Wastewater treatment system and method thereof

Abstract

The present application relates to a wastewater treatment system and a method thereof. The wastewater treatment system includes a carbon source tank, a constructed wetland, and a composite ditch; the composite ditch includes an upper ditch, a lower ditch, a first connecting pipe, a second connecting pipe, a first inlet valve, a first drain valve, a second inlet valve, and a second drain valve; the first connecting pipe is connected between the upper ditch and the upper part of the constructed wetland, and the second connecting pipe is connected between the lower ditch and the lower part of the constructed wetland; wherein, the composite ditch has a first mode and a second mode; in the first mode, the first inlet valve and the second drain valve are both closed, and the first drain valve and the second inlet valve are both open; in the second mode, the first inlet valve and the second drain valve are both open, and the first drain valve and the second inlet valve are both closed; the temperature of the wastewater in the first mode is lower than that in the second mode. The present application can improve the denitrification efficiency of the constructed wetland for wastewater under low temperature conditions.

Description

Technical Field

[0001] This application relates to the technical field of sewage treatment, and particularly to a wastewater treatment system and method for low carbon-nitrogen ratio wastewater. Background Art

[0002] With the intensification of water resource pollution, it is imperative to increase sewage treatment. As an economical and effective water treatment facility, constructed wetlands have low costs and are easy to maintain and operate. Constructed wetlands can be used to treat low carbon-nitrogen ratio wastewater such as the tail water of sewage treatment plants, low-pollution river water, urban surface runoff, and farmland runoff, mainly through the nitrification reaction of plants and the denitrification reaction of microorganisms for nitrogen removal. Currently, when using constructed wetlands to treat low carbon-nitrogen ratio wastewater, low temperatures in winter will affect the nitrogen removal efficiency, thereby reducing the wastewater treatment efficiency. Summary of the Invention

[0003] Based on this, in view of the problem that low winter temperatures restrict the nitrogen removal efficiency of constructed wetlands, it is necessary to provide a wastewater treatment system and method.

[0004] According to the first aspect of the present application, a wastewater treatment system is provided, including:

[0005] A carbon source pool;

[0006] A constructed wetland, connected to the carbon source pool;

[0007] A composite ditch for accommodating wastewater. The composite ditch includes an upper ditch, a lower ditch, a first connecting pipe, and a second connecting pipe. The first connecting pipe is connected between the upper ditch and the upper part of the constructed wetland, and the second connecting pipe is connected between the lower ditch and the lower part of the constructed wetland. The composite ditch further includes a first inlet valve, a first drain valve, a second inlet valve, and a second drain valve. The first inlet valve is used to conduct or cut off the water inlet of the upper ditch, the first drain valve is used to conduct or cut off the water outlet of the upper ditch, the second inlet valve is used to conduct or cut off the water inlet of the lower ditch, and the second drain valve is used to conduct or cut off the water outlet of the lower ditch;

[0008] Wherein, the composite ditch has a first mode and a second mode;

[0009] In the first mode, the first inlet valve and the second drain valve are both closed, and the first drain valve and the second inlet valve are both open;

[0010] In the second mode, the first inlet valve and the second drain valve are both open, and the first drain valve and the second inlet valve are both closed;

[0011] The temperature of the wastewater in the first mode is lower than the temperature of the wastewater in the second mode.

[0012] In one embodiment, the composite ditch further includes a first communication valve for opening or closing the first communication pipe; the composite ditch further includes a second communication valve for opening or closing the second communication pipe.

[0013] In the first mode, both the first communication valve and the second communication valve are open.

[0014] In the second mode, both the first communication valve and the second communication valve are open.

[0015] In one embodiment, the composite ditch further includes an isolation layer located between the upper ditch and the lower ditch. The isolation layer is provided with through holes, and the upper ditch communicates with the lower ditch through the through holes.

[0016] The composite ditch further has a third mode; in the third mode, both the first communication valve and the second communication valve are closed, and the first water inlet valve, the first drain valve, the second water inlet valve, and the second drain valve are all open.

[0017] In one embodiment, the composite ditch further includes a sealing layer.

[0018] In the first mode and the second mode, the sealing layer seals the through holes.

[0019] In one embodiment, the carbon source pool includes a pool body, a plant floating bed, and eutrophic water. The plant floating bed and the eutrophic water are arranged in the pool body. The plant floating bed is used for planting aquatic plants; the eutrophic water is used for cultivating the aquatic plants.

[0020] In one embodiment, the carbon source pool further includes a reflective component disposed on the bottom wall and the side wall of the pool body.

[0021] In one embodiment, the carbon source pool further includes an aeration pipe for introducing inorganic carbon source gas into the pool body from the outside.

[0022] In one embodiment, the carbon source pool further includes a protective cover for enclosing the space above the pool body.

[0023] In one embodiment, the constructed wetland includes a soil layer, a first filler layer, and a second filler layer arranged from top to bottom. The soil layer is used for planting emergent plants, the first filler layer is used for adsorbing nitrogen and phosphorus substances in the wastewater, and the second filler layer serves as a carrier for microorganisms.

[0024] In one embodiment, the constructed wetland further includes a third connecting pipe, at least a part of the third connecting pipe is located in the second filler layer, and the third connecting pipe is connected between the second filler layer and the carbon source pool.

[0025] According to a second aspect of the present application, there is provided a wastewater treatment method, which is applied to the wastewater treatment system as described in any of the foregoing embodiments. The wastewater treatment method includes:

[0026] Monitoring the temperature of the wastewater;

[0027] If the temperature of the wastewater meets a first preset condition, then close the first inlet valve and the second drain valve, and open the first drain valve and the second inlet valve;

[0028] If the temperature of the wastewater meets a second preset condition, then open the first inlet valve and the second drain valve, and close the first drain valve and the second inlet valve.

