Wastewater treatment system and method

Abstract

The present application relates to sewage treatment technical field, specifically to a kind of sewage treatment system and method, the sewage treatment system includes first wetland treatment unit, second wetland treatment unit and third wetland treatment unit, first wetland treatment unit includes multiple interval arrangement processing component, processing component periodically fills sewage, and first sewage is formed by treating sewage through aerobic reaction, second wetland treatment unit includes bending section, bending section includes bending wall and adsorption layer, adsorption layer covers on bending wall, first sewage flows along the extension direction of bending section, the dissolved oxygen concentration of second wetland treatment unit is less than the dissolved oxygen concentration of first wetland treatment unit and greater than third wetland treatment unit, third wetland treatment unit receives the sewage after second wetland treatment unit processing and carries out anaerobic reaction, the sewage treatment system of the present application embodiment, greenhouse gas emissions is reduced while improving the treatment capacity of sewage by artificial wetland cascade treatment sewage.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and more specifically, to a wastewater treatment system and method. Background Technology

[0002] Tidal flow constructed wetlands utilize the pore suction generated by the tidal movement of the wetland bed's saturated surface to draw oxygen from the atmosphere into the bed, greatly improving oxygen transport and utilization. Constructed wetlands are frequently used for wastewater treatment; however, they generate significant amounts of greenhouse gases in low-oxygen or anoxic environments, leading to excessive greenhouse gas emissions. Summary of the Invention

[0003] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a wastewater treatment system that can adjust the cycle time of a first wetland treatment unit and extend the residence time of wastewater in a second wetland treatment unit. By treating wastewater in stages through constructed wetlands, the system improves wastewater treatment capacity while reducing greenhouse gas emissions.

[0004] This invention also proposes a wastewater treatment method.

[0005] The wastewater treatment system of this invention includes: a first wetland treatment unit, which is a tidal flow constructed wetland, comprising multiple treatment components arranged at intervals, wherein the treatment components are periodically filled with wastewater and the wastewater is treated through an aerobic reaction to form first wastewater; a second wetland treatment unit, which is a subsurface flow constructed wetland, wherein the dissolved oxygen concentration of the second wetland treatment unit is lower than that of the first wetland treatment unit, the second wetland treatment unit includes at least one bend section, the bend section including a bend wall and an adsorption layer, the adsorption layer covering the bend wall, the first wastewater flowing along the extension direction of the bend section, and the adsorption layer adsorbing impurities in the first wastewater; and a third wetland treatment unit, which is a horizontal constructed wetland, wherein the dissolved oxygen concentration of the third wetland treatment unit is lower than that of the second wetland treatment unit, and the third wetland treatment unit is used to receive the wastewater treated by the second wetland treatment unit and perform an anaerobic reaction.

[0006] The wastewater treatment system of this invention can adjust the cycle time of the first wetland treatment unit and extend the residence time of wastewater in the second wetland treatment unit, thereby improving the wastewater treatment capacity while reducing greenhouse gas emissions.

[0007] In some embodiments, the processing assembly includes a frame, an inlet pipe, and an outlet pipe. The frame is filled with a first filler layer. One end of both the inlet pipe and the outlet pipe is located within the first filler layer. One end of the inlet pipe and one end of the outlet pipe are spaced apart in the height direction of the frame, and the outlet pipe is higher than the inlet pipe.

[0008] In some embodiments, the frame is provided with through holes, and the first filler layer includes pebbles, modified clay and zeolite arranged sequentially from bottom to top.

[0009] In some embodiments, the second wetland treatment unit further includes a second packing layer, which includes pebbles, modified slag and zeolite arranged sequentially from bottom to top, and the bent section is arranged vertically in the second packing layer to change the flow direction of the first sewage.

[0010] In some embodiments, the third wetland treatment unit includes a third filler layer, which includes pebbles, modified slag and zeolite arranged sequentially from bottom to top, and the height of the first filler layer is greater than or equal to that of the second filler layer, and the height of the second filler layer is greater than that of the third filler layer.

[0011] In some embodiments, the third wetland treatment unit includes a first outlet and a second outlet, the first outlet being connected to the first wetland treatment unit to form a first reflux, and the second outlet being used to discharge the water treated by the third wetland treatment unit.

