An artificial wetland system for sewage treatment and operation method thereof

Abstract

An artificial wetland system for treating domestic sewage comprises a bed body in a pool body, a partition wall is arranged in the pool body, the partition wall divides the bed body into a bed body A and a bed body B from the water inlet to the water outlet direction, a water distribution branch pipe enters from the lower part of the bed body A, a C-shaped water collecting pipe along the left and right horizontal direction is fixedly arranged on the upper part of the partition wall, a plurality of horizontal front-to-back water distribution overflow pipes are fixedly connected to the C-shaped water collecting pipe along the width direction, a plurality of water outlet holes are opened on the water distribution overflow pipe, a plurality of trough bodies are fixedly arranged on the upper part of the bed body B along the left and right direction, water seepage holes are opened on the bottom surface and the peripheral wall of the trough body, there are gaps between the trough bodies, soil is inside the filter screen in the trough body, the height of the trough body is lower than the water distribution overflow pipe, the water distribution overflow pipe is located above the trough body, an inverted U-shaped siphon drain pipe is installed at the bottom of the bed body B, the top of the siphon drain pipe is lower than the C-shaped water collecting pipe, and the outlet of the siphon drain pipe is located in the drainage channel. The denitrification effect of the present invention is good.

Description

Technical Field

[0001] The invention relates to sewage treatment, in particular to an artificial wetland system for sewage treatment and an operation method thereof, belonging to the technical field of environmental protection. Background Art

[0002] For decentralized domestic sewage, such as rural township sewage, since the cost of incorporating it into the municipal sewage treatment system is too high, artificial wetlands have been proven to be very suitable for treating this type of sewage in the past. The use of artificial wetlands to treat sewage consumes low energy, is environmentally friendly, and has good environmental and social benefits. In addition to domestic sewage, artificial wetlands can also be used in many occasions, such as water treatment in lakes and tailwater treatment in sewage treatment plants. At present, artificial wetlands have many cases in these applications. There are also many public technical solutions for artificial wetlands in Chinese patent literature. It is well known in the industry that the problems in the operation of existing artificial wetland systems mainly include the following aspects: First, in the treatment of domestic sewage with a certain nitrogen content, the nitrification process needs to be carried out in an aerobic environment, and the denitrification needs to be carried out in an anoxic environment. Anoxic environments are easy to form in artificial wetlands. How can the wetland be effectively supplied with oxygen to meet the nitrification process in the denitrification treatment? Second, how to avoid blockage and extend the service life of the wetland system? For the first problem, the traditional method is to use intermittent aeration in the artificial wetland, and some also install pumps for circulation during aeration to achieve Backflow is used to achieve better water discharge effect. Although this method has certain effects, it consumes energy and has high processing costs. Based on this problem, the industry has also proposed waterfall design and tidal flow artificial wetland methods. The waterfall design requires a drop structure, which is not applicable in many occasions. Tidal flow is to alternately fill and drain the wetland during wetland operation to provide alternating anoxic and aerobic environments to improve the denitrification effect. The drainage can be done by water pumps or siphon drainage, but the reoxygenation capacity of this operation mode is still limited after research. In order to improve the reoxygenation capacity, Chinese patent application No. 2019110554552 (A submerged artificial wetland system with strong denitrification and non-powered reoxygenation and its application) discloses a technical solution for oxygenation using aeration components. Although this solution can improve the reoxygenation capacity of the bed to a certain extent, it will become anoxic again after rapid flooding after reoxygenation, and the sites where nitrification and denitrification occur overlap, and different bacterial communities cannot be taken into account. The current tidal flow wetland operation has a long period of emptying, and the water around the plants is significantly reduced during emptying, so the utilization of plants is obviously insufficient. For the second problem, many artificial wetlands still use aeration to prevent internal blockage in the wetland. Summary of the invention

[0003] The purpose of the present invention is to overcome the above-mentioned problems existing in current artificial wetlands and to provide an artificial wetland system for domestic sewage treatment and an operation method thereof.

