A sand pool structure with high efficiency before sand leaving and after water flowing

Abstract

The application belongs to the technical field of grit chamber, and particularly relates to a high-efficiency grit chamber structure with sand left in front and water flow behind, which comprises a water inlet channel and a pool body. A water inlet groove is arranged on the front short slope of the pool body. A comb-tooth type water inlet is arranged on the side of the water inlet groove close to the pool body. A clear water pool is arranged on the back short slope of the pool body. A desilting passage is arranged on the middle part of one side of the long slope of the pool body. The water inlet channel is connected with the water inlet groove. A water distribution gate is arranged at the front end of the water inlet channel. The comb-tooth type water inlet is arranged on the water conservancy structure of the front pool, and the mechanical desilting slope is arranged on the slope of the grit chamber, so that the high-efficiency grit setting effect of sand left in front and water flow behind can be realized, and the cleaning of the silt is facilitated.

Description

Technical Field

[0001] This invention belongs to the field of sedimentation tank technology, specifically relating to a high-efficiency sedimentation tank structure with sand retention before water flow. Background Technology

[0002] The head sedimentation tank in drip irrigation systems is the first line of defense in drip irrigation networks, and the treatment of sediment in surface water sources has always been a primary research task in drip irrigation engineering. Commonly used head sedimentation tanks are strip-shaped, with rectangular or trapezoidal channels directly introducing water into the tank. However, when the water depth in the sedimentation tank is shallow, the inflow velocity is much greater than the inflow velocity, carrying suspended sediment to the end of the tank and into the drip irrigation network. This results in ineffective sedimentation, severe wear on the pump impeller, and frequent backwashing of the post-pump filter. Various solutions have been considered in the application of sedimentation tanks in drip irrigation projects, such as side-entry channels and the addition of sand-blocking embankments at the bottom of the tank, but the sedimentation effect remains insignificant. A large amount of sediment still enters the later part of the sedimentation tank and then the drip irrigation system, causing blockage of the drip tape.

[0003] Therefore, how to provide an efficient sedimentation tank structure that can improve the location of sediment deposition and facilitate sediment removal has become a problem that needs to be considered by those skilled in the art. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention discloses a high-efficiency sedimentation tank structure with sand retention before water flow. This invention achieves efficient sand settling by incorporating a comb-shaped inlet in the pre-sedimentation tank and a mechanical dredging ramp on the side slope of the sedimentation tank, thus facilitating the removal of sediment. Specifically, this invention discloses the following technical solutions:

[0005] A high-efficiency sedimentation tank structure with sand retention before water flow is provided. The front short slope of the tank body is provided with a water inlet channel, and the side of the water inlet channel near the tank body is provided with a comb-shaped water inlet. The rear short slope of the tank body is provided with a clear water tank. The middle of one side of the long slope of the tank body is provided with a sludge removal channel. The water inlet channel is connected to the water inlet channel, and a water diversion gate is provided at the front end of the water inlet channel.

[0006] Furthermore, the comb-shaped water inlet includes several overflow channels arranged at equal intervals, with the bottom end of the overflow channel located precisely at the top of the short front slope of the pool body.

[0007] Furthermore, concave grooves are provided on both sides of the overflow outlet, and primary filter grids are inserted into the concave grooves.

[0008] Furthermore, it also includes a secondary cleaning mechanism, which is located above the clear water tank.

[0009] Furthermore, the secondary cleaning mechanism includes a diversion wall, a support, an inclined flow guiding mechanism, and a V-shaped overflow collection trough. The diversion wall is located at the connection between the clear water tank and the tank body. The height difference between the top of the diversion wall and the overflow trough is 10cm. A water passage trough is provided below the diversion wall, and the height of the water passage trough is one-third of the tank body depth. The support is installed in the clear water tank. The inclined flow guiding mechanism and the V-shaped overflow collection trough are both located on the support. The inclined flow guiding mechanism is located on the back of the diversion wall, and the V-shaped overflow collection trough is located below the end of the inclined flow guiding mechanism.

