Open type sewage purification circulating device

Abstract

The utility model relates to an open type sewage purification circulating device. The device comprises a sewage purification body (5) which is a container, the open type sewage purification circulating device comprises a plant purification layer (1), a water inlet pipe (8), a water outlet pipe (2), a circulating water tank A (3), a U-shaped groove (4), a circulating water tank B (9), a circulating water tank C (7), a water lifting pipe (11), a sewer pipe (12) and the like. The device used in the utility model is simple and easy to obtain, only needs to increase the circulating water body height (slightly higher than the duckweed purification device) in the operation process, the other processes are all realized by water body self-flow, the construction and operation cost is low, the management and maintenance are easy, the device is not limited by plant varieties, and the application of the plant purification device in water environment treatment is promoted.

Description

TECHNICAL FIELD

[0001] The utility model belongs to water body purification and clean production technical field, especially, relate to an open sewage purification circulating device structure technical field. BACKGROUND

[0002] In recent years, aquatic plants have been widely studied and applied in water pollution control. Duckweed is a small floating aquatic plant that has attracted much attention due to its fast growth, strong nitrogen and phosphorus absorption capacity, high biomass nutritional value (rich in protein, starch, and oil), and easy harvesting.

[0003] However, existing duckweed purification systems also have low pollutant removal efficiency and high methane gas emissions. This is because duckweed floating on the water surface cannot absorb pollutants in the lower water body, which limits the growth of duckweed and the removal of pollutants to some extent. At the same time, duckweed floating on the water surface also hinders the spread of oxygen to the water body, causing oxygen deficiency in the water body, which adversely affects the growth of aerobic microorganisms and the removal of pollutants. At the same time, it also promotes the production and emission of methane, making methane the greenhouse gas with the highest warming potential contribution rate (up to 86%) in the duckweed purification system. Therefore, increasing the dissolved oxygen (DO) concentration of the duckweed purification system and the migration rate of pollutants to the surface water body is the key to improving duckweed growth, promoting pollutant removal, and reducing methane emissions.

[0004] At present, water circulation technology has been reported to improve water purification efficiency, but mainly uses pipeline circulation and internal circulation to improve water power conditions, with poor improvement effect on dissolved oxygen. Internal circulation also disturbs the surface water body, which is not suitable for duckweed purification systems. For example, Chinese patent (Publication No. CN115947459A) discloses a closed water body construction self-circulation ecological purification system, which has the advantages of low capital investment and operating cost, simple maintenance and repair, and easy operation. However, the invention circulates through a closed pipeline, which does not significantly improve the dissolved oxygen concentration of the water body. In addition, Chinese patent (Publication No. CN202936242U) relates to a comprehensive treatment system for an external circulation oxygenation ecological system river, which has the characteristics of maintenance-free and low operating cost. However, the pipeline is still a closed pipeline, which requires an additional oxygenation control unit (a pipeline with micron-sized small holes) to achieve oxygenation. The micron-sized small holes are prone to clogging, making it difficult to use for a long time. At the same time, this technology requires a supporting microcomputer automatic control system, which has high construction cost and difficult operation and management. Therefore, for duckweed purification systems, it is extremely important to develop an open external circulation technology that does not disturb the water surface, has a significant oxygenation effect, and promotes the migration of pollutants from the lower water body to the surface. SUMMARY

[0005] The utility model discloses in order to solve above-mentioned problem defect, provide an open sewage purification circulating device and use method.

[0006] The utility model discloses the following technical scheme realizes.

[0007] An open sewage purification circulating device, the device includes the sewage purification body 5 of container, the open sewage purification circulating device includes:

[0008] Plant purification layer 1, plant purification layer 1 is arranged in the upper portion of sewage purification body 5,

[0009] Water inlet pipe 8 is arranged in the lower portion lateral wall of sewage purification body 5,

[0010] Water outlet pipe 2 is arranged in the upper portion lateral wall of sewage purification body 5,

[0011] Circulating water tank A3 is arranged in the lower portion of water outlet pipe 2,

[0012] U-shaped groove 4, one end of U-shaped groove 4 is arranged in the lower portion of circulating water tank A3,

[0013] Circulating water tank B9 is arranged in the lower portion of the other end of U-shaped groove 4,

[0014] The height of circulating water tank A3 is higher than the height of circulating water tank B9,

[0015] Circulating water tank C7 is arranged in one side of sewage purification body 5,

[0016] Water lifting pipe 11, one end is connected with circulating water pump 10 arranged in circulating water tank B9, and the other end is arranged in the upper portion of circulating water tank C7,

[0017] Drain pipe 12, one end is fixedly connected to the lateral wall of circulating water tank C7, and the other end is connected with water inlet pipe 8 of sewage purification body 5.

