrate nitrogen in the wastewater into nitrogen under anaerobic conditions, wherein hydraulic retention time in the anaerobic ammonia oxidation reaction tank is greater than 3 days; after the wastewater passes through the anaerobic ammonia oxidation reaction tank, the removal rate of the total nitrogen therein reaches 90%, and the removal rate of the COD, therein reaches 70%:

[0013] step 6: flowing wastewater discharged from the anaerobic ammonia oxidation reaction tank by gravity into the primary coagulating sedimentation tank, wherein coagulating reaction time is greater than 20 minutes, and a surface load of a sedimentation tank of the primary coagulating sedimentation tank is less than 0.5 m*/(m? h);

[0014] step 7: flowing wastewater discharged from the primary coagulating sedimentation tank by gravity into the Fenton-persulfate catalytic oxidation reaction tank to degrade the organic pollutants in the wastewater by a Fenton and persulfate composite oxidation technology;

[0015] step 8: flowing wastewater discharged from the Fenton-persulfate catalytic oxidation reaction tank into the ozone catalytic oxidation reaction tank to treat refractory organic pollutants by catalytic ozonation of the leachate, wherein an ozone source 1s an oxygen source or an air source; and 1006002

[0016] step 9: flowing wastewater discharged from the ozone catalytic oxidation reaction tank into the secondary coagulating sedimentation tank for secondary coagulation and sedimentation, and finally discharging acceptable water through a water outlet, and sludge settling at the bottoms of the coagulating sedimentation tanks through sludge outlets.

[0017] Furthermore, the flexible treatment method 1s suitable for treating an aged leachate from a closed landfill site of municipal solid wastes, CODer of influent water of the leachate ranges from 2000 to 3000 mg/L, a concentration of ammonia nitrogen ranges from 500 to 1000 mg/L; treated effluent water meets the following conditions: the COD. < 100 mg/L, the ammonia nitrogen < 25 mg/L, the total nitrogen < 40 mg/L, and total phosphorus < 3 mg/L.

[0018] Furthermore, the flexible treatment method is suitable for treating a mixed leachate from municipal solid wastes and food wastes; CODer of influent water of the mixed leachate ranges from 8000 to 15000 mg/L, a concentration of ammonia nitrogen ranges from 500 to 1000 mg/L; treated effluent water meets the following conditions: the COD, < 500 mg/L, suspended solids (SS) < 400 mg/L, the ammonia nitrogen < 35 mg/L, the total nitrogen < 70 mg/L, and the total phosphorus < 3 mg/L.

[0019] Wherein, during treatment to the mixed leachate from municipal solid wastes and food wastes, the wastewater treatment system further includes a coagulating flotation tank, and the coagulation flotation tank is communicated with the regulating tank and the rotating biological contactor unit through pipelines respectively; after execution of step 1, the method further includes:

[0020] flowing the wastewater from the regulating tank into the coagulating flotation tank through a pipeline, wherein the coagulating flotation tank includes a coagulation reaction zone, a contact zone and a flotation tank separation zone; firstly mixing the wastewater from the regulating tank with 100-500 mg/L of polyferric chloride and 3-5 mg/L of polyacrylamide coagulant which are added in the coagulation reaction zone to react, then flowing the wastewater into the contact zone from the bottom to mix and contact with dissolved air water to overflow into the flotation tank separation zone located at an upper part of the contact zone, thereby removing suspended solids, colloidal pollutants and grease from the wastewater, wherein a concentration of animal and vegetable oils in the effluent water passing through the coagulating flotation tank is decreased to below 50 mg/L, and the concentration of the suspended solids is decreased to below 100 mg/L. 1006002

[0021] Furthermore, the rotating biological contactor unit has effects of removing organic pollutants (CODer) from the leachate and achieving nitrification. The rotating biological contactor unit includes a plurality of axially arranged discs and an oxidation tank, and the discs are connected by a center shaft and long fixing screws, and submerged by less than 1/2. The discs are perforated corrugated plates with a corrugated height ranging from 1 to 3 cm, and corrugations on the two adjacent perforated corrugated plates are staggered obliquely. The corrugated plates are made from stainless steel or PP and PVC plastics, a void percentage of the rotating biological contactor unit integrated by combination is greater than 95%, and a specific surface area is greater than 250 m’/m°. A diameter of each of the discs of the rotating biological contactor unit is allowed to be designed according to a quantity of treated wastewater, and a diameter specification D ranges from 1 to 2.5 m. The rotating biological contactor unit is driven by slow-speed motors, and a rotational speed of the discs is controlled at 2-4 rpm.

[0022] Furthermore, all the anoxic denitrification reaction tank, the shortcut nitrification reaction tank and the anaerobic ammonia oxidation reaction tank are filled with suspended ball fillers which are hollow balls with a diameter ranging from 80 to 100 mm, and a filling volume ratio of the reaction tanks ranges from 40% to 60%. Spiral fiber biofilms are attached to outer surfaces of the suspended ball fillers, an attachable specific surface area is greater than 4000 m°/m°, and a void percentage is greater than 95%.

