Method for removing attached algae by sediment-laden water

Abstract

The present invention discloses a method for removing attached algae from sediment-laden water flow, which includes collecting the biomass density of attached algae in the river downstream of the reservoir; when the biomass density is greater than a preset density, obtaining the water flow velocity and sediment content in the water body of the river under various pulse flows; calculating the scouring removal rate of each type of algae in the attached algae under all pulse flows; selecting the corresponding pulse flow required when the same type of algae is greater than its preset target removal rate, and counting all the pulse flows required to scour and remove the algae to reach the target removal rate; according to the water storage volume in the reservoir, selecting the optimal value from the counted pulse flows, and starting the reservoir to discharge the pulse flow to remove the attached algae.

Description

Technical Field

[0001] The present invention relates to the technical field of river ecological protection, and particularly relates to a method for removing attached algae by sediment-laden flow. Background Art

[0002] Attached algae are the general term for algae such as diatoms, cyanobacteria, and green algae attached to riverbed pebbles, rocks, sediment, and aquatic plants. Attached algae are important primary producers and the main source of energy in mountain river ecosystems. Their biomass and species composition have important ecological value and are the food source for benthic animals and fish.

[0003] Benthic animals and fish prefer to eat diatoms and rarely eat and digest cyanobacteria. Filamentous cyanobacteria may also block rapids and shoals, causing water quality deterioration. Water flow velocity is an important factor affecting attached algae. In dammed rivers, the flow rate and velocity are artificially controlled, and the change frequency generally decreases. Compared with before damming, the attached algae in the downstream river of the reservoir are less scoured by the natural flood pulse velocity and lack the natural renewal and succession process.

[0004] Under relatively stable low flow velocity conditions, the biomass of algae will grow excessively. When the biomass density is greater than a certain value, it is in an overgrowth state. As the algae density increases, the proportion of cyanobacteria will gradually increase, and it can develop from being mainly diatoms (reference Figure 1 ) to an overgrowth stage of algae mainly composed of filamentous cyanobacteria, thereby causing water quality deterioration and a decline in the habitat quality of fish fattening grounds. Summary of the Invention

[0005] In view of the above deficiencies in the prior art, the method for removing attached algae by sediment-laden flow provided by the present invention can scour the attached algae in the river to reduce their biomass density by adjusting the pulsed discharge from the reservoir.

[0006] To achieve the above invention object, the technical solution adopted by the present invention is as follows:

[0007] Provide a method for removing attached algae by sediment-laden flow, which includes the steps of:

[0008] S1. Collect the biomass density of attached algae in the river downstream of the reservoir;

[0009] S2. When the biomass density is greater than the preset density, obtain the water flow velocity and sediment content in the water of the river under various pulsed discharges;

[0010] S3. Based on the momentum theorem for scouring attached algae, calculate the scouring removal rate of each type of algae in the attached algae under all pulsed discharges R m :

[0011]

[0012] Among them, S m is the algae scouring resistance coefficient; ρ w is the density of water, ρ s is the sediment concentration in the water body; v is the water flow velocity;

[0013] S4. Select the corresponding pulse flow required when the removal rate of the same algae is greater than its preset target removal rate, and count the pulse flow required for removing all the algae to be scoured and removed;

[0014] S5. According to the water storage volume in the reservoir, select the optimal value from the counted pulse flows, and start the reservoir to release the pulse flow to remove the attached algae.

[0015] Furthermore, the calculation formula of the algae scouring resistance coefficient is:

[0016]

[0017] Among them, C d is the turbulence resistance coefficient, L is the shape coefficient of the algae being scoured.

[0018] Furthermore, the method for removing attached algae by sediment-laden water flow also includes calculating the impact force of the water flow on each type of algae when calculating the released pulse flow F which is:

[0019]

[0020] Among them, C d is the turbulence resistance coefficient, L is the shape coefficient of the algae being scoured.

[0021] Furthermore, the step S1 includes:

[0022] At the wading section downstream of the reservoir and when the water flow is stable, randomly collect at least 3 pebbles along the riverbed cross-section;

[0023] Scrape the attached algae with a preset area on each stone, and form a mixed solution after rinsing the surface of the pebbles with distilled water;

[0024] Measure the chlorophyll a biomass of the attached algae, identify the algae species, and obtain the biomass density of the algae according to the sampling area and biomass.

