CN113429063A - Landfill leachate treatment system and method - Google Patents

Abstract

The invention discloses a system and a method for treating garbage leakage liquid, wherein the system comprises: (1) the plant protective layer is arranged above the garbage filled in the garbage filling pool and comprises a herbaceous plant protective layer positioned on the ground surface and a woody plant protective layer positioned below the herbaceous plant protective layer, and the woody plant is preferably paulownia elongata; (2) the water seepage structure layer is arranged on the impermeable filter layer which is arranged at the bottom of the refuse landfill pool and inclines towards one side of the refuse landfill pool and is arranged below the filled refuse; (3) the seepage liquid recovery tank is positioned on one side of the refuse landfill tank and communicated with the seepage structure layer, and the bottom and the side wall of the seepage liquid recovery tank are provided with seepage-proof filter layers; (4) the leakage liquid adsorption and purification device is communicated with the leakage liquid recovery tank through a water pipe, and a plurality of working cavities for filling adsorption materials are arranged in the leakage liquid adsorption and purification device. The invention treats the landfill leachate with lower cost and simple process, can effectively prevent secondary pollution and improve the ecological environment of the landfill.

Description

Landfill leachate treatment system and method

Technical Field

The invention belongs to the technical field of environmental protection, and particularly relates to a landfill leachate treatment system and method.

Background

During the temporary storage of municipal solid waste in a refuse station, before the incineration in a refuse incineration plant, leachate containing various harmful components is generated during the refuse composting treatment process, particularly during the landfill treatment process of a refuse dump, and comparatively speaking, the leachate generated during the landfill treatment process of the refuse dump poses the greatest threat to the environment. The reason is that the amount of garbage buried in a garbage site is the largest (even if the garbage is incinerated, the residue after incineration is suitable for utilization and generally needs to be buried), the generated leachate is the largest, the harmful components in the leachate are complex and variable, if the leachate is not treated, the soil, surface water and even underground water around the garbage site can be seriously polluted, and the flow of the surface water and the underground water can cause pollution in a larger range.

In recent years, various methods are proposed in the technical field aiming at the treatment of landfill leachate. At present, the basic treatment methods include "repeated biological treatment by feeding + powdered activated carbon treatment", "nitrification and denitrification treatment", "activated sludge + reverse osmosis treatment", "nanofiltration + powdered activated carbon treatment", "ozone + granular activated carbon treatment", "high-efficiency anaerobic + ammonia stripping + A/O contact oxidation + NF treatment", "ammonia stripping + UBF + SBR + depth treatment", "pretreatment + IOC + MBR + softening + RO + disk-tube reverse osmosis (DTRO) treatment", "photochemical + activated sludge treatment", "Fenton oxidation + UASB treatment", and the like. Based on the principle embodied by these basic methods, many related patent technologies have been derived in the technical field. For example, the invention patent with the patent number of 201410647730.0 discloses a process for resource utilization of biochemical effluent of landfill leachate, which comprises the following steps:

(1) adding hydrated lime calcium hydroxide into leachate biochemical treatment effluent of a waste incineration power plant, stirring and flocculating, wherein the addition amount of the hydrated lime calcium hydroxide is based on the condition that the conductance value of flocculated supernatant reaches the lowest level, and the addition amount of the calcium hydroxide is 2-5 g/L;

(2) carrying out microfiltration filtration on the supernatant after lime flocculation by using a diatomite filter or a ceramic membrane, and adjusting the pH of the obtained filtrate to 6-8 by using hydrochloric acid;

(3) the filtrate after the pH value is adjusted is treated by a reverse osmosis membrane RO, and RO produced water is recycled or directly discharged according to the first-level discharge standard; the RO membrane treatment operating parameters are as follows: the transmembrane pressure is 1.08MPa, the water temperature is 10-30 ℃, and the water yield of the single-stage RO membrane is controlled within 10%;

(4) and (3) stirring and mixing the sediment obtained by lime flocculation in the step (1) and the concentrated water of the RO treatment unit in the step (3), mixing with calcium oxide CaO to prepare Ca (OH) 2 slurry with the mass fraction of 9%, and using the obtained slurry for flue gas desulfurization and deacidification of waste incineration tail gas.

