Multi-stage linkage water quality purification treatment method for drainage basin treatment

Abstract

The invention relates to the technical field of water treatment, and discloses a multi-stage linkage water quality purification treatment method for drainage basin treatment, which comprises the following steps: reducing the flow rate of drainage basin runoff entering a pretreatment pool by using a stepped energy dissipation ridge; an overflow weir is arranged between the pretreatment pool and the biochemical purification unit, runoff with the flow lower than a threshold value is guided to the biochemical purification unit according to a water level pressure head, and excessive flow is guided to a bank zone ecological buffer zone; enabling the runoff to sequentially flow through the anaerobic biological filter tank and the aerobic ecological tank, and generating gravity flow by utilizing a unit elevation difference; according to the invention, the self-adaptive flow distribution is realized by utilizing a water level physical signal, the scouring stripping of a microbial film of a biochemical unit by a dynamic load is effectively prevented, and the stability of the effluent quality of the system is maintained through kinetic energy level conversion.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and more specifically, to a multi-stage coordinated water purification and treatment method for watershed management. Background Technology

[0002] In current small watershed management projects in the hilly areas of southern China, the purification of non-point source pollution often employs structures such as constructed wetlands, anaerobic biological ponds, and ecological buffer zones. These purification units work together to remove chemical oxygen demand, ammonia nitrogen, and total phosphorus from the water through mechanisms such as matrix filtration, microbial degradation, and plant absorption. In the conventional design of this type of purification process, the hydraulic retention time and the stability of the biofilm directly determine the purification efficiency, and it achieves the expected treatment effect under a stable hydraulic load environment.

[0003] However, the hilly terrain in southern China has a steep slope, resulting in a short runoff confluence time and causing extremely drastic fluctuations in water level and flow rate for treatment facilities. Traditional fixed purification units, when faced with the instantaneous high hydraulic load caused by heavy rainfall, experience shear forces in their internal flow field that trigger biofilm stripping. Existing technologies reduce inflow velocity by optimizing the geometry of energy dissipation structures. For example, Chinese utility model patent CN204875720U discloses a discontinuous, low-sill, stepped energy dissipation structure for spillways or chutes. This structure uses discontinuous steps at intervals on the bottom plate to reduce discharge energy, and the actual hydraulic residence time is significantly reduced as the flow velocity increases. Biochemical reactions cannot cover pollutant loads. During dry seasons with low flow rates, the weakening of water flow dynamics causes stagnation in the water within the biochemical unit. Insufficient dissolved oxygen replenishment can even lead to anaerobic odor and disrupt the balance of the ecosystem. To cope with such fluctuating loads, existing improvement strategies typically employ redundant designs that expand the tank volume or install electric gates and sensor control systems. While expanding the volume increases the system's hydraulic buffering capacity, it does not solve the physical limitations of dead zones and flow field imbalances, and it also increases infrastructure costs. Furthermore, automated control equipment that relies on external power faces challenges such as inconvenient maintenance and unstable power supply in hilly and rural areas.

[0004] Therefore, how to construct a method that can spontaneously adjust the purification path according to water level fluctuations and realize real-time coupling between the topology of the treatment unit and the dynamic hydraulic load has become the technical problem to be solved by this invention. Summary of the Invention

[0005] This invention provides a multi-stage coordinated water purification and treatment method for watershed management, comprising the following steps:

[0006] Step S1: The watershed runoff is introduced into the pretreatment pool. The stepped energy dissipation sills set in the pretreatment pool are used to reduce the inflow velocity of the watershed runoff and to intercept floating objects and sediment in the watershed runoff.

[0007] Step S2: An overflow weir is set at the connection between the pretreatment tank and the biochemical purification unit. Based on the water level head in the pretreatment tank, the overflow weir directs watershed runoff with a flow rate below the flow rate threshold to the biochemical purification unit, and directs watershed runoff with a flow rate exceeding the flow rate threshold to the riparian ecological buffer zone. The weir crest elevation is set according to the rated inflow of the biochemical purification unit, and the flow rate threshold is determined by the difference between the weir crest elevation and the bottom elevation of the pretreatment tank.

