A system and method for treating wastewater using a subsurface flow wetland

Abstract

The present application provides a kind of subsurface wetland sewage treatment system and method, the system includes microbial in-situ reactor and subsurface wetland, and the microbial in-situ reactor is communicated with subsurface wetland.The present method includes the following steps: the sewage to be treated is divided into first sewage to be treated and second sewage to be treated after preliminary sedimentation storage, and the first sewage to be treated is used to activate microorganism under the action of nutrient agent, to obtain first treatment mixed liquor;The first treatment mixed liquor is introduced into subsurface wetland, and the second sewage to be treated is treated by the first treatment mixed liquor, to obtain treated sewage.The present application combines microbial in-situ reactor, which not only increases the dissolved oxygen in water body, but also rapidly increases the content and activity of microorganism in the system, to improve the treatment efficiency of the system on pollutants.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and in particular relates to a system and method for treating wastewater using subsurface flow wetlands. Background Technology

[0002] In recent years, the central government has proposed the guiding principle of sponge city construction. A sponge city refers to a city that, like a sponge, possesses good "elasticity" in adapting to environmental changes and responding to natural disasters. It absorbs, stores, infiltrates, and purifies rainwater when it rains, and releases and utilizes the stored water when needed. Sponge city construction should adhere to principles such as ecological priority, combining natural pathways with subsurface flow measures. While ensuring urban drainage and flood control safety, it should maximize the accumulation, infiltration, and purification of rainwater in urban areas, promoting the utilization of rainwater resources and ecological environmental protection. During the construction of sponge cities, the systematic nature of natural precipitation, surface water, and groundwater should be considered, along with the coordination of various links in the water cycle, including water supply and drainage, taking into account its complexity and long-term nature.

[0003] Subsurface flow wetlands are widely used for water purification and restoration, non-point source pollution control, and initial rainfall treatment. However, current subsurface flow wetlands exhibit a predominance of aerobic microorganisms at the front end, while anaerobic microorganisms become dominant further downstream. Simultaneously, the rapid growth of heterotrophic bacteria easily clogs the packing material, severely impacting the overall wetland system's treatment efficiency. Therefore, rapidly increasing the activity and proportion of aerobic microorganisms throughout the wetland system, while simultaneously reducing sediment production and preventing subsurface flow wetland clogging, has become a key focus in wetland treatment. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a subsurface flow wetland wastewater treatment system and method to solve the problems of low treatment efficiency and easy clogging of the packing material.

[0005] To achieve the above and other related objectives, the first aspect of the present invention provides a subsurface flow wetland system for treating wastewater, comprising a microbial in-situ reactor and a subsurface flow wetland, wherein the microbial in-situ reactor is connected to the subsurface flow wetland and utilizes pollutants in the polluted water as a nutrient source in situ.

[0006] Preferably, the subsurface flow wetland includes a connected subsurface flow wetland section and a distribution channel, and the in-situ microbial reactor is connected to the distribution channel and the subsurface flow wetland section respectively.

[0007] Preferably, it further includes at least one of the following technical features:

[0008] a1) The subsurface flow wetland section includes a planting area and a filler area;

[0009] a2) The microbial in-situ reactor is provided with a first inlet pipe and a first outlet pipe. The microbial in-situ reactor is connected to the water distribution channel through the first inlet pipe, and the microbial in-situ reactor is connected to the subsurface flow wetland through the first outlet pipe.

[0010] a3) The system also includes a booster pump, which is located on the pipeline between the microbial in-situ reactor and the water distribution channel;

[0011] a4) The subsurface wetland section is equipped with a second outlet pipe.

[0012] Preferably, it further includes at least one of the following technical features:

[0013] In feature b1), the filling area, from top to bottom, includes a river sand layer, a geotextile layer, a filling layer, a protective layer, and an impermeable layer.

[0014] b2) The filler layer is made of silicate ceramic particles with a diameter ranging from 10 to 50 mm.

[0015] Preferably, it further includes at least one of the following technical features:

[0016] c1) The microbial in-situ reactor described herein contains microorganisms and nutrients;

[0017] c2) The system also includes a regulating pool, which is connected to the subsurface flow wetland.