[0004] In order to achieve the purpose of the present invention, the following technical scheme is adopted: an artificial wetland system for domestic sewage treatment, including a pool body and a bed body located in the pool body, the bed body including multiple layers of fillers, the multiple layers of fillers are arranged in order of increasing particle size from top to bottom, there is a soil layer above the bed body, plants are planted in the soil layer, the water inlet of the bed body is connected to a water distribution main pipe, a regulating valve is installed on the water distribution main pipe, a plurality of parallel water distribution branches are connected to the water distribution main pipe through a transverse pipe, a partition wall is arranged in the pool body, the partition wall divides the bed body into bed A and bed B from the water inlet to the water outlet direction, the water distribution branch pipe enters from the lower part of the bed A, and a C-type water collecting pipe is fixedly arranged along the left and right horizontal directions on the upper part of the partition wall, the C-type water collecting pipe opening faces the side of the bed A, and the C-type water collecting pipe is opened to the side of the bed A. A filter screen is fixedly installed on the water pipe opening to prevent filler from entering. A plurality of horizontal front-to-back water distribution overflow pipes are fixedly connected to the C-shaped water collecting pipe in the width direction. The water distribution overflow pipe is provided with a plurality of water outlet holes. A plurality of trough bodies are fixedly arranged on the upper part of the bed B in the left-right direction. Seepage holes are provided on the bottom surface and the surrounding wall of the trough body. A flexible filter screen is laid on the bottom surface and the surrounding wall of the trough body. There are gaps between the trough bodies. There is soil inside the filter screen in the trough body. Plants above the bed body B are located in the trough body. The height of the trough body is lower than the water distribution overflow pipe. The water distribution overflow pipe is located above the trough body. An inverted U-shaped siphon drain pipe is installed at the bottom of the bed body B. The top of the siphon drain pipe is lower than the C-shaped water collecting pipe, and the outlet of the siphon drain pipe is located in the drainage ditch.

[0005] Furthermore, there is a cavity in the filler of the bed B located below the top of the siphon drain pipe, and the cavity has a cavity, the mouth of the cavity is a constricted mouth, and the mouth of the cavity faces downward.

[0006] Furthermore, the water outlet on the water distribution overflow pipe is located on both sides of the lower part, and an open pipe is fixedly arranged outside the water distribution overflow pipe, the opening of the open pipe is downward, and a plurality of comb-shaped teeth are fixedly connected to the inner wall of the open pipe.

[0007] Furthermore, a recoil pipe is connected to the water distribution main pipe, a pumping pipe is fixedly connected to the end of the C-shaped water collecting pipe, and valves are installed on the recoil pipe and the pumping pipe.

[0008] Furthermore, the length ratio of the bed A to the bed B is 1:1.2-2.5.

[0009] Furthermore, there are multiple siphon drain pipes, and the top ends of the multiple siphon drain pipes are located at at least two heights.

[0010] Furthermore, a plurality of holes are provided on the wall of the vertical pipe of the siphon drainage pipe located in the bed B near the lower end, and the plurality of holes are located at different heights.

[0011] The operating method of the artificial wetland system for domestic sewage treatment adopts the above-mentioned artificial wetland system for domestic sewage treatment. When the wetland system is running and water is taken in, the regulating valve on the water distribution main pipe is opened to allow the water to be treated to enter the bed body A. When the water distribution overflow pipe is opened to flow water, the regulating valve is closed to allow the water to stay in the bed body A for 3-4 hours; then the regulating valve is opened to continue to take in water, and the water enters the bed body B through the water distribution overflow pipe and the trough body. The size of the regulating valve is adjusted to allow the siphon drainage pipe in the bed body B to siphon drainage once every 3-6 hours, and the drainage time is 15-40 minutes.

[0012] Furthermore, when the bed A is blocked, the regulating valve is closed, and a water pump is connected to the recoil pipe and the pumping pipe for backwashing, and the backwashing water enters from the recoil pipe and flows out from the pumping pipe.

[0013] The positive and beneficial technical effects of the present invention are: the present invention can better carry out the denitrification and nitrification processes in denitrification, the denitrification effect is good, and the utilization of plants is sufficient. The specific benefits are explained together with the description in the specific implementation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the present invention.

[0015] Figure 2 yes Figure 1 Schematic diagram of the upper part of the center isolation wall.

[0016] Figure 3 It is a schematic diagram of the tank body.

[0017] Figure 4 It is a cross-sectional schematic diagram of the water distribution overflow pipe.

