Landfill leachate treatment method based on organic matter molecular weight control

Abstract

The invention provides a landfill leachate treatment system based on organic matter molecular weight control and a method for treating landfill leachate by using the system, and the method comprises the following steps: treating the landfill leachate through a pretreatment unit, a deamination membrane unit and an ultrafiltration membrane unit in sequence, enabling the trapped fluid of the ultrafiltration membrane unit to flow back as the inlet water of the ultrafiltration membrane unit, and continuously treating by the ultrafiltration membrane unit to obtain a trapped concentrated solution and ultrafiltration water; treating the trapped concentrated solution through a Fenton advanced oxidation unit to obtain Fenton effluent; fenton effluent is mixed with ultrafiltration water, and the mixture is treated by an A / O-MBR treatment unit. The sewage treatment cost is reduced, secondary pollution is reduced, the sewage treatment efficiency and the water purification effect are improved, a physical, chemical and biological coupling method is adopted, the method has the advantages of being low in medicine consumption, short in treatment streamline and small in concentrated water generation amount, the quality of treated water can stably meet the requirement of GB16889-2008, and accurate treatment of organic matter is achieved.

Description

Technical Field

[0001] The invention relates to a method for treating landfill leachate based on organic matter molecular weight control, and belongs to the technical field of sewage treatment. Background Art

[0002] With the rapid economic development and the sharp increase in population, the amount of urban domestic waste in the world has increased year by year. In response to the generation of such a large amount of domestic waste, the main disposal methods currently adopted by developing countries are landfill and incineration. However, both landfill and incineration processes will produce leachate. Since leachate contains a variety of difficult-to-degrade pollutants, heavy metals, chlorinated organic compounds, etc., it is very difficult to effectively treat it.

[0003] There are several types of leachate treatment methods: conventional methods (i.e., recycling to landfills and transferring to sewage treatment plants), biological, chemical, and physical methods. Conventional methods are easy to maintain and low in cost, but have low treatment efficiency and may lead to the accumulation of soluble substances that are difficult to biodegrade, making them more difficult to treat. Although biological methods have good cost-effectiveness, they are ineffective for soluble substances that are difficult to biodegrade. The problems with chemical methods are the large amount of chemical reagents used, pH dependence, and secondary pollution. Among the physical methods, membrane treatment is considered to be a promising method for treating leachate in recent decades due to its outstanding characteristics such as small footprint, large volume load, good effluent quality, and strong disinfection ability. However, considering the complexity of the water quality of leachate, in order to meet the corresponding emission standards, the actual situation is that physical, chemical, and biological coupling processes must be adopted. However, the existing physical, chemical, and biological coupling treatment technologies for leachate have problems such as long treatment lines, high drug and power consumption, and large amounts of concentrated water produced. Summary of the invention

[0004]

Technical issues

[0005] The existing physical, chemical and biological coupling treatment technologies for landfill leachate have problems such as long treatment flow lines, high drug and electricity consumption, and large amounts of concentrated water produced.

[0006]

Technical solution

[0007] In order to solve the above problems, the present invention uses the principle of separation membrane gradient screening to separate the landfill leachate into difficult-to-biodegrade organic matter components and easily biodegradable organic matter components according to their molecular weight, and then treats each component separately using targeted technologies.

[0008] like Figure 1 , 2As shown, the present invention first uses a pretreatment unit to remove large suspended particles in the landfill leachate, and uses a deammoniation membrane unit to achieve the removal of most of the ammonia nitrogen in the landfill leachate. Then, the interception performance of the ultrafiltration membrane is applied to screen the deammonified landfill leachate into high molecular weight difficult-to-biodegrade organic components and low molecular weight easy-to-biodegrade organic components through large flow circulation and cross-flow filtration. Next, the Fenton advanced oxidation unit is used to carry out targeted treatment on the high molecular weight difficult-to-biodegrade organic components, effectively remove the difficult-to-degrade organic matter, and improve its biodegradability. Finally, the A / O-MBR treatment unit is used to mix the effluent treated by Fenton and the low molecular weight biodegradable organic components filtered by the ultrafiltration membrane as the influent, and further remove the organic matter, ammonia nitrogen, total nitrogen and total phosphorus in the leachate, and the effluent water quality can stably meet the standards of Table 2 in the "Standards for Pollutant Control of Municipal Waste Landfills" (GB16889-2008).