For another example, the invention patent with the patent number 201610085521.0 discloses a landfill leachate ammonia nitrogen removal membrane module and a landfill leachate ammonia nitrogen removal method, wherein the membrane module comprises a shell (9), two ends of the shell (9) are respectively provided with a first end cover (10) and a second end cover (11), hollow membrane filaments (8) are arranged in the shell along the length direction of the shell, the membrane filaments (8) are arranged at intervals, the outer surfaces of the two ends of the membrane filaments are sealed and fixed in the shell (9), the landfill leachate ammonia nitrogen removal membrane module is characterized in that an acid absorption liquid outlet (1) is arranged on the second end cover (11), an acid absorption liquid inlet (3) is arranged on the first end cover (10), two ends of an inner cavity of each membrane filament (8) are respectively communicated with the acid absorption liquid outlet and the acid absorption liquid inlet, a landfill leachate inlet (2) is arranged below the sealing position of the membrane filaments and the shell at the upper end of the shell (9), a landfill leachate ammonia nitrogen outlet (4) is arranged above the sealing position of the shell and the membrane filaments at the lower end of the shell, the membrane silk in the casing and the inner chamber between the sealed department at both ends communicate with rubbish liquid import (2) and rubbish liquid export (4) respectively, are provided with a plurality of hydrophobic holes (13) along the length direction of membrane silk on the membrane silk wall, and the membrane silk inner chamber is linked together through hydrophobic hole (13) and casing inner chamber, is provided with the pressure of the rubbish filtration liquid that rivers anti-deviation device control casing flows at rubbish liquid export (4) end, hydrophobic hole (13) are the slot hole, and its length direction sets up along the length direction of membrane silk, hydrophobic hole (13) are provided with flange (14) to turning up, rivers anti-deviation device is connected in proper order by motorised valve (5), pressure sensor (6) and electrical control valve (7) and is constituteed, and electrical control valve is connected with the rubbish liquid outlet pipe by motorised valve one end.

The prior art is helpful to reduce the harm of the landfill leachate to the environment, but also has some technical defects, for example, some treatment methods generate new harmful substances while reducing the harmful components in the leachate, and improper treatment can cause secondary pollution, for example, some treatment methods are only suitable for leachate with simple harmful components and are not suitable for leachate with complex harmful components, and for example, some treatment methods are too complex in process and too high in treatment cost.

Disclosure of Invention

The invention aims to treat the landfill leachate with lower cost and simpler process, effectively prevent secondary pollution and overcome the defects of the prior art.

In order to realize the purpose of the invention, the invention adopts the following technical scheme:

a waste leachate treatment system, comprising:

(1) a plant protective layer arranged on the garbage filled in the garbage filling pool; the plant protective layer comprises a herbaceous plant protective layer positioned on the ground surface and a woody plant protective layer positioned below the herbaceous plant protective layer; the herbaceous plant protective layer is a soil layer for planting herbaceous plants, and the woody plant protective layer is a soil layer for planting woody plants; by the following, it is meant that the root system of the woody plant is located below the root system of the herbaceous plant;

(2) the top surface of the seepage-proofing filter layer is inclined towards one side of the refuse landfill pool;

(3) a water seepage structure layer arranged above the seepage-proofing filter layer at the bottom of the refuse landfill pool and below the filled refuse;

(4) the seepage liquid recovery tank is arranged on one side of the refuse landfill and is communicated with the seepage structure layer, and the bottom and the side wall of the seepage liquid recovery tank are also provided with seepage-proof filter layers;

(5) and the leakage liquid adsorption and purification device is communicated with the leakage liquid recovery tank through a water pipe, and a working cavity for filling an adsorption material is arranged in the leakage liquid adsorption and purification device.

The technical route of the invention is as follows: the landfill process of the garbage and the treatment process of the penetrating fluid are considered as a general invention concept, and the treatment of the garbage penetrating fluid and the improvement of the ecological environment of the garbage landfill site are considered, not only the penetrating fluid generated by the garbage which is completely filled is treated. On the basis of the technical scheme, the invention can be additionally provided with the following technical means so as to better or more specifically realize the purpose of the invention:

the water seepage structure layer is a parallel multi-pipe body formed by water pipes which are made of pervious concrete and have semicircular cross sections in parallel. In the invention, the water seepage structure layer has two main functions: the first one, play a supporting role to the rubbish that its upper portion landfills, and the second one, for the penetrant that the said rubbish formed provides the channel that flows into the seepage liquid recovery pond.

Furthermore, the soil thickness of the herbaceous plant protective layer is 40 centimeters, and the soil of the woody plant protective layer is sandy soil, and the thickness of the woody plant protective layer is 50 centimeters.

Further, the woody plant protective layer is planted with a plant which is saline-alkali tolerant, preferably paulownia elongata.

Furthermore, a plurality of woody plant nutrition conveying holes which are vertically downward, have different depths and are arranged in a ring shape are arranged around the tree pit at the periphery of the tree pit for planting the woody plant before or at the same time of planting the woody plant, the minimum depth of the conveying holes is 60 cm, and the maximum depth is 500 cm; a rod-shaped object with the shape and the length matched with the shape and the depth of the conveying hole is inserted into the conveying hole, and the outlet of the woody plant nutrition conveying hole is sealed, so that the conveying hole is prevented from being blocked; when nutrition needs to be delivered to the root system of the woody plant, the rod-shaped object is pulled out, and the nutrient components are delivered to the bottom of the delivery hole.