[0029] In one embodiment, the composite ditch further includes a first connecting valve for conducting or closing the first connecting pipe; the composite ditch further includes a second connecting valve for conducting or closing the second connecting pipe;

[0030] The composite ditch further includes an isolation layer located between the upper ditch and the lower ditch. The isolation layer is provided with through holes, and the upper ditch is connected to the lower ditch through the through holes;

[0031] The wastewater treatment method further includes:

[0032] If the temperature of the wastewater meets a third preset condition, then close the first connecting valve and the second connecting valve, and open the first inlet valve, the first drain valve, the second inlet valve and the second drain valve to make the temperature of the wastewater meet the second preset condition.

[0033] In one embodiment, the first preset condition is: t < the first preset temperature;

[0034] The second preset condition is: the first preset temperature ≤ t ≤ the second preset temperature;

[0035] The third preset condition is: t > the second preset temperature;

[0036] Wherein, t represents the temperature of the wastewater, the first preset temperature is between 8°C and 12°C, and the second preset temperature is between 28°C and 32°C.

[0037] In one embodiment, the wastewater treatment method further includes:

[0038] If the temperature of the wastewater meets the first preset condition, the water storage capacity of the carbon source pool is increased according to the preset water storage depth.

[0039] In one embodiment, the wastewater treatment method further includes:

[0040] Regularly harvest the aquatic plants in the carbon source pool.

[0041] In the above wastewater treatment system and its method, the first connecting pipe connects the upper ditch and the upper part of the constructed wetland, and the second connecting pipe connects the lower ditch and the lower part of the constructed wetland. According to the characteristics of the relatively constant temperature underground or underwater, in winter when the temperature is relatively low, the temperature of the lower part of the constructed wetland is higher than that of the upper part. In most cases, when the temperature of the wastewater is at an appropriate temperature condition, the composite ditch can turn on the second mode, both the first inlet valve and the second drain valve are opened, and both the first drain valve and the second inlet valve are closed, so that the wastewater enters the constructed wetland through the upper ditch, and after the nitrogen removal treatment by the constructed wetland, it is discharged through the lower ditch. The wastewater achieves the purpose of nitrogen removal through nitrification and denitrification reactions in sequence. When facing the low temperature situation in winter, the temperature of the wastewater is at a low temperature condition, and the composite ditch can turn on the first mode, both the first inlet valve and the second drain valve are closed, and both the first drain valve and the second inlet valve are opened, so that the wastewater enters the constructed wetland through the lower ditch, and after the nitrogen removal treatment by the constructed wetland, it is discharged through the upper ditch. On the one hand, it can effectively utilize the geothermal energy to conduct heat and raise the temperature of the influent water. On the other hand, it can reduce the heat loss caused by air convection in a relatively closed environment. The two together reduce the impact of low temperature on the nitrogen removal efficiency of the constructed wetland, indirectly improve the nitrogen removal efficiency of the constructed wetland under low temperature conditions, and further improve the wastewater treatment efficiency. Description of the Drawings

[0042] Figure 1 It is a schematic structural diagram of a wastewater treatment system in an embodiment of the present application.

[0043] Figure 2 It is Figure 1 a side view of the composite ditch in

[0044] Figure 3 It is a schematic structural diagram of the carbon source pool of a wastewater treatment system in another embodiment of the present application.

[0045] Figure 4 It is a schematic flow chart of a wastewater treatment method in an embodiment of the present application.

[0046] Figure 5 It is a schematic flow chart of a wastewater treatment method in another embodiment of the present application.

[0047] Description of the Reference Numerals:

[0048] 1. Carbon source pool; 11. Water tank body; 12. Plant floating bed; 13. Eutrophic water body; 14. Reflective component; 15. Aeration pipe; 16. Protective cover; K. Aquatic plants;

[0049] 2. Constructed wetland; 21. Soil layer; 22. First filler layer; 23. Second filler layer; 24. Third connecting pipe; Q. Emergent plants;

[0050] 3. Composite ditch; 31. Upper ditch; 32. Lower ditch; 33. First connecting pipe; 34. Second connecting pipe; 35. Isolation layer; 351. Through-hole area; a. First inlet valve; b. First drain valve; c. Second inlet valve; d. Second drain valve. Detailed implementation manners

[0051] To make the above objects, features, and advantages of the present application more apparent and understandable, the following describes the detailed implementation manners of the present application with reference to the accompanying drawings. Many specific details are set forth in the following description to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0052] In the description of the present application, it should be understood that if these terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. appear, the orientation or positional relationship indicated by these terms is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present application.

[0053] In addition, if these terms "first" and "second" appear, these terms are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present application, if the term "multiple" appears, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0054] In this application, unless otherwise clearly specified and defined, if terms such as "installed", "connected", "joined", "fixed", etc. appear, these terms shall be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0055] In this application, unless otherwise clearly specified and defined, if there is a description such as a first feature being "on" or "under" a second feature, its meaning can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature can be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature is at a higher horizontal level than the second feature. The first feature being "under", "beneath" and "underneath" the second feature can be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature is at a lower horizontal level than the second feature.

[0056] It should be noted that if an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or there can also be an intermediate element. If an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. If so, the terms "vertical", "horizontal", "up", "down", "left", "right" and similar expressions used in this application are only for the purpose of illustration and do not represent the only implementation.