[0012] In some embodiments, the wastewater treatment system further includes a membrane unit having a first inlet, a fourth outlet, and a fifth outlet, and the third wetland treatment unit further includes a third outlet. The first inlet is connected to the third outlet, the fourth outlet is connected to the first wetland treatment unit to form a second reflux, and the fifth outlet is used to discharge the water treated by the membrane unit.

[0013] In some embodiments, the first wetland treatment unit, the second wetland treatment unit, and the third wetland treatment unit are each equipped with a gas collection box and a dissolved oxygen meter. The gas collection box is used to collect greenhouse gases emitted by the wetland treatment unit, and the dissolved oxygen meter measures the dissolved oxygen concentration of the wetland to adjust the cycle time of the first wetland treatment unit.

[0014] In some embodiments, the wastewater treatment system further includes a photocatalytic reactor, one end of which is connected to the second wetland treatment unit and the other end of which is connected to the third wetland treatment unit.

[0015] In some embodiments, the wastewater treatment system further includes an equalization tank connected to the inlet of the first wetland treatment unit, the equalization tank being used to regulate the quantity and quality of wastewater.

[0016] The wastewater treatment method of this invention includes:

[0017] Wastewater is periodically filled into the first wetland treatment unit for aerobic reaction to form the first wastewater, wherein the first wetland treatment unit is a tidal flow artificial wetland;

[0018] The first wastewater flows along the extension direction of the bend section of the second wetland treatment unit to adsorb impurities in the first wastewater. The second wetland treatment unit is a subsurface flow constructed wetland. The second wetland treatment unit includes at least one bend section, the bend section includes a bend wall and an adsorption layer, the adsorption layer covers the bend wall, and the dissolved oxygen concentration of the second wetland treatment unit is less than the dissolved oxygen concentration of the first wetland treatment unit.

[0019] The wastewater treated by the second wetland treatment unit is transferred to the third wetland treatment unit for anaerobic reaction. The third wetland treatment unit is a horizontal constructed wetland, and the dissolved oxygen concentration of the third wetland treatment unit is lower than that of the second wetland treatment unit.

[0020] The wastewater treatment method of this invention can adjust the cycle time of the first wetland treatment unit and extend the residence time of wastewater in the second wetland treatment unit, thereby improving the wastewater treatment capacity while reducing greenhouse gas emissions. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a wastewater treatment system according to an embodiment of the present invention.

[0022] Figure 2 This is a schematic diagram of the first wetland treatment unit according to an embodiment of the present invention.

[0023] Figure 3 This is a schematic diagram of the second wetland treatment unit according to an embodiment of the present invention.

[0024] Figure 4 This is a schematic diagram of the third wetland treatment unit in an embodiment of the present invention.

[0025] Figure label:

[0026] First wetland treatment unit 1, treatment component 11, frame 111, inlet pipe 112, outlet pipe 113, first packing layer 114, lifting lug 115.

[0027] Second wetland treatment unit 2, bending section 21, second filler layer 22, wall 23.

[0028] The third wetland treatment unit 3, the third filler layer 31, the steel frame 32, the plants 33, the gas collection box 4, the water collection channel 5, the pebbles 6, the modified clay 7, the zeolite 8, and the modified slag 9. Detailed Implementation

[0029] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0030] The wastewater treatment system of this invention includes a first wetland treatment unit 1, a second wetland treatment unit 2, and a third wetland treatment unit 3. The first wetland treatment unit 1 is a tidal flow constructed wetland, comprising multiple treatment components 11 arranged at intervals. Each treatment component 11 is periodically filled with wastewater, which is then treated through an aerobic reaction to form first wastewater. The second wetland treatment unit 2 is a subsurface flow constructed wetland, with a lower dissolved oxygen concentration than the first wetland treatment unit 1. The second wetland treatment unit 2 includes at least one bent section 21, comprising a bent wall and an adsorption layer. The adsorption layer covers the bent wall, and the first wastewater flows along the extension direction of the bent section 21. The adsorption layer can adsorb impurities in the first wastewater. The third wetland treatment unit 3 is a horizontal constructed wetland, with a lower dissolved oxygen concentration than the second wetland treatment unit 2. The third wetland treatment unit 3 receives the wastewater treated by the second wetland treatment unit 2 and performs an anaerobic reaction.