[0010] Furthermore, it also includes a sand-blocking sill located in the water channel, wherein the height of the rear slope of the pool body is one-quarter of the depth of the pool body, and the sand-blocking sill is set at the top of the rear slope.

[0011] Furthermore, the inclined flow guiding mechanism is an inclined flow guiding plate, and baffles are provided on both sides of the flow guiding plate.

[0012] Furthermore, the inclined guide mechanism is an inclined conveyor belt.

[0013] Furthermore, a fine filter screen is installed inside the V-shaped collection trough.

[0014] Furthermore, a debris barrier is installed between the sand retaining wall and the diversion wall.

[0015] The beneficial effects of this invention are as follows:

[0016] 1. This invention, through adjustment of the inlet structure, completely alters the flow pattern of the incoming water, significantly improving the sedimentation effect. The comb-shaped inlet effectively reduces the inlet water velocity, achieving "inverse parabolic" physical sedimentation of suspended matter under hydraulic action. This results in sedimentation in the upstream 2 / 3 of the sedimentation tank, creating a highly efficient sedimentation effect of "sand retention before water flow," effectively settling sediment in the upstream section of the sedimentation tank. It treats suspended matter with a particle size greater than 0.05mm, reduces pump wear caused by sediment, lowers the likelihood of filter clogging caused by sediment, reduces pipe siltation, and extends the service life of drip irrigation facilities.

[0017] 2. This invention fully considers the size of the sedimentation tank and the influence of the guardrail. Instead of using machinery to directly dredge or hydraulically flush sand from the top of the tank, it sets up a mechanical dredging ramp on the side slope, and loaders enter the bottom of the tank to carry out dredging. The dredging efficiency is high and the dredging is clean and quick.

[0018] 3. The primary filter screen of this invention can perform primary filtration of floating objects in river water. The secondary cleaning mechanism can divert water flow and collect floating objects on the water surface. The detachable fine screen allows the trapped floating impurities to adhere to the surface of the fine screen for easy cleaning. Attached Figure Description

[0019] Figure 1 This is a top view of the present invention;

[0020] Figure 2 This is a schematic diagram of the water inlet tank of the present invention;

[0021] Figure 3 This is a schematic diagram of the installation of the primary filter grid in Embodiment 2 of the present invention;

[0022] Figure 4 This is a schematic diagram of the clear water tank and secondary cleaning mechanism in Embodiment 3 of the present invention;

[0023] Figure 5 This is a schematic diagram of the installation of the trash rack in Embodiment 5 of the present invention.

[0024] The components include: 1. Inlet channel; 2. Pool body; 3. Inlet trough; 4. Overflow outlet; 5. Clear water pool; 6. Diversion gate; 7. Concave trough; 8. Primary filter screen; 9. Sand retaining wall; 10. Diversion wall; 11. Support frame; 12. Inclined flow guiding mechanism; 13. V-shaped float collection trough; 14. Detachable fine mesh screen; 15. Dredging channel; and 16. Trash rack. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1

[0027] See attached document Figure 1-2 This embodiment discloses a high-efficiency sedimentation tank structure with sand retention before water flow and a sedimentation tank structure after water flow. It includes an inlet channel 1 and a tank body 2. An inlet trough 3 is provided on the front short slope of the tank body 2 for energy dissipation of the water flow. A comb-shaped inlet is provided on the side of the inlet trough 3 near the tank body 2. The comb-shaped inlet consists of several overflow troughs 4 spaced at equal intervals. The bottom of the overflow troughs 4 is located at the top of the front short slope of the tank body, used to disperse and concentrate the water flow, weiring the water into the sedimentation tank, thereby reducing the inflow velocity. A clear water tank 5 is provided on the rear short slope of the tank body 2. A sludge removal channel is provided in the middle of one side of the long slope of the tank body 2. The inlet channel 1 is connected to the inlet trough 3. A water diversion gate 6 is provided at the front end of the inlet channel 1 to control the inflow rate.