[0009] The first object of the present invention is to provide a landfill leachate treatment system based on organic matter molecular weight control, comprising a pretreatment unit, a deamination membrane unit, an ultrafiltration membrane unit, a Fenton advanced oxidation unit and an A / O-MBR treatment unit; wherein the pretreatment unit, the deamination membrane unit, the ultrafiltration membrane unit, the Fenton advanced oxidation unit and the A / O-MBR treatment unit are connected in sequence, and the ultrafiltration membrane unit is also connected to the A / O-MBR treatment unit.

[0010] In one embodiment of the present invention, the effluent of the pretreatment unit is passed into a deamination membrane unit, the effluent of the deamination membrane unit is passed into an ultrafiltration membrane unit, the retentate of the ultrafiltration membrane unit is passed into a Fenton advanced oxidation unit, and the effluent of the Fenton advanced oxidation unit and the effluent of the ultrafiltration membrane unit are mixed and passed into an A / O-MBR treatment unit.

[0011] In one embodiment of the present invention, the water outlet of the pretreatment unit is connected to the water inlet of the deamination membrane unit, the water outlet of the deamination membrane unit is connected to the water inlet tank of the ultrafiltration membrane unit, the water inlet tank of the ultrafiltration membrane unit is also connected to the Fenton advanced oxidation unit, the water outlet of the ultrafiltration membrane unit is connected to the water collection tank, the water outlet of the Fenton advanced oxidation unit is connected to the water collection tank, and the water collection tank is connected to the water inlet of the A / O-MBR treatment unit.

[0012] The retentate is the liquid that is retained on one side of the membrane assembly during the wastewater treatment process of the ultrafiltration membrane unit due to the presence of substances with diameters larger than the micropores on the surface of the membrane assembly that are difficult to pass through the membrane assembly. The ultrafiltration water (the effluent of the ultrafiltration membrane unit) is the liquid that has passed through the membrane assembly of the ultrafiltration membrane unit and is not retained on one side of the membrane assembly.

[0013] In one embodiment of the present invention, the pretreatment unit is a polypropylene (PP) bag filter with a pore size of 0.9 to 1.1 microns.

[0014] In one embodiment of the present invention, the membrane assembly of the deamination membrane unit is a hollow fiber membrane with a diameter of 45-55 mm, a length of 620-630 mm, and a membrane area of ​​1.6-1.8 m 2 ; The material is polytetrafluoroethylene (PTFE).

[0015] In one embodiment of the present invention, the ultrafiltration membrane unit comprises a filtration component and a membrane component; the filtration component is a filter whose filter element is PP cotton; the membrane component is a polyethersulfone (PES) membrane; and the membrane component has a molecular weight cutoff of 1k Da.

[0016] In one embodiment of the present invention, the Fenton advanced oxidation unit includes a reactor, a dosing device and a stirrer, and the effective volume of the reactor is 5L.

[0017] In one embodiment of the present invention, the A / O-MBR treatment unit comprises an anoxic tank (A tank) and an aerobic tank (O tank), and the A tank and the O tank are connected through a connecting port at the bottom; the A tank is provided with a stirring device to maintain an anoxic state; a perforated pipe is provided at the bottom of the O tank to maintain an aerobic environment, and the O tank is also provided with a microfiltration membrane (MF membrane) assembly, and the MF membrane assembly is immersed in the O tank.

[0018] In one embodiment of the present invention, the influent of the A / O-MBR treatment unit flows into the O pool after being treated in the A pool, and part of the mud-water mixture in the O pool flows back to the A pool, and finally passes through the MF membrane filtration and leaves the system to obtain the effluent of the A / O-MBR treatment unit. The A / O-MBR treatment can further remove organic matter, ammonia nitrogen, total nitrogen and total phosphorus in the landfill leachate, and the effluent water quality can stably meet the standards of Table 2 in the Pollutant Control Standards for Municipal Solid Waste Landfills (GB16889-2008).

[0019] In one embodiment of the present invention, the total effective volume of the A / O-MBR treatment unit is 6.2-6.4 L, the effective volume ratio of the A pool to the O pool is 1:1.5-1:2.5; the MF membrane component is made of polyvinylidene fluoride (PVDF); a flat membrane is used; the effective area is 0.030-0.034 m 2 ; The pore size is 0.1 to 0.4 microns.