[0018] Figure 5 It is a schematic diagram of cavity oxygenation and nitrification. DETAILED DESCRIPTION

[0019] In order to more fully explain the implementation of the present invention, implementation examples of the present invention are provided. These implementation examples are merely elaborations of the present invention and do not limit the scope of the present invention.

[0020] The marks in the attached drawings are: 1: bed body A; 2: bed body B; 3: water inlet channel; 4: water distribution pipe; 5: regulating valve; 6: tank body; 7: plant; 8: backwash pipe; 9: water extraction pipe; 10: siphon drain pipe; 11: hole; 12: partition wall; 13: C-shaped water collecting pipe; 14: water distribution overflow pipe; 141: water outlet hole; 15: water; 16: open pipe; 161: comb teeth; 17: cavity body; 171: cavity; 172: constriction 18: water distribution main pipe;

[0021] As shown in the attached drawings, an artificial wetland system for treating domestic sewage includes a pool body and a bed body located in the pool body. The bed body includes multiple layers of fillers. In this embodiment, the filler of the bed body is the same as usual. There are three layers in this case. The three layers of fillers increase in size from top to bottom. The fillers and plants of artificial wetlands are currently known technologies. The fillers can be cheap gravel, and zeolite, vermiculite, limestone and other known fillers can be used. The particle size of the upper filler is about 2mm, the particle size of the middle layer is about 4mm, and the particle size of the lower layer is about 6-7mm. There is a soil layer above the bed body, and plants 7 are planted in the soil layer. The water inlet of the bed body is connected to the water distribution main pipe 18. A regulating valve 5 is installed on the water distribution main pipe. The regulating valve can adjust the water inlet. The water distribution main pipe is connected to multiple parallel water distribution branch pipes 4 through a transverse pipe. The transverse pipe is a pipe that is consistent with the width direction of the pool body. A plurality of water distribution holes are opened on the water distribution branch pipe located in the bed body A. The water distribution pipes and water distribution holes are all known in the prior art. The water distribution main pipe is connected with a recoil pipe 8, and a partition wall 12 is arranged in the pool body. The partition wall divides the bed body into bed A1 and bed B2 from the water inlet to the water outlet. The length ratio of the bed body A to the bed body B is 1:1.2-2. The water distribution branch pipe 4 enters from the lower part of the pool body A, and the water distribution branch pipe enters from the bottom. Due to the continuous water inflow in the artificial wetland, the water overflows from bottom to top, which can effectively avoid the upper part of the soil being flushed, causing it to enter the bed body A and cause blockage, and can extend the service life of the wetland.

[0022] A C-shaped water collecting pipe 13 is fixedly arranged on the upper part of the isolation wall along the left and right horizontal directions, and a water extraction pipe is fixedly connected to the end of the C-shaped water collecting pipe. Valves are installed on the backwash pipe and the water extraction pipe.

[0023] The opening of the C-type water collecting pipe is toward the side of the bed A, and a filter screen is fixedly installed on the opening of the C-type water collecting pipe to prevent the entry of fillers. A plurality of horizontal front-to-back water distribution overflow pipes 14 are fixedly connected to the C-shaped water collecting pipe along the width direction, and a plurality of water outlet holes 141 are opened on the water distribution overflow pipe. The water outlet holes on the water distribution overflow pipe are located on both sides of the lower part, and an open pipe 16 is fixedly arranged outside the water distribution overflow pipe. The opening of the open pipe is downward, and a plurality of comb teeth 161 are fixedly connected to the inner wall of the open pipe. This design is intended to minimize the interference between the water flowing out of the water outlet hole 141 and the soil part in the trough body, to prevent the water from carrying fine particles into the bed B, and to extend the life of the bed B.