[0018] Preferably, it further includes at least one of the following technical features:

[0019] d1) The system further includes a filter element, which is located at the water inlet of the equalization tank;

[0020] d2) The system also includes a submersible sewage pump, and the equalization tank is connected to the submersible flow wetland via the submersible sewage pump.

[0021] d3) The regulating tank is equipped with a second inlet pipe.

[0022] Preferably, it further includes at least one of the following technical features:

[0023] In feature d1), the filter element is a hanging basket grid;

[0024] In feature d31), the system further includes a valve well, which contains one or more valves located on the pipeline connecting the submersible pump and the submersible wetland.

[0025] Another aspect of the present invention provides a method for treating wastewater using a subsurface flow wetland, employing the system described above, and comprising the following steps:

[0026] 1) After primary sedimentation and conditioning, the wastewater to be treated is divided into the first wastewater to be treated and the second wastewater to be treated. The first wastewater to be treated is used to activate microorganisms under the action of nutrients to obtain the first treatment mixture.

[0027] 2) The first treatment mixture is introduced into the subsurface flow wetland, and the second wastewater to be treated is treated by the first treatment mixture to obtain treated wastewater.

[0028] Preferably, it includes at least one of the following technical features:

[0029] e1) The microorganisms include nitrifying bacteria, nitrite-oxidizing bacteria, denitrifying bacteria, Bacillus subtilis, Bacillus mucilaginosus and its products, Bacillus megaterium, Lactobacillus plantarum, Candida utilis, and Nocardia fibrosis; the mass ratio of each component in the microorganisms is: 1.0:0.8±0.03:1.0±0.03:1.5±0.15:1.5±0.17:1.2±0.12:0.7±0.05:1.0±0.07:1.0±0.10;

[0030] e2) The nutrient solution comprises, by mass fraction, 50.3%–59.7% corn flour, 13.1%–16.9% sucrose, 21.8%–26.2% cellulose, 0.89%–1.11% ammonium sulfate, 0.69%–0.81% magnesium sulfate heptahydrate, 0.69%–0.81% magnesium nitrate, 1.85%–2.15% ferrous sulfate, 0.67%–0.83% potassium dihydrogen phosphate, and 0.71%–0.79% sodium ammonium hydrogen phosphate.

[0031] Preferably, the ratio of the microorganisms to the nutrient is 96:1 to 120:1.

[0032] The above technical solution has the following beneficial effects:

[0033] As described above, the subsurface flow wetland system and method for treating wastewater according to the present invention have at least one of the following beneficial effects:

[0034] 1. This invention uses specially made silicate ceramic particles as the matrix of subsurface flow wetlands. Its high porosity and large specific surface area can not only adsorb a large amount of nutrients, but also serve as a microbial carrier, which can efficiently remove nutrients from water bodies and is not easily clogged.

[0035] 2. This invention combines a microbial in-situ reactor, which increases dissolved oxygen in the water and rapidly increases the content and activity of microorganisms in the system, thereby improving the system's efficiency in treating pollutants.

[0036] 3. Sponge city subsurface flow wetlands have low efficiency in treating surface runoff sewage, and the filler is prone to clogging and has a short lifespan. This invention can effectively solve the above problems. Attached Figure Description

[0037] Figure 1 The diagram shown is a schematic representation of a subsurface flow wetland system for treating wastewater according to the present invention.

[0038] Figure 2 The diagram shows the effect of a subsurface flow wetland system for treating wastewater on the removal of total phosphorus (TP) from initial stormwater runoff.

[0039] Figure 3 The system for treating wastewater using subsurface flow wetlands, as described in this invention, demonstrates the effectiveness of TN removal from initial stormwater runoff.

[0040] Figure 4 The diagram shows the effect of a subsurface flow wetland wastewater treatment system of the present invention on the removal of NH4+-N from initial rainwater runoff.

[0041] Figure 5 The diagram shows the CODcr removal effect of a subsurface flow wetland wastewater treatment system according to the present invention on initial rainwater runoff.