[0020] The second object of the present invention is to provide a method for treating landfill leachate using the landfill leachate treatment system, comprising the steps of:

[0021] (1) Pretreatment: The garbage leachate is treated by a pretreatment unit to obtain effluent from the pretreatment unit;

[0022] (2) Deamination membrane treatment: The effluent from the pretreatment unit is pH-adjusted and treated by the deamination membrane unit. The pH of the absorption liquid is maintained during the treatment process to obtain the effluent from the deamination membrane unit;

[0023] (3) Ultrafiltration membrane treatment: The pH of the effluent from the deammoniation membrane unit is adjusted, and the effluent is treated by the ultrafiltration membrane unit, so that the retentate of the ultrafiltration membrane unit is refluxed as the influent of the ultrafiltration membrane unit and continuously treated by the ultrafiltration membrane unit to obtain retentate concentrate and ultrafiltration water;

[0024] (4) Fenton advanced oxidation treatment: the pH of the retained concentrated solution is adjusted, ferrous sulfate solution and hydrogen peroxide solution are added and mixed to obtain a Fenton reaction solution, which is reacted in a Fenton advanced oxidation unit, the pH is adjusted to terminate the reaction, and the iron sludge is removed to obtain Fenton effluent;

[0025] (5) A / O-MBR treatment: The Fenton effluent is mixed with the ultrafiltration water and treated in an A / O-MBR treatment unit to obtain treated water.

[0026] In one embodiment of the present invention, in step (2), the pH of the effluent from the pretreatment unit is adjusted to 10.0±0.1; the absorption liquid is a sulfuric acid aqueous solution; the sulfuric acid concentration of the sulfuric acid aqueous solution is ≥0.2 mol / L; and the pH of the absorption liquid is maintained at <2.

[0027] In one embodiment of the present invention, in step (2), the influent enters the deamination membrane unit through the water inlet on the shell side of the deamination membrane, the absorption liquid enters the tube side for circulation, and the effluent leaves the deamination membrane unit through the water outlet on the shell side of the deamination membrane. The ammonia nitrogen in the influent passes through the deamination membrane and is absorbed by the absorption liquid. The absorption liquid after circulation is evaporated and crystallized, and the purity of ammonium sulfate can reach more than 98%, which can be recovered as ammonium salt.

[0028] In one embodiment of the present invention, in step (3), the pH is adjusted to 7.0-8.0; the influent is ultrafiltered by a pressure pump, and the operating pressure is 2.0-2.5 bar; the retentate obtained by the ultrafiltration membrane unit treatment is returned to the inlet tank and continuously filtered until the retention volume ratio is 10-15%, and the obtained retentate is a retentate concentrate.

[0029] The interception volume ratio is the volume percentage of the intercepted concentrated liquid to the ultrafiltration membrane unit treatment liquid (the deamination membrane unit effluent after pH adjustment).

[0030] In one embodiment of the present invention, in step (4), the pH of the retained concentrate is adjusted to 4.0±0.1; the added ferrous sulfate solution and hydrogen peroxide solution are n(Fe 2+ ):n(H2O2)=1:5~1:7(mol:mol); add ferrous sulfate solution to make Fe in Fenton reaction solution 2+ The concentration is 0.060-0.068 mol / L; hydrogen peroxide solution is added to make the hydrogen peroxide concentration in the Fenton reaction solution 0.3-0.5 mol / L; the pH is adjusted to 7.5-7.8 to terminate the reaction; and the iron mud is removed by static sedimentation and suction filtration.

[0031] In one embodiment of the present invention, in step (4), the reaction temperature in the Fenton advanced oxidation unit is 15-35° C., the stirring speed is 100-200 r / min, and the reaction time is 0.5-2 h.

[0032] In one embodiment of the present invention, the sludge needs to be acclimatized before performing step (5).

[0033] In one embodiment of the present invention, the method for acclimating sludge is to mix landfill leachate with domestic sewage to obtain an acclimation liquid, perform sequencing batch acclimation on aerobic activated sludge to obtain an aerobic activated sludge mixed liquid, inoculate it into an A / O-MBR treatment unit, operate the A / O-MBR treatment unit, use the acclimation liquid as influent, continue acclimation, after the COD of the effluent of the A / O-MBR treatment unit is stable, use the mixed liquid of landfill leachate and domestic sewage as influent and increase the proportion of landfill leachate in the influent, after the COD removal rate is stable, complete the sludge acclimation of the A / O-MBR treatment unit.

[0034] In one embodiment of the present invention, in the method for acclimating sludge, the volume of landfill leachate in the acclimation liquid: the volume of domestic sewage = 1:8 to 1:10; the influent flux is 4 to 5 LMH; the ratio of landfill leachate in the influent is increased so that the volume of landfill leachate in the influent: the volume of domestic sewage = 1:5 to 1:7.

