Denitrification-enhanced sewage treatment tail water constructed wetland system

Abstract

A sewage treatment tail water constructed wetland system for enhanced denitrification comprises a plurality of unit wetlands, each unit wetland is composed of water inlet ditches on the two sides, a horizontal subsurface flow type wetland in the middle, a vertical subsurface flow type wetland on the lower portion and a drainage channel on the drainage side, and water permeable pore plates are arranged between the horizontal subsurface flow type wetlands and the water inlet ditches. The vertical subsurface flow type wetland comprises a water collecting ditch and a water collecting pipe and is communicated with the drainage channel through a drainage well, the horizontal subsurface flow type wetland comprises aeration areas which are symmetrically arranged by taking the water collecting ditch as the center, micropore aeration pipes and bottom gravels are arranged in the aeration areas, upper gravels and surface soil are laid on the top surfaces, and aquatic plants are planted; according to the structure, nitrification and denitrification reaction zones are strengthened, the denitrification efficiency is improved, wetland surface soil prevents a water body from making contact with the atmosphere, heat preservation is conducted in winter, the microbial activity is kept through bottom aeration, the total nitrogen removal rate in winter is increased, the sewage treatment efficiency and the running stability in winter are effectively improved, and the system has remarkable environmental protection and economic benefits.

Description

Technical Field

[0001] The utility model relates to the technical field of sewage treatment, in particular to an artificial wetland system for treating the tail water of sewage with enhanced nitrogen removal. Background Art

[0002] The artificial wetland sewage treatment system is a new type of ecological sewage treatment technology developed on the basis of the purification of natural wetlands, and has the characteristics of good pollution purification effect, low operation cost and easy maintenance. Its essence is actually a combination of numerous A1 / O biological nitrogen removal processes. The removal effect of pollutants is affected and restricted by various factors, such as dissolved oxygen in the wetland, air temperature, wetland plants, wetland microorganisms, etc. These factors can all limit the further improvement of the wetland purification effect and become an important factor restricting the popularization and application of wetlands. At present, it is considered that the subsurface flow type artificial wetland is a wetland type with better application effect, but there are still many problems in the subsurface flow type artificial wetland, such as hypoxia inside the wetland. The oxygen transported to the roots by the photosynthesis of aquatic plants can basically only meet the respiration of plant roots. The oxygen required by aerobic microorganisms mainly comes from the reoxygenation of the atmosphere on the water surface, and with the increase of water depth, it becomes an anoxic and anaerobic environment. In winter at low temperature, the water body communicates with the atmosphere, the water temperature decreases, the microbial activity decreases, affecting the nitrogen removal effect. At the same time, after the aquatic plants wither and are harvested in winter, the dissolved oxygen concentration in the root water body is even lower, becoming an anoxic or anaerobic state, and the number of aerobic microorganisms decreases by an order of magnitude, affecting the progress of the nitrification reaction. Content of the Utility Model

[0003] The utility model provides an artificial wetland system for treating the tail water of sewage with enhanced nitrogen removal to eliminate the potential safety hazards of the reverse operation of the man-riding vehicle, aiming at solving the deficiencies of the prior art.

[0004] To achieve the above object, the utility model first proposes an artificial wetland system for treating the tail water of sewage with enhanced nitrogen removal, which includes a plurality of unit wetlands. Each unit wetland includes inlet ditches on both sides, a horizontal subsurface flow type wetland arranged between the inlet ditches on both sides, a vertical subsurface flow type wetland arranged below the horizontal subsurface flow type wetland, and a drainage channel arranged on the drainage side of the unit wetland. The inlet ditch and the horizontal subsurface flow type wetland are separated by a permeable orifice plate. The vertical subsurface flow type wetland includes a water collecting ditch arranged in the middle of the unit wetland and parallel to the inlet ditch. A water collecting pipe is arranged at the bottom of the water collecting ditch, and the outlet of the water collecting pipe is communicated with the drainage channel through a drainage well. Bottom gravel and middle gravel are sequentially arranged from bottom to top in the water collecting ditch to form a vertical subsurface flow type wetland.

