Gravel filter bed process design method based on model test

Abstract

The invention discloses a gravel filter bed process design method based on a model test, which is specifically implemented according to the following steps: carrying out water quality monitoring on an application area, and determining a water sample determination index; the method comprises the following steps: acquiring a biological membrane of a gravel filter bed reactor for an indoor test through an in-situ biofilm formation test, and determining filler; establishing a hydrodynamic model of the application area, and determining the flow velocity and flow of a gravel filter bed; biofilm culturing is carried out on the gravel filter bed reactor, the test working condition of the gravel filter bed reactor is determined, a simulation test is carried out, and the concentration and on-way change characteristics of water sample determination indexes are obtained; carrying out an impact resistance test, and determining the maximum flow rate allowed by the gravel filter bed reactor under the condition that the effluent quality reaches the standard; and according to test results, gravel filter bed arrangement types of different river channels are obtained. The method disclosed by the invention has the characteristic of providing a basis for popularization and application of the gravel filter bed in a water environment treatment project.

Description

Technical Field

[0001] The invention belongs to the technical field of hydraulic engineering, and in particular relates to a gravel filter bed process design method based on model tests. Background Art Gravel contact oxidation technology is also known as gravel filter bed technology. It is a rapid way to treat sewage. It is a natural treatment method first designed by WJ Dibden, a sewage treatment engineer in London, England in the 19th century. Its essence is an artificial enhancement of the biofilm growing on the surface of gravel in the natural riverbed.

[0002] The gravel-to-gravel contact oxidation method removes pollutants mainly through multiple effects such as contact precipitation, adsorption, and biodegradation. This method forms a continuous water flow channel between the gravels. When sewage passes through, the suspended solids in the water move to the gravel surface due to precipitation, physical interception, hydrodynamics, etc. and contact precipitation. At the same time, the microorganisms or algae growing on the gravel surface will oxidize and decompose the pollutants they adsorb. The gravel-to-gravel contact oxidation purification system guides the target water body to flow through the treatment tank filled with fillers, so that the sewage contacts and reacts with the biofilm on the surface of the fillers, thereby purifying the water quality.

[0003] As a biological / ecological method for the treatment of polluted water bodies in rivers and lakes, the gravel contact oxidation method has the advantages of being environmentally friendly, ecologically energy-saving and easy to operate and manage. However, it has not yet been promoted on a large scale. The engineering characteristics and applicability of gravel filter beds in natural rivers have not been fully studied and proven. Therefore, it is necessary to establish an experimental model, study the design of gravel filter beds, explore the regular characteristics of gravel filter beds in reducing pollutants, and provide a basis for the actual application of gravel filter beds in designated areas. Summary of the invention

[0004] The purpose of the present invention is to provide a gravel filter bed process design method based on model tests, which can provide a basis for the promotion and application of gravel filter beds in water environment treatment projects.

[0005] The technical solution adopted by the present invention is a gravel filter bed process design method based on model test, which is specifically implemented according to the following steps: Step 1: Monitor water quality in the application area and clarify water sample measurement indicators; Step 2, obtaining the biofilm of the gravel filter bed reactor for indoor testing through an in-situ biofilm test, and determining the filler; Step 3, establish a hydrodynamic model of the application area to determine the velocity and flow rate of the gravel filter bed; Step 4, forming a biofilm on the gravel filter bed reactor, determining the test conditions of the gravel filter bed reactor and conducting a simulation test to obtain the concentration and along-process variation characteristics of the water sample measurement indicators; Step 5, conducting an impact resistance test to determine the maximum flow rate that the gravel filter bed reactor can allow under the condition that the effluent quality meets the standard; Step 6: Obtain the gravel filter bed layout patterns for different river channels based on the test results. The present invention is also characterized in that: In step 1, the time periods for water quality monitoring are summer and winter; Water sample measurement indicators include NO 3 — N, NH 4 + -N, TN, PO 4 3— P, TP, COD.

[0006] The specific process of step 2 is: select fillers with different particle sizes in the application area and put them into multiple stainless steel mesh barrels respectively, and then place the stainless steel mesh barrels in the water body of the application area. After on-site biofilm formation, the biofilm attached to the surface of the filler is peeled off and the biofilm characterization is measured. According to the measurement results, the filler type and particle size are determined.

[0007] The specific process of step 3 is as follows: import the plan of the application area into MIKE21 to establish the river bank line, riverbed depth, gravel filter bed inlet flow, inlet and outlet water level information, build the MIKE 21 FM hydrodynamic model, simulate the water level and flow rate of the water system in the application area through the MIKE 21 FM hydrodynamic model, and then obtain the flow rate of the gravel filter bed through the flow rate and the flow area of ​​the gravel filter bed reactor.

[0008] The specific process of step 4 is: Step 4.1, adding one or more of the fillers specified in step 2, the functional fillers G1, and the functional fillers G2 to multiple gravel filter bed reactors, and running a peristaltic pump to transport water into each gravel filter bed reactor, and adjusting the flow rate of the peristaltic pump to ensure a constant flow rate in each gravel filter bed reactor; Step 4.2, forming a biofilm on the gravel filter bed reactor; Step 4.3, conduct simulation tests with different water qualities, different hydraulic retention times, different aeration volumes, different aeration modes, and different operating days as test conditions, regularly measure the effluent samples of the gravel filter bed reactor, and obtain the concentrations and along-the-process variation characteristics of the water sample measurement indicators under different operating conditions of each gravel filter bed reactor.

[0009] The specific process of step 4.2 is as follows: the biofilm formation in the gravel filter bed reactor includes an intermittent start-up stage and a continuous biofilm formation stage; Intermittent startup stage: the water sample containing sediment collected in the application area is used as inoculation water, and the biofilm peeled off in step 2 is used as the inoculation source. The inoculation water and the inoculation source are mixed evenly and added to the gravel filter bed reactor for aeration for several days. Aeration is carried out once in the morning, noon and evening every day. The water quality of the gravel filter bed reactor at different aeration days is measured respectively. After the aeration is completed on the last day, all the inoculation water is discharged from the gravel filter bed reactor, and then the inoculation water and the inoculation source of the same volume as the discharged inoculation water are added to the gravel filter bed reactor again, and the above process is repeated; Continuous biofilm formation stage: After all the inoculated water is discharged for the last time, a peristaltic pump is used to continuously add artificial water until biofilm formation is successful.

[0010] In step 5, the impact resistance test is achieved by increasing the water flow rate and reducing the hydraulic retention time.

