A method for locating blockage and determining the degree of blockage in subsurface artificial wetlands

Abstract

The present invention relates to a method for locating blockage and judging the blockage degree of a subsurface flow artificial wetland. The method comprises the following steps: pre-setting permeability coefficient measuring tubes in the subsurface flow artificial wetland, wherein the permeability coefficient measuring tubes are distributed by a systematic random point distribution method to cover wetland substrates of different regions and depths; after the wetland is first circulated with water, a water level meter is used to measure the permeability coefficients of the permeability coefficient measuring tubes one by one to obtain an initial permeability coefficient K0; when the blockage degree of the wetland needs to be judged, a water level meter is used to measure the permeability coefficient once to obtain a secondary permeability coefficient K0. n ; The initial permeability coefficient K0 and the secondary permeability coefficient K n By using the method for locating and judging the blockage degree of the subsurface flow artificial wetland in the present invention, the permeability coefficients of different areas and depths within the wetland can be accurately measured, thereby judging the blockage degree of the wetland and providing effective technical support for wetland construction and operation and maintenance.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular relates to a method for locating blockage and judging the blockage degree of a subsurface artificial wetland. Background Art

[0002] As a popular ecological treatment process, artificial wetlands have been widely used in ecological treatment processes such as rural sewage treatment, river water purification, and deep treatment of sewage plant tailwater.

[0003] According to the requirements of relevant technical specifications, the lifespan of artificial wetlands is generally required to be 20 to 50 years. In fact, in addition to the quality of the project, the blockage problem has become the main factor affecting the lifespan of artificial wetlands. During the operation of artificial wetlands, if there are phenomena such as surface water congestion, stench, and serious decline in effluent water quality due to non-human control reasons, it can be judged as blockage. Blockage is the result of the combined effects of physics, chemistry, and biology. The process of wetland blockage is essentially the process of reducing effective porosity. The sharp decline in porosity will inevitably lead to a decrease in the flow capacity of the wetland. Sewage will form overflow on the surface of the wetland, thereby reducing the sewage purification function and affecting the treatment effect of the wetland and the stability of long-term operation. There are many reasons for the blockage of artificial wetlands, mainly including unreasonable filler grading, high concentration of suspended solids in the inlet water, high organic load, plant residue blockage, improper operation, etc.

[0004] At present, the first task to solve the blockage problem of subsurface artificial wetlands is to accurately evaluate the blockage degree of subsurface artificial wetlands. There are many methods to evaluate the blockage degree, such as microbial fuel cell method, ground penetrating radar method, etc. The above methods can determine the blockage status of wetlands to a certain extent, but due to their high professionalism and high requirements for operators and instruments, they are rarely used in actual projects. At the same time, due to the long operation life of wetlands, methods such as resistivity method and water temperature sensing method that require electrodes or sensors to be laid in wetlands are difficult to guarantee the quality of later operation and signal transmission problems.

[0005] Therefore, it is necessary to develop a simple and reliable method to locate the blockage area and the degree of blockage in subsurface artificial wetlands, so as to provide favorable technical support for the construction of wetland black box models and provide theoretical guarantee for preventing wetland blockage. Summary of the invention

[0006] In view of the defects existing in the prior art, the purpose of the present invention is to provide a method for locating the blockage of a subsurface artificial wetland and judging the blockage degree. By using the in-situ measurement technology of the permeability coefficient method and pre-burying the measurement tube in the wetland, the operator only needs to measure and calculate the pressure head difference of the wetland bed within a certain period of time, and then calculate the permeability coefficient according to the formula to accurately reflect the blockage degree of the wetland. The permeability coefficient method is simple to operate, low in cost, can specifically reflect the blockage degree of the sampling point, and can be directly used in the construction of wetlands for promotion and use.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is: a method for locating blockage and judging the blockage degree of a subsurface artificial wetland, the method comprising the following steps:

[0008] S1. Set up permeability coefficient measuring tubes in the subsurface artificial wetland, and the layout of the permeability coefficient measuring tubes covers the wetland matrix in different areas and depths;