[0008] Step S3: The watershed runoff entering the biochemical purification unit is sequentially introduced into the anaerobic biological filter and the aerobic ecological pond. The elevation difference between the anaerobic biological filter and the aerobic ecological pond is used to generate gravity flow of fluid, and the watershed runoff is brought into contact with the biological substrate in the anaerobic biological filter and the aquatic plants in the aerobic ecological pond, respectively.

[0009] Step S4: Drainage from the aerobic ecological pond is directed to the end multi-layered ecological buffer zone, and the drainage resistance is increased by the graded filler layer in the end multi-layered ecological buffer zone.

[0010] Preferably, in step S2, the overflow weir is set at the inlet of the biochemical purification unit, and the flow rate entering the biochemical purification unit is determined by the relative difference between the weir crest elevation and the water level in the pretreatment tank.

[0011] Preferably, in step S3, the specific surface area of ​​the biological substrate filling the anaerobic biological filter is not less than 200 m². 2 / m 3 Emergent plants are planted in the aerobic ecological pond, and the roots of the aquatic plants are covered with microbial films.

[0012] Preferably, the hydraulic retention time in the aerobic ecological pond is determined by the following formula: T = V / Q, where T is the hydraulic retention time, V is the volume of the aerobic ecological pond, and Q is the real-time flow rate entering the aerobic ecological pond; the hydraulic retention time is controlled at 4 hours through the physical diversion effect of the overflow weir. above.

[0013] Preferably, in step S1, the height of the stepped energy dissipation embankment is determined according to the river slope of the watershed, and the number of stepped energy dissipation embankments is 3 to 5.

[0014] Preferably, in step S4, the terminal multilayered ecological buffer zone consists of an emergent plant area, a submerged plant area, and a gravel damping layer; the porosity of the gravel damping layer is 30% to 45%.

[0015] Preferably, step S1 further includes: setting a sedimentation hopper at the effluent end of the pretreatment tank, and using gravity to allow the sand and gravel in the runoff to settle to the bottom of the sedimentation hopper.

[0016] Preferably, the biochemical purification unit is equipped with a flow guide baffle, the angle between the flow guide baffle and the horizontal plane is 30 degrees to 60 degrees, and the flow guide baffle forms an S-shaped flow path of watershed runoff in the biochemical purification unit.

[0017] Preferably, the top of the anaerobic biological filter is provided with a light-shielding cover, and the light-shielding cover covers the entire liquid surface of the anaerobic biological filter.

[0018] Preferably, it also includes: setting a water level regulating well at the outlet of the terminal multi-layered ecological buffer zone, and changing the operating water level height in the biochemical purification unit by the number of weir plates in the water level regulating well.

[0019] The embodiments of the present invention have at least the following beneficial effects:

[0020] 1. In multi-stage linkage water purification and treatment, by setting up flow channel nodes with gradient differences, the purification process can undergo phased path migration with water level fluctuations, realizing dynamic adaptation of the treatment unit topology and instantaneous pollution load. Traditional treatment facilities are limited by fixed volume and constant flow direction, which can cause short-flow or overflow problems when facing high-intensity runoff impacts. This invention utilizes a multi-stage linkage mechanism triggered by water level signals to enable water flow to automatically enter the corresponding biochemical reaction sequence at different pollution concentrations, ensuring the coordination and consistency between treatment depth and load fluctuations.

[0021] 2. The purification method utilizes the hydraulic resistance path constructed by vegetated swales and wetland fillers to cause the effective biochemical reaction area of ​​the water to expand non-linearly with the rise of the water level, compensating for the loss of hydraulic residence time under high flow rate conditions; the physical linkage mechanism ensures that the microbial community has sufficient contact reaction time under extreme flow conditions, avoiding repeated effluent quality changes caused by insufficient residence time in the purification process, and improving the output stability of the treatment system under all time-domain conditions.

[0022] 3. By combining the energy dissipation structure at the diversion outlet with the terminal multi-layered ecological buffer zone, the kinetic energy gradient is transformed in stages to reduce the stripping and damage of the biofilm in the biochemical core unit caused by water flow scouring; by utilizing the guiding effect of the physical diversion node, the excessive hydraulic load is guided to the shoreline area with high scouring resistance, thereby achieving in-situ protection of the reaction environment such as the internal anaerobic biological filter, and maintaining the structural integrity and functional continuity of the system under complex hydrological conditions. Attached Figure Description

[0023] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings, in which several embodiments of the invention are illustrated by way of example and not limitation, wherein:

[0024] Figure 1 This is a flowchart illustrating the multi-stage linkage process of water purification in this invention.