[0018] The method for using the open sewage purification circulating device, comprising the following steps:

[0019] Step 1) fills and lays the long-term deposited bottom mud in the bottom of sewage purification body 5,

[0020] Step 2) after injecting the water body to be purified to the horizontal position slightly higher than water outlet pipe 2, stops injecting,

[0021] Step 3) the plant variety described in the utility model is laid in plant purification layer 1,

[0022] Step 4) the water body to be purified flows out of sewage purification body 5 through water outlet pipe 2, and naturally falls into circulating water tank A (3) and carries out primary waterfall reoxygenation.

[0023] Step 5) The water body to be purified slowly flows through the U-shaped groove 4 arranged, and then naturally falls into the circulating water tank B9 to perform secondary drop water reoxygenation;

[0024] Step 6) The water body to be purified is lifted into the circulating water tank C7 from the circulating water tank B9 by the combination of the water lifting pipe 11 and the circulating water pump 10 to perform tertiary drop water reoxygenation;

[0025] Step 7) The water body to be purified in the circulating water tank C7 is returned to the lower part of the sewage purification body 5 through the water outlet pipe 12 to complete the circulation;

[0026] Step 8) Steps 1) to 7) are repeated.

[0027] The beneficial effects of the utility model are as follows:

[0028] 1. The utility model discloses a water force external circulation system installed on the periphery of a plant (such as duckweed) purification device, which solves the problems of low dissolved oxygen content, low pollutant removal efficiency and the limitation of directly aerating and increasing oxygen in the prior duckweed purification system, and achieves the purposes of effectively improving the water body DO content of the purification device, significantly promoting plant growth and pollutant removal efficiency, and significantly reducing the methane emission flux of the purification device.

[0029] 2. The utility model studies the slow flow rate relationship and result of the water body to be purified in the U-shaped groove, and finds out the relationship inclination angle of water quality and flow rate in different purification stages.

[0030] 3. The device used in the utility model is simple and easy to obtain, only needs to consume energy to lift the circulating water body height (slightly higher than the duckweed purification device) in the running process, and the rest of the process is realized by relying on the water body self-flow, so that the utility model has the advantages of low construction and running cost, easy management and maintenance, and no limitation of plant varieties, and is favorable to promoting the application of the plant purification device in water environment treatment.

[0031] The utility model will be further explained in combination with the drawings and specific embodiments. DRAWINGS

[0032] Figure 1 It is a structure schematic view of the utility model device. In the drawing, the marks are as follows: 1-plant purification layer, 2-water outlet pipe, 3-circulating water tank A, 4-U-shaped groove, 5-sewage purification body, 6-bottom mud layer, 7-circulating water tank C, 8-water inlet pipe, 9-circulating water tank B, 10-circulating water pump, 11-water lifting pipe, and 12-water outlet pipe.

[0033] Figure 2 It is the dissolved oxygen concentration and the improvement rate in the comparative example and the embodiment.

[0034] Figure 3Average removal rate and improvement rate of TN, TP, ammonia nitrogen and nitrate nitrogen in the comparative examples and examples.

[0035] Figure 4 Wet weight growth rate of duckweed in the comparative examples and examples.

[0036] Figure 5 Dry weight growth rate of duckweed in the comparative examples and examples.

[0037] Figure 6 CH4 emission flux in the comparative examples and examples. DETAILED DESCRIPTION

[0038] The following examples are only a part of the technical scheme of the present application, and are not a limitation on the whole technical scheme of the present application. The examples of the present application are provided to further explain and illustrate the technical scheme details of the present application.

[0039] See Figure 1 An open sewage purification circulating device, the device comprises a sewage purification body 5 which is a container; the open sewage purification circulating device comprises:

[0040] A plant purification layer 1 is arranged at the upper part of the sewage purification body 5;

[0041] A water inlet pipe 8 is arranged at the lower side wall of the sewage purification body 5;

[0042] A water outlet pipe 2 is arranged at the upper side wall of the sewage purification body 5;

[0043] A circulating water tank A 3 is arranged at a certain position below the water outlet pipe 2;

[0044] A U-shaped groove 4 is arranged at one end of the circulating water tank A 3;

[0045] A circulating water tank B 9 is arranged at a certain position below the other end of the U-shaped groove 4;

[0046] The height of the circulating water tank A 3 is higher than the height of the circulating water tank B 9;

[0047] A circulating water tank C 7 is arranged at one side of the sewage purification body 5;

[0048] A water lifting pipe 11 is connected with a circulating water pump 10 arranged in the circulating water tank B 9 at one end, and is arranged at a certain position above the circulating water tank C 7 at the other end;

[0049] A sewer pipe 12 is fixedly connected with the side wall of the circulating water tank C 7 at one end, and is connected with the water inlet pipe 8 of the sewage purification body 5 at the other end.

