1. Has the functions of synchronous denitrification and N reduction₂The rainwater garden with the O-release potential function is characterized by comprising a covering layer, a soil layer, a sand layer and a gravel layer which are sequentially arranged from top to bottom, wherein the covering layer comprises bark scraps, biochar is arranged in the soil layer, a denitrification microorganism population is enriched on the surface of the biochar to realize rainwater denitrification, and an organic carbon source is arranged in the sand layer and used for enhancing the microbial denitrification and reducing N simultaneously₂O release potential, a water outlet pipe is installed at the bottom of the gravel layer and connected with an external water outlet, and the height of the external water outlet is set to form a water immersion area inside the rainwater garden.

2. A rainwater garden as claimed in claim 1, wherein the overall thickness of the cover is 2-10 cm.

3. A rainshed garden as claimed in claim 2, wherein the mulch comprises loose scales.

4. A stormwater garden as claimed in any one of claims 1 to 3, wherein the soil has a particle size of not more than 5mm, a total thickness of 40cm, and the volume ratio of the biochar to the soil layer is 10%.

5. A raindrop garden as claimed in any one of claims 1 to 4, wherein the organic carbon source is a slow release organic carbon source; preferably, the slow-release organic carbon source comprises sawdust and bagasse, and more preferably, the sand layer comprises 5% by volume of sawdust and 5% by volume of bagasse.

6. A stormwater garden as claimed in any one of claims 1 to 5, wherein the sand bed is of construction fine sand having a grit size of no more than 3mm and a total thickness of 20 cm.

7. A stormwater garden as claimed in any one of claims 1 to 6, wherein the gravel layer is construction gravel having a particle size of 3 to 5cm and a total thickness of 10 cm.

8. A stormwater garden as claimed in any one of claims 1 to 7, wherein a water permeable cloth is laid between adjacent layers for separation.

9. A rainwater garden as claimed in any one of claims 1 to 8, wherein said soil layer is seeded with lawn grass.

10. A raindrop garden as claimed in claim 9, wherein said lawn grass is nanniella dwarfina; preferably, the method for sowing the turfgrass is to water the turfgrass once every three days instead of spraying water every day until the plants and roots develop to maturity. The plants are grown too high and trimmed to a length of about 2cm above the cover layer 1 and the trimmed parts are removed.

Background

Along with the process of urbanization, the impervious underlying surface is gradually increased, so that the runoff of rainwater is greatly increased, a large amount of pollutants are brought into downstream water bodies, and urban inland inundation and non-point source pollution are caused. The surface water pollution problem in China is serious, and researches show that about 15 percent of pollutants in urban water bodies are from non-point source pollution.

Pollutants contained in the rainwater runoff comprise nutritive salts (nitrogen and phosphorus), heavy metals, organic carbon (PAHs), bacteria, viruses, total suspended solids and the like. Many researches show that the removal ways of pollutants by low-impact development facilities comprise adsorption, replacement, precipitation, volatilization, biodegradation, nutrient cycle and the like, but the removal effect on soluble nitrate nitrogen is poor, even the nitrogen release phenomenon occurs, and the water eutrophication is aggravated. Therefore, the design of a novel enhanced denitrification rainwater treatment facility has important significance for reducing the nitrogen pollution load of the water body and controlling the eutrophication of the water body.

The rainwater denitrification process is mainly carried out through the nitrification and denitrification of microorganisms. Nitrous oxide (N) in microbial denitrification processes₂O) will be released as nitration by-products and denitrification intermediates. N is a radical of₂O is one of three greenhouse gases, 1mol N₂O has an infrared radiation intensity of about CO₂206 times of the total carbon dioxide, longer residence time in the atmosphere (about 120 years), and approximate CO greenhouse effect₂300 times of the total weight of the powder. Although N is₂O is very low in the atmosphere (about 322ppbv) and represents only 0.03% of the total greenhouse gas release, but contributes about 4.5% to the total greenhouse effect and 6-8% to the anthropogenic greenhouse effect. N in the atmosphere₂For every 1% increase in O content, the greenhouse effect increases by about 30%. Therefore, with the aggravation of urban non-point source pollution problem and the wide application of rainwater treatment facilities, how to reduce the pollution is reducedN₂The problem of O release is also urgently to be solved.

It is to be noted that the information disclosed in the above background section is only for understanding the background of the present application and thus may include information that does not constitute prior art known to a person of ordinary skill in the art.

Disclosure of Invention

The main purpose of the present invention is to overcome the drawbacks of the prior art and to provide a method for simultaneous denitrification and N reduction₂O release potential acting rain gardens.

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

has the functions of synchronous denitrification and N reduction₂The rainwater garden with the O-release potential function comprises a covering layer, a soil layer, a sand layer and a gravel layer which are sequentially arranged from top to bottom, wherein the covering layer comprises bark scraps, biochar is arranged in the soil layer, a denitrification microorganism population is enriched on the surface of the biochar to realize rainwater denitrification, an organic carbon source is arranged in the sand layer and used for enhancing the microbial denitrification and reducing N₂O release potential, a water outlet pipe is installed at the bottom of the gravel layer and connected with an external water outlet, and the height of the external water outlet is set to form a water immersion area inside the rainwater garden.

