CN213012208U

CN213012208U - Plant solid-phase biochar multistage root-hole wetland system for removing nitrogen pollution of water body

Info

Publication number: CN213012208U
Application number: CN202021310857.0U
Authority: CN
Inventors: 古小治; 陈开宁; 马书占
Original assignee: Nanjing Institute of Geography and Limnology of CAS
Current assignee: Nanjing Institute of Geography and Limnology of CAS
Priority date: 2020-07-07
Filing date: 2020-07-07
Publication date: 2021-04-20
Anticipated expiration: 2030-07-07

Abstract

The utility model provides a get rid of multistage root hole wetland system of plant solid phase biochar of water nitrogen pollution, including the inner ring and the outer loop filtration system that the cover was established, the inner ring and the outer loop filtration system are the annular earth pillar that the protection network was encircleed, and the intussuseption is filled with matrix and plant solid phase biochar to the plant has the plant, is provided with nanometer aeration pipe in the matrix, and the inner ring is higher than the outer loop, and plant solid phase biochar is the biochar material through modifier activation, and the modifier includes clay mineral and heat insulating agent. Firstly, sewage enters an inner ring core area, and the artificial wetland system is filled by using the biochar as an annular soil column matrix material, so that the denitrification rate is improved while effective carbon source supply is not reduced. The problem of communication of hydraulic flow paths is solved by using the water level difference, and the ecological filtration of water amount is realized by the step water level difference. Utilize the utility model discloses can reach the water aquatic plant discarded object resourceization high efficiency and the water and go on the purpose of administering in step with a large amount of nitrogen form pollutants of surplus.

Description

Plant solid-phase biochar multistage root-hole wetland system for removing nitrogen pollution of water body

Technical Field

The utility model belongs to the technical field of the environmental protection, a utilize multistage root hole wetland system of enhancement mode plant solid phase biological carbon who lasts high-efficient effective biological carbon who supplies with is related to. In particular to a wetland system constructed by utilizing carbon source materials in the enhanced water denitrification and denitrification technology of lakeside and riparian zone wetlands or artificial vertical flow wetlands.

Background

Biological denitrification refers to a process of converting nitrate nitrogen into nitrogen gas by denitrification in the presence of denitrifying bacteria. The denitrification process of the water body, in particular the denitrification and denitrification of the vertical flow artificial wetland is one of the main processes for removing the nitrogen. Sufficient electron donors are needed to ensure the smooth operation of denitrification, and the organic matters in the sewage can provide the electron donors for denitrifying bacteria. In the actual wetland denitrification process, the COD/TN is generally required to be 4-15 to ensure that denitrification can be smoothly carried out, the C/N in general sewage is less than 3, obviously, when tail water is subjected to deep denitrification, a carbon source is insufficient, and a carbon source needs to be continuously added. Therefore, in the deep denitrification process of urban reclaimed water, research on the supply mode of an external carbon source (electron donor) becomes a key problem which needs to be solved urgently at present.

If the soluble carbon source is directly added, the problems of insufficient denitrification of the carbon source, waste and secondary pollution caused by excessive carbon source and the like are easily caused along with the fluctuation of the concentration of the nitrate in the treated water, the difficulty in controlling the adding amount of the soluble carbon source becomes the greatest difficulty, and the method is very unfavorable for economic cost and operation management. Sufficient sustainable supply of available carbon sources is the main means to increase microbial activity. In addition, by combining the characteristics of the microporous 'multi-medium' active interface of the root-hole wetland, a rich aerobic and anaerobic microporous environment is constructed in the wetland substrate environment, an effective carbon source is continuously supplied for denitrification, the nitrification-denitrification coupled denitrification process is further improved, and the removal efficiency of water nitrogen can be accelerated.

SUMMERY OF THE UTILITY MODEL

To the problem, the utility model discloses an enhancement mode plant solid phase biological carbon to root hole wetland micropore "multimedium" active interface is the core, has constructed the multistage ecological filterable annular root hole wetland system of plant solid phase biological carbon who gets rid of water nitrogen pollution.