[0057] Constructed wetlands are an economical and effective water treatment facility, with the advantages of low cost, easy operation and maintenance, and are widely used. Constructed wetlands can be used to treat low-carbon and low-nitrogen ratio wastewater such as the tail water of sewage treatment plants, low-pollution river water, urban surface runoff and farmland runoff. There are many ways for constructed wetlands to remove nitrogen from wastewater. Among them, nitrification-denitrification is the most important way, and the removal rate of total nitrogen can reach 60% - 70%. However, in actual applications, the denitrification reaction of microorganisms is greatly affected by temperature. Especially in winter at low temperatures, the nitrogen removal efficiency will be reduced, and thus the wastewater treatment efficiency is also relatively low.

[0058] Based on this, this application provides a wastewater treatment system and its method to improve the nitrogen removal efficiency of constructed wetlands under low-temperature conditions in winter.

[0059] Refer to Figure 1 , Figure 1The structural schematic diagram of the wastewater treatment system in an embodiment of the present application is shown. The wastewater treatment system provided in an embodiment of the present application at least includes a carbon source pool 1, a constructed wetland 2, and a composite ditch 3. The constructed wetland 2 is communicated with the carbon source pool 1. The composite ditch 3 is used to accommodate wastewater. The composite ditch 3 includes an upper ditch 31, a lower ditch 32, a first communication pipe 33, and a second communication pipe 34. The first communication pipe 33 is connected between the upper ditch 31 and the upper part of the constructed wetland 2, and the second communication pipe 34 is connected between the lower ditch 32 and the lower part of the constructed wetland 2. The composite ditch 3 further includes a first inlet valve a, a first drain valve b, a second inlet valve c, and a second drain valve d. The first inlet valve a is used to conduct or cut off the water inlet of the upper ditch 31, the first drain valve b is used to conduct or cut off the water outlet of the upper ditch 31, the second inlet valve c is used to conduct or cut off the water inlet of the lower ditch 32, and the second drain valve d is used to conduct or cut off the water outlet of the lower ditch 32.

[0060] Among them, the composite ditch 3 has a first mode and a second mode. In the first mode, both the first inlet valve a and the second drain valve d are closed, and both the first drain valve b and the second inlet valve c are open. In the second mode, the first inlet valve a and the second drain valve d are both open, and the first drain valve b and the second inlet valve c are both closed. The temperature of the wastewater in the first mode is lower than the temperature of the wastewater in the second mode.

[0061] It should be noted that the three areas of the carbon source pool 1, the constructed wetland 2, and the composite ditch 3 can be separated by a brick partition wall or a concrete partition wall, or alternatively, these three areas are not continuously constructed together. This embodiment does not make any restrictions as long as the cooperation of these three areas can complete the denitrification treatment of wastewater.

[0062] The carbon source pool 1 is a carrier for providing the organic carbon required for the denitrification reaction of the constructed wetland 2. Exemplarily, the carbon source pool 1 can adopt a plant carbon source. The constructed wetland 2 is a place for denitrifying wastewater by means of the nitrification reaction of plants and the denitrification reaction of microorganisms. Generally, the upper part of the constructed wetland 2 includes some plants for carrying out nitrification reactions, and the lower part includes some microorganisms for carrying out denitrification reactions. According to the characteristics of warm in winter and cool in summer underground or underwater, when the winter temperature is relatively low, the temperature of the lower part of the constructed wetland 2 will be higher than that of the upper part. When the summer temperature is relatively high, the temperature of the lower part of the constructed wetland 2 will be lower than that of the upper part. When the temperature is suitable, the temperature difference between the lower part and the upper part of the constructed wetland 2 is not large.

[0063] The composite ditch 3 is used to hold wastewater, and the wastewater can flow into the constructed wetland 2 through the composite ditch 3 and undergo denitrification treatment in the constructed wetland 2. The wastewater after denitrification treatment can also be discharged through the composite ditch 3. The wastewater can be low-carbon-nitrogen ratio tail water, sewage, urban surface runoff, or farmland runoff drainage, etc. The composite ditch 3 includes an upper ditch 31 and a lower ditch 32 located in the same vertical direction. The upper ditch 31 is connected to the upper part of the constructed wetland 2 through a first connecting pipe 33, and the lower ditch 32 is connected to the lower part of the constructed wetland 2 through a second connecting pipe 34. The first inlet valve a is used to conduct or cut off the water inlet of the upper ditch 31, the first drain valve b is used to conduct or cut off the water outlet of the upper ditch 31, the second inlet valve c is used to conduct or cut off the water inlet of the lower ditch 32, and the second drain valve d is used to conduct or cut off the water outlet of the lower ditch 32. By setting two layers of ditches, it is convenient to switch the wastewater flow path. The first mode refers to the wastewater flow path under low-temperature conditions. The second mode refers to the wastewater flow path under appropriate-temperature conditions.

[0064] The temperature of the wastewater mainly refers to the temperature of the wastewater to be treated. Exemplarily, in order to facilitate the monitoring of the temperature of the wastewater, a waterproof temperature sensor can be installed in the upper ditch 31, as long as it can monitor the wastewater temperature. Or, waterproof temperature sensors can be installed in both the upper ditch 31 and the lower ditch 32. Or, the temperature of the wastewater to be treated can be monitored in the total pool for holding the wastewater to be treated. Any of the above three methods is acceptable, and specific selection can be made according to specific usage requirements.