Furthermore, the water inlet of the leakage liquid adsorption and purification device is positioned at the bottom or the lower part of the side surface of the leakage liquid adsorption and purification device, the water outlet of the leakage liquid adsorption and purification device is positioned at the top or the upper part of the side surface of the leakage liquid adsorption and purification device, four detachable filter plates are arranged in the leakage liquid adsorption and purification device, and the internal space of the leakage liquid adsorption and purification device is divided into five working cavities for filling adsorption materials by the four detachable filter plates.

Further, the garbage leakage liquid treatment system also comprises an MBR membrane-bioreactor communicated with the leakage liquid adsorption and purification device through a water pipe.

Further, the garbage leakage liquid treatment system also comprises a biogas conduit which penetrates through the plant protection layer and enters the filled garbage.

The invention also provides a method for treating the garbage leachate by taking the garbage leachate treatment system as hardware, which comprises the following steps:

step 1, crushing garbage to be buried, adding lime powder (hydrated lime powder or quicklime powder) into the garbage, fully mixing the lime powder and the garbage to form a garbage-lime mixture, wherein the adding amount of the lime powder is determined according to the standard that the PH value of a saturated aqueous solution of the garbage-lime mixture is 8-9;

step 2, burying the garbage-lime mixture into a garbage burying pool, and compacting;

step 3, paving a woody plant protective layer consisting of soil on the filled garbage-lime mixture;

step 4, laying a herbaceous plant protective layer consisting of soil on the woody plant protective layer;

step 5, arranging a biogas conduit which penetrates through the herbaceous plant protective layer and the woody plant protective layer and enters the garbage-lime mixture;

step 6, digging a tree pit, arranging a plurality of woody plant nutrition conveying holes which are vertically downward, have different depths and are arranged in a ring shape around the tree pit, inserting rod-shaped objects with the shapes and the lengths matched with the shapes and the depths into the woody plant nutrition conveying holes, and sealing the outlets of the woody plant nutrition conveying holes; the dug tree pits penetrate through the herbaceous plant protection layer to reach the bottom of the woody plant protection layer, and the distance between every two adjacent tree pits is 2 meters; after the tree pit is dug, repeatedly drilling the tree pit into the garbage-lime mixture below the tree pit by using a drill bit of a drilling machine, wherein the drilling depth is 3-5 m, and the function of the drilling machine is to locally loosen the compacted garbage-lime mixture so as to ensure that the root system of a subsequently cultivated woody plant is deeply inserted into the garbage-lime mixture;

step 7, planting herbaceous plants on the surfaces of the herbaceous plant protective layers, planting saline-alkali-resistant woody plants (preferably paulownia elongata) in tree pits, and transplanting partial woody plants along with the growth of the woody plants so as to enlarge the space between the adjacent woody plants;

step 8, after the leakage liquid in the leakage liquid recovery pool reaches a certain amount, determining whether to disinfect the leakage liquid according to the detection result of harmful bacteria in the leakage liquid, adjusting the type of an adsorption material in the leakage liquid adsorption and purification device according to the type and content of heavy metal ions in the leakage liquid, and pumping the leakage liquid to the leakage liquid adsorption and purification device by using a water pump;

and 9, if the herbaceous plants and the woody plants need watering, watering by using the water treated by the leakage liquid adsorption and purification device, and if the herbaceous plants and the woody plants do not need watering, pumping the water treated by the leakage liquid adsorption and purification device into the MBR membrane-bioreactor, and performing deep purification treatment on the water treated by the leakage liquid adsorption and purification device by using the MBR membrane-bioreactor.

Further, when step 7 is executed, activated carbon particles, zeolite particles, diatomite particles, montmorillonite particles and sepiolite particles are respectively filled in the five working cavities of the leakage liquid adsorption and purification device.

In general, the invention treats the landfill leachate with lower cost and simple process, can effectively prevent secondary pollution and improve the ecological environment of the landfill. The following beneficial effects of the invention are specifically described by combining the technical means of planting lime powder and paulownia elongata and the like:

1. the lime powder (hydrated lime powder or quicklime powder) is fully mixed with the garbage and absorbs water, so that most harmful bacteria in the garbage can be killed, and the lime powder can react with lipid substances in the garbage to generate calcium lipoids which are insoluble or slightly soluble in water, so that the toxicity and the viscosity of garbage penetrating fluid are reduced, and the subsequent treatment of the penetrating fluid is facilitated.