[0050] Further, the bottom of the sewage purification body 5 is provided with a bottom mud layer 6.

[0051] Further, the top of the circulating water tank A3, the circulating water tank B9 and the circulating water tank C7 is open.

[0052] Further, the height of the circulating water tank C7 is higher than the height of the sewage purification body 5.

[0053] Further, the U-shaped groove 4 is inclined; the included angle between the U-shaped groove 4 and the horizontal is 0.1°-0.5°.

[0054] Further, the included angle between the U-shaped groove 4 and the horizontal is 0.1°-0.2°.

[0055] Further, the included angle between the U-shaped groove 4 and the horizontal is 0.3°-0.5°.

[0056] Further, the plants in the plant purification layer 1 are duckweed or big ginger or willow leaf or lotus or red duckweed or round heart duckweed.

[0057] Further, the plants in the plant purification layer 1 are duckweed, and the coverage of duckweed in the sewage purification body 5 is 150g / m 2 -850g / m 2 . The coverage of duckweed in the sewage purification body 5 is too high or too low, which is not conducive to the growth of duckweed and the removal of pollutants.

[0058] The method for using the open sewage purification circulating device comprises the following steps:

[0059] Step 1) fill the long-term deposited bottom mud at the bottom of the sewage purification body 5;

[0060] Step 2) inject the water body to be purified to the water body slightly higher than the horizontal position of the water outlet pipe 2, and then stop injecting;

[0061] Step 3) the plant variety of the utility model is laid on the plant purification layer 1;

[0062] Step 4) the water body to be purified flows out of the sewage purification body 5 through the water outlet pipe 2, naturally falls into the circulating water tank A3, and carries out primary waterfall reoxygenation;

[0063] Step 5) the water body to be purified slowly flows through the U-shaped groove 4, and then naturally falls into the circulating water tank B9, and carries out secondary waterfall reoxygenation;

[0064] Step 6) The water body to be purified is lifted by the combination of the water lifting pipe 11 and the circulating water pump 10 from the circulating water tank B9 to the circulating water tank C7, and is subjected to three-stage water drop reoxygenation;

[0065] Step 7) The water body to be purified in the circulating water tank C7 is returned to the lower part of the sewage purification body 5 through the water outlet pipe 12, and the circulation is completed.

[0066] Step 8) Steps 1) to 7) are repeated.

[0067] The comparative example is different from Examples 1-5 in that there is no external circulation system, and the rest of the conditions are the same as in Examples 1-5. The sewage treatment and duckweed growth process lasts for 6 months, during which the excess duckweed is salvaged every 4 days, the dissolved oxygen (DO) content of the surface water body and the bottom water body in the middle of the duckweed purification device is measured every 2 days, the concentration of pollutants in the influent and effluent is measured every 4 days, and the removal rate of TN, TP, ammonia nitrogen and nitrate nitrogen of the duckweed purification device is calculated. The concentrations of various pollutants in the influent are shown in Table 1.

[0068] Table 1 Influent and effluent concentrations of TN, TP, ammonia nitrogen and nitrate nitrogen in the comparative example and examples

[0069]

[0070] The determination method of each pollutant and the removal rate calculation method are as follows:

[0071] Determination of TN in water body-UV spectrophotometry (GB 11894-89);

[0072] Determination of TP in water body-ammonium molybdate spectrophotometry (GB 11893-89);

[0073] Determination method of ammonia nitrogen in water body-UV spectrophotometry (HJ 535-2009);

[0074] Determination of nitrate nitrogen in water body-UV spectrophotometry (HJ / T 346-2007);

[0075] Removal rate of pollutants in sewage (%)=(concentration of pollutants in influent-concentration of pollutants in effluent) / concentration of pollutants in influent x 100;

[0076] Removal rate improvement of pollutants in sewage (%)=(removal rate of pollutants in examples-removal rate of pollutants in comparative example) / removal rate of pollutants in comparative example x 100;

[0077] The quantitative sampling operation of duckweed is as follows: 1 rectangular frame (made of PVC pipe with an outer diameter of 20 mm) is placed on the surface of the sewage in each duckweed purification device, and the water surface area in the frame is 0.1 m 2Collect all the duckweed within the frame, dehydrate it using a centrifuge (1 minute each time, twice in total), and weigh it to obtain the wet weight of the duckweed. Calculate the wet weight of each treatment area per 1m² based on the duckweed's wet weight. 2 The wet weight of duckweed on the water surface, the amount of duckweed to be harvested = (calculated per 1m of sampling) 2 Wet weight of duckweed on water surface - per 1m at initial inoculation 2 The wet weight of duckweed on the water surface is multiplied by the water surface area of ​​the treatment area. Based on the calculated amount of duckweed to be removed, the duckweed is removed to maintain a constant coverage rate on the wastewater surface after removal (550g wet weight / m²). 2 A certain amount of wet duckweed was weighed and dried in an oven at 60℃ until constant weight. The wet weight growth rate and dry weight growth rate of the duckweed were calculated based on the obtained weight data. The calculation method is as follows:

[0078] Wet weight growth rate of duckweed (g / m 2 / d)=(Wet weight of duckweed at the time of sampling - Wet weight of duckweed at the time of the last sampling) / Sampling water surface area / Sampling cycle;

[0079] Dry weight growth rate of duckweed (g / m 2 / d)=(dry weight of duckweed at the time of sampling - dry weight of duckweed at the time of the last sampling) / sampling water surface area / sampling cycle.