[0028] Specifically, taking the Weigan River water source of the Weigan River irrigation area in Shaya County as an example, the upstream Kizil Reservoir flushing, wind-blown sand entering the water along the river, the flood season of the river channel, and the natural river channel water conveyance will all bring a large amount of sediment to the drip irrigation water source. Therefore, how to set up a sedimentation tank, determine the size of the sedimentation tank, and control the sedimentation speed have become the primary tasks to consider for the drip irrigation system.

[0029] The average annual total sediment load of the Weigan River is 73.62 × 10⁻⁶. 4 The sediment transport volume during the four consecutive months of maximum sediment transport (June-September) accounted for 92.45% of the total suspended sediment transport volume, with a total annual sediment transport volume of 68.06 × 10⁻⁶. 4 t, a 50% guarantee rate is given when the total annual water volume of the river is 2.96 billion m³. 3 The average sediment content of the river channel is 2.3 kg / m³. 3 .

[0030] Based on the sediment content and particle size distribution of the Weigan River, the sedimentation calculation methods in the "Drip Irrigation Engineering Design Atlas" and "Water Conservancy and Hydropower Engineering Sedimentation Tank Design" were used to calculate the sedimentation effect. After comparison, the appropriate sedimentation tank size was determined to ensure a better sedimentation effect.

[0031] 1. Determination of parameters for grit chamber

[0032] (1) Surface loading rate:

[0033] Surface loading rate refers to the water production per unit surface area of ​​a grit chamber. It is calculated using the following formula:

[0034] V0 = Q / A

[0035] Where: V0—surface loading rate, m / h;

[0036] Q – Design flow, m 3 / s;

[0037] Ac – Surface area of ​​the sedimentation tank, m² 2 .

[0038] The "Technical Specification for Micro-irrigation Engineering" stipulates that the surface loading rate of the grit chamber should not exceed 3.0 mm / s. The specific value should be selected according to the water quality of the canal and the water quality requirements of the drip irrigation system, with V0 = 0.72 to 7.2 m / h. The value of 0.72 is adopted in this design.

[0039] (2) Horizontal flow velocity: Increasing the horizontal flow velocity in the sedimentation tank increases the Reynolds number (Re), which is not conducive to the settling of sediment particles. On the other hand, it increases the Fr number (Fr), which increases the stability of the water flow and is beneficial to improving the sedimentation effect. Based on experience, the design velocity is 36 m / h.

[0040] (3) Retention time: The retention time in the grit chamber should take into account the water quality of the canal and the water quality requirements of the drippers. Based on operational experience, T is adopted.停留 = 1~3h. T is determined based on the flow rate. 停留 =2.0h.

[0041] 2. Calculation of parameters for grit chamber

[0042] The sedimentation tank has a trapezoidal cross-section, and the sediment content of the project's water source is 2.3 kg / m³. 3 The sedimentation tank is mainly composed of fine sand with moderate organic matter content. This sedimentation tank design includes two types: a dual-system and a single-system. The dual-system design involves two inlet sections sharing a single sedimentation tank (maximum flow rate 790.27 m³ / h). 3 / h), a single system uses one head section with one grit chamber (maximum flow rate 435.6 m³ / h). 3 / h).

[0043] (1) Determining the size of the sedimentation tank

[0044] ① Surface area of ​​sedimentation tank

[0045] A 沉砂池 =Q / v0

[0046] A 沉砂池 —Surface area of ​​sedimentation tank (m²) 2 ,

[0047] Q 并 —Design flow rate 790.27m³ 3 / h,

[0048] Q 单 —Design flow rate 435.6m³ 3 / h,

[0049] v0—Surface loading rate, taken as 0.72 m / h

[0050] The calculated surface area of ​​the sedimentation tank is A. 并＝ 1094.22m 2 A 单 =603m 2 .