In order to achieve the above purpose, the utility model adopts the following technical scheme:

a plant solid-phase biochar multi-level root hole wetland system for removing nitrogen pollution of a water body comprises an inner ring filtering system and an outer ring filtering system which are sleeved, wherein the inlet water of the wetland system is positioned at the inner side of the inner ring filtering system,

the inner ring filtering system is an annular column surrounded by a protective net, an inner ring substrate, plant solid-phase biochar and a nano aeration pipe are arranged in the protective net, and plants are planted in the inner ring substrate, the plant solid-phase biochar and the nano aeration pipe,

the outer ring filtering system is an annular column surrounded by a protective net, an outer ring substrate, plant solid-phase biochar and a nano aeration pipe are arranged in the protective net, plants are planted in the nano aeration pipe, and the outer ring filtering system is lower than the inner ring filtering system in height.

Preferably, the nano aeration pipe is transversely arranged in the inner ring matrix or the outer ring matrix, and the plant solid biochar is in the form of a plant solid biochar module surrounding the nano aeration pipe.

Preferably, the total volume ratio of the plant solid phase biochar module to the inner ring matrix or the outer ring matrix is 1: 3.

Preferably, the inner ring filtering system or the outer ring filtering system comprises an upper layer nano aeration pipe and a lower layer nano aeration pipe, and the lower layer nano aeration pipe is arranged in the middle lower layer of the inner ring filtering system or the outer ring filtering system.

Preferably, the distance between the lower layer of nano aeration pipe and the bottom of the inner ring filtering system or the outer ring filtering system is 15-25 cm.

Preferably, the lower layer nano aeration pipe is externally surrounded with a lower layer plant solid phase biological carbon module, and the lower layer plant solid phase biological carbon module comprises a lower layer three-dimensional plant net and plant solid phase biological carbon filled in the lower layer three-dimensional plant net.

Preferably, the upper layer nanometer aeration pipe is surrounded by an upper layer plant solid phase biological carbon module, and the upper layer plant solid phase biological carbon module comprises an upper layer three-dimensional plant net, plant solid phase biological carbon filled in the upper layer three-dimensional plant net and plants fixedly planted in the three-dimensional plant net.

The upper layer plant solid-phase biochar can be obtained by using a method which is general in the field, and can also be prepared by adopting the following method:

(0-1) making the aquatic plant straws and the corncobs into chips, mixing the chips, and then carrying out anaerobic curing in inert gas;

(0-2) after the three-dimensional plant net is added, spreading and activating on the surface of the three-dimensional plant net, and drying and curing in the air.

Preferably, the density of the plants planted in the upper three-dimensional plant net is 8-12 plants/square meter.

Preferably, the aquatic plant straws in the step (0-1) are straws of submerged plants, floating plants and emergent aquatic plants. Preferably, said submerged plant is mainly curly pondweed, and said floating plant is a member selected from the group consisting of watercress, water peanuts and watercress; the emergent aquatic plant is reed or zizania latifolia; preferably the aerial parts of the emergent aquatic plant straws.

Preferably, the mixing mass ratio of the aquatic plant straws and the corncobs in the step (0-1) is as follows: the submerged plant is a floating plant, the emergent plant is corncob = 25-35: 15-30: 5-15.

Preferably, the aquatic plant straws in the step (0-1) are dried and ground.

Preferably, the length of the aquatic plant straw in the step (0-1) is 1-2 cm; the corncob is a particle with the particle size of 1-2 cm.

Preferably, the inert gas in the step (0-1) is N₂。

Preferably, the temperature of the anaerobic curing in the step (0-1) is 25-40 ℃, and preferably 30-35 ℃.

Preferably, the temperature for activation in the step (0-2) is 30-35 ℃.

Preferably, the spreading activation in the step (0-2) is Ca (OH) spraying₂Or Mg (OH)₂And (5) activating the suspension.

Preferably, the material of the three-dimensional plant net is made into plant fiber; preferably, the plant fiber is coconut shell fiber or flax fiber.

Preferably, the inner ring matrix is a mixture of clay, iron oxide and limestone. Preferably, the mass ratio of the clay to the ferric oxide to the limestone is 80-90: 2-5: 5-10.

Preferably, the outer ring substrate is a mixture of sand, limestone and iron oxide. Preferably, the mass ratio of the gravel, the limestone and the iron oxide is 85-90: 2-5: 5-15.

Preferably, the protective net is a galvanized wire net.

Preferably, the plants are reed and cattail.