[0065] Specifically, in the first mode, that is, under the low-temperature state, both the first inlet valve a and the second drain valve d are closed, and both the first drain valve b and the second inlet valve c are open. The wastewater enters the lower ditch 32 through the second inlet valve c, then enters the lower part of the constructed wetland 2 through the second connecting pipe 34. By appropriately extending the hydraulic retention time, the wastewater is diffused to the upper part of the constructed wetland 2, and the denitrification purpose is achieved through the nitrification-denitrification reaction. Then, the wastewater after denitrification treatment is discharged to the upper ditch 31 through the first connecting pipe 33 and then discharged through the first drain valve b. In this way, a bottom-in and top-out water flow path is formed, enabling the wastewater under the low-temperature state to be thermally conducted and heated by the geothermal energy in the lower part of the constructed wetland 2 for the incoming wastewater, which is beneficial for microorganisms to carry out the denitrification reaction and improve the denitrification efficiency.

[0066] Further, in the second mode, i.e., the suitable temperature state, the first water inlet valve a and the second drain valve d are both opened, and the first drain valve b and the second water inlet valve c are both closed. The wastewater enters the upper channel 31 through the first water inlet valve a, and then enters the upper part of the constructed wetland 2 through the first connecting pipe 33, diffusing the wastewater to the upper part of the constructed wetland 2, and achieving the purpose of nitrogen removal through nitrification-denitrification reaction. Then, the wastewater after nitrogen removal treatment is discharged to the lower channel 32 through the second connecting pipe 34 and discharged through the second drain valve d. In this way, an upward-inlet and downward-outlet water flow path is formed, enabling the wastewater to first undergo nitrification reaction through the plants in the upper part of the constructed wetland 2, and then be diffused to the lower part of the constructed wetland 2 by the water flow, and the denitrification reaction is carried out by microorganisms, thereby achieving the purpose of nitrogen removal.

[0067] It should be noted that in most cases, the temperature of the wastewater is in the suitable temperature state. At this time, the upward-inlet and downward-outlet water flow path is more in line with the sequence of nitrification reaction and denitrification reaction, with a shorter hydraulic retention time and higher nitrogen removal efficiency compared to the low-temperature state. However, in the low-temperature state, by adopting the downward-inlet and upward-outlet water flow path, the hydraulic retention time can be appropriately extended to allow sufficient time for the nitrification reaction and denitrification reaction, making the reaction more complete and improving the nitrogen removal efficiency.

[0068] It can be understood that compared with a single downward-inlet and upward-outlet water flow path, the present embodiment adopts two water flow paths of downward-inlet and upward-outlet and upward-inlet and downward-outlet alternately, which is more conducive to improving the nitrogen removal efficiency of the system.

[0069] In this embodiment, the first connecting pipe 33 connects the upper-layer ditch 31 and the upper part of the constructed wetland 2, and the second connecting pipe 34 connects the lower-layer ditch 32 and the lower part of the constructed wetland 2. According to the characteristics of warm in winter and cool in summer underground or underwater, when the temperature is relatively low in winter, the temperature of the lower part of the constructed wetland 2 is higher than that of the upper part. In most cases, when the temperature of the wastewater is within the appropriate temperature range, the composite ditch can operate in the second mode, where the first inlet valve a and the second drain valve d are both opened, and the first drain valve b and the second inlet valve c are both closed. As a result, the wastewater enters the constructed wetland 2 through the upper-layer ditch 31. After nitrogen removal treatment in the constructed wetland 2, it is then discharged through the lower-layer ditch 32. The wastewater achieves nitrogen removal through nitrification and denitrification reactions successively. When facing the low-temperature situation in winter, with the temperature of the wastewater being in the low-temperature range, the composite ditch can operate in the first mode, where the first inlet valve a and the second drain valve d are both closed, and the first drain valve b and the second inlet valve c are both opened. Thus, the wastewater enters the constructed wetland 2 through the lower-layer ditch 32. After nitrogen removal treatment in the constructed wetland 2, it is then discharged through the upper-layer ditch 31. On the one hand, it can effectively utilize geothermal energy to conduct heat and raise the temperature of the influent. On the other hand, in a relatively enclosed environment, it can reduce heat loss caused by air convection. The two aspects together reduce the impact of low temperature on the nitrogen removal efficiency of the constructed wetland 2, indirectly improving the nitrogen removal efficiency of the constructed wetland 2 under low-temperature conditions and further enhancing the wastewater treatment efficiency.

[0070] In some embodiments, the composite ditch 3 further includes a first connecting valve (not shown in the figure), and the first connecting valve is used to conduct or cut off the first connecting pipe 33. The composite ditch 3 further includes a second connecting valve (not shown in the figure), and the second connecting valve is used to conduct or cut off the second connecting pipe 34. In the first mode, both the first connecting valve and the second connecting valve are opened. In the second mode, both the first connecting valve and the second connecting valve are opened.

[0071] Specifically, the first connecting valve and the second connecting valve can be opened or closed by an operator, or the operation of the first connecting valve and the second connecting valve can be controlled by an external control module. This control module can be electrically connected to a temperature sensor, and based on the wastewater temperature result monitored by the temperature sensor, it conducts or closes the first connecting valve and the second connecting valve. In this way, in the first mode and the second mode of the composite ditch 3, the upper-layer ditch 31 and the upper part of the constructed wetland 2 remain connected, and the lower-layer ditch 32 and the lower part of the constructed wetland 2 remain connected.

[0072] Please continue to refer to Figure 1 and in combination with Figure 2, in some embodiments, the composite ditch 3 further includes a separation layer 35. The separation layer 35 is located between the upper ditch 31 and the lower ditch 32. Through holes (not shown in the figure) are provided on the separation layer 35, and the upper ditch 31 is connected to the lower ditch 32 through the through holes. The composite ditch 3 also has a third mode. In the third mode, both the first connection valve and the second connection valve are closed, and the first water inlet valve a, the first drain valve b, the second water inlet valve c, and the second drain valve d are all opened. The third mode refers to the wastewater flow path under high temperature conditions.