[0080] During long-term continuous operation, all duckweed purification devices underwent periodic (approximately every 10 days) greenhouse gas sampling at the atmosphere-water interface using the static sealed chamber method. Samples were collected once during the day (13:00-14:00) and once at night (22:00-23:00). The sampling device (length × width × height = 52.5cm × 36.5cm × 31.5cm) was equipped with a thermometer and a small fan (to mix the gas inside the chamber). Gas samples (300mL each) were collected from the sampling port using a sampler at 0 and 30 minutes after the chamber was closed.

[0081] CH4 emission flux of duckweed purification device (mg / m³) 2 / h) = Gas density (mol / m 3 ) × Static box volume (m 3 ) / Static box cross-sectional area (m 2 × Local atmospheric pressure (Pa) / Standard atmospheric pressure (Pa) × 237.15K / (237.15K + Average temperature inside the static chamber (°C)) × Slope of gas content change over time during the observation period

[0082] Comparative example:

[0083] As can be seen from the influent and effluent concentrations of each pollutant in Table 1, the effluent concentration in the comparative example is lower than the influent concentration, indicating that the pollutants have been removed.

[0084] Depend onFigure 2 It can be seen that the dissolved oxygen content was 2.18 mg / L during the 6-month period of wastewater treatment and duckweed growth in the comparative example.

[0085] Depend on Figure 3 The average removal rate data of pollutants shows that, over a period of 6 months during the comparative wastewater treatment and duckweed growth process, the removal rate of TN was 55.29%, the removal rate of TP was 38.40%, the removal rate of ammonia nitrogen was 50.04%, and the removal rate of nitrate nitrogen was 23.20%. These data indicate that TN removal was the most effective, and its removal effect was better than that of TP.

[0086] Depend on Figure 4 Duckweed wet weight growth rate and Figure 5 Data on the dry weight growth rate of duckweed showed that, over a 6-month period during the comparative wastewater treatment and duckweed growth process, the average wet weight growth rate of duckweed was 65.3 g / m³. 2 The average dry weight growth rate of duckweed was 4.86 g / m³ / day. 2 / d, duckweed grows relatively slowly.

[0087] Depend on Figure 6 The CH4 emission flux data from the duckweed purification device show that, over a continuous 6-month period of wastewater treatment and duckweed growth, the emission flux of the duckweed purification device was 17.58 mg / m³. 2 / h.

[0088] Example 1:

[0089] An open-type wastewater purification and circulation device and its usage method are disclosed. The device includes a duckweed purification unit (wastewater purification unit 5), which is 1.07m long, 0.78m wide, and 0.82m high, with a controlled water level of 0.64m. Duckweed is planted within the purification unit. An inlet pipe 8 and an outlet pipe 2 are respectively installed at both ends of the purification unit. An external circulation system is also provided. The external circulation system consists of a circulating water tank A3 placed below the outlet pipe 2 of the purification unit for primary cascading reoxygenation. Water from circulating water tank A3 flows slowly by gravity through an open U-shaped channel 4 into circulating water tank B9 for secondary cascading reoxygenation. A circulating water pump 10 is placed inside circulating water tank B9 to lift the incoming water to a circulating water tank C7 located above B9 and higher than the water surface of the purification unit for tertiary cascading reoxygenation. The outlet water from circulating water tank C7 is connected to the bottom inlet pipe 8 of the purification unit via a pipe, allowing the circulating water to flow by gravity into the purification unit, thus forming an open-type external circulation system. The circulating water flow rate is 0.25 L / min, and the circulation frequency is 1 cycle / day.

[0090] The implementation results of Example 1 are as follows:

[0091] As can be seen from the influent and effluent concentrations of each pollutant in Table 1, the effluent concentration in Example 1 is lower than the influent concentration, indicating that the pollutants have been removed. The effluent concentration in Example 1 is lower than the effluent concentration in the comparative example, indicating that Example 1 removed more pollutants.

[0092] Depend on Figure 2 It can be seen that during the 6-month period of wastewater treatment and duckweed growth in Example 1, the dissolved oxygen content was 3.91 mg / L, which was 1.73 mg / L higher than that of the comparative example.

