Design of selective constructed wetland for treating town sewage
By switching the undercurrent mode in different seasons and selective artificial wetland systems using multi-layer filler structures, the problem of low treatment efficiency in winter is solved, and efficient removal of nitrogen and phosphorus pollutants and reducing costs is achieved.
Patent Information
- Application Number
- CN202410085374.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-01-20
- Publication Date
- 2025-07-22
AI Technical Summary
The existing artificial wetland systems have low efficiency in treating tailwater in winter and have high site costs, making it difficult to effectively remove nitrogen and phosphorus pollutants.
A selectable artificial wetland system is designed to use a multi-layer filler structure for sewage treatment by switching horizontal and vertical undercurrent modes in different seasons, combined with the growth period of reeds and water onions.
It improves the efficiency of winter tail water treatment, reduces site costs, and effectively removes nitrogen and phosphorus pollutants.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to the field of sewage purification, and particularly to a flexible application of a selective constructed wetland system in seasonal changes, belonging to the technical field of wastewater treatment. Background Art
[0002] Constructed wetland is a relatively suitable process for treating tail water. Constructed wetlands are divided into surface flow constructed wetlands and subsurface flow constructed wetlands. Surface flow constructed wetlands have advantages such as simple structure and low cost investment. However, in practice, they are extremely prone to attracting mosquitoes and flies, and especially in summer, they are prone to emitting odors, which will affect the surrounding ecological environment. Moreover, in the actual sewage treatment process, some trace elements will be absorbed by the soil, plants, or microbial colonies during the sedimentation process and continuously circulate in the entire wetland ecosystem, and cannot be thoroughly treated.
[0003] Subsurface flow constructed wetlands are further divided into horizontal subsurface flow constructed wetlands and vertical subsurface flow constructed wetlands. In a horizontal subsurface flow constructed wetland, the sewage will flow under the surface of the bed body of the system. The first stage that the sewage passes through is the root zone filler layer of the water distribution system. The filler layer is mainly composed of porous substances and aquatic plants. Aquatic plants with relatively developed roots should be selected to ensure that the roots of the plants are intricate, so that the plants can better cooperate with the filler, and then form a system with good water permeability. This part can largely treat the suspended solids in the sewage. At the same time, the plants will also produce more oxygen, which is extremely beneficial to the survival of aerobic microorganisms in the surrounding environment. The horizontal subsurface flow constructed wetland is less affected by seasonal temperature changes and can make good use of the synergistic effect among the fillers, emergent plants, and microorganisms in the system to remove pollutants in the water body, and has good treatment effects on solid suspended matter, organic matter, and heavy metals. However, the nitrification effect is not ideal, and the subsequent nitrogen removal process is restricted to a certain extent; in a vertical subsurface flow constructed wetland, the sewage generally flows on the wetland surface in a vertical flow state from the bottom of the substrate bed, so as to achieve the effect of treating sewage. The vertical subsurface flow constructed wetland has a better sewage treatment effect than the horizontal subsurface flow constructed wetland, but it is prone to clogging. The horizontal subsurface flow constructed wetland and the vertical subsurface flow constructed wetland both have their own advantages. If the two are combined, their advantages will be better exerted.
[0004] The operation effect of constructed wetlands is susceptible to environmental temperature. The influence of temperature on the removal of total phosphorus and ammonia nitrogen in wetlands is that the removal rate is low at low temperatures and high at high temperatures. In subsurface flow constructed wetland systems, the removal of total phosphorus and ammonia nitrogen mainly relies on polyphosphate-accumulating organisms (PAOs) and nitrifying bacteria and nitrite bacteria under aerobic or anoxic conditions. During biological phosphorus removal, PAOs use molecular oxygen or combined oxygen as electron acceptors, oxidize and metabolize PHB or PHV, etc., and generate energy. They excessively uptake phosphate from sewage, and the energy is stored in the form of high-energy substance ATP. Part of it is converted into polyphosphate and stored in the cells as energy, and high-efficiency biological phosphorus removal is achieved through the discharge of excess sludge. During biological nitrogen removal, nitrifying bacteria obtain energy by oxidizing inorganic compounds through nitrification to meet their own energy requirements, and use CO2 as the only carbon source. They are typical chemoautotrophic bacteria. Research shows that temperature affects the rate of microbial enzymatic reactions. Johnson K found that when the environmental temperature is 15 - 30 °C, the biological phosphorus removal efficiency increases with the increase of temperature. When the temperature is higher than 30 °C, the biological phosphorus removal efficiency begins to decrease. During the period from November to March, the wet environmental temperature ≤ 15 °C, and the removal rate of total phosphorus in the wetland ≤ 20%. When the wetland temperature > 15 °C, the maximum removal rate of total phosphorus in June is 43.47%. The average environmental temperature from November to April is 9 °C, and the average removal rate of ammonia nitrogen in the wetland is 5.58%. When the wetland temperature > 15 °C, the removal rate of ammonia nitrogen ≥ 30%. The removal rate of ammonia nitrogen is the highest in October, which is 59.01%. Therefore, improving the treatment efficiency of constructed wetlands in winter and reducing site costs have become new research directions for treating tail water with constructed wetlands. Summary of the Invention
[0005] Object of the Invention: In order to improve the efficiency of treating tail water in winter and reduce site costs at the same time, the present invention provides a selective constructed wetland system.