[0009] S2. After the subsurface artificial wetland is first irrigated, the outlet valve is used to control the wetland liquid level, and the liquid level height of each permeability coefficient measuring tube of different lengths is measured to obtain the initial permeability coefficient K of the corresponding wetland matrix at different depths by calculation. 0 ;

[0010] S3. When the degree of wetland blockage needs to be determined, the liquid level height of each permeability coefficient measuring tube of different lengths is measured again, and the corresponding secondary permeability coefficient K of the wetland matrix at different depths is obtained by calculation. n ;

[0011] S4. The calculated initial permeability coefficient K at different depths 0 And the secondary permeability coefficient K n A comparison is made to determine the degree of blockage of the subsurface artificial wetland.

[0012] Furthermore, when constructing the subsurface flow artificial wetland, the permeability coefficient measuring tube is pre-installed in the subsurface flow artificial wetland bed.

[0013] Furthermore, the particle size distribution and laying method of the matrix in the subsurface artificial wetland bed are uniform, and the wetland matrix is ​​divided into three layers in the vertical direction: an upper isolation layer, a middle functional layer and a bottom supporting layer. The thickness of the upper isolation layer is b, the thickness of the middle functional layer is g, the bottom of the measuring tube is located in the middle functional layer area, and the top of the measuring tube is higher than the matrix layer by a≥20cm.

[0014] Furthermore, the length l of the permeability coefficient measuring tube is taken as: a+b<l<a+b+g, and the length l of each permeability coefficient measuring tube is taken as an arithmetic progression.

[0015] Furthermore, the permeability coefficient measuring tubes are arranged using the systematic random distribution method, specifically including: dividing a wetland into several parts of equal area in a grid manner, arranging a permeability coefficient measuring tube in each grid, and the length l of the permeability coefficient measuring tubes arranged in each vertical row and each longitudinal crack is different.

[0016] Further, the steps of measuring the liquid level height of each permeability coefficient measuring tube of different lengths are as follows:

[0017] S21, dividing the permeability coefficient measuring tube and the water outlet valve into several levels in the vertical direction, and controlling the valves at different heights on the water outlet pipe to keep the liquid level of the subsurface flow artificial wetland at different levels so that it just covers the bottom of the permeability coefficient measuring tube to be measured;

[0018] S22, pour water into the permeability coefficient measuring tube continuously until it reaches a distance M below the top of the tube, stop pouring water, and record the liquid level at this time as h 1 ;

[0019] S23. Allow the water level to drop naturally until the reading remains constant at a certain value. The height of the liquid level at this time is recorded as h. 2 , change the liquid level from h 1 Down to h 2 The elapsed time is denoted as t.

[0020] Further, the initial permeability coefficient K 0 And the secondary permeability coefficient K n The permeability coefficient in is calculated according to the following formula:

[0021] Where K is the permeability coefficient, h 1 is the liquid level height at time 0, h 2 is the liquid level height at time t, d is the pipe aperture, L is the underwater length of the pipe perforation, and t is the liquid level from h 1 Down to h 2 The time that has passed.

[0022] Further, the method for determining the degree of blockage is:

[0023] For the same subsurface artificial wetland, calculate the clogging degree judgment coefficient Where: K n K is the permeability coefficient measured in a certain period of time; 0 is the background value of the matrix permeability coefficient measured when the wetland is first irrigated; when 0<θ<k 1 When k 1 <θ<k 2 When k 2 <θ<k 3When k 3 <θ<k 4 When the wetland is completely blocked, k 1 , k 2 , k 3 and k 4 are preset thresholds, k 1 <k 2 <k 3 <k 4 ≤100%.

[0024] Furthermore, the subsurface flow artificial wetland includes a vertical subsurface flow artificial wetland and a horizontal subsurface flow artificial wetland.

