CN103739081B - A kind of current wetland device for low-pollution water strengthened denitrification - Google Patents

Abstract

The invention relates to an enhanced denitrification subsurface flow artificial wetland device in the technical field of environmental engineering, including: a pretreatment sedimentation tank, a drop aeration well and a wetland tank, and the wetland tank is divided into an aerobic nitrification section, an inspection well, Anoxic denitrification section and water collection well. Pre-treat sedimentation ponds to settle suspended solids to prevent subsequent structures from clogging; drop water steps are set in the drop water aeration well to increase the concentration of dissolved oxygen; Plant vascular plants to increase the concentration of dissolved oxygen in the filler layer, thereby ensuring the smooth occurrence of nitrification; the inspection well is connected with a secondary water inlet pipe to supplement the carbon source required for denitrification; the anoxic denitrification section is filled with efficient phosphorus removal substrates, Denitrification and adsorptive removal of phosphorus pollutants; catchment wells collect treated water and eventually exit the plant. Compared with the prior art, the invention has a better treatment effect on nitrogen in sewage, and the removal rates of total nitrogen and ammonia nitrogen can reach more than 80%.

Description

A subsurface wetland device for enhanced denitrification of low-polluted water

technical field

The invention relates to a device in the technical field of environmental engineering, in particular to a subsurface flow artificial wetland device with enhanced denitrification function. It can be used for enhanced denitrification of low-pollution water such as tail water from urban sewage plants and farmland irrigation backwater.

Background technique

Low-pollution water, including tailwater from urban sewage plants, backwater from farmland irrigation, etc. Because its water quality is between the sewage treatment plant discharge standard and the surface water V standard, once it is discharged into the receiving water body, it will greatly increase the organic matter and nutrient load in the water body, so it is currently regarded as the main external cause of eutrophication in the water body one of the sources.

At present, for the treatment of low-pollution water, countries all over the world adopt ecological engineering methods, including artificial wetlands and ecological gravel beds. Engineering practice at home and abroad shows that the existing ecological engineering technology has a good treatment effect on organic pollutants (BOD) and suspended solids (SS) in low-pollution water, but the removal effect on nitrogen pollutants is not ideal. The landscape water purification artificial wetlands constructed in Chengdu, Shanghai and other places in my country show that after the low-pollution water is purified by artificial wetlands, the removal rate of total nitrogen is generally lower than 60%, and the content of ammonia nitrogen is even greater than that of the incoming water, causing stench and seriously affecting the landscape water body. viewing function.

Studies have shown that the removal of nitrogen in low-pollution water by constructed wetlands mainly depends on the nitrification and denitrification of microorganisms. The fundamental reason for the poor denitrification effect of low-polluted water in constructed wetlands is that these two effects are inhibited. The specific reasons include (1) the dissolved oxygen content in the constructed wetland is very low, which inhibits the nitrification of ammonia nitrogen, causing the ammonia nitrogen in the effluent to be higher than that in the influent; has been degraded, and the growth and decay of constructed wetland plants release very little carbon source. These reasons lead to insufficient carbon source for denitrification. Solving the above problems is the technical key to strengthening the denitrification function of constructed wetlands.

Retrieve the prior art. Chinese patent announcement number CN102642927A discloses an automatic oxygen supply type artificial wetland device. By filling a part of hollow bricks in the artificial wetland matrix, and adopting the intermittent operation mode of water inflow for 6 days and drain for 1 day, the underflow The content of dissolved oxygen in the constructed wetland is greatly increased, which in turn promotes the degradation of organic matter and the nitrification of ammonia nitrogen. However, filling the hollow bricks reduces the matrix content in the wetland and reduces the effective purification volume inside the wetland; in addition, the intermittent operation of the device is impossible in some cases (such as in-situ purification of river water). These shortcomings limit the use and promotion of this technology.

Contents of the invention

The object of the present invention is to provide a subsurface flow wetland device for enhanced denitrification of low-pollution water in order to overcome the above-mentioned defects in the prior art.