[0031] It should be noted that tidal flow constructed wetlands utilize the pore suction generated by the tidal movement of the bed's saturated wetting surface to draw oxygen from the atmosphere into the bed, significantly increasing the oxygen transport and utilization rate within the wetland bed, thereby enhancing the wetland's purification effect on pollutants. The wastewater treatment system in this embodiment can be applied to the removal of pollutants from effluent in industrial parks.

[0032] Specifically, such as Figures 1-3 As shown, the tidal flow constructed wetland alternately fills and empties the wetland bed with sewage, which increases the oxygenation capacity of the tidal flow constructed wetland and forms a highly efficient oxygen-rich zone. Multiple treatment components 11 are arranged at intervals to form the wetland bed. The interval arrangement of multiple treatment components 11 is conducive to the uniform distribution and flow of sewage, and also conducive to the transport and diffusion of oxygen.

[0033] The first wetland treatment unit 1 and the second wetland treatment unit 2 are arranged at intervals in the left-right direction. The first wastewater treated by the first wetland treatment unit 1 is transferred to the second wetland treatment unit 2 through the collection channel 5. Since the dissolved oxygen concentration in the second wetland treatment unit 2 is lower than that in the first wetland treatment unit 1, the first wastewater can continue to react in the second wetland treatment unit 2. Since the second wetland treatment unit 2 is provided with a bending section 21, the first wastewater first flows along the extension direction of the bending section 21, and then the flow direction of the first wastewater is changed under the action of the bending section 21. The setting of the bending section 21 can increase the water retention time, thereby increasing the reaction time between the first wastewater and the second wetland treatment unit 2, thereby improving the denitrification capacity of the second wetland treatment unit 2.

[0034] After the first wastewater undergoes sufficient reaction in the second wetland treatment unit 2, it flows to the third wetland treatment unit 3, where it mainly undergoes anaerobic reaction. Through the combination of aerobic and anaerobic reactions, organic matter and nitrogen in the wastewater can be removed more effectively, thus improving the efficiency and quality of wastewater treatment.

[0035] It is understandable that the greenhouse gases emitted by wetland treatment units are mainly methane and nitrous oxide. Methane is the main product under anaerobic conditions, while nitrous oxide is produced during both nitrification and denitrification. By controlling and adjusting the dissolved oxygen concentration of the tidal flow constructed wetland, greenhouse gas emissions during aerobic and anoxic reactions can be reduced. Specific settings need to be adjusted according to the wastewater quality and quantity.

[0036] For example, the hydraulic load of the first wetland treatment unit 1 is 200-300 L / m².d, and the retention time is 2-3 days; the hydraulic load of the second wetland treatment unit 2 is 150-250 L / m².d, and the retention time is 2-3 days; the hydraulic load of the third wetland treatment unit 3 is less than or equal to 100 L / m².d, and the retention time is 0.5 days.

[0037] Wastewater undergoes primarily aerobic reactions in the first wetland treatment unit 1, but some anaerobic reactions also occur. The wastewater is treated through aerobic reactions to form the first wastewater. The first wastewater undergoes primarily aerobic reactions in the second wetland treatment unit 2. In other words, the first wastewater undergoes both aerobic and anaerobic reactions in the second wetland treatment unit 2.

[0038] The wastewater treatment system of this invention first introduces wastewater into a first wetland treatment unit 1 for aerobic reaction to remove organic matter and some ammonia nitrogen. The wastewater is then transferred to a second wetland treatment unit 2 for a secondary aerobic reaction. The first and second wetland treatment units 1 and 2 form a composite constructed wetland, creating better conditions for the anoxic reaction in a third wetland treatment unit 3. The wastewater treated in the second wetland treatment unit 2 is then transferred to the third wetland treatment unit 3 for anaerobic reaction. By adjusting the cycle time of the tidal flow constructed wetland, the dissolved oxygen concentration in the tidal flow constructed wetland can be adjusted. Combined with the aerobic and anaerobic reactions, the constructed wetland achieves tiered wastewater treatment, which can more effectively remove organic matter and nitrogen from the wastewater, improve the treatment capacity of the wetland treatment unit, and reduce greenhouse gas emissions.