[0073] It should be noted that the upper ditch 31 and the lower ditch 32 are separated by the separation layer 35. There is a through hole area 351 on the separation layer. Through holes are opened on the through hole area 351. Exemplarily, the through hole area 351 can be provided with 1, 2 or 3. A number of through holes are penetrated through each through hole area to connect the upper ditch 31 and the lower ditch 32. In this embodiment, the number of through hole areas and the number of through holes in each through hole area are not overly limited and can be specifically determined according to specific scenario requirements.

[0074] Specifically, in the third mode, that is, the high temperature mode, both the first connection valve and the second connection valve are closed, and the first water inlet valve a, the first drain valve b, the second water inlet valve c, and the second drain valve d are all opened. In this way, the wastewater can circulate between the upper ditch 31 and the lower ditch 32, reducing the temperature of the wastewater to be treated and increasing the dissolved oxygen content in the water body, which is more conducive to the subsequent denitrification reaction of microorganisms and improving the nitrogen removal efficiency.

[0075] Furthermore, the composite ditch 3 further includes a plugging layer (not shown in the figure). In the first mode and the second mode, the plugging layer plugs the through holes.

[0076] It should be noted that the plugging layer can adopt temporary plugging materials. Exemplarily, bricks, plates or large stones can be used to temporarily plug the through holes.

[0077] Specifically, in the third mode, after cooling treatment, the temperature of the wastewater approaches the suitable temperature. Then, both the first connection valve and the second connection valve are opened, and the through hole area 351 is plugged with temporary plugging materials. Then, the composite ditch 3 adopts the wastewater flow path in the suitable temperature state, that is, the second mode, to maintain the wastewater flow path of entering from the upper part and discharging from the lower part, so that the constructed wetland 2 performs nitrogen removal treatment. In addition, if in the low temperature state, the through hole area 351 is still plugged with temporary plugging materials, which is convenient for the wastewater to flow in the path of entering from the lower part and discharging from the upper part.

[0078] Please continue to refer to Figure 1, in some embodiments, the carbon source pool 1 may include a water pool body 11, a plant floating bed 12, and eutrophic water body 13. The plant floating bed 12 and the eutrophic water body 13 are arranged inside the water pool body 11. The plant floating bed 12 is used for planting aquatic plants K. The eutrophic water body 13 is used for cultivating aquatic plants K.

[0079] Specifically, the plant floating bed 12 is a carrier for planting aquatic plants K. The eutrophic water body 13 is a water body for cultivating aquatic plants K. Exemplarily, eutrophic surface water such as lakes and rivers can be used. Aquatic plants K are plants with a fast growth cycle and good economy, resulting in a high overall harvesting frequency and a large carbon fixation amount. The planting position of aquatic plants K can be close to the water surface or underwater (in combination Figure 1 and Figure 3 ).

[0080] Exemplarily, aquatic plants K can be selected as ornamental plants, such as Chlorophytum comosum, or economic crops, such as Ipomoea aquatica and / or Oenanthe javanica. In addition, it should be noted that the organic matter secreted by the roots of aquatic plants K accounts for 15% - 25% of the total photosynthetically fixed carbon. These are all high-quality carbon sources, and the organic acids in the root exudates can promote the growth of ammonifying bacteria and denitrifying bacteria in microorganisms and inhibit the growth of nitrite bacteria and nitrifying bacteria, thereby further improving the nitrogen removal efficiency of the constructed wetland 2.

[0081] In this way, the eutrophic water body 13 is used to accelerate the photosynthesis of aquatic plants K, which not only increases the carbon fixation amount of the system but also increases the organic carbon secreted by the roots of aquatic plants K. The organic carbon serves as a supplementary carbon source for the denitrification reaction in the constructed wetland 2. The eutrophic water body 13 rich in organic carbon can be directly transported to the denitrification reaction zone in the lower part of the constructed wetland 2, improving the carbon source utilization rate and nitrogen removal efficiency. And throughout the process, it can overcome the problem of carbon source ratio imbalance caused by insufficient carbon source in the wastewater and also achieve the dual purposes of nitrogen removal and carbon fixation.

[0082] Please refer to Figure 3 , the carbon source pool 1 further includes a light-reflecting component 14, and the light-reflecting component 14 is arranged on the bottom wall and side walls of the water pool body 11.

[0083] Specifically, the light-reflecting component 14 is a functional configuration object for reflecting sunlight. Exemplarily, a light-reflecting film or a mirror can be pasted on the bottom wall and side walls of the water pool body 11. In this way, when sunlight enters the water pool body 11, it can not only enable the front side of the leaves of aquatic plants K to carry out photosynthesis, but also enable the back side of the leaves of aquatic plants K to carry out photosynthesis after being reflected by the light-reflecting film or mirror, thereby enhancing the photosynthesis of aquatic plants K, increasing the carbon fixation amount, and also promoting the secretion of more organic carbon by the roots of aquatic plants K.

[0084] Please continue to refer toFigure 3 The carbon source pool 1 further includes an aeration pipe 15, which is used to introduce inorganic carbon source gas from the outside into the water tank body 11.

[0085] Exemplarily, the inorganic carbon source gas can be carbon dioxide. Carbon dioxide is introduced into the bottom of the water tank body 11 through the aeration pipe 15 by an external aeration device, increasing the inorganic carbon content to improve the photosynthesis of the aquatic plant K and promoting the secretion of organic carbon by the roots of the aquatic plant K to supplement the carbon source for the denitrification reaction of the constructed wetland 2.