The purpose of the present invention can be achieved through the following technical solutions: a subsurface flow wetland device for enhanced denitrification of low-pollution water, characterized in that it includes: a pretreatment sedimentation tank, a drop water oxygenation well and a wetland tank, the wetland tank is in accordance with The direction of water flow is divided into aerobic nitrification section, inspection well, anoxic denitrification section and water collection well. There is a secondary water inlet pipe in the inspection well; the raw water overflows after being settled in the pretreatment sedimentation pond and falls into the falling water for oxygenation Well, after oxygenation, the water flows into the wetland tank, and the nitrification is completed in the aerobic nitrification section; after passing through the inspection well and mixing with the secondary water flowing out of the secondary water inlet pipe, it enters the anoxic denitrification section to complete the denitrification, Eventually enters the sump and exits the unit.

The pretreatment sedimentation pond is rectangular or square, with an aspect ratio of 3:1 to 1:1; it is mainly used for settling suspended particulate matter in the water body to prevent it from blocking subsequent subsurface flow wetland tanks. The pretreatment sedimentation pond enters water through the water inlet pipe, and the effluent (supernatant) after sedimentation falls through the horizontal weir and enters the falling water oxygenation well. The falling water oxygenation well is rectangular, built together with the pretreatment sedimentation pond, so the width is the same, and the length along the water flow direction is 100-200cm; the wetland tank is rectangular, and the aspect ratio is 10:1 to 3 : 1, its depth is 50-80cm.

The bottoms of the pretreatment sedimentation tanks, falling water oxygenation wells and wetland tanks are treated with rolled clay or composite soil for anti-seepage treatment, the pool bodies are built with rubble, and the walls are treated with cement mortar for anti-seepage treatment.

The upstream side wall of the pretreatment sedimentation pond is provided with a water inlet pipe, and the top surface of the downstream side wall is provided with a horizontal weir, and the water to be treated is input into the pretreatment sedimentation pond through the water inlet pipe, and the supernatant after precipitation overflows through the horizontal weir. out of water.

The upstream side wall of the falling water oxygenation well is shared with the pretreatment sedimentation pond, the top of the side wall is provided with a horizontal weir, and the horizontal weir is connected with 3 to 5 steps of falling water, each step is 10-20cm high; The water level difference between the pretreatment sedimentation pond and the falling water oxygenation well is 30-50cm. The drop water oxygenation well is kept level with the water surface of the wetland tank, and the water depth is the same as that of the wetland tank. After the effluent of the pretreatment sedimentation pond overflows, the content of dissolved oxygen in the water is increased by dropping water, a natural oxygen-enriching method that does not require any power energy consumption.

Both the aerobic nitrification section and the anoxic denitrification section of the wetland tank are filled with active substrate fillers with a thickness of 40-70 cm, and a soil layer with a thickness of 10 cm is covered on the top of the filler layer.

The filler layer and the soil layer are separated by a net, and the material of the net is a material with a certain strength and corrosion resistance, including a nylon net with a pore size of 0.2-0.8cm; the nylon net can prevent soil particles from entering the active matrix to cause Wetland plugging, on the other hand, can also allow the roots of plants to penetrate the substrate layer.

The active matrix filler filled in the aerobic nitrification section is ammonia nitrogen adsorption material, including natural zeolite and vermiculite; the active matrix filler filled in the anoxic denitrification section is phosphorus adsorption material, including calcite, manganese sand or activated alumina. The organic matter (including organic nitrogen) in the sewage is aerobically decomposed in this section, and the ammonia nitrogen produced by the decomposition and the ammonia nitrogen in the raw water are first adsorbed by the ammonia nitrogen adsorption material (such as zeolite, etc.) to form a high concentration area of ammonia nitrogen, and then pass through the microorganism Nitrification converts it to nitrate nitrogen. Microbial nitrification generally takes a long time and requires a long hydraulic retention time, while the adsorption material can "retain" ammonia nitrogen in the aerobic nitrification section, effectively shortening the residence time and the occupied area of the treatment structure.

The ratio of the length of the aerobic nitrification section to the length of the anoxic denitrification section in the wetland tank is 15-40:60-85.

Perforated aeration tubes are vertically inserted in the aerobic nitrification section of the wetland tank, with a density of 4-8 roots/m ² ; vascular plants with strong rooting ability and oxygenation function are planted in the soil layer, with a density of 1-8 3 plants/m ² . Make the oxygen in the atmosphere enter the soil and the filler layer, supplement the oxygen consumed by the degradation of organic matter and ammonification, and ensure the smooth progress of the nitrification reaction. In addition, vascular plants, such as reeds, are planted in the aerobic nitrification section (planting density 1-4 plants/m ² ). On the one hand, vascular plants have a strong rooting ability and can penetrate deep into the matrix layer. On the other hand, vascular plants can transport oxygen to the plant roots through vascular bundles, like an "oxygenation pump", replenishing the matrix layer. Oxygen further ensures an aerobic environment in the stroma layer. The above two enhanced oxygenation methods are in line with the principles of ecological engineering, without any power and energy consumption.

