Open type sewage purification circulating device and use method

Abstract

The invention relates to an open type sewage purification circulating device and a use method. 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 invention 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 present invention belongs to the technical field of water purification and clean production, and in particular relates to the technical field of an open sewage purification and recycling device and its usage method. Background Art

[0002] In recent years, aquatic plants have been widely studied and applied in the field of water pollution treatment. Duckweed is a small floating aquatic plant, and it has attracted much attention due to its many advantages such as fast growth, strong nitrogen and phosphorus absorption ability, high biomass nutritional value (rich in protein, starch, oil, etc.), and easy harvesting.

[0003] However, the existing duckweed purification systems also have problems of low pollutant removal efficiency and high methane gas emissions. This is because the duckweed floating on the water surface cannot absorb pollutants in the lower layer of water, which to a certain extent limits the growth of duckweed and pollutant removal. At the same time, the duckweed floating on the water surface also hinders the expansion of oxygen into the water body, causing hypoxia in the water, which will have an adverse impact on the growth of aerobic microorganisms and pollutant removal. At the same time, it will also promote the generation and emission of methane, making methane the greenhouse gas with the highest contribution rate to the global warming potential of the duckweed purification system (up to 86%). Therefore, increasing the dissolved oxygen (DO) concentration in the water body 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 the present stage, although there have been certain reports on water circulation technology in improving the water purification efficiency, it mainly adopts pipeline circulation and internal circulation, mainly to improve the hydrodynamic conditions, and the improvement effect on dissolved oxygen is poor. The internal circulation will also disturb the surface water body and is not suitable for use in the duckweed purification system. For example, Chinese Patent (Publication No.: CN115947459A) discloses a self-circulating ecological purification system for constructing a closed water body, which has advantages such as low capital investment and operation cost, simple maintenance and repair, and easy operation. However, this invention circulates through a closed pipeline and has no obvious improvement in the dissolved oxygen concentration of the water body. In addition, the content of Chinese Patent (Publication No.: CN202936242U) relates to a comprehensive treatment system for a river with an external circulation reoxygenation ecosystem. Although this comprehensive treatment system has the characteristics of being maintenance-free and low operation cost, its pipeline is still a closed pipeline, and it needs to achieve oxygenation through an additional installed reoxygenation control unit (a pipeline with micron-sized holes). Its micron-sized holes are easy to block and not suitable for long-term use. At the same time, this technology requires a supporting microcomputer automatic control system, which has a high construction cost and a large operation and management difficulty. Therefore, for the duckweed purification system, developing an open external circulation technology that does not disturb the water surface, has a significant oxygenation effect, and can promote the migration of pollutants in the lower layer of water to the surface layer is extremely important for improving the growth rate of duckweed, promoting pollutant removal, and reducing methane emissions. Summary of the Invention

[0005] The present invention precisely aims to solve the above-mentioned problems and deficiencies, and provides an open sewage purification and recycling device and its usage method.

[0006] The present invention is implemented by the following technical solutions.

[0007] An open sewage purification and recycling device, the device includes a sewage purification body 5 which is a container; the open sewage purification and recycling device includes:

[0008] A plant purification layer 1, which is arranged on the upper part of the sewage purification body 5;

[0009] An inlet pipe 8, which is arranged on the lower side wall of the sewage purification body 5;

[0010] An outlet pipe 2, which is arranged on the upper side wall of the sewage purification body 5;

[0011] A circulation water tank A 3, which is arranged at a certain position below the outlet pipe 2;

[0012] A U-shaped groove 4, one end of the U-shaped groove 4 is connected and communicated with the lower part of the circulation water tank A 3;

[0013] A circulation water tank B 9, which is arranged at a certain position below the other end of the U-shaped groove 4;

[0014] The height of the circulation water tank A 3 is higher than the height of the circulation water tank B 9;

[0015] A circulation water tank C 7, which is arranged on one side of the sewage purification body 5;

[0016] A lift pipe 11, one end of which is connected to a circulation water pump 10 arranged in the circulation water tank B 9, and the other end is arranged at a certain position above the circulation water tank C 7;

[0017] A down pipe 12, one end of which is fixedly connected to the side wall of the circulation water tank C 7, and the other end is connected to the inlet pipe 8 of the sewage purification body 5.