[0051] ② Length of sedimentation tank

[0052] L 沉砂池 =vT 停留

[0053] L 沉砂池 —Length of the sedimentation tank (m);

[0054] v—Horizontal flow velocity 36m / h;

[0055] T 停留 —The stay time is set at 2.0 hours.

[0056] The calculated length of the sedimentation tank is 72m. Since the flow rate of the single and double systems differs by about 1 time and the flow velocity also differs greatly, the initial design of this sedimentation tank is to select the length of the sedimentation tank as Ldouble = 120m and Lsing = 70m respectively.

[0057] ③ Average width of sedimentation tank

[0058]

[0059] B 沉砂池 —Average width of the sedimentation tank;

[0060] A 沉砂池 — Surface area of ​​the sedimentation tank, m² 2 ;

[0061] L 沉砂池 —Length of the sedimentation tank, in meters;

[0062] The calculated width of the sedimentation tank is B. 并 = 9.11m, design value is 12m; B 单 =8.6m, the design is 9m.

[0063] ④ Sedimentation tank (effective) water depth

[0064]

[0065] H1—Effective water depth of the sedimentation tank (m),

[0066] Q—Design flow rate, m 3 / h;

[0067] T 停留 —Duration of stay: 2 hours;

[0068] A 沉砂池 — Surface area of ​​the sedimentation tank, m² 2 ;

[0069] The effective water depth of the sedimentation tank is calculated to be 1.44m.

[0070] ⑤ Depth of mud storage area

[0071]

[0072] H2—Depth of the mud storage area (m);

[0073] Q—Design flow rate, m 3 / h;

[0074] C0—The concentration of sediment with particle sizes of 1 kg / m³ or larger in the water entering the grit chamber. 3 ;

[0075] T—Irrigation cycle for drip irrigation, 100 hours;

[0076] γ—Bulk density of sediment, 1780 kg / m³ 3 ;

[0077] A 沉砂池 — Surface area of ​​the sedimentation tank, m² 2 ;

[0078] The calculated depth of the mud storage area is H. 并 =0.041m, and each irrigation cycle involves approximately 14 irrigations, so the mud depth within the irrigation cycle is 0.57m.

[0079] ⑥ Depth of sedimentation tank

[0080] H3=H1+H2+Δ

[0081] H3—Depth of the grit chamber (m)

[0082] H1—Sedimentation tank (effective) water depth 1.44m,

[0083] H2—Deep area of ​​the mud storage zone: 0.57m.

[0084] Δ—Safe extra height 0.4m,

[0085] The calculated depth of the sedimentation tank is 2.41m, but the design depth is 2.5m.

[0086] (2) Hydraulic condition verification of sedimentation tank

[0087] ① Cross-sectional area of ​​water passage

[0088] ω=B 沉砂池 H1

[0089] B 沉砂池 —Average width of the sedimentation tank, in meters.

[0090] ω — cross-sectional area of ​​the water passage (m²) 2 ,

[0091] H1—Effective water depth of the sedimentation tank, in meters.

[0092] The cross-sectional area of ​​the water passage is ω 并 =17.33m 2 ω 单 =13m 2 .

[0093] ②Hydraulic wetted perimeter

[0094] The hydraulic wetted perimeter is X 并 =17.05m, X 单 =14.05m.

[0095] ③ Hydraulic radius

[0096] R 水 =ω / X

[0097] The hydraulic radius is R 并 =1.02m, R 单 =0.93m.

[0098] The hydraulic conditions have been verified as follows:

[0099] ④ Reynolds number

[0100] Re = vR / r

[0101] Reynolds number

[0102] v—Horizontal flow velocity 0.001 m / s,

[0103] R—hydraulic radius

[0104] r—the kinematic viscosity of water, 1.01 × 10⁻⁶ -6 ,

[0105] The Reynolds number is calculated to be R. e并 =220986, R e单 =110866, all greater than 500, indicating turbulence.

