Method for designing gravel filter bed process based on model test

Abstract

The application discloses a gravel filter bed process design method based on model test, and is implemented according to the following steps: water quality monitoring is carried out on an application area to determine water sample determination indexes; biological membranes of indoor test gravel filter bed reactors are obtained through in-situ biofilm test to determine fillers; a hydrodynamic model of the application area is established to determine gravel filter bed flow velocity and flow rate; biofilm is hung on the gravel filter bed reactor to determine test working conditions of the gravel filter bed reactor and carry out simulation test, and the concentration of the water sample determination indexes and the variation characteristics along the way are obtained; impact resistance test is carried out to determine the maximum flow velocity of the gravel filter bed reactor under the condition that the effluent water quality meets the standard; and the arrangement type of the gravel filter bed of different river channels is obtained according to the test results. The method can provide a basis for popularization and application of the gravel filter bed in water environment treatment engineering.

Description

Technical Field

[0001] This invention belongs to the field of hydraulic engineering technology, specifically relating to a gravel filter bed process design method based on model tests. Background Technology

[0002] Gravel contact oxidation technology, also known as gravel filter bed technology, is a rapid wastewater treatment method. It was first designed by W.J. Dibden, a wastewater treatment engineer in London, England in the 19th century, as a natural treatment method. In essence, it is an artificial enhancement of the biofilm that grows on the surface of gravel in natural riverbeds.

[0003] Inter-gravel contact oxidation removes pollutants primarily through multiple processes including contact sedimentation, adsorption, and biodegradation. This method creates continuous water flow channels between the gravels. When wastewater passes through, suspended solids in the water move to the gravel surface due to sedimentation, physical interception, and hydrodynamic forces, resulting in contact sedimentation. Simultaneously, microorganisms or algae growing on the gravel surface oxidize and decompose the adsorbed pollutants. The inter-gravel contact oxidation purification system guides the target water body through a treatment tank filled with packing material, allowing the wastewater to react with the biofilm on the packing material surface, thereby purifying the water.

[0004] Gravel contact oxidation, as a biological / ecological method for treating polluted rivers and lakes, has the advantages of being environmentally friendly, energy-saving, and easy to operate and manage. However, it has not yet been widely promoted. The engineering characteristics and applicability of gravel filters in natural river channels have not been fully studied and proven. Therefore, it is necessary to establish an experimental model, study the design of gravel filters, explore the characteristics of pollutant reduction by gravel filters, and provide a basis for the practical application of gravel filters in designated areas. Summary of the Invention

[0005] The purpose of this invention is to provide a gravel filter bed process design method based on model experiments, which can provide a basis for the promotion and application of gravel filters in water environment treatment projects.

[0006] The technical solution adopted in this invention is a gravel filter bed process design method based on model experiments, which is implemented according to the following steps:

[0007] Step 1: Conduct water quality monitoring in the application area and determine the water sample measurement indicators;

[0008] Step 2: Obtain the biofilm from the gravel filter bed reactor used in the indoor test through in-situ biofilm attachment experiments to determine the packing material;

[0009] Step 3: Establish a hydrodynamic model of the application area to determine the flow velocity and flow rate of the gravel filter bed;

[0010] Step 4: Attach a biofilm to the gravel filter bed reactor, determine the experimental conditions of the gravel filter bed reactor and conduct a simulation experiment to obtain the concentration and flow characteristics of the water sample indicators.

[0011] Step 5: Conduct a shock resistance test to determine the maximum allowable flow rate of the gravel filter bed reactor under the condition that the effluent quality meets the standards;

[0012] Step 6: Based on the test results, obtain the gravel filter bed layout patterns for different river channels.

[0013] The invention is further characterized in that,

[0014] In step 1, the water quality monitoring period is during summer and winter;

[0015] Water sample testing indicators include NO3 — N, NH4 + -N, TN, PO4 3— P, TP, COD.

[0016] The specific process of step 2 is as follows: Select fillers of different particle sizes in the application area and put them into multiple stainless steel mesh buckets. Then place the stainless steel mesh buckets in the water body of the application area. After on-site biofilm formation, peel off the biofilm attached to the surface of the filler and perform biofilm characterization and measurement. Based on the measurement results, determine the filler type and particle size.

[0017] The specific process of step 3 is as follows: import the application area plan into MIKE21 to establish information on the riverbank, riverbed depth, gravel filter inlet flow rate, and inlet and outlet water levels. Build the MIKE 21 FM hydrodynamic model, simulate the water level and flow velocity of the water system in the application area using the MIKE 21 FM hydrodynamic model, and then obtain the flow rate of the gravel filter bed through the flow velocity and the flow area of ​​the gravel filter bed reactor.

[0018] The specific process of step 4 is as follows:

[0019] Step 4.1: Add one or more of the packing material, functional packing material G1, and functional packing material G2 specified in Step 2 to multiple gravel filter bed reactors, and run peristaltic pumps to deliver water to each gravel filter bed reactor, and adjust the flow rate of the peristaltic pumps to ensure that the flow rate of each gravel filter bed reactor is constant.

[0020] Step 4.2: Attach a biofilm to the gravel filter bed reactor;

[0021] Step 4.3: Simulation experiments were conducted under different water quality, hydraulic retention time, aeration rate, aeration method, and number of operating days. The effluent water samples from the gravel filter reactor were measured periodically to obtain the concentration and flow characteristics of the water sample indicators under different operating conditions for each gravel filter reactor.

[0022] 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;

[0023] Intermittent start-up phase: Water samples containing bottom sediment collected in the application area are used as inoculation water. The biofilm sloughed off in step 2 is used as the inoculation source. The inoculation water and 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 each day. The water quality in the gravel filter bed reactor for different aeration days is measured. After the last day of aeration, all inoculation water is discharged from the gravel filter bed reactor. Then, an inoculation water and inoculation source of the same volume as the discharged inoculation water are added back to the gravel filter bed reactor. The above process is repeated.

[0024] Continuous biofilm formation stage: After the last drainage of all inoculation water, artificial water is continuously added using a peristaltic pump until biofilm formation is successful.

[0025] In step 5, the impact resistance test is achieved by increasing the water flow velocity and reducing the hydraulic residence time.

[0026] In step 6, the gravel filter bed arrangement patterns for different river channels include:

[0027] The first method is to use a separated gravel filter bed arrangement for rivers that need to carry out flood control tasks. That is, the gravel filter bed is placed outside the flood control area of ​​the river. A portion of the river water is introduced into the gravel filter bed for treatment and then returned to the river downstream.

