CN104326574A - Horizontal subsurface wetland system for intensifying denitrification of micro-polluted water in winter - Google Patents

Abstract

The invention relates to a horizontal subsurface flow wetland system that strengthens denitrification of micro-polluted water bodies in winter, and effectively solves problems such as low BOD ₅ /NO ₃ ^- , dissolved oxygen, matrix clogging, etc. that affect the denitrification effect of winter wetlands. The method is to inject water into the matrix bed The water distribution room is formed between the water distribution plate installed on the inner surface of the end and the inner surface of the water inlet end. The water collection room is formed between the water collecting plate provided on the inner surface of the water outlet end and the inner surface of the water outlet end. The front section of the matrix bed is between the water distribution plate and the water collecting plate. There are multiple sampling tubes in the middle section, and each sampling tube has a vent hole. There is a corncob layer in the rear section of the matrix bed. There are water holes on the water distribution plate and the water collection plate. The water distribution plate and the water collection plate are The matrix bed is filled from top to bottom with a sand and gravel layer, a zeolite layer, and a gravel and iron filing layer. The water inlet end of the matrix bed is equipped with a water inlet pipe, and the water outlet end is equipped with an outlet pipe to adjust the water level. The surface of the wetland system is covered With the membrane, the invention has simple maintenance, low substrate clogging frequency, denitrification rate of not less than 40%, and low operating costs.

Description

Horizontal subsurface flow wetland system to strengthen denitrification of slightly polluted water in winter

technical field

The invention relates to a sewage treatment system, in particular to a horizontal subsurface flow wetland system that strengthens denitrification of slightly polluted water bodies in winter.

Background technique

Pollution of water sources is a common problem in the world, especially my country is one of the countries with serious shortage of water resources in the world. The per capita water resources are small, but the water pollution is very serious. In recent years, due to the continuous strengthening of the construction of sewage treatment plants, the problem of direct sewage discharge has been curbed to a certain extent. However, even if the sewage treatment plants implement the most stringent discharge standards, there is still a certain gap between the effluent indicators and the surface water environmental quality standards. As the receiving water body of various treated wastewater, rivers are often polluted by organic matter and nitrogen and phosphorus, but the pollution is relatively light, and they are called slightly polluted water bodies. Although the pollution of such water bodies is not serious, the quality of the ecological environment of most rivers is poor and cannot meet the functional requirements of the water environment. Especially in the north, due to the lack of natural runoff and serious shortage of water resources in most areas, the pollution-holding capacity of natural water bodies has been reduced. It is very difficult to guarantee and maintain the functional zoning requirements of the surface water environment.

At present, scholars at home and abroad have developed some technical means to purify the slightly polluted water bodies of polluted rivers. (1) The commonly used physical purification methods include river aeration, water diversion dilution and sediment dredging. Such methods require high energy consumption to achieve the expected effects of aeration, dredging, and flushing, and do not remove pollutants fundamentally, treating the symptoms but not the root cause. (2) Chemical purification methods include chemical algae removal, flocculation and sedimentation, and chemical fixation of heavy metals. Such methods also do not remove nitrogen, phosphorus or heavy metals from water bodies, and easily lead to secondary pollution due to the application of chemical reagents. In addition, for the river water with a large flow rate, the amount of dosing is also large, and the economy is poor. (3) The commonly used methods of biological purification include the method of bacteriostasis, biofilm and aeration and oxygenation. In general, biological purification has the advantages of good treatment effect, low investment, low energy consumption, and the ability to restore or enhance the self-purification ability of water bodies. However, it takes a long time for the breeding of high-efficiency microorganisms used in the bacterial injection method, and the purification effect lasts. The time is short, and it is easily restricted by external conditions; the investment of biofilm method and aeration and oxygenation method is relatively large, and it is not suitable for large-scale adoption under the premise of limited funds. (4) Ecological technologies mainly include plant purification technology, land treatment technology, stabilization pond technology and artificial wetland purification technology. Ecological management measures have the advantages of good governance effects, low energy consumption, low operating costs, and simple maintenance, especially the artificial wetland purification method, which also has certain ecological and economic benefits.