Preferably, in order to effectively control the ratio of the live root holes to the dead root holes and improve the denitrification efficiency of the root-hole wetland, the ratio of the porosity of the live root holes to the porosity of the dead root holes in the multistage root-hole wetland system is 1: 0.5-0.9, and the porosity ratio is specifically adjusted by adjusting the clay ratio and the aeration rate in the matrix layer. Plant roots are inserted into the matrix, root living holes are formed around the roots, functional microbial communities are formed by means of root secretion, and the effective range of the root holes is within 1-2cm of the root surface. The dead root hole is a gap left after the root system of the plant is rotten and dead.

According to the root hole wetland system, the nano aeration pipes are distributed in the substrate and the plant solid-phase biochar, an active biofilm layer is formed on the root surface of the root system periphery of the mixed substrate system for denitrification enhancement treatment of an aerobic-anaerobic microporous interface, and the developed root system of the plant, the microbial film attached to the surface of the substrate layer and the aeration pipeline are used as the basic plant active root hole system.

The inner ring is a core area, sewage is introduced into the inner ring through a pipeline, and the arranged nano aeration pipes enhance the reoxygenation capacity of a local water body. The height of the inner ring filtering system is higher than that of the outer ring filtering system, and the water body between the inner ring and the outer ring realizes the self-flow of the water body by utilizing the fall.

After the solid-phase biological carbon module of the plant containing the underground stem with the spore roots is arranged, the plant roots are filled with the three-dimensional plant net, the inner ring filtering system and the outer ring filtering system after 2-3 months.

The plant solid-phase biochar multistage root hole wetland system is constructed by adopting a multi-stage ecological filtering reticular root hole wetland, solves the problem of hydraulic flow path communication by utilizing water level difference, and realizes water quantity ecological filtration by step water level difference.

Preferably, the water head fall of the inner ring filtering system and the outer ring filtering system is controlled within the range of 0.2-0.4 m, and the height of the inner ring or the outer ring is 50-120 cm.

The utility model provides a solution's technical progress nature lies in:

(1) aiming at the technical difficult problem that the effective carbon source can be continuously supplied in the carbon supply stage, the utility model provides a technical scheme adopts the optimal configuration through the inside component structure of wetland system to realize. Specifically, the degradation characteristics and proportion configuration of different solid-phase plant materials are utilized, the wetland surplus plant materials are utilized for recycling, the advantages of wetland plant solid-phase carbon sources in the process of strengthening denitrification treatment are fully exploited, and no new pollution source is introduced to form secondary pollution.

(2) Aiming at the technical difficulty of excessive release of nitrogen and phosphorus nutritive salts in the process of supplying a carbon source, the plant carbon is utilized, simultaneously, the problem of excessive release of other plant secondary substances such as nitrogen and phosphorus is effectively controlled, the carbon nitrogen decay and decomposition process is effectively controlled by utilizing the slow release characteristic of the carbon, and simultaneously, a small amount of released soluble nitrogen and phosphorus is effectively fixed so as not to enter a water body to cause serious secondary pollution.

(3) Aiming at the problem of controlling toxic substances in carbon source supply, the technical difficulty of inhibiting effect of toxic and harmful substances released by anaerobic degradation on the denitrification process is as follows: in order to solve the problem of biological toxicity in the process of supplying the plant carbon source, excessive biological carbon supply causes the accumulation of anaerobic and toxic organic matters in a water body, and inhibits the physiological ecology and the enzyme activity of active microorganisms in the nitrification-denitrification process. The utility model discloses the slow-release process is given the reoxygenation of system simultaneously, has formed abundant anaerobism reoxygenation microenvironment, has avoided the toxic substance to denitrogenation process inhibitive nature, provides the powerful habitat condition for coupling denitrification denitrogenation process simultaneously.

(4) The performance of available biochar is improved, rich aerobic and anaerobic micropore environments are formed, good habitat conditions are provided for the high efficiency of the biochar, the reaction temperature of the biochar participating biochemical process is kept to be higher, the carbon utilization is continuous and efficient, and the technical problem of low efficiency of the winter wetland is solved to a certain extent. Under the common coupling of the two, the supply of carbon for the denitrification process in which the plant carbon source participates is ensured to be effectively utilized, and the coupling denitrification efficiency of the water body is improved.

The utility model has the advantages that:

(1) the utility model discloses in relate to engineering implementation technology process flow simplify relatively, technical operability is strong, but in the synchronous implementation of general constructed wetland construction process, promote ecological engineering's restoration effect.