[0025] Figure 2 This is a diagram of the core structural elements of the multi-level linkage processing system of the present invention. Detailed Implementation

[0026] The principles and spirit of the present invention will now be described with reference to several exemplary embodiments in conjunction with the accompanying drawings. It should be understood that these embodiments are provided merely to enable those skilled in the art to better understand and implement the present invention, and are not intended to limit the scope of the present invention in any way. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0027] A multi-stage coordinated water purification and treatment method for watershed management includes the following steps:

[0028] Step S1: The watershed runoff is introduced into the pretreatment pool. The stepped energy dissipation sills set in the pretreatment pool are used to reduce the inflow velocity of the watershed runoff and to intercept floating objects and sediment in the watershed runoff.

[0029] Step S2: An overflow weir is set at the connection between the pretreatment tank and the biochemical purification unit. Based on the water level head in the pretreatment tank, the overflow weir directs watershed runoff with a flow rate below the flow rate threshold to the biochemical purification unit, and directs watershed runoff with a flow rate exceeding the flow rate threshold to the riparian ecological buffer zone. The weir crest elevation is set according to the rated inflow of the biochemical purification unit, and the flow rate threshold is determined by the difference between the weir crest elevation and the bottom elevation of the pretreatment tank.

[0030] Step S3: The watershed runoff entering the biochemical purification unit is sequentially introduced into the anaerobic biological filter and the aerobic ecological pond. The elevation difference between the anaerobic biological filter and the aerobic ecological pond is used to generate gravity flow of fluid, and the watershed runoff is brought into contact with the biological substrate in the anaerobic biological filter and the aquatic plants in the aerobic ecological pond, respectively.

[0031] Step S4: Drainage from the aerobic ecological pond is directed to the end multi-layered ecological buffer zone, and the drainage resistance is increased by the graded filler layer in the end multi-layered ecological buffer zone.

[0032] Preferably, in step S2, the overflow weir is set at the inlet of the biochemical purification unit, and the flow rate entering the biochemical purification unit is determined by the relative difference between the weir crest elevation and the water level in the pretreatment tank.

[0033] Preferably, in step S3, the specific surface area of ​​the biological substrate filling the anaerobic biological filter is not less than 200 m². 2 / m 3 Emergent plants are planted in the aerobic ecological pond, and the roots of the aquatic plants are covered with microbial films.

[0034] Preferably, the hydraulic retention time in the aerobic ecological pond is determined by the following formula: T = V / Q, where T is the hydraulic retention time, V is the volume of the aerobic ecological pond, and Q is the real-time flow rate entering the aerobic ecological pond; the hydraulic retention time is controlled at 4 hours through the physical diversion effect of the overflow weir. above.

[0035] Preferably, in step S1, the height of the stepped energy dissipation embankment is determined according to the river slope of the watershed, and the number of stepped energy dissipation embankments is 3 to 5.

[0036] Preferably, in step S4, the terminal multilayered ecological buffer zone consists of an emergent plant area, a submerged plant area, and a gravel damping layer; the porosity of the gravel damping layer is 30% to 45%.

[0037] Preferably, step S1 further includes: setting a sedimentation hopper at the effluent end of the pretreatment tank, and using gravity to allow the sand and gravel in the runoff to settle to the bottom of the sedimentation hopper.

[0038] Preferably, the biochemical purification unit is equipped with a flow guide baffle, the angle between the flow guide baffle and the horizontal plane is 30 degrees to 60 degrees, and the flow guide baffle forms an S-shaped flow path of watershed runoff in the biochemical purification unit.

[0039] Preferably, the top of the anaerobic biological filter is provided with a light-shielding cover, and the light-shielding cover covers the entire liquid surface of the anaerobic biological filter.

[0040] Preferably, it also includes: setting a water level regulating well at the outlet of the terminal multi-layered ecological buffer zone, and changing the operating water level height in the biochemical purification unit by the number of weir plates in the water level regulating well.