[0028] The second method involves placing gravel filter beds directly into rivers that do not require flood control, allowing all river water to flow through the gravel filter beds for full-volume treatment, or allowing some water to overflow from the top of the gravel filter beds while some water enters the gravel filter beds for further treatment.

[0029] For the first case: based on the water diversion method, it is divided into separate gravel filter beds with water diversion without a dam and separate gravel filter beds with water diversion with a dam;

[0030] The damless water diversion separated gravel filter bed includes a water diversion channel set on one side of the river. A waterfall is arranged across the river in the upstream section of the water diversion channel. The inlet of the water diversion channel is equipped with a sand retainer, a trash rack, and a gate in sequence. The sand retainer is arranged at the entrance where the water diversion channel connects to the river and is connected to the side wall of the water diversion channel. The trash rack is set downstream of the sand retainer and is connected to the side wall of the water diversion channel on both sides. The gate is arranged downstream of the trash rack and is connected to the bottom plate and side wall of the water diversion channel. The outlet of the water diversion channel is equipped with a gravel filter bed filled with filler. The bottom of the gravel filter bed is connected to the downstream of the river through the outlet channel.

[0031] The dammed, separated gravel filter bed includes an intake channel located on one side of the river. A waterfall spans the river upstream of the intake channel, and a dam also spans the river upstream of the intake channel. The intake channel inlet is equipped with a sand-blocking sill, a debris screen, and a gate. The sand-blocking sill is located at the entrance where the intake channel connects to the river and is connected to the sidewall of the intake channel. The debris screen is located downstream of the sand-blocking sill, with both sides connected to the sidewall of the intake channel. The gate is located downstream of the debris screen and is connected to the bottom plate and sidewall of the intake channel. A gravel filter bed is located at the outlet of the intake channel, filled with filler material. The bottom of the gravel filter bed is connected to the downstream of the river via an outlet channel.

[0032] The second scenario includes gravel filter beds arranged horizontally directly within the river channel and gravel filter beds arranged vertically directly within the river channel.

[0033] The structure of the gravel filter bed being arranged transversely in the river channel is as follows: it includes a sedimentation tank, a waterfall, and a gravel filter bed arranged sequentially in the river channel and along the direction of water flow. A drainage channel is set up near the waterfall and on the side of the river channel near the sedimentation tank. The drainage channel is set up 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 sedimentation tank to the outlet side of the gravel filter bed. One end of the gravel filter bed is connected to the inner wall of the river channel, and the other end of the gravel filter bed is connected to the side wall of the drainage channel.

[0034] The structure of the gravel filter bed being arranged longitudinally within the river channel specifically includes a sedimentation tank, a drop structure, and a gravel filter bed arranged sequentially within the river channel and along the direction of water flow. Several drainage gates are installed along the direction of water flow on the gravel filter bed. 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.

[0035] The beneficial effects of this invention are as follows: This invention is a gravel filter bed process design method based on model experiments. Starting from the analysis of water quality, biofilm types and applicable fillers in the application area of ​​the gravel filter bed, it establishes a gravel filter bed flow model in the application area, conducts continuous indoor experiments under different operating conditions, monitors changes in pollutant concentrations, analyzes the operating characteristics of the gravel filter bed reactor under different operating conditions, and proposes gravel filter bed layout patterns for different rivers based on the experimental results. This provides a basis for the promotion and application of gravel filters in water environment management projects. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the gravel filter bed reactor in the method of the present invention;

[0037] Figure 2 This refers to the change in nitrogen concentration in the inoculation mixture during the intermittent start-up period in the method of this invention.

[0038] Figure 3 This refers to the change in phosphorus concentration in the inoculation mixture during the intermittent start-up period in the method of this invention.

[0039] Figure 4 This refers to the change in nitrogen concentration in each gravel filter bed reactor during the continuous biofilm formation process in the method of this invention.

[0040] Figure 5 The PO4 in the influent and effluent of each gravel filter bed reactor during the continuous biofilm formation period in the method of this invention is... 3 --Changes in P concentration over time;

[0041] Figure 6 This invention describes the time-varying nitrogen removal rate of different gravel filter bed reactors under different operating conditions of water quality in winter in the method of this invention.

[0042] Figure 7 This invention describes the variation of nitrogen concentration in the influent and effluent of different gravel filter bed reactors under different operating conditions of water quality in winter.

[0043] Figure 8 The method of the present invention shows the time-varying phosphorus concentration and removal rate of influent and effluent of different gravel filter bed reactors under different winter water quality conditions.

[0044] Figure 9 These are the average phosphate concentrations and removal rates of different gravel filter bed reactors under different operating conditions of water quality in winter, as described in the method of this invention.

[0045] Figure 10 This invention describes the variation of nitrogen concentration in the influent and effluent of different gravel filter bed reactors under different operating conditions of water quality in summer.

[0046] Figure 11 This invention describes the time-varying nitrogen removal rate of different gravel filter bed reactors under different operating conditions of water quality in summer in the method of this invention.

[0047] Figure 12 The average nitrogen concentrations of the influent and effluent of different gravel filter bed reactors under different operating conditions of water quality in summer in the method of the present invention;

[0048] Figure 13 The average nitrogen removal rate of different gravel filter bed reactors under different operating conditions of water quality in summer in the method of the present invention;

[0049] Figure 14 The average phosphate concentration and removal rate of different gravel filter bed reactors under different operating conditions of water quality in summer according to the method of the present invention.

[0050] Figure 15 This invention describes the variation of TN concentration along the flow path in various gravel filter bed reactors under different water quality conditions during winter.

[0051] Figure 16 This invention describes the variation of TN concentration along the flow path in various gravel filter bed reactors under different water quality conditions during summer.

[0052] Figure 17 This refers to the time-dependent change in nitrogen content during the impact resistance test in the method of this invention.

[0053] Figure 18 This refers to the average nitrogen concentration in the effluent from the impact resistance test in the method of this invention.

[0054] Figure 19 This refers to the time-dependent change in phosphate content during the impact resistance test in the method of this invention.

[0055] Figure 20 This refers to the average phosphate concentration in the effluent from the impact resistance test in the method of this invention.

[0056] Figure 21 This is a plan view of the damless water diversion and separation gravel filter bed in the method of the present invention;

[0057] Figure 22 This is a plan view of the gravel filter bed with dam water diversion separation in the method of the present invention;

[0058] Figure 23 This is a plan view of the direct transverse gravel filter bed in the method of the present invention;

[0059] Figure 24 This is a plan view of the direct longitudinal gravel filter bed in the method of the present invention.