[0039] Furthermore, in this embodiment, a three-stage wetland treatment unit is set up. Based on the dissolved oxygen concentration gradient, the first wetland treatment unit 1 adopts a water-filling reaction-drainage and idle method, which has an oxygenation capacity 8-10 times higher than that of ordinary wetlands, forming an oxygen-rich zone. Combined with the relatively anoxic zone of the second wetland treatment unit 2 and the anaerobic reaction of the third wetland treatment unit 3, a composite wetland is constructed to achieve a biochemical treatment effect similar to A / O, optimize the sewage treatment process, and reduce greenhouse gas emissions.

[0040] In some embodiments, the processing component 11 includes a frame 111, an inlet pipe 112, and an outlet pipe 113. The frame 111 is filled with a first filler layer 114. One end of the inlet pipe 112 and the outlet pipe 113 are both located in the first filler layer 114. One end of the inlet pipe 112 and one end of the outlet pipe 113 are spaced apart in the height direction of the frame 111, and the outlet pipe 113 is higher than the inlet pipe 112.

[0041] Specifically, such as Figure 2 As shown, the treatment components 11 are arranged in a matrix. The treatment components 11 alternately fill and empty the sewage. The lower ends of the inlet pipe 112 and the outlet pipe 113 are both located inside the first packing layer 114, so that the sewage enters the first packing layer 114 from below and flows out of the first packing layer 114 from above. This facilitates the absorption and filtration of pollutants in the sewage by the first packing layer 114, thereby improving the treatment capacity of the first wetland treatment unit 1.

[0042] Optionally, the treatment component 11 also includes an impermeable layer and lifting ears 115. The impermeable layer is located below the frame 111 and is made of HDPE membrane to prevent sewage from seeping downwards. The lifting ears 115 are located above the frame 111 for easy installation.

[0043] For example, the frame 111 is made of polyethylene. The frame 111 has dimensions of 1m × 1m × 1.2m, and the spacing between two adjacent treatment components 11 is 1m-1.5m to facilitate the flow of wastewater and the transport of oxygen.

[0044] In some embodiments, the frame 111 is provided with through holes, and the first filler layer 114 includes pebbles 6, modified clay 7 and zeolite 8 arranged sequentially from bottom to top.

[0045] Specifically, such as Figure 2 As shown, the outlet end of the inlet pipe 112 is located inside the cobblestones 6, and the inlet end of the outlet pipe 113 is located inside the zeolite 8. The height ratio of the cobblestones 6, modified clay 7, and zeolite 8 in the first packing layer 114 is 1:2:1. The particle size of the first packing layer 114 gradually increases from bottom to top. The lower layer can absorb and filter larger molecular pollutants, while the upper layer can absorb and filter smaller pollutants.

[0046] In this embodiment, the size of the through hole is 0.2-0.3cm. By limiting the size of the through hole, the gap between the first packing layers 114 is also limited, so that the first packing layers 114 have a certain degree of looseness, which can better utilize the specific surface area of ​​the first packing layers 114 and improve the sewage treatment capacity of the first packing layers 114.

[0047] In some embodiments, the second wetland treatment unit 2 further includes a second packing layer 22, which includes pebbles 6, modified slag 9 and zeolite 8 arranged sequentially from bottom to top, and a bent section 21 is arranged vertically in the second packing layer 22 to change the flow direction of the first sewage.

[0048] Specifically, such as Figure 3 As shown, the second wetland treatment unit 2 also includes a wall 23, and a second filler layer 22 is filled between the wall 23 and the bending section 21. The height ratio of the pebbles 6, modified slag 9 and zeolite 8 in the second filler layer 22 is 0.5:0.25:0.25m.

[0049] In this embodiment, the second wetland treatment unit 2 includes two bent sections 21 arranged in parallel, extending in the front-to-back direction and spaced apart in the left-to-right direction. A gap is provided between the front end of the left bent section 21 and the front wall 23, and a gap is provided between the rear end of the right bent section 21 and the rear wall 23. This allows the first wastewater to flow forward along the left bent section 21, and then flow to the right bent section 21 under the obstruction of the front wall 23. It then flows backward along the right bent section 21, and finally flows to the right wall 23 under the obstruction of the rear wall 23, exiting the second wetland treatment unit 2. The bent sections 21 form a meandering flow channel, reducing dead zones and extending the reaction time between the first wastewater and the second wetland treatment unit 2. Furthermore, the bent sections 21 also include an adsorption layer, which can improve the treatment capacity of the second wetland treatment unit 2 and thus reduce greenhouse gas emissions.