[0041] Example 1: In the hilly areas of southern China, small watersheds subject to seasonal rainfall face continuous nonlinear hydrological load fluctuations. Short-duration rainfall shortens the runoff confluence time and increases the kinetic energy at the head of the flow. The drastically fluctuating water level head directly acts on the fixed-volume biological purification unit, causing a hydraulic short-circuit phenomenon. The accompanying high-velocity shear force directly strips the microbial film attached to the surface of the biological substrate in the anaerobic biological filter. During the dry season, the lack of water renewal leads to the depletion of dissolved oxygen in the pretreatment tank and subsequent structures, resulting in water quality deterioration. The watershed runoff is introduced into the pretreatment tank, where a stepped energy dissipation sill is installed to reduce the inflow velocity. The stepped energy dissipation sill traps floating debris and sediment, stabilizing the flow field morphology entering the pretreatment tank. The increased inflow volume causes the water level in the pretreatment tank to rise, creating a physical water level head. An overflow is installed at the connection between the pretreatment tank and the biological purification unit. The weir, specifically the overflow weir, has its crest elevation set according to the rated inflow of the biochemical purification unit. The flow threshold is determined by the difference between the weir crest elevation and the bottom elevation of the pretreatment tank. Based on the water level head in the pretreatment tank, an overflow weir is installed at the connection between the pretreatment tank and the biochemical purification unit. The overflow weir is located directly above the subsurface flow channel. The overflow weir's crest elevation is set according to the rated inflow of the biochemical purification unit, and the flow threshold is determined by the difference between the weir crest elevation and the bottom elevation of the pretreatment tank. Based on the water level head in the pretreatment tank, the overflow weir guides the runoff below the flow threshold through the bottom layer of the subsurface flow channel to the biochemical purification unit. The runoff entering the biochemical purification unit is then sequentially introduced into the anaerobic biological filter and the aerobic ecological pond. The elevation difference between the anaerobic biological filter and the aerobic ecological pond generates gravity flow, which allows the runoff to contact the biological substrate in the anaerobic biological filter and the aquatic plants in the aerobic ecological pond, overcoming internal flow resistance.

[0042] When the water level head in the pretreatment tank causes the flow rate to exceed the flow threshold, the overflow weir diverts the excess runoff to the riparian ecological buffer zone. This physical diversion utilizes water level signals to achieve adaptive flow distribution, transforming abrupt runoff impact loads into physical boundary constraints. This method resolves the engineering constraints between expanding redundant tank capacity and maintaining a suitable flow field for biochemical reactions. The physical diversion effect of the overflow weir synergizes with the elevation difference of the structures, maintaining the hydraulic retention time in the aerobic ecological tank at over 4 hours. This 4-hour time boundary, along with the selection of 3- to 5-level energy dissipation embankments and 30% to 45% damping layer porosity, are all calculated based on a 36-month rainfall-runoff water quality calibration degradation rate database of the target watershed. To rigidly guarantee these parameters under dynamic loads, the control unit executes the highest priority blocking logic: through real-time... The system reads the liquid level and flow rate data correspondence table to obtain the estimated inflow volume, and calculates the ratio with the remaining vacant volume of the aerobic ecological pond. When the estimated actual retention time drops to near the safety threshold of 4 hours, regardless of the current pressure head calculation status of the system, the control unit immediately forces an additional downward pressure pulse command to the overflow weir stepper motor, causing the weir crest elevation to physically decrease by 0.1m. By expanding the geometric channel ratio of the bypass diversion, the absolute volume of sewage entering the core reaction zone is forcibly reduced. This dynamic blocking method rigidly ensures that the biological substrate in the biochemical purification unit is protected from high-velocity shear force erosion, maintaining the structural integrity of the attached microbial film. The drainage from the aerobic ecological pond is directed to the terminal multi-layered ecological buffer zone. The graded packing layer in the terminal multi-layered ecological buffer zone increases the drainage resistance, and the chemical oxygen demand and ammonia nitrogen water quality purification indicators of the system effluent remain stable under kinetic energy impact environment.