Although constructed wetland technology is widely used in the south, its promotion and application in the north is greatly restricted. The main reasons are: (1) the cold climate in the north inhibits the activity of microorganisms, resulting in poor removal effect; (2) plants wither or die in winter, The reoxygenation ability of photosynthesis is weakened, and the dissolved oxygen in the matrix bed is insufficient; (3) the treated wastewater collected by the river has low BOD ₅ /NO ₃ ^- and poor biodegradability, which limits the treatment effect of the constructed wetland; (4) Microbial activity is limited in winter, which accelerates the frequency of substrate bed clogging.

Although it is recognized that BOD ₅ /NO ₃ ^- , dissolved oxygen, and matrix clogging affect the denitrification effect of wetlands in winter, there is no recognized technical solution at home and abroad.

Contents of the invention

In view of the above situation, in order to overcome the defects of the prior art, the purpose of the present invention is to provide a horizontal subsurface flow wetland system that strengthens the denitrification of slightly polluted water in winter, which can effectively solve the problems of low BOD ₅ /NO ₃ ^- , dissolved oxygen, matrix clogging, etc. Problems affecting the denitrification effect of wetlands in winter.

The technical solution solved by the present invention is that the system includes a water distribution plate, a matrix bed body and a water collection plate, and the inner surface of the water inlet end of the matrix bed body along the long direction is provided with a water distribution plate parallel to the end surface of the matrix bed body upwards, and the water distribution plate The water distribution room is formed between the plate and the inner surface of the water inlet end, and the inner surface of the water outlet end of the matrix bed is provided with a water collection plate parallel to the end surface of the matrix bed body, and the water collection room is formed between the water collection plate and the inner surface of the water outlet end. The front section and the middle section of the matrix bed formed between the water plate and the water collection plate are vertically placed with multi-channel ventilation sampling tubes, each sampling tube is provided with air holes, and the rear section of the matrix bed body is vertically placed with a tube parallel to the collection tube. The inner surface of the water board is the corn cob layer as the cellulose carbon source (the front section, middle section, and rear section are defined by the water inlet end as the front and the water outlet end as the back), the structure of the water distribution board and the water collection board are the same, and the water distribution board The water distribution plate and the water collection plate are evenly distributed with water holes, and the matrix bed between the water distribution plate and the water collection plate is filled with sandstone layer, zeolite layer, gravel iron filings layer, sandstone layer and zeolite layer from top to bottom. Between the layers, between the zeolite layer and the gravel iron filings layer, there are geotechnical permeable cloths used to prevent the matrix layer from collapsing or seeping down. The end surface of the water inlet end of the matrix bed is equipped with a water inlet pipe, and the end surface of the water outlet end is arranged from top to bottom. The first water outlet pipe, the second water outlet pipe, and the third water outlet pipe for adjusting the water level. The surface of the wetland system is covered with a film, and the water outlet pipe for adjusting the water level constitutes the heat preservation structure of the water in the bed. Through the water hole on the water distribution plate, The water body evenly flows zigzagging in the matrix bed, fully contacts with the corn cob layer, increases the BOD ₅ /NO ₃ ^- of the water body, and adjusts the water level in the matrix bed through the first water outlet pipe, the second water outlet pipe, and the third water outlet pipe. Combining the water level adjustment with the film covering the surface of the matrix bed body ensures the water temperature in the matrix bed body, and then strengthens the denitrification effect of the horizontal subsurface flow wetland system in winter. The reoxygenation capacity of the front end of the body is higher than that of the back end, so that the oxygen-enriched water is mainly concentrated in the front end of the matrix bed, creating conditions for the aerobic nitrification at the front end of the matrix bed and anaerobic denitrification at the end, which is beneficial to the nitrogen removal effect of the wetland and benefits Nitrification at the front end of the matrix bed and denitrification at the end.

The present invention provides a horizontal subsurface flow wetland system with reasonable structure design, appropriate reoxygenation measures and heat preservation measures in view of the limited promotion of wetlands in the north. The matrix configuration and distribution of the system can significantly improve the denitrification of the horizontal subsurface flow wetland system in winter capacity, and simple maintenance, low frequency of matrix clogging, can strengthen the denitrification capacity of the wetland bed in winter, the denitrification rate is not less than 40%, and simple maintenance, low operating costs, effectively solve the problem of water pollution, huge economic and social benefits.