2. After the saline-alkali tolerant woody plant grows for a period of time, the root system of the woody plant breaks through the bottom surface of the protective layer of the woody plant and penetrates into the garbage-lime mixture, and absorbs water and other components in the garbage-lime mixture to promote the degradation of the garbage-lime mixture. It should be particularly emphasized that paulownia has the advantage of growing fast compared to other saline-alkali tolerant woody plants such as elm, koelreuteria paniculata, mulberry, honey locust, and silk floss wood, while paulownia elongata trunk, has stronger saline-alkali tolerance, more developed root system, and has the advantage that the root system mainly grows to the periphery and deep in soil with less than 40 cm on the ground surface (the depth of the main root can reach more than three meters, and the fine root at the front end of the main root can even extend to more than five meters underground), and the trunk height and the branch are sparse, so that the paulownia paniculata has almost no influence on the herbaceous lighting of the plants on the ground surface. The advantages also make the paulownia elongata play an important role in the three-pest fight of treating sand storm, salt and alkali and waterlogging by the people of Lancet with the caustic college of focus and position. In addition, the paulownia elongata also has certain capacity of tolerating methane, and is suitable for improving the ecological environment of a refuse landfill. Along with the extension of the root system in the garbage-lime mixture, the paulownia elongata can not only absorb more water and other components (including beneficial and harmful components) in the garbage-lime mixture, but also a large amount of microorganisms capable of degrading the harmful components in the garbage can take the root system as a hotbed to deeply penetrate into the garbage-lime mixture, and in addition, beneficial substances secreted by the root system, such as tartaric acid and the like, can further promote the degradation of the garbage.

3. The water seepage structure layer adopts a parallel multi-tube structure, which is beneficial to quickly discharging garbage percolate and avoids overlarge humidity of a garbage-lime mixture, thereby creating an environment beneficial to the growth of woody plants, especially the paulownia elongata (the paulownia elongata has stronger drought and waterlogging resistance, but the root system of the paulownia elongata is not well soaked in water for a long time). In addition, the herbaceous plant protective layer is favorable for relieving the rainwater infiltration rate, is favorable for the growth of woody plants such as paulownia elongata and the like, and can generate obvious economic benefit and ecological benefit after the woody plants such as paulownia elongata and the like are made into wood.

4. The absorption of harmful ingredients in the landfill leachate by different absorption materials is selective (at least has tendentiousness), and the leakage liquid absorption and purification device can more fully absorb the harmful ingredients in the landfill leachate by arranging a structural design that the working cavities are used for filling different absorption materials, and the water inlet is arranged at the lower part and the water outlet is arranged at the upper part.

Drawings

Fig. 1 is a schematic longitudinal sectional view of a landfill tank and a leakage liquid recovery tank in embodiment 1 of the present invention;

fig. 2 is a schematic cross-sectional view of a water permeable structure layer in example 1 of the present invention;

FIG. 3 is a schematic longitudinal sectional view showing a percolating liquid adsorbing and purifying apparatus in example 1 of the present invention;

FIG. 4 is a schematic top view of the structure of embodiment 1 of the present invention;

fig. 5 is a schematic view of a horizontal cross-sectional partial structure of a landfill pool in embodiment 2 of the present invention.

In the figure:

1-refuse landfill; 101-herbaceous plant protective layer; 102-woody plant protective layer; 103-refuse-lime mixture; 104-impermeable filtration layer on the side surface of the landfill pool; 105-a water-permeable structure layer; 106-impermeable filtration layer at the bottom of the landfill pool; 107-biogas conduit; 1 a-Paulownia elongata area with planting time of up to seven years; 1 b-the area of paulownia elongata with planting time of six years; 1 c-area of paulownia elongata with planting time of up to five years; 1 d-area of paulownia elongata with planting time of up to four years; 1 e-the area of paulownia elongata with planting time of up to three years; 1 f-area of paulownia elongata with planting time of two years; 1 g-area of paulownia elongata with planting time one year old; 1 h-the paulownia elongata area of a newly planted tree in the same year;

2-leachate recovery tank; 201-leachate recovery tank outlet pipe;

3-leakage liquid adsorption purification device; 301-water inlet pipe of leakage liquid adsorption purification device; 302-water outlet pipe of the leakage liquid adsorption purification device; 303 — first filter plate; 304-second filter plate; 305-third Filter plate; 306-third Filter plate;

4-MBR membrane-bioreactor;

5-tree pit; 501-woody plant nutrient delivery pores located in the first circle of layers; 502-woody plant nutrient delivery pores located in the second circle of layers.

Detailed Description

In order to facilitate the technical solutions of the present invention to be better understood by those skilled in the art, two embodiments embodying the structural features of the landfill leachate treatment system of the present invention are described below with reference to the accompanying drawings:

example 1

As shown in fig. 1, a garbage leachate treatment system includes:

(1) the plant protection layer is arranged above the garbage-lime mixture 103 filled in the garbage landfill pool 1 and comprises a herbaceous plant protection layer 101 positioned on the ground surface and a woody plant protection layer 102 positioned below the herbaceous plant protection layer 101; the herbaceous plant protective layer is a soil layer for planting herbaceous plants, and the woody plant protective layer is a soil layer for planting woody plants; the term "root system of woody plant" means that the root system of woody plant is located under the root system of herbaceous plant (in this embodiment, woody plant is paulownia elongata, which includes the broad sense of paulownia elongata, which means paulownia elongata native to the county of Lanceo, and the narrow sense of paulownia elongata is preferable, the soil for planting paulownia elongata is sandy soil, and herbaceous plant is not limited in kind as long as it is suitable for local environment and flourish growth.