[0006] Technical Solution: To achieve the above object, the technical solution adopted by the present invention is as follows:
[0007] A design of a selective constructed wetland for treating urban tail water, which includes the following steps:
[0008] (1) Inlet unit: The adsorption unit is connected to the subsurface flow unit through two inlet pipes. Valves are provided on both inlet pipes. In spring and summer, the valve of inlet pipe 1 is opened, and horizontal subsurface flow is adopted. In autumn and winter, the valve of inlet pipe 2 is opened, and vertical subsurface flow is adopted. Reed and scallion are planted in the subsurface flow unit. The growth period of reed is in spring and summer. After withering and harvesting in autumn, it can be spread on the surface of the covering layer for heat preservation. The growth period of scallion is in autumn and winter, and it can be used for tail water purification treatment.
[0009] (2) Subsurface flow unit: The subsurface flow unit is provided with a drainage layer (iron-rich gravel, particle size 50 - 60 mm), a filter layer (biochar + limestone + iron-rich gravel, particle size 5 - 15 mm), and a covering layer (iron-rich gravel, particle size 8 - 16 mm) in sequence from bottom to top. The thickness of the drainage layer is 200 mm, the thickness of the filter layer is 700 mm, and the covering layer is 100 mm.
[0010] (3) Overall process: A through hole 1 is provided at the bottom of the water inlet unit and is communicated with the adsorption unit. An adsorption component is arranged inside the adsorption unit, and two water inlet pipes extending into the subsurface flow unit are installed on the upper part. Valves are installed on the surfaces of the water inlet pipes for convenient switching to vertical subsurface flow during seasonal changes. The water inlet pipe 1 is used for horizontal subsurface flow in spring and summer seasons. A through hole 2 is provided at the upper part on the side far from the adsorption unit and is communicated with the sedimentation unit; the water inlet pipe 2 is used for vertical subsurface flow in autumn and winter seasons. Multiple through holes are opened on the surface of the water inlet pipe 2 for vertical subsurface flow of the tail water. A through hole 3 is provided at the bottom on the side far from the adsorption unit and is communicated with the sedimentation unit.
[0011] Beneficial effects: The tail water first enters the water inlet unit and the adsorption unit in sequence, and impurities are adsorbed by activated carbon in the adsorption unit. Then the tail water enters the subsurface flow unit. In spring and summer seasons, the inlet pipe 1 is used, and horizontal subsurface flow is used for tail water purification treatment. In autumn and winter seasons, the inlet pipe 2 is used, and vertical subsurface flow is used for tail water purification treatment. Then the tail water enters the sedimentation unit to further purify the tail water so that it meets the requirements and is discharged. By setting two inlet pipes in this application, the selectivity of the constructed wetland can be realized, while reducing the site cost and improving the efficiency of treating urban tail water in winter. Description of the Drawings
[0012] Figure 1 It is the overall design drawing of the selective constructed wetland
[0013] Figure 2 It is the sectional view of the selective constructed wetland design
[0014] Figure 3 It is the top view of the selective constructed wetland
[0015] Figure 4 It is the sectional view of the packing of the subsurface flow unit Detailed Implementation Manner
[0016] The following further describes this application in detail with reference to the drawings.
[0017] 1. Referring to Figure 1 and Figure 2 , a selective constructed wetland system provided by this application includes a water inlet unit, an adsorption unit, a subsurface flow unit, and a sedimentation unit that are connected in sequence and arranged in a row along the same straight line direction.