[0018] The method of using the open sewage purification and recycling device of the present invention includes the following steps:

[0019] Step 1) Lay the long-term deposited bottom mud at the bottom of the sewage purification body 5;

[0020] Step 2) Inject the water to be purified until the water level is slightly higher than the horizontal position of the outlet pipe 2 and then stop injecting;

[0021] Step 3) Lay the plant varieties of the present invention on the plant purification layer 1;

[0022] Step 4) The water to be purified flows out of the sewage purification body 5 through the outlet pipe 2 and naturally drops into the circulation water tank A (3) for primary drop aeration;

[0023] Step 5) The water body to be purified slowly flows through the provided U-shaped groove 4, and then naturally drops into the circulation water tank B9 for secondary drop aeration and reoxygenation.

[0024] Step 6) The water body to be purified is lifted from the circulation water tank B9 to the circulation water tank C7 by the combination of the lift pipe 11 and the circulation water pump 10 for tertiary drop aeration and reoxygenation.

[0025] Step 7) The water body to be purified in the circulation water tank C7 flows back to the lower part of the sewage purification body 5 through the down pipe 12 to complete the circulation.

[0026] Step 8) Repeat Steps 1) to 7).

[0027] The beneficial effects of the present invention are as follows:

[0028] 1. By installing a hydraulic external circulation system around the plant (such as duckweed) purification device, the present invention solves the limitations of the existing duckweed purification system, such as low dissolved oxygen content, low pollutant removal efficiency, and inability to directly aerate and increase oxygen. It achieves the purpose of effectively increasing the DO content of the water body in 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 present invention studies the slow flow velocity relationship and results of the water body to be purified in the U-shaped groove, and finds out the relationship inclination angle between water quality and flow velocity at different purification stages.

[0030] 3. The device used in the present invention is simple and easy to obtain. During the operation process, only the energy consumption for lifting the height of the circulating water body (slightly higher than the duckweed purification device) is required, and the rest of the process is entirely achieved by the self-flow of the water body. Its construction and operation costs are low, it is easy to manage and maintain, and it is not restricted by plant varieties, which is beneficial to promoting the application of plant purification devices in water environment treatment.

[0031] The following further explains the present invention in conjunction with the accompanying drawings and specific embodiments. Description of the Drawings

[0032] Figure 1 It is a schematic structural diagram of the device of the present invention. The marks in the figure are: 1 - plant purification layer, 2 - outlet pipe, 3 - circulation water tank A, 4 - U-shaped groove, 5 - sewage purification body, 6 - bottom mud layer, 7 - circulation water tank C, 8 - inlet pipe, 9 - circulation water tank B, 10 - circulation water pump, 11 - lift pipe, 12 - down pipe.

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

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

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

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

[0037] Figure 6 For the CH4 emission flux in the comparative examples and examples. Detailed implementation manners

[0038] The following examples are only part of the technical solutions of the present invention and do not limit all the technical solutions of the present invention. The examples of the present invention are provided to further explain and illustrate the details of the technical solutions of the present invention.

[0039] See Figure 1 As shown. An open sewage purification and recycling device, the device includes a sewage purification body 5 that is a container; the open sewage purification and recycling device includes:

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

[0041] An inlet pipe 8, arranged on the lower side wall of the sewage purification body 5;

[0042] An outlet pipe 2, arranged on the upper side wall of the sewage purification body 5;

[0043] A circulation water tank A3, arranged at a certain position below the outlet pipe 2;

[0044] A U-shaped groove 4, one end of the U-shaped groove 4 is connected and communicated with the lower part of the circulation water tank A3;

[0045] A circulation water tank B9, arranged at a certain position below the other end of the U-shaped groove 4;

[0046] The height of the circulation water tank A3 is higher than the height of the circulation water tank B9;

[0047] A circulation water tank C7, arranged on one side of the sewage purification body 5;

[0048] A lifting pipe 11, one end is connected to a circulation water pump 10 arranged in the circulation water tank B9, and the other end is arranged at a certain position above the circulation water tank C7;

[0049] A down pipe 12, one end is fixedly connected to the side wall of the circulation water tank C7, and the other end is connected to the inlet pipe 8 of the sewage purification body 5.