[0023] Furthermore, a reflux port is further formed in a bottom of the anaerobic ammonia oxidation reaction tank, and the reflux port is communicated with a reflux pump through a pipeline. The other end of the reflux pump is connected with the anoxic denitrification reaction tank through a pipeline for feeding a reflux mixture to an inlet of the anoxic denitrification reaction tank, and an internal reflux ratio ranges from 50% to 100%.

[0024] Furthermore, sludge outlets are formed in the bottoms of the primary coagulating sedimentation tank and the secondary coagulating sedimentation tank, respectively, and used for discharging sludge settling at the bottoms of the coagulating sedimentation tanks. The sludge is mechanically dehydrated and dried to form sludge cakes for outward transport.

[0025] Furthermore, agents and suspended solids in the wastewater are quickly mixed by stirrers in the primary coagulating sedimentation tank, the Fenton-persulfate catalytic oxidation reaction tank and the secondary coagulating sedimentation tank, thereby facilitating fast sedimentation of the suspended solids. 1006508

[0026] Furthermore, the coagulant is 1-5 g/L of polyferric chloride, and a coagulant aid 1s 3-5 mg/L of polyacrylamide.

[0027] The present invention has the following advantages and beneficial effects:

[0028] 1. According to the present invention, based on the water quality characteristics of the aged (or closed landfill) leachate from the landfill site of municipal solid wastes and the mixed leachate from municipal solid wastes and food wastes, the flexible treatment method is adopted in a unit combination manner, that is, a new combination of biochemistry and physicochemistry, and an advanced technical combination of anoxic denitrification-shortcut nitrification-anaerobic ammonia oxidation-multistage chemical oxidation are used for the aged leachate from an aged (especially closed) landfill site of municipal solid wastes; and for treatment to the mixed leachate from municipal solid wastes and food wastes, the coagulating flotation tank unit is added based on the above method to remove grease. Therefore, the flexible treatment based on the water quality characteristics is achieved;

[0029] 2. In the present invention, a membrane separation technology is not used in treatment of the landfill leachate; the main components in the treatment method include: the regulating tank, the rotating biological contactor, the anoxic denitrification reaction tank, the shortcut nitrification reaction tank, the anaerobic ammonia oxidation reaction tank, the primary coagulating sedimentation tank, the Fenton-persulfate catalytic oxidation reaction tank, the ozone catalytic oxidation reaction tank and the secondary coagulating sedimentation tank;

[0030] 3. The suspended ball fillers with the spiral fiber biofilms being attached to outer surfaces thereof are filled in the anoxic denitrification reaction tank, the shortcut nitrification reaction tank and the anaerobic ammonia oxidation reaction tank to form the high-efficiency biofilm reaction tank.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG. la is a structural schematic diagram of a system suitable for treating an aged (or closed landfill) leachate from a landfill site of municipal solid wastes in Embodiment 1; FIG. 1b is a structural schematic diagram of a system suitable for treating a mixed leachate from municipal solid wastes and food wastes in Embodiment 2;

[0032] FIG. 2a is a flow chart of a treatment method suitable for an aged (or closed landfill) leachate from a landfill site of municipal solid wastes in Embodiment 1; and FIG. 2b is a flow 0% chart of a treatment method suitable for a mixed leachate from municipal solid wastes and food wastes in Embodiment 2.

[0033] Wherein:

[0034] 1: regulating tank

[0035] 2: Coagulating flotation tank

[0036] 3: Rotating biological contactor unit with obliquely staggered corrugated plates

[0037] 4: Anoxic denitrification reaction tank

[0038] 5: Shortcut nitrification reaction tank

[0039] 6: Anaerobic ammonia oxidation reaction tank

[0040] 7: Primary coagulating sedimentation tank

[0041] 8: Fenton-persulfate catalytic oxidation reaction tank

[0042] 9: Ozone catalytic oxidation reaction tank

[0043] 10: Adsorption reaction tank

[0044] 11: Secondary coagulating sedimentation tank

[0045] 12: Reflux pump

[0046] 13: Lift pump

[0047] 14: Intake pump

[0048] 15: Air blower

[0049] 16: Stirrer

[0050] 17: Filler

[0051] 18: Flow meter

[0052] 19: Motor

LU504592

[0053] AA: Rotating contactor bracket

[0054] BB: Discharge effluent water

[0055] CC: Discharge sludge

[0056]

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0057] The present invention will be further described below with reference to drawings and specific embodiments. The embodiments of the present invention are construed to allow those skilled in the art to better understand the present invention, instead of limiting it in any manner.

The working process and principles of the present invention will be further described by taking a preferred embodiment of the present invention as an example.

[0058] Embodiment 1: aged leachate from landfill site of municipal solid wastes

[0059] The embodiment is suitable for treating the aged (or closed landfill) leachate from the landfill site of municipal solid wastes. CODer of influent water of the leachate ranges from 2000 to 3000 mg/L; a concentration of ammonia nitrogen ranges from 500 to 1000 mg/L; the treated effluent water meets the requirements of Standard for Pollution Control on the Landfill Site of

Municipal Solid Waste (GB/T 16889-2008) , having the following main indexes: COD< 100 mg/L, ammonia nitrogen < 25mg/L, total nitrogen < 40mg/L, and total phosphorus < 3mg/L.