[0011] In step 6, the gravel filter bed layout types for different river channels include: The first type: For rivers that need to undertake flood discharge tasks, a separated gravel filter bed layout is adopted, that is, the gravel filter bed is arranged outside the flood discharge area of ​​the river, and part of the water in the river is introduced into the gravel filter bed for treatment, and then returned to the river downstream; The second type: For rivers that do not need to bear the task of flood discharge, the gravel filter bed is directly arranged in the river channel, so that all the river water flows through the gravel filter bed for full-scale treatment, or part of the water overflows from the upper part of the gravel filter bed, and part of the water enters the gravel filter bed for treatment.

[0012] For the first case: according to the water diversion method, it is divided into a separated gravel filter bed with no dam diversion and a separated gravel filter bed with dam diversion; Among them, the separated gravel filter bed for damless water diversion includes a water diversion channel arranged on one side of the river channel, a waterfall across the river channel is arranged in the river channel upstream of the water inlet channel, and a sand barrier, a trash rack, and a gate are arranged in sequence at the inlet of the water inlet channel. The sand barrier is arranged at the entrance where the water diversion channel connects with the river channel and is connected to the side wall of the water diversion channel. The trash rack is arranged downstream of the sand barrier, and both sides of the trash rack are connected to the side wall of the water diversion channel. The gate is arranged downstream of the trash rack, and the gate is connected to the bottom plate and side wall of the water diversion channel. A gravel filter bed is arranged at the outlet of the water inlet channel, and the gravel filter bed is filled with fillers. The bottom of the gravel filter bed is connected to the downstream of the river channel through the outlet channel; Among them, the separated gravel filter bed with dam water diversion includes a water diversion channel arranged on one side of the river channel, a waterfall across the river channel is arranged in the river channel upstream of the water inlet channel, a water dam across the river channel is arranged in the river channel upstream of the water inlet channel, and a sand retaining bank, a trash rack and a gate are arranged in sequence at the inlet of the water inlet channel. The sand retaining bank is arranged at the entrance where the water diversion channel connects with the river channel and is connected to the side wall of the water diversion channel. The trash rack is arranged downstream of the sand retaining bank, and the two sides of the trash rack are connected to the side wall of the water diversion channel. The gate is arranged downstream of the trash rack, and the gate is connected to the bottom plate and side wall of the water diversion channel. A gravel filter bed is arranged at the outlet of the water inlet channel, the gravel filter bed is filled with fillers, and the bottom of the gravel filter bed is connected to the downstream of the river channel through the outlet channel.

[0013] For the second case: including the gravel filter bed directly arranged horizontally in the river channel and the gravel filter bed directly arranged vertically in the river channel; The structure in which the gravel filter bed is directly arranged transversely in the river channel is specifically as follows: a grit chamber, a waterfall, and a gravel filter bed are sequentially arranged in the river channel and along the direction of water flow; a drainage channel is arranged on one side of the grit chamber near the waterfall and close to the river bank; the drainage channel is arranged along the direction of river water flow and the length of the drainage channel is not less than the distance from the water outlet side of the grit chamber to the water outlet side of the gravel filter bed; one end of the gravel filter bed is connected to the inner side wall of the river channel, and the other end of the gravel filter bed is connected to the side wall of the drainage channel; Among them, the structure in which the gravel filter bed is directly arranged longitudinally in the river channel is specifically as follows: a sand settling tank, a waterfall, and a gravel filter bed are arranged in sequence in the river channel and along the direction of water flow, a plurality of drainage gates are arranged on the gravel filter bed along the direction of water flow, and the width of the gravel filter bed is smaller than the width of the river channel and is arranged along the direction of water flow in the river channel.

[0014] The beneficial effects of the present invention are as follows: the gravel filter bed process design method of the present invention is based on model tests, starting from the analysis of water quality, biofilm types and applicable fillers in the gravel filter bed application area, by establishing a gravel filter bed water flow model in the application area, conducting continuous indoor tests under different working conditions, monitoring changes in pollutant concentrations, analyzing the operating characteristics of the gravel filter bed reactor under different working conditions, and based on the test results, proposing gravel filter bed layout types for use in different river channels, thereby providing a basis for the promotion and application of gravel filter beds in water environment governance projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic diagram of a gravel filter bed reactor in the method of the present invention; Figure 2 The change of nitrogen concentration in the inoculated mixed solution during the intermittent startup period in the method of the present invention; Figure 3 The change of phosphorus concentration in the inoculated mixed solution during the intermittent startup period in the method of the present invention; Figure 4 is the change of nitrogen concentration in each gravel filter bed reactor during the continuous biofilm formation in the method of the present invention; Figure 5 The PO in the inlet and outlet water of each gravel filter bed reactor during the continuous biofilm formation in the method of the present invention is 4 3 --Temporal changes in P concentration; Figure 6 is the time-dependent change of nitrogen removal rate of different gravel filter bed reactors under different winter water quality conditions in the method of the present invention; Figure 7 is the change of nitrogen concentration in inlet and outlet water of different gravel filter bed reactors under different water quality conditions in winter in the method of the present invention; Figure 8 The phosphorus concentration and removal rate of the inlet and outlet water of different gravel filter bed reactors under different winter water quality conditions in the method of the present invention are changed over time; Fig. 9 is the mean value of phosphate concentration and removal rate of different gravel filter bed reactors under different winter water quality conditions in the method of the present invention; Fig.10 The change of nitrogen concentration in the inlet and outlet water of different gravel filter bed reactors under different water quality conditions in summer in the method of the present invention; Fig.11 is the time-dependent change of nitrogen removal rate of different gravel filter bed reactors under different water quality conditions in summer in the method of the present invention; Fig.12 is the average nitrogen concentration of inlet and outlet water of different gravel filter bed reactors under different water quality conditions in summer in the method of the present invention; Fig.13 is the average nitrogen removal rate of different gravel filter bed reactors under different water quality conditions in summer in the method of the present invention; Fig.14 is the average phosphate concentration and removal rate of different gravel filter bed reactors under different water quality conditions in summer in the method of the present invention Fig.15 The TN concentration changes along the process in each gravel filter bed reactor under different water quality conditions in winter in the method of the present invention; Fig.16 The TN concentration changes along the process in each gravel filter bed reactor under different water quality conditions in summer in the method of the present invention; Fig.17 is the change of nitrogen over time in the impact resistance test in the method of the present invention; Fig.18 is the average nitrogen concentration of the effluent water from the impact resistance test in the method of the present invention; Fig.19 The time-dependent change of phosphate in the impact resistance test in the method of the present invention; Fig. 20 is the average phosphate concentration of the effluent from the impact resistance test in the method of the present invention; Fig.21 It is a plan layout diagram of a damless water diversion separation type gravel filter bed in the method of the present invention; Fig. 22 It is a plan view of the dam-type water diversion separation gravel filter bed in the method of the present invention; Fig.23 It is a plan view of the direct transverse gravel filter bed in the method of the present invention; Fig.24 This is a plan view of the direct longitudinal gravel filter bed in the method of the present invention.