[0093] Depend on Figure 3 The average pollutant removal rate data shows that, during the 6-month period of wastewater treatment and duckweed growth in Example 1, the removal rates of TN were 71.81%, TP was 46.84%, ammonia nitrogen was 63.50%, and nitrate nitrogen was 26.75%. Compared with the comparative example, the removal rates of TN, TP, ammonia nitrogen, and nitrate nitrogen increased by 29.88%, 21.98%, 26.90%, and 15.30%, respectively. Among them, the removal rates of TN, TP, and ammonia nitrogen increased significantly.

[0094] Depend on Figure 4 Duckweed wet weight growth rate and Figure 5 Data on the dry weight growth rate of duckweed showed that, during the six months of wastewater treatment and duckweed growth in Example 1, the average wet weight growth rate of duckweed was 67.07 g / m³. 2 The average dry weight growth rate of duckweed was 4.76 g / m³ / d. 2 / d, compared with the control, the wet weight growth rate increased by 1.77 g / m 2 / d, the dry weight growth rate did not increase significantly.

[0095] Depend on Figure 6 According to the CH4 emission flux data, during the six-month period of wastewater treatment and duckweed growth in Example 1, the emission flux of the duckweed purification device was 19.77 mg / m³. 2 / h.

[0096] Based on the data from Example 1 and the comparative example, and the above comparative analysis, compared with the comparative example, the dissolved oxygen increase rate of the water in the duckweed purification device in Example 1 was 79.36%, and the increases in TN, TP, ammonia nitrogen, and nitrate nitrogen removal rates were 29.88%, 21.98%, 26.90%, and 15.30%, respectively. The average wet weight growth rate of duckweed increased by 2.64%. These data indicate that this method can improve duckweed yield and the removal capacity of pollutants from wastewater.

[0097] Example 2:

[0098] The structure is the same as in Example 1. The circulating water flow rate is set to 0.5 L / min, and the circulation frequency is 2 times / day.

[0099] The results of implementing Example 2 are as follows:

[0100] As can be seen from the influent and effluent concentrations of each pollutant in Table 1, the effluent concentration in Example 2 is lower than the influent concentration, indicating that the pollutants have been removed. The effluent concentration in Example 2 is lower than the effluent concentration in the comparative example, indicating that Example 2 removed more pollutants.

[0101] Depend on Figure 2 It can be seen that during the 6-month period of wastewater treatment and duckweed growth in Example 2, the dissolved oxygen content was 4.86 mg / L, which was 2.68 mg / L higher than that of the comparative example.

[0102] Depend on Figure 3 The average pollutant removal rate data shows that, during the 6-month period of wastewater treatment and duckweed growth in Example 2, the removal rate of TN was 78.84%, the removal rate of TP was 54.14%, and the removal rate of ammonia nitrogen was 70.94%. Compared with the comparative example, the removal rates of TN, TP, and ammonia nitrogen increased by 42.59%, 40.99%, and 41.77%, respectively. The removal rates of TN, TP, and ammonia nitrogen were significantly improved.

[0103] Depend on Figure 4 Duckweed wet weight growth rate and Figure 5 Data on the dry weight growth rate of duckweed showed that, during the six months of wastewater treatment and duckweed growth in Example 2, the average wet weight growth rate of duckweed was 85.85 g / m³. 2 The average dry weight growth rate of duckweed was 6.27 g / m³ / d. 2 / d, compared with the control group, the wet weight and dry weight growth rates increased by 20.55 g / m², respectively. 2 / d、1.41g / m 2 / d.

[0104] Depend on Figure 6 According to the CH4 emission flux data, during the six-month period of wastewater treatment and duckweed growth in Example 2, the emission flux of the duckweed purification device was 12.38 mg / m³. 2 / h, compared with the comparative example, the emission flux of the duckweed purification device was reduced by 5.2 mg / m³. 2 / h.

[0105] Based on the data from Example 2 and the comparative example, and the above comparative analysis, compared with the comparative example, the dissolved oxygen in the water purified by the duckweed purification device in Example 2 increased by 122.94%, and the removal rates of TN, TP, and ammonia nitrogen increased by 42.59%, 40.99%, and 41.77%, respectively. The average wet weight and average dry weight growth rates of duckweed increased by 31.47% and 29.01%, respectively. These data indicate that this method can improve duckweed yield and the removal capacity of pollutants from wastewater, as well as reduce methane emissions.

[0106] Example 3:

[0107] The structure is the same as in Example 1. The circulating water flow rate is set to 1L / min, and the circulation frequency is 4 times / day.