[0106] ⑤Froude number

[0107] Fr = v 2 / Rg

[0108] Fr—Froude number,

[0109] v—Horizontal flow velocity 0.001 m / s,

[0110] R—hydraulic radius, m

[0111] g—gravitational acceleration 9.8 m / s² 2 ,

[0112] The calculated Froude number is Fr. 并 =4.8×10 -3 ,Fr 单 =1.6×10 -4 greater than 10 -5 This meets the requirements for stable water flow.

[0113] (3) Calculation conclusions

[0114] After trial calculations, the length of the sedimentation tank is taken as L. 并 =120m, L 单 =70m, average bottom width of the pool is taken as B 并 =12m, B 单 =9m, slope coefficient 1:1.75, pool depth is 2.5m.

[0115] The grit chamber is designed with a concrete trapezoidal cross-section structure. The size of the grit chamber is selected according to the flow rate of the drip irrigation system. Specifically, the size of the grit chamber for the combined system is length × width × height = 120 × 12 × 2.5m, and the size of the single system is 70 × 9 × 2.5m.

[0116] 3. Analysis using relevant methods from the "Design Code for Sedimentation Basins in Water Conservancy and Hydropower Projects" (SL / T269-2019)

[0117] Based on the relevant calculation methods and formulas in this specification, and considering the actual conditions of this project, the sedimentation tank is designed to have a sedimentation rate of no less than 85% for sediment particles with a diameter greater than 0.05 mm. Sediment parameters remain the same as before.

[0118] (1) Inlet water depth of the working section

[0119]

[0120] In the formula: H—inlet water depth of the working section (m);

[0121] Z—Difference between the inlet water level of the working section and the natural river channel water level at the outlet of the sediment discharge channel (m);

[0122] q—the velocity of the flushing flow at the outlet of the sand discharge channel (m / s);

[0123] υc—Desand flushing velocity at the outlet of the sand discharge channel (m / s);

[0124] i—The bottom slope of the working section of the sedimentation tank;

[0125] Lw—Length of the working section of the sedimentation tank (m), including the length of the overflow weir area for periodically flushed sedimentation tanks in water conservancy projects;

[0126] io—bottom slope of the sand-drainage channel;

[0127] Lo—Length of the sand-drainage channel;

[0128] (2) The working depth at the inlet of the working section is calculated using the following formula:

[0129] H e =H-△H k

[0130] Where: He—working depth at the inlet of the working section (m);

[0131] Hk—Design siltation thickness at the inlet of the working section (m). In the initial design, the sedimentation tank for periodic flushing in water conservancy projects can be selected as (0.5--0.6)H; in this case, 0.5H is taken.

[0132] (3) Calculation of working width

[0133] The working width is calculated using the following formula:

[0134]

[0135] Where: Q—Working flow rate (m³) 3 / s);

[0136] v—average flow velocity of the working section (m / s). In the initial design, when the minimum particle size of sediment in the sedimentation tank is 0.05mm, the average flow velocity is taken as 0.05m / s.

[0137] Hw—Average working depth (m);

[0138] (4) Calculation of settling velocity of suspended sediment

[0139] For the portion with a particle size less than 0.062 mm, sedimentation analysis is used; for the portion with a particle size greater than 0.062 mm, the suspended particle size distribution obtained by sieve analysis is used, and the settling velocity of each particle size is calculated using the following formula.

[0140] When the particle size is equal to or less than 0.062 mm, the Stokes formula is used for calculation:

[0141]

[0142] When the particle size is 0.062–2.0 mm, the settling velocity formula for natural sand from Shayuqing is used for calculation:

[0143]

[0144] (lgSa+3.790) 2 +(lgψ-5.777) 2 =39.0

[0145] When the particle size is greater than 2.0 mm, the settling velocity formula in the turbulent zone of the sand and jade is used for calculation:

[0146]

[0147] In the above formulas, υ represents the kinematic viscosity of water (cm). 2 / s);

[0148] t — water temperature (°C);

[0149] d—Sediment particle size (mm);

[0150] ρ s —Density of sediment (g / cm³) 3 )