[0035] In one embodiment of the present invention, in step (5), the dissolved oxygen in pool A is maintained at 0.2-0.5 mg / L; the dissolved oxygen in pool O is maintained at 2.0-5.0 mg / L; the reflux ratio is 100%-200%; the MF membrane module is operated at a constant flux; and the temperature of the A / O-MBR treatment is 25±2°C.

[0036] The reflow ratio is the volume flow ratio of the mud-water mixture reflowing to pool A to the influent water of the A / O-MBR treatment unit, expressed as a percentage.

[0037] The third object of the present invention is to use the above-mentioned garbage leachate treatment system or garbage leachate treatment method in sewage treatment.

[0038] Beneficial effects:

[0039] (1) The present invention utilizes the interception effect of the ultrafiltration membrane to screen the landfill leachate into high molecular weight organic matter components and low molecular weight organic matter components, and then uses the Fenton advanced oxidation unit to carry out targeted treatment of the high molecular weight difficult-to-biodegrade organic matter components, effectively remove the difficult-to-degrade organic matter, and improve its biodegradability, so that the landfill leachate has strong biodegradability, and then carries out A / O-MBR treatment, thereby reducing the sewage treatment cost, reducing secondary pollution, and improving the sewage treatment efficiency and water purification effect.

[0040] (2) The method for treating landfill leachate of the present invention adopts physical, chemical and biological coupling treatment technology, and has the advantages of low drug consumption, short treatment flow line and small amount of concentrated water produced. The effluent water quality can stably meet the standards of Table 2 in the "Pollutant Control Standards for Municipal Solid Waste Landfills" (GB16889-2008), thereby achieving accurate treatment of organic matter and improving the efficiency of landfill leachate treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The present invention is a process flow chart of the method for treating landfill leachate based on the molecular weight control of organic matter.

[0042] Figure 2 It is a schematic diagram of the device of the landfill leachate treatment method based on the molecular weight control of organic matter of the present invention. DETAILED DESCRIPTION

[0043] Test Method

[0044] COD was determined by the dichromate method (GB 11914-89);

[0045] NH3-N was determined by Nessler's reagent spectrophotometry (HJ 535-2009);

[0046] TN was determined by alkaline potassium persulfate digestion UV spectrophotometry (HJ 636-2012);

[0047] TP was determined by ammonium molybdate spectrophotometry (GB 11893-89).

[0048] Example 1

[0049] A landfill leachate treatment system based on organic matter molecular weight control comprises a pretreatment unit, a deamination membrane unit, an ultrafiltration membrane unit, a Fenton advanced oxidation unit and an A / O-MBR treatment unit; the water outlet of the pretreatment unit is connected to the water inlet of the deamination membrane unit, the water outlet of the deamination membrane unit is connected to the water inlet tank of the ultrafiltration membrane unit, the water inlet tank of the ultrafiltration membrane unit is also connected to the Fenton advanced oxidation unit, the water outlet of the ultrafiltration membrane unit is connected to a water collection tank, the water outlet of the Fenton advanced oxidation unit is connected to the water collection tank, and the water collection tank is connected to the water inlet of the A / O-MBR treatment unit.

[0050] The pretreatment unit is a polypropylene (PP) bag filter with a pore size of 1 micron.

[0051] The membrane assembly of the deamination membrane unit is a hollow fiber membrane made of polytetrafluoroethylene (PTFE), with a diameter of 50 mm, a length of 625 mm, and a membrane area of ​​1.7 m 2 .

[0052] The ultrafiltration membrane unit comprises a filter assembly and a membrane assembly. The filter assembly is a filter whose filter element is PP cotton, and the membrane assembly is a polyethersulfone (PES) membrane with a molecular weight cutoff of 1k Da.

[0053] The Fenton advanced oxidation unit comprises a reactor, a dosing device and a stirrer, and the effective volume of the reactor is 5L.

[0054] The A / O-MBR treatment unit comprises an anoxic pool (A pool) and an aerobic pool (O pool), wherein the A pool and the O pool are connected via a connecting port at the bottom; the A pool is provided with a stirring device to maintain an anoxic state; a perforated pipe is provided at the bottom of the O pool to maintain an aerobic environment by means of aeration, and the O pool is also provided with a microfiltration membrane (MF membrane) assembly, which is immersed in the O pool.

[0055] The total effective volume of the A / O-MBR treatment unit is 6.3 L, the effective volume ratio of the A pool and the O pool is 1:2, and the MF membrane component is a flat membrane with an effective area of ​​0.032 m 2 The pore size is 0.2 microns and the material is polyvinylidene fluoride (PVDF).