[0050] Furthermore, a bottom mud layer 6 is arranged at the bottom of the sewage purification body 5 of the present invention.

[0051] Furthermore, the tops of the circulation water tank A3, the circulation water tank B9 and the circulation water tank C7 of the present invention are all open - set.

[0052] Furthermore, the height of the circulation water tank C7 of the present invention is higher than the height of the sewage purification body 5.

[0053] Furthermore, the U - shaped groove 4 of the present invention is inclined; the included angle between the U - shaped groove 4 and the horizontal is set between 0.1° and 0.5°.

[0054] Furthermore, the included angle between the U - shaped groove 4 and the horizontal of the present invention is set between 0.1° and 0.2°.

[0055] Furthermore, the included angle between the U - shaped groove 4 and the horizontal of the present invention is set between 0.3° and 0.5°.

[0056] Furthermore, the plants in the plant purification layer 1 of the present invention are duckweed or pistia stratiotes or salvinia natans or water hyacinth or azolla or pennywort.

[0057] Furthermore, the plant in the plant purification layer 1 of the present invention is duckweed, and the coverage rate of duckweed in the sewage purification body 5 is 150g / m 2 ~850g / m 2 . If the coverage rate of duckweed in the sewage purification body 5 is too high or too low, it is not conducive to the growth of duckweed and the removal of pollutants.

[0058] The method of using the open - type sewage purification circulation device of the present invention includes the following steps:

[0059] Step 1) Lay 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 until the water level is slightly higher than the horizontal position of the water outlet pipe 2, and then stop injecting;

[0061] Step 3) Lay the plant varieties of the present invention in 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 and naturally drops into the circulation water tank A3 for primary drop - water reoxygenation;

[0063] Step 5) The water body to be purified slowly flows through the set U - shaped groove 4, and then naturally drops into the circulation water tank B9 for secondary drop - water reoxygenation;

[0064] Step 6) The water body to be purified is lifted from the circulation water tank B9 to the circulation water tank C7 through the combination of the lift pipe 11 and the circulation water pump 10 for tertiary drop - water reoxygenation;

[0065] Step 7) The water body to be purified in the circulation water tank C7 flows back to the lower part of the sewage purification body 5 through the sewer pipe 12 to complete the circulation;

[0066] Step 8) Repeat Step 1) to Step 7).

[0067] Compared with Examples 1-5, the difference in the comparative example is that there is no external circulation system, and the other conditions are the same as those in Examples 1-5. The sewage treatment and duckweed growth processes lasted for 6 months. During this period, the excess duckweed was salvaged every 4 days, the dissolved oxygen (DO) content of the surface water and bottom water in the middle of the duckweed purification device was measured every 2 days, and the concentrations of pollutants in the influent and effluent were measured every 4 days, and the removal rates of TN, TP, ammonia nitrogen, and nitrate nitrogen in the sewage by the duckweed purification device were 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 measurement methods of various pollutants and the calculation method of the removal rate are as follows:

[0071] Determination of TN in water body - ultraviolet 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 - ultraviolet spectrophotometry (HJ 535--2009);

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

[0075] Pollutant removal rate in sewage (%) = (pollutant concentration in influent - pollutant concentration in effluent) / pollutant concentration in influent × 100;

[0076] Pollutant removal improvement rate in sewage (%) = (pollutant removal rate in example - pollutant removal rate in comparative example) / pollutant removal rate in comparative example × 100;