[0043] Example 2: To investigate the impact of hydraulic distribution mechanisms on the retention rate of the microbial biofilm within the biochemical purification unit and the overall pollutant removal rate of the system under high-frequency transient rainfall impact conditions, a pilot-scale physical experimental platform was constructed. This platform included a 15m³ pretreatment tank, a 20m³ effective volume biochemical purification unit, and a shoreline ecological buffer zone simulating natural elevation differences. The test water source was drawn from surrounding natural river water and mixed with artificially prepared high-concentration rainwater runoff. The baseline concentration of influent chemical oxygen demand (COD) was maintained at 250 mg / L, and the baseline concentration of ammonia nitrogen was also maintained at [missing information]. With a concentration of 15 mg / L, the influent pump group was controlled to generate transient flow pulses with step characteristics, and random Gaussian white noise with an amplitude fluctuating by 5% was superimposed on the basic influent flow curve. This hydrological disturbance noise was achieved at the physical testing equipment level by connecting a servo proportional valve with a frequency response range of 0 Hz to 50 Hz outside the main influent pipeline, and by a programmable logic controller outputting a random duty cycle control signal with a 100 ms update cycle to frequently block and restore the water flow area, thereby simulating irregular hydrological disturbances in the natural watershed confluence process. The core technical consideration for determining the overflow weir crest elevation in the pretreatment tank lies in balancing the total amount of runoff interception and purification with the hydraulic shear stress limit borne by the biofilm inside the biochemical purification unit. When the porosity inside the biochemical purification unit decreases and the water flow channel contracts, the sensitivity of the internal flow velocity to the external influent water level pressure head increases nonlinearly. The judgment rule for the overflow weir elevation parameter is based on the correspondence between hydraulic resistance and biofilm adhesion. According to the microbial film on the surface of the polyurethane biomatrix undergoing 720 days in a closed transparent test tank... After biofilm formation, the speed of the variable frequency circulating water pump was gradually increased, and the surface was observed simultaneously using a 500FPS high-speed camera. The flow rate reading of the rotor flowmeter corresponding to the instant when the continuous detachment area of ​​the biofilm reached 20% of the total attachment area was calibrated as the measured critical detachment flow rate limit of 0.15m / s. The upper limit of the allowable safe overflow head in the biochemical purification unit was calculated in reverse. Combined with the hydraulic friction resistance equation, the liquid level head limit of the overflow weir was calculated to be 0.45m. The runoff in the watershed exceeding this head height was diverted to the overflow bypass.

[0044] An experimental group and two independent control groups were set up. The experimental group used an overflow weir with a set upper limit of 0.45m and was equipped with a stepped energy dissipation sill and a gravity flow distribution structure based on elevation difference. Control group 1 removed the overflow weir structure to allow all transient pulse water flow to completely penetrate the biochemical purification unit. Control group 2 had the overflow weir liquid level head height limit set at 0.85m to form an out-of-range operating condition exceeding the critical shear stress design limit. A test hydrological sequence was established and a baseline flow rate of 10m³ / h, a moderate impact flow rate of 30m³ / h, and a flow rate of 6m³ / h were set. The system was continuously operated for 48 hours at an extreme pulse flow rate of 0 m³ / h under various constant reference flow rates superimposed with random noise. Real-time flow velocity within the biochemical purification unit and biofilm retention rate at the end of the experimental cycle were monitored simultaneously. Intermediate quantitative data on the core flow field characteristics and attached microorganisms within the biochemical purification unit were obtained. Under a reference flow rate of 10 m³ / h, the accumulated water head in the pretreatment tank was below 0.3 m and no physical overflow mechanism was triggered. The measured flow velocities within the experimental group and the two control groups were maintained at [a certain value]. Within the safe range of 0.04 m / s to 0.05 m / s, the biofilm retention rates were measured to be 98.2%, 98.1%, and 98.4%, respectively. When the baseline flow rate was instantaneously increased to 60 m³ / h and a flow velocity disturbance component was introduced, the liquid level in the pretreatment tank of the experimental group rose to the 0.45 m limit and triggered an overflow diversion action. The measured flow velocity inside the anaerobic biological filter of the experimental group was controlled within a narrow fluctuation range of 0.11 m / s to 0.13 m / s. The physical water level boundary suppressed random flow noise from entering the biochemical purification process. The transfer within the chemical unit was measured, and the biofilm retention rate was 91.4%. In control group one, the internal flow velocity increased sharply to 0.42 m / s. The high flow velocity and shear force directly washed away the polyurethane carrier, causing the biofilm retention rate to drop sharply to 27.5%. In control group two, the internal flow velocity reached 0.26 m / s and exceeded the critical safety threshold of 0.15 m / s, inducing a moderate stripping effect, which reduced the measured biofilm retention rate to 52.1%. Key data on the water quality concentration at the system effluent were extracted and quantified to confirm the final technical effect.