[0108] The implementation results of Example 3 are as follows:

[0109] As can be seen from the influent and effluent concentrations of each pollutant in Table 1, the effluent concentration in Example 3 is lower than the influent concentration, indicating that the pollutants have been removed. The effluent concentration in Example 3 is lower than the effluent concentration in the comparative example, indicating that Example 3 removed more pollutants.

[0110] Depend on Figure 2 It can be seen that during the 6-month period of wastewater treatment and duckweed growth in Example 3, the dissolved oxygen content was 5.71 mg / L, which was 3.53 mg / L higher than that of the comparative example.

[0111] Depend on Figure 3 The average pollutant removal rate data shows that, during the 6-month period of wastewater treatment and duckweed growth in Example 3, the removal rate of TN was 85.99%, the removal rate of TP was 59.35%, and the removal rate of ammonia nitrogen was 76.50%. Compared with the comparative example, the removal rates of TN, TP, and ammonia nitrogen increased by 55.53%, 54.56%, and 52.88%, respectively. The removal rates of TN, TP, and ammonia nitrogen all increased significantly.

[0112] Depend on Figure 4 Duckweed wet weight growth rate and Figure 5 Data on the dry weight growth rate of duckweed showed that, during the six months of wastewater treatment and duckweed growth in Example 3, the average wet weight growth rate of duckweed was 106.33 g / m³. 2 The average dry weight growth rate of duckweed was 7.54 g / m³ / d. 2 / d, compared with the control group, the wet weight and dry weight growth rates increased by 41.03 g / m², respectively. 2 / d、2.68g / m 2 / d.

[0113] Depend on Figure 6CH4emission flux data, the emission flux of the duckweed purification device in Example 3 was 5.58 mg / m 2 / h during the 6-month process of sewage treatment and duckweed growth, which was 12 mg / m 2 / h less than that of the comparative example.

[0114] The data in Example 3 and the comparative example and the above comparative analysis showed that, compared with the comparative example, the increase rate of dissolved oxygen in the water body of the duckweed purification device in Example 3 was 161.93%, the increase rates of TN, TP and ammonia nitrogen removal were 55.53%, 54.56% and 52.88% respectively, and the increase rates of the average wet weight and the average dry weight growth rates of duckweed were 62.83% and 55.14% respectively. The above data showed that the method could improve the yield of duckweed and the removal capacity of pollutants in sewage, and reduce the emission of methane.

[0115] Example 4:

[0116] The structure was the same as that of Example 1. The circulating water flow rate was set to 1.5 L / min, and the circulating frequency was 6 times / day.

[0117] The implementation effect of Example 4 was as follows:

[0118] As can be seen from the concentration of each pollutant in and out of water in Table 1, the concentration of out of water in Example 4 was lower than that of in water, indicating that the pollutants were removed, and the concentration of out of water in Example 4 was lower than that of the comparative example, indicating that more pollutants were removed.

[0119] As can be seen from the concentration of each pollutant in and out of water in Table 1, the concentration of out of water in Example 4 was lower than that of in water, indicating that the pollutants were removed, and the concentration of out of water in Example 4 was lower than that of the comparative example, indicating that more pollutants were removed. Figure 2 As can be seen from the concentration of each pollutant in and out of water in Table 1, the concentration of out of water in Example 4 was lower than that of in water, indicating that the pollutants were removed, and the concentration of out of water in Example 4 was lower than that of the comparative example, indicating that more pollutants were removed.

[0120] As can be seen from the concentration of each pollutant in and out of water in Table 1, the concentration of out of water in Example 4 was lower than that of in water, indicating that the pollutants were removed, and the concentration of out of water in Example 4 was lower than that of the comparative example, indicating that more pollutants were removed. Figure 3 As can be seen from the concentration of each pollutant in and out of water in Table 1, the concentration of out of water in Example 4 was lower than that of in water, indicating that the pollutants were removed, and the concentration of out of water in Example 4 was lower than that of the comparative example, indicating that more pollutants were removed.

[0121] As can be seen from the concentration of each pollutant in and out of water in Table 1, the concentration of out of water in Example 4 was lower than that of in water, indicating that the pollutants were removed, and the concentration of out of water in Example 4 was lower than that of the comparative example, indicating that more pollutants were removed. Figure 4 As can be seen from the concentration of each pollutant in and out of water in Table 1, the concentration of out of water in Example 4 was lower than that of in water, indicating that the pollutants were removed, and the concentration of out of water in Example 4 was lower than that of the comparative example, indicating that more pollutants were removed. Figure 5 As can be seen from the concentration of each pollutant in and out of water in Table 1, the concentration of out of water in Example 4 was lower than that of in water, indicating that the pollutants were removed, and the concentration of out of water in Example 4 was lower than that of the comparative example, indicating that more pollutants were removed. 2 / d, and the average dry weight growth rate of duckweed was 8.24 g / m 2 / d, compared with the control group, the wet weight and dry weight growth rates increased by 45.59 g / m², respectively. 2 / d、3.38g / m 2 / d.