[0016] In the figure, 1. waterfall, 2. sand retaining bank, 3. trash rack, 4. gate, 5. water diversion channel, 6. gravel filter bed, 7. outlet channel, 8. dam, 9. grit chamber, 10. drainage channel, 11. drainage gate, 12. gravel filter bed reactor. DETAILED DESCRIPTION The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] Example 1 The gravel filter bed process design method based on the model test of the present invention is specifically implemented according to the following steps: Step 1: Monitor water quality in the application area and clarify water sample measurement indicators; Step 2, obtaining the biofilm of the gravel filter bed reactor for indoor testing through an in-situ biofilm test, and determining the filler; Step 3, establish a hydrodynamic model of the application area to determine the velocity and flow rate of the gravel filter bed; Step 4, forming a biofilm on the gravel filter bed reactor, determining the test conditions of the gravel filter bed reactor and conducting a simulation test to obtain the concentration and along-process variation characteristics of the water sample measurement indicators; Step 5, conducting an impact resistance test to determine the maximum flow rate that the gravel filter bed reactor can allow under the condition that the effluent quality meets the standard; Step 6: Obtain the gravel filter bed layout patterns for different river channels based on the test results.

[0018] In this embodiment, based on water quality monitoring, in-situ biofilm test, hydrodynamic model and simulation of different working conditions, the water quality, flow rate, flow rate and other parameters of the gravel filter bed reactor are determined, and continuous indoor tests and impact resistance tests of the gravel filter bed reactor are carried out. The effects of aeration, functional fillers, gas-water ratio and other factors on pollutant removal, as well as the changes in pollutant concentration along the reactor are analyzed to provide a basis for the application of gravel filter beds.

[0019] Example 2 Based on Example 1, water quality monitoring is carried out in the application area. Through on-site investigation of the application area, the pollution characteristics of river and lake water bodies are understood, the water quality characteristics of unpurified river and lake water bodies are mastered, and the water quality, pollutant types and pollutant concentration range of the water body to be entered into the gravel filter bed are determined, that is, the water sample measurement indicators, including NO 3- -N, NH 4 + -N, TN (total nitrogen), PO 4 3- -P, TP (total phosphorus), COD (chemical oxygen demand), NO 2 - -N.

[0020] In order to make the water samples more representative and reasonably reflect the water quality in the application area, different points were selected in summer and winter to randomly collect water samples, and the types and concentrations of pollutants in the water were measured and analyzed. See Table 1 and Table 2 for details.

[0021] Table 1 Water quality in different locations in summer (July to August)

[0022] Note: Except for T which is in °C, all others are in mg / L.

[0023] Table 2 Water quality in different locations in winter (October to December)

[0024] Note: Except for T which is in °C, all others are in mg / L.

[0025] It can be seen from Table 1 and Table 2 that there are certain differences in water quality in summer and winter.

[0026] Based on the above differences, the influent water of the gravel filter bed reactor in subsequent tests was divided into summer and winter influent water qualities for separate tests. The summer and winter influent water qualities used in the tests are shown in Table 3.

[0027] Table 3 Test water quality in winter and summer

[0028] Example 3 On the basis of Example 2, the specific process of step 2 is: select fillers with different particle sizes in the application area and put them into 10 stainless steel mesh barrels respectively, and then place the stainless steel mesh barrels in the water body of the application area. After on-site biofilm formation, the biofilm attached to the surface of the filler is peeled off, and the biofilm is characterized and measured. According to the measurement results, the filler type and particle size are determined.

[0029] The fillers include 3cm gravel, 5cm gravel, 3cm pebbles, 5cm pebbles and 10cm pebbles, a total of 5 types of fillers; the height of the stainless steel grid bucket is 32cm, the diameter is 20cm, and the grid aperture is 2cm×2cm; two stainless steel grid buckets are used for each filler to carry out in-situ biofilm test.

[0030] All fillers must be cleaned before being placed in the stainless steel mesh barrel. Then use a 10L plastic measuring cup to measure the porosity and specific surface area of ​​stones of different particle sizes, and make records and calculations. After the calculation is completed, the fillers are placed in the stainless steel mesh barrel for on-site installation. When hanging, ensure that the bottom of the stainless steel mesh barrel is 20cm away from the riverbed.

[0031] After the biofilm formation is completed, other impurities attached to the surface of the filler are removed, and then multiple fillers are selected from different positions of the same stainless steel grid barrel as the objects for peeling off the biofilm. The biofilm on the selected fillers is peeled off one by one with a hard brush, and the peeled biofilm is collected for subsequent determination; the following indicators are measured for the collected biofilm: the total amount of biofilm, high-throughput sequencing of microorganisms in the biofilm, where the total amount of biofilm is characterized by total SS (biofilm dry weight) and total VSS (biofilm volatile dry weight). The specific results are shown in Table 4.

[0032] Table 4 Total amount of biofilm exfoliated with different particle sizes

[0033] It can be seen from Table 4 that among the same type of fillers, the amount of biofilm attached to the fillers with a particle size of 3 cm is greater than that of the fillers with a particle size of 5 cm, while among different types, the same volume of crushed stone has more biofilm attached to it than pebbles. Finally, 3 cm crushed stone was selected as the filler for the gravel filter bed reactor in this embodiment.

[0034] Through high-throughput analysis of biofilm formation tests, it was found that actual water bodies contain a variety of microorganisms with different functions, which have sufficient potential to degrade pollutants. Therefore, it was determined that actual on-site water samples were selected as the inoculation source when starting biofilm formation in the laboratory gravel filter bed reactor to promote rapid biofilm formation in the gravel filter bed reactor while ensuring the similarity of species in the biofilm.

[0035] Example 4 On the basis of Example 3, the specific process of step 3 is: importing the plan view of the application area into MIKE21 to establish the river bank line, riverbed water depth, gravel filter bed inlet flow, inlet and outlet water level information, building a MIKE 21 FM hydrodynamic model, simulating the water level and flow velocity of the water system in the application area through the MIKE 21 FM hydrodynamic model, and then obtaining the flow rate of the gravel filter bed through the flow velocity and the flow area of ​​the gravel filter bed reactor.

[0036] The velocity and flow rate results simulated by the MIKE 21 FM hydrodynamic model provide data support for the subsequent gravel filter bed reactor design and biofilm test.