Description of drawings

Fig. 1 is the front view of the sectional structure of the present invention.

Fig. 2 is a structural front view of the water distribution plate (or water collection plate) of the present invention.

Fig. 3 is a sectional front view of the substrate bed bottom structure of the present invention.

Detailed ways

The specific implementation manners of the present invention will be described in detail below in conjunction with the accompanying drawings.

As shown in Figure 1, the present invention includes a water distribution plate, a matrix bed body and a water collection plate, and the inner surface of the water inlet end of the matrix bed body along the long direction is provided with a water distribution plate 3 parallel to the end surface of the matrix bed body upwards, and the water distribution plate The water distribution room 13 is formed between the inner surface of the water inlet end, and the inner surface of the water outlet end of the matrix bed along the length is provided with a water collection plate 11 parallel to the end surface of the matrix bed body, and a water collection room 14 is formed between the water collection plate and the inner surface of the water outlet end. , the front section and the middle section of the matrix bed formed between the water distribution plate and the water collection plate are placed vertically upwards with multi-channel ventilation sampling tubes 4, each sampling tube is provided with air holes 5, and the rear section of the matrix bed body is placed vertically upwards There is a corn cob layer 9 parallel to the inner surface of the water collecting plate as the cellulose carbon source (the front section, middle section, and rear section are defined by the water inlet end as the front and the water outlet end as the rear), the water distribution plate and the water collection plate The structure is the same, the water distribution plate and the water collection plate are evenly distributed with water holes 3-1, and the matrix bed between the water distribution plate and the water collection plate is filled with sandstone layer 6, zeolite layer 7, The gravel iron filings layer 8, between the sandstone layer 6 and the zeolite layer 7, and between the zeolite layer 7 and the gravel iron filings layer 8 are provided with a geotechnical permeable cloth 10 for preventing the matrix layer from collapsing or infiltrating, and the matrix bed is infiltrated with water. The water inlet pipe 2 is installed on the end surface of the water end, and the first water outlet pipe 12-1, the second water outlet pipe 12-2, and the third water outlet pipe 12-3 for adjusting the water level are arranged on the end surface of the water outlet end from top to bottom. The surface of the wetland system is covered with The film and the water outlet pipe for adjusting the water level constitute the heat preservation structure of the water in the bed body. Through the water holes on the water distribution plate, the water body evenly flows in the matrix bed body in a zigzag way, fully contacts with the corn cob layer 9, and increases the BOD ₅ of the water body /NO ₃ ^- , through the first water outlet pipe 12-1, the second water outlet pipe 12-2, and the third water outlet pipe 12-3 to adjust the water level in the matrix bed, and combine the water level adjustment with the film covering the matrix bed surface, Ensure the water temperature in the matrix bed, and then strengthen the denitrification effect of the horizontal submerged wetland system in winter. The layout density of the sampling pipes decreases from the water inlet to the water outlet. It is mainly concentrated at the front end of the matrix bed, creating conditions for aerobic nitrification at the front end of the matrix bed and anaerobic denitrification at the end, which is beneficial to the removal of nitrogen by wetlands, and is beneficial to the nitrification at the front end of the matrix bed and denitrification at the end .

The matrix bed body is composed of a rectangular peripheral wall 1-1 made of bricks and a bottom surface 1-2 at the bottom of the peripheral wall body. The matrix bed body has an aspect ratio of 2:1, a height of 1.2 meters, and a bottom surface of Composite consisting of tamped 20cm-thick plain soil layer 1-2-3, 1.5mm-thick high-density polyethylene anti-seepage cloth layer 1-2-2 and rammed 10cm-thick clay layer 1-2-1 from bottom to top structure.

The sampling tube 4 is a circular hollow tube with a diameter of 1.5 cm made of PVC, and the hollow tube has a ventilation hole 5 of 0.3 cm at intervals of 8.0 cm.

The corncob layer 9 has a corncob particle size of 0.5-3 cm, is placed vertically in the middle and back of the matrix bed, has a thickness of 1.0-3.0 cm, a height of 80 cm, and the same width as the matrix bed.