[0060] In the diagram, 1. Waterfall, 2. Sand barrier, 3. Trash rack, 4. Gate, 5. Water intake channel, 6. Gravel filter bed, 7. Water outlet channel, 8. Dam, 9. Sedimentation tank, 10. Drainage channel, 11. Drainage gate, 12. Gravel filter bed reactor. Detailed Implementation

[0061] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0062] Example 1

[0063] The gravel filter bed process design method based on model experiments of this invention is implemented according to the following steps:

[0064] Step 1: Conduct water quality monitoring in the application area and determine the water sample measurement indicators;

[0065] Step 2: Obtain the biofilm from the gravel filter bed reactor used in the indoor test through in-situ biofilm attachment experiments to determine the packing material;

[0066] Step 3: Establish a hydrodynamic model of the application area to determine the flow velocity and flow rate of the gravel filter bed;

[0067] Step 4: Attach a biofilm to the gravel filter bed reactor, determine the experimental conditions of the gravel filter bed reactor and conduct a simulation experiment to obtain the concentration and flow characteristics of the water sample indicators.

[0068] Step 5: Conduct a shock resistance test to determine the maximum allowable flow rate of the gravel filter bed reactor under the condition that the effluent quality meets the standards;

[0069] Step 6: Based on the test results, obtain the gravel filter bed layout patterns for different river channels.

[0070] In this embodiment, based on water quality monitoring, in-situ biofilm formation tests, hydrodynamic models, and simulations of different operating conditions, parameters such as water quality, flow rate, and flow rate of the gravel filter bed reactor are determined. Continuous indoor tests and shock resistance tests of the gravel filter bed reactor are conducted to analyze the effects of factors such as aeration, functional packing materials, and air-to-water ratio on pollutant removal, as well as the changes in pollutant concentration along the reactor, providing a basis for the application of gravel filters.

[0071] Example 2

[0072] Based on Example 1, water quality monitoring was conducted in the application area. Through on-site investigation, the pollution characteristics of rivers and lakes were understood, the water quality characteristics of untreated rivers and lakes were identified, and the water quality, pollutant types, and concentration ranges of the water to be introduced into the gravel filter bed were determined. This clarified the water sample measurement indicators, including NO3. - -N, NH4 + -N, TN (total nitrogen), PO4 3- -P, TP (total phosphorus), COD (chemical oxygen demand), NO2 - -N.

[0073] To ensure the water samples are representative and accurately reflect the water quality of the application area, water samples were randomly collected from different locations in summer and winter. The types and concentrations of pollutants in the water were measured and analyzed, as detailed in Tables 1 and 2.

[0074] Table 1 Water quality in different locations during summer (July-August)

[0075]

[0076] Note: Except for T, which is in °C, all other values ​​are in mg / L.

[0077] Table 2 Water quality in different locations during winter (October to December)

[0078]

[0079] Note: Except for T, which is in °C, all other values ​​are in mg / L.

[0080] As can be seen from Tables 1 and 2, water quality differs somewhat between summer and winter.

[0081] Based on the above differences, the influent water of the gravel filter bed reactor was tested separately for summer and winter. The influent water quality for summer and winter is shown in Table 3.

[0082] Table 3. Influent water quality during winter and summer for the experiment.

[0083]

[0084] Example 3

[0085] Based on Example 2, the specific process of step 2 is as follows: Select fillers with different particle sizes in the application area and put them into 10 stainless steel mesh buckets. Then place the stainless steel mesh buckets in the water body of the application area. After on-site biofilm formation, peel off the biofilm attached to the surface of the filler and perform biofilm characterization and measurement. Based on the measurement results, determine the filler type and particle size.

[0086] Five types of fillers were used: 3cm crushed stone, 5cm crushed stone, 3cm pebbles, 5cm pebbles and 10cm pebbles. The stainless steel mesh buckets were 32cm high and 20cm in diameter, with a mesh size of 2cm×2cm. Two stainless steel mesh buckets were used for in-situ biofilm formation tests for each type of filler.

[0087] All fillers must be thoroughly cleaned before being placed into the stainless steel mesh bucket. Then, the porosity and specific surface area of ​​different particle sizes of stone are measured using a 10L plastic measuring cup, and the results are recorded and calculated. After the calculation is completed, the fillers are loaded into the stainless steel mesh bucket and installed on site. When hanging, ensure that the bottom of the stainless steel mesh bucket is 20cm away from the riverbed.

[0088] After biofilm formation, other impurities attached to the packing material surface were removed. Then, multiple packing materials were selected from different locations in the same stainless steel mesh bucket as targets for biofilm removal. The biofilm on each selected packing material was removed one by one using a stiff brush, and the removed biofilm was collected for subsequent measurements. The following indicators were measured on the collected biofilm: total biofilm amount and high-throughput sequencing of microorganisms in the biofilm. The total biofilm amount was characterized by total SS (biofilm dry weight) and total VSS (biofilm volatile dry weight). The specific results are detailed in Table 4.

[0089] Table 4 Total amount of exfoliated biofilm of different particle sizes

[0090]

[0091] As can be seen from Table 4, among the same type of packing material, the 3cm particle size packing material has a greater amount of biofilm attached than the 5cm particle size packing material. Among different types, the same volume of crushed stone has a greater amount of biofilm attached than that of pebbles. Therefore, 3cm crushed stone was finally selected as the packing material for the gravel filter bed reactor in this embodiment.

[0092] High-throughput analysis of biofilm formation experiments revealed that actual water bodies contain a variety of microorganisms with different functions, possessing sufficient potential for pollutant degradation. Therefore, it was determined that actual on-site water samples should be selected as the inoculum source when starting up the biofilm formation in the laboratory gravel filter reactor to promote rapid biofilm formation while ensuring the similarity of species within the biofilm.

[0093] Example 4

[0094] Based on Example 3, the specific process of step 3 is as follows: import the application area plan into MIKE21 to establish information on the riverbank, riverbed depth, gravel filter inlet flow rate, and inlet and outlet water levels; build a MIKE 21 FM hydrodynamic model; simulate the water level and flow velocity of the water system in the application area using the MIKE 21 FM hydrodynamic model; and then obtain the flow rate of the gravel filter bed through the flow velocity and the flow area of ​​the gravel filter bed reactor.

[0095] 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 formation test.