(2) The utility model relates to a repair materials is ecological friendly type material like plant straw, reed, cattail etc to and slaked lime, diatomaceous earth, attapulgite, and low price, material source is wide, suits to apply in constructed wetland ecological engineering practice and promotes.

(3) The utility model provides a technical scheme, make full use of river lake ecosystem's oneself regulatory function reduces jamming frequency and intensity. Through the adjustment of the internal component structure of the ecological system, the supply quantity and quality of the carbon source of the plant material are improved, and the aim of sustainable and efficient supply of the carbon source is finally achieved. After the pretreatment of the carbon source supply, the secondary overflow of main pollutants in the carbon synchronous release process is removed or reduced, and the technical difficulty of low efficiency of the winter wetland is solved to a certain extent by utilizing the safe disposal and heat preservation performance of the eco-friendly modifier. The carbon source is utilized to be carried out in an oxidation pond and a vertical flow artificial wetland system, so that the denitrification rate is improved while the supply of effective carbon sources is not reduced.

The utility model discloses just look at wetland carbon source supply system, research and development kind lasts the preparation method of the water available carbon of high-efficient supply and utilizes biological carbon to construct the multistage root hole wetland system of an enhancement mode plant solid phase biological carbon, provides a new solution thinking for the treatment of china's polluted water and deposit nitrogen pollution.

Drawings

Fig. 1 is a schematic view of the multi-stage root-hole wetland system in the present invention.

Fig. 2 is a schematic diagram of a semi-section structure of the multi-stage root-hole wetland system of the present invention.

Wherein, 1 is a water inlet tank, 2 is an inner ring substrate, 3 is a first-stage water outlet tank, 4 is a second-stage water outlet tank, 5 is an outer ring filtering system, 6 is an outer ring substrate, 7 is a lower plant solid-phase carbon module, 8 is a nano aeration pipeline, 9 is a plant, and 10 is an upper plant solid-phase carbon module. The arrows in the figure indicate the direction of the water flow.

FIG. 3 is a graph showing the comparison of the dynamic changes of TOC in the water of example 1 before and after the addition of the plant immobilized biochar.

FIG. 4 shows N in a water body in example 1₂And (3) comparing the dynamic change of O before and after adding the plant solid biochar.

FIG. 5 is a graph showing the comparison of the dynamic changes of TOC in the water body before and after the addition of the plant immobilized biochar in example 2.

FIG. 6 shows N in a water body in example 2₂And (3) comparing the dynamic change of O before and after adding the plant solid biochar.

FIG. 7 is a graph showing the comparison of the dynamic changes of TOC in the water body before and after the addition of the plant immobilized biochar in example 3.

FIG. 8 shows N in a water body in example 3₂And (3) comparing the dynamic change of O before and after adding the plant solid biochar.

FIG. 9 is a graph showing the comparison of the dynamic changes of TOC in the water body before and after the addition of the plant immobilized biochar in example 4.

FIG. 10 shows N in a water body in example 4₂And (3) comparing the dynamic change of O before and after adding the plant solid biochar.

FIG. 11 is a graph showing the comparison of the dynamic changes of TOC in the water body before and after the addition of the plant immobilized biochar in example 5.

FIG. 12 shows N in a water body in example 5₂And (3) comparing the dynamic change of O before and after adding the plant solid biochar.

Detailed Description

The technical solution of the present invention will be described in detail with reference to the following description of specific embodiments and accompanying drawings. The scope of the present invention is not limited to the specific embodiments but is defined by the appended claims.

Example 1

According to the utility model discloses, to the problem of water nitrogen pollution, for the denitrification denitrogenation process of strengthening the oxidation pond of a certain river bypass water purification wetland in Anhui, utilize plant solid phase biological carbon mend carbon, promote microbial activity, promote denitrogenation efficiency. The specific embodiment is as follows:

(1) preparing the plant solid-phase biochar: collecting aerial parts of plant material such as potamogeton crispus, rhizoma Phragmitis, and caulis Zizaniae Caduciflorae, oven drying respectively, pulverizing into 1cm pieces, collecting corncob, oven drying, and pulverizing into particles with particle size of about 1 cm. Then mixing the curly pondweed, the Xincai, the reed and wild rice stem according to the mass ratio of 35:25:30:5 to obtain a plant-type carbon source, and storing the plant-type carbon source for further modification of the biological carbon by using the mixed modifier. Then the plant type carbon source is placed in N₂In the atmosphere of the above, anaerobic fermentation is carried out in a closed container at 30-35 ℃ to obtain a biochar material, a mixed modifier of 25g/L diatomite and 10% of slaked lime suspension is added in a scattering mode, the above substances are aged for 24 hours after being mixed, fermentation is carried out for 3 days, and the fermentation temperature is controlled at 30 ℃. Then performing secondary fermentation treatment, adding 50g/L zeolite suspension and 2mol/LH₂SO₄Spraying, mixing the above materials, aging for 24 hr, fermenting for 5 days, and controlling fermentation temperature at 32 deg.C. Obtaining the activated solid-phase plant carbon source after the fermentation is finished.

(2) Obtaining a three-dimensional plant net by using a coconut shell material, filling the obtained plant type carbon source into the three-dimensional plant net, wherein the filling volume is 60 percent, and then placing the net in the netSpraying 20g/L Ca (OH)₂And (4) suspending the solution. And carrying out secondary activation treatment to obtain the upper layer plant solid-phase biochar module.

(3) Preparing a solid-phase biochar module of the lower layer plant: planting the rhizomes of the reed and the cattail with the spore roots in the three-dimensional net of the obtained part of the upper plant solid-phase biological carbon module, and planting according to 8 plants per square meter. The buried depth of the spores is 5 cm.

(4) Constructing a plant solid-phase biochar multistage root-pore wetland system for removing nitrogen pollution of a water body:

an inner ring filtering system and an outer ring filtering system which are sleeved are constructed, the inlet water of the wetland system is positioned at the inner side of the inner ring filtering system, the inner ring filtering system and the outer ring filtering system are annular columns which are surrounded by a galvanized iron wire net, and the height of the outer ring filtering system is lower than that of the inner ring filtering system.

An auxiliary filler mixture consisting of clay, iron oxide and limestone is adopted as an inner ring matrix, the mass ratio of the clay, the iron oxide and the limestone is 80:2:10, an upper nano aeration pipe and a lower nano aeration pipe which are transversely arranged are arranged in the matrix, the lower nano aeration pipe surrounds a lower plant solid-phase biochar module, the distance from the bottom of the lower nano aeration pipe is 15-25 cm, and the upper nano aeration pipe surrounds the plant solid-phase biochar module.

The total volume ratio of the solid-phase biochar module of the implant in the inner ring to the inner ring matrix is 1: 3.

The structure of the outer ring is the same as that of the inner ring, except that the matrix of the outer ring is gravel and limestone and ferric oxide, and the mass ratio of the gravel to the limestone to the ferric oxide is 90:5: 5.

After 2 months, the plant root system is filled with the three-dimensional net and the annular substrate, and the multi-stage root-hole wetland system is basically constructed.

(5) After the system is stable after operating for a period of time, high-nitrogen sewage is introduced into the wetland system and flows out after being retained and treated by the annular root-hole wetland with multi-stage ecological filtration. The water body was continuously monitored for 6 months, and the data are shown in fig. 3 and 4. Finding soluble Total Organic Carbon (TOC) and N in water₂O was significantly higher than the control, 2.28 and 3.74 times higher than the control, respectively. Number of nitrifying and denitrifying bacteriaThe amount was increased by 95% and 120%, respectively. The removal rate of ammonia nitrogen and nitrate nitrogen in the water body is obviously reduced by 45% and 76% compared with the control. The effect is obvious, and the water quality is obviously improved.

Example 2

According to the utility model discloses, to the problem of water nitrogen pollution, for the denitrification process of the perpendicular flow wetland of strengthening a certain river bypass water purification wetland in Anhui, utilize plant solid phase biological carbon mend carbon, promote microbial activity. The specific embodiment is as follows:

(1) preparing the plant solid-phase biochar: collecting aerial plant materials of curly pondweed, green armyworm, and stem of Zizania aquatica, respectively oven drying, pulverizing into 2cm pieces, collecting corncob, oven drying, and pulverizing into 2cm granule. Then mixing the curly pondweed, the myrica rubra and the Xinjiang vegetable according to the mass ratio of 25:30:30:15 of the wild rice stem to the corncob to obtain a plant-type carbon source, and storing the plant-type carbon source for modifying the biological carbon by utilizing the mixed modifying agent in the next step. Then the plant type carbon source is placed in N₂The biochar material is obtained by anaerobic fermentation in a closed container at the temperature of 25-30 ℃ in the atmosphere, a mixed modifier of 60g/L attapulgite and 12% hydrated lime suspension is added in a spreading mode, the substances are aged for 24 hours after being mixed, fermentation is started for 3 days, and the fermentation temperature is controlled to be 30 ℃. Then performing secondary fermentation treatment, adding 60g/L zeolite suspension and 2mol/LH₂SO₄Spraying, mixing the above materials, aging for 24 hr, fermenting for 5 days, and controlling fermentation temperature at 32 deg.C. Obtaining the activated solid-phase plant carbon source after the fermentation is finished.

(2) Obtaining a three-dimensional plant net by using flax fibers, filling the obtained plant type carbon source into the three-dimensional plant net, wherein the filling volume is 60%, and then spraying 20g/L of Ca (OH)₂And 10% Mg (OH)₂And (4) suspending the solution. And carrying out secondary activation treatment to obtain the upper layer plant solid-phase biochar module.

(3) Preparing a solid-phase biochar module of the lower layer plant: planting the rhizomes of the reed and the cattail with the spore roots in the three-dimensional net of the obtained part of the upper plant solid-phase biological carbon module, and planting according to 10 plants per square meter. The buried depth of the spores is 10 cm.

An auxiliary filler mixture consisting of clay, iron oxide and limestone is adopted as an inner ring matrix, the mass ratio of the clay, the iron oxide and the limestone is 90:5:5, an upper nano aeration pipe and a lower nano aeration pipe which are transversely arranged are arranged in the matrix, the lower nano aeration pipe surrounds a lower plant solid-phase biochar module, the distance from the bottom of the lower nano aeration pipe is 15-25 cm, and the upper nano aeration pipe surrounds the plant solid-phase biochar module.

The structure of the outer ring is the same as that of the inner ring, except that the matrix of the outer ring is gravel and limestone and ferric oxide, and the mass ratio of the gravel to the limestone to the ferric oxide is 85: 2: 15.

(5) After the system is stable after operating for a period of time, high-nitrogen sewage is introduced into the wetland system and flows out after being retained and treated by the annular root-hole wetland with multi-stage ecological filtration. The water body was continuously monitored for 6 months, and the data are shown in fig. 5 and 6. Finding soluble Total Organic Carbon (TOC) and N in water₂O is significantly higher than the control, wherein TOC and the denitrification product N in the water body₂O is 1.64 and 3.28 times of the control respectively, and the quantity of the nitrifying bacteria and the denitrifying bacteria is increased by 85 percent and 140 percent respectively. The ammonia nitrogen and nitrate nitrogen in the water body are 52 percent and 68 percent lower than those in the contrast. The effect is obvious, and the water quality is obviously improved.

Example 3

(1) preparing the plant solid-phase biochar: collecting aerial plant materials of curly pondweed, water caltrop, waterweed and water peanut straw, respectively drying, pulverizing into 1cm small segments, collecting corn cob, drying, and pulverizing into particles with particle diameter of about 1 cm. And then mixing the curly pondweed, the mixture of the green water peanuts and the waterweed, the wild rice stems and the corncobs according to the mass ratio of 35:35:15:15 to obtain a plant-type carbon source, and storing the plant-type carbon source for modifying the biological carbon by utilizing the mixed modifying agent in the next step. Then the plant type carbon source is placed in N₂In the atmosphere, performing anaerobic fermentation in a closed container at 35-40 ℃ to obtain a biochar material, adding a mixed modifier of 150g/L attapulgite and 20% hydrated lime suspension in a spreading mode, mixing the above components, aging for 24h, fermenting for 3 days, and controlling the fermentation temperature to be 30 ℃. Then performing secondary fermentation treatment, adding 20g/L zeolite suspension and 2mol/LH₂SO₄Spraying, mixing the above materials, aging for 24 hr, fermenting for 5 days, and controlling fermentation temperature at 35 deg.C. Obtaining the activated solid-phase plant carbon source after the fermentation is finished.