[0077] The quantitative sampling operation of duckweed is as follows: Place 1 rectangular frame (made of PVC pipe with an outer diameter of 20 mm) on the sewage surface of each duckweed purification device. The water surface area in the frame is 0.1 m 2 , Scoop up all the duckweed in the frame, dehydrate the scooped duckweed with a centrifugal dryer (dehydrate for 1 minute each time, a total of 2 times), and then weigh it to obtain the wet weight of the duckweed. Calculate the wet weight of duckweed per 1 m in each treatment area according to the wet weight of the duckweed 2The wet weight of duckweed on the water surface, the amount of duckweed salvaged = (the wet weight of duckweed per 1 m calculated by sampling - the wet weight of duckweed per 1 m at the initial inoculation) × the water surface area of the treatment area. Salvage duckweed according to the calculated amount of duckweed salvaged to keep the coverage rate of duckweed on the sewage surface constant (550 g wet weight / m 2 ). Weigh a certain amount of wet duckweed and dry it in an oven at 60 °C until it reaches a constant weight and then weigh it. Calculate the wet weight growth rate and dry weight growth rate of duckweed according to the obtained weight data. The calculation methods are as follows: 2 ). Weigh a certain amount of wet duckweed and dry it in an oven at 60 °C until it reaches a constant weight and then weigh it. Calculate the wet weight growth rate and dry weight growth rate of duckweed according to the obtained weight data. The calculation methods are as follows: 2 ). Weigh a certain amount of wet duckweed and dry it in an oven at 60 °C until it reaches a constant weight and then weigh it. Calculate the wet weight growth rate and dry weight growth rate of duckweed according to the obtained weight data. The calculation methods are as follows:

[0078] The wet weight growth rate of duckweed (g / m 2 / d) = (the wet weight of duckweed at sampling - the wet weight of duckweed at the previous sampling) / the sampling water surface area / the sampling period;

[0079] The dry weight growth rate of duckweed (g / m 2 / d) = (the dry weight of duckweed at sampling - the dry weight of duckweed at the previous sampling) / the sampling water surface area / the sampling period.

[0080] During the long-term continuous operation of all duckweed purification devices, greenhouse gas sampling is regularly carried out (about every 10 days) at the air-water interface using the static closed chamber method. Samples are collected once during the day (13:00 - 14:00 at noon) and once at night (22:00 - 23:00 at night). The sampling device (length × width × height = 52.5 cm × 36.5 cm × 31.5 cm) is equipped with a thermometer and a small fan (to mix the gas in the chamber). Gas samples (300 mL) are collected from the sampling port using a sampler at 0 and 30 min after closing the chamber.

[0081] The CH4 emission flux of the duckweed purification device (mg / m 2 / h) = gas density (mol / m 3 ) × static chamber volume (m 3 ) / static chamber cross-sectional area (m 2 ) × local air pressure (Pa) / standard atmospheric pressure (Pa) × 237.15 K / (237.15 K + average temperature in the static chamber (°C)) × slope of the change in gas content over time during the observation period

[0082] Control example:

[0083] From the influent and effluent concentrations of each pollutant in Table 1, it can be seen that the effluent concentration in the control example is lower than the influent concentration, indicating that the pollutants are removed.

[0084] From Figure 2 it can be seen that during the 6 months of the control example's sewage treatment and duckweed growth process, the dissolved oxygen content is 2.18 mg / L.

[0085] FromFigure 3 From the data of the average pollutant removal rate, during the 6 months of the sewage treatment in the comparative example and the 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%. From these data, it can be seen that the removal effect of TN was the best, and the removal effect of TN was better than that of TP.

[0086] From Figure 4 the wet weight growth rate of duckweed and Figure 5 the dry weight growth rate of duckweed data, during the 6 months of the sewage treatment in the comparative example and the duckweed growth process, the average wet weight growth rate of duckweed was 65.3 g / m 2 / d, and the average dry weight growth rate of duckweed was 4.86 g / m 2 / d, and the growth of duckweed was relatively slow.