[0056] Example 2

[0057] The method for treating landfill leachate using the landfill leachate treatment system described in Example 1 comprises the following steps:

[0058] The water quality indicators of garbage leachate are: COD: 1800mg / L, NH3-N: 1100mg / L, TN: 1400mg / L, TP: 19mg / L.

[0059] (1) Pretreatment: The garbage leachate is treated by a pretreatment unit to obtain effluent from the pretreatment unit;

[0060] The effluent quality indicators of the pretreatment unit are: COD: 1400mg / L, NH3-N: 1100mg / L, TN: 1400mg / L, TP: 12mg / L.

[0061] (2) Deamination membrane treatment: The effluent from the pretreatment unit is adjusted to pH 10.0 using a 2 mol / L NaOH aqueous solution, and then treated by a deamination membrane unit to obtain effluent from the deamination membrane unit;

[0062] The influent water enters the deamination membrane unit through the water inlet on the shell side of the deamination membrane. A sulfuric acid aqueous solution with a sulfuric acid concentration of 0.2 mol / L is used as the absorption liquid. The absorption liquid enters one side of the tube side for circulation. The ammonia nitrogen in the influent water passes through the deamination membrane and is absorbed by the absorption liquid. The effluent water leaves the deamination membrane unit through the shell side outlet. The pH of the sulfuric acid solution is monitored during the deamination membrane treatment process. When the pH is close to 2.0, it is necessary to replace it with a new sulfuric acid solution in time to ensure its acidity.

[0063] The effluent water quality indicators of the deammonification membrane unit are: COD: 1300mg / L, NH3-N: 120mg / L, TN: 150mg / L, TP: 9mg / L, pH: 9.4. The ammonia nitrogen removal rate is as high as 90%, achieving the removal of most of the ammonia nitrogen in the raw liquid.

[0064] (3) Ultrafiltration membrane treatment: Deionized water is used as the inlet water, which enters the filter assembly of the ultrafiltration membrane unit through the water inlet pump for filtration, and then enters the ultrafiltration membrane assembly for ultrafiltration through a pressure pump. The operating pressure is 2.0 to 2.5 bar and the operation is carried out for 20 minutes. After the ultrafiltration device is stable, the inlet water is replaced with 10 L of deamination membrane unit effluent with a pH adjusted to 7.5, and ultrafiltration is performed at a pressure of 2.0 to 2.5 bar. The retentate of the ultrafiltration membrane unit is refluxed to the inlet tank and continuously treated by the ultrafiltration membrane unit until the retention volume ratio is 15%. The device is closed to obtain 8.5 L of ultrafiltration water and 1.5 L of retained concentrate.

[0065] The water quality indicators of ultrafiltration water (molecular weight ≤ 1k) are: COD: 450mg / L, BOD: 160mg / L, NH3-N: 80mg / L, TN: 90mg / L, TP: 6mg / L.

[0066] The water quality indicators of the intercepted concentrate (molecular weight ≥ 1k) are: COD: 5500mg / L, BOD: 370mg / L, NH3-N: 220mg / L, TN: 330mg / L, TP: 23mg / L. The screening of the leachate was achieved, and the relationship between molecular weight and biodegradability was established.

[0067] (4) Fenton advanced oxidation treatment: The pH of the retained concentrate was adjusted to 4.0, and 0.1 L Fe was added to 1.5 L of the retained concentrate. 2+ The concentrations are 1 mol / L ferrous sulfate solution and 0.06L 30% hydrogen peroxide solution (9.79 mol / L). After mixing, react at room temperature for 1 hour in a Fenton advanced oxidation unit with a stirring speed of 150 r / min. The pH is adjusted to 7.5 to terminate the reaction. The iron sludge is removed by static precipitation and filtration to obtain 1L of Fenton effluent.

[0068] The water quality indicators of Fenton effluent are: COD: 1300mg / L, BOD: 500mg / L, NH3-N: 120mg / L, TN: 155mg / L, TP: 0.74mg / L, which effectively improves the biodegradability of components with molecular weight ≥1k.

[0069] (5) A / O-MBR treatment: 1L Fenton effluent was mixed with 8.5L ultrafiltrated water as the inlet water of the A / O-MBR unit. The water quality of the inlet water of the A / O-MBR unit was COD: 560mg / L, NH3-N: 85mg / L, TN: 95mg / L, TP: 4.5mg / L.