[0050] In some embodiments, the third wetland treatment unit 3 includes a third filler layer 31, which includes pebbles 6, modified slag 9 and zeolite 8 arranged sequentially from bottom to top, and the height of the first filler layer 114 is greater than or equal to the height of the second filler layer 22, and the height of the second filler layer 22 is greater than that of the third filler layer 31.

[0051] Specifically, such as Figure 4 As shown, the wastewater treated by the second wetland treatment unit 2 enters the third treatment unit for anaerobic treatment. The third wetland treatment unit 3 includes a steel frame 32 and a third filling layer. The third filling layer is filled in the space enclosed by the steel frame 32. The height ratio of pebbles 6, modified slag 9 and zeolite 8 in the third filling layer 31 is 0.3:0.2:0.2m.

[0052] Optionally, plants 33 are planted on the third wetland treatment unit 3 to increase the wetland vegetation coverage area, which can improve the absorption capacity of wetland plants 33, increase the ornamental value and reduce greenhouse gas emissions.

[0053] For example, the height of the first packing layer 114 is between 1.5 and 2 m, the height of the second packing layer 22 is the same as the height of the first packing layer 114, or the height of the second packing layer 22 is between 1 and 1.5 m, and the height of the third packing layer 31 is between 0.5 and 0.8 m.

[0054] The wastewater treatment system of this invention sets up a first wetland treatment unit 1, a second wetland treatment unit 2, and a third wetland treatment unit 3 with successively decreasing heights, so that gravity flow is formed between different wetland treatment units, which can reduce the need for power devices and save energy.

[0055] In some embodiments, the third wetland treatment unit 3 includes a first outlet and a second outlet. The first outlet is connected to the first wetland treatment unit 1 to form a first reflux, and the second outlet is used to discharge the water treated by the third wetland treatment unit 3.

[0056] Specifically, such as Figure 1 As shown, the water treated by the third wetland treatment unit 3 can be directly discharged or returned to the first wetland treatment unit 1 for further treatment. The choice of which wetland treatment unit 3 to use depends on the actual situation. If the water treated by the third wetland treatment unit 3 reaches or exceeds Class IV surface water standards, it can be directly discharged. If the water treated by the third wetland treatment unit 3 does not reach or exceed Class IV surface water standards, it needs to be returned to the first wetland treatment unit 1 for further treatment to ensure that the water treated by the sewage treatment system meets the discharge requirements.

[0057] In some embodiments, the wastewater treatment system further includes a membrane unit having a first inlet, a fourth outlet and a fifth outlet, and the third wetland treatment unit 3 further includes a third outlet. The first inlet is connected to the third outlet, the fourth outlet is connected to the first wetland treatment unit 1 to form a second reflux, and the fifth outlet is used to discharge the water treated by the membrane unit.

[0058] Specifically, the water treated by the third treatment unit can flow to the membrane unit through the third outlet. Whether it enters the membrane unit depends on the actual water demand. For example, it may be used as landscape water replenishment or as greywater that needs to be treated by the membrane unit before reuse.

[0059] The second return flow is determined based on the membrane selected in the membrane unit. If the water treated by the membrane unit does not meet the requirements for reclaimed water reuse, it can be returned to the first wetland treatment unit 1 through the fourth outlet for further treatment to ensure that the water quality after treatment by the wastewater treatment system meets the standards. If the water treated by the membrane unit meets the requirements for reclaimed water reuse, it can be reused directly.

[0060] For example, the membrane unit employs microfiltration, ultrafiltration, and reverse osmosis. The microfiltration membrane pore size can be 1μm-3μm, the ultrafiltration membrane pore size can be 0.05-0.1μm, and the reverse osmosis membrane pore size can be 0.1nm, which can efficiently remove heavy metals. The reverse osmosis concentrate from the second reflux unit of the membrane unit is returned to the first wetland treatment unit 1, and the reverse osmosis recovery rate can be adjusted according to relevant operating data.