[0087] From Figure 6 the CH4 emission flux data of the duckweed purification device, during the 6 months of the sewage treatment in the comparative example and the duckweed growth process, the emission flux of the duckweed purification device was 17.58 mg / m 2 / h.

[0088] Example 1:

[0089] An open sewage purification circulation device and its use method, including the duckweed purification device body (sewage purification body 5), the duckweed purification device body is 1.07 m long, 0.78 m wide, and 0.82 m high, the water body height is controlled at 0.64 m, duckweed is planted in the duckweed purification device body, and a water inlet pipe 8 and a water outlet pipe 2 are respectively arranged at both ends of the duckweed purification device body. An external circulation system is also provided. The external circulation device is to place a circulation water tank A3 under the water outlet pipe 2 of the duckweed purification device body for primary drop aeration and reoxygenation. The water in the circulation water tank A3 slowly flows into the circulation water tank B9 through an open U-shaped groove 4 for secondary drop aeration and reoxygenation. A circulation water pump 10 is placed in the circulation water tank B9 to lift the inflowing water to the circulation water tank C7 above the circulation water tank B9 and higher than the water surface of the duckweed purification device for tertiary drop aeration and reoxygenation. The water outlet of the circulation water tank C7 is connected to the bottom water inlet pipe 8 of the duckweed purification device through a pipeline, and the circulating water flows into the duckweed purification device through this pipeline by self-flow, constituting an open external circulation system. Among them, the circulating water flow rate is 0.25 L / min, and the circulation frequency is 1 time / day.

[0090] The implementation effect of Example 1 is as follows:

[0091] From the influent and effluent concentrations of each pollutant in Table 1, it can be seen that the effluent concentration in Example 1 was lower than the influent concentration, indicating that the pollutants were removed. The effluent concentration in Example 1 was lower than the effluent concentration in the comparative example, indicating that Example 1 removed more pollutants.

[0092] As can be seen from Figure 2 Figure 2 , during the 6 months of sewage treatment and duckweed growth in Example 1, the dissolved oxygen content was 3.91 mg / L, and compared with the comparative example, the dissolved oxygen increased by 1.73 mg / L.

[0093] As can be seen from Figure 3 the average pollutant removal rate data, during the 6 months of sewage treatment and duckweed growth in Example 1, the removal rate of TN was 71.81%, the removal rate of TP was 46.84%, the removal rate of ammonia nitrogen was 63.50%, and the removal rate of 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] As can be seen from Figure 4 the duckweed wet weight growth rate and Figure 5 the duckweed dry weight growth rate data, during the 6 months of sewage treatment and duckweed growth in Example 1, the average wet weight growth rate of duckweed was 67.07 g / m 2 / d, and the average dry weight growth rate of duckweed was 4.76 g / m 2 / d. Compared with the comparative example, the wet weight growth rate increased by 1.77 g / m 2 / d, and the dry weight growth rate did not increase significantly.

[0095] As can be seen from Figure 6 the CH4 emission flux data, during the 6 months of sewage treatment and duckweed growth in Example 1, the emission flux of the duckweed purification device was 19.77 mg / m 2 / h.

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

[0097] Example 2:

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

[0099] The implementation effect of Example 2 is as follows:

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

[0101] From Figure 2 it can be seen that during the 6 months of the sewage treatment and duckweed growth process in Example 2, the dissolved oxygen content was 4.86 mg / L. Compared with the comparative example, the dissolved oxygen increased by 2.68 mg / L.

[0102] From Figure 3 the data of the average pollutant removal rate, it can be seen that during the 6 months of the sewage treatment and duckweed growth process 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 increased significantly.

[0103] From Figure 4 the duckweed wet weight growth rate and Figure 5 the duckweed dry weight growth rate data, it can be seen that during the 6 months of the sewage treatment and duckweed growth process in Example 2, the average wet weight growth rate of duckweed was 85.85 g / m 2 / d, and the average dry weight growth rate of duckweed was 6.27 g / m 2 / d. Compared with the comparative example, the wet weight and dry weight growth rates increased by 20.55 g / m 2 / d and 1.41 g / m 2 / d respectively.