[0037] Example 5 Based on Example 4, the specific process of step 4 is as follows: Step 4.1, adding one or more of 3 cm crushed stone, functional filler G1, and functional filler G2 to four gravel filter bed reactors respectively, and running a four-channel constant flow peristaltic pump to transport water into each gravel filter bed reactor, and adjusting the flow rate of the peristaltic pump to ensure a constant flow rate in each gravel filter bed reactor; Specifically, Figure 1 As shown, the gravel filter bed reactor 12 is columnar, and a plurality of water outlets are arranged at equal intervals on its side wall along the water flow direction, and a water outlet is arranged at its bottom. All water outlets are provided with valves. The fillers added to the four gravel filter bed reactors (respectively denoted as 1#, 2#, 3#, and 4#) are: 100% gravel for 1#, 67.7% gravel + 32.3% zeolite for 2# (gravel at the bottom, zeolite at the top), 67.7% gravel + 32.3% zeolite for 3# (gravel at the bottom, zeolite at the top), and 100% gravel + 32.3% zeolite for 1#. Volcanic rock (crushed stone at the bottom, volcanic rock at the top), 4# is 67.7% crushed stone + 16.1% zeolite + 16.2% volcanic rock (crushed stone at the bottom, zeolite in the middle, volcanic rock at the top); each channel of the four-channel peristaltic pump corresponds to a gravel filter bed reactor, and the four-channel constant flow peristaltic pump is used to transport water to each gravel filter bed reactor, and the peristaltic pump flow rate is adjusted according to the cross-sectional area of ​​the gravel filter bed reactor to ensure a constant flow rate in the gravel filter bed reactor filler; Step 4.2, forming a biofilm on the gravel filter bed reactor; The biofilm formation in the gravel filter bed reactor includes an intermittent start-up phase and a continuous biofilm formation phase. Intermittent startup stage: The water sample containing sediment collected in the application area is used as inoculation water (the inoculation water is 50L), and the biofilm peeled off in step 2 is used as the inoculation bacteria source. The inoculation water and the inoculation bacteria source are mixed evenly (the inoculation mixture is obtained after mixing) and added to the gravel filter bed reactor for aeration for 6 days. Aeration is carried out once in the morning, noon and evening every day. The water quality in the gravel filter bed reactor is measured on the 0th day, the 3rd day and the 6th day respectively. After the end of the 6th day, all the inoculation water is discharged from the gravel filter bed reactor, and then the inoculation water and the inoculation bacteria source with the same volume as the discharged inoculation water are added to the gravel filter bed reactor again, and the above process is repeated; Continuous biofilm formation stage: After all the inoculated water is discharged for the last time, artificial water is continuously added using a peristaltic pump and the process is continued under the condition of a hydraulic retention time of 12 hours until biofilm formation is successful; The inoculation mixture and artificial water distribution used for biofilm formation are shown in Table 5; Table 5 Water used for biofilm test

[0038] like Figure 2As shown, the TN concentration changes in the 1#, 2#, 3# and 4# gravel filter bed reactors were consistent during the intermittent startup phase, and decreased over time in each cycle. However, compared with other gravel filter bed reactors, the 1# gravel filter bed reactor decreased the slowest, indicating that the addition of functional fillers contributed more to the reduction of total nitrogen concentration in the water at the initial biofilm formation stage; the ammonia nitrogen concentration in all gravel filter bed reactors showed a downward trend, but compared with the 1# gravel filter bed reactor, the ammonia nitrogen concentration in the 2#, 3# and 4# gravel filter bed reactors decreased faster, indicating that the addition of functional fillers had a certain promoting effect on the reduction of ammonia nitrogen concentration in the water at the initial biofilm formation stage, and also indicated that nitrification occurred in the gravel filter bed reactor; the nitrate nitrogen concentration in the four gravel filter bed reactors showed a downward trend, and the nitrite nitrogen concentration decreased to a certain extent, indicating that nitrification and denitrification reactions occurred in the gravel filter bed reactors. In short, after 12 days of intermittent startup, a certain amount of microbial strains related to nitrogen removal had been inoculated in the gravel filter bed reactor; like Figure 3 As shown, in the first and second cycles of the intermittent start-up period, regardless of PO 4 3- -P and TP concentrations all showed a significant decrease, and the decrease was most obvious in reactors 2# and 3#, followed by reactor 4#, while reactor 1# decreased less. Therefore, it can be considered that the decrease in phosphorus concentration in the water at the initial start-up is closely related to the adsorption of the functional filler itself; Continuous biofilm formation stage: Figure 4 As shown in the figure, the TN concentrations of the effluents from the 1#, 2#, 3# and 4# gravel filter bed reactors were 6.32±0.49 mg / L, 5.34±0.30 mg / L, 6.68±0.49 mg / L and 5.92±0.45 mg / L, respectively. It can be seen that the 2# gravel filter bed reactor has the best TN removal effect, followed by the 4# gravel filter bed reactor. The 2# gravel filter bed reactor and the 4# gravel filter bed reactor were filled with 32% and 16% zeolite, respectively, which indicates that the adsorption of zeolite fillers played a certain role in TN removal during the continuous biofilm formation period. The largest contribution to TN removal during the continuous biofilm formation period was NH 4+ -N removal, NH in the effluent of 1#, 2#, 3# and 4# gravel filter bed reactors in the stabilization stage 4+ -N concentrations were 5.69±0.55, 5.23±0.30, 6.05±0.65 and 5.47±0.43 mg / L, respectively. Therefore, it can be considered that the zeolite filler has a significant effect on NH 4+ The adsorption of -N directly leads to the increase of TN removal rate. In the first 12 days of continuous biofilm formation, the effluent NO 3- -N concentration gradually decreased and then stabilized. In the stable stage, NO 3 --N concentrations were 0.06 mg / L, 0.06 mg / L, 0.04 mg / L and 0.07 mg / L respectively, indicating that the denitrifying bacteria in the reactor played a certain role. However, due to oxygen limitation, the role of nitrifying bacteria was limited. Therefore, the nitrification effect was very weak in the initial stage. The nitrite nitrogen (NO 2 - -N) concentrations were basically below 0.2 mg / L. In short, after 12 days of continuous biofilm formation, the gravel filter bed reactor gradually entered a stable stage. During the stable period, each reactor removed nitrogen to a certain extent under the action of microorganisms, but due to the low DO concentration in the gravel filter bed reactor, the biological removal of nitrogen was limited. The adsorption of nitrogen by the functional filler zeolite in the early stage of biofilm formation was the main reason for the difference in nitrogen concentration in the effluent of each gravel filter bed reactor.

[0039] like Figure 5 As shown in the figure, in the initial stage of continuous biofilm formation, the removal effects of the gravel filter bed reactors on the phosphate concentration in the water were quite different, which was mainly attributed to the physical adsorption of the functional fillers. After 20 days, the phosphate concentration of the effluent from each gravel filter bed reactor gradually increased, and the removal effect began to decline, but the phosphate concentration of the effluent from the 3# gravel filter bed reactor and the 4# gravel filter bed reactor was relatively low, indicating that the adsorption effect of the functional filler volcanic rock on phosphorus in the gravel filter bed reactor was more obvious in the biofilm formation stage.