[0151] ρ w —Density of clean water (g / cm³) 3 );

[0152] ω—sediment settling velocity (cm / s);

[0153] g—acceleration due to gravity (cm / s²) 2 );

[0154] S a —Sinking speed determination;

[0155] ψ—Particle size criterion;

[0156] The average settling velocity of a particle size group is the geometric mean of the settling velocities of its upper and lower limits:

[0157]

[0158] In the formula —Average settling velocity of particle size group (cm / s);

[0159] ω i —Settling velocity of the lower limit of particle size group (cm / s);

[0160] ω i+1 —Settling velocity of the upper limit of the particle size group (cm / s);

[0161] (5) Sediment Settlement Calculation

[0162] The working depth and sediment thickness of the sedimentation tank vary along the course of the sedimentation process. Therefore, the sedimentation tank should be divided into n calculation sections, and the water surface line should be calculated from downstream to upstream using the following formula:

[0163]

[0164] In the formula: L k —k Pool section length (m);

[0165] H k H k+1—k Water depth (m) at the upper and lower cross sections of the pool section;

[0166] v k v k+1—k Flow velocity (m) at the upper and lower cross sections of the pool section;

[0167] i k —Longitudinal slope of the bed surface in section k;

[0168] —average hydraulic gradient of pool section k;

[0169] g—acceleration due to gravity (m / s²) 2 );

[0170] —average flow velocity in pool section k (m / s);

[0171] R k R k+1 —Hydraulic radii (m) of the upper and lower sections of the k-section;

[0172] —The average hydraulic radius of the k-section (m);

[0173] —average Chey coefficient for pool segment k;

[0174] n—roughness coefficient, which is generally the same for all sections of the pool, and is taken as 0.025 in the design.

[0175] k—Pool section number, ordered from the inlet of the working section to the end of the pool or the beginning of the overflow weir area, k = 1, 2, ..., n.

[0176] (6) Settlement ratio calculation

[0177] The sediment concentration changes of each calculation section, the sedimentation rate of each section, the sedimentation rate of the whole pool, and the sedimentation rate of particles larger than a certain size are calculated from upstream to downstream.

[0178] ① The change in sediment content in the lower cross section of the pool is calculated using the following formula.

[0179]

[0180] In the formula S ik S i(k+1) —Sediment content (kg / m³) of upper and lower cross sections of pool k 3 );

[0181] α ik —Recovery saturation coefficient of particle size group in pool k;

[0182] —Average settling velocity of particle size group (m / s);

[0183] q k —k pool section unit width flow rate [m 3 / (s﹒m)];

[0184] i — Particle size group number, sorted from smallest to largest, i = 1, 2, ..., m.

[0185] ② The settling rate of each pool section is calculated using the following formula:

[0186]

[0187] In the formula η ik —Settlement rate of particle size group i in pool section k.

[0188] ③ The settling rate of the entire pool groups is calculated using the following formula:

[0189] When the working section has no inlet trough (overflow weir area)

[0190]

[0191] In the formula η i —Settling rate of the i-sized particle group in the whole pool.

[0192] ④ Percentage of the weight of the i-th particle size group of silt accumulated in the sedimentation tank (%).

[0193]

[0194] In the formula, △P di —Percentage (%) of the weight of the i-th particle size group of sediment in the sedimentation tank or in the water flow of the corridor or discharge hole.

[0195] ⑤ Calculation results

[0196] Based on the above formula, the grit chamber is calculated in segments, and the design parameters and results are as follows.

[0197] Design Parameter Table

[0198]

[0199]

[0200] Sand settling effect table

[0201] project Shared sedimentation tank single pool The sand content at the outlet of the pond is 0.008131 0.003926 Overall sedimentation rate 0.996465 0.998293 Sedimentation rate of particles larger than 0.05 mm 0.988741 0.994564

[0202] Different cross-sectional sediment volumes and thicknesses

[0203]

[0204] This method was used to verify the sedimentation effect of a sedimentation tank with a determined size. The sedimentation rate of 0.05mm particle size sediment was 99.4%, the total sedimentation rate was 99.8%, and the sand content at the outlet was 0.0081kg / m³. 3 This meets the requirements of drip irrigation equipment for sediment particle size.