[0096] Example 5

[0097] Based on Example 4, the specific process of step 4 is as follows:

[0098] Step 4.1: Add one or more of 3cm gravel, functional packing G1, and functional packing G2 to the four gravel filter bed reactors respectively, and run a four-channel constant flow peristaltic pump to deliver water to each gravel filter bed reactor. Adjust the flow rate of the peristaltic pump to ensure that the flow rate of each gravel filter bed reactor is constant.

[0099] Specifically, such as Figure 1 As shown, the gravel filter bed reactor 12 is cylindrical, with several outlets evenly spaced along the water flow direction on its sidewalls, and one outlet at its bottom. All outlets are equipped with valves. The packing materials added to the four gravel filter bed reactors (denoted as 1#, 2#, 3#, and 4#) are as follows: 1# is 100% crushed stone; 2# is 67.7% crushed stone + 32.3% zeolite (crushed stone at the bottom, zeolite at the top); and 3# is 67.7% crushed stone + 32.3% zeolite. Volcanic rock (gravel at the bottom, volcanic rock at the top), #4 is 67.7% gravel + 16.1% zeolite + 16.2% volcanic rock (gravel at the bottom, zeolite in the middle, volcanic rock at the top); each channel of the four-channel peristaltic pump corresponds to one gravel filter bed reactor. Water is delivered to each gravel filter bed reactor by running the four-channel constant flow peristaltic pump. The flow rate of the peristaltic pump is adjusted according to the cross-sectional area of ​​the gravel filter bed reactor to ensure a constant flow velocity in the gravel filter bed reactor packing.

[0100] Step 4.2: Attach a biofilm to the gravel filter bed reactor;

[0101] The biofilm formation process in a gravel filter bed reactor includes an intermittent start-up phase and a continuous biofilm formation phase.

[0102] Intermittent start-up phase: Water samples containing bottom sediment collected in the application area are used as inoculation water (50L). The biofilm sloughed off in step 2 is used as the inoculation source. The inoculation water and inoculation source are mixed evenly (the resulting inoculation mixture) and added to the gravel filter reactor for aeration for 6 days, aerating once each in the morning, noon and evening. The water quality in the gravel filter reactor is measured on day 0, day 3 and day 6. After day 6, all inoculation water is discharged from the gravel filter reactor, and then an equal volume of inoculation water and inoculation source is added back to the gravel filter reactor. The above process is repeated.

[0103] Continuous biofilm formation stage: After the last drainage of all inoculation water, artificial water is continuously added using a peristaltic pump, and the process is continued until biofilm formation is successful under a hydraulic retention time of 12 hours.

[0104] The specific inoculation mixture and artificial water used for biofilm formation are shown in Table 5.

[0105] Table 5. Water used in the biofilm formation stage experiment

[0106]

[0107] like Figure 2 As shown, during the intermittent start-up phase, the TN concentration in gravel filter reactors #1, #2, #3, and #4 exhibited a consistent trend, decreasing over time in each cycle. However, compared to the other gravel filter reactors, the decrease was slowest in reactor #1, indicating that the addition of functional packing material significantly contributed to the reduction of total nitrogen concentration in the water during the initial biofilm formation stage. Ammonia nitrogen concentration in all gravel filter reactors showed a decreasing trend, but compared to reactor #1, the decrease was faster in reactors #2, #3, and #4, indicating that the addition of functional packing material had a certain promoting effect on the reduction of ammonia nitrogen concentration in the water during the initial biofilm formation stage, and also indicating that nitrification occurred in the gravel filter reactors. Nitrate nitrogen concentration in all four gravel filter reactors showed a decreasing trend, while nitrite nitrogen concentration decreased to some extent, indicating that nitrification and denitrification reactions occurred in all gravel filter reactors. In conclusion, after 12 days of intermittent start-up, a certain amount of nitrogen removal-related microbial strains were inoculated into the gravel filter reactors.

[0108] like Figure 3 As shown, in the first and second cycles of the intermittent start-up period, regardless of PO4 3-Both -P and TP concentrations showed significant decreases, with the most pronounced decreases in reactors #2 and #3, followed by reactor #4, while reactor #1 showed a smaller decrease. Therefore, it can be concluded that the decrease in phosphorus concentration in the water during the initial startup phase is closely related to the adsorption effect of the functional packing material itself.

[0109] Continuous film attachment stage: such as Figure 4 As shown, the TN concentrations in the effluent from gravel filter reactors #1, #2, #3, and #4 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 gravel filter reactor #2 showed the best TN removal efficiency, followed by #4. Since reactors #2 and #4 were filled with 32% and 16% zeolite, respectively, this indicates that the adsorption of zeolite packing played a role in TN removal during continuous biofilm formation. NH3 contributed the most to TN removal during the continuous biofilm formation period. 4+ -N removal, stable phase: NH3 in the effluent of gravel filter bed reactors #1, #2, #3, and #4 4+ The -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 packing material significantly reduced the NH4+ concentration during continuous biofilm formation. 4+ The adsorption of -N directly leads to an increase in TN removal rate. During the first 12 days of continuous biofilm formation, the NO₂ in the effluent from each gravel filter reactor... 3- -N concentration gradually decreased and then tended to stabilize. During the stable phase, the NO3 concentration in the effluent from gravel filter reactors #1, #2, #3, and #4 was [high]. - The -N concentrations were 0.06 mg / L, 0.06 mg / L, 0.04 mg / L, and 0.07 mg / L, respectively, indicating that denitrifying bacteria played a certain role in the reactor. However, due to oxygen limitation, the activity of nitrifying bacteria was restricted, resulting in weak nitrification in the initial stage. The concentrations of nitrite (NO2) in the gravel filter reactor were [not specified]. - The nitrogen (DO) concentrations were generally below 0.2 mg / L. In summary, after 12 days of continuous biofilm formation, the gravel filter reactors gradually entered a stable phase. During this stable phase, each reactor achieved some nitrogen removal under the action of microorganisms. However, due to the extremely low DO concentration in the gravel filter reactors, the biological removal of nitrogen was limited. The adsorption of nitrogen by the functional packing zeolite in the early stage of biofilm formation was the main reason for the differences in nitrogen concentration in the effluent of each gravel filter reactor.