The thickness of the sandstone layer is 20cm, the thickness of the zeolite layer is 40cm, the thickness of the gravel iron filings layer is 30cm, the particle size of the sandstone is 0.5~1.0cm, the particle size of the zeolite is 1.0~2.0cm, the particle size of the gravel is 2.0~4.0cm, iron The chip particle size is 0.5~1.0cm, and the volume ratio of iron filings and gravel is 1︰8~10.

The geotechnical permeable fabric is a polyester cloth with a thickness of 1.5mm; the film is a TPU waterproof and breathable membrane with a thickness of 0.2mm.

The tops of the water distribution plate 3 and the water collection plate 11 are lower than the upper edge of the matrix bed at both ends of the lengthwise direction, the upper top of the sampling pipe 4 is higher than the upper edge of the matrix bed, and the vent hole at the top of the sampling pipe must be Lower than the upper plane of the gravel layer 6, the top of the corn cob layer 9 will be higher than the upper plane of the gravel layer 6 to ensure the use effect.

The surface of the sandstone layer can be covered with sandy soil, and plants such as reeds, cattails or yellow iris are planted.

It can be seen from the above that the present invention consists of water distribution board, substrate bed, water collection board, reoxygenation structure and heat preservation structure to form a horizontal subsurface flow wetland system that strengthens the denitrification of slightly polluted water in winter.

The reoxygenation structure (measure) is a combination of ventilation sampling tube and water level adjustment, the vertical density of the ventilation sampling tube is placed from large to small, and the water level is adjusted according to the concentration of dissolved oxygen in the water in the matrix bed;

The heat preservation structure (measure) is a combination of covering film and water level adjustment. The film is a TPU breathable film with a thickness of 0.2 mm, and the water level is adjusted according to the water temperature in the matrix bed.

The ventilation sampling tube is made of PVC, which is resistant to acid, alkali and corrosion. The ventilation sampling tubes are irregularly arranged, and the arrangement density is from large to small along the longitudinal direction of the matrix bed. The reoxygenation capacity of the front end of the matrix bed is higher than that of the rear end, so that the oxygen-enriched water is mainly concentrated at the front end of the matrix bed, which is aerobic for the front end of the matrix bed. Nitrification and terminal anaerobic denitrification create suitable conditions, which are beneficial to the nitrogen removal effect of wetlands.

The cellulose carbon source is corn cob, which has the advantages of wide source, low price, strong carbon supply capacity, and not easy to block the matrix bed. The corn cob is placed vertically in the middle and back of the matrix bed, and the water body fully contacts with the corn cob during the horizontal tortuous flow process, and the release of the corn cob extract improves the biodegradability of the wastewater (BOD ₅ /NO ₃ ^- ), which is denitrification The effect creates favorable conditions, and then promotes the removal effect of wetland on nitrogen.

Apply iron filings and other industrial wastes to the construction of horizontal subsurface flow wetlands, and comprehensively use electrochemical principles (internal electrolysis technology composed of iron filings/carbon) to improve the biodegradability of micro-polluted water bodies. Under the joint action of microorganisms, plants, and substrates , to achieve enhanced purification of slightly polluted water.

And through actual tests, very satisfactory beneficial technical effects have been obtained, and its technical advantages mainly lie in:

The irregular and reasonable layout of the ventilation and sampling pipes, while achieving the decontamination effect, avoids the power consumption of the aeration system and saves operating costs. The cost of water treatment per ton is not higher than 0.05 yuan, while the cost of conventional sewage treatment is not less than 0.4 yuan / ton, the sewage treatment cost is only 1/8 of the original treatment cost, and the economic effect is very huge;

^Industrial waste, agricultural waste and other materials are used in wetland construction, which not only provides a place for waste disposal, but also improves the biodegradability of wastewater. The BOD ₅ /NO ₃ of slightly polluted water can be increased from about 1.0 at the beginning to 2.0 or above, thereby promoting the decontamination effect of the wetland;

The organic combination of different heat preservation measures such as film covering, water level adjustment (precipitation level using geothermal heat preservation) and reoxygenation measures solves the contradiction between heat preservation (blocking the gas exchange between the matrix bed and the outside world) and reoxygenation, and the water temperature in the wetland bed can be adjusted. Keep the temperature above 10°C and the concentration of dissolved oxygen not lower than 2mg/L to ensure that the nitrogen removal rate of the wetland system in winter is not lower than 40%. Under normal circumstances, the removal rate of TN in horizontal subsurface flow wetlands is only maintained at about 20%. The denitrification rate of the invention is much higher than that of the prior art, and has been fully proved by practical application.