[0086] Furthermore, wood carbon source can be added to the water tank body 11 to release the fixed carbon in the wood and supplement the carbon source for the denitrification reaction of the constructed wetland 2.

[0087] Furthermore, the carbon source pool 1 further includes a protective cover 16, which is used to enclose the upper space of the water tank body 11. Specifically, the protective cover 16 can be made of a light-transmitting material, for example, a plastic film of polyethylene material or glass. In this way, it is convenient for sunlight to enter the carbon source pool 1, and in a closed environment, the carbon dioxide concentration in the water tank body 11 is higher, which is more conducive to the photosynthesis of the aquatic plant K.

[0088] Please continue to refer to Figure 1 The constructed wetland 2 includes a soil layer 21, a first filler layer 22, and a second filler layer 23 arranged from top to bottom. The soil layer 21 is used to plant emergent plants Q, the first filler layer 22 is used to adsorb nitrogen and phosphorus substances in the wastewater, and the second filler layer 23 serves as a carrier for microorganisms.

[0089] Specifically, the emergent plant Q is a plant used for the nitrification reaction of wastewater. Exemplarily, the emergent plant Q can be one or a combination of reed, cattail, nutgrass galingale rhizome, calamus, Chinese alpine rush, and phalaris arundinacea, etc. The soil layer 21 is an environmental place for the growth of the emergent plant Q. In addition, the emergent plant Q can also perform photosynthesis, enabling the plant roots to secrete organic carbon for microorganisms to carry out denitrification reaction. The first filler layer 22 is mainly used to adsorb nitrogen and phosphorus substances in the wastewater and can also serve as a carrier for microorganisms. The second filler layer 23 mainly serves as a carrier for microorganisms. The particle sizes of the fillers in the first filler layer 22 and the second filler layer 23 are different, and their filler materials can be the same or different. Exemplarily, the first filler layer 22 can be a combination of one or more of ceramsite, zeolite, steel slag, pebbles, waste bricks, tailings, and gravel, and the second filler layer 23 can be a combination of one or more of ceramsite, zeolite, steel slag, pebbles, waste bricks, tailings, and gravel.

[0090] Furthermore, the constructed wetland 2 further includes a third connecting pipe 24, at least a part of the third connecting pipe 24 is located in the second filler layer 23, and the third connecting pipe 24 is connected between the second filler layer 23 and the carbon source pool 1.

[0091] Specifically, the third connecting pipe 24 can be a Z-shaped pipe or a straight pipe. Exemplarily, in some embodiments, a Z-shaped pipe (combined Figure 1 ) can be used to connect between the carbon source pool 1 and the constructed wetland 2. The eutrophic water rich in organic carbon enters the second packing layer 23 through the high water level inlet of the Z-shaped pipe, and the vertical part of the Z-shaped pipe can be buried in the vertical wall between the carbon source pool 1 and the constructed wetland 2. The Z-shaped pipe is provided with a plurality of perforations on the pipe located in the second packing layer 23, so as to facilitate the discharge of the eutrophic water body 13 rich in organic carbon to the second packing layer 23 and supplement the carbon source for the denitrification reaction of microorganisms. Further, in order to prevent the perforations from being blocked, geotextile or gauze can be coated outside the Z-shaped pipe.

[0092] In other embodiments, a straight pipe can be used to connect between the carbon source pool 1 and the constructed wetland 2, as long as there is a water level difference between the inlet and outlet ends of the straight pipe. In this way, it is convenient for the eutrophic water rich in organic carbon to flow into the second packing layer 23. The straight pipe is also provided with a plurality of perforations on the pipe located in the second packing layer 23, so as to facilitate the discharge of the eutrophic water body 13 rich in organic carbon to the second packing layer 23 and supplement the carbon source for the denitrification reaction of microorganisms. Further, in order to prevent the perforations from being blocked, geotextile or gauze can be coated outside the straight pipe.

[0093] Please refer to Figure 4 , based on the same inventive concept, another embodiment of the present application provides a wastewater treatment method, which is applied to the wastewater treatment system of any of the foregoing embodiments. The wastewater treatment method includes the following steps:

[0094] S1. Monitor the temperature of the wastewater;

[0095] S2. If the temperature of the wastewater meets the first preset condition, close the first inlet valve a and the second drain valve d, and open the first drain valve b and the second inlet valve c;

[0096] S3. If the temperature of the wastewater meets the second preset condition, open the first inlet valve a and the second drain valve d, and close the first drain valve b and the second inlet valve c.

[0097] It should be noted that the temperature of the wastewater under the first preset condition is less than the temperature of the wastewater under the second preset condition.

[0098] Specifically, in most cases, when the temperature of the wastewater meets the second preset condition, that is, the suitable temperature condition, the first inlet valve a and the second drain valve d are both opened, and the first drain valve b and the second inlet valve c are both closed. Thus, the wastewater enters the constructed wetland 2 through the upper channel 31, and after being subjected to denitrification treatment in the constructed wetland 2, it is discharged through the lower channel 32. The wastewater achieves the denitrification purpose through nitrification reaction and denitrification reaction successively. When facing the low temperature in winter, when the temperature of the wastewater meets the first preset condition, that is, the low temperature condition, the first inlet valve a and the second drain valve d are both closed, and the first drain valve b and the second inlet valve c are both opened. Thus, the wastewater enters the constructed wetland 2 through the lower channel 32, and after being subjected to denitrification treatment in the constructed wetland 2, it is discharged through the upper channel 31. On the one hand, the geothermal energy can be effectively utilized to conduct heat and raise the temperature of the influent. On the other hand, the heat loss caused by air convection can be reduced in a relatively closed environment. The two jointly reduce the influence of low temperature on the denitrification efficiency of the constructed wetland 2, indirectly improve the denitrification efficiency of the constructed wetland 2 under low temperature conditions, and further improve the wastewater treatment efficiency.