[0040] Step 4.3, conducting simulation tests on four gravel filter bed reactors with different water qualities, different hydraulic retention times, different aeration volumes, different aeration modes, and different operating days as test conditions, regularly measuring effluent water samples of the gravel filter bed reactors, and obtaining the concentration and along-process variation characteristics of water sample measurement indicators under different working conditions of each gravel filter bed reactor, thereby obtaining the working condition with the best concentration and along-process variation effects of water sample measurement indicators; The specific test conditions are shown in Table 6, where the winter water quality and summer water quality adopt the water quality recorded in Table 3; Table 6 Continuous test conditions of gravel filter bed reactor

[0041] During the test, the effluent samples of the gravel filter bed reactor were collected every 3 days, and water samples along the process were collected when the working conditions were stable. All water samples were tested for the following conventional indicators, including TN, NH 4 + -N, NO 3 - -N, NO 2 - -N,PO 4 3- -P.

[0042] For winter water quality, the nitrogen concentration trends among the gravel filter bed reactors under the same operating conditions are similar, but there are obvious differences in nitrogen concentration under different operating conditions. Figure 6 As shown in the figure, during the test, the influent TN and NH 4 + -N and NO 3 - The concentration ranges of -N were 10.03 mg / L ~11.11 mg / L, 7.64 mg / L ~8.76 mg / L and 1.93 mg / L ~2.71 mg / L, and the corresponding average concentrations were 10.67 mg / L, 8.14 mg / L and 2.37 mg / L, respectively. 4 + The mean concentrations of -N were 5.96 mg / L, 5.02 mg / L, 6.35 mg / L and 5.63 mg / L under condition 1, 0.42 mg / L, 0.42 mg / L, 0.08 mg / L and 0.16 mg / L under condition 2, 3.34 mg / L, 2.92 mg / L, 3.12 mg / L and 2.93 mg / L under condition 3, and 2.07 mg / L, 2.16 mg / L, 2.24 mg / L and 2.19 mg / L under condition 4. 4 + The removal rate of -N with aeration is significantly higher than that without aeration. It can also be seen that under condition 2, NH 4 + -N removal rate can reach up to 100%. 3 - -N removal rate and NH 4 + -N removal rate showed an opposite trend, with NO in the effluents of reactors 1#, 2#, 3# and 4# 3 - The mean values ​​of -N concentrations were 0.07 mg / L, 0.01 mg / L, 0.01 mg / L and 0.06 mg / L in condition 1; 7.41 mg / L, 8.25 mg / L, 8.16 mg / L and 8.67 mg / L in condition 2; 1.35 mg / L, 0.46 mg / L, 1.37 mg / L and 1.30 mg / L in condition 3; and 3.05 mg / L, 3.02 mg / L, 3.04 mg / L and 3.24 mg / L in condition 4. It can be seen that with the increase of aeration volume, the effluent NO 3 - -N concentration increases, and under condition 1 without aeration, the nitrate-nitrogen removal rate can reach 100%.

[0043] like Figure 7 As shown, for winter water quality, aeration will significantly affect the conversion of nitrogen by the gravel filter bed reactor, thereby affecting the concentration of different forms of nitrogen in the effluent. Under the condition of sufficient oxygen supply, the gravel filter bed reactor is capable of removing 100% of ammonia nitrogen, while under the condition of no oxygen supply, the gravel filter bed reactor is capable of removing 100% of nitrate nitrogen. Therefore, in order to remove TN to the maximum extent, the appropriate aeration condition is to maximize the removal of TN. In this embodiment, when the air-water ratio is 1:3 under continuous aeration conditions, the TN removal rate of the winter influent water quality can reach a maximum of 69.1%, that is, operating condition 3 is the optimal operating condition.

[0044] like Figure 8 As shown in the figure, for winter water quality, the phosphorus concentration change trends among the gravel filter bed reactors are similar, but there are certain differences in the removal effect of phosphorus concentration, and there are certain differences in the change of phosphorus concentration under different working conditions. During the test, the average phosphate concentration of the effluent of reactors 1#, 2#, 3# and 4# was 0.53 mg / L, 0.53 mg / L, 0.52 mg / L and 0.55 mg / L in working condition 1; 0.53 mg / L, 0.54 mg / L, 0.49 mg / L and 0.54 mg / L in working condition 2; 0.51 mg / L, 0.52 mg / L, 0.45 mg / L and 0.50 mg / L in working condition 3 and 0.53 mg / L, 0.51 mg / L, 0.53 mg / L and 0.53 mg / L in working condition 4. The data show that, except for operating condition 3, the average phosphorus concentration of the effluent of the same gravel filter bed reactor under other operating conditions is not much different. Among different gravel filter bed reactors, the 3# gravel filter bed reactor has the highest removal rate, which can reach up to 46.7%. Fig. 9 This can be seen more intuitively. This may be related to the adsorption of functional fillers, and is also affected by the microbial action related to phosphorus removal in the reactor.

[0045] For summer water quality, the time course changes of nitrogen concentrations in the inlet and outlet water of different reactors under different aeration conditions are as follows: Fig.10 As shown, the corresponding nitrogen removal rate changes over time as shown Fig.11 As shown in Figure 2, the mean nitrogen concentration and average nitrogen removal rate of different reactors under different aeration conditions are shown in Figure 2. Fig.12 and 13 As shown in the figures, the gravel filter bed reactors under various working conditions have a certain removal effect on nitrogen in the influent, and the nitrogen removal effects of the gravel filter bed reactors are similar, but there are obvious differences in nitrogen concentrations between different working conditions.

[0046] For summer water quality, under conditions IV, V and VI, the effluent TN concentration was less than 2 mg / L, meeting the surface water V water quality requirements. Under continuous aeration conditions, the effluent TN concentration of each reactor was the lowest under condition IV, and the removal rate was up to 70.53%; under intermittent aeration conditions, the effluent TN concentration of each reactor under condition V was further reduced, and the removal rate was up to 76.37%. Except for condition I, the effluent NH 4 + -N concentrations were all lower than 1.5 mg / L, meeting the surface water quality requirements of Class IV. There was almost no NH in the effluent under conditions II and III. 4 + -N, the removal rate can reach the highest value, up to 100%, meeting the water quality requirements of Class I surface water. At the same time, NH 4 + -N concentration under aeration conditions was significantly lower than that under no aeration conditions, and with the increase of aeration volume, the effluent NH 4 + -N concentration is lower. Under the same aeration rate, the effluent NH 4 + -N concentration was slightly higher than that under continuous aeration conditions.