[0045] Under an extreme pulse flow impact of 60 m³ / h, the overall chemical oxygen demand (COD) removal rate in the experimental group remained at 76.8%, and the ammonia nitrogen removal rate remained at 68.5%. Excessive transient floodwaters, within the shoreline ecological buffer zone, achieved a 31.2% reduction in COD through the physical impediment and adsorption sedimentation of the graded filler layer. In control group one, the overall COD removal rate dropped to 19.4% due to the significant loss of the core purification community. In control group two, the COD removal rate was 41.7%. The evolution curve of pollutant removal efficiency across the entire flow range shows that when the influent baseline flow... When the flow rate increased from 60 m³ / h to 80 m³ / h, the chemical oxygen demand (COD) removal rate of the effluent in the experimental group remained in a stable plateau range of 75.0% to 76.8%. When the influent reference flow rate exceeded the inflection point of 85 m³ / h and exceeded the maximum physical permeability flux of the graded filler material in the shore ecological buffer zone, the overall COD removal rate of the system deteriorated nonlinearly and dropped sharply to 48.3%. The test data confirmed that the physical diversion system jointly constructed by the overflow weir head difference and elevation potential energy severed the direct destructive connection between the external extreme hydrological pulse and the internal flow field of the biochemical structure.

[0046] Example 3: The current accumulation of non-point source suspended solids and the proliferation of internally attached microbial films create physical constraints on the multi-stage linkage water purification system. The matrix porosity in the anaerobic biological filter decreases with operating time. The initially calibrated static overflow weir crest elevation cannot adapt to the increased hydraulic resistance, leading to premature triggering of overflow diversion under the input of the basin runoff benchmark flow rate, or, under transient rainfall impact conditions, the shear force of the water flow inside the biochemical purification unit exceeds the adhesion limit of the microbial film due to the flow resistance lag effect. The end of the pretreatment tank and the effluent end of the anaerobic biological filter are selected as liquid level monitoring nodes. The liquid level transmitters at both ends synchronously collect real-time liquid level parameters. The control unit calculates the liquid level difference between the two to obtain the real-time head loss of the biochemical purification unit, and introduces a flow resistance change coefficient to characterize the decay state of the internal physical porosity, according to the formula... The flow resistance variation coefficient is calculated, where K is the flow resistance variation coefficient, ΔH is the real-time head loss collected, and Q is the real-time flow rate of the guiding biochemical purification unit. The maximum safe inlet pressure head that the biochemical purification unit can withstand under the current porosity is calculated. Based on the physical model of friction head loss, the control unit adopts the formula... Determine the inlet water pressure head, where, This represents the maximum safe inlet pressure head, and K represents the real-time flow resistance variation coefficient obtained from previous calculations. The critical stripping flow rate threshold corresponding to the locally stored microbial membrane, where A is the internal cross-sectional area of ​​the biochemical purification unit.

[0047] The internal structure of the pretreatment tank defines a hydraulic lag volume zone, with a physical water storage volume not less than the product of the preset transient confluence acceleration extreme value and the full stroke operating time of the weir lifting mechanism. Based on the obtained flow resistance change coefficient and the preset critical stripping velocity threshold, the control unit calculates the maximum safe influent head under the current porosity in the biochemical purification unit and sends an adjustment command to the mechanically lifting overflow weir at the connection between the pretreatment tank and the biochemical purification unit, driving the weir lifting mechanism to adjust the actual weir crest elevation. The calibration and compensation of real-time head loss ensures that the overflow weir's diversion boundary matches the flow capacity of the biochemical purification unit. The dynamic flow resistance compensation mechanism cuts off flood kinetic energy higher than the maximum safe influent head during the operating cycle when the matrix porosity decreases by 30%, avoiding biofilm stripping caused by static weir height setting and maintaining the stability of the system's effluent water quality.