[0025] Furthermore, the method for obtaining the water flow velocity and sediment concentration in the river under multiple pulse flows includes:

[0026] S21. Construct a test flume to simulate the pulse discharge of a river with a reservoir, where the sediment content in the test flume is the same as that in the river with the reservoir.

[0027] S22. Adjust the initial water flow in the test flume to be equal to the flow velocity of the river with the reservoir, discharge a pulse flow into the test flume, and collect the flow velocity and sediment concentration in the water body of the test flume.

[0028] S23. Increase the pulse flow according to a preset value and return to step S22 until the collected flow velocity and sediment concentration in the water body reach the preset values.

[0029] S24. According to the pulse flow and the corresponding preset flow velocity and sediment concentration, use the bilinear interpolation method to expand the quantities of the flow velocity and sediment concentration in the water body respectively.

[0030] S25. Use all the flow velocities and sediment concentrations in the water body obtained in step S24 to plot a flow velocity - pulse flow curve and a sediment concentration in the water body - pulse flow curve, and smooth the two curves.

[0031] S26. Based on the smoothed curves, obtain the flow velocity and sediment concentration in the water body at each pulse flow between the initial pulse flow and the maximum pulse flow.

[0032] Further, the method for selecting the optimal value among the statistically counted pulse flows includes:

[0033] When the water storage in the reservoir indicates that it is in the dry season, select the minimum value among the statistically counted pulse flows as the optimal value.

[0034] When the water storage in the reservoir indicates that it is in the flood season, select the maximum value among the statistically counted pulse flows as the optimal value.

[0035] When the water storage in the reservoir indicates that it is neither in the dry season nor in the flood season, calculate the ratio of the scouring removal rate of each type of algae to be removed to its corresponding preset target removal rate at each pulse flow.

[0036] Compare the ratios at all pulse flows, and select the pulse flow with the largest number of the largest ratios as the optimal value.

[0037] Further, the preset density of the epiphytic algae to be scoured and removed is greater than 150 mg / m 2 .

[0038] The beneficial effects of the present invention are as follows: Based on the specific scouring removal rate target (preset removal rate) of harmful algae and combined with the scouring removal rate model of algae constructed in this solution, the scouring removal rate under each pulse can be quickly obtained. Based on this, the ecological flow rate of the reservoir discharge required can be quickly determined, so as to scour the attached algae, promote the renewal and succession of periphytic algae, and promote the ecological-friendly operation of the reservoir and the protection and restoration of the aquatic ecosystem in the downstream river course.

[0039] The scouring removal rate model of algae constructed in this solution is based on the quantitative relationship between variables such as the algae scouring resistance coefficient, water sediment concentration, and water flow velocity, which can improve the quantitative calculation ability of the scouring algae removal rate; this model considers the water flow scouring effect under different flow velocities and sediment concentrations, and can be applied to the evaluation of the scouring removal effect of sediment-laden water in natural river courses on periphytic algae. Description of the Drawings

[0040] Figure 1 It is the growth status of filamentous periphytic algae.

[0041] Figure 2 It is the flow chart of the method for removing periphytic algae by sediment-laden water. Detailed Embodiments

[0042] The following describes the detailed embodiments of the present invention to facilitate those skilled in the art of the present technology to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the detailed embodiments. For those of ordinary skill in the art of the present technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are within the scope of protection.

[0043] Refer to Figure 2 , Figure 2 which shows the flow chart of the method for removing periphytic algae by sediment-laden water; as Figure 1 shown, this method S includes steps S1 to S5.

[0044] In step S1, collect the biomass density of periphytic algae in the river downstream of the reservoir. The specific collection method may include the following steps:

[0045] In the wadeable section downstream of the reservoir and when the water flow is stable, randomly collect at least 3 pebbles along the riverbed cross-section;

[0046] Scrape a preset area of periphytic algae on each stone, and form a mixed solution after rinsing the surface of the pebble with distilled water;

[0047] Measure the chlorophyll a biomass of periphytic algae, identify the algae species, and obtain the biomass density of algae according to the sampling area and biomass.