[0047] For summer water quality, aeration can significantly affect the removal of nitrogen from the influent by the gravel filter bed reactor. Given the right conditions, the gravel filter bed reactor is capable of removing 100% of the NH 4 + -N or NO 3 - -N. In this experiment, under continuous aeration conditions, it is impossible to simultaneously meet the requirements of NH 4 + -N or NO 3 - When 100% removal of -N is achieved, the aeration conditions can only be controlled as much as possible to make both reach a higher value, that is, continuous aeration and an air-to-water ratio of 1:3 are the best conditions.

[0048] PO of different gravel filter bed reactors under different aeration conditions 4 3- -P concentration mean and removal rate mean Fig.14 As shown in the figure, the PO between each gravel filter bed reactor 4 3- -P concentration changes were similar, but for PO 4 3- -P concentration removal effect has certain differences, and different working conditions have different 4 3- There are also some differences in the removal effect of -P concentration.4 3- -P concentration average is lower than 0.3mg / L; effluent PO under conditions IV, V and VI 4 3- The average concentration of -P was lower than 0.2 mg / L. 4 3- The removal rate of -P increased slightly, indicating that the microbial activity related to phosphorus removal in the gravel filter bed reactor gradually increased.

[0049] In summary, the removal effects of various pollutants among the gravel filter bed reactors under different aeration conditions of influent water quality are slightly different. Therefore, the experiment further understands the main functional areas inside the gravel filter bed reactor through the changes of pollutants along the process in each gravel filter bed reactor, and compares the changes along the process between different gravel filter bed reactors.

[0050] The changes of TN concentration in each gravel filter bed reactor under different working conditions during winter and summer water inflow are as follows: Fig.15 and 16 As shown in the figure, by calculating the change of TN concentration in each gravel filter bed reactor along the process, it can be seen that the average proportion of TN concentration removed in the first 20 cm of the gravel filter bed reactor to the TN concentration removed in the whole reactor under conditions 1, 2, 3 and 4 reached more than 86%. From the data, it can be found that the proportion of TN concentration removed within the first 35 cm of each gravel filter bed reactor under different conditions to the overall TN removal concentration is all above 80.0%, and even in most cases it can reach more than 90.0%, which is mainly the result of the action of a large number of microorganisms enriched in the front section.

[0051] Example 6 On the basis of Example 5, the impact resistance test was carried out by increasing the water flow rate and reducing the hydraulic retention time to study the effect of hydraulic impact caused by runoff during heavy rain on GBF (gravel filter bed).

[0052] The water used for the impact resistance test is prepared according to the summer water quality recorded in Table 3.

[0053] The main purpose of the impact test is to explore the maximum value of the flow rate in the gravel filter bed reactor while ensuring that the effluent quality meets the standard. In view of the large water consumption and the small differences between the gravel filter bed reactors, this test only uses the 1# gravel filter bed reactor (100% gravel) as the research object. The specific impact test conditions are shown in Table 7. The impact test is used to obtain the optimal conditions under the condition of maximum flow rate in the gravel filter bed reactor; Table 7 Impact resistance test conditions

[0054] During the impact test, the nitrogen changes under different hydraulic retention times are as follows: Fig.17 As shown in Figure 2, the average nitrogen concentration of effluent under different working conditions is as follows: Fig.18 As the HRT (hydraulic retention time) decreases, the TN and NH in the effluent of the gravel filter bed reactor decrease. 4 + -N concentration showed an overall upward trend. When HRT≤1.5h, the effluent TN concentration significantly exceeded the surface water Class V water standard, but the effluent NH 4 + -N concentration can still reach the surface water Class V water standard. Therefore, when it is necessary to ensure that the effluent nitrogen concentration meets the treatment requirements, the HRT cannot be lower than 1.5h, and the corresponding internal flow rate of the GBF reactor is 1.72×10-4m / s.

[0055] During the impact test, the phosphate changes under different hydraulic retention times are as follows: Fig.19 As shown in Figure 2, the average phosphate concentration of the effluent under different working conditions is as follows: Fig. 20 As shown in Figure 2, as the HRT (hydraulic retention time) decreases, the PO 4 3- -P concentration showed a downward trend overall, which was mainly related to the large-scale enrichment of microorganisms related to phosphorus removal. Combined with the previous continuous operation test, it can be seen that when a sufficient amount of microorganisms are enriched in the gravel filter bed reactor, the PO 4 3- -P has a relatively continuous and stable removal effect, which can improve its concentration to Class III surface water quality, but the removal rate is still low, not exceeding 68.6%.

[0056] Example 7 Based on the changes in filler type, filler particle size, gravel filter bed velocity, gravel filter bed flow, hydraulic retention time, aeration, and pollutants (water sample measurement indicators) along the way, a comprehensive consideration is given, that is, the gravel filter bed layout type suitable for different rivers in the application area with the most comprehensive operating conditions is selected.

[0057] Based on the above continuous tests, increasing aeration has a good effect on the removal of nitrogen and COD in water. Therefore, in this embodiment, the gravel filter bed is arranged with aeration conditions, and aeration facilities are considered; if artificial aeration is used, it is necessary to lay pipelines or place equipment, and power supply facilities are required. In order to reduce operation and maintenance costs and simplify the operation mode, the aeration form is proposed to adopt natural waterfalls that do not require power, or waterfall weirs.

[0058] Depending on whether they undertake flood-carrying tasks, rivers can be divided into two categories: one is flood control rivers that need to undertake flood-carrying tasks, and the other is landscape rivers that do not need to undertake flood-carrying tasks.

[0059] Rivers that need to undertake flood discharge tasks generally have the following characteristics: (1) There is a large difference in flow between the dry season and the flood season; (2) The flow rate of the river during the flood season is large and the flow rate is fast; (3) The amount of sediment in the river increases during flood discharge. Since this type of river undertakes the task of flood discharge, firstly, according to water conservancy requirements, buildings that affect flood discharge cannot be arranged in the river; secondly, the flow rate during the flood season is large, and it is impossible to introduce all the water into the gravel filter bed for treatment. Therefore, this type of river is suitable for the use of a separated gravel filter bed arrangement, that is, the gravel filter bed is arranged outside the flood discharge area of ​​the river, and part of the water in the river is introduced into the gravel filter bed for treatment, and then returned to the river downstream.