[0060] A flexible treatment method suitable for treating an aged (or closed landfill) leachate from a landfill site of municipal solid wastes applies a system specifically including the following units as shown in FIG. la: a hageding tank 1, a rotating biological contactor unit 3 with obliquely staggered corrugated plates, an anoxic denitrification reaction tank 4, a shortcut nitrification reaction tank 5, an anaerobic ammonia oxidation reaction tank 6, a primary coagulating sedimentation tank 7, a Fenton-persulfate catalytic oxidation reaction tank 8, an ozone catalytic oxidation reaction tank 9, an adsorption reaction tank 10 and a secondary coagulating sedimentation tank 11, which are connected in sequence; and a water flow direction is shown by arrows in the figure.

[0061] As shown in FIG. 2a, the specific treatment steps are as follows:

[0062] step 1: the leachate from a closed aged landfill site of municipal solid wastes is pumped into the regulating tank 1, and an aeration stirring equipment is arranged in the regulating tank 9598 retention time of the leachate in the regulating tank 1 is greater than 48 hours, and wastewater is continuously or intermittently stirred by a stirrer in the regulating tank 1 to regulate a pH value of the wastewater in the regulating tank; a pH value of effluent water is controlled at 7-9;

[0063] step 2: the wastewater from the regulating tank 1 flows into the rotating biological contactor unit 3 with the obliquely staggered corrugated plates through a flow meter 18 after flowing through a lift pump 13 via a pipeline.

[0064] The rotating biological contactor unit 3 with the obliquely staggered corrugated plates has effects of removing organic pollutants (CODer) from the leachate and achieving nitrification.

The rotating biological contactor unit 3 includes a plurality of axially arranged discs and an oxidation tank; the discs are connected by a center shaft and long fixing screws, and submerged by less than 1/2; and a water level of the rotating biological contactor unit is higher than that of the anoxic denitrification reaction tank 4. The discs are perforated corrugated plates with a corrugated height ranging from 1 to 3 cm, and two adjacent perforated corrugated plates are arranged with corrugations being staggered obliquely; the corrugated plates are made from stainless steel or PP and PVC plastic, and a void percentage of the rotating biological contactor unit with the obliquely staggered corrugated plates integrated by combination is greater than 95%; and a specific surface area is greater than 250 m°/m°. A diameter of each of the discs of the rotating biological contactor unit is allowed to be designed according to a quantity of treated wastewater, and a diameter specification D ranges from 1 to 2.5 m. The contact time of the wastewater in an oxidation tank is greater than or equal to 6 hours, and hydraulic loads of surfaces of the discs are less than or equal to 0.08 m*/(m°.d). The oxidation tank of the rotating biological contactor is made from fiberglass reinforced plastic or stainless steel. A denitrification microbial inoculant is inoculated when the rotating biological contactor is started.

[0065] After the wastewater passes through the rotating biological contactor unit 3 with the obliquely staggered corrugated plates, a removal rate of COD, therein approximately ranges from 20% to 30%, and a degradation rate of ammonia nitrogen approximately ranges from 80% to 90%; wherein, during strain acclimation in the rotating biological contactor unit, for treatment to the leachate from an aged closed landfill site of municipal solid wastes, the denitrification microbial inoculant is inoculated when the rotating biological contactor unit 3 is started, the rotational speed ranges from 2 to 4 rpm, and the system is stable after continuous operation for 3 months.

[0066] For the aged leachate, a biochemical system in a testing experiment stage of the rotating biological contactor unit 3 has following main operating parameters: 1006006

[0067] High-efficiency rotating biological contactor: a hydraulic load of the rotating biological contactor in unit area ranges from 0.04 to 0.06 m*/(m°.d);

[0068] a COD load ranges from 0.3 to 0.5 kg COD/(m°.d);

[0069] an ammonia nitrogen load ranges from 28 to 45 g NH;-N/(m°.d); and

[0070] the hydraulic retention time in the oxidation tank ranges from 10 to 16 h.

[0071] Step 3: the wastewater flowing out by gravity from the rotating biological contactor unit 3 with the obliquely staggered corrugated plates enters a water inlet located in a bottom of the anoxic denitrification reaction tank 4 through a pipeline; and