[0205] in conclusion

[0206] 1. Through calculation, analysis, and comparative verification using two methods, the design flow rate of the grit chamber is determined to be 0.22 m³ / h. 3 When the flow rate is 0.12 m³ / s, the dimensions of the grit chamber are: length × width × height = 120 × 12 × 2.5 m; the design flow rate of the grit chamber is 0.12 m³ / s. 3 When the flow rate is 1 / s, the dimensions of the sedimentation tank are: length × width × height = 70 × 9 × 2.5m.

[0207] 2. When the water flow velocity in the sedimentation tank is controlled at 36m / h, the sedimentation effect is better.

[0208] 3. The comb-tooth structure of this invention increases the inlet width from the conventional 50cm to about 9.5m, reduces the water depth from 26cm to 6cm, and reduces the flow velocity to about 0.33m / s. The inlet flow velocity and the sedimentation flow velocity are perfectly combined, and the sedimentation and accumulation of silt in the water are parabolic. This achieves the effect of sediment settling in the first 2 / 3 of the pool, and clear water enters the drip irrigation system after passing through the last 1 / 3 of the sedimentation tank, thus achieving effective sedimentation.

[0209] Example 2

[0210] See attached document Figure 2-3 In order to clean up floating objects in the water flow, concave grooves 7 are provided on both sides of the overflow outlet 4. A primary filter screen 8 is inserted into the concave groove 7. The primary filter screen 8 can filter aquatic plants, organic matter or other suspended impurities in the water flow to avoid clogging the outlet pipe of the clear water pool 5.

[0211] Example 3

[0212] See attached document Figure 4 Since the primary filter screen 8 can only clean large-sized organic matter and impurities, and if the primary filter screen 8 is set too densely, it will easily cause blockage of the overflow channel 4 and affect the sedimentation of silt. Therefore, in order to further clean the floating objects on the surface of the river, this embodiment also includes a secondary cleaning mechanism.

[0213] Specifically, the secondary cleaning mechanism is located above the clear water tank 5. The secondary cleaning mechanism includes a diversion wall 10, a support 11, an inclined flow guiding mechanism 12, and a V-shaped overflow collection trough 13. The height difference between the top of the diversion wall 10 and the overflow trough 4 is 10cm. A water passage trough is provided below the diversion wall 10. The height of the water passage trough is one-third of the tank depth. A sand retainer 9 is also provided in the water passage trough. The height of the rear slope of the tank 2 is one-quarter of the tank depth. The sand retainer 9 is located at the top of the rear slope.

[0214] The bracket 11 is installed in the clear water tank 5. The inclined flow guiding mechanism 12 and the V-shaped float collection trough 13 are both set on the bracket 11. The inclined flow guiding mechanism 12 is set on the back of the diversion wall 10. In this embodiment, the inclined flow guiding mechanism 12 is an inclined flow guiding plate. Baffles are provided on both sides of the flow guiding plate. The V-shaped float collection trough 13 is set below the end of the inclined flow guiding mechanism 12. Insertion holes are provided on both sides of the V-shaped float collection trough 13. A detachable fine mesh grid 14 is inserted into the insertion hole. In this invention, the surface of the detachable fine mesh grid 14 is provided with a handle, which can be removed by pulling it outward.

[0215] The inclined flow guiding mechanism 12 and the V-shaped floating trough 13 of the present invention can basically cover the top of the clear water pool, preventing impurities blown by the wind from falling into the clear water pool. When the water flows through the diversion wall 10, the bottom clear water flows from the water channel to the clear water pool 5. The floating objects pass over the diversion wall 10 with the surface water and flow through the guide plate. Under the push of the water flow, the floating objects are pushed to the V-shaped floating trough 13 by the guide plate and intercepted on the detachable fine mesh grid 14 of the V-shaped floating trough 13. The water flows along the V-shaped floating trough 13 into the clear water pool 5. The detachable fine mesh grid 14 facilitates the drying and cleaning of the floating objects.