[0024] A plurality of trough bodies 6 are fixedly arranged along the left and right directions on the upper part of the bed body B, and water seepage holes are opened on the bottom surface and the surrounding wall of the trough body. A flexible filter screen is laid on the bottom surface and the surrounding wall of the trough body. There is a gap between adjacent trough bodies, and the gap is covered with a filter screen. There is soil inside the filter screen in the trough body, and the height of the soil is below two-thirds of the height of the trough body. The plants above the bed body B are located in the trough body, and the height of the trough body 6 is lower than the water distribution overflow pipe 4; the water distribution overflow pipe is located above the trough body, and the water in the water distribution overflow pipe flows into the trough body and can be discharged from the water seepage holes and between the trough bodies through the filter screen. The filter can prevent particles from entering the bed B and causing blockage. The trough can prevent soil loss and can also precipitate the water from the overflow water pipe. When the amount of sediment in the trough is large, it is located on the surface, which is convenient for manual cleaning. Since the water entering the bed B passes through the trough sedimentation and filter, it is not easy to cause blockage of the bed B, which is beneficial to extend the service life of the bed B. When water enters the trough, the degradation effect of plants on sewage can be fully utilized. Since water continues to flow into the bed A, there is always water in the trough, and the plants continue to degrade the water.

[0025] The bed B has a cavity 17 in the filler below the top of the siphon drain pipe. More specifically, the cavity is located in the filler above the hole 11 on the wall of the siphon pipe. The cavity has a cavity 171. The mouth of the cavity is a constricted mouth 172. The mouth of the cavity faces downward. The particle size of the cavity is adapted to the size of the filler in the layer. The cavity can be made of fired ceramic or other inorganic minerals with greater hardness. The function of the cavity is to store air in the cavity when the liquid level rises to provide oxygen for the nitrification reaction. Gas source, because the liquid level rises from bottom to top, when the cavity is flooded by water, the gas cannot be discharged after the constricted part is sealed by water, so a "microreactor" that can carry out nitrification reaction is formed inside the bed B, which is conducive to nitrification of water. The proportion of the cavity in the filler is more suitable between 20% and 40%. The larger the proportion, the more microreactors will be installed. An inverted U-shaped siphon drain pipe 10 is installed at the bottom of the bed B. The top of the siphon drain pipe is lower than the C-type water collecting pipe, and the outlet of the siphon drain pipe is located in the drainage channel. The siphon drain pipe is multiple, and the tops of the multiple siphon drain pipes are located at at least two heights. The siphon drain pipes are of the same model, the top is high, and the bottom is also raised accordingly. In practice, only one of the siphon drain pipes is too high, and the siphon drain pipes are of the same model, the top is high, and the bottom is also raised accordingly. This design is mainly for the water inlet of the lower siphon drain pipe to fail and cannot produce siphon. Under normal circumstances, the siphon drain pipe with a high top does not produce siphon drainage. A plurality of holes 11 are provided on the wall of the vertical pipe of the siphon pipe located near the lower end in the bed B, and the plurality of holes are located at different heights. The function of the holes is to destroy the siphon when the water level drops to the holes during siphon drainage, so that the siphon drainage pipe stops draining water, so that the water that enters the bed B for a period of time before and during the siphon drainage is retained in the bed B for a relatively thorough denitrification process, and a certain height of water is stored at the bottom of the bed B for a long time, so as to maintain a good anoxic environment, so that the lower part of the bed B basically becomes a denitrification zone completely isolated from the air, and the overall denitrification effect is improved.