[0005] The horizontal subsurface flow wetland includes pits symmetrically arranged on both sides of the collection ditch with the collection ditch as the center to form an aeration area. Multiple microporous aeration pipes are arranged in the aeration area. The microporous aeration pipes are arranged in the same direction as the water collection pipe. The aeration area is filled with bottom gravel. The top surface of the aeration area and the top surface of the collection ditch are successively paved with upper gravel and surface soil from bottom to top to form a horizontal subsurface flow wetland. Aquatic plants are planted on the surface soil.

[0006] In this embodiment, the water inlet ditch is 40 cm deep, and a cover plate is provided on the water inlet ditch for sealing.

[0007] In this embodiment, the width of the horizontal subsurface flow wetland between the two water inlet ditches is 2A, where A ≤ 5 m. The depth of the horizontal subsurface flow wetland is 0.4 m. The width of the collection ditch is 0.8 m, and the depth is (0.2 - 0.25) × A.

[0008] In this embodiment, the width of the aeration area is B, where B < A - 0.4 m, and the depth h of the aeration area > 0.2 m.

[0009] In this embodiment, three microporous aeration pipes are evenly arranged in the aeration area. A porous protection pipe is sleeved outside the microporous aeration pipe. The air inlet end of the microporous aeration pipe is connected to the pipeline of a Roots blower.

[0010] In this embodiment, the particle size of the bottom gravel is 40 - 60 mm, the particle size of the middle gravel is 20 - 40 mm, and the particle size of the upper gravel is 10 - 30 mm.

[0011] In this embodiment, the aquatic plants are reeds, cannas, dracaena sanderiana or cyperus alternifolius.

[0012] Due to the above structure, microporous aeration is formed by arranging microporous aeration pipes at the bottom of the horizontal subsurface flow wetland, thereby increasing the dissolved oxygen in the water. Due to the existence of organic matter in the root exudates of aquatic plants, aerobic microorganisms in the rhizosphere of the soil and gravel multiply vigorously, forming an obvious nitrification reaction area. The organic matter and ammonia nitrogen in the tail water enter the vertical subsurface flow wetland after a long-time nitrification reaction. The hydraulic retention times of the two areas are in a ratio of 5 - 6:1. The dissolved oxygen in the water is exhausted, forming an anoxic and anaerobic area. Under the action of denitrifying bacteria, nitrate nitrogen is denitrified to form nitrogen gas, which is discharged with the drainage or discharged into the atmosphere from the wetland.

[0013] To sum up, this structure strengthens the nitrification reaction area and the denitrification reaction area, increases the nitrogen removal efficiency. At the same time, the surface soil on the upper part of the wetland blocks the contact between the water body and the atmosphere, playing a role in water body heat preservation when the winter temperature is relatively low. At the same time, the aeration at the bottom enables the aerobic microorganisms in the roots to still maintain good activity even when the aquatic plants lack photosynthesis in winter, improving the total nitrogen removal rate of the wetland in winter. Description of the Drawings

[0014] Figure 1 This is the sectional structure diagram of the non-operating state of the present utility model;

[0015] Figure 2 This is the top view of the present utility model;

[0016] Figure 3 This is the sectional schematic diagram of the operating state of the present utility model;

[0017] Figure 4 This is the top view of the operating state of the present utility model;

[0018] Figure 5 is Figure 3 The sectional view at C.

[0019] In the figure: 1, water inlet ditch; 2, permeable orifice plate; 3, aeration area; 4, water collection ditch; 5, water collection pipe; 6, adjusting plate; 7, drainage well; 8, microporous aeration pipe; 9, bottom layer gravel; 10, middle layer gravel; 11, upper layer gravel; 12, aquatic plants; 13, surface soil; 14, drainage channel. Specific embodiments

[0020] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all of the embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present utility model.

[0021] In addition, the technical solutions between the various embodiments of the present utility model can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present utility model.