(2) The anti-seepage filtering layer 106 is arranged at the bottom of the refuse landfill pool 1 and inclines towards one side of the refuse landfill pool 1; a side anti-seepage filtering layer 104 is also arranged on the contact surface of the side surface of the refuse landfill tank 1 and the filled refuse-lime mixture 103.

(3) And a water seepage structure layer 105 arranged above the seepage-proofing filter layer 106 at the bottom of the refuse landfill pool 1 and below the filled refuse-lime mixture 103.

(4) And the seepage liquid recovery tank 2 is positioned on one side of the refuse landfill tank 1 and is communicated with the seepage structure layer 105, the bottom and the side wall of the seepage liquid recovery tank 2 are provided with seepage-proof filter layers, and the seepage-proof filter layer at the bottom of the seepage liquid recovery tank is connected with the seepage-proof filter layer 106 at the bottom of the refuse landfill tank 1 into a whole.

(5) Through the herbal protection layer 101 and the woody plant protection layer 102 into the biogas conduit 107 in the waste-lime mixture 103.

As shown in fig. 2, the water permeable structure layer 105 is a parallel multi-pipe body formed by juxtaposing water pipes made of water permeable concrete and having a semicircular cross section.

As shown in fig. 3 and 4, the garbage leachate treatment system of the present invention further includes a leachate absorption and purification apparatus 3 connected to the leachate recovery tank 2 through a water pipe (not shown), and an MBR membrane-bioreactor 4 (MBR membrane-bioreactor and the above-mentioned impermeable layer) connected to the leachate absorption and purification apparatus 3 through a water pipe (not shown) and constructed by using the existing equipment or materials in the prior art, for example, concrete with an impermeable grade greater than or equal to P6 grade.

As shown in fig. 3, in the present embodiment, the water inlet 301 of the leakage fluid adsorption and purification device 3 is located at the bottom thereof, the water outlet 302 thereof is located at the top thereof, and four detachable filter plates, that is, a first filter plate 303, a second filter plate 304, a third filter plate 305, and a fourth filter plate 306, are arranged inside the leakage fluid adsorption and purification device, and the four detachable filter plates divide the internal space thereof into five working chambers for filling with the adsorption material.

As shown in fig. 4, in the present embodiment, the woody plant protective layer 102 is divided into 8 regions connected to each other, that is, an paulownia elongata region 1a planted for 7 years, an paulownia elongata region 1b planted for six years, an paulownia elongata region 1c planted for five years, an paulownia elongata region 1d planted for four years, an paulownia elongata region 1e planted for three years, an paulownia elongata region 1f planted for two years, an paulownia elongata region 1g planted for one year, and an paulownia elongata region 1h newly planted in the same year. For the area of the paulownia elongata (the height of a crown can be about 20 meters generally, the height of a trunk can be about 12 meters generally, and the diameter at breast height can be about 35 centimeters generally) planted for seven years, if the area needs to be continuously used for landfill, a refuse landfill pool is dug again after the trees are felled, the toxicity of the dug-out 'refuse' mixture is greatly reduced, the dug-out 'refuse' mixture can be used as soil after detection or further treatment, and if the area does not need to be used for landfill, the area of the paulownia elongata can be reserved, so that the ecological benefit of the area can be better realized.

Example 2

The basic structural features of example 2 are identical to those of example 1, except that, as shown in fig. 2, a plurality of woody plant nutrition delivering holes are formed in a circle vertically downward and in different depths around a tree pit 5 for planting woody plants in a landfill 1 before or at the same time of planting the woody plants. In this embodiment, the total number of woody plant nutrient delivery pores is 16, and the woody plant nutrient delivery pores are divided into two circle layers, namely 8 woody plant nutrient delivery pores 501 located in the first circle layer and 8 woody plant nutrient delivery pores 502 located in the second circle layer. The distance from the 8 woody plant nutrition delivery holes 501 of the first circle layer to the edge of the tree pit 5 is 40 cm, and the distance from the 8 woody plant nutrition delivery holes 502 of the second circle layer to the edge of the tree pit 5 is 80 cm (more woody plant nutrition delivery hole circle layers can be arranged according to different planning time limits). The minimum depth of the woody plant nutrition delivery holes 501 and 502 is 60 cm, and the maximum depth is 500 cm; the woody plant nutrition conveying holes 501 and 502 are internally inserted with rod-shaped objects with the shapes and the lengths matched with the shapes and the depths, and the outlets of the woody plant nutrition conveying holes 501 and 502 are sealed, so that the effects of preventing the conveying holes from being blocked are achieved (in the embodiment, the horizontal sections of the woody plant nutrition conveying holes 501 and 502 are both circular and have the diameter of 3 cm, and the rod-shaped objects are moso bamboos); when nutrition needs to be delivered to the root system of the woody plant, the rod-shaped object is pulled out, and nutrient components (such as phosphate fertilizer, potash fertilizer and the like) can be delivered to the bottom of the delivery hole of the woody plant. This embodiment is before planting woody plant or simultaneously, sets up woody plant nutrition delivery hole 501, 502 promptly, helps protecting woody plant's root system, avoids punching afterwards to hurt woody plant's root system. In addition, when the root system of the woody plant has diseases and insect pests (generally, the diseases and insect pests can be judged according to the growth vigor of the leaves), corresponding medicines can also be conveyed to the root system of the woody plant through the nutrition conveying holes 501 and 502 of the woody plant.