[0072] the anoxic denitrification reaction tank 4 has a main function of removing nitrate nitrogen and organic pollutants from effluent water from the rotating biological contactor unit. The anoxic denitrification reaction tank is of an open structure, and is divided into a water distribution zone located at its bottom and a suspended ball filler zone located at an upper part of the water distribution zone; the water inlet of the anoxic denitrification reaction tank 4 is located in the bottom of the anoxic denitrification reaction tank, and therefore the wastewater moves from bottom to top; and a filler interception grid is arranged at a water outlet, and the water outlet is located in a wall connected with the shortcut nitrification reaction tank 5, which is 0.2 m below a water surface. The suspended ball filler zone is filled with suspended ball fillers, the fillers 17 are hollow balls with a diameter ranging from 80 to 100 mm, and a filling volume ratio of the anoxic denitrification reaction tank ranges from 40% to 60%; spiral fiber biofilms are attached to outer surfaces of the suspended ball fillers, an attachable specific surface area is greater than 6000 m*/m’, and a void percentage is greater than 95%. The hydraulic retention time in the anoxic denitrification reaction tank 4 is greater than 3 days, and dissolved oxygen is controlled at 0.5 mg/L below. The amount of additional carbon sources is calculated according to an actual carbon-to-nitrogen ratio of influent water, and the carbon-to-nitrogen ratio is generally controlled to be greater than 4. After the wastewater passes through the anoxic denitrification reaction tank 4, the removal rate of COD, therein is about 60%, and the removal rate of TN therein approximately ranges from 60% to 70%;

[0073] step 4: the wastewater flows by gravity into the shortcut nitrification reaction tank 5 from an opening formed in a partition wall, abutting against the shortcut nitrification reaction tank 5 04092 of the anoxic denitrification reaction tank 4;

[0074] the shortcut nitrification reaction tank 5 has a main function of converting residual ammonia nitrogen in effluent water in the anoxic denitrification reaction tank 4 into nitrite nitrogen. The shortcut nitrification reaction tank is a completely mixed reaction tank, and the filler interception grid is arranged at the water outlet. The opening in the partition wall, abutting against the shortcut nitrification reaction tank 5, of the anoxic denitrification reaction tank 4 is located 0.2 m below the water surface. The shortcut nitrification reaction tank is filled with the suspended ball fillers which are the same as those in the anoxic denitrification reaction tank. The filling volume ratio of the fillers in the shortcut nitrification reaction tank ranges from 40% to 60%. The spiral fiber biofilms are attached to the outer surfaces of the suspended ball fillers, an attachable specific surface area is greater than 4000 m“/m°, and a void percentage is greater than 95%. A microporous aerator is arranged at a bottom of the shortcut nitrification reaction tank 5, and connected with an air blower 15 located at the exterior of the shortcut nitrification reaction tank for oxygen supply, and a concentration of dissolved oxygen is controlled at 1-2 mg/L. The hydraulic retention time in the shortcut nitrification reaction tank 5 is controlled at 2-3 days.

Through online testing of concentrations of ammonia nitrogen and nitrate nitrogen in the wastewater, a blast aeration rate is regulated, and the concentration of dissolved oxygen is controlled at 1-2 mg/L. Dissolved oxygen, oxidation reduction potential (ORP) and nitrate online monitors are further arranged in the shortcut nitrification reaction tank 5, and an air demand and dissolved oxygen are controlled according to the feedback of values monitored by the monitors.

Residual unconverted ammonia nitrogen is converted into nitrite nitrogen by the shortcut nitrification reaction tank 5 at a conversion rate of 50% or so;

[0075] step 5: the wastewater flows by gravity into a bottom of the anaerobic ammonia oxidation reaction tank 6 from an opening formed in a partition wall, abutting against the anaerobic ammonia oxidation reaction tank 6, of the shortcut nitrification reaction tank 5; and the opening formed in the wall, abutting against the anaerobic ammonia oxidation reaction tank 6, of the shortcut nitrification reaction tank 5 is located in the bottom of the shortcut nitrification reaction tank. The ammonia nitrogen and the nitrate nitrogen are converted into nitrogen in the anaerobic ammonia oxidation reaction tank 6 under anaerobic conditions. The anaerobic ammonia oxidation reaction tank features an up-flow hydraulic design, and stirring equipment is not arranged. The anaerobic ammonia oxidation reaction tank is of a sealed structure, and is divided into three zones including a water distribution zone located at its bottom, a suspended filler reaction zone located in its middle, and a clear water zone located in its upper part. A water inlet is located in the bottom of the anaerobic ammonia oxidation reaction tank, and therefore 904598 wastewater moves from bottom to top to pass through the suspended filler reaction zone in an up-flow manner; and anaerobic ammonia oxidizing bacteria (anaerobic ammonia oxidizing sludge) are inoculated when the anaerobic ammonia oxidation reaction tank 6 is started to run.

The anaerobic ammonia oxidation reaction tank is filled with the suspended ball fillers which are the same as those in the anoxic denitrification reaction tank. A diameter of hollow balls ranges from 80 to 100 mm. The filling volume ratio of the fillers in the anaerobic ammonia oxidation reaction tank ranges from 40% to 60%. The spiral fiber biofilms are attached to the outer surfaces of the suspended ball fillers, an attachable specific surface area is greater than 4000 m°/m°, and a void percentage is greater than 95%. The hydraulic retention time in the anoxic denitrification reaction tank is greater than 3 days. A reflux port is further formed in the bottom of the anaerobic ammonia oxidation reaction tank 6, and the reflux port is communicated with a reflux pump 12 through a pipeline for feeding a reflux mixture to the inlet of the anoxic denitrification reaction tank 4; and an internal reflux ratio ranges from 50% to 100%. After the reflux mixture passes through the anaerobic ammonia oxidation reaction tank, the removal rate of the total nitrogen therein reaches 90% or so, and the removal rate of the COD therein reaches 70% or so.