[0026] The water in the inlet channel has been intercepted for suspended solids and initially filtered and precipitated, or it is the tail water that has been treated accordingly in the sewage treatment plant. Before the artificial wetland is operated, the denitrifying bacteria of the A / O process are connected to the bed A, and the sludge in the secondary sedimentation tank of the A / O process is connected to the bed B. When the artificial wetland is in operation, the bed A is filled with water, creating a good anoxic environment. The denitrifying bacteria are not easily destroyed, which is conducive to the denitrification. The carbon source in the sewage that has not been biochemically treated can meet the needs of denitrification. The NO2- and NO3- in the water in the bed A are under anoxic conditions and the action of the denitrifying bacteria The water in the upper part of the bed A can be in full contact with the plants and degraded by the plants. The water in the water distribution overflow pipe enters the tank body and then falls into the bed B after sedimentation, filtration and plant degradation. The liquid level of the bed B is at the bottom after siphoning. The upper part is in a void state with sufficient oxygen. The water is in full contact with the oxygen during the falling process through the filler. When the water falls to the liquid surface, it can also produce a waterfall oxygenation effect, providing an aerobic environment for the nitrification reaction. The water under the liquid surface can continue the nitrification reaction by utilizing the reoxygenation of the bed B when the water level drops. When the water level of the bed B rises, the shrinkage at the bottom of the cavity The air enclosed in the bed B can also form a local nitrification reactor, so the upper part of the bed B adopts a variety of methods to provide aerobic conditions for the bed B, which is very conducive to a more thorough nitrification reaction. Good conditions are provided for the nitrification reaction near the liquid surface and above the liquid surface, which is conducive to the nitrification reaction. Ammonia nitrogen in the bed B is converted into NO2- and NO3- under the action of nitrifying bacteria, while the environment below the liquid surface is relatively anoxic. The more strict anoxic environment at the bottom of the bed B provides good conditions for denitrification. Therefore, after the nitrification reaction, the NO2- and NO3- in the water are in anoxic conditions. Under the conditions and the action of denitrifying bacteria, it can be reduced to N2, so that the water that has undergone denitrification in bed A and then passed through the roots of plants and fell into pool B from top to bottom will experience nitrification and denitrification processes successively. The concentrations of NH4+ and NO3- (NO2) are greatly reduced, and the height range of the nitrification reaction in pool B is relatively stable, which is conducive to the growth and stability of the bacterial community and has a good denitrification effect. When the liquid level reaches the top of the siphon drain pipe, a siphon effect is generated and drainage begins. Oxygen will be inhaled during the drainage process. Repeated water inflow and drainage make the renewal of nitrification biofilm faster, which is more conducive to denitrification. Artificial wetland plants can be reeds, lotus, etc., which are currently commonly used. When the wetland system is inflowing, open the regulating valve on the water distribution main pipe to allow the water to be treated to enter the bed A. When the water distribution overflow pipe is opened to flow water, close the regulating valve to allow the water to stay in the bed A for 3-4 hours; then open the regulating valve to continue to let water in, and the water enters the bed B through the water distribution overflow pipe and the trough body. Adjust the size of the regulating valve to make the siphon drainage pipe in the bed B siphon drainage every 3-6 hours, and the drainage time is 15-40 minutes.When the bed A is blocked, close the regulating valve, connect water pumps to the recoil pipe and the suction pipe respectively for backwashing, and the backwashing water enters from the recoil pipe and flows out from the suction pipe.

[0027] In order to verify the effectiveness of oxygenation of the technical solution of the present application, a simulation and comparative experiment was carried out on the oxygenation part of the technical solution in the laboratory. The experiment used two boxes with a length of 0.5m, a width of 0.2m and a depth of 0.6. One of the boxes was separated by a partition (isolation wall) at a length of 0.2. Gravel was used as filler in the experiment. The upper layer was 0.15m thick, the middle layer was 0.3m thick, and the lower layer was 0.15m thick. The upper layer, the middle layer, and the junction of the middle layer and the lower layer in the pool body behind the partition were filled with small ceramic gourd medicine bottles purchased online. The size was basically the same as the particle size of the corresponding layer, and the filling ratio was about 20%. The opening of the ceramic gourd medicine bottle faced downward, and the small hole on the siphon was 10mm away from the bottom. The sewage used was modulated sewage, with a COD of 110mg / L and an ammonia nitrogen of 40mg / L. The one without a partition was Pool A. Pool B has a baffle. Both pools are inletted from the front bottom with a small water pump with controllable flow. Pool A is connected to the secondary sedimentation tank sludge in A / O treatment, and the sludge in the denitrification tank is connected in front of the baffle of Pool B, and the sludge in the secondary sedimentation tank is connected behind the baffle. Pool B uses an overflow pipe to distribute water from the upper part of the baffle. Pool A is operated by tidal flow with an operation cycle of 10 hours. Pool B is siphoned off once every 5 hours. After stable operation, its drainage indicators are measured. The COD removal rate of Pool A is about 33-39%, and the ammonia nitrogen removal rate is about 20-24%. The COD removal rate of Pool B is about 50-56%, and the ammonia nitrogen removal rate is about 33-38%. Due to time constraints, no plants were involved in the above experiments. The above experiments prove that this scheme should have a good nitrification effect, and the removal rate of ammonia nitrogen is significantly improved compared with the tidal flow.