(2) Obtaining a three-dimensional plant net by using a coconut shell material, filling the obtained plant type carbon source into the three-dimensional plant net, wherein the filling volume is 65%, and then spraying 10g/L of Ca (OH) on the net₂And 10% Mg (OH)₂And (4) suspending the solution. And carrying out secondary activation treatment to obtain the upper layer plant solid-phase biochar module.

(5) After the system is stable after operating for a period of time, high-nitrogen sewage is introduced into the wetland system and flows out after being retained and treated by the annular root-hole wetland with multi-stage ecological filtration. The water body was continuously monitored for 6 months, and the data are shown in fig. 7 and 8. Finding soluble Total Organic Carbon (TOC) and N in water₂O is significantly higher than the control, wherein TOC and the denitrification product N in the water body₂O is 1.70 and 2.70 of the control respectively, and the numbers of nitrobacteria and denitrifying bacteria are increased by 75 percent and 160 percent respectively. The ammonia nitrogen and nitrate nitrogen in the water body are 55 percent and 71 percent lower than those in the contrast. The effect is obvious, and the water quality is obviously improved.

Example 4

(1) preparing the plant solid-phase biochar: collecting aerial plant material of curly pondweed, water bamboo grass and green foxtail algae, and respectively bakingDrying, pulverizing into 1cm pieces, collecting corn cob, oven drying, and pulverizing into 1cm granule. Then mixing the curly pondweed, the myrica rubra, the zizania latifolia and the corncob according to the mass ratio of 25:35:30:10 to obtain a plant-type carbon source, and storing the plant-type carbon source for modifying the biological carbon by using the mixed modifying agent in the next step. Then the plant type carbon source is placed in N₂The fermentation is carried out in a closed container at the temperature of 30-35 ℃ in the atmosphere to obtain a biochar material, a mixed modifier of 160 g/L diatomite and 15% of slaked lime suspension is added in a scattering mode, the substances are aged for 24 hours after being mixed, fermentation is carried out for 3 days, and the fermentation temperature is controlled to be 30 ℃. Then performing secondary fermentation treatment, adding 10g/L zeolite suspension and 2mol/LH₂SO₄Spraying, mixing the above materials, aging for 24 hr, fermenting for 5 days, and controlling fermentation temperature at 35 deg.C. Obtaining the activated solid-phase plant carbon source after the fermentation is finished.

(2) Obtaining a three-dimensional plant net by using a coconut shell material, filling the obtained plant type carbon source into the three-dimensional plant net, wherein the filling volume is 70%, and then spraying 15g/L of Ca (OH) on the net₂And 10% Mg (OH)₂And (4) suspending the solution. And carrying out secondary activation treatment to obtain the upper layer plant solid-phase biochar module.

(5) After the system is stable after operating for a period of time, high-nitrogen sewage is introduced into the wetland system and flows out after being retained and treated by the annular root-hole wetland with multi-stage ecological filtration. The water body was continuously monitored for 6 months, and the data are shown in fig. 9 and 10. Finding soluble Total Organic Carbon (TOC) and N in water₂O is significantly higher than the control, wherein TOC and the denitrification product N in the water body₂O is 1.70 and 2.70 of the control respectively, and the numbers of nitrobacteria and denitrifying bacteria are increased by 85 percent and 180 percent respectively. The ammonia nitrogen and nitrate nitrogen in the water body are 65 percent and 77 percent lower than those in the contrast. The effect is obvious, and the water quality is obviously improved.

Example 5

(1) preparing the plant solid-phase biochar: collecting water caltrop and aerial plant material of Foliuba, Zizania latifolia, and Foliuba Luciformis straw, respectively oven drying, pulverizing into 1cm small segments, collecting corn cob, oven drying, and pulverizing into particles with particle diameter of about 1 cm. Then mixing the curly pondweed, the myrica rubra, the zizania latifolia and the corncob according to the mass ratio of 30:30:25:15 to obtain a plant-type carbon source, and storing the plant-type carbon source for modifying the biological carbon by using the mixed modifying agent in the next step. Then the plant type carbon source is placed in N₂In the atmosphere ofAnaerobic fermentation is carried out in a closed container at the temperature of 30-35 ℃ to obtain a biochar material, a mixed modifier of 120 g/L kaolin and 10% hydrated lime suspension is added in a spreading mode, the above substances are aged for 24 hours after being mixed, fermentation is carried out for 3 days, and the fermentation temperature is controlled at 30 ℃. Then performing secondary fermentation treatment, adding 15g/L zeolite suspension and 2mol/LH₂SO₄Spraying, mixing the above materials, aging for 24 hr, fermenting for 5 days, and controlling fermentation temperature at 35 deg.C. Obtaining the activated solid-phase plant carbon source after the fermentation is finished.