The aerobic nitrification section in the wetland tank enters the inspection well through the overflow of the horizontal weir; the side of the inspection well is connected to the secondary water inlet pipe, which is used to supplement the needs of the upcoming denitrification in the anoxic denitrification section. carbon source. The secondary water intake should be determined according to the raw water quality and the nitrification and organic matter degradation in the aerobic nitrification section. Generally, it is 0.1 to 1 times the water intake at the beginning of the device. After determining the secondary water intake, the secondary water intake can be calculated according to the water volume. diameter; the effluent from the anoxic denitrification section overflows through the horizontal weir and enters the water collection well; the water collection well finally discharges the treated water out of the device through pipelines.

The surface of the anoxic denitrification section is planted with plants without oxygenation (such as turf, etc.) and does not have any enhanced aeration facilities. Therefore, except near the microenvironment of the rhizosphere of the plants, the whole is in an anoxic state. The anoxic condition and the carbon source supplemented by the secondary influent ensure the effect of denitrification in this stage.

The present invention aims at the problems of insufficient dissolved oxygen for nitrification and insufficient carbon source for denitrification existing in existing constructed wetlands (including matrix-enhanced constructed wetlands), divides subsurface flow constructed wetlands into two purification sections according to the degradation process of nitrogen, and strengthens the configuration Dissolved oxygen and carbon source conditions required by each purification stage, so as to greatly improve the removal performance of nitrogen pollutants in sewage on the basis of taking into account the removal effects of organic matter, suspended matter and phosphorus.

The specific measures of the present invention include: (1) dividing the subsurface wetland into an aerobic nitrification section and an anoxic denitrification section; (2) adopting hydraulic oxygenation, enhanced atmospheric oxygenation, plant oxygenation, etc. Increase the amount of dissolved oxygen without power energy, and configure the dissolved oxygen conditions required for nitrification; (3) Set up secondary water intake before the anoxic denitrification section, and use organic substances in raw water to supplement the carbon source required for denitrification; (4) Fill the active matrix with ammonia nitrogen adsorption function in the aerobic nitrification section to promote nitrification; fill the active matrix with phosphorus adsorption performance in the anoxic denitrification section to ensure effective phosphorus removal under the background of strengthening denitrification of the whole device remove.

Compared with the prior art, the present invention rationally divides the subsurface constructed wetland into an aerobic nitrification section and an anoxic denitrification section according to the degradation process of nitrogen pollutants. The distinction between nitrification and denitrification, two nitrogen degradation processes with very different nutrient and dissolved oxygen requirements, provides a prerequisite for strengthening the conditions required for each reaction. On this basis, through various ecological engineering methods without power consumption such as hydrodynamic oxygenation (falling water aeration), enhanced atmospheric oxygenation (insertion of perforated aeration tubes), plant oxygenation (planting vascular plants), etc., to ensure good The higher dissolved oxygen level in the oxynitrification section; through the secondary water intake, the sufficient carbon source for denitrification in the anoxic denitrification section is ensured, thereby ensuring the smooth progress of nitrification and denitrification. In addition, the filling of active substrate in the aerobic nitrification section shortens the residence time of the nitrification section, while the filling of phosphorus adsorption materials in the anoxic denitrification section realizes the removal of phosphorus pollutants in wetlands. In general, on the basis of ensuring the removal of suspended solids, organic matter, phosphorus and other pollutants, the present invention effectively solves the problem of improving the denitrification efficiency when ordinary constructed wetlands treat low-pollution water, and prevents excessive ammonia nitrogen in the effluent and irritating odors. nasal problems.

Description of drawings

Fig. 1 is a schematic diagram of the structure of the present invention.

Detailed ways

The embodiments of the present invention will be described in detail below. This embodiment is carried out on the premise of the technical solution of the present invention, and a detailed implementation mode and specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

This example is located in Shangguan Town, Dali Bai Autonomous Prefecture, Yunnan Province. The influent water is the tail water of a village sewage purification device. The total water volume introduced into the device is 55m ³ /d (including secondary water inflow). "Quality Standard" (GB3838-2002) identified as inferior V water, the main pollution indicators are total nitrogen 10mg/L, ammonia nitrogen 4mg/L, total phosphorus 0.8mg/L, COD 40mg/L.