[0022] As Figures 1 to 5 shown, an artificial wetland system for treating the tail water of sewage with enhanced nitrogen removal includes a plurality of unit wetlands. The unit wetland includes water inlet ditches 1 on both sides, a horizontal subsurface flow wetland arranged between the water inlet ditches 1 on both sides, a vertical subsurface flow wetland arranged below the horizontal subsurface flow wetland, and a drainage channel 14 arranged on the drainage side of the unit wetland. The water inlet ditch 1 and the horizontal subsurface flow wetland are separated by a permeable orifice plate 2. The vertical subsurface flow wetland includes a water collection ditch 4 parallel to the water inlet ditch 1 arranged in the middle of the unit wetland. The bottom of the water collection ditch 4 is provided with a water collection pipe 5. The water outlet of the water collection pipe 5 is communicated with the drainage channel 14 through a drainage well 7. The bottom layer gravel 9 and the middle layer gravel 10 are sequentially arranged in the water collection ditch 4 from bottom to top to form a vertical subsurface flow wetland;

[0023] The horizontal subsurface flow wetland includes depression pits symmetrically arranged on both sides of the water collecting ditch 4 with the water collecting ditch 4 as the center to form an aeration zone 3. A plurality of microporous aeration pipes 8 are arranged in the aeration zone 3. The microporous aeration pipes 8 are arranged in the same direction as the water collecting pipe 5. The aeration zone 3 is filled with bottom gravel 9. The top surface of the aeration zone 3, the top surface of the water collecting ditch 4 and the bottom surface of the water inlet ditch 1 are flush; The top surface of the aeration zone 3 and the top surface of the water collecting ditch 4 are successively paved with upper gravel 11 and surface soil 13 from bottom to top to form a horizontal subsurface flow wetland, and aquatic plants 12 are planted on the surface soil 13.

[0024] As Figure 1 shown, the water inlet ditch 1 is 40 cm deep and has a cover plate. The width of the horizontal subsurface flow wetland between the two water inlet ditches 1 is 2A, A≤5m, the depth is 40 cm, the width of the water collecting ditch 4 is 80 cm, and the depth is (0.2 - 0.25)A. The width of the aeration zone 3 is B, B﹤A - 0.4m, and the depth h of the aeration zone 3>20 cm.

[0025] Furthermore, three microporous aeration pipes 8 are evenly arranged in the aeration zone 3. A porous protection pipe is sleeved outside the microporous aeration pipe 8. The air inlet end of the microporous aeration pipe 8 is connected to the Roots blower pipeline. A baffle is arranged at the outlet of the drainage well 7 to form an overflow port, and the water level of the wetland can be adjusted by adjusting the height of the baffle.

[0026] Furthermore, the particle size of the bottom gravel is 40 - 60 mm, the particle size of the middle gravel is 20 - 40 mm, and the particle size of the upper gravel is 10 - 30 mm.

[0027] In this embodiment, the surface soil 13 is the surface soil 13 reserved during the wetland excavation. The aquatic plants 12 are reeds, cannas, lucky bamboo, cyperus alternifolius, etc.

[0028] The specific construction process of this structure is as follows: Excavate the unit wetland. During excavation, the top 20 cm of soil is reserved and piled up centrally. After the construction of the wetland anti-seepage membrane and geotextile membrane in the unit wetland, install the microporous aeration pipe and its protection pipe 8, the water collecting pipe 5, fill the bottom gravel 9 and the middle gravel 10, install the permeable orifice plate 2 between the water inlet ditch and the horizontal subsurface flow wetland, fill the upper gravel 11 and the surface soil 13, plant aquatic plants 12 on the soil 13, and install the regulating plate 6 of the drainage well 7 to complete the wetland construction.

[0029] In the initial stage of the operation of the constructed wetland system, adjust the water level of the wetland below the surface soil layer, stop the water inlet, and intermittently aerate to supplement oxygen to make the aquatic plants survive. According to the growth of the plants, intermittently inlet water at an appropriate time. When the aquatic plants generate more roots in the gravel water body and a large number of microorganisms multiply, start the operation of the wetland, and according to the hydraulic retention time 4 ～Control the influent flow for 5 days to maintain the operation effect of the wetland.