[0070] Domestication of sludge: leachate and domestic sewage are mixed in a volume ratio of 1:9 to obtain domestication liquid, and the aerobic activated sludge is domesticated in a sequencing batch mode to obtain an aerobic activated sludge mixed liquid with a suspended solid concentration (MLSS) of 4.5g / L, which is inoculated into the A / O-MBR treatment unit. The A / O-MBR treatment unit is operated, and the influent is the domestication liquid. The flux is controlled at 5LMH and domestication continues. After the effluent COD of the A / O-MBR treatment unit is stabilized, a mixture of leachate and domestic sewage in a volume ratio of 1:6 is used as the influent. At this time, the influent COD is basically consistent with the COD of the aerobic activated sludge mixed liquid. After the COD removal rate is stabilized, the sludge domestication of the A / O-MBR treatment unit is completed.

[0071] The influent of the A / O-MBR unit is treated by the A / O-MBR treatment unit to obtain treated water; the dissolved oxygen in the A pool is maintained at 0.3 mg / L; the dissolved oxygen in the O pool is maintained at 5 mg / L; the reflux ratio is 150%; the MF membrane module is operated at a constant flux; the temperature of the A / O-MBR treatment is 25±2°C.

[0072] The water quality indicators of treated water are: COD: 80mg / L, NH3-N: 8mg / L, TN: 22mg / L, TP: 2mg / L, which can stably meet the standards in Table 2 of the "Pollutant Control Standards for Municipal Solid Waste Landfills" (GB16889-2008).

[0073] Comparative Example 1

[0074] The method for treating landfill leachate using the landfill leachate treatment system described in Example 1 comprises the following steps:

[0075] The water quality indicators of garbage leachate are: COD: 1800mg / L, NH3-N: 1100mg / L, TN: 1400mg / L, TP: 19mg / L.

[0076] (1) Pretreatment: The garbage leachate is treated by a pretreatment unit to obtain effluent from the pretreatment unit;

[0077] The effluent quality indicators of the pretreatment unit are: COD: 1400mg / L, NH3-N: 1100mg / L, TN: 1400mg / L, TP: 12mg / L.

[0078] (2) Deamination membrane treatment: The effluent from the pretreatment unit is adjusted to pH 10.0 using a 2 mol / L NaOH aqueous solution, and then treated by a deamination membrane unit to obtain effluent from the deamination membrane unit;

[0079] The influent water enters the deamination membrane unit through the water inlet on the shell side of the deamination membrane. A sulfuric acid aqueous solution with a sulfuric acid concentration of 0.2 mol / L is used as the absorption liquid. The absorption liquid enters one side of the tube side for circulation. The ammonia nitrogen in the influent water passes through the deamination membrane and is absorbed by the absorption liquid. The effluent water leaves the deamination membrane unit through the shell side outlet. The pH of the sulfuric acid solution is monitored during the deamination membrane treatment process. When the pH is close to 2.0, it is necessary to replace it with a new sulfuric acid solution in time to ensure its acidity.

[0080] The effluent water quality indicators of the deammonification membrane unit are: COD: 1300mg / L, NH3-N: 120mg / L, TN: 150mg / L, TP: 9mg / L, pH: 9.4. The ammonia nitrogen removal rate is as high as 90%, achieving the removal of most of the ammonia nitrogen in the raw liquid.

[0081] (3) Fenton advanced oxidation treatment: The pH of the deammoniation membrane effluent was adjusted to 4.0, and 0.67 L Fe 2+ The concentrations were 1 mol / L ferrous sulfate solution and 0.4 L 30% hydrogen peroxide solution (9.79 mol / L). After mixing, the mixture was reacted at room temperature for 1 h in a Fenton advanced oxidation unit with a stirring speed of 150 r / min. The pH was adjusted to 7.5 to terminate the reaction. The iron sludge was removed by static sedimentation and filtration to obtain 7 L Fenton effluent.

[0082] The water quality indicators of Fenton effluent are: COD: 700mg / L, BOD: 196mg / L, NH3-N: 89mg / L, TN: 105mg / L, TP: 0.60mg / L.

[0083] It can be seen that the effluent after deammoniation in Comparative Example 1 directly enters the Fenton advanced oxidation unit without ultrafiltration treatment. Under the same reaction dosage ratio and reaction time, due to the significant increase in the inlet volume, the diffusion of the reaction system is limited, the capture efficiency of free radicals is reduced, and the mixing is not sufficient, resulting in reduced removal rates of COD, ammonia nitrogen, total nitrogen and total phosphorus, B / C is reduced to 0.28, and the biodegradability is deteriorated; at the same time, the dosage of hydrogen peroxide and ferrous sulfate increased by 6 to 7 times, and the output of iron sludge also increased by nearly 6 times.