As shown in Figure 1, the present embodiment includes along the water flow direction: a pretreatment sedimentation pond 101, a drop water oxygenation well 102, and a wetland tank. Denitrification section 105 and water collection well 106. The pretreatment sedimentation pond 101 is fed with 42m ³ /d of water through the water inlet pipe 1, and the outlet water overflows through the horizontal weir 2 and enters the falling water oxygenation well 102, and the water level difference between the two is 50cm. The falling water oxygenation well 102 is connected with the aerobic nitrification section 103 of the wetland tank through the orifice 4 at the bottom of the partition wall between the two. After the influent water is treated in the aerobic nitrification section 103 ^of the wetland tank, it overflows through the horizontal weir 10 and enters the inspection well 104. The orifice 12 at the bottom of the partition wall of the oxygen denitrification section 105 enters the anoxic denitrification section 105 for treatment. After the treatment is completed, the water overflows through the horizontal weir 16 and enters the water collection well 106, and is finally discharged from the device through the water outlet pipe 17.

The pretreatment sedimentation pond 101, the falling water oxygenation well 102, the aerobic nitrification section 103 of the wetland tank, the inspection well 104, the anoxic denitrification section 105 of the wetland tank and the water collection well 106 are all built together, with a width of 5m and a depth of Both are 80cm, and the lengths are 5m, 2.5m, 15m, 0.5m, 22m, and 0.5m. The bottom elevation of the pretreatment sedimentation pond 101 is 50 cm higher than the bottom elevation of the subsequent treatment structures 102-106.

The pretreatment sedimentation pond 101, the falling water oxygenation well 102, the aerobic nitrification section 103 of the wetland tank, the inspection well 104, the anoxic denitrification section 105 of the wetland tank and the water collection well 106 are all built with rubble, and the outer layer is smeared Cement mortar is used for anti-seepage, and the bottom is treated with rolled clay for anti-seepage.

The effluent from the pretreatment sedimentation pond 101 overflows through the horizontal weir 2 and enters the falling water oxygenation well 102 . The horizontal weir width is 160cm.

In the falling water oxygenation well 102, utilize the drop of 50cm between it and the pretreatment sedimentation tank 101 water surface, set 3 steps 3 to carry out the falling water oxygenation, each step is 15cm high and 10cm wide.

The water inflow to the aerobic nitrification section 103 of the wetland tank enters from the drop water oxygenation well 102 and the water inlet port 4 at the bottom of the partition wall of the wetland tank aerobic nitrification section 103 . There are 12 orifices with a width of 10 cm and a height of 10 cm, which are 10 cm away from the bottom of the drop water oxygenation well 102 .

The aerobic nitrification section 103 of the wetland tank is divided into an active matrix layer 7 and a soil layer 8. The active matrix layer 7 is 70cm thick, and the upper part is covered with a soil layer 8 with a thickness of 10cm. Between the two, nylon with an aperture of 0.2cm is used. The nets are separated to prevent soil particles from falling into the matrix layer 7 and causing blockage. Plant vascular plants 6 with well-developed root systems at a density of 1.5 plants/m ² , and the roots of the plants 6 extend downward through the nylon mesh to reach the active matrix layer 7 . Insert the perforated aeration tube 5 vertically at a density of 2/m ² , the diameter of the aeration tube is 2 cm, the perforation diameter on the tube is 0.2 cm, the bottom of the tube reaches the bottom of the tank, and the top is 20 cm above the ground.

The active substrate in the aerobic nitrification section 103 bed of the wetland tank is natural zeolite, and the planted plants are reeds.

The effluent from the aerobic nitrification-phosphorus removal section 103 of the wetland tank overflows through the horizontal weir 10 and is discharged into the inspection well. The width of the horizontal weir is 160cm.

On the side of the inspection well, a secondary water inlet pipe is set at a place 70cm away from the bottom of the tank.

The water inflow and outflow modes and substrate-soil layer structure of the anoxic denitrification section 105 of the wetland tank are similar to those of the aerobic nitrification section 103 of the wetland tank. However, the active matrix 14 filled in the anoxic denitrification-phosphorus removal section of the wetland tank is calcite, a phosphorus adsorption material, and plant turf without oxygenation function.