[0028] After describing the implementation mode of the present invention in detail, people familiar with the technology can clearly understand that various changes and modifications can be made without departing from the scope and spirit of the above-mentioned patent application. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are within the scope of the technical solution of the present invention, and the present invention is not limited to the implementation mode of the examples given in the specification.

Claims

1. An artificial wetland system for sewage treatment, comprising a pool body, a bed body located in the pool body, the bed body comprising multiple layers of fillers, the multiple layers of fillers are arranged in order of increasing particle size from top to bottom, there is a soil layer above the bed body, plants are planted in the soil layer, the water inlet of the bed body is connected to a water distribution main pipe, a regulating valve is installed on the water distribution main pipe, and a plurality of parallel water distribution branches are connected to the water distribution main pipe through a horizontal pipe, characterized in that: A partition wall is arranged in the pool body, which divides the bed body into bed body A and bed body B from the water inlet to the water outlet direction. The water distribution branch pipe enters from the lower part of bed body A, and a C-type water collecting pipe is fixedly arranged along the left and right horizontal directions on the upper part of the partition wall. The opening of the C-type water collecting pipe faces the side of bed body A, and a filter screen is fixedly installed on the opening of the C-type water collecting pipe to prevent the entry of fillers. A plurality of horizontal front-to-back water distribution overflow pipes are fixedly connected to the C-type water collecting pipe along the width direction, and a plurality of water outlet holes are opened on the water distribution overflow pipe. A plurality of trough bodies are fixedly arranged on the upper part of bed body B along the left and right directions, and water seepage holes are opened on the bottom surface and the surrounding wall of the trough body. A flexible filter screen is laid on the bottom surface and the surrounding wall of the trough body, and there is a gap between the trough bodies. There is soil in the filter screen in the trough body, and plants above bed body B are arranged on the bottom surface and the surrounding wall of the trough body. It is located in the trough body, and the height of the trough body is lower than the water distribution overflow pipe. The water distribution overflow pipe is located above the trough body. An inverted U-shaped siphon drain pipe is installed at the bottom of the bed body B. The top of the siphon drain pipe is lower than the C-type water collecting pipe, and the outlet of the siphon drain pipe is located in the drainage channel; there is a cavity in the filler of the bed body B located below the top of the siphon drain pipe, and there is a cavity on the cavity body, the mouth of the cavity is a contraction, and the mouth of the cavity faces downward; the water outlet on the water distribution overflow pipe is located on both sides of the lower part, and an open pipe is fixedly provided outside the water distribution overflow pipe, the opening of the open pipe is downward, and a plurality of comb-shaped teeth are fixedly connected to the inner wall of the open pipe; a recoil pipe is connected to the water distribution main pipe, and a pumping pipe is fixedly connected to the end of the C-type water collecting pipe, and valves are installed on the recoil pipe and the pumping pipe.

2. The artificial wetland system for sewage treatment according to claim 1, characterized in that: The length ratio of the bed body A to the bed body B is 1:1.2-2.

5.

3. The artificial wetland system for sewage treatment according to claim 1, characterized in that: There are at least two siphon drainage pipes, and the top ends of the two siphon drainage pipes are located at different heights.

4. The artificial wetland system for sewage treatment according to claim 1, characterized in that: A plurality of holes are provided on the pipe wall of the vertical pipe of the siphon drainage pipe located in the bed body B near the lower end, and the plurality of holes are located at different heights.

5. A method for operating an artificial wetland system for sewage treatment, using the artificial wetland system for sewage treatment according to claim 1, characterized in that: When the wetland system is running and water is entering, open the regulating valve on the water distribution main pipe to allow the water to be treated to enter the bed A. When the water distribution overflow pipe begins to flow, close the regulating valve to allow the water to stay in the bed A for 3-4 hours; then open the regulating valve to continue to let water in, and the water enters the bed B through the water distribution overflow pipe and the trough body. Adjust the size of the regulating valve to allow the siphon drainage pipe in the bed B to siphon drainage every 3-6 hours, and the drainage time is 15-40 minutes.

6. The method for operating a constructed wetland system for sewage treatment according to claim 5, characterized in that: When the bed A is blocked, close the regulating valve, connect water pumps to the recoil pipe and the suction pipe respectively for backwashing, and the backwashing water enters from the recoil pipe and flows out from the suction pipe.

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