[0048] In step S2, when the biomass density is greater than a preset density, the water flow velocity and the sediment content of the river under various pulse flow rates are obtained.

[0049] Through a large amount of experimental data, it is found that when the biomass density of algae is greater than 150mg / m 2 When the algae is in an overgrowth state, the proportion of filamentous algae is on the rise, which is higher than the proportion in the normal succession process of the algae community structure. Therefore, this plan sets the preset density to 150mg / m 2 .

[0050] In one embodiment of the present invention, a method for obtaining the water flow velocity and the water sediment content of a river under various pulse flow rates includes:

[0051] S21. construct a test flume simulating the outflow pulse flow of a river with a reservoir, wherein the sediment content in the test flume is the same as that of the river with a reservoir;

[0052] S22, adjusting the water flow in the initial state of the test flume to be equal to the flow velocity of the river with the reservoir, discharging a pulse flow into the test flume, and collecting the flow velocity and sediment content in the test flume;

[0053] S23, increasing the pulse flow rate according to a preset value, and returning to step S22 until the collected flow velocity and water body sediment content reach a preset value;

[0054] S24, according to the pulse flow rate and the corresponding preset flow velocity and sediment content, using a bilinear interpolation method to expand the flow velocity and the sediment content of the water body respectively;

[0055] S25, using all the flow velocities and water sediment content obtained in step S24, draw a flow velocity-pulse flow curve and a water sediment content-pulse flow curve, and smooth the two curves;

[0056] S26. Based on the smoothed curve, the flow velocity and the water body sediment content at each pulse flow rate between the initial pulse flow rate and the maximum pulse flow rate are obtained.

[0057] This scheme first obtains multiple sets of pulse flow, flow velocity and sediment content data through experiments, and then uses interpolation to expand the data. This can ensure the accuracy of the acquired data while greatly reducing the test time for obtaining the flow velocity and sediment content corresponding to different pulse flow rates. Since the number of test groups required is greatly reduced, the test cost can be saved.

[0058] In addition, this scheme smoothes the two obtained curves to eliminate values with large errors, which can further make the flow velocity and water sediment content under each pulse flow more accurate, thereby ensuring the accuracy of the scour removal rate obtained by subsequent calculations.

[0059] In step S3, based on the momentum theorem of the epilithic algae being scoured, calculate the scouring removal rate of each type of algae in the epilithic algae under all pulse flows. R m :

[0060]

[0061] Among them, S m is the algae scouring resistance coefficient; ρ w is the density of water, ρ s is the sediment concentration in the water body; v is the water flow velocity;

[0062] During implementation, the preferred calculation formula for the algae scouring resistance coefficient in this solution is:

[0063]

[0064] Among them, C d is the turbulence resistance coefficient, L is the shape coefficient of the algae being scoured.

[0065] In step S4, select the pulse flow corresponding to when the removal rate of the same type of algae is greater than its preset target removal rate, and count the pulse flows required for all the algae to be scoured and removed.

[0066] In step S5, according to the water storage volume in the reservoir, select the optimal value among the counted pulse flows, and start the reservoir to discharge the pulse flow to remove the epilithic algae.

[0067] During implementation, the preferred method for selecting the optimal value among the counted pulse flows in this solution includes:

[0068] When the water storage volume in the reservoir indicates that it is in the dry season, select the minimum value among the counted pulse flows as the optimal value;

[0069] When the water storage volume in the reservoir indicates that it is in the flood season, select the maximum value among the counted pulse flows as the optimal value;

[0070] When the water storage volume in the reservoir does not indicate that it is in the dry season or the flood season, calculate the ratio of the scouring removal rate of each type of algae to be removed to its corresponding preset target removal rate under each pulse flow;

[0071] Compare the ratios under all pulse flows, and select the pulse flow with the largest number of the largest ratios as the optimal value.

[0072] During implementation, this solution preferably also includes calculating the impact force of the water flow on each type of algae when discharging the pulse flow. Fis: the impact force of water flow on each type of algae F is:

[0073]

[0074] wherein, C d is the turbulence resistance coefficient, L is the shape coefficient of the algae being scoured.