[0099] In some embodiments, the composite channel 3 further includes a first connection valve for conducting or closing the first connecting pipe 33. The composite channel 32 further includes a second connection valve for conducting or closing the second connecting pipe 34. The composite channel 3 further includes an isolation layer 35 located between the upper channel 31 and the lower channel 32. The isolation layer 35 is provided with through holes, and the upper channel 31 is connected to the lower channel 32 by means of the through holes. Please refer to Figure 5 , the wastewater treatment method further includes:

[0100] S4. If the temperature of the wastewater meets the third preset condition, the first connection valve and the second connection valve are closed, and the first inlet valve a, the first drain valve b, the second inlet valve c, and the second drain valve d are opened to make the temperature of the wastewater meet the second preset condition.

[0101] It should be noted that the temperature of the wastewater under the third preset condition is higher than the temperature of the wastewater under the second preset condition.

[0102] Specifically, in the third mode, that is, the high temperature mode, the first connection valve and the second connection valve are both closed, and the first inlet valve a, the first drain valve b, the second inlet valve c, and the second drain valve d are all opened. In this way, the wastewater can circulate between the upper channel 31 and the lower channel 32, reducing the temperature of the wastewater to be treated. After increasing the dissolved oxygen content in the water body, it is more conducive to the subsequent denitrification reaction of microorganisms and improves the denitrification efficiency.

[0103] In some embodiments, the first preset condition is: t < the first preset temperature. The second preset condition is: the first preset temperature ≤ t ≤ the second preset temperature. The third preset condition is: t > the second preset temperature. Wherein, t represents the temperature of the wastewater, the first preset temperature is between 8°C and 12°C, and the second preset temperature is between 28°C and 32°C.

[0104] It should be noted that the first preset temperature may refer to a low-temperature reference value, and the second preset temperature may refer to a high-temperature reference value. Exemplarily, the first preset temperature can be set to 8°C, and the second preset temperature can be set to 28°C. Or, the first preset temperature can be set to 10°C, and the second preset temperature can be set to 30°C. Or, the first preset temperature can be set to 12°C, and the second preset temperature can be set to 32°C. In this embodiment, the specific settings of the first preset temperature and the second preset temperature are not overly limited and can be specifically selected according to specific scenario requirements.

[0105] In some embodiments, the wastewater treatment method further includes: if the temperature of the wastewater meets the first preset condition, the water storage capacity of the carbon source pool 1 is increased according to the preset water storage depth. It should be noted that the specific value of the preset water storage depth can be set through experimental tests or manual experience, and this embodiment does not limit it further here.

[0106] Specifically, during the winter operation, the water storage depth of the carbon source pool 1 can be appropriately increased to make the water level at the inlet of the third connecting pipe 24 lower than the water level of the water surface of the carbon source pool 1. According to the characteristics of warmer in winter and cooler in summer underground or underwater, the water temperature at the inlet of the third connecting pipe 24 is higher than the water temperature of the water surface of the carbon source pool 1. In this way, the temperature of the eutrophic water introduced into the constructed wetland 2 through the third connecting pipe 24 is higher, which helps to improve the denitrification efficiency of the constructed wetland 2 and reduce the impact of low winter temperature on the wastewater purification treatment.

[0107] In some embodiments, the wastewater treatment method further includes: regularly harvesting the aquatic plants K in the carbon source pool 1. In this way, it is possible to avoid new pollution caused by the rotting of plants in the carbon source pool 1.

[0108] In summary, in the wastewater treatment system and method of this embodiment, the first connecting pipe 33 connects the upper-layer ditch 31 and the upper part of the constructed wetland 2, and the second connecting pipe 34 connects the lower-layer ditch 32 and the lower part of the constructed wetland 2. According to the characteristics of warm in winter and cool in summer underground or underwater, when the temperature is relatively low in winter, the temperature of the lower part of the constructed wetland 2 is higher than that of the upper part. In most cases, when the temperature of the wastewater is at an appropriate temperature condition, the first inlet valve a and the second drain valve d are both opened, and the first drain valve b and the second inlet valve c are both closed, so that the wastewater enters the constructed wetland 2 through the upper-layer ditch 31. After denitrification treatment in the constructed wetland 2, it is then discharged through the lower-layer ditch 32. The wastewater achieves the purpose of denitrification through nitrification reaction and denitrification reaction successively. When facing the low-temperature situation in winter, the temperature of the wastewater is at a low-temperature condition, the first inlet valve a and the second drain valve d are both closed, and the first drain valve b and the second inlet valve c are both opened, so that the wastewater enters the constructed wetland 2 through the lower-layer ditch 32. After denitrification treatment in the constructed wetland 2, it is then discharged through the upper-layer ditch 31. On the one hand, the geothermal energy can be effectively utilized to conduct heat and raise the temperature of the influent. On the other hand, the heat loss caused by air convection can be reduced in a relatively closed environment. The two jointly reduce the influence of low temperature on the denitrification efficiency of the constructed wetland 2, indirectly improve the denitrification efficiency of the constructed wetland 2 under low-temperature conditions, and further improve the wastewater treatment efficiency. In addition, the carbon source pool 1 uses the eutrophic water body 13 to cultivate the aquatic plant K to accelerate the photosynthesis of the aquatic plant K, which not only increases the carbon fixation amount of the system, but also increases the organic carbon secreted by the roots of the aquatic plant K. The organic carbon serves as a supplementary carbon source for the denitrification reaction in the constructed wetland 2, improving the carbon source utilization rate and denitrification efficiency. And throughout the process, it can overcome the problem of carbon source ratio imbalance caused by insufficient carbon source in the wastewater, and also achieve the dual purposes of denitrification and carbon fixation.