[0110] like Figure 5As shown, in the initial stage of continuous biofilm formation, the removal efficiency of phosphate concentration in the water varied significantly among the gravel filter reactors, mainly due to the physical adsorption effect of the functional packing material. After 20 days, the phosphate concentration in the effluent of each gravel filter reactor gradually increased, and the removal efficiency began to decline. However, the phosphate concentration in the effluent of gravel filter reactors #3 and #4 was relatively low, indicating that the adsorption of phosphorus by the volcanic rock functional packing material in the gravel filter reactors was more significant during the biofilm formation stage.

[0111] Step 4.3: Simulation tests were conducted on four gravel filter reactors under different operating conditions, including different water quality, different hydraulic retention time, different aeration rate, different aeration method, and different number of operating days. The effluent water samples from the gravel filter reactors were measured periodically to obtain the concentration and flow characteristics of the water sample indicators under different operating conditions for each gravel filter reactor. This allowed for the determination of the operating conditions with the best concentration and flow characteristics of the water sample indicators.

[0112] The specific test conditions are shown in Table 6, where the water quality in winter and summer is the same as that recorded in Table 3.

[0113] Table 6 Continuous test conditions of gravel filter bed reactor

[0114]

[0115] During the experiment, water samples were collected from the gravel filter reactor effluent every 3 days, and water samples were collected along the flow path after each stable operating condition. All water samples were measured for the following routine parameters, including total nitrogen (TN) and NH4+. + -N, NO3 - -N, NO2 - -N,PO4 3- -P.

[0116] For winter water quality, the nitrogen concentration variation trends are similar among gravel filter reactors under the same operating conditions, but there are significant differences in nitrogen concentration under different operating conditions. For example... Figure 6 As shown, during the test, the influent TN and NH4... + -N and NO3 - 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, respectively, with corresponding average concentrations of 10.67 mg / L, 8.14 mg / L, and 2.37 mg / L. The NH4+ effluent from gravel filter reactors #1, #2, #3, and #4... +The average concentrations of -N were 5.96 mg / L, 5.02 mg / L, 6.35 mg / L, and 5.63 mg / L under operating condition 1; 0.42 mg / L, 0.42 mg / L, 0.08 mg / L, and 0.16 mg / L under operating condition 2; 3.34 mg / L, 2.92 mg / L, 3.12 mg / L, and 2.93 mg / L under operating condition 3; and 2.07 mg / L, 2.16 mg / L, 2.24 mg / L, and 2.19 mg / L under operating condition 4. Therefore, NH4+... + The removal rate of NH4+ was significantly higher with aeration than without aeration. This was also observed in condition 2. + -N removal rates can reach up to 100%. NO3 removal rates in each reactor... - -N removal rate and NH4 + -N removal rates showed the opposite trend, with NO3 removal rates in the effluent from reactors #1, #2, #3, and #4 increasing. - The average NO3- concentrations were 0.07 mg / L, 0.01 mg / L, 0.01 mg / L, and 0.06 mg / L under operating condition 1; 7.41 mg / L, 8.25 mg / L, 8.16 mg / L, and 8.67 mg / L under operating condition 2; 1.35 mg / L, 0.46 mg / L, 1.37 mg / L, and 1.30 mg / L under operating condition 3; and 3.05 mg / L, 3.02 mg / L, 3.04 mg / L, and 3.24 mg / L under operating condition 4. It can be seen that with the increase of aeration rate, the effluent NO3- concentration... - -N concentration increases, while in condition 1 without aeration, the nitrate removal rate can reach 100%.

[0117] like Figure 7 As shown, for winter water quality, aeration significantly affects the nitrogen conversion in the gravel filter reactor, thus affecting the concentration of different forms of nitrogen in the effluent. Under sufficient oxygen supply, the gravel filter reactor is capable of removing 100% of ammonia nitrogen, while under oxygen-free conditions, it is capable of removing 100% of nitrate nitrogen. Therefore, to maximize TN removal, suitable aeration conditions are those that maximize TN removal. In this embodiment, under continuous aeration conditions with an air-to-water ratio of 1:3, the TN removal rate of the influent in winter can reach a maximum of 69.1%, meaning that condition 3 is the optimal condition.

[0118] like Figure 8As shown, for winter water quality, the phosphorus concentration variation trends among the gravel filter reactors were similar, but the phosphorus removal efficiency varied to some extent. Furthermore, the phosphorus concentration variation also differed under different operating conditions. During the experiment, the average phosphate concentrations in the effluent from reactors #1, #2, #3, and #4 were 0.53 mg / L, 0.53 mg / L, 0.52 mg / L, and 0.55 mg / L under operating condition 1; 0.53 mg / L, 0.54 mg / L, 0.49 mg / L, and 0.54 mg / L under operating condition 2; 0.51 mg / L, 0.52 mg / L, 0.45 mg / L, and 0.50 mg / L under operating condition 3; and 0.53 mg / L, 0.51 mg / L, 0.53 mg / L, and 0.53 mg / L under operating condition 4. Data shows that, except for operating condition 3, the average effluent phosphorus concentration of the same gravel filter reactor did not differ significantly under other operating conditions. However, among different gravel filter reactors, the No. 3 gravel filter reactor consistently achieved the highest removal rate, reaching up to 46.7%. Figure 9 This can be seen more intuitively. This may be related to the adsorption effect of the functional packing material, and is also affected by the microorganisms in the reactor related to phosphorus removal.

[0119] For summer water quality, the time-varying changes in nitrogen concentrations in the influent and effluent of different reactors under different aeration conditions are as follows: Figure 10 As shown, the corresponding nitrogen removal rate changes over time are as follows: Figure 11 As shown in the figure, the average nitrogen concentration and average nitrogen removal rate of different reactors under different aeration conditions are as follows: Figure 12 and 13 As shown in the figures, the gravel filter reactors under all operating conditions have a certain nitrogen removal effect on the influent. The nitrogen removal effects are similar among the gravel filter reactors, but there are significant differences in nitrogen concentration between different operating conditions.

[0120] For summer water quality, under operating conditions IV, V, and VI, the effluent TN concentration was less than 2 mg / L, meeting the Class V surface water quality requirements. Among these, under continuous aeration conditions, operating condition IV resulted in the lowest effluent TN concentration and the highest removal rate of 70.53%. Under intermittent aeration conditions, operating condition V further reduced the effluent TN concentration, achieving a removal rate of up to 76.37%. Except for operating condition I, the effluent NH4+ concentration was significantly higher under the other operating conditions. + The NH4+ concentration was below 1.5 mg / L, meeting the Class IV surface water quality requirements. Specifically, the effluent under operating conditions II and III had almost no NH4+. + -N removal rates can reach their highest levels, up to 100%, meeting the Class I surface water quality requirements. Simultaneously, NH4+ can be detected in the effluent. + The NH4+ concentration in the effluent was significantly lower under aeration conditions than under non-aeration conditions, and the concentration increased with increasing aeration rate.+ The lower the -N concentration, the better. Under the same aeration rate, the effluent NH4 under intermittent aeration conditions... + -N concentration is slightly higher than under continuous aeration conditions.