[0042] Figure Labels

[0043] 1. Microbial in-situ reactor

[0044] 11 First water inlet pipe

[0045] 12 First water outlet pipe

[0046] 2. Subsurface flow wetlands

[0047] 21 Subsurface Wetland Section

[0048] 211 Planting Area

[0049] 212 Packing Zone

[0050] 22. Water distribution canal

[0051] 23 Second water outlet pipe

[0052] 3. Booster Pump

[0053] 4. Equalization tank

[0054] 41 Second water inlet pipe

[0055] 5. Filter components

[0056] 6 Observation Wells

[0057] 7. Sewage replacement pump

[0058] 8 Valve wells Detailed Implementation

[0059] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0060] like Figure 1 As shown, a subsurface flow wetland system for treating wastewater includes a microbial in-situ reactor 1 and a subsurface flow wetland 2. The microbial in-situ reactor 1 is connected to the subsurface flow wetland 2. The microbial in-situ reactor 1 is a reactor that utilizes pollutants in the polluted water as a nutrient source in situ.

[0061] In a preferred embodiment, the subsurface flow wetland includes a connected subsurface flow wetland section 21 and a water distribution channel 22, and the microbial in-situ reactor 1 is connected to the water distribution channel 22 and the subsurface flow wetland section 21 respectively.

[0062] In a preferred embodiment, it further includes at least one of the following technical features:

[0063] a1) The subsurface wetland section 21 includes a planting area 211 and a filler area 212. The aquatic plants in the planting area 211 are all provided by the production base of Shanghai Shanheng Ecological Technology Co., Ltd. The emergent plants are mainly aquatic canna, umbrella grass and loosestrife, and the submerged plants are cold-resistant dwarf evergreen eelgrass.

[0064] a2) The microbial in-situ reactor 1 is provided with a first inlet pipe 11 and a first outlet pipe 12. The microbial in-situ reactor 1 is connected to the water distribution channel 22 through the first inlet pipe 11, and the microbial in-situ reactor 1 is connected to the subsurface flow wetland section 21 through the first outlet pipe 12.

[0065] a3) The system further includes a booster pump 3, which is installed on the pipeline between the in-situ microbial reactor 1 and the water distribution channel 22. The outflow rate of the in-situ microbial reactor is 220-280 L / h, for example: 220-210 L / h, 210-220 L / h, 220-230 L / h, 230-240 L / h, 240-250 L / h, 250-260 L / h, 260-270 L / h, 270-280 L / h; the booster pump 3 has a lifting capacity of 5.5-6.5 m³. 3 / h, for example: 5.5-6.0m 3 / h, 6.0-6.5m 3 / h etc.

[0066] a4) The subsurface wetland section 21 is equipped with a second outlet pipe 23.

[0067] In a preferred embodiment, it further includes at least one of the following technical features:

[0068] b1) In feature a1), the filling area 212 includes, from top to bottom, a river sand layer, a geotextile layer, a filling layer, a protective layer, and an impermeable layer;

[0069] b2) The filler layer is made of silicate ceramic particles with a diameter range of 10-50 mm. The silicate ceramic particles are prepared by the method described in patent number ZL 201110253738.5, and their φ range can be 10-15 mm, 15-20 mm, 20-25 mm, 25-30 mm, 30-35 mm, 35-40 mm, 40-45 mm, or 45 mm-50 mm. They have high porosity, large specific surface area, high decontamination efficiency, and are not easily clogged. They are provided by Nanjing University of Science and Technology and are mainly used in horizontal subsurface flow constructed wetlands.

[0070] In a preferred embodiment, it further includes at least one of the following technical features:

[0071] c1) The microbial in-situ reactor 1 described herein contains microorganisms and nutrients;

[0072] c2) The system also includes a regulating pool 4, which is connected to the subsurface flow wetland 2.

[0073] In a preferred embodiment, it further includes at least one of the following technical features:

[0074] d1) The system also includes a filter element 5, which is located at the water inlet of the equalization tank 4;

[0075] The system also includes an observation well 6, which is located on the regulating tank 4;

[0076] d2) The system also includes a submersible sewage pump 7, and the regulating tank 4 is connected to the submersible flow wetland 2 via the submersible sewage pump 7. The model number of the sewage pump is WQD6-12-0.55L1.

[0077] d3) The regulating tank 4 is equipped with a second water inlet pipe 41.

[0078] In a preferred embodiment, it further includes at least one of the following technical features:

[0079] In feature d1), the filter component 5 is a hanging basket grid;

[0080] In feature d31), the system further includes a valve well 8, which contains one or more valves located on the pipe connecting the submersible pump 7 and the submersible wetland 2.