[0084] (4) A / O-MBR treatment: The Fenton effluent was used as the inlet water of the A / O-MBR unit. The water quality of the inlet water of the A / O-MBR unit was COD: 700 mg / L, BOD: 196 mg / L, NH3-N: 89 mg / L, TN: 105 mg / L, TP: 0.60 mg / L.

[0085] Domestication of sludge: leachate and domestic sewage are mixed in a volume ratio of 1:9 to obtain domestication liquid, and the aerobic activated sludge is domesticated in a sequencing batch mode to obtain an aerobic activated sludge mixed liquid with a suspended solid concentration (MLSS) of 4.5g / L, which is inoculated into the A / O-MBR treatment unit. The A / O-MBR treatment unit is operated, and the influent is the domestication liquid. The flux is controlled at 5LMH and domestication continues. After the effluent COD of the A / O-MBR treatment unit is stabilized, a mixture of leachate and domestic sewage in a volume ratio of 1:6 is used as the influent. At this time, the influent COD is basically consistent with the COD of the aerobic activated sludge mixed liquid. After the COD removal rate is stabilized, the sludge domestication of the A / O-MBR treatment unit is completed.

[0086] The influent of the A / O-MBR unit is treated by the A / O-MBR treatment unit to obtain treated water; the dissolved oxygen in the A pool is maintained at 0.3 mg / L; the dissolved oxygen in the O pool is maintained at 5 mg / L; the reflux ratio is 150%; the MF membrane module is operated at a constant flux; the temperature of the A / O-MBR treatment is 25±2°C.

[0087] The water quality indicators of treated water are: COD: 280mg / L, NH3-N: 17mg / L, TN: 52mg / L, TP: 0.43mg / L. Among them, COD and total nitrogen failed to stably meet the standards in Table 2 of the "Pollutant Control Standards for Municipal Solid Waste Landfills" (GB16889-2008). This is because the influent water quality is poor, the biodegradability is reduced, the biochemical reaction is affected, and the removal rate is significantly reduced.

[0088] In summary, the method of utilizing the interception effect of ultrafiltration membrane to screen the landfill leachate into different components based on molecular weight and then conducting targeted treatment is necessary. It not only effectively improves the treatment effect of the Fenton unit, reduces operating costs, and reduces secondary pollution, but the improvement of biodegradability is also beneficial to the subsequent biochemical stage reaction, ensuring that the effluent water quality meets the standards.

[0089] The embodiments provided above are not intended to limit the scope of the present invention, and the steps described are not intended to limit the execution order thereof. Those skilled in the art may make obvious improvements to the present invention in combination with existing common knowledge, which also fall within the scope of protection defined by the claims of the present invention.

Claims

1. A landfill leachate treatment system based on organic matter molecular weight control, characterized in that: It includes a pretreatment unit, a deamination membrane unit, an ultrafiltration membrane unit, a Fenton advanced oxidation unit and an A / O-MBR treatment unit; wherein the pretreatment unit, the deamination membrane unit, the ultrafiltration membrane unit, the Fenton advanced oxidation unit and the A / O-MBR treatment unit are connected in sequence, and the ultrafiltration membrane unit is also connected to the A / O-MBR treatment unit.

2. The landfill leachate treatment system according to claim 1, characterized in that: The effluent from the pretreatment unit is passed into the deamination membrane unit, the effluent from the deamination membrane unit is passed into the ultrafiltration membrane unit, the retentate from the ultrafiltration membrane unit is passed into the Fenton advanced oxidation unit, and the effluent from the Fenton advanced oxidation unit and the effluent from the ultrafiltration membrane unit are mixed and passed into the A / O-MBR treatment unit.