[0109] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0110] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A wastewater treatment system, characterized in that, Comprising: A carbon source pool; The carbon source pool includes a pool body, a plant floating bed, and eutrophic water. The plant floating bed and the eutrophic water are arranged in the pool body. The plant floating bed is used for planting aquatic plants; the eutrophic water is used for cultivating the aquatic plants; the carbon source pool further includes a reflective component, which is arranged on the bottom wall and side wall of the pool body; the carbon source pool further includes an aeration pipe, which is used to introduce inorganic carbon source gas into the pool body from the outside; the carbon source pool further includes a protective cover, which is used to enclose the upper space of the pool body; An artificial wetland, which is connected to the carbon source pool; A composite ditch, which is used to accommodate wastewater. The composite ditch includes an upper ditch, a lower ditch, a first connecting pipe, and a second connecting pipe. The first connecting pipe is connected between the upper ditch and the upper part of the artificial wetland, and the second connecting pipe is connected between the lower ditch and the lower part of the artificial wetland. The composite ditch further includes a first inlet valve, a first drain valve, a second inlet valve, and a second drain valve. The first inlet valve is used to conduct or cut off the water inlet of the upper ditch, the first drain valve is used to conduct or cut off the water outlet of the upper ditch, the second inlet valve is used to conduct or cut off the water inlet of the lower ditch, and the second drain valve is used to conduct or cut off the water outlet of the lower ditch; Wherein, the composite ditch has a first mode and a second mode; In the first mode, the first inlet valve and the second drain valve are both closed, and the first drain valve and the second inlet valve are both open; In the second mode, the first inlet valve and the second drain valve are both open, and the first drain valve and the second inlet valve are both closed; The temperature of the wastewater in the first mode is less than the temperature of the wastewater in the second mode.

2. The wastewater treatment system according to claim 1, wherein The composite ditch further includes a first connecting valve, which is used to conduct or cut off the first connecting pipe; the composite ditch further includes a second connecting valve, which is used to conduct or cut off the second connecting pipe; In the first mode, the first connecting valve and the second connecting valve are both open; In the second mode, the first connecting valve and the second connecting valve are both open.

3. The wastewater treatment system according to claim 2, characterized in that, The composite ditch further includes an isolation layer, which is located between the upper ditch and the lower ditch. The isolation layer is provided with through holes, and the upper ditch is connected to the lower ditch through the through holes; The composite ditch further has a third mode; in the third mode, the first connecting valve and the second connecting valve are both closed, and the first inlet valve, the first drain valve, the second inlet valve, and the second drain valve are all open.

4. The wastewater treatment system according to claim 3, characterized in that, The composite ditch further includes a blocking layer; In the first mode and the second mode, the blocking layer blocks the through holes.

5. The wastewater treatment system according to any one of claims 1-4, characterized in that, The artificial wetland includes a soil layer, a first filler layer, and a second filler layer arranged from top to bottom. The soil layer is used for planting emergent plants, the first filler layer is used for adsorbing nitrogen and phosphorus substances in the wastewater, and the second filler layer serves as a carrier for microorganisms.

6. The wastewater treatment system according to claim 5, characterized in that, The constructed wetland further includes a third connecting pipe, at least a part of the third connecting pipe is located in the second filler layer, and the third connecting pipe is connected between the second filler layer and the carbon source pool.

7. A wastewater treatment method, applied to the wastewater treatment system according to any one of claims 1-6, characterized in that, The wastewater treatment method includes: monitoring the temperature of the wastewater; if the temperature of the wastewater meets the first preset condition, closing the first inlet valve and the second drain valve, and opening the first drain valve and the second inlet valve; if the temperature of the wastewater meets the second preset condition, opening the first inlet valve and the second drain valve, and closing the first drain valve and the second inlet valve.

8. The wastewater treatment method according to claim 7, characterized in that, The composite ditch further includes a first connecting valve for conducting or closing the first connecting pipe; the composite ditch further includes a second connecting valve for conducting or closing the second connecting pipe; The composite ditch further includes an isolation layer located between the upper ditch and the lower ditch, and through holes are provided on the isolation layer, and the upper ditch is communicated with the lower ditch by means of the through holes; The wastewater treatment method further includes: if the temperature of the wastewater meets the third preset condition, closing the first connecting valve and the second connecting valve, and opening the first inlet valve, the first drain valve, the second inlet valve and the second drain valve, so that the temperature of the wastewater meets the second preset condition.

9. The wastewater treatment method according to claim 8, wherein the first preset condition is: t < the first preset temperature; the second preset condition is: the first preset temperature ≤ t ≤ the second preset temperature; the third preset condition is: t > the second preset temperature; wherein, t represents the temperature of the wastewater, the first preset temperature is between 8°C and 12°C, and the second preset temperature is between 28°C and 32°C.

10. The wastewater treatment method according to any one of claims 7-9, characterized in that, The wastewater treatment method further includes: if the temperature of the wastewater meets the first preset condition, increasing the water storage capacity of the carbon source pool according to a preset water storage depth.

11. The wastewater treatment method according to any one of claims 7-9, characterized in that The wastewater treatment method further includes: regularly harvesting the aquatic plants in the carbon source pool.

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