[0076] Step 6: the wastewater enters the primary coagulating sedimentation tank 7 from an opening formed in a partition wall, abutting against the primary coagulating sedimentation tank 7, of the anaerobic ammonia oxidation reaction tank 6; and the opening in the partition wall, abutting against the primary coagulating sedimentation tank 7, of the anaerobic ammonia oxidation reaction tank 6 is located 0.2 m below the water surface.

[0077] The primary coagulating sedimentation tank 7 is an inclined tube sedimentation tank, which includes a coagulation reaction tank and a sedimentation tank which are communicated with each other; the wastewater from an outlet of the anaerobic ammonia oxidation reaction tank 6 firstly enters the coagulation reaction tank, and a coagulant and a coagulant aid are added to the coagulation reaction tank; the coagulant is 1-5 g/L. of polyferric chloride, and the coagulant aid is 3-5 mg/L of polyacrylamide. A stirrer 16 is arranged in the coagulation reaction tank, and a rotational speed of a stirring impeller thereof ranges from 50 to 100 rpm. The stirrer is used for quickly mixing agents with suspended solids in the wastewater, and a heavier floc with a higher density is formed by taking sludge as a center, thereby facilitating fast sedimentation in the sedimentation tank. The sedimentation tank is an inclined plate sedimentation tank. The coagulation reaction time is greater than 20 minutes, and a surface load of the sedimentation tank is less than 0.5 m°/(m°h). Honeycomb inclined tubes are filled in the sedimentation tank. A wastewater distribution zone is located below inclined tubes, and a sludge zone is located a+ 904598 lower part of the wastewater distribution zone; an opening communicating the primary coagulating sedimentation tank with the sedimentation tank is formed in the wall, abutting against the sedimentation tank, of the primary coagulating sedimentation tank, and the opening is located 0.2 m below the water surface to prevent a floating drift from being taken away. The removal rate of suspended solids in the wastewater by coagulating sedimentation in this step is greater than 70%, and the removal rate of CODer is greater than 50%. A sludge outlet is further formed in the bottom of the primary coagulating sedimentation tank 7, and used for discharging sludge settling at the bottom of the primary coagulating sedimentation tank. The sludge is mechanically dehydrated and dried to form sludge cakes for outward transport; and liquid generated by sludge dehydration is also allowed to return to the anoxic denitrification reaction tank 4 for reaction. A pipeline is arranged at an effluent weir of the sedimentation tank of the primary coagulating sedimentation tank 7, and the other end of the pipeline gets in touch with a bottom of the Fenton-persulfate catalytic oxidation reaction tank 8.

[0078] step 7: the wastewater enters the Fenton-persulfate catalytic oxidation reaction tank 8 from the effluent weir of the primary coagulation oxidation tank 7:

[0079] organic pollutants in the leachate are degraded in the Fenton-persulfate catalytic oxidation reaction tank by a Fenton and persulfate composite oxidation technology. The Fenton- persulfate catalytic oxidation reaction tank features a multistage continuous mixing-reaction design. The Fenton-persulfate catalytic oxidation reaction tank is made from fiberglass reinforced plastic or engineering plastic structural materials, and a stirrer 16 is arranged in the

Fenton-persulfate catalytic oxidation reaction tank for stirring at a rotational speed ranging from to 100 rpm. According to the water concentration and treatment requirements, it is determined by small testing experiments to add 500-800 mg/L of hydrogen peroxide, 1-1.5 g/L of activated persulfate and 0.5-0.8 g/L. of ferrous sulfate catalyst, a Fenton catalytic oxidation reaction is conducted firstly, and then a persulfate oxidation reaction is conducted; and after the wastewater passes through the Fenton-persulfate catalytic oxidation reaction tank, the removal rate of CODer therein 1s 70% or so.

[0080] Step 8: the wastewater enters the ozone catalytic oxidation reaction tank 9 from an opening formed in a partition wall, abutting against the ozone catalytic oxidation reaction tank 9, of the Fenton-persulfate catalytic oxidation reaction tank 8, and the opening formed in the wall, abutting against the ozone catalytic oxidation reaction tank 9, of the Fenton-persulfate catalytic oxidation reaction tank 8 is located 0.2 m below the water surface. The ozone catalytic oxidation reaction tank 9 includes an ozone aeration zone located at its bottom, a catalytic reaction zone 06008 located in its middle, and a clear water zone located at its upper part. Refractory organic pollutants are treated by catalytic ozonation of the leachate in the ozone catalytic oxidation reaction tank 9. An ozone source is allowed to be an oxygen source or an air source. The ozone catalytic oxidation reaction tank 9 is designed in an up-flow manner (or in a multi-grid manner according to actual requirements), and ozone prepared by an ozone generation system is filled into the wastewater in the ozone aeration zone in a microporous aeration or jet aeration manner.