[0122] Depend on Figure 6 According to the CH4 emission flux data, during the six-month period of wastewater treatment and duckweed growth in Example 3, the emission flux of the duckweed purification device was 7.76 mg / m³. 2 / h, compared with the comparative example, the emission flux of the duckweed purification device was reduced by 9.82 mg / m³. 2 / h.

[0123] Based on the data from Example 4 and the comparative example, and the above comparative analysis, compared with the comparative example, the dissolved oxygen increase rate of the water in the duckweed purification device in Example 4 was 210.55%, and the increases in TN, TP, and ammonia nitrogen removal rates were 47.60%, 52.45%, and 55.74%, respectively. The increases in average wet weight and average dry weight growth rate of duckweed were 69.82% and 69.55%, respectively. These data indicate that this method can improve duckweed yield and the removal capacity of pollutants from wastewater, as well as reduce methane emissions.

[0124] Example 5:

[0125] The structure is the same as in Example 1. The circulating water flow rate is set to 2L / min, and the circulation frequency is 8 times / day.

[0126] The results of implementing Example 5 are as follows:

[0127] As can be seen from the influent and effluent concentrations of each pollutant in Table 1, the effluent concentration in Example 5 is lower than the influent concentration, indicating that the pollutants have been removed. The effluent concentration in Example 5 is lower than the effluent concentration in the comparative example, indicating that Example 5 removed more pollutants.

[0128] Depend on Figure 2 It can be seen that during the 6-month period of wastewater treatment and duckweed growth in Example 5, the dissolved oxygen content was 7.82 mg / L, which was 5.64 mg / L higher than that of the comparative example.

[0129] Depend on Figure 3 The average pollutant removal rate data shows that, during the 6-month period of wastewater treatment and duckweed growth in Example 5, the removal rate of TN was 84.38%, the removal rate of TP was 59.97%, and the removal rate of ammonia nitrogen was 79.50%. Compared with the comparative example, the removal rates of TN, TP, and ammonia nitrogen increased by 52.61%, 56.17%, and 58.87%, respectively. The removal rates of TN, TP, and ammonia nitrogen all increased significantly.

[0130] Depend on Figure 4 Duckweed wet weight growth rate and Figure 5Data on the dry weight growth rate of duckweed showed that, during the six months of wastewater treatment and duckweed growth in Example 5, the average wet weight growth rate of duckweed was 100.42 g / m³. 2 The average dry weight growth rate of duckweed was 7.81 g / m³ / d. 2 / d, compared with the control group, the wet weight and dry weight growth rates increased by 35.12 g / m², respectively. 2 / d、2.95g / m 2 / d.

[0131] Depend on Figure 6 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 According to the CH4 emission flux data, during the six-month period of wastewater treatment and duckweed growth in Example 3, the emission flux of the duckweed purification device was 8.69 mg / m³. 2 / h, compared with the comparative example, the emission flux of the duckweed purification device was reduced by 8.89 mg / m³. 2 / h.

[0132] Based on the data from Example 5 and the comparative example, and the above comparative analysis, compared with the comparative example, the dissolved oxygen in the water purified by the duckweed purification device in Example 5 increased by 258.71%, and the removal rates of TN, TP, and ammonia nitrogen increased by 52.61%, 56.17%, and 58.87%, respectively. The average wet weight and average dry weight growth rates of duckweed increased by 53.78% and 60.70%, respectively. These data indicate that this method can improve duckweed yield and the removal capacity of pollutants from wastewater, as well as reduce methane emissions.

[0133] Example 6: Study on the relationship between the inclination angle of the U-shaped trough and the flow velocity of the water to be purified within it, and the results thereof.

[0134] 6.1 Theoretical Basis: The Relationship Between Flow Velocity and Gradient

[0135] According to Manning's formula (open channel velocity formula):

[0136]

[0137] Where: V is the flow velocity, n is the roughness coefficient, R is the hydraulic radius, and S is the slope (i.e., sinθ, where θ is the angle between the U-shaped channel and the horizontal).

[0138] The flow velocity V is proportional to the square root of the slope S, so the smaller the slope, the slower the flow velocity. Theoretically, the flow velocity is minimum when the slope approaches zero, but in practice, a minimum flow velocity must be maintained to prevent deposition.

[0139] 6.2. Slope Range Reference in Practical Applications

[0140] (1) Irrigation canals

[0141] Recommended slope: 0.05% to 0.3% (corresponding to an angle of approximately 0.03° to 0.17°).

[0142] For example, the optimal slope for a trapezoidal channel is 0.1%-0.3% when the flow rate is 0.8 m 3 / s.

[0143] Key point: Too small a slope can lead to sedimentation, which needs to be adjusted in combination with soil permeability.