[0061] In some embodiments, the first wetland treatment unit 1, the second wetland treatment unit 2, and the third wetland treatment unit 3 are each equipped with a gas collection box 4 and a dissolved oxygen meter (not shown in the figure). The gas collection box 4 is used to collect greenhouse gases emitted by the wetland treatment unit, and the dissolved oxygen meter measures the dissolved oxygen concentration of the wetland to adjust the cycle time of the first wetland treatment unit 1.

[0062] Specifically, the greenhouse gases emitted by the wetland mainly include methane and nitrous oxide. These greenhouse gases are collected from each wetland treatment unit via gas collection box 4, and their concentrations are monitored. The dissolved oxygen concentration in each wetland treatment unit reflects its wastewater treatment capacity and effectiveness. By combining the greenhouse gas concentration with the dissolved oxygen concentration, the cycle time of the first wetland treatment unit 1 is adjusted to improve the treatment capacity and effectiveness of each wetland treatment unit.

[0063] For example, in the monitoring of the first wetland treatment unit 1 and the second wetland treatment unit 2, the CH4 concentration ranged from 0.5 to 5.2 mg / m³. 2 *h, N2O concentration is between 0.005-0.410 mg / m³ 2 *h; In the monitoring of the third wetland treatment unit 3, the CH4 concentration ranged from 0.05 to 16.8 mg / m³. 2 *h, N2O concentration is between 0.018 and 0.763 mg / m³ 2 When *h, it indicates that the greenhouse gas emissions of each wetland treatment unit are within the required range. If the methane and nitrous oxide emissions of the first wetland treatment unit 1 and / or the second wetland treatment unit 2 and / or the third wetland treatment unit 3 exceed the above range, the cycle time of the first wetland treatment unit 1 needs to be adjusted to adjust the treatment capacity of each wetland treatment unit, improve the wastewater treatment capacity, and keep the greenhouse gas emissions within the required range.

[0064] This invention, through the detection of greenhouse gas emissions and concentrations, adjusts the aeration frequency and recirculation ratio of the first wetland treatment unit 1 to achieve both improved pollutant removal and reduced carbon emissions.

[0065] In some embodiments, the wastewater treatment system further includes a photocatalytic reactor, one end of which is connected to the second wetland treatment unit 2, and the other end of which is connected to the third wetland treatment unit 3.

[0066] Specifically, the photocatalytic reactor can treat pollutants that are difficult to degrade in the first wetland treatment unit 1 and the second wetland treatment unit 2. Larger pollutants in the wastewater are removed by the first wetland treatment unit 1 and the second wetland treatment unit 2, and smaller pollutants in the wastewater are removed by the photocatalytic reactor, thereby improving the wastewater treatment capacity.

[0067] For example, the photocatalytic reactor is intermittent and uses modified titanium dioxide as the photocatalyst. The ratio of photocatalysis to adsorption is adjusted according to the water quality of the wastewater. It can efficiently remove refractory organic matter in the effluent of industrial parks. At the same time, it decomposes the difficult-to-remove large molecular organic matter into small molecular organic matter, thereby improving the biochemical effect of subsequent processes.

[0068] Optionally, the wastewater treated by the photocatalytic reactor flows to the third wetland treatment unit 3, which can treat the photocatalyst that may leak out during the photocatalysis process to ensure the wastewater treatment effect.

[0069] The wastewater treatment system of this invention comprehensively considers the diverse and complex characteristics of industrial park effluent pollutants. By setting up a three-stage constructed wetland coupled with a photocatalytic reactor, it can not only efficiently remove recalcitrant organic matter from the effluent, but also improve the park's landscape effect by planting plants 33 on the third wetland treatment unit 3. At the same time, by setting up a membrane unit after the third wetland treatment unit 3, different processes can be selected according to the needs of the park's water system, so that the effluent of the wastewater treatment system can meet or exceed the Class IV surface water discharge standard, or be directly used for industrial water or reclaimed water reuse in the park, achieving the goal of near-zero wastewater discharge in the park.