[0018] 2. Refer to Figure 3 , the adsorption unit is connected to the subsurface flow unit through two inlet pipes, and valves are installed on both inlet pipes. In spring and summer, the valve of the inlet pipe 1 is opened to adopt horizontal subsurface flow; in autumn and winter, the valve of the inlet pipe 2 is opened to adopt vertical subsurface flow. Reed and softstem bulrush are planted in the subsurface flow unit. The growth period of reed is in spring and summer, and after withering and harvesting in autumn, it can be spread on the surface of the covering layer for heat preservation. The growth period of softstem bulrush is in autumn and winter, and it can be used for tail water purification treatment.
[0019] 3. Refer to Figure 4 and Table 1, the subsurface flow unit is sequentially provided with a drainage layer (ferric-rich gravel, particle size 50 - 60 mm), a filter layer (biochar + limestone + ferric-rich gravel, particle size 5 - 15 mm), and a covering layer (ferric-rich gravel, particle size 8 - 16 mm) from bottom to top. The thickness of the drainage layer is 200 mm, the thickness of the filter layer is 700 mm, and the covering layer is 100 mm.
[0020] Table 1 Composition of the packing layer of the subsurface flow unit
[0021]
Claims
1. An optional constructed wetland system, characterized in that: The selective constructed wetland system includes an inlet unit, an adsorption unit, a subsurface flow unit, and a sedimentation unit arranged in sequence. A through-hole 1 is provided at the bottom of the inlet unit to communicate with the adsorption unit. An adsorption assembly is arranged inside the adsorption unit, and two inlet pipes extending into the subsurface flow unit are installed at the upper part. Valves are installed on the surfaces of the inlet pipes to facilitate switching to vertical subsurface flow during seasonal changes. Inlet pipe 1 is used for horizontal subsurface flow in spring and summer. A through-hole 2 is provided at the upper part on the side far from the adsorption unit and communicates with the sedimentation unit. Inlet pipe 2 is used for vertical subsurface flow in autumn and winter. A plurality of through-holes are opened on the surface of inlet pipe 2 for vertical subsurface flow of the tail water. A through-hole 3 is provided at the bottom on the side far from the adsorption unit and communicates with the sedimentation unit. By adopting the above technical solution, the tail water first enters the inlet unit and the adsorption unit in sequence, and impurities are adsorbed by activated carbon in the adsorption unit. Then the tail water enters the subsurface flow unit. In spring and summer, inlet pipe 1 is used, and horizontal subsurface flow is used for purifying the tail water. In autumn and winter, inlet pipe 2 is used, and vertical subsurface flow is used for purifying the tail water. Then the tail water enters the sedimentation unit to further purify the tail water so that it meets the requirements and is discharged. By setting two inlet pipes in this application, the selectivity of the constructed wetland can be realized, the site cost is reduced, and the efficiency of treating urban tail water in winter is improved. Inside the subsurface flow unit, a drainage layer (ferric gravel, particle size 50 - 60 mm), a filter layer (biochar + limestone + ferric gravel, particle size 5 - 15 mm), a covering layer (ferric gravel, particle size 8 - 16 mm), and aquatic plants (Phragmites australis, Scirpus validus) are arranged from bottom to top in sequence. By adopting the above technical solution, in spring and summer, the tail water enters the subsurface flow unit through inlet pipe 1, and the horizontal subsurface flow mode is adopted. It passes through Phragmites australis and the covering layer and enters the sedimentation unit through through-hole 2. In autumn and winter, the tail water enters the subsurface flow unit through inlet pipe 2, and the vertical subsurface flow mode is adopted. It passes through Scirpus validus, the covering layer, the filter layer, and the drainage layer from top to bottom, so that the tail water is purified and enters the sedimentation unit through through-hole 3. In summary, the present invention has the following technical effects: 1) By arranging an inlet unit, an adsorption unit, a subsurface flow unit, and a sedimentation unit that are connected in sequence, the urban tail water is purified step by step, improving the tail water treatment effect. 2) By installing valves on both inlet pipes, the constructed wetland has selectivity. Horizontal subsurface flow treatment is adopted in spring and summer, and vertical subsurface flow treatment is adopted in autumn and winter. 3) By planting Phragmites australis and Scirpus validus in the subsurface flow unit, the growth period of Phragmites australis is in spring and summer. After withering in autumn, it can be harvested and spread on the surface to achieve a heat preservation effect. The growth period of Scirpus validus is in autumn and winter, which can improve the treatment efficiency of the constructed wetland in autumn and winter.