[0081] Example 1

[0082] This embodiment provides a subsurface flow wetland wastewater treatment system, as shown in the figure. It includes a microbial in-situ reactor 1 and a subsurface flow wetland 2. The microbial in-situ reactor 1 is connected to the subsurface flow wetland 2 and utilizes pollutants in the polluted water as a nutrient source in situ. The subsurface flow wetland includes a connected subsurface flow wetland section 21 and a distribution channel 22. The microbial in-situ reactor 1 is connected to both the distribution channel 22 and the subsurface flow wetland section 21. The microbial in-situ reactor 1 is equipped with a first inlet pipe 11 and a first outlet pipe 12. The microbial in-situ reactor 1 is connected to the distribution channel 22 via the first inlet pipe 11 and to the subsurface flow wetland section 21 via the first outlet pipe 12. The system also includes a lift pump 3, which is located on the pipeline between the microbial in-situ reactor 1 and the distribution channel 22. The subsurface flow wetland section 21 is equipped with a second outlet pipe 23. An equalization tank 4 is included, which is connected to the subsurface flow wetland 2 and is equipped with a second inlet pipe 41. The system also includes a filter component 5, which is a hanging basket grille. The hanging basket grille has a stainless steel wire mesh structure with a mesh size of 0.9-1.1 cm, preferably 1 cm. The hanging basket grille has a long service life and is easy to remove and clean. The filter component 5 is located at the water inlet of the equalization tank 4. Rainwater enters the equalization tank 4 from the second inlet pipe 41 through the hanging basket grille 5. The rainwater undergoes pretreatment by the hanging basket grille 5, which can intercept larger debris. The system also includes an observation well 6, which is located on the regulating tank 4, facilitating regular inspection, cleaning, dredging, or downhole operations. The system also includes a submersible sewage pump 7, which connects the regulating tank 4 to the submersible flow wetland 2. Pretreated rainwater in the regulating tank enters the distribution channel 10 via the submersible sewage pump 9, and then enters the microbial in-situ reactor 8 through the first inlet pipe 11 via the lift pump 10. The microbial in-situ reactor 8 contains microorganisms and nutrients. When rainwater passes through the microbial in-situ reactor 1, the activated high-concentration, high-activity microbial agent can be added to the submersible flow wetland section 21 through the first outlet pipe 12. The rainwater passing through the microbial in-situ reactor increases the solubility of rainwater and rapidly increases the content and activity of microorganisms in the system, thereby improving the system's efficiency in treating pollutants. The subsurface flow wetland section 21 includes a filler zone 212 and a planting zone 211. The planting zone mainly grows pollution-resistant plants that absorb nutrients through their roots. The filler zone 212 consists of a natural river sand layer, geotextile, filler layer, protective layer, and a two-layer geotextile and one-layer membrane seepage-proof layer from top to bottom. The filler layer is composed of specially made silicate ceramsite, which is prepared according to the method in patent number ZL 201110253738.5. The silicate ceramsite ranges from φ10 to 50 mm. This silicate particle has high porosity and large specific surface area, which can adsorb a large amount of nutrients and also act as a microbial carrier. It can efficiently remove nutrients from the water and is not easy to clog, greatly improving the rainwater purification efficiency. Finally, the effluent meets the standards and is discharged into the surface water body through the second outlet pipe 23.

[0083] This embodiment provides a method for treating wastewater using a subsurface flow wetland. The system described above includes the following steps: 1) Activating a first wastewater to be treated in the presence of microorganisms to obtain a first treatment mixture; 2) Passing the first treatment mixture into a subsurface flow wetland 2, and treating a second wastewater to be treated with the first treatment mixture to obtain treated wastewater. The wastewater to be treated is initially settled and regulated before being separated into the first wastewater to be treated and the second wastewater to be treated. The microorganisms include nitrifying bacteria, nitrite-oxidizing bacteria, denitrifying bacteria, Bacillus subtilis, Bacillus mucilaginosus and its products, Bacillus megaterium, Lactobacillus plantarum, Candida utilis, and Nocardia fibrosis. The mass ratio of each component in the microorganisms is: 1.0:0.8±0.03:1.0±0.03:1.5±0.15:1.5±0.17:1.2±0.12:0.7±0.05:1.0±0.07 The nutrient solution has the following mass fractions: corn flour 50.3%–59.7%, sucrose 13.1%–16.9%, cellulose 21.8%–26.2%, ammonium sulfate 0.89%–1.11%, magnesium sulfate heptahydrate 0.69%–0.81%, magnesium nitrate 0.69%–0.81%, ferrous sulfate 1.85%–2.15%, potassium dihydrogen phosphate 0.67%–0.83%, and sodium ammonium hydrogen phosphate 0.71%–0.79%; the ratio of microorganisms to nutrient solution is 96:1–120:1.