Two embodiments characterizing the structure of the present invention are described above with reference to the accompanying drawings, and one embodiment characterizing the method of the present invention is further described below, which includes the following steps:

step 1, crushing garbage to be buried, randomly extracting 100 parts of garbage samples with the same mass, respectively placing the garbage samples into water, measuring the pH value of each garbage sample after the concentration of an aqueous solution is saturated, calculating the pH value of a saturated aqueous solution of the garbage according to an arithmetic mean value, then adding slaked lime powder into the garbage, fully mixing the garbage and the slaked lime powder to form a garbage-lime mixture, wherein the adding amount of the slaked lime powder is determined according to the standard that the pH value of the saturated aqueous solution of the garbage-lime mixture is 8-9.

And 2, burying the garbage-lime mixture into a garbage burying pool, and compacting. In this example, the thickness of the landfill-lime mixture is 6 to 8 meters. (since the impermeable filter layer 106 and the permeable structure layer 105 at the bottom of the landfill pool incline to one side, the thickness of the landfill-lime mixture increases from small to large.)

And 3, paving a woody plant protective layer consisting of soil (preferably sand-containing soil) on the filled garbage-lime mixture.

And 4, paving a herbaceous plant protective layer consisting of soil on the woody plant protective layer.

And 5, arranging a biogas guide pipe which penetrates through the herbaceous plant protective layer and the woody plant protective layer and enters the garbage-lime mixture.

And 6, digging tree pits, wherein the dug tree pits penetrate through the herbaceous plant protection layer to reach the bottom of the woody plant protection layer, and the distance between every two adjacent tree pits is 2 meters. After the tree pit is dug, a drill bit of a drilling machine is used for repeatedly drilling the garbage-lime mixture below the tree pit (including the inclined lower side), the drilling depth is 3-5 meters, the effect of the drilling is not to leave a drilled hole in the garbage-lime mixture, but the compacted garbage-lime mixture is locally loosened so as to ensure that the root system of a subsequently cultivated woody plant is deeply inserted into the garbage-lime mixture, meanwhile, a plurality of woody plant nutrition conveying holes which are vertically downward and have different depths and are arranged in a ring shape are arranged around the tree pit, a rod-shaped object with the shape and the length matched with the shape and the depth is inserted into the woody plant nutrition conveying holes, and the outlet of the woody plant nutrition conveying holes is sealed.

And 7, planting herbaceous plants on the surfaces of the herbaceous plant protective layers, and planting paulownia elongata in tree pits, preferably paulownia elongata with main roots, which is cultured in the area of Lancoo county in Henan province. Transplanting is performed on part of paulownia elongata as the paulownia elongata grows so as to enlarge the space between adjacent paulownia elongata.

And 8, after the leakage liquid in the leakage liquid recovery tank reaches a certain amount (for example, after the capacity of the leakage liquid recovery tank reaches one fourth), determining whether to perform disinfection treatment on the leakage liquid (for example, when escherichia coli exceeds the standard, bleaching powder treatment can be performed) according to the detection result of harmful bacteria such as escherichia coli and the like in the leakage liquid, adjusting the type of an adsorption material in the leakage liquid adsorption purification device according to the type and content of heavy metal ions in the leakage liquid, and pumping the leakage liquid into the leakage liquid adsorption purification device by using a water pump for treatment. If the heavy metal ions are of various types (such as copper, lead, zinc, cadmium, manganese, chromium and the like) and the content is obviously higher than the emission standard, the five working chambers of the leakage liquid adsorption and purification device can be respectively filled with activated carbon particles, zeolite particles, diatomite particles, montmorillonite particles and sepiolite particles.

And 9, if the herbaceous plants and the woody plants need watering, watering by using the water treated by the leakage liquid adsorption and purification device, and if the herbaceous plants and the woody plants do not need watering, pumping the water treated by the leakage liquid adsorption and purification device into the MBR membrane-bioreactor, and performing deep purification treatment on the water treated by the leakage liquid adsorption and purification device by using the MBR membrane-bioreactor.

It should be noted that quicklime powder may be used instead of slaked lime powder when step 1 is performed. Since the quicklime reacts with water to produce slaked lime, the technical effects of both are generally the same. However, there is a slight difference that quicklime releases a large amount of heat when it is in contact with water, which is disadvantageous to the growth of the root system of woody plants such as paulownia elongata, and therefore, in the case of treating garbage with quicklime, the time for planting the woody plants should be appropriately delayed.