[0060] According to the water diversion method, it is divided into a separated gravel filter bed with no dam diversion and a separated gravel filter bed with dam diversion; Among them, Fig.21 As shown, the separated gravel filter bed for damless water diversion includes a water diversion channel 5 arranged on one side of the river channel, a waterfall 1 across the river channel is arranged in the river channel upstream of the water inlet channel 5, and a sand retaining bank 2, a trash rack 3, and a gate 4 are arranged in sequence at the inlet of the water inlet channel 5. The sand retaining bank 2 is arranged at the entrance where the water diversion channel 5 is connected to the river channel and is connected to the side wall of the water diversion channel 5. The trash rack 3 is arranged downstream of the sand retaining bank 2, and both sides of the trash rack 3 are connected to the side wall of the water diversion channel 5. The gate 4 is arranged downstream of the trash rack 3, and the gate 4 is connected to the bottom plate and side wall of the water diversion channel 5. A gravel filter bed 6 is arranged at the outlet of the water inlet channel 5, and the gravel filter bed 6 is filled with fillers. The bottom of the gravel filter bed 6 is connected to the downstream of the river channel through the outlet channel 7; if the longitudinal slope of the river channel is steep, the waterfall can be arranged naturally by utilizing the river channel drop; if the longitudinal slope of the river channel is gentle, a concrete or stone weir can be set to form a waterfall after the water level is raised.

[0061] Among them, Fig. 22 As shown, for a river with a small flow rate in the dry season and a large difference in elevation between the water surface and the bank, the separated gravel filter bed with dam water diversion can be used to raise the water level through a weir gate, and then water is diverted into the gravel filter bed on the upstream side of the weir gate. Specifically, it includes a water diversion channel 5 arranged on one side of the river, a waterfall 5 across the river is arranged in the river upstream of the water inlet channel 5, a water dam 8 across the river is arranged in the river upstream of the water inlet channel 5, and a sand barrier 2, a trash rack 3, a gate are arranged in sequence at the inlet of the water inlet channel 5. The gate 4 and the sand barrier 2 are arranged at the entrance where the water diversion channel 5 is connected to the river channel and are connected to the side wall of the water diversion channel 5. The trash rack 3 is arranged downstream of the sand barrier 2. Both sides of the trash rack 3 are connected to the side wall of the water diversion channel 5. The gate 4 is arranged downstream of the trash rack 3. The gate 4 is connected to the bottom plate and side wall of the water diversion channel 5. The outlet of the water inlet channel 5 is provided with a gravel filter bed 6 filled with fillers. The bottom of the gravel filter bed 6 is connected to the downstream of the river channel through the outlet channel 7. If the longitudinal slope of the river channel is steep, the waterfall can be arranged naturally by using the river channel drop; if the longitudinal slope of the river channel is gentle, a concrete or stone weir can be set to form a waterfall after the water level is raised.

[0062] For landscape rivers that do not carry flood water, the river has a stable water supply, a small flow, and a low sediment content. Therefore, the gravel filter bed can be directly arranged in the river, so that all the river water flows through the gravel filter bed for full quantitative treatment, or part of the water overflows from the upper part of the gravel bed, and part of the water enters the gravel bed for treatment.

[0063] It includes gravel filter bed arranged directly in the river channel horizontally and gravel filter bed arranged directly in the river channel vertically; Among them, Fig.23 As shown, when the width of the landscape river channel is small, the gravel filter bed can be directly arranged in the river channel horizontally. The structure of the gravel filter bed directly arranged in the river channel horizontally is specifically as follows: a grit chamber 9, a waterfall 1, and a gravel filter bed 6 are sequentially arranged in the river channel and along the direction of water flow; a drainage channel 10 is arranged on one side of the grit chamber 9 near the waterfall 1 and near the river bank; a gate 4 is arranged at the inlet of the drainage channel 10; the drainage channel 10 is arranged along the direction of water flow in the river channel and its length is not less than the distance from the outlet side of the grit chamber 9 to the outlet side of the gravel filter bed 6; One end of the bed 6 is connected to the inner wall of the river channel, and the other end of the gravel filter bed 6 is connected to the side wall of the drainage channel 10; in order to reduce the sediment in the river channel entering the downstream gravel filter bed, the direct gravel filter bed is first arranged with a grit chamber upstream. Considering that the gravel filter bed cannot be arranged too high when it is directly arranged in the river channel, and in order to cooperate with the upstream sand settling, the waterfall of this scheme adopts a concrete or stone weir, and the water level is raised to form a waterfall. In order to meet the requirements of the grit chamber and the filter bed for maintenance and emptying, a drainage channel is arranged on the shore side, and a gate is arranged at the inlet of the drainage channel.

[0064] Among them, Fig.24 As shown, the width of the landscape river channel is relatively large. The gravel filter bed can be arranged longitudinally in the river channel in combination with the landscape. The structure of the gravel filter bed arranged longitudinally in the river channel is specifically as follows: a grit chamber 9, a waterfall 1, and a gravel filter bed 6 are arranged in sequence in the river channel and along the direction of water flow. The gravel filter bed 6 is provided with a number of drainage gates 11 along the direction of water flow. The width of the gravel filter bed 6 is less than the width of the river channel and is arranged along the direction of water flow in the river channel. In order to reduce the amount of sediment in the river channel entering the downstream gravel filter bed, the direct gravel filter bed is first arranged with a grit chamber upstream. The bottom of the grit chamber should be 0.5m to 1m lower than the riverbed and the length is 10m to 20m. Considering that the gravel filter bed cannot be arranged too high when it is directly arranged in the river channel, and in conjunction with the upstream sand settling, the waterfall of this scheme adopts a concrete or stone water weir, and the water level is raised to form a waterfall. In order to meet the requirements for the maintenance and emptying of the filter bed, drainage gates are arranged at intervals in the longitudinal direction of the filter bed.

Claims

1. A gravel filter bed process design method based on model test, characterized in that: Follow the steps below to implement it: Step 1: Monitor water quality in the application area and clarify water sample measurement indicators; Step 2, obtaining the biofilm of the gravel filter bed reactor for indoor testing through an in-situ biofilm test, and determining the filler; Step 3, establish a hydrodynamic model of the application area to determine the velocity and flow rate of the gravel filter bed; Step 4, forming a biofilm on the gravel filter bed reactor, determining the test conditions of the gravel filter bed reactor and conducting a simulation test to obtain the concentration and along-process variation characteristics of the water sample measurement indicators; Step 5, conducting an impact resistance test to determine the maximum flow rate that the gravel filter bed reactor can allow under the condition that the effluent quality meets the standard; Step 6: Based on the test results, obtain the gravel filter bed layout type suitable for different river channels.

2. The gravel filter bed process design method based on model test according to claim 1 is characterized in that: In step 1, the time periods for water quality monitoring are summer and winter; Water sample measurement indicators include NO3 — N、NH4 + -N, TN, PO4 3— P, TP, COD.

3. The gravel filter bed process design method based on model test according to claim 2 is characterized in that: The specific process of step 2 is: select fillers with different particle sizes in the application area and put them into multiple stainless steel mesh barrels respectively, and then place the stainless steel mesh barrels in the water body of the application area. After on-site biofilm formation, the biofilm attached to the surface of the filler is peeled off and the biofilm characterization is measured. According to the measurement results, the filler type and particle size are determined.