[0048] Example 4: When the multi-stage linkage water purification system is in its initial deployment state, the physical overflow boundary and the internal hydraulic parameters of the biochemical purification unit are calibrated. A constant reference flow rate of raw river water is continuously injected into the fluid channels of the pretreatment tank and the biochemical purification unit. After the internal liquid level of the structure reaches a dynamic equilibrium, level transmitters deployed at the end of the pretreatment tank and the effluent end of the anaerobic biological filter are used. The control unit is configured to continuously read the original liquid level analog voltage signal at a sampling frequency of 100Hz, establishing a data buffer queue with 50 sampling points. Each time the queue is updated, the highest and lowest three abnormal extreme values ​​are removed, and the arithmetic average of the remaining 44 valid sampling points is calculated to output the smoothed physical height of the liquid level, eliminating high-frequency noise caused by transient water wave surges; For real-time flow rate acquisition, the control unit does not rely on an external physical flow meter. Instead, it reads the pre-stored liquid level height from the internal non-volatile memory and maps it to a flow rate discrete data mapping table. This data mapping table is generated during the initial system deployment by injecting clean water in 5 m³ / h increments using an external standard flow variable frequency pump, simultaneously recording the smoothed physical liquid level height. The control unit looks up the table based on the current smoothed physical liquid level height and outputs the corresponding real-time flow rate value using linear scaling. Based on this, it simultaneously collects the liquid level difference under steady-state conditions to obtain the initial head loss. Based on this constant reference flow rate and the initial head loss, it calculates the initial flow resistance characteristic reference value corresponding to the initial deployment conditions. The specific formula for calculating the initial flow resistance characteristic reference value is as follows: ,in, This is the initial flow resistance characteristic reference value. This represents the measured initial head loss. To inject a constant reference flow rate, the control unit writes the initial flow resistance characteristic reference value into the local register as a reference for subsequent monitoring of flow resistance evolution.

[0049] The control unit reads the critical stripping velocity threshold corresponding to the microbial film on the target biomatrix surface, stored locally. Combined with the physical cross-sectional area inside the biochemical purification unit, to eliminate the physical logic discontinuity of the static cross-sectional area under dynamic porosity decay conditions, this physical cross-sectional area is replaced at the software level with the real-time effective flow cross-sectional area obtained by the control unit by consulting a built-in table mapping flow resistance characteristics to effective cross-sectional area data. This discrete mapping table is obtained based on measured fitting of an offline physical sand table under a sediment content gradient of 0% to 50%. Based on the dynamically matched real-time effective flow cross-sectional area, the maximum safe influent flow rate not exceeding the critical stripping velocity threshold is calculated. Based on the initial flow resistance characteristic baseline value and the maximum safe influent flow rate, the initial physical diversion boundary of the overflow weir at the connection between the pretreatment tank and the biochemical purification unit is determined. The formula for calculating the initial head limit corresponding to the initial physical diversion boundary is as follows: ,in, This is the initial upper limit of the water head. To obtain the maximum safe inflow rate, the control unit outputs a control command to the mechanically lifting overflow weir. The specific physical mapping logic of this control command is as follows: The control unit subtracts the smoothed liquid level physical height output by the current liquid level transmitter from the calculated absolute height physical quantity corresponding to the initial head upper limit to obtain the height difference control quantity. This value is then divided by the 0.05mm physical step angle increment corresponding to each pulse of the stepper motor drive screw, rounded down to generate the corresponding number of stepper pulse drives. A specified number of high and low level pulse signals are output to the stepper motor controller through the pulse width modulation port to drive the weir plate lifting mechanism to move the weir top elevation to the physical position corresponding to the initial head upper limit. The system sets physical parameters according to the target hydrological environment and activates hydraulic distribution.

[0050] The above description is only a few preferred embodiments of the present invention and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the embodiments of the present invention is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the above-mentioned inventive concept. For example, technical solutions formed by replacing the above-mentioned features with (but not limited to) technical features with similar functions disclosed in the embodiments of the present invention.