[0081] Step 9: the wastewater enters the secondary coagulating sedimentation tank from an opening formed in a partition wall, abutting against the secondary coagulating sedimentation tank, of the ozone catalytic oxidation reaction tank 9; and the opening in the partition wall, abutting against the secondary coagulating sedimentation tank, of the ozone catalytic oxidation reaction tank 9 is located in the bottom of the ozone catalytic oxidation reaction tank. The secondary coagulating sedimentation tank includes an adsorption reaction tank 10 and a secondary coagulating sedimentation tank 11 which are communicated with each other, and an opening used for communication is formed in a wall, abutting against the secondary coagulating sedimentation tank 11, of the adsorption reaction tank 10; effluent water from the ozone catalytic oxidation reaction tank 9 firstly enters the adsorption reaction tank 10 to in depth remove organic pollutants from the wastewater through combination of powdered activated carbon adsorption and coagulation reaction in the adsorption reaction tank 10. Firstly, 50-100 mg/L of powdered activated carbon is added for adsorption reaction for 1 hour, and then the coagulant and the coagulant aid are added for reaction for 15 minutes (the coagulant is 1-5 g/L of polyferric chloride, and the coagulant aid is 3-5 mg/L of polyacrylamide), thereby further removing the organic pollutants from the wastewater through sedimentation separation. The outlet of the adsorption reaction tank 10 is located 0.2 m below the water surface, and effluent water flows by gravity into the inlet in the bottom of the secondary coagulating sedimentation tank 11. The secondary coagulating sedimentation tank 11 is an inclined plate sedimentation tank, and suspended solids in the wastewater are further removed by a coagulating sedimentation method.

A triangular overflow weir is arranged at a water outlet of the secondary coagulating sedimentation tank, and finally, effluent water after sedimentation separation is collected by an effluent water zone. A sludge outlet is formed in the bottom of the secondary coagulating sedimentation tank 11, and used for discharging sludge settling at the bottom of the secondary coagulating sedimentation tank, and the sludge is fed to a landfill site for landfill after being mechanically dehydrated and dried in a sludge treatment room. The final effluent water meets the requirements of Standard for Pollution Control on the Landfill Site of Municipal Solid Waste (GB/T 16889-2008). 1006508

[0082] Embodiment 2: mixed leachate from municipal solid wastes and foot wastes

[0083] The embodiment is suitable for treating the mixed leachate from municipal solid wastes and food wastes. COD; of influent water of the mixed leachate ranges from 8000 to 15000 mg/L, and a concentration of ammonia nitrogen ranges from 500 to 1000 mg/L. Effluent water meets the requirements of Wastewater Quality Standards for Discharge to Municipal Sewers (GBT31962-2015), and has the following main indexes: COD: < 500 mg/L, suspended solids (SS) < 400 mg/L, ammonia nitrogen < 35 mg/L, total nitrogen< 70 mg/L, and total phosphorus< 3 mg/L.

[0084] A flexible treatment method suitable for a mixed leachate from municipal solid wastes and food wastes applies a system, as shown in FIG. 1b, specifically including: a regulating tank 1, a coagulating flotation tank 2, a rotating biological contactor unit 3 with obliquely staggered corrugated plates, an anoxic denitrification reaction tank 4, a shortcut nitrification reaction tank 5, an anaerobic ammonia oxidation reaction tank 6, a primary coagulating sedimentation tank 7, a

Fenton-persulfate catalytic oxidation reaction tank 8, an ozone catalytic oxidation reaction tank 9, an adsorption reaction tank 10 and a secondary coagulating sedimentation tank 11, which are connected in sequence; and various components are communicated with each other by pipelines.

[0085] Treatment steps are similar to those in Embodiment 1, as shown in FIG. 2b. Only differences are described below, and the same part will not be repeated.

[0086] A process unit in this embodiment is different from Embodiment 1 in that a coagulating flotation tank 2 is added after the regulating tank and before the anoxic denitrification reaction tank.

[0087] The coagulating flotation tank 2 includes a coagulation reaction zone, a contact zone and a flotation tank separation zone. Wastewater from the regulating tank flows into the coagulation reaction zone of the coagulating flotation tank through a flow meter 18 after flowing through a lift pump via a pipeline, and is mixed and reacts with 100-500 mg/L of polyferric chloride and 3- mg/L of polyacrylamide which are added. Effluent water from the reaction zone enters a bottom of the contact zone to mix and contact with dissolved air water, and then overflows into the flotation tank separation zone located at an upper part of the contact zone to remove suspended solids, colloidal pollutants and grease from the wastewater. A clear water collecting pipe is arranged at the bottom of the separation zone, and clear water is discharged from the

LU504592 bottom thereof. A sediment scraper is arranged at an upper part of the separation zone, and a sediment collecting tank is arranged at a tail end of the separation zone. A concentration of animal and vegetable oils in effluent liquid passing through the coagulating flotation tank is decreased to below 50 mg/L, and a concentration of the suspended solids is decreased to below 100 mg/L; and effluent water from the coagulating flotation tank 2 flows into or is pumped into the rotating biological contactor unit 3 with the obliquely staggered corrugated plates. And then, effluent water from the rotating biological contactor unit 3 with the obliquely staggered corrugated plates flows into the anoxic denitrification reaction tank 4.