[0070] For example, the wastewater influent sequentially passes through the first wetland treatment unit 1, the second wetland treatment unit 2, the photocatalytic reactor, the third wetland treatment unit 3, and the membrane unit, with an influent flow rate of 1000 m³. 3 The daily concentrations were as follows: COD 60 mg / L, BOD5 20 mg / L, SS 20 mg / L, ammonia nitrogen 15 mg / L, TN 20 mg / L, TP 1 mg / L, and cadmium 1.5 mg / L. COD refers to the amount of reducing substances in a water sample that need to be oxidized, measured chemically. BOD5 is an important indicator of the degree of organic pollution in water bodies, indirectly expressed by the amount of dissolved oxygen consumed by microbial metabolism over a 5-day period. SS refers to the concentration of activated sludge in the mixed liquor. Ammonia nitrogen is a form of nitrogen in water and a significant pollutant contributing to eutrophication and environmental pollution. TN represents the total amount of inorganic and organic nitrogen in the wastewater. TP represents total phosphorus and is an important indicator for assessing phosphorus content in wastewater.

[0071] The filling-reaction-drainage idle ratio of the first wetland treatment unit 1 was 4:4 hours. The dissolved oxygen concentration detected by the dissolved oxygen meter in both the first and second wetland treatment units 1 and 2 was 3.5 mg / L. The volumes of CH4 and N2O collected by the gas collection box 4 were 4 m³ and 4 m³, respectively. 3 and 5m 3 The dissolved oxygen concentration detected by the dissolved oxygen meter in the third wetland treatment unit 3 was 1.2 mg / L, and the volumes of CH4 and N2O collected by the gas collection box were 7 m³ and 7 m³, respectively. 3 and 8.5m 3 The membrane unit has a reflux ratio of 70%, and the effluent standards are COD 15 mg / L, BOD5 10 mg / L, SS 3.5 mg / L, ammonia nitrogen 6 mg / L, TN 1.2 mg / L, TP 0.2 mg / L, and cadmium 0.02 mg / L.

[0072] In some embodiments, the wastewater treatment system further includes an equalization tank connected to the inlet of the first wetland treatment unit 1, the equalization tank being used to regulate the quantity and quality of the wastewater.

[0073] Specifically, by setting up an equalization tank before the first wetland treatment unit 1, the quantity and quality of wastewater are regulated to improve the uniformity of wastewater treatment.

[0074] The wastewater treatment method of this invention includes periodically filling a first wetland treatment unit with wastewater to form first wastewater through an aerobic reaction, wherein the first wetland treatment unit is a tidal flow constructed wetland; flowing the first wastewater along the extension direction of a bend section of a second wetland treatment unit to adsorb impurities in the first wastewater, wherein the second wetland treatment unit is a subsurface flow constructed wetland, the second wetland treatment unit includes at least one bend section, the bend section includes a bend wall and an adsorption layer, the adsorption layer covers the bend wall, and the dissolved oxygen concentration of the second wetland treatment unit is less than the dissolved oxygen concentration of the first wetland treatment unit; and transferring the wastewater treated by the second wetland treatment unit to a third wetland treatment unit for an anaerobic reaction, wherein the third wetland treatment unit is a horizontal constructed wetland, and the dissolved oxygen concentration of the third wetland treatment unit is less than the dissolved oxygen concentration of the second wetland treatment unit.

[0075] The wastewater treatment method of this invention involves first introducing wastewater into a first wetland treatment unit for aerobic reaction to remove organic matter and some ammonia nitrogen. The wastewater is then transferred to a second wetland treatment unit for a secondary aerobic reaction. The first and second wetland treatment units form a composite constructed wetland, creating better conditions for the anoxic reaction in a third wetland treatment unit. The wastewater treated in the second wetland treatment unit is then transferred to the third wetland treatment unit for anaerobic reaction. By adjusting the cycle time of the tidal flow constructed wetland, the dissolved oxygen concentration can be adjusted. Combined with the aerobic and anaerobic reactions, this method achieves tiered wastewater treatment via constructed wetlands, more effectively removing organic matter and nitrogen from the wastewater, improving the treatment capacity of the wetland treatment unit while reducing greenhouse gas emissions.