Claims

1. A multi-stage coordinated water purification and treatment method for watershed management, characterized in that, Includes the following steps: Step S1: The watershed runoff is introduced into the pretreatment pool. The stepped energy dissipation sills set in the pretreatment pool are used to reduce the inflow velocity of the watershed runoff and to intercept floating objects and sediment in the watershed runoff. Step S2: An overflow weir is set at the connection between the pretreatment tank and the biochemical purification unit. Based on the water level head in the pretreatment tank, the overflow weir directs watershed runoff with a flow rate below the flow rate threshold to the biochemical purification unit, and directs watershed runoff with a flow rate exceeding the flow rate threshold to the riparian ecological buffer zone. The weir crest elevation is set according to the rated inflow of the biochemical purification unit, and the flow rate threshold is determined by the difference between the weir crest elevation and the bottom elevation of the pretreatment tank. Step S3: The watershed runoff entering the biochemical purification unit is sequentially introduced into the anaerobic biological filter and the aerobic ecological pond. The elevation difference between the anaerobic biological filter and the aerobic ecological pond is used to generate gravity flow of fluid, and the watershed runoff is brought into contact with the biological substrate in the anaerobic biological filter and the aquatic plants in the aerobic ecological pond, respectively. Step S4: Drainage from the aerobic ecological pond is directed to the end multi-layered ecological buffer zone, and the drainage resistance is increased by the graded filler layer in the end multi-layered ecological buffer zone.

2. The multi-stage coordinated water purification and treatment method for watershed management according to claim 1, characterized in that, In step S2, the overflow weir is set at the inlet of the biochemical purification unit, and the flow rate entering the biochemical purification unit is determined by the relative difference between the weir crest elevation and the water level in the pretreatment tank.

3. The multi-stage coordinated water purification and treatment method for watershed management according to claim 1, characterized in that, In step S3, the specific surface area of ​​the biological substrate filling the anaerobic biological filter is not less than 200 m². 2 / m 3 Emergent plants are planted in the aerobic ecological pond, and the roots of the aquatic plants are covered with microbial films.

4. The multi-stage coordinated water purification and treatment method for watershed management according to claim 3, characterized in that, The hydraulic retention time in the aerobic ecological pond is determined by the following formula: T=V / Q, where T is the hydraulic retention time, V is the volume of the aerobic ecological pond, and Q is the real-time flow rate entering the aerobic ecological pond; the hydraulic retention time is controlled to be more than 4 hours through the physical diversion effect of the overflow weir.

5. A multi-stage coordinated water purification and treatment method for watershed management according to claim 1, characterized in that, In step S1, the height of the stepped energy dissipation embankment is determined according to the river channel slope of the watershed, and the number of stepped energy dissipation embankments is 3 to 5.

6. A multi-stage coordinated water purification and treatment method for watershed management according to claim 1, characterized in that, In step S4, the terminal multi-layered ecological buffer zone consists of emergent plant area, submerged plant area and gravel damping layer; the porosity of the gravel damping layer is 30% to 45%.

7. A multi-stage coordinated water purification and treatment method for watershed management according to claim 1, characterized in that, Step S1 also includes: setting a sedimentation hopper at the effluent end of the pretreatment tank, and using gravity to allow the sand and gravel in the watershed runoff to settle to the bottom of the sedimentation hopper.

8. A multi-stage coordinated water purification and treatment method for watershed management according to claim 1, characterized in that, The biochemical purification unit is equipped with a flow guide baffle, which has an angle of 30 to 60 degrees with the horizontal plane, and the flow guide baffle forms an S-shaped flow path for watershed runoff within the biochemical purification unit.

9. A multi-stage coordinated water purification and treatment method for watershed management according to claim 1, characterized in that, The top of the anaerobic biological filter is equipped with a light-shielding cover, which covers the entire liquid surface of the anaerobic biological filter.

10. A multi-stage coordinated water purification and treatment method for watershed management according to claim 1, characterized in that, Also includes: A water level regulating well is installed at the outlet of the terminal multi-layered ecological buffer zone. The number of weirs in the water level regulating well changes the operating water level in the biochemical purification unit.

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