[0088] During strain acclimation in the rotating biological contactor unit, for treatment to the mixed leachate, a denitrification microbial inoculant is inoculated when the rotating biological contactor is started at a rotational speed ranging from 2 to 4 rpm, and the system is stable after continuous operation for 1 month.

[0089] For the mixed leachate, main operating parameters controlled by main units in a testing experiment stage are as follows:

[0090] coagulating flotation tank: hydraulic retention time is 1 h, and a reflux ratio of dissolved air water 1s 30%;

[0091] high-efficiency rotating biological contactor 3: a hydraulic load of the rotating biological contactor in unit area ranges from 0.02 to 0.05 m*/(m°.d);

[0092] a COD load ranges from 0.3 to 0.5 kg COD/(m°.d);

[0093] an ammonia nitrogen load ranges from 10 to 30 g NH3-N/(m?.d); and

[0094] the hydraulic retention time in the oxidation tank ranges from 10 to 16 h.

[0095] The above described embodiments are merely descriptive of the technical thoughts and characteristics of the present invention, and are intended to enable those skilled in the art to understand the contents of the present invention and implement it accordingly, which should not be construed as limiting the patent scope of the present invention; and equivalent variations or modifications made within the spirit disclosed by the present invention still fall within the patent scope of the present invention.

Claims

CLAIMS LU504592

1. A flexible treatment method of a landfill leachate, characterized in that the treatment method applies a wastewater treatment system which comprises the following units: a regulating tank, a rotating biological contactor unit, an anoxic denitrification reaction tank, a shorteut nitrification reaction tank, an anaerobic ammonia oxidation reaction tank, a primary coagulating sedimentation tank, a Fenton-persulfate catalytic oxidation reaction tank, an ozone catalytic oxidation reaction tank and a secondary coagulating sedimentation tank; the treatment method comprises the following steps: step 1: flowing the leachate to flow by gravity into or pumping the leachate into the regulating tank (1), and regulating a pH value of wastewater, wherein retention time of the leachate in the regulating tank is greater than 48 hours, and a pH value of effluent water 1s controlled at 7-9; step 2: flowing wastewater discharged from a water outlet in a bottom of the hageding tank into the rotating biological contactor unit (3) through a pipeline to remove organic pollutants from the leachate and achieve nitrification, wherein contact time of the wastewater with an oxidation tank in the rotating biological contactor unit (3) is greater than or equal to 6 hours, and hydraulic loads of surfaces of discs are less than or equal to 0.08 m°/(m°.d); after the wastewater passes through the rotating biological contactor unit, a removal rate of COD, therein ranges from 20% to 30%, and a degradation rate of ammonia nitrogen ranges from 60% to 80%; step 3: flowing wastewater discharged from a water outlet of the rotating biological contactor unit (3) by gravity into a bottom of the anoxic denitrification reaction tank (4) through a pipeline to remove nitrate nitrogen and organic pollutants from effluent water from the rotating biological contactor unit, wherein hydraulic retention time in the anoxic denitrification reaction tank (4) is greater than 3 days, and a concentration of dissolved oxygen is controlled at 0.5 mg/L below; a removal rate of CODer by the anoxic denitrification reaction tank (4) is 60%, and a removal rate of total nitrogen (TN) ranges from 60% to 70%; step 4: flowing the wastewater by gravity into the shortcut nitrification reaction tank (5) from an opening formed in a partition wall, abutting against the shortcut nitrification reaction tank (5), of the anoxic denitrification reaction tank (4) to convert residual unconverted ammonia nitrogen in the effluent water from the anoxic denitrification reaction tank (4) into nitrite nitrogen, wherein a microporous aerator for oxygen supply is arranged in an air distribution zone at a bottom of the shortcut nitrification reaction tank (5), and a concentration of dissolved oxygen is controlled at 1-2 mg/L; the hydraulic retention time in the shortcut nitrification reaction tank (5) is controlled at 2-3 days; 1006508 step 5: flowing wastewater discharged from the shortcut nitrification reaction tank (5) by gravity into a bottom of the anaerobic ammonia oxidation reaction tank (6) to convert ammonia nitrogen and nitrate nitrogen in the wastewater into nitrogen under anaerobic conditions, wherein hydraulic retention time in the anaerobic ammonia oxidation reaction tank (6) is greater than 3 days; after the wastewater passes through the anaerobic ammonia oxidation reaction tank (6), a removal rate of total nitrogen therein reaches 90%, and the removal rate of the COD, therein reaches 70%; step 6: flowing wastewater discharged from the anaerobic ammonia oxidation reaction tank (6) by gravity into the primary coagulating sedimentation tank (7), wherein coagulation reaction time is greater than 20 minutes, and a surface load of a sedimentation tank of the primary coagulating sedimentation tank (7) is less than 0.5m°/(m°.h); step 7: flowing wastewater discharged from the primary coagulating sedimentation tank (7) by gravity into the Fenton-persulfate catalytic oxidation reaction tank (8) to degrade organic pollutants in the wastewater by a Fenton and persulfate composite oxidation technology; step 8: flowing wastewater discharged from the Fenton-persulfate catalytic oxidation reaction tank (8) into the ozone catalytic oxidation reaction tank (9) to treat refractory organic pollutants by catalytic ozonation of the leachate, wherein an ozone source is an oxygen source or an air source; and step 9: flowing wastewater discharged from the ozone catalytic oxidation reaction tank (9) to enter the secondary coagulating sedimentation tank (11) for secondary coagulation and sedimentation, and finally discharging acceptable water through a water outlet, and sludge settling at the bottom of the secondary coagulating sedimentation tank through a sludge outlet.