example 1

For example, a estuary wetland project in Liaoning adopts the technology described in the present invention to treat domestic sewage and some industrial wastewater around the wetland. The project consists of a sewage pretreatment area, a horizontal subsurface flow wetland treatment area (main process), and a surface flow wetland landscape area. Three kinds of substrates are laid in the subsurface wetland, the planting layer is 0.3m, the small-size gravel layer is 0.5m, and the large-size gravel layer is 0.4m. The water distribution of the horizontal submerged wetland adopts PVC pipes for multi-point water intake, with three water levels of high, medium and low, and the water volume is adjusted by opening the three water level valves. In order to ensure the normal operation of the wetland system in winter, the on-site personnel covered the wetland system with plastic film, straw curtains and other materials to keep the wetland system warm. The water temperature in the wetland system can be maintained at 10-15°C, and the effluent meets the "Pollutant Discharge Standards for Urban Sewage Treatment Plants" ( GB18918-2002) A standard of the first class standard.

Example 2:

For another example, a river beach wetland project in Shanxi adopts the technology described in the present invention to treat upstream river water, surrounding industrial wastewater and domestic sewage. The main treatment process of the wetland is "pretreatment sedimentation tank + surface flow wetland + vertical flow wetland". The wetland bed is paved with 1.5m thick gravel fill of different specifications, which is divided into five layers. From top to bottom, the gravel particle size ranges from small to large (3mm~100mm), and the water quality is purified through the absorption of microorganisms in the matrix layer. The surface layer is covered with sandy soil, on which plants such as reeds, cattails, and yellow iris are planted. Air ducts are evenly distributed in the vertical flow wetland. The total length of a single air duct is 1.8m, and the air holes (aperture diameter is about 5mm) are evenly opened on the pipe wall at intervals of 30cm. After reeds and other plants are harvested in winter, plant stalks and breathable films are covered on the surface of the subsurface wetland. Due to the small amount of water treated in winter and the long hydraulic retention time, the treatment efficiency of COD and ammonia nitrogen in winter wetlands is not much different from that in other seasons, and the wetland effluent is mainly polluted The concentration of pollutants meets the water quality standard of Class IV of surface water.

It can be clearly seen from the above data that the present invention can strengthen the denitrification capacity of the wetland bed in winter, the denitrification rate is not lower than 40%, and the maintenance is simple, the operation cost is low, and it has strong practicability. It is a major innovation with huge economic and social benefits.

Claims (9)

1. strengthen the horizontal subsurface flow wetland system of micropollutant water denitrogenation in winter for one kind, comprise water distribution board, matrix bed body and water collecting plate, it is characterized in that, matrix bed body along long to feed-water end inner face be provided with the water distribution board (3) being upwards parallel to matrix bed body end face, form between water distribution board and feed-water end inner face (13) between water distribution, matrix bed body along long to water side inner face be provided with the water collecting plate (11) being upwards parallel to matrix bed body end face, form between water collecting plate and water side inner face and receive (14) between water, leading portion in the matrix bed body formed between water distribution board and water collecting plate and stage casing are placed with the stopple coupon (4) of multiple tracks ventilation vertically upward, each stopple coupon has ventilating pit (5), in matrix bed body, back segment is placed with vertically upward and is parallel to the corn sandwich layer (9) of water collecting plate inner face as Mierocrystalline cellulose carbon source, water distribution board is identical with water collecting plate structure, water distribution board and water collecting plate are evenly equipped with limbers (3-1), sand stone layer (6) is filled with from top to bottom successively in matrix bed body between water distribution board and water collecting plate, zeolite layer (7), gravel iron filings layer (8), between sand stone layer (6) and zeolite layer (7), be provided with between zeolite layer (7) and gravel iron filings layer (8) for prevent hypothallus from caving in or under the permeable cloth of geotechnique (10) that oozes, the end face of matrix bed body feed-water end is equipped with water inlet pipe (2), the end face of water side is provided with the first rising pipe (12-1) for regulating water level from top to bottom, second rising pipe (12-2), 3rd rising pipe (12-3), wet land system surface coverage has film, with the insulation construction regulating the rising pipe of water level to form water in bed body, by the limbers on water distribution board, water body is Tortuous flow in matrix bed body uniformly, fully contact with corn sandwich layer (9), improve the BOD of water body ₅/ NO ₃ ^-, by the first rising pipe (12-1), second rising pipe (12-2), 3rd rising pipe (12-3) regulates the water level in matrix bed body, regulation of level is combined with the coating film measure of matrix bed surface, ensure the water temperature in matrix bed body, and then strengthen the denitrification effect in winter of horizontal subsurface flow wetland system, the layout density of stopple coupon is reduced to water side successively by feed-water end, matrix bed body front end reoxygenation ability is higher than rear end, oxygen enrichment water body is made mainly to concentrate on matrix bed body front end, for the aerobic nitrification effect of matrix bed body front end and the effect of end anaerobic denitrifying create conditions, favourable wetland is to the removal effect of nitrogen, benefit the carrying out of matrix bed body front end nitrification and end denitrification.