[0025] The effect of the present invention is that the method for locating blockage and judging the degree of blockage of a subsurface artificial wetland disclosed in the present invention can effectively solve the problem of monitoring the degree of blockage during the operation of the wetland, so as to timely adjust the operation mode and take effective measures to prevent and alleviate the blockage of the wetland, extend the service life of the wetland, and reduce the renovation costs caused by the blockage of the wetland. Even if renovation is required, the renovation area can be located to the smallest possible range to reduce unnecessary expenses. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A cross-sectional diagram of the distribution of vertical subsurface flow wetland permeability coefficient measuring tubes in a method for locating blockage and determining the blockage degree of a subsurface flow constructed wetland according to an embodiment of the present invention;

[0027] Figure 2 It is a position relationship diagram of the permeability coefficient measuring tube 6 and the pipe sleeve 10 in a method for locating blockage and judging the blockage degree of a subsurface flow constructed wetland according to an embodiment of the present invention;

[0028] Figure 3 A plan view showing the distribution of vertical subsurface flow wetland permeability coefficient measuring tubes in a method for locating blockage and determining the blockage degree of a subsurface flow constructed wetland according to an embodiment of the present invention;

[0029] Figure 4 A fitting diagram of the relationship between the wetland blockage degree and the measuring tube length in a method for locating blockage and determining the blockage degree of a subsurface flow constructed wetland according to an embodiment of the present invention;

[0030] In the figure: 1-wetland water inlet pipe, 2-wetland water outlet pipe, 3-isolation layer, 4-middle functional layer, 5-bottom supporting layer, 6-permeability coefficient measuring tube, 7-pressure probe, 8-data transmission line, 9-data processing unit, 10-pipe sleeve, 11-outlet valve, 11-1-first-order outlet valve, 11-2-second-order outlet valve, 11-3-third-order outlet valve, 11-4-fourth-order outlet valve. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0032] Embodiment 1

[0033] In this embodiment, a vertical subsurface flow artificial wetland for rural sewage treatment in Beijing is used as an example to illustrate the method disclosed in the present invention, but this is not limited to it. In fact, the method disclosed in the present invention is also applicable to horizontal subsurface flow artificial wetlands.

[0034] like Figure 1 As shown, in this embodiment, the wetland water inlet distribution pipe 1 distributes water from the upper end of the wetland matrix, and the matrix particle size distribution and laying method in the subsurface artificial wetland bed are uniform, dividing the wetland matrix into three layers in the vertical direction: the three layers are an upper isolation layer 3, a middle functional layer 4 and a bottom supporting layer 5.

[0035] The upper isolation layer 3 is composed of 8-16 mm ceramsite, which has the function of heat preservation and odor isolation. The thickness of the upper isolation layer 3 is b, which is 0.2 m in this embodiment. The middle functional layer 4 is formed by mixing 1-5 mm zeolite and river sand. The thickness of the middle functional layer 4 is g, which is 0.8 m in this embodiment. The bottom supporting layer 5 is composed of 16-32 mm limestone, and the thickness of the bottom supporting layer 5 is 0.2 m. The wetland water outlet is controlled by valve 11. The top height of the wetland outlet pipe 2 is 1 m, the height of the first-order valve is 0.8 m, the second-order valve is 0.6 m, the third-order valve is 0.4 m, and the fourth-order valve is 0.1 m.

[0036] A method for locating blockage and determining the blockage degree of a subsurface artificial wetland disclosed in the present invention comprises the following steps:

[0037] S1. A permeability coefficient measuring tube 6 is set in the subsurface artificial wetland. The permeability coefficient measuring tube 6 is arranged to cover wetland matrices of different regions and depths.

[0038] A permeability coefficient measuring pipe 6 is laid in the wetland. The permeability coefficient measuring pipe 6 is a high-density polyethylene HDPE pipe, a galvanized steel pipe or a PVC pipe. Figure 2 As shown, a pipe sleeve 10 is provided on the top of the permeability coefficient measuring tube 6, the bottom of the permeability coefficient measuring tube 6 is located in the middle functional layer 4 area, and the top of the permeability coefficient measuring tube 6 is higher than the wetland matrix by a height a of not less than 20 cm.