[0084] Example 2

[0085] Wastewater flows from the second inlet pipe 41 at a speed of 6.0m. 3 The wastewater enters the equalization tank 4 at a flow rate of / h for primary sedimentation. The wastewater is then pumped from the equalization tank 4 to the submersible flow wetland 2 by a submersible pump 7. The submersible pump 7 is controlled by a level controller. When the water level in the equalization tank 4 is insufficient, a low-water-level compensation system automatically activates the greywater supply. After being pumped by the lift pump 3, the wastewater is divided into two parts: the first wastewater entering the in-situ microbial reactor 1 and the second wastewater remaining in the submersible flow wetland 2. The first wastewater is used to activate microorganisms with the help of nutrients to obtain a first treated mixture. This first treated mixture is then introduced into the submersible flow wetland 2, where the second wastewater is treated. After 50.4 hours of treatment in the submersible flow wetland 2, the treated wastewater is obtained.

[0086] 500 mL samples were taken from the regulating tank 4, the subsurface flow wetland 2, and the second outlet pipe 23, and stored in brown glass bottles. The samples were sent to a professional laboratory for water quality analysis within 30 minutes. The testing frequency was once a month, and three parallel samples were taken from each sample.

[0087] Total nitrogen (TN) was determined by alkaline potassium persulfate digestion ultraviolet spectrophotometry (GB18194-1989), ammonia nitrogen (NH4+-N) was determined by Nessler spectrophotometry (HJ535-2009), total phosphorus (TP) was determined by ammonium molybdate spectrophotometry (GB / T 11893-1989), and chemical oxygen demand (CODCr) was determined by potassium dichromate method (GB11914-1989).

[0088] TN stands for Total Nitrogen. TN refers to the total amount of inorganic and organic nitrogen in water, including inorganic nitrogen such as NO3-, NO2-, and NH4+, and organic nitrogen such as proteins, amino acids, and organic amines. It is calculated in milligrams of nitrogen per liter of water. It is often used to indicate the degree of nutrient pollution in water bodies.

[0089] TP stands for Total Phosphorus. British TP refers to the result of measuring phosphorus in a water sample after digestion, converting various forms of phosphorus into orthophosphate, and is measured in milligrams of phosphorus per liter of water sample.

[0090] Ammonia nitrogen (NH4+-N) is the sum of non-ionic and ionic ammonia.

[0091] CODcr is the chemical oxygen demand measured using potassium dichromate (K₂Cr₂O₇) as an oxidant, also known as the dichromate index. It is the chemical oxygen demand measured in a strongly acidic solution using potassium dichromate as the oxidant. The standard procedure for determining the chemical oxygen demand of water using potassium dichromate as the oxidant involves adding excess potassium dichromate solution and sulfuric acid to the water sample, heating, and using silver sulfate as a catalyst to complete the oxidation reaction. Excess potassium dichromate is back-titrated with ferrous sulfate standard solution using ferrous sulfate as an indicator, and the potassium dichromate consumption is then converted to milligrams of oxygen consumed per liter of water. This method offers a high degree of oxidation and can be used to analyze heavily polluted industrial wastewater, illustrating the extent of organic pollution in the wastewater.