3. The landfill leachate treatment system according to claim 1, characterized in that: The pretreatment unit is a polypropylene bag filter with a pore size of 0.9 to 1.1 microns; The membrane assembly of the deamination membrane unit is a hollow fiber membrane; the material of the membrane assembly of the deamination membrane unit is polytetrafluoroethylene; the membrane assembly of the deamination membrane unit has a diameter of 45-55mm, a length of 620-630mm, and a membrane area of ​​1.6-1.8m 2 ; The ultrafiltration membrane unit includes a filter assembly and a membrane assembly; the filter assembly is a filter with a filter element of PP cotton; the membrane assembly of the ultrafiltration membrane unit is a polyethersulfone (PES) membrane; the molecular weight cutoff is 1k Da; The Fenton advanced oxidation unit includes a reactor, a dosing device and an agitator, and the effective volume of the reactor is 5L; The A / O-MBR treatment unit consists of an anoxic tank and an aerobic tank, which are connected through a connecting port at the bottom; the anoxic tank is provided with a stirring device; the bottom of the aerobic tank is provided with a perforated pipe, and the aerobic tank is also provided with a microfiltration membrane assembly, which is immersed in the aerobic tank; The total effective volume of the A / O-MBR treatment unit is 6.2-6.4 L, and the effective volume ratio of the A pool and the O pool is 1:1.5-1:2.5; the MF membrane component is made of polyvinylidene fluoride; a flat membrane is used; the effective area is 0.030-0.034 m 2 ; The pore size is 0.1 to 0.4 microns.

4. The method for treating landfill leachate using the landfill leachate treatment system according to claim 1, characterized in that: Includes steps: (1) Pretreatment: The garbage leachate is treated by a pretreatment unit to obtain effluent from the pretreatment unit; (2) Deamination membrane treatment: The effluent from the pretreatment unit is pH-adjusted and treated by the deamination membrane unit. The pH of the absorption liquid is maintained during the treatment process to obtain the effluent from the deamination membrane unit; (3) Ultrafiltration membrane treatment: The pH of the effluent from the deammoniation membrane unit is adjusted, and the effluent is treated by the ultrafiltration membrane unit, so that the retentate of the ultrafiltration membrane unit is refluxed as the influent of the ultrafiltration membrane unit and continuously treated by the ultrafiltration membrane unit to obtain retentate concentrate and ultrafiltration water; (4) Fenton advanced oxidation treatment: the pH of the retained concentrated solution is adjusted, ferrous sulfate solution and hydrogen peroxide solution are added and mixed to obtain a Fenton reaction solution, which is reacted in a Fenton advanced oxidation unit, the pH is adjusted to terminate the reaction, and the iron sludge is removed to obtain Fenton effluent; (5) A / O-MBR treatment: The Fenton effluent is mixed with the ultrafiltration water and treated in an A / O-MBR treatment unit to obtain treated water.

5. The method for treating landfill leachate according to claim 4, characterized in that: In step (2), the pH of the effluent from the pretreatment unit is adjusted to 10.0±0.1; the absorption liquid is a sulfuric acid aqueous solution; the sulfuric acid concentration of the sulfuric acid aqueous solution is ≥0.2 mol / L; and the pH of the absorption liquid is maintained at <2.

6. The method for treating landfill leachate according to claim 4, characterized in that: In step (3), the pH is adjusted to 7.0-8.0; the influent is ultrafiltered by a pressure pump, and the operating pressure is 2.0-2.5 bar; the retentate obtained by the ultrafiltration membrane unit treatment is returned to the inlet tank and continuously filtered until the retentate volume ratio is 10-15%, and the retentate obtained is the retentate concentrate.

7. The method for treating landfill leachate according to claim 4, characterized in that: In step (4), the pH of the retained concentrated solution is adjusted to 4.0±0.1; the added ferrous sulfate solution and hydrogen peroxide solution are added to n(Fe 2+ ):n(H2O2)=1:5~1:7;Add ferrous sulfate solution to make Fe 2+ The concentration is 0.060-0.068 mol / L; hydrogen peroxide solution is added to make the concentration of hydrogen peroxide in the Fenton reaction solution 0.3-0.5 mol / L; and the pH is adjusted to 7.5-7.8 to terminate the reaction.

8. The method for treating landfill leachate according to claim 4, characterized in that: In step (4), the reaction temperature in the Fenton advanced oxidation unit is 15-35° C., the stirring speed is 100-200 r / min, and the reaction time is 0.5-2 h.

9. The method for treating landfill leachate according to claim 4, characterized in that: In step (5), the dissolved oxygen in the anoxic tank is maintained at 0.2-0.5 mg / L; the dissolved oxygen in the aerobic tank is maintained at 2.0-4.0 mg / L; the reflux ratio is 100%-200%; the MF membrane module is operated at a constant flux; and the temperature of the A / O-MBR treatment is 25±2°C.

10. Use of the garbage leachate treatment system according to any one of claims 1 to 3 or the garbage leachate treatment method according to any one of claims 4 to 9 in sewage treatment.

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