(2) Obtaining a three-dimensional plant net by using a coconut shell material, filling the obtained plant type carbon source into the three-dimensional plant net with the filling volume of 60%, and then spraying 20g/L of Ca (OH)₂And 12% Mg (OH)₂And (4) suspending the solution. And carrying out secondary activation treatment to obtain the upper layer plant solid-phase biochar module.

(5) After the system is stable after operating for a period of time, high-nitrogen sewage is introduced into the wetland system and flows out after being retained and treated by the annular root-hole wetland with multi-stage ecological filtration. The water body was continuously monitored for 6 months, and the data are shown in fig. 11 and 12. Finding soluble Total Organic Carbon (TOC) and N in water₂O is significantly higher than the control, wherein TOC and the denitrification product N in the water body₂O is 1.81 and 3.14 of the control respectively, and the numbers of the nitrifying bacteria and the denitrifying bacteria are increased by 85 percent and 120 percent respectively. The ammonia nitrogen and nitrate nitrogen in the water body are 40 percent and 70 percent lower than those in the contrast. The effect is obvious, and the water quality is obviously improved.

Claims

1. A plant solid-phase biochar multi-level root hole wetland system for removing nitrogen pollution of a water body is characterized by comprising an inner ring filtering system and an outer ring filtering system which are sleeved, wherein the inlet water of the wetland system is positioned at the inner side of the inner ring filtering system,

the inner ring filtering system is an annular column surrounded by a protective net, an inner ring substrate, plant solid-phase biochar and a nano aeration pipe are arranged in the protective net, plants are planted in the nano aeration pipe, the nano aeration pipe is transversely arranged in the inner ring substrate, the plant solid-phase biochar surrounds the nano aeration pipe in the form of a plant solid-phase biochar module,

the outer ring filtering system is an annular column surrounded by a protective net, an outer ring substrate, plant solid-phase biochar and a nano aeration pipe are arranged in the protective net, plants are planted in the nano aeration pipe, the nano aeration pipe is transversely arranged in the outer ring substrate, the plant solid-phase biochar surrounds the nano aeration pipe in a plant solid-phase biochar module mode, and the outer ring filtering system is lower than the inner ring filtering system in height.

2. The multi-stage root-hole wetland system of claim 1, wherein the total volume ratio of the plant solid biochar module to the inner ring matrix or the outer ring matrix is 1: 3.

3. The multi-stage root-hole wetland system of claim 1, wherein the inner ring filtration system or the outer ring filtration system comprises an upper layer nano aerator pipe and a lower layer nano aerator pipe, and the lower layer nano aerator pipe is arranged at the middle lower layer of the inner ring filtration system or the outer ring filtration system.

4. The multi-stage root-hole wetland system of claim 3, wherein the lower-layer nanoaeration pipe is 15-25 cm away from the bottom of the inner ring filtration system or the outer ring filtration system.

5. The multi-stage root-hole wetland system according to claim 3, wherein the lower nano aeration pipe is externally surrounded by a lower plant solid biochar module, and the lower plant solid biochar module comprises a lower three-dimensional plant net and plant solid biochar filled in the lower three-dimensional plant net; the upper layer nanometer aeration pipe is surrounded by an upper layer plant solid phase biological carbon module, the upper layer plant solid phase biological carbon module comprises an upper layer three-dimensional plant net, plant solid phase biological carbon filled in the upper layer three-dimensional plant net and plants fixedly planted in the three-dimensional plant net.

6. The multi-stage root-hole wetland system of claim 5, wherein the density of the plants planted in the upper three-dimensional plant net is 8-12 plants per square meter.

7. The multi-stage root-hole wetland system of claim 1, wherein the protective mesh is galvanized wire.

8. The multi-stage root-hole wetland system of claim 1, wherein the plants are reed and typha orientalis.

9. The multi-stage root-hole wetland system of claim 1, wherein the ratio of the porosity of the live root holes to the porosity of the dead root holes in the multi-stage root-hole wetland system is 1: 0.5-0.9.