[0144] (2) Drainage pipes

[0145] Plastic pipes: Common slope 1%-3% (corresponding angle approximately 0.57° to 1.72°), balancing flow rate and material wear.

[0146] Minimum slope limit: Indoor drainage pipe slope is controlled within 25%, but affected by pipe diameter and material (e.g., 50 mm pipe minimum slope 12%).

[0147] (3) Farmland furrow irrigation

[0148] Slope recommendation: 0.005-0.02 (corresponding angle 0.03° to 0.11°), to evenly wet the soil.

[0149] 6.3. Calculation example

[0150] Assuming the required flow rate V = 0.3 m / s, Manning coefficient n = 0.013 (concrete), and hydraulic radius R = 0.3 m (U-shaped channel diameter 0.6 m, full flow):

[0151]

[0152] Corresponding angle:

[0153] θ = arcsin(S) ≈ 0.023

[0154] Considering a safety margin, the actual slope can be set to 0.1°-0.2°, still meeting the slow flow requirement.

[0155] 6.4. Conclusion and recommendations

[0156] Theoretical optimal range: 0.1° to 0.5°.

[0157] 0.1°: Maximize flow rate reduction, suitable for low-flow, low-roughness scenarios.

[0158] 0.5°: Provides self-cleaning ability, avoiding sedimentation, suitable for sediment-laden water flow.

[0159] Specific design: Needs to be determined through Manning formula calculation based on flow rate, roughness, and sediment characteristics. For example:

[0160] Clean water irrigation: 0.1°-0.2°.

[0161] Silt-laden water: 0.3°-0.5°.

[0162] By setting the slope reasonably, balance between slow water flow and preventing siltation can be achieved, and efficient operation of the U-shaped groove is ensured.

[0163] The above only is part of the specific embodiments of the utility model, the specific content or common sense in the scheme is not described too much here (including but not limited to abbreviations, abbreviations, units commonly used in the art). It should be pointed out that the above embodiments do not limit the utility model in any way, and for those skilled in the art, any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the utility model. The protection scope claimed in the present application shall be subject to the content of its claims, and the specific implementation mode and the like recorded in the specification can be used to explain the content of the claims.

Claims

1. An open sewage purification circulation device, said device comprising a sewage purification body (5) which is a container; characterized in that, The open sewage purification circulating device comprises: a plant purification layer (1) arranged at the upper part of a sewage purification body (5); a water inlet pipe (8) arranged at the lower side wall of the sewage purification body (5); a water outlet pipe (2) arranged at the upper side wall of the sewage purification body (5); a circulating water tank A (3) arranged at a certain position below the water outlet pipe (2); a U-shaped groove (4) with one end arranged in communication at the lower part of the circulating water tank A (3); a circulating water tank B (9) arranged at a certain position below the other end of the U-shaped groove (4); the height of the circulating water tank A (3) is higher than that of the circulating water tank B (9); a circulating water tank C (7) arranged at one side of the sewage purification body (5); a water lifting pipe (11) with one end connected with a circulating water pump (10) arranged in the circulating water tank B (9) and the other end arranged at a certain position above the circulating water tank C (7); a sewer pipe (12) with one end fixedly connected with the side wall of the circulating water tank C (7) and the other end connected with the water inlet pipe (8) of the sewage purification body (5).

2. The open sewage purification circulating device according to claim 1, characterized in that, The bottom of the sewage purification body (5) is provided with a bottom mud layer (6).

3. The open sewage purification circulating device according to claim 1, characterized by The top of the circulating water tank A (3), the circulating water tank B (9) and the circulating water tank C (7) is open.

4. The open sewage purification circulating device according to claim 1, characterized by The height of the circulating water tank C (7) is higher than that of the sewage purification body (5).

5. The open sewage purification circulating device according to claim 1, characterized by The U-shaped groove (4) is arranged obliquely; the included angle between the U-shaped groove (4) and the horizontal plane is arranged to be between 0.1° and 0.5°.

6. The open sewage purification circulating device according to claim 5, wherein The included angle between the U-shaped groove (4) and the horizontal plane is arranged to be between 0.1° and 0.2°.

7. The open sewage purification circulating device according to claim 5, characterized in that, The included angle between the U-shaped groove (4) and the horizontal plane is arranged to be between 0.3° and 0.5°.

8. The open sewage purification circulating device according to claim 1, characterized by The plants in the plant purification layer (1) are duckweed, hydrilla verticillata, samolus valerandi, eichhornia crassipes, azolla pinnata or lemnas rotundifolia.

9. The open sewage purification circulating device according to claim 1, characterized by The plants in the plant purification layer (1) are duckweed, and the coverage of duckweed in the sewage purification body (5) is 150g / m 2 ~ 850g / m 2 .

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