[0092] like Figure 2As shown, the overall trend of TP content changes in the process water of each process in the constructed wetland system is as follows: (1) The TP concentration in the water of the equalization tank 4 ranges from 0.26 to 0.37 mg / L, the total phosphorus concentration after treatment by the subsurface flow wetland 2 ranges from 0.01 to 0.09 mg / L, and the TP concentration in the water discharged from the second effluent pipe 23 ranges from 0.01 to 0.07 mg / L. (2) During the same period, the TP concentration of different processes is: equalization tank 4 > subsurface flow wetland 2 > second effluent pipe 23, indicating that each process in the constructed wetland system has a certain removal effect on TP in the influent. (3) The total phosphorus concentration in the influent is significantly higher than that in the effluent, indicating that the constructed wetland system has a good removal effect on total phosphorus, and the removal effect is relatively stable. (4) With the change of time, the TP removal rate shows a trend of first increasing and then stabilizing, with a removal rate range of 80.0% to 97.3%, the highest removal effect being 97.3%, and the average removal rate being 94.1%.

[0093] like Figure 3 As shown, the overall trend of TN content changes in the process water of each process in the constructed wetland system is as follows: (1) The TN mass concentration range of the water in the equalization tank 4 is 4.21-4.83 mg / L, the TN mass concentration range after treatment by the subsurface flow wetland 2 is 0.82-1.95 mg / L, and the TN mass concentration range at the second effluent pipe 23 is 0.66-1.77 mg / L. (2) During the same period, the TN mass concentration of different processes is: equalization tank 4 > subsurface flow wetland 2 > second effluent pipe 23, indicating that each process in the constructed wetland system has a certain removal effect on TN in the influent. (3) The TN mass concentration of the influent is significantly higher than that of the effluent, indicating that the constructed wetland system has a good removal effect on TN, and the removal effect is relatively stable. (4) With the change of time, the TN removal rate shows a trend of first increasing and then stabilizing, with a removal rate range of 62.6%-86.3%, the highest removal effect being 86.3%, and the average removal rate being 78.7%.

[0094] like Figure 4As shown, the overall trend of NH4+-N content changes in the process water of each process in the constructed wetland system is as follows: (1) During the same period, the NH4+-N mass concentration of different processes is: content in equalization tank 4 > content in subsurface flow wetland 2 > content in second effluent pipe 23, indicating that each process in the constructed wetland system has a certain removal effect on NH4+-N in the influent. (2) The NH4+-N mass concentration range of the water in equalization tank 4 is 2.51~2.80mg / L, the NH4+-N mass concentration range after treatment by subsurface flow wetland 2 is 0.09~0.74mg / L, and the NH4+-N mass concentration range of the effluent from the second effluent pipe 23 is 0.03-0.63mg / L. (3) The NH4+-N mass concentration in the influent is significantly higher than that in the effluent, indicating that the constructed wetland system has a good removal effect on NH4+-N and the removal effect is relatively stable. (4) Over time, the removal rate of NH4+-N showed a trend of first increasing and then stabilizing, with a range of 77.5%-99.3%, the highest removal efficiency being 99.3%, and an average removal rate of 93.6%.

[0095] like Figure 5 As shown, the overall trend of CODCr content changes in the process water of each process in the constructed wetland system is as follows: (1) During the same period, the CODCr concentration of different processes is basically: equalization tank 4 > subsurface flow wetland 2 > second effluent pipe 23, indicating that each process in the constructed wetland system has a certain removal effect on CODCr in the influent, and the removal effect is relatively stable. (2) The CODCr concentration range of the water in equalization tank 4 is 90.2~127.6mg / L, the CODCr concentration range after treatment by subsurface flow wetland 2 is 3.0~29.5mg / L, and the CODCr concentration range of the effluent from the second effluent pipe 23 is 2.1-25.2mg / L. (3) The CODCr concentration of the influent is significantly higher than that of the effluent, indicating that the constructed wetland system has a good removal effect on CODCr, and the removal effect is relatively stable. (4) Over time, the CODCr removal rate showed a trend of first increasing and then stabilizing, with a range of 77.8%-98.1%, the highest removal efficiency being 98.3%, and an average removal rate of 89.7%.