The total thickness of the covering layer is 2-10 cm.

The coating includes loose scales.

The granularity of the soil is not more than 5mm, the total thickness is 40cm, and the volume ratio of the biochar to the soil layer is 10%.

The organic carbon source is a slow-release organic carbon source; preferably, the slow-release organic carbon source comprises sawdust and bagasse, and more preferably, the sand layer comprises 5% by volume of sawdust and 5% by volume of bagasse

The sand layer is made of building fine sand, the granularity of the fine sand is not more than 3mm, and the total thickness is 20 cm.

The gravel layer is gravel for construction, the particle size of the gravel is 3-5cm, and the total thickness is 10 cm.

And a permeable cloth is laid between the adjacent layers for separation.

Lawn grass is sowed in the soil layer.

The turfgrass is dwarf manila.

The method for sowing the lawn grass comprises the steps of watering in a spraying mode every day until the plants and root systems develop to be mature, and watering once in about three days. The plants are grown too high and trimmed to a length of about 2cm above the cover layer 1 and the trimmed parts are removed.

Compared with the prior art, the invention has the following beneficial effects:

the invention provides a method for synchronously strengthening denitrification and reducing N₂The rainwater garden with the function of releasing the potential of O, the height of an external water outlet connected with a water outlet pipe of the rainwater garden is set so as to form a water immersion area in the rainwater garden, and the water immersion area can continuously and stably provide an anoxic environment, wherein biochar is arranged on a soil layer, the surface area of the biochar is large, the water seepage performance of the soil can be improved, the microbial population for denitrification is enriched on the surface of the biochar, the denitrification effect of the rainwater garden is enhanced, the nitrogen pollutants in the runoff of rainwater on a road are effectively removed, meanwhile, an organic carbon source is also arranged on a sand layer, preferably a slow-release organic carbon source is adopted, and under the coordination of the anoxic environment provided by the water immersion area, the enhanced denitrification and the reduction of N are synchronously realized₂Release potential of O. Through the integral design of the rainwater garden structure, the rainwater garden can effectively reduce N while denitrifying and preventing pollution₂O release potential and reduce greenhouse effect.

Drawings

Fig. 1 is a schematic view of the structure of a rainwater garden according to an embodiment of the present invention.

FIG. 2 is a graph showing denitrification effects of the rainwater garden according to the embodiment of the present invention at different rainfall periods.

Fig. 3 is a graph showing the effect of N2O release in a raining garden according to an embodiment of the present invention at different periods of rainfall.

Detailed Description

The embodiments of the present invention will be described in detail below. It should be emphasized that the following description is merely exemplary in nature and is not intended to limit the scope of the invention or its application.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element. In addition, the connection may be for either a fixed or coupled or communicating function.

It is to be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in an orientation or positional relationship indicated in the drawings for convenience in describing the embodiments of the present invention and to simplify the description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed in a particular orientation, and be in any way limiting of the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the embodiments of the present invention, "a plurality" means two or more unless specifically limited otherwise.

Referring to FIG. 1, in one embodiment, a process for simultaneous denitrification and N reduction₂The rainwater garden with the O-release potential effect comprises a covering layer 1, a soil layer 2, a sand layer 3 and a gravel layer 4 which are sequentially arranged from top to bottom, wherein the covering layer 1 comprises bark scraps, biochar is arranged in the soil layer 2, a denitrification microorganism population is enriched on the surface of the biochar to realize rainwater denitrification, an organic carbon source is arranged in the sand layer 3 and used for enhancing the microbial denitrification and reducing N₂The gravel layer 4 also acts as a drainage layer, the gravelThe bottom of the stone layer 4 is provided with a water outlet pipe 5, the water outlet pipe 5 is connected with an external water outlet 6, and the height of the external water outlet 6 is set to form a water immersion area 7 inside the rainwater garden. By setting the height of the water outlet, a water immersion area 7 is formed in the rainwater garden, and an anoxic environment can be continuously and stably provided by utilizing the water immersion effect of the water immersion area 7. In the anoxic environment, the microorganisms can effectively utilize the organic carbon source arranged in the sand layer 3, thereby achieving the purposes of strengthening denitrification and reducing N₂The role of the O release potential.

The rainwater garden provided by the embodiment of the invention forms the soaking area 7, the biochar is arranged on the soil layer 2, the specific surface area is large, the water seepage performance of the soil can be improved, the biochar is loaded with microorganisms on the surface, the in-situ domestication and the enrichment of denitrification microorganism populations are realized, the denitrification effect of the rainwater garden is enhanced, the effective removal of nitrogen pollutants in the rainwater runoff of a road is realized, meanwhile, the organic carbon source is arranged on the sand layer 3, the soaking area 7 provides an anoxic environment, and the synchronous realization of the enhanced microorganism denitrification and the N reduction are facilitated₂O release potential.