[0104] From Figure 6 the CH4 emission flux data, it can be seen that during the 6 months of the sewage treatment and duckweed growth process in Example 2, the emission flux of the duckweed purification device was 12.38 mg / m 2 / h. Compared with the comparative example, the emission flux of the duckweed purification device decreased by 5.2 mg / m 2 / h.

[0105] Based on the data in Example 2 and the comparative example and the above comparative analysis, compared with the comparative example, the increase rate of dissolved oxygen in the water body of the duckweed purification device in Example 2 was 122.94%, the increase rates of the removal of TN, TP, and ammonia nitrogen were 42.59%, 40.99%, and 41.77% respectively, and the increase rates of the average wet weight and average dry weight growth rates of duckweed were 31.47% and 29.01% respectively. The above data show that this method can improve the duckweed yield and the removal ability of pollutants in sewage, as well as reduce methane emissions.

[0106] Example 3:

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

[0108] The implementation effect of Example 3 is as follows:

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

[0110] From Figure 2 it can be seen that during the 6 months of the sewage treatment and duckweed growth process in Example 3, the dissolved oxygen content is 5.71 mg / L. Compared with the comparative example, the dissolved oxygen increases by 3.53 mg / L.

[0111] From Figure 3 the average pollutant removal rate data, it can be seen that during the 6 months of the sewage treatment and duckweed growth process in Example 3, the removal rate of TN is 85.99%, the removal rate of TP is 59.35%, and the removal rate of ammonia nitrogen is 76.50%. Compared with the comparative example, the removal rates of TN, TP, and ammonia nitrogen increase by 55.53%, 54.56%, and 52.88% respectively. The removal rates of TN, TP, and ammonia nitrogen all increase significantly.

[0112] From Figure 4 the wet weight growth rate of duckweed and Figure 5 the dry weight growth rate of duckweed data, it can be seen that during the 6 months of the sewage treatment and duckweed growth process in Example 3, the average wet weight growth rate of duckweed is 106.33 g / m 2 / d, and the average dry weight growth rate of duckweed is 7.54 g / m 2 / d. Compared with the comparative example, the wet weight and dry weight growth rates increase by 41.03 g / m 2 / d and 2.68 g / m 2 / d respectively.

[0113] From Figure 6 the CH4 emission flux data, it can be seen that during the 6 months of the sewage treatment and duckweed growth process in Example 3, the emission flux of the duckweed purification device is 5.58 mg / m 2 / h. Compared with the comparative example, the emission flux of the duckweed purification device decreases by 12 mg / m 2 / h.

[0114] Based on the data in Comprehensive Example 3 and the Comparative Example and the above comparative analysis, compared with the Comparative Example, the increase rate of dissolved oxygen in the water body of the duckweed purification device in Example 3 is 161.93%, and the increase rates of TN, TP, and ammonia nitrogen removal are 55.53%, 54.56%, and 52.88% respectively. The increase rates of the average wet weight and average dry weight growth rates of duckweed are 62.83% and 55.14%. The above data show that this method can improve the duckweed yield, the removal ability of pollutants in sewage, and reduce methane emissions.

[0115] Example 4:

[0116] The structure is the same as that in Example 1. Set the circulating water flow rate to 1.5 L / min and the circulation frequency to 6 times per day.

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

[0118] From the influent and effluent concentrations of each pollutant in Table 1, it can be seen that the effluent concentration in Example 4 is lower than the influent concentration, indicating that the pollutants are removed. The effluent concentration in Example 4 is lower than the effluent concentration in the Comparative Example, indicating that Example 4 removes more pollutants.

[0119] From Figure 2 it can be seen that during the 6 months of the sewage treatment and duckweed growth process in Example 4, the dissolved oxygen content is 6.77 mg / L. Compared with the Comparative Example, the dissolved oxygen increases by 4.59 mg / L.