[0096] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any form or substance. It should be noted that those skilled in the art can make various improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention. Any modifications, alterations, and equivalent changes made by those skilled in the art based on the above-disclosed technical content without departing from the spirit and scope of the present invention are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for treating wastewater using subsurface flow wetlands, characterized in that, The system used in this method includes a microbial in-situ reactor (1) and a subsurface flow wetland (2), wherein the microbial in-situ reactor (1) is connected to the subsurface flow wetland (2); the subsurface flow wetland includes a connected subsurface flow wetland section (21) and a water distribution channel (22), and the microbial in-situ reactor (1) is connected to the water distribution channel (22) and the subsurface flow wetland section (21) respectively; the subsurface flow wetland section (21) includes a planting area (211) and a filling area (212); the microbial in-situ reactor (1) is provided with a first inlet pipe (11) and a first outlet pipe (12), the microbial in-situ reactor (1) is connected to the water distribution channel (22) via the first inlet pipe (11), and the microbial in-situ reactor (1) is connected to the subsurface flow wetland section (21) via the first outlet pipe (12); The filling zone (212) includes, from top to bottom, a river sand layer, a geotextile layer, a filling layer, a protective layer, and an impermeable layer; the material of the filling layer is silicate ceramsite, and the diameter of the silicate ceramsite ranges from 10 to 50 mm; the microbial in-situ reactor (1) is filled with microorganisms and nutrients; the treatment method includes the following steps: 1) the wastewater to be treated is initially settled and stored and then divided into the first wastewater to be treated and the second wastewater to be treated. The first wastewater to be treated is used to activate microorganisms under the action of nutrients to obtain the first treatment mixture; 2) the first treatment mixture is introduced into the subsurface flow wetland (2), and the second wastewater to be treated is treated by the first treatment mixture to obtain the treated wastewater; the microbial in-situ reactor (1) increases the dissolved oxygen in the water and also increases the content and activity of microorganisms in the system.

2. The method for treating wastewater using subsurface flow wetlands according to claim 1, characterized in that, It also includes at least one of the following technical features: a1) The system also includes a booster pump (3), which is located on the pipeline between the microbial in-situ reactor (1) and the water distribution channel (22); a2) The subsurface wetland section (21) is equipped with a second outlet pipe (23).

3. The method for treating wastewater using subsurface flow wetlands according to claim 1, characterized in that, The system also includes a regulating pool (4), which is connected to the subsurface wetland (2).

4. The method for treating wastewater using subsurface flow wetlands according to claim 3, characterized in that: It also includes at least one of the following technical features: d1) The system also includes a filter element (5), which is located at the water inlet of the equalization tank (4); The system also includes an observation well (6), which is located on the regulating tank (4); d2) The system also includes a submersible sewage pump (7), and the regulating tank (4) is connected to the submersible flow wetland (2) via the submersible sewage pump (7); d3) The regulating tank (4) is equipped with a second water inlet pipe (41).

5. The method for treating wastewater using subsurface flow wetlands according to claim 4, characterized in that, It also includes at least one of the following technical features: In feature d1), the filter element (5) is a hanging basket grid; In feature d21), the system further includes a valve well (8), which is provided with one or more valves, which are located on the pipeline connecting the submersible pump (7) and the submersible wetland (2).

6. The method for treating wastewater using subsurface flow wetlands according to claim 1, characterized in that, It includes at least one of the following technical features: e1) The microorganisms include nitrifying bacteria, nitrite-oxidizing bacteria, denitrifying bacteria, Bacillus subtilis, Bacillus mucilaginosus and its products, Bacillus megaterium, Lactobacillus plantarum, Candida utilis, and Nocardia fibrosis; the mass ratio of each component in the microorganisms is: 1.0:0.8±0.03:1.0±0.03:1.5±0.15:1.5±0.17:1.2±0.12:0.7±0.05:1.0±0.07:1.0±0.10; e2) The nutrient solution has the following mass fractions: corn flour 50.3%~59.7%, sucrose 13.1%~16.9%, cellulose 21.8%~26.2%, ammonium sulfate 0.89%~1.11%, magnesium sulfate heptahydrate 0.69%~0.81%, magnesium nitrate 0.69%~0.81%, ferrous sulfate 1.85%~2.15%, potassium dihydrogen phosphate 0.67%~0.83%, and sodium ammonium hydrogen phosphate 0.71%~0.79%, with the total mass fraction of all components being 100%.

7. The method for treating wastewater using subsurface flow wetlands according to claim 1, characterized in that, The ratio of microorganisms to nutrients is 96:1 to 120:1.

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