[0121] For summer water quality, aeration significantly affects the nitrogen removal efficiency of gravel bed reactors in the influent. However, under suitable conditions, gravel bed reactors are capable of removing 100% of NH4. + -N or NO3 - -N. In this experiment, under continuous aeration conditions, it was impossible to simultaneously meet the NH4+ requirement. + -N or NO3 - To achieve 100% removal of -N, the aeration conditions can only be controlled as much as possible to bring both to a relatively high value. The optimal conditions are continuous aeration with an air-to-water ratio of 1:3.

[0122] PO4 in different gravel filter reactors under different aeration conditions 3- -P concentration mean and removal rate mean as follows Figure 14 As shown in the figure. It can be seen from the figure that the PO4 levels between each gravel filter bed reactor are... 3- -P concentration changes show similar trends, but for PO4 3- The removal efficiency of PO4 varies depending on the concentration of -P, and the effect on PO4 removal also differs under different operating conditions. 3- The removal efficiency of -P concentration also varies. The effluent PO4 levels differ under operating conditions I, II, and III. 3- -P concentrations were all below 0.3 mg / L; effluent PO4 levels were below 0.3 mg / L under operating conditions IV, V, and VI. 3- -P concentrations were all below 0.2 mg / L. As the experiment progressed, the gravel filter reactor effectively reduced PO4 in the influent. 3- The slight increase in the removal rate of phosphorus-containing phosphorus indicates that the activity of microorganisms related to phosphorus removal in the gravel filter bed reactor is gradually enhanced.

[0123] In summary, the removal efficiency of various pollutants among the gravel filter reactors under different aeration conditions with different influent water quality is relatively small. Therefore, by observing the changes of pollutants along the flow path in each gravel filter reactor, this experiment aims to further understand the main functional areas inside the gravel filter reactor and compare the changes along the flow path among different gravel filter reactors.

[0124] The variation of TN concentration along the flow path in various gravel filter bed reactors under different operating conditions during winter and summer water intake is as follows: Figure 15 and 16As shown, calculations of the TN concentration along the flow path in each gravel filter reactor reveal that, under operating conditions 1, 2, 3, and 4, the average proportion of TN removed in the first 20 cm of the gravel filter reactor accounts for over 86% of the total TN removal. Furthermore, the data shows that under different operating conditions, the proportion of TN removed within the first 35 cm of each gravel filter reactor accounts for over 80.0% of the total TN removal, and in most cases, even exceeds 90.0%, primarily due to the action of the large number of microorganisms accumulated in the upstream section.

[0125] Example 6

[0126] Based on Example 5, the impact resistance test was conducted by increasing the water flow velocity and decreasing the hydraulic residence time to study the impact of hydraulic impact caused by runoff during rainstorms on GBF (gravel filter bed).

[0127] The water used for the impact resistance test shall be prepared according to the summer water quality as recorded in Table 3.

[0128] The main purpose of the impact resistance test is to explore the maximum flow velocity that can be achieved in the gravel filter bed reactor while ensuring that the effluent quality meets the standards. Given the large water consumption and the small differences between the various gravel filter bed reactors, this experiment only uses the No. 1 gravel filter bed reactor (100% crushed stone) as the research object. The specific impact resistance test conditions are shown in Table 7. The optimal operating condition for the maximum flow velocity in the gravel filter bed reactor is obtained through the impact resistance test.

[0129] Table 7 Impact Resistance Test Conditions

[0130]

[0131] During the shock resistance test, the nitrogen duration variation under different hydraulic residence times is as follows: Figure 17 As shown, the average nitrogen concentration in the effluent under different operating conditions is as follows: Figure 18 As shown, with the reduction of HRT (hydraulic retention time), the TN and NH4+ in the effluent from the gravel filter reactor decrease. + -N concentration showed an overall upward trend. When HRT ≤ 1.5h, the effluent TN concentration significantly exceeded the Class V surface water standard, but the effluent NH4 concentration was lower. + -N concentration can still meet the Class V surface water standard. Therefore, when it is necessary to ensure that the nitrogen concentration in the effluent meets the treatment requirements, the HRT should not be less than 1.5h, and the corresponding internal flow velocity of the GBF reactor is 1.72×10-4m / s.

[0132] During the impact resistance test, the changes in phosphate concentration over time at different hydraulic residence times are as follows: Figure 19 As shown in the figure, the average phosphate concentration in the effluent under different operating conditions is as follows: Figure 20 As shown, with the reduction of HRT (hydraulic retention time), the PO4 in the effluent from the gravel filter reactor...3- The overall concentration of phosphorus-containing phosphorus (PO4) showed a decreasing trend, mainly due to the large-scale enrichment of microorganisms related to phosphorus removal. Combined with previous continuous operation experiments, it is known that when a sufficient amount of microorganisms are enriched in the gravel filter reactor, the concentration of PO4 in the water is significantly reduced. 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%.

[0133] Example 7

[0134] The optimal gravel filter bed layout is selected by comprehensively considering factors such as filler type, filler particle size, gravel filter bed velocity, gravel filter bed flow rate, hydraulic retention time, aeration, and pollutant (water sample measurement index) variations along the course of the application. This means selecting the most suitable gravel filter bed layout for different river channels in the application area.

[0135] Based on the aforementioned continuous experiments, increased aeration has a good effect on the removal of nitrogen and COD from water. Therefore, in this embodiment, aeration facilities are considered to be installed in all gravel filter bed arrangements where aeration conditions are available; if artificial aeration is used, pipelines or equipment need to be laid, and power supply facilities are also required. To reduce operating and maintenance costs and simplify operation, the aeration method is proposed to be a natural cascade or a drop weir that does not require power.

[0136] Based on whether or not they undertake flood control tasks, rivers can be divided into two categories: one is flood control rivers that need to undertake flood control tasks, and the other is landscape rivers that do not need to undertake flood control tasks.