[0120] From Figure 3 the average pollutant removal rate data, it can be seen that during the 6 months of the sewage treatment and duckweed growth process in Example 4, the removal rate of TN is 81.61%, the removal rate of TP is 58.54%, and the removal rate of ammonia nitrogen is 77.93%. Compared with the Comparative Example, the removal rates of TN, TP, and ammonia nitrogen increase by 47.60%, 52.45%, and 55.74% respectively. The removal rates of TN, TP, and ammonia nitrogen all increase significantly.

[0121] From Figure 4 the duckweed wet weight growth rate and Figure 5 the duckweed dry weight growth rate data, it can be seen that during the 6 months of the sewage treatment and duckweed growth process in Example 4, the average wet weight growth rate of duckweed is 110.89 g / m 2 / d, and the average dry weight growth rate of duckweed is 8.24 g / m 2 / d. Compared with the Comparative Example, the wet weight and dry weight growth rates increase by 45.59 g / m 2 / d and 3.38 g / m 2 / d respectively.

[0122] From Figure 6From the CH4 emission flux data, during the 6 months of sewage treatment and duckweed growth in Example 3, the emission flux of the duckweed purification device was 7.76 mg / m 2 / h. Compared with the comparative example, the emission flux of the duckweed purification device decreased by 9.82 mg / m 2 / h.

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

[0124] Example 5:

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

[0126] The implementation effect of Example 5 is as follows:

[0127] From the influent and effluent concentrations of each pollutant in Table 1, it can be seen that the effluent concentration in Example 5 was lower than the influent concentration, indicating that the pollutants were removed. The effluent concentration in Example 5 was lower than that in the comparative example, indicating that Example 5 removed more pollutants.

[0128] From Figure 2 it can be seen that during the 6 months of sewage treatment and duckweed growth in Example 5, the dissolved oxygen content was 7.82 mg / L. Compared with the comparative example, the dissolved oxygen increased by 5.64 mg / L.

[0129] From Figure 3 the average pollutant removal rate data, during the 6 months of sewage 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] From Figure 4 the duckweed wet weight growth rate and Figure 5 the duckweed dry weight growth rate data, during the 6 months of sewage treatment and duckweed growth in Example 5, the average wet weight growth rate of duckweed was 100.42 g / m 2 / d, and the average dry weight growth rate of duckweed was 7.81 g / m 2 / d. Compared with the comparative example, the growth rates of wet weight and dry weight increased by 35.12 g / m 2 / d and 2.95 g / m 2 / d, respectively.

[0131] From Figure 6 the CH4 emission flux data, it can be seen that during the 6 months when the sewage treatment and duckweed growth process of Example 3 continued, the emission flux of the duckweed purification device was 8.69 mg / m 2 / h. Compared with the comparative example, the emission flux of the duckweed purification device decreased by 8.89 mg / m 2 / h.

[0132] Based on the data in Example 5 and the comparative example and the above comparative analysis, it can be seen that compared with the comparative example, the increase rate of dissolved oxygen in the water body of the duckweed purification device in Example 5 was 258.71%, and the increase rates of TN, TP, and ammonia nitrogen removal were 52.61%, 56.17%, and 58.87%, respectively. The increase rates of the average wet weight and average dry weight growth rates of duckweed were 53.78% and 60.70%. The above data show that this method can improve the duckweed yield, the removal ability of pollutants in sewage, and reduce methane emissions.

[0133] Research on the relationship between the inclination angle of the U-shaped groove in Example 6 and the flow rate of the water body to be purified therein and the results

[0134] 6.1 Theoretical basis: The relationship between flow rate and slope

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

[0136]

[0137] Where: V is the flow rate, 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 groove and the horizontal).

[0138] The flow rate V is proportional to the square root of the slope S. Therefore, the smaller the slope, the slower the flow rate. Theoretically, the flow rate is the smallest when the slope approaches zero, but a minimum flow rate needs to be maintained in practice to prevent sedimentation.