2. the horizontal subsurface flow wetland system of strengthening micropollutant water denitrogenation in winter according to claim 1, it is characterized in that, described matrix bed body be by the brick rectangular periphery body of wall (1-1) that builds up and periphery body of wall bottom bottom surface (1-2) form, matrix bed body long-width ratio is 2 ︰ 1, high 1.2 meters, bottom surface is the composite structure be made up of the thick high density polyethylene(HDPE) antiseepage layer of cloth (1-2-2) of the thick plain soil layer (1-2-3) of bottom-up compacting 20cm, 1.5mm and the thick clay seam (1-2-1) of compacting 10cm.

3. the horizontal subsurface flow wetland system of strengthening micropollutant water denitrogenation in winter according to claim 1, it is characterized in that, described stopple coupon (4) is the circular hollow tube of the diameter 1.5cm be made up of PVC, open tube has the ventilating pit (5) of 0.3cm at interval of 0.8cm.

4. the horizontal subsurface flow wetland system of strengthening micropollutant water denitrogenation in winter according to claim 1, it is characterized in that, described corn sandwich layer (9), the particle diameter of corn cob is 0.5-3cm, vertically place in matrix bed body posterior segment, laying depth 1.0 ~ 3.0cm, height 80cm, width is identical with the width of matrix bed body.

5. the horizontal subsurface flow wetland system of strengthening micropollutant water denitrogenation in winter according to claim 1, it is characterized in that, described sand stone layer thickness is 20cm, zeolite layer thickness is 40cm, gravel iron filings layer thickness is 30cm, gravel size 0.5 ~ 1.0cm, sized zeolite particles 1.0 ~ 2.0cm, grain size of gravel 2.0 ~ 4.0cm, iron filings particle diameter 0.5 ~ 1.0cm, volume ratio 1 ︰ 8 ~ 10 of iron filings and gravel.

6. the horizontal subsurface flow wetland system of strengthening micropollutant water denitrogenation in winter according to claim 1, it is characterized in that, the permeable cloth of described geotechnique is the woven dacron of thickness 1.5mm.

7. the horizontal subsurface flow wetland system of strengthening micropollutant water denitrogenation in winter according to claim 1, it is characterized in that, described film is the TPU waterproof ventilated membrane of thickness 0.2mm.

8. the horizontal subsurface flow wetland system of strengthening micropollutant water denitrogenation in winter according to claim 1, it is characterized in that, described water distribution board (3), the top of water collecting plate (11) are lower than the long upper edge to the matrix bed body at two ends, the upper top of stopple coupon (4) is higher than the upper edge of matrix bed body, the ventilating pit of stopple coupon topmost will lower than the upper plane of sand stone layer (6), and the top of corn sandwich layer (9) is higher than the upper plane of sand stone layer (6).

9. the horizontal subsurface flow wetland system of strengthening micropollutant water denitrogenation in winter according to claim 1, it is characterized in that, described sand stone layer surface coverage has sand, and kind is implanted with reed, cattail or wilson iris plant.