[0137] Rivers that need to carry out flood control generally have the following characteristics: (1) the flow rate differs greatly between the dry season and the flood season; (2) the flow rate is large and the velocity is fast during the flood season; (3) the amount of sediment in the river increases during flood control. Because these rivers are responsible for flood control, firstly, according to water conservancy requirements, it is not possible to arrange structures that affect flood control in the river; secondly, the flow rate is large during the flood season, making it impossible to introduce all the water into the gravel filter bed for treatment. Therefore, such rivers are suitable for a separated gravel filter bed arrangement, that is, the gravel filter bed is arranged outside the flood control 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.

[0138] Based on the water diversion method, it is divided into separate gravel filter beds with water diversion without dams and separate gravel filter beds with water diversion with dams.

[0139] Among them, such as Figure 21As shown, the damless water diversion separated gravel filter bed includes a water diversion channel 5 set on one side of the river. A waterfall 1 spans the river in the upstream section of the water diversion channel 5. The inlet of the water diversion channel 5 is equipped with a sand retaining wall 2, a debris barrier 3, and a gate 4 in sequence. The sand retaining wall 2 is located at the entrance where the water diversion channel 5 connects to the river and is connected to the side wall of the water diversion channel 5. The debris barrier 3 is located downstream of the sand retaining wall 2, and its two sides are connected to the side wall of the water diversion channel 5. The gate 4 is located downstream of the debris barrier 3 and is connected to the bottom plate and side wall of the water diversion channel 5. A gravel filter bed 6 is set at the outlet of the water diversion channel 5. The gravel filter bed 6 is filled with filler. The bottom of the gravel filter bed 6 is connected to the downstream section of the river through an outlet channel 7. If the longitudinal slope of the river is steep, the waterfall can be arranged naturally by utilizing the river drop. If the longitudinal slope of the river is gentle, a concrete or stone weir can be set up to raise the water level and form a waterfall.

[0140] Among them, such as Figure 22 As shown, for rivers with low flow rates and significant elevation differences between the water surface and the banks during the dry season, a dammed, separated gravel filter bed can raise the water level by using a weir and sluice gate, and then divert water upstream of the weir and sluice gate into the gravel filter bed. Specifically, this includes a water intake channel 5 located on one side of the river, a drop structure 5 spanning the river upstream of the intake channel 5, a dam 8 spanning the river upstream of the intake channel 5, and a sand-blocking sill 2, a debris screen 3, and a sluice gate sequentially installed at the inlet of the intake channel 5. Gate 4 and sand-blocking embankment 2 are located at the entrance where the water diversion channel 5 connects to the river channel and are connected to the sidewall of the water diversion channel 5. Trash grating 3 is located downstream of sand-blocking embankment 2, with both sides of the grating connected to the sidewall of the water diversion channel 5. Gate 4 is located downstream of trash grating 3, and is connected to the bottom plate and sidewall of the water diversion channel 5. A gravel filter bed 6 is installed at the outlet of the water inlet channel 5, filled with filler material. The bottom of the gravel filter bed 6 is connected to the downstream of the river channel via an outlet channel 7. If the river channel has a steep longitudinal slope, a natural waterfall can be constructed using the river channel drop; if the river channel has a gentler longitudinal slope, a concrete or stone weir can be constructed to raise the water level and form a waterfall.

[0141] Landscape rivers that do not serve flood control purposes have a stable water supply, low flow rate, and low sediment content. Therefore, gravel filter beds can be directly placed in the river channel, allowing all the river water to flow through the gravel filter bed for full-volume treatment, or a portion of the water can overflow from the top of the gravel bed while the rest enters the gravel bed for further treatment.

[0142] This includes gravel filter beds arranged directly transversely within the river channel and gravel filter beds arranged directly longitudinally within the river channel;

[0143] Among them, such as Figure 23As shown, when the width of the landscape river channel is relatively small, the gravel filter bed can be arranged directly transversely within the river channel. The specific structure for this transverse arrangement includes: a sedimentation tank 9, a waterfall 1, and a gravel filter bed 6 arranged sequentially within the river channel and along the water flow direction. A drainage channel 10 is located near the waterfall 1 and on the side closest to the riverbank of the sedimentation tank 9. A gate 4 is installed at the inlet of the drainage channel 10. The drainage channel 10 is arranged along the water flow direction and its length is not less than the distance from the outlet side of the sedimentation tank 9 to the outlet side of the gravel filter bed 6. One end of the gravel filter 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 ditch 10. In order to reduce the amount of sediment entering the downstream gravel filter bed, a sedimentation tank is first arranged upstream of the direct gravel filter bed. Considering that the height of the filter bed cannot be made too high when the gravel filter bed is directly arranged in the river channel, and in conjunction with the upstream sedimentation, the cascade is made of concrete or stone weir. After the water level is raised, a cascade is formed. In order to meet the requirements of the sedimentation tank and filter bed maintenance and emptying, a drainage ditch is arranged on the bank side, and a gate is arranged at the inlet of the drainage ditch.

[0144] Among them, such as Figure 24 As shown, the landscape river channel is relatively wide, allowing for a longitudinal arrangement of gravel filter beds within the channel, integrated with the landscape design. The specific structure of the gravel filter bed directly longitudinally within the channel includes: a sedimentation tank 9, a drop structure 1, and a gravel filter bed 6 arranged sequentially along the water flow direction. Several drainage gates 11 are installed on the gravel filter bed 6 along the water flow direction. The width of the gravel filter bed 6 is less than the width of the river channel and is arranged along the water flow direction. To reduce the amount of sediment entering the downstream gravel filter bed, a sedimentation tank is first arranged upstream for the direct gravel filter bed. The bottom of the sedimentation tank should be 0.5m to 1m lower than the riverbed, and its length should be 10m to 20m. Considering that the height of the gravel filter bed cannot be made too high when directly arranged in the river channel, and in conjunction with upstream sedimentation, this scheme uses a concrete or stone weir to raise the water level and form a drop structure. To meet the requirements for draining the filter bed during maintenance, drainage gates are arranged at intervals along the longitudinal direction of the filter bed.