[0039] The inner diameter d of the permeability coefficient measuring tube 6 is 80-160 mm, preferably 110 mm, and the wall thickness is 3.2-5.5 mm, preferably 5.3 mm. In order to ensure that the bottom of the permeability coefficient measuring tube 6 is located in the middle functional layer 4 area, the length l of the permeability coefficient measuring tube 6 is: a+b<l<a+b+g. The permeability coefficient measuring tube 6 needs to have a certain hardness and can withstand a pressure of 0.8Mpa; the tube sleeve 10 is made of low-density polyethylene LDPE, 80 mm long, and 121 mm in inner diameter.

[0040] like Figure 3 As shown, in this embodiment, the laying method of the permeability coefficient measuring tube 6 adopts the random point method, that is, a wetland is divided into several parts of equal area in a grid manner, and a measuring tube is laid in each grid. The length of the measuring tube is different in each vertical row and each longitudinal crack. The length l of the permeability coefficient measuring tube 6 takes an arithmetic progression value to ensure the extensiveness of the measured data at different heights and planes of the wetland. The size of the wetland division area is 5% to 20% of the construction area of ​​each vertical subsurface flow wetland, preferably 6.25%. In this embodiment, the length l of the permeability coefficient measuring tube 6 is: 1.1m, 0.9m, 0.7m and 0.5m.

[0041] S2. After the first water flow to the subsurface artificial wetland, the outlet valve is used to control the wetland liquid level, and the water level meter is used to measure the liquid level height of each permeability coefficient measuring tube 6 of different lengths, and the initial permeability coefficient K of the corresponding wetland matrix at different depths is obtained by calculation. 0 .

[0042] The permeability performance of wetland substrates at different depths can be determined by measuring the liquid level of permeability coefficient measuring tubes 6 of different lengths.

[0043] The water level meter uses a immersion liquid level meter, which includes a pressure probe 7, a data transmission line 8 and a data processing unit 9. The data processing unit 9 can record the time and water level value in real time. The water level meter has a measuring range greater than 3m. In this embodiment, the measuring range of the water level meter is 5m, the output frequency is 0.1s, and the measuring accuracy is 0.5%.

[0044] The calculation formula of permeability coefficient K is:

[0045]

[0046] Where K is the permeability coefficient, cm / min; h 1 is the liquid level height at time 0, cm; h 2 is the liquid level height at time t, cm; d is the pipe aperture, cm; L is the underwater length of the pipe perforation, cm; t is the time, min.

[0047] The liquid level is measured as follows:

[0048] S21, the permeability coefficient measuring tube 6 and the water outlet valve are divided into 4 levels in the vertical direction, and the valves at different heights on the wetland outlet pipe 2 are controlled to keep the liquid level at different levels so that it just covers the bottom of the permeability coefficient measuring tube 6 at the height to be measured, that is, the underwater length L of the perforation of the permeability coefficient measuring tube 6 is greater than 0;

[0049] S22. Place the water level meter probe into the bottom of the permeability coefficient measuring tube 6, pour water into the permeability coefficient measuring tube 6 continuously until it reaches 5 cm below the top of the permeability coefficient measuring tube 6, turn on the instrument and start reading. The water level meter can automatically record the time and liquid level changes. Continue to add water to the permeability coefficient measuring tube until there is a little overflow on the top of the tube. Keep pouring water for 2 seconds and then record the liquid level height at this time as h 1 ;

[0050] S23. Allow the water level to drop naturally until the reading remains constant at a certain value. The height of the liquid level at this time is recorded as h. 2 . , the liquid level is changed from h 1 Down to h 2 The elapsed time is denoted as t.

[0051] In this embodiment, each point is measured repeatedly for multiple times, and the average value of the three measurement results with an error less than 2% is selected to calculate the permeability coefficient of the point.

[0052] By closing all the outlet valves, the permeability coefficients of all points can be measured; by opening the first-order valve 11-1, the permeability coefficients of points other than 0.5m can be measured; by opening the second-order valve 11-2, the permeability coefficients of points 1.1m and 0.9m can be measured; by opening the third-order valve 11-3, only points with a pipe length of 1.1 meters can be measured; by opening the fourth-order valve 11-4, the wetland can be emptied; the wetland liquid level can be controlled by adjusting the outlet valves to meet different operating needs.