The water collection well 106 collects the water from the anoxic denitrification section 105 of the wetland tank, and discharges it out of the system through the water outlet pipe 17 .

Long-term monitoring shows that the low-pollution water treated by the device can remove 82% of total nitrogen, 91% of ammonia nitrogen, 90% of total phosphorus, and 65% of COD, which are stable in << Class III water standard defined in the Environmental Quality Standard for Surface Water.

Claims (6)

1. A subsurface flow wetland device for enhanced denitrification of low-polluted water, characterized in that it comprises: a pretreatment sedimentation tank, a drop water oxygenation well and a wetland tank, and the wetland tank is divided into aerobic nitrification section, In the inspection well, the anoxic denitrification section and the water collection well, there are secondary water inlet pipes in the inspection well; the raw water overflows after being settled in the pretreatment sedimentation pond and falls into the drop water oxygenation well, and the oxygenated water flows into the wetland tank , the nitrification is completed in the aerobic nitrification section; after the inspection well is mixed with the secondary water flowing out of the secondary water inlet pipe, it enters the anoxic denitrification section to complete the denitrification, and finally enters the water collection well and discharges the device; The upstream side wall of the falling water oxygenation well is shared with the pretreatment sedimentation pond, the top of the side wall is provided with a horizontal weir, and the horizontal weir is connected with 3 to 5 steps of falling water, each step is 10-20cm high; The water level difference between the pretreatment sedimentation pond and the falling water oxygenation well is 30-50cm; The aerobic nitrification section and the anoxic denitrification section of the wetland tank are filled with active matrix fillers with a thickness of 40-70 cm, and a soil layer with a thickness of 10 cm is covered on the top of the filler layer; The filler layer and the soil layer are separated by a net, and the material of the net is a material with a certain strength and corrosion resistance, including nylon net, and the aperture is 0.2-0.8cm; the active matrix filler filled in the aerobic nitrification section is Ammonia nitrogen adsorption materials, including natural zeolite and vermiculite; the active matrix filler filled in the anoxic denitrification section is phosphorus adsorption materials, including calcite, manganese sand or activated alumina; Perforated aeration tubes are vertically inserted in the aerobic nitrification section of the wetland tank, with a density of 4-8 roots/m ² ; vascular plants with strong rooting ability and oxygenation function are planted in the soil layer, with a density of 1-8 3 plants/m ² . 2. A subsurface flow wetland device for enhanced denitrification of low-polluted water according to claim 1, characterized in that the pretreatment sedimentation pond is rectangular or square, with an aspect ratio of 3:1 to 1: 1. The falling water oxygenation well is rectangular, with a length of 100-200cm along the direction of water flow; the wetland tank is rectangular, with an aspect ratio of 10:1 to 3:1, and a depth of 50-80cm. 3. A kind of subsurface flow wetland device for strengthening denitrification of low-pollution water according to claim 1, characterized in that, the bottoms of the pretreatment sedimentation tank, the falling water oxygenation well and the wetland tank are used to roll clay Or composite soil for anti-seepage treatment, the pool body is built with rubble, and cement mortar is used for wall anti-seepage treatment. 4. A subsurface flow wetland device for enhanced denitrification of low-polluted water according to claim 1, characterized in that, the upstream side wall of the pretreatment sedimentation pond is provided with a water inlet pipe, and the top surface of the downstream side wall is provided with a water inlet pipe. There is a horizontal weir, and the water to be treated is input into the pretreatment sedimentation pond through the water inlet pipe, and the supernatant after sedimentation overflows the water through the horizontal weir. 5. A subsurface flow wetland device for enhanced denitrification of low-polluted water according to claim 1, characterized in that the length ratio of the aerobic nitrification section to the anoxic denitrification section in the wetland tank is 15~40: 60~85. 6. A subsurface flow wetland device for enhanced denitrification of low-polluted water according to claim 1, characterized in that, the aerobic nitrification section in the wetland tank overflows into the inspection well through a horizontal weir; The side of the inspection well is connected to the secondary water inlet pipe, and the secondary water inlet is 0.1 to 1 times the water inlet at the beginning of the device; the outlet water of the anoxic denitrification section overflows into the water collection well through the horizontal weir; the water collection well passes through The pipes will eventually take the treated water out of the unit.