[0030] Before the aquatic plants wither in winter, harvest the above-ground parts of the plants and cover them on the soil surface for heat preservation, and collect and process them before the beginning of spring.

[0031] Detect the dissolved oxygen concentration inside the wetland and in the drainage. When the dissolved oxygen concentration inside the wetland is lower than 0.5 mg / l, increase the aeration time and aeration volume to keep the dissolved oxygen concentration at 0.5 - 2 mg / l, and detect various control indicators such as total nitrogen in the influent and drainage, and compare them with the discharge standards.

[0032] The above are only the preferred embodiments of the present utility model, and do not limit the patent scope of the present utility model accordingly. Any equivalent structural transformation made under the concept of the present utility model by using the content of the specification and drawings of the present utility model, or directly / indirectly applied in other related technical fields, is included in the patent protection scope of the present utility model.

Claims

1. A sewage treatment tailwater artificial wetland system for enhanced denitrification, characterized by: The invention comprises a plurality of unit wetlands, wherein the unit wetlands comprise water inlet ditches on both sides, a horizontal submerged flow wetland arranged between the water inlet ditches on both sides, a vertical submerged flow wetland arranged below the horizontal submerged flow wetland, and a drainage channel arranged on the drainage side of the unit wetlands, the water inlet ditches and the horizontal submerged flow wetland are separated by a permeable plate, the vertical submerged flow wetland comprises a water collecting ditch arranged in the middle of the unit wetland and parallel to the water inlet ditch, a water collecting pipe is arranged at the bottom of the water collecting ditch, the water outlet of the water collecting pipe is connected to the drainage channel through a drainage well, and bottom gravel and middle gravel are arranged in sequence from bottom to top in the water collecting ditch to form a vertical submerged flow wetland; The horizontal subsurface flow wetland includes pits arranged on both sides of the water collecting ditch and symmetrically arranged with the water collecting ditch as the center to form an aeration area, the aeration area is provided with a plurality of microporous aeration pipes, the microporous aeration pipes and the water collecting pipes are arranged in the same direction, the aeration area is filled with bottom gravel, the top surface of the aeration area and the top surface of the water collecting ditch are paved with upper gravel and surface soil from bottom to top in sequence to form a horizontal subsurface flow wetland, and aquatic plants are planted on the surface soil.

2. The sewage treatment tailwater artificial wetland system for enhanced denitrification according to claim 1, characterized in that: The water inlet ditch is 40 cm deep and is closed by a cover plate.

3. The sewage treatment tailwater artificial wetland system for enhanced denitrification according to claim 1, characterized in that: The width of the horizontal subsurface flow wetland between the inlet ditches on both sides is 2A, A≤5m, the depth of the horizontal subsurface flow wetland is 0.4m, the width of the collection ditch is 0.8m, and the depth is (0.2~0.25)×A.

4. The sewage treatment tailwater artificial wetland system for enhanced denitrification according to claim 1, characterized in that: The width of the aeration zone is B, B﹤A-0.4m, and the depth of the aeration zone is h>0.2m.

5. The sewage treatment tailwater artificial wetland system for enhanced denitrification according to claim 1, characterized in that: Three microporous aeration tubes are evenly distributed in the aeration zone, a porous protection tube is sheathed outside the microporous aeration tube, and an air inlet end of the microporous aeration tube is connected to the Roots blower pipeline.

6. The sewage treatment tailwater artificial wetland system for enhanced denitrification according to claim 1, characterized in that: The particle size of the bottom layer gravel is 40-60 mm, the particle size of the middle layer gravel is 20-40 mm, and the particle size of the upper layer gravel is 10-30 mm.

7. The sewage treatment tailwater artificial wetland system for enhanced denitrification according to claim 1, characterized in that: Aquatic plants include reeds, cannas, lucky bamboo or windmill grass.

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