[0216] Example 4

[0217] The difference between this embodiment and embodiment 3 is that in this embodiment, the inclined guide mechanism 12 is an inclined conveyor belt. By setting the conveyor belt, floating impurities are actively transported to the V-shaped floating trough 13, which further improves the collection speed of floating objects.

[0218] Example 5

[0219] See attached document Figure 5 When the water flow rate is too slow, in order to avoid the accumulation of silt and floating objects from the river water in the inlet trough 3, and the water level in the pool 2 cannot reach the upper surface of the diversion wall 10 so that the water cannot be diverted (for example, the water flow in the pool is only half), the primary filter grid 8 is no longer set in this embodiment. Instead, a debris barrier 16 is vertically set between the diversion wall 10 and the sand barrier 9 in embodiment 3 to prevent larger impurities in the water from entering the clear water pool.

[0220] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A sand pool structure before sand leaving and after water flowing, characterized in that, The water inlet channel and the pool body are included, the front short slope of the pool body is provided with a water inlet groove, the water inlet groove is provided with a comb tooth type water inlet near one side of the pool body, the rear short slope of the pool body is provided with a clean water pool, the middle part of the long slope side of the pool body is provided with a dredging channel, the water inlet channel is communicated with the water inlet groove, and the front end of the water inlet channel is provided with a water distribution gate. The secondary sewage cleaning mechanism is further included and is arranged above the clean water pool; the secondary sewage cleaning mechanism includes a flow distribution low wall, a support, an inclined flow guide mechanism and a V-shaped floating collection groove, the flow distribution low wall is arranged at the connection between the clean water pool and the pool body, the height difference between the top end of the flow distribution low wall and the overflow groove is 10 cm, the flow distribution low wall is provided below with a water passing groove, the height of the water passing groove is one third of the depth of the pool body, the support is installed in the clean water pool, the inclined flow guide mechanism and the V-shaped floating collection groove are arranged on the support, the inclined flow guide mechanism is arranged at the back of the flow distribution low wall, and the V-shaped floating collection groove is arranged below the end of the inclined flow guide mechanism.

2. The sand pre-remaining and water post-flowing high-efficiency grit chamber structure according to claim 1, characterized in that, The comb tooth type water inlet includes a plurality of overflow grooves arranged at equal intervals, and the bottom end of the overflow groove is just located at the top of the front short slope of the pool body.

3. The sand pre-remaining and water post-flowing high-efficiency grit chamber structure according to claim 2, characterized in that, Both sides of the overflow groove are provided with recessed grooves, and the primary filter grating is inserted into the recessed groove.

4. The sand pre-remaining and water post-flowing high-efficiency grit chamber structure according to claim 1, characterized in that, The sand blocking ridge in the water passing groove is further included, the height of the rear slope of the pool body is one fourth of the depth of the pool body, and the sand blocking ridge is arranged at the top of the rear slope.

5. The sand pre-remaining and water post-flowing high-efficiency grit chamber structure according to claim 1, characterized in that, The inclined flow guide mechanism is an inclined flow guide plate, and the both sides of the flow guide plate are provided with baffle plates.

6. The sand pre-remaining and water post-flowing high-efficiency grit chamber structure according to claim 1, characterized in that, The inclined flow guide mechanism is an inclined conveying belt.

7. The sand pre-remaining and water post-flowing high-efficiency grit chamber structure according to claim 1, characterized in that, The V-shaped floating collection groove is provided with a detachable fine grid inside.

8. The sand pre-remaining and water post-flowing high-efficiency grit chamber structure according to claim 4, characterized in that, The trash screen is arranged between the sand blocking ridge and the flow distribution low wall.

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