[0076] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0077] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0078] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0079] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first and second features are in direct contact, or that they are in indirect contact through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0080] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0081] It is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A sewage treatment system characterised in that, The application relates to a wetland treatment system, comprising: a first wetland treatment unit, which is a tidal flow constructed wetland, the first wetland treatment unit comprising a plurality of treatment assemblies, the plurality of treatment assemblies being arranged at intervals, the treatment assemblies being periodically filled with sewage, the sewage being treated by aerobic reaction to form first sewage; a second wetland treatment unit, which is a subsurface flow constructed wetland, the second wetland treatment unit having a lower dissolved oxygen concentration than the first wetland treatment unit, the second wetland treatment unit comprising at least one bending section, the bending section comprising a bending wall and an adsorption layer, the adsorption layer being arranged on the bending wall, the first sewage flowing along the extension direction of the bending section, the adsorption layer being capable of adsorbing impurities in the first sewage; a third wetland treatment unit, which is a horizontal flow constructed wetland, the third wetland treatment unit having a lower dissolved oxygen concentration than the second wetland treatment unit, the third wetland treatment unit being used for receiving the sewage treated by the second wetland treatment unit to perform anaerobic reaction; a photocatalytic reactor, one end of the photocatalytic reactor being connected to the second wetland treatment unit, the other end of the photocatalytic reactor being connected to the third wetland treatment unit; a membrane unit, the membrane unit having a first inlet, a fourth outlet and a fifth outlet, the third wetland treatment unit further comprising a third outlet, the first inlet being in communication with the third outlet, the fourth outlet being connected to the first wetland treatment unit to form a second backflow, the fifth outlet being used for discharging water treated by the membrane unit; the treatment assembly comprising a frame, a water inlet pipe and a water outlet pipe, the frame being filled with a first filler layer, one end of the water inlet pipe and one end of the water outlet pipe being located in the first filler layer, one end of the water inlet pipe being arranged at an interval from one end of the water outlet pipe in the height direction of the frame, the water outlet pipe being higher than the water inlet pipe, the frame being provided with a through hole, the first filler layer comprising, from bottom to top, cobblestones, modified clay and zeolite; the second wetland treatment unit further comprising a second filler layer, the second filler layer comprising, from bottom to top, cobblestones, modified slag and zeolite, the bending section being arranged vertically in the second filler layer to change the flow direction of the first sewage.

2. The sewage treatment system of claim 1, wherein, the third wetland treatment unit comprising a third filler layer, the third filler layer comprising, from bottom to top, cobblestones, modified slag and zeolite, the height of the first filler layer being greater than or equal to the height of the second filler layer, the height of the second filler layer being greater than the height of the third filler layer.

3. The sewage treatment system of claim 1, wherein, the third wetland treatment unit comprising a first outlet and a second outlet, the first outlet being connected to the first wetland treatment unit to form a first backflow, the second outlet being used for discharging water treated by the third wetland treatment unit.

4. The sewage treatment system of claim 1, wherein, The first wetland treatment unit, the second wetland treatment unit and the third wetland treatment unit are each provided with a gas collection tank and a dissolved oxygen meter, the gas collection tank is used to collect greenhouse gas discharged by the wetland treatment unit, and the dissolved oxygen meter measures the dissolved oxygen concentration of the wetland to adjust the cycle time of the first wetland treatment unit.

5. The sewage treatment system according to any one of claims 1-4, characterized in that, Further comprising a conditioning tank connected to the inlet end of the first wetland treatment unit, the conditioning tank is used to adjust the water quantity and water quality of the sewage.

6. A sewage treatment method of the sewage treatment system according to any one of claims 1 to 5, characterized by, Comprise: periodically filling the first wetland treatment unit with sewage to form first sewage, wherein the first wetland treatment unit is a tidal flow constructed wetland; flowing the first sewage along the extension direction of the bending section of the second wetland treatment unit to adsorb impurities in the first sewage, wherein the second wetland treatment unit is a subsurface flow constructed wetland, the second wetland treatment unit comprises at least one bending section, the bending section comprises a bending wall and an adsorption layer, the adsorption layer is covered on the bending wall, and the dissolved oxygen concentration of the second wetland treatment unit is less than that of the first wetland treatment unit; transmitting the sewage treated by the second wetland treatment unit to the third wetland treatment unit for anaerobic reaction, wherein the third wetland treatment unit is a horizontal constructed wetland, and the dissolved oxygen concentration of the third wetland treatment unit is less than that of the second wetland treatment unit.

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