[0053] S3. After the subsurface artificial wetland has been in operation for a period of time, when the wetland blockage situation needs to be checked, the water level meter is used to measure the liquid level height of each permeability coefficient measuring tube 6 of different lengths again, and the corresponding secondary permeability coefficient K of the wetland matrix at different depths is obtained by calculation. n .

[0054] After the subsurface flow artificial wetland has been in operation for 2 years, when it is necessary to check the blockage of the wetland, the permeability coefficient of the laid pipes is measured again one by one using a water level meter. Each point is measured repeatedly for multiple times, and the average of the three measurement results with an error of less than 2% is selected to calculate the permeability coefficient of the point.

[0055] S4. The calculated initial permeability coefficient K of each point 0 And the secondary permeability coefficient K nBy comparison, the degree of blockage of the subsurface artificial wetland can be judged.

[0056] The method for judging the degree of blockage is as follows: for the same subsurface artificial wetland, the blockage degree judgment coefficient is calculated according to the following formula:

[0057] Where: θ is the blocking degree judgment coefficient; K n K is the permeability coefficient measured in a certain period of time; 0 It is the background value of the matrix permeability coefficient measured when water is first passed through the wetland;

[0058] When 0<θ<k 1 When k 1 <θ<k 2 When k 2 <θ<k 3 When k 3 <θ<k 4 When the wetland is completely blocked, k 1 , k 2 , k 3 and k 4 are preset thresholds, k 1 <k 2 <k 3 <k 4 ≤100%.

[0059] In this embodiment, when 0<θ<25%, it indicates that the wetland is slightly blocked, when 25%<θ<50%, it indicates that the wetland is moderately blocked, when 50%<θ<75%, it indicates that the wetland is severely blocked, and when 75%<θ<100%, it indicates that the wetland is completely blocked. However, this is not limited to an example.

[0060] In this embodiment, the permeability coefficient measurement value K and the blockage degree determination coefficient θ calculated by the above method are shown in Table 1.

[0061] Table 1 Permeability coefficient values ​​and blockage degree judgment coefficients at different points

[0062]

[0063] The first, second, third and fourth rows in Table 1 represent horizontal rows that are parallel to the water inlet pipe but have different measured depths. The first, second, third and fourth rows are arranged from top to bottom. The permeability test tubes arranged in each row are at the same height above the wetland matrix, and the measured wetland matrix depths are different. The permeability test tubes in the other three rows are arranged and combined based on the increasing depth of the wetland matrix measured by the permeability test tubes arranged in the first row, so as to ensure that the permeability test tubes arranged in the same column in the vertical direction have different measured depths. It can be seen from Table 1 that the vertical subsurface flow artificial wetlands that have been in operation for two years have all been blocked, but the degree is relatively mild. At the same time, the data in Table 1 are fitted to obtain Figure 4 The relationship between the degree of wetland blockage and the length of the measuring tube is shown in the figure. The length of the measuring tube represents the depth of the wetland matrix. It can be seen that when water is distributed at the upper end of the vertical subsurface flow artificial wetland, the degree of blockage of the surface matrix is ​​the most serious, and then decreases with the depth of the matrix, and the degree of blockage of the bottom matrix is ​​relatively light.

[0064] It can be seen from the above embodiments that the method for locating blockage and judging the degree of blockage of a subsurface artificial wetland disclosed in the present invention can effectively solve the problem of monitoring the degree of blockage during field operation, so as to timely adjust the operation mode and take effective measures to prevent wetland blockage, extend the service life of the wetland, and reduce the renovation costs caused by wetland blockage. Even if renovation is required, the renovation area can be located to the smallest possible range to reduce unnecessary expenses.

[0065] The method described in the present invention is not limited to the embodiments described in the specific implementation manner. Those skilled in the art may derive other implementation manners based on the technical solution of the present invention, which also fall within the technical innovation scope of the present invention.