It is particularly emphasized that saturated aqueous solutions of waste, having a PH of greater than 9, even greater than 10, are generally at a PH of less than 7.5, even lower, but without excluding waste of particular origin, and in such cases where the invention is practiced, it is not advisable to treat the waste with direct lime. Otherwise, the growth of paulownia elongata or other saline-alkali tolerant plants is not facilitated. For this purpose, solid tartaric acid may be added to the waste, the PH of a saturated aqueous solution of the waste-solid tartaric acid mixture being controlled between 8 and 9. Of course, the waste with a high pH value and the waste with a low pH value may be mixed and then treated with lime.

It should be noted that, in order to verify the technical means of planting with slaked lime and paulownia to treat landfill garbage, so as to reduce the toxicity and viscosity of the garbage penetrating fluid and facilitate the technical effect of the subsequent treatment of the penetrating fluid, the research and development team also performs the following experimental research:

the garbage is crushed and fully stirred and then is divided into two parts, one part is placed in a garbage landfill pool serving as a control group (the thickness of garbage landfill is 1 meter), the other part is fully mixed with hydrated lime and then is placed in a garbage landfill pool serving as a research group (the thickness of garbage landfill is also 1 meter), paulownia elongata and herbaceous plants are planted according to the method, samples are respectively taken from percolate generated by the control group and the experimental group when the growth period of the paulownia elongata is one year and two years, and data obtained after detection are as follows: (wherein, the PH value is dimensionless, the chroma is multiple, the faecal coliform is CFU/L, and the others are mg/L)

Detecting items	First sampling of control group	Second sampling of control group	First sampling of the experimental group	Second sampling of the experimental group
					pH value	7.31	7.32	8.9	8.1
Color intensity	256	250	66	42
					Chemical Oxygen Demand (COD)	4.86×10³	4.77×10³	7.78×10²	4.95×10²
Biochemical oxygen demand in five days	1.78×10³	1.71×10³	2.77×10²	1.76×10²
					Suspended matter	7.2×10²	6.9×10²	2.13×10²	1.39×10²
Ammonia nitrogen	2.75×10³	2.83×10³	8.2×10²	5.2×10²
					Total phosphorus	73.5	55.4	19.1	13.2
Total nitrogen	2.92×10³	3.06×10³	7.33×10²	5.11×10²
					Faecal coliform (CFU/L)	3.0×106	5.6×106	3.81×10²	4.96×10²
Hexavalent chromium	0.004	0.004	0．0018	0．0013
					Total chromium	4.02	3.59	1.89	1.37
Total mercury	0.00279	0.00294	0.00078	0.00046
					Total arsenic	0.3476	0.3159	0.1215	0.0813
Total cadmium	0.005	0.005	0.0018	0.0012
					Total lead	0.007	0.007	0.003	0.002

From the data, the technical means of planting the slaked lime and the paulownia elongata can effectively reduce the harmful components in the landfill leachate, create favorable conditions for the subsequent treatment of the landfill leachate, and besides the faecal coliform flora, the harmful substances are in a trend of obviously reducing on the whole along with the growth of the paulownia elongata.

It should be noted that although paulownia elongata has many advantages, the growth of paulownia elongata is greatly limited in regions with extreme temperatures below-20 degrees celsius, and in alpine mountainous regions. Therefore, when the method is implemented in the region, other tree species which are suitable for the climate of the region and have strong saline-alkali tolerance need to be selected.

Claims (10)

1. A waste leachate treatment system, comprising:

(1) a plant protective layer arranged on the garbage filled in the garbage filling pool; the plant protective layer comprises a herbaceous plant protective layer positioned on the ground surface and a woody plant protective layer positioned below the herbaceous plant protective layer; the herbaceous plant protective layer is a soil layer for planting herbaceous plants, and the woody plant protective layer is a soil layer for planting woody plants; by the following, it is meant that the root system of the woody plant is located below the root system of the herbaceous plant;

(2) the top surface of the seepage-proofing filter layer is inclined towards one side of the refuse landfill pool;

(3) a water seepage structure layer arranged above the seepage-proofing filter layer at the bottom of the refuse landfill pool and below the filled refuse;

(4) the seepage liquid recovery tank is arranged on one side of the refuse landfill and is communicated with the seepage structure layer, and the bottom and the side wall of the seepage liquid recovery tank are also provided with seepage-proof filter layers;

(5) and the leakage liquid adsorption and purification device is communicated with the leakage liquid recovery tank through a water pipe, and a working cavity for filling an adsorption material is arranged in the leakage liquid adsorption and purification device.

2. The waste leachate treatment system of claim 1, wherein: the water seepage structure layer is a parallel multi-pipe body formed by water pipes which are made of pervious concrete and have semicircular cross sections in parallel.