Specific embodiments of the present invention are described further below by way of example.

The construction of a rain garden according to a specific embodiment is shown in fig. 1 and comprises, from top to bottom, a cover layer 1, a soil layer 2, a sand layer 3 and a gravel layer 4. Wherein the gravel layer 4 also acts as a drainage layer, the bottom of the gravel layer 4 is fitted with an outlet pipe 5, for example a perforated pipe of 20cm diameter, the outlet pipe 5 is connected to an external outlet 6, the height of the external outlet 6 being set to form a submerged area 7 inside the storm water garden. The flooding action of the flooding zone 7 can provide an anoxic environment continuously and stably. The effluent which is highly above the soaking zone 7 during rainfall can be collected through the outlet pipe 5 of the gravel layer 4 and the external outlet 6.

In a preferred embodiment, the cover layer 1 is pine bark such as pine scales, has a total thickness of 2-10cm, such as 2-3cm, more preferably 5-10cm, and can protect plants.

In a preferred embodiment, the soil layer 2 has a soil grain size of not more than 5mm and a total thickness of 40 cm. The volume ratio of the biochar to the soil layer 2 is 10%.

In a preferred embodiment, the sand layer is constructed by fine sand with the granularity of no more than 3mm and the total thickness of 20 cm.

In a preferred embodiment, the organic carbon source is a slow-release organic carbon source. The slow-release organic carbon source can adopt wood chips, bagasse and the like. In a particularly preferred embodiment, the sand layer 3 comprises 5% by volume of wood chips and 5% by volume of bagasse.

In a preferred embodiment, the gravel layer 4 is construction gravel with a particle size of 3-5cm and a total thickness of 10 cm.

In a preferred embodiment, black permeable geotextile is laid at the bottom of each filler layer for separation, so that the filler is prevented from being lost.

In a preferred embodiment, the soil layer 2 is seeded with turfgrass, preferably nanniella dwarfii. One preferred method of seeding is to water the plant and root system once every three days after they have developed maturity. The plants are grown too high and trimmed to a length of about 2cm above the cover layer 1 and the trimmed parts are removed.

Experimental example:

the rainfall simulation experiment was carried out using the flooded rainwater garden of the example.

Referring to the urban road rainfall runoff characteristics, the chemical composition of the synthetic road rainfall runoff used in the embodiment is shown in table 1, wherein the chemical composition contains 111mg/L Chemical Oxygen Demand (COD) and 1.5mg/L ammonia Nitrogen (NH)₄-N), 2.0mg/L nitrate Nitrogen (NO)₃-N) and 3mg/L organic nitrogen. Before each rainfall simulation experiment, 0.3mL/L of trace element stock solution is added into the synthetic road rainwater runoff. The chemical components of the synthetic road rainfall runoff are shown in table 1.

TABLE 1 synthetic chemical composition table for road rainfall runoff

In this example, the greening rate is taken5% and the rainfall intensity is 5 mm/h. The runoff coefficient of the catchment area is 0.9 (design code for water supply and drainage of buildings GB50015-2009) according to the concrete pavement. This example focuses on investigating the denitrification efficiency and N of a flooded rainwater garden₂O release characteristics.

The pollutant removal effect of the submerged rainwater garden under different rainfall periods is investigated, and the rainfall simulation experiment with the rainfall periods of 6h and 8h (the sampling time is 24h) is carried out. Removing effect of submerged rainwater garden on nitrogen pollutants in road runoff and N₂The O release effect is shown in fig. 2 and 3, respectively.

As can be seen from figure 2, the denitrification efficiency of the submerged rainwater garden reaches more than 80%, and the effluent quality is stable.

As can be seen from FIG. 3, the rainfall duration is 6h, and N is the simulated rainfall₂Gradually increasing the amount of O released, N₂The release amount of O is rapidly increased to about 1mg N₂O-N/m²And the rainfall duration is 8h of rainfall simulation N₂The release amount of O is basically stabilized at 0.04-0.07mg N₂O-N/m²Within the range. Thus, the submerged rain garden pair reduces N under long-term rainfall conditions₂The role of the O release potential is better.

The background of the present invention may contain background information related to the problem or environment of the present invention and does not necessarily describe the prior art. Accordingly, the inclusion in the background section is not an admission of prior art by the applicant.

The foregoing is a more detailed description of the invention in connection with specific/preferred embodiments and is not intended to limit the practice of the invention to those descriptions. It will be apparent to those skilled in the art that various substitutions and modifications can be made to the described embodiments without departing from the spirit of the invention, and these substitutions and modifications should be considered to fall within the scope of the invention. In the description herein, references to the description of the term "one embodiment," "some embodiments," "preferred embodiments," "an example," "a specific example," or "some examples" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Various embodiments or examples and features of various embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction. Although embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the scope of the claims.