Claims

1. A method for locating blockage and determining the degree of blockage in a subsurface artificial wetland, the method comprising the following steps: S1. When constructing a subsurface flow artificial wetland, a permeability coefficient measuring tube is pre-installed in the subsurface flow artificial wetland bed, a tube sleeve is provided on the top of the permeability coefficient measuring tube, the top of the permeability coefficient measuring tube is higher than the wetland matrix, the bottom of the permeability coefficient measuring tube is perforated, and the permeability coefficient measuring tube is arranged by a systematic random point distribution method, specifically including: A wetland is divided into several parts of equal area in a grid manner, and a permeability coefficient measuring tube is arranged in each grid. The length l of the permeability coefficient measuring tube arranged in each vertical row and each vertical column is different. The length l of each permeability coefficient measuring tube is an arithmetic progression. The arrangement of the permeability coefficient measuring tube covers wetland matrices of different areas and depths. S2. After the water is first passed through the subsurface artificial wetland, the liquid level of the wetland is controlled by the outlet valve, and the liquid level height of each permeability coefficient measuring tube of different lengths is measured, and the initial permeability coefficient K0 of the corresponding wetland matrix at different depths is obtained by calculation; S3. When it is necessary to determine the degree of blockage of the subsurface artificial wetland, the liquid level height of each permeability coefficient measuring tube of different lengths is measured again, and the corresponding secondary permeability coefficient K of the wetland matrix at different depths is obtained by calculation. n ; S4. The calculated initial permeability coefficient K0 and secondary permeability coefficient K0 at different depths are n Comparison is made to determine the degree of blockage of the subsurface artificial wetland; The steps of measuring the liquid level height of each permeability coefficient measuring tube of different lengths in step S2 are as follows: S21, dividing the permeability coefficient measuring tube and the water outlet valve into several levels in the vertical direction, and controlling the valves at different heights on the water outlet pipe to keep the liquid level of the subsurface flow artificial wetland at different levels so that it just covers the bottom of the permeability coefficient measuring tube to be measured; S22, pouring water continuously into the permeability coefficient measuring tube until it reaches a distance M below the top of the permeability coefficient measuring tube, stopping pouring water, and recording the liquid level at this time as h1; S23, let the water level drop naturally until the reading remains constant at a certain value, record the liquid level height at this time as h2, and record the time taken for the liquid level to drop from h1 to h2 as t; The initial permeability coefficient K0 and the secondary permeability coefficient K n The permeability coefficient in is calculated according to the following formula: Where K is the permeability coefficient, h1 is the liquid level height at time 0, h2 is the liquid level height at time t, d is the pore size of the permeability coefficient measurement tube, L is the underwater length of the perforation of the permeability coefficient measurement tube, and t is the time it takes for the liquid level to drop from h1 to h2; The method for determining the degree of blockage is as follows: For the same subsurface artificial wetland, calculate the clogging degree judgment coefficient When 0< <k1, it means the wetland is slightly blocked. <k2, it means the wetland is moderately blocked. <k3, it means the wetland is seriously blocked. When <k4, it indicates that the wetland is completely blocked, where k1, k2, k3 and k4 are all preset thresholds, k1<k2<k3<k4≤100%.

2. The method for locating blockage and determining the blockage degree of a subsurface artificial wetland according to claim 1, characterized in that: The matrix particle size distribution and laying method in the subsurface artificial wetland bed are uniform, and the wetland matrix is ​​divided into three layers in the vertical direction: an upper isolation layer, a middle functional layer and a bottom supporting layer. The thickness of the upper isolation layer is b, the thickness of the middle functional layer is g, the bottom of the permeability measuring tube is located in the middle functional layer area, and the top of the permeability measuring tube is higher than the matrix layer by a≥20cm.

3. The method for locating blockage and determining the blockage degree of a subsurface artificial wetland according to claim 2, characterized in that: The length l of the permeability coefficient measuring tube is set to: a+b<l<a+b+g.

4. The method for locating blockage and determining the blockage degree of a subsurface flow artificial wetland according to claim 1, characterized in that: The subsurface flow artificial wetland includes a vertical subsurface flow artificial wetland and a horizontal subsurface flow artificial wetland.

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