[0139] 6.2. Reference for the slope range in practical applications

[0140] (1) Irrigation channels

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

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

[0143] Key point: If the slope is too small, it is easy to cause sedimentation, and it is necessary to adjust in combination with the soil permeability.

[0144] (2) Drainage pipes

[0145] Plastic pipes: The common slope is 1%-3% (corresponding to angles of about 0.57° to 1.72°), balancing the flow velocity and material wear.

[0146] Minimum slope limit: The slope of indoor drainage pipes is controlled within 25%, but it is affected by the pipe diameter and material (e.g., the minimum slope of a 50mm pipe is 12%).

[0147] (3) Farmland furrow irrigation

[0148] Slope recommendation: 0.005 - 0.02 (corresponding to angles of 0.03° to 0.11°) to uniformly moisten the soil.

[0149] 6.3. Calculation example

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

[0151]

[0152] Corresponding angle:

[0153] θ = arcsin(S) ≈ 0.023

[0154] Considering the safety margin, the actual slope can be set to 0.1° - 0.2°, which can still meet the slow flow requirements.

[0155] 6.4 Conclusions and suggestions

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

[0157] 0.1°: Minimize the flow velocity, suitable for low-flow and low-roughness scenarios.

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

[0159] Specific design: It needs to be determined by calculation through the Manning formula according to the flow rate, roughness, and sediment characteristics. For example:

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

[0161] Sediment-laden drainage: 0.3° - 0.5°.

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

[0163] The above are only some specific embodiments of the present invention, and the specific content or common knowledge well known in the art is not described in detail herein (including but not limited to abbreviations, contractions, and units commonly used in the art). It should be noted that the above embodiments do not limit the present invention in any way. For those skilled in the art, any technical solutions obtained by means of equivalent substitution or equivalent transformation fall within the protection scope of the present invention. The protection scope required by this application shall be subject to the content of its claims, and the specific implementation manners described in the specification can be used to interpret the content of the claims.

Claims

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

2. The open sewage purification and recycling device according to claim 1, characterized in that A bottom sludge layer (6) is arranged at the bottom of the sewage purification body (5).

3. The open sewage purification and recycling device according to claim 1, characterized in that, The tops of the circulation water tank A (3), the circulation water tank B (9) and the circulation water tank C (7) are all open.

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

5. The open sewage purification and recycling device according to claim 1, characterized in that, The U-shaped groove (4) is inclined; the included angle between the U-shaped groove (4) and the horizontal is set between 0.1° and 0.5°.

6. The open sewage purification and recycling device according to claim 5, characterized in that The included angle between the U-shaped groove (4) and the horizontal is set between 0.1° and 0.2°.

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

8. The open sewage purification and recycling device according to claim 1, characterized in that The plants in the plant purification layer (1) are duckweed or pistia stratiotes or salvinia natans or water hyacinth or azolla or pennywort.

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

10. The method for using the open sewage purification and recycling device according to claim 1, characterized in that, It includes the following steps: Step 1) Lay the bottom sludge deposited for a long time at the bottom of the sewage purification body (5); Step 2) Inject the water to be purified until the water level is slightly higher than the horizontal position of the outlet pipe (2), and then stop injecting; Step 3) Lay the plant varieties described in claim 8 in the plant purification layer (1); Step 4) The water to be purified flows out of the sewage purification body (5) through the outlet pipe (2) and naturally drops into the circulation water tank A (3) for primary drop aeration; Step 5) The water to be purified flows through the arranged U-shaped groove (4), and then naturally drops into the circulation water tank B (9) for secondary drop aeration; Step 6) The water to be purified is lifted from the circulation water tank B (9) to the circulation water tank C (7) through the combination of the lifting pipe (11) and the circulation water pump (10) for tertiary drop aeration; Step 7) The water to be purified in the circulation water tank C (7) flows back to the lower part of the sewage purification body (5) through the down pipe (12) to complete the circulation; Step 8) Repeat steps 1) to 7).

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