4. The gravel filter bed process design method based on model test according to claim 3 is characterized in that: The specific process of step 3 is as follows: import the plan of the application area into MIKE21 to establish the river bank line, riverbed depth, gravel filter bed inlet flow, inlet and outlet water level information, build the MIKE 21 FM hydrodynamic model, simulate the water level and flow rate of the water system in the application area through the MIKE 21 FM hydrodynamic model, and then obtain the flow rate of the gravel filter bed through the flow rate and the flow area of ​​the gravel filter bed reactor.

5. The gravel filter bed process design method based on model test according to claim 4 is characterized in that: The specific process of step 4 is: Step 4.1, adding one or more of the fillers specified in step 2, the functional fillers G1, and the functional fillers G2 to multiple gravel filter bed reactors, and running a peristaltic pump to transport water into each gravel filter bed reactor, and adjusting the flow rate of the peristaltic pump to ensure a constant flow rate in each gravel filter bed reactor; Step 4.2, forming a biofilm on the gravel filter bed reactor; Step 4.3, conduct simulation tests with different water qualities, different hydraulic retention times, different aeration volumes, different aeration modes, and different operating days as test conditions, regularly measure the effluent samples of the gravel filter bed reactor, and obtain the concentrations and along-the-process variation characteristics of the water sample measurement indicators under different operating conditions of each gravel filter bed reactor.

6. The gravel filter bed process design method based on model test according to claim 5 is characterized in that: The specific process of step 4.2 is as follows: the biofilm formation in the gravel filter bed reactor includes an intermittent start-up stage and a continuous biofilm formation stage; Intermittent startup stage: the water sample containing sediment collected in the application area is used as inoculation water, and the biofilm peeled off in step 2 is used as the inoculation source. The inoculation water and the inoculation source are mixed evenly and added to the gravel filter bed reactor for aeration for several days. Aeration is carried out once in the morning, noon and evening every day. The water quality of the gravel filter bed reactor at different aeration days is measured respectively. After the aeration is completed on the last day, all the inoculation water is discharged from the gravel filter bed reactor, and then the inoculation water and the inoculation source of the same volume as the discharged inoculation water are added to the gravel filter bed reactor again, and the above process is repeated; Continuous biofilm formation stage: After all the inoculated water is discharged for the last time, a peristaltic pump is used to continuously add artificial water until biofilm formation is successful.

7. The gravel filter bed process design method based on model test according to claim 5 is characterized in that: In step 5, the impact resistance test is achieved by increasing the water flow rate and reducing the hydraulic retention time.

8. The gravel filter bed process design method based on model test according to claim 7 is characterized in that: In step 6, the gravel filter bed layout types for different river channels include: The first type: For rivers that need to undertake flood discharge tasks, a separated gravel filter bed layout is adopted, that is, the gravel filter bed is arranged outside the flood discharge area of ​​the river, and part of the water in the river is introduced into the gravel filter bed for treatment, and then returned to the river downstream; The second type: For rivers that do not need to bear the task of flood discharge, the gravel filter bed is directly arranged in the river channel, so that all the river water flows through the gravel filter bed for full-scale treatment, or part of the water overflows from the upper part of the gravel filter bed, and part of the water enters the gravel filter bed for treatment.

9. The gravel filter bed process design method based on model test according to claim 8, characterized in that: For the first case: according to the water diversion method, it is divided into a separated gravel filter bed with no dam diversion and a separated gravel filter bed with dam diversion; The damless water diversion separated gravel filter bed comprises a water diversion channel (5) arranged on one side of a river channel, a waterfall (1) across the river channel is arranged in the river channel upstream of the water diversion channel (5), a sand barrier (2), a trash rack (3) and a gate (4) are arranged in sequence at the inlet of the water diversion channel (5), the sand barrier (2) is arranged at the inlet where the water diversion channel (5) is connected to the river channel and is connected to the side wall of the water diversion channel (5), the trash rack (3) is arranged downstream of the sand barrier (2), both sides of the trash rack (3) are connected to the side wall of the water diversion channel (5), the gate (4) is arranged downstream of the trash rack (3), the gate (4) is connected to the bottom plate and side wall of the water diversion channel (5), and a gravel filter bed (6) is arranged at the outlet of the water diversion channel (5), the gravel filter bed (6) is filled with filler, and the bottom of the gravel filter bed (6) is connected to the downstream of the river channel through the outlet channel (7); The separated gravel filter bed with dam water diversion comprises a water diversion channel (5) arranged on one side of a river channel, a waterfall (5) across the river channel is arranged in the river channel upstream of the water diversion channel (5), a water barrier (8) across the river channel is arranged in the river channel upstream of the water diversion channel (5), a sand retaining bank (2), a trash rack (3), and a gate (4) are arranged in sequence at the inlet of the water diversion channel (5), and the sand retaining bank (2) is arranged at the entrance where the water diversion channel (5) is connected to the river channel and is connected to the water diversion channel (5). The trash rack (3) is arranged downstream of the sand barrier (2), and both sides of the trash rack (3) are connected to the side walls of the water diversion channel (5). The gate (4) is arranged downstream of the trash rack (3), and the gate (4) is connected to the bottom plate and side walls of the water diversion channel (5). A gravel filter bed (6) is arranged at the outlet of the water inlet channel (5), and the gravel filter bed (6) is filled with fillers. The bottom of the gravel filter bed (6) is connected to the downstream of the river through the outlet channel (7).

10. The gravel filter bed process design method based on model test according to claim 8, characterized in that: For the second case: including the gravel filter bed directly arranged horizontally in the river channel and the gravel filter bed directly arranged vertically in the river channel; The structure in which the gravel filter bed is directly arranged transversely in the river channel specifically comprises: a grit chamber (9), a waterfall (1), and a gravel filter bed (6) are arranged in sequence in the river channel and along the direction of water flow; a drainage channel (10) is arranged on one side of the grit chamber (9) close to the waterfall (1) and close to the river bank; the drainage channel (10) is arranged along the direction of water flow in the river channel and has a length not less than the distance from the outlet side of the grit chamber (9) to the outlet side of the gravel filter bed (6); one end of the gravel filter bed (6) is connected to the inner side wall of the river channel, and the other end of the gravel filter bed (6) is connected to the side wall of the drainage channel (10); The structure in which the gravel filter bed is directly arranged longitudinally in the river channel specifically comprises: a sand settling tank (9), a waterfall (1), and a gravel filter bed (6) are arranged in sequence in the river channel and along the direction of water flow; the gravel filter bed (6) is provided with a plurality of drainage gates (11) along the direction of water flow; the width of the gravel filter bed (6) is smaller than the width of the river channel and is arranged along the direction of water flow in the river channel.

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