3. The waste leachate treatment system of claim 1, wherein: the soil thickness of herbaceous plant inoxidizing coating is 40 centimetres, the soil of woody plant inoxidizing coating is the soil that contains sand, and its thickness is 50 centimetres.

4. The waste leachate treatment system of claim 1, wherein: the woody plant protective layer is planted with saline-alkali tolerant woody plants.

5. The waste leachate treatment system of claim 4, wherein: the woody plant is paulownia elongata.

6. The waste leachate treatment system of claim 1, wherein: arranging a plurality of woody plant nutrition conveying holes which are vertically downward, have different depths and are arranged in a ring shape around a tree pit at the periphery of the tree pit for planting the woody plant before or at the same time of planting the woody plant, wherein the minimum depth of the conveying holes is 60 cm, and the maximum depth is 500 cm; a rod-shaped object with the shape and the length matched with the shape and the depth of the conveying hole is inserted into the conveying hole, and the outlet of the woody plant nutrition conveying hole is sealed, so that the conveying hole is prevented from being blocked; when nutrition needs to be delivered to the root system of the woody plant, the rod-shaped object is pulled out, and the nutrient components are delivered to the bottom of the delivery hole.

7. The refuse leachate treatment system according to any of claims 1 to 6, wherein: the water inlet of the leakage liquid adsorption and purification device is positioned at the lower part of the bottom or the side surface of the leakage liquid adsorption and purification device, the water outlet of the leakage liquid adsorption and purification device is positioned at the upper part of the top or the side surface of the leakage liquid adsorption and purification device, four detachable filter plates are arranged in the leakage liquid adsorption and purification device, and the internal space of the leakage liquid adsorption and purification device is divided into five working cavities for filling adsorption materials by the four detachable filter plates.

8. The refuse leachate treatment system according to any of claims 1 to 6, wherein: the garbage leakage liquid treatment system also comprises an MBR membrane-bioreactor communicated with the leakage liquid adsorption and purification device through a water pipe.

9. A method of treating a landfill permeate, comprising the steps of:

step 1, crushing garbage to be buried, adding lime powder into the garbage, and fully mixing the lime powder and the garbage to form a garbage-lime mixture, wherein the adding amount of the lime powder is determined according to the standard that the PH value of a saturated aqueous solution of the garbage-lime mixture is 8-9;

step 2, burying the garbage-lime mixture into a garbage burying pool, and compacting;

step 3, paving a woody plant protective layer consisting of soil on the filled garbage-lime mixture;

step 4, laying a herbaceous plant protective layer consisting of soil on the woody plant protective layer;

step 5, arranging a biogas conduit which penetrates through the herbaceous plant protective layer and the woody plant protective layer and enters the garbage-lime mixture;

step 6, digging a tree pit, arranging a plurality of woody plant nutrition conveying holes which are vertically downward, have different depths and are arranged in a ring shape around the tree pit, inserting rod-shaped objects with the shapes and the lengths matched with the shapes and the depths into the woody plant nutrition conveying holes, and sealing the outlets of the woody plant nutrition conveying holes; the dug tree pits penetrate through the herbaceous plant protection layer to reach the bottom of the woody plant protection layer, and the distance between every two adjacent tree pits is 2 meters; after the tree pit is dug, repeatedly drilling the tree pit into the garbage-lime mixture below the tree pit by using a drill bit of a drilling machine, wherein the drilling depth is 3-5 m, and the function of the drilling machine is to locally loosen the compacted garbage-lime mixture so as to ensure that the root system of a subsequently cultivated woody plant is deeply inserted into the garbage-lime mixture;

step 7, planting herbaceous plants on the surfaces of the herbaceous plant protective layers, planting saline-alkali-resistant woody plants in the tree pits, and transplanting partial woody plants along with the growth of the woody plants so as to enlarge the space between the adjacent woody plants;

step 8, after the leakage liquid in the leakage liquid recovery pool reaches a certain amount, determining whether to disinfect the leakage liquid according to the detection result of harmful bacteria in the leakage liquid, adjusting the type of an adsorption material in the leakage liquid adsorption and purification device according to the type and content of heavy metal ions in the leakage liquid, and pumping the leakage liquid to the leakage liquid adsorption and purification device by using a water pump;

and 9, if the herbaceous plants and the woody plants need watering, watering by using the water treated by the leakage liquid adsorption and purification device, and if the herbaceous plants and the woody plants do not need watering, pumping the water treated by the leakage liquid adsorption and purification device into the MBR membrane-bioreactor, and performing deep purification treatment on the water treated by the leakage liquid adsorption and purification device by using the MBR membrane-bioreactor.

10. A process for treating a landfill permeate according to claim 9, wherein: and 7, respectively filling activated carbon particles, zeolite particles, diatomite particles, montmorillonite particles and sepiolite particles in the five working cavities of the leakage liquid adsorption and purification device.

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