[0075] The impact force calculated in this solution can reflect the acting force on the algae when discharging pulsed flow, and the algae removal effect can be further reflected by this force. After the calculation in step S3 is completed, it is judged whether the algae removal rate and the impact force F reflect the same algae removal effect under the same pulsed flow. If they are inconsistent, in this case, the pulsed flow corresponding to the algae can be excluded to ensure that the finally selected pulsed flow can achieve the expected algae removal effect.

[0076] In summary, the algae removal effect evaluated by this solution through the scouring removal rate obtained from the flow velocity and sediment concentration under different pulsed flows is used to select the best pulsed flow for algae removal, so as to achieve the protection and restoration effect of the water body in the downstream river channel of the reservoir.

Claims

1. Method for removing attached algae from sediment-laden water flow, characterized in that, Including the steps: S1. Collect the biomass density of periphytic algae in the river downstream of the reservoir; S2. When the biomass density is greater than the preset density, obtain the water flow velocity and sediment concentration in the river under various pulse flows; S3. Calculate the scouring removal rate of each type of periphytic algae under all pulse flows based on the momentum theorem of periphytic algae R m : Among them, S m is the algae scour resistance coefficient; ρ w is the density of water, ρ s is the sediment concentration in the water body; v is the water flow velocity; The calculation formula for the algae scour resistance coefficient is: Among them, C d is the spoiler drag coefficient, L is the scoured algae shape coefficient; S4. Select the pulse flow corresponding to the preset target removal rate for the same algae, and count the pulse flows required for all algae to be scoured and removed; S5. According to the water storage volume in the reservoir, select the optimal value among the counted pulse flows, and start the reservoir to release the pulse flow to remove the periphytic algae; The method for selecting the optimal value among the counted pulse flows includes: When the water storage volume in the reservoir indicates that it is in the dry season, select the minimum value among the counted pulse flows as the optimal value; When the water storage volume in the reservoir indicates that it is in the flood season, select the maximum value among the counted pulse flows as the optimal value; When the water storage volume in the reservoir does not indicate that it is in the dry season or the flood season, calculate the ratio of the scour removal rate of each algae to be removed to its corresponding preset target removal rate under each pulse flow; Compare the ratios under all pulse flows, and select the pulse flow with the largest number of the largest ratios as the optimal value.

2. The method for removing attached algae by sediment-laden water flow according to claim 1, characterized in that, The step S1 includes: In the wadeable section downstream of the reservoir and when the water flow is stable, randomly collect at least 3 pebbles along the riverbed cross-section; Scrape the periphytic algae with a preset area on each stone, and rinse the surface of the pebbles with distilled water to form a mixed solution; Measure the chlorophyll a biomass of the periphytic algae and identify the algae species, and obtain the biomass density of the algae according to the sampling area and biomass.

3. The method for removing epiphytic algae by sediment-laden water flow according to claim 1, characterized in that, The method for obtaining the water flow velocity and sediment concentration in the river under various pulse flows includes: S21. Construct a test flume to simulate the pulse flow discharged from the reservoir in the river. The sediment content in the test flume is the same as that in the river with a reservoir; S22. Adjust the initial water flow in the test flume to be equal to the flow velocity of the river with a reservoir, discharge the pulse flow into the test flume, and collect the flow velocity and sediment concentration in the test flume; S23. Increase the pulse flow according to the preset value, and return to step S22 until the collected flow velocity and sediment concentration reach the preset value; S24. According to the pulse flow and the corresponding preset value of the flow velocity and sediment concentration, use the bilinear interpolation method to expand the quantities of the flow velocity and sediment concentration respectively; S25. Use all the flow velocities and sediment concentrations obtained in step S24 to draw the flow velocity - pulse flow curve and the sediment concentration - pulse flow curve, and smooth the two curves; S26. Based on the smoothed curves, obtain the flow velocity and sediment concentration under each pulse flow between the initial pulse flow and the maximum pulse flow.

4. The method for removing attached algae by sediment-laden water flow according to any one of claims 1-3, characterized in that, The preset density of epiphytic algae to be washed away is greater than 150 mg / m 2 .

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