2. The flexible treatment method of the landfill leachate according to claim 1, characterized in that the flexible treatment method is suitable for treating a leachate from an aged closed landfill site of municipal solid wastes; CODer of influent water of the leachate ranges from 2000 to 3000 mg/L, a concentration of ammonia nitrogen ranges from 500 to 1000 mg/L; treated effluent water meets the following conditions: the CODer< 100 mg/L, the ammonia nitrogen < 25 mg/L, the total nitrogen < 40 mg/L, and total phosphorus< 3 mg/L.

3. The flexible treatment method of the landfill leachate according to claim 1, characterized in that the flexible treatment method is suitable for treating a mixed leachate from municipal 99 solid wastes and food wastes; COD; of influent water of the mixed leachate ranges from 8000 to 15000 mg/L, a concentration of ammonia nitrogen ranges from 500 to 1000 mg/L; treated effluent water meets the following conditions: the CODer< 500 mg/L, suspended solids (SS) < 400 mg/L, the ammonia nitrogen < 35 mg/L, the total nitrogen < 70 mg/L, and the total phosphorus < 3 mg/L; wherein, during treatment of the mixed leachate from the municipal solid wastes and the food wastes, the wastewater treatment system further comprises a coagulating flotation tank (2), and the coagulating flotation tank (2) is communicated with the regulating tank (1) and the rotating biological contactor unit (3) through pipelines respectively; after execution of step 1, the method further comprises: flowing the wastewater from the regulating tank (1) into the coagulating flotation tank (2) through a pipeline, wherein the coagulating flotation tank (2) comprises a coagulation reaction zone, a contact zone and a flotation tank separation zone; firstly mixing the wastewater from the regulating tank with 100-500 mg/L of polyferric chloride and 3-5 mg/L of polyacrylamide coagulant which are added in the coagulation reaction zone to react, then flowing the wastewater into the contact zone from the bottom to mix and contact with dissolved air water to overflow into the flotation tank separation zone located at an upper part of the contact zone; and thereby removing suspended solids, colloidal pollutants and grease from the wastewater, wherein a concentration of animal and vegetable oils in effluent water passing through the coagulating flotation tank (2) is decreased to below 50 mg/L, and a concentration of the suspended solids is decreased to below 100 mg/L.

4. The flexible treatment method of the landfill leachate according to claim 1, characterized in that all the anoxic denitrification reaction tank (4), the shortcut nitrification reaction tank (5) and the anaerobic ammonia oxidation reaction tank (6) are filled with suspended ball fillers (17) which are hollow balls with a diameter ranging from 80 to 100 mm, and a filling volume ratio of the reaction tanks ranges from 40% to 60%; spiral fiber biofilms are attached to outer surfaces of the suspended ball fillers, and an attachable specific surface area is greater than 4000 m°/m°; and a void percentage is greater than 95%.

5. The flexible treatment method of the landfill leachate according to claim 1, characterized in that a reflux port is further formed in a bottom of the anaerobic ammonia oxidation reaction tank (6), and the reflux port is communicated with a reflux pump (12) through a pipeline; the other end of the reflux pump (12) is connected with the anoxic denitrification reaction tank (4) through a pipeline for feeding a reflux mixture to an inlet of the anoxic denitrification reaction. P0409 tank (4) for re-filtering; and an internal reflux ratio ranges from 50% to 100%.

6. The flexible treatment method of the landfill leachate according to claim 1, characterized in that sludge outlets are formed in bottoms of the primary coagulating sedimentation tank (7) and the secondary coagulating sedimentation tank, and used for discharging sludge settling at the bottoms thereof.

7. The flexible treatment method of the landfill leachate according to claim 1, characterized in that agents and suspended solids in the wastewater are quickly mixed by stirrers (16) in the primary coagulating sedimentation tank (7), the Fenton-persulfate catalytic oxidation reaction tank (8) and the secondary coagulating sedimentation tank.

8. The flexible treatment method of the landfill leachate according to claim 1, characterized in that the coagulant is 1-5 g/L. of polyferric chloride, and the coagulant aid is 3-5 mg/L of polyacrylamide.