Claims

1. A gravel filter bed process design method based on model experiments, characterized in that, The specific steps are as follows: Step 1: Conduct water quality monitoring in the application area and determine the water sample measurement indicators; Step 2: Obtain the biofilm from the gravel filter bed reactor used in the indoor test through in-situ biofilm attachment experiments to determine the packing material; The specific process of step 2 is as follows: Select fillers of different particle sizes in the application area and put them into multiple stainless steel mesh buckets. Then place the stainless steel mesh buckets in the water body of the application area. After on-site biofilm formation, peel off the biofilm attached to the surface of the filler and perform biofilm characterization and measurement. Based on the measurement results, determine the filler type and particle size. Step 3: Establish a hydrodynamic model of the application area to determine the flow velocity and flow rate of the gravel filter bed; The specific process of step 3 is as follows: import the application area plan into MIKE21 to establish information on the riverbank, riverbed depth, gravel filter inlet flow rate, and inlet and outlet water levels; build a MIKE 21 FM hydrodynamic model; simulate the water level and flow velocity of the water system in the application area using the MIKE 21 FM hydrodynamic model; and then obtain the flow rate of the gravel filter bed through the flow velocity and the flow area of ​​the gravel filter bed reactor. Step 4: Attach a biofilm to the gravel filter bed reactor, determine the experimental conditions of the gravel filter bed reactor and conduct a simulation experiment to obtain the concentration and flow characteristics of the water sample indicators. The specific process of step 4 is as follows: Step 4.1: Add the packing material specified in Step 2 to each of the multiple gravel filter bed reactors, or add one or two of the packing material specified in Step 2 and zeolite and volcanic rock, and run a peristaltic pump to deliver water to each gravel filter bed reactor, and adjust the flow rate of the peristaltic pump to ensure that the flow rate of each gravel filter bed reactor is constant. Step 4.2: Attach a biofilm to the gravel filter bed reactor; Step 4.3: Simulation experiments were conducted under different water quality, hydraulic retention time, aeration rate, aeration method, and number of operating days. The effluent water samples from the gravel filter reactor were measured periodically to obtain the concentration and flow characteristics of the water sample indicators under different operating conditions for each gravel filter reactor. Step 5: Conduct a shock resistance test to determine the maximum allowable flow rate of the gravel filter bed reactor under the condition that the effluent quality meets the standards; Step 6: Taking into account the type of filler, particle size of filler, gravel filter bed velocity, gravel filter bed flow rate, hydraulic retention time, aeration, and the variation characteristics of water sample test indicators along the process, select the optimal gravel filter bed layout suitable for different river channels in the application area.

2. The gravel filter bed process design method based on model experiments according to claim 1, characterized in that, In step 1, the water quality monitoring period is during summer and winter; Water sample testing indicators include NO 3 -N, NH4 + -N, TN, PO4 3 -P, TP, COD.

3. The gravel filter bed process design method based on model experiments according to claim 1, 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 start-up phase: Water samples containing bottom sediment collected in the application area are used as inoculation water. The biofilm sloughed off in step 2 is used as the inoculation source. The inoculation water and 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 each day. The water quality in the gravel filter bed reactor for different aeration days is measured. After the last day of aeration, all inoculation water is discharged from the gravel filter bed reactor. Then, an inoculation water and inoculation source of the same volume as the discharged inoculation water are added back to the gravel filter bed reactor. The above process is repeated. Continuous biofilm formation stage: After the last drainage of all inoculation water, artificial water is continuously added using a peristaltic pump until biofilm formation is successful.

4. The gravel filter bed process design method based on model experiments according to claim 3, characterized in that, In step 5, the impact resistance test is achieved by increasing the water flow velocity and reducing the hydraulic residence time.

5. The gravel filter bed process design method based on model experiments according to claim 4, characterized in that, In step 6, the gravel filter bed arrangement patterns for different river channels include: The first method is to use a separated gravel filter bed arrangement for rivers that need to carry out flood control tasks. That is, the gravel filter bed is placed outside the flood control area of ​​the river. A portion of the river water is introduced into the gravel filter bed for treatment and then returned to the river downstream. The second method involves placing gravel filter beds directly into rivers that do not require flood control, allowing all river water to flow through the gravel filter beds for full-volume treatment, or allowing some water to overflow from the top of the gravel filter beds while some water enters the gravel filter beds for further treatment.

6. The gravel filter bed process design method based on model experiments according to claim 5, characterized in that, For the first case: based on the water diversion method, it is divided into separate gravel filter beds with water diversion without a dam and separate gravel filter beds with water diversion with a dam; Among them, the damless water diversion separation gravel filter bed includes a water diversion channel (5) set on one side of the river channel. A waterfall (1) is arranged across the river channel upstream of the water diversion channel (5). The inlet of the water diversion channel (5) is provided with a sand retaining wall (2), a trash rack (3), and a gate (4) in sequence. The sand retaining wall (2) is arranged at the entrance where the water diversion channel (5) connects to the river channel and is connected to the side wall of the water diversion channel (5). The trash rack (3) is set downstream of the sand retaining wall (2). The two 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 diversion channel (5) is provided with a gravel filter bed (6). The gravel filter bed (6) is filled with filler. The bottom of the gravel filter bed (6) is connected to the downstream of the river channel through the outlet channel (7). Among them, the separated gravel filter bed with dam water diversion includes a water diversion channel (5) set on one side of the river channel, a waterfall (1) spanning the river channel is arranged in the upstream river channel of the water diversion channel (5), a dam (8) spanning the river channel is arranged in the upstream river channel of the water diversion channel (5), and a sand retaining wall (2), a debris barrier (3), and a gate (4) are arranged in sequence at the inlet of the water diversion channel (5). The sand retaining wall (2) is arranged at the entrance where the water diversion channel (5) connects to the river channel and is connected to the water diversion channel (5). The side walls are connected, the trash rack (3) is set downstream of the sand retaining wall (2), the two 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), the gate (4) is connected to the bottom plate and side walls of the water diversion channel (5), the outlet of the water diversion channel (5) is provided with a gravel filter bed (6), 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 through the outlet channel (7).

7. The gravel filter bed process design method based on model experiments according to claim 5, characterized in that, The second scenario includes gravel filter beds arranged horizontally directly within the river channel and gravel filter beds arranged vertically directly within the river channel. The structure of the gravel filter bed being arranged transversely in the river channel is as follows: a sedimentation tank (9), a waterfall (1), and a gravel filter bed (6) are arranged sequentially in the river channel and along the direction of water flow. A drainage ditch (10) is set up near the waterfall (1) and near the bank of the river channel in the sedimentation tank (9). The drainage ditch (10) is set up 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 sedimentation tank (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 ditch (10). The structure of the gravel filter bed being arranged longitudinally in the river channel is as follows: it includes a sedimentation tank (9), a drop (1), and a gravel filter bed (6) arranged sequentially in the river channel and along the direction of water flow. The gravel filter bed (6) is equipped with several 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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