A wetland substrate and an offline wetland pollution control method

Abstract

The present invention relates to the technical field of pollutant treatment methods, and specifically to a wetland matrix and an offline wetland-based pollution control method. This technical solution uses offline wetland treatment methods to control pollution in urban river water, and can effectively remove major pollutants in urban rivers such as ammonia nitrogen and phosphorus. This technical solution uses a mixture of purple soil and river sand to effectively reduce rainfall runoff flow and remove pollutants such as nitrogen and phosphorus. This technical solution also introduces a new type of iron ore with an ideal phosphorus removal effect. The ratio of purple soil to iron ore determines the control efficiency of the wetland on nitrogen and phosphorus in water. This technical solution solves the technical problems of limited nitrogen and phosphorus removal effects and high preparation costs of wetland matrix materials in the prior art by using common purple soil / river sand and iron ore fillers for enhanced phosphorus removal, and has an ideal prospect for application and promotion.

Description

Technical Field

[0001] The present invention relates to the technical field of pollutant treatment methods, and in particular to a wetland matrix and an off-line wetland pollution control method. Background Art

[0002] Ecological technologies such as artificial wetlands, detention ponds, and infiltration ponds are one of the fundamental ways to solve the problem of urban rainfall runoff pollution. Therefore, the use of hydraulic separation technology to input the initial high-concentration surface runoff into the wetland for treatment is one of the important ways in the existing river restoration. On the basis of hydraulic diversion, the matrix materials in ecological engineering technologies such as artificial wetlands and detention ponds play a vital role in the infiltration capacity of surface runoff and the removal capacity of pollutants.

[0003] Chinese patent CN107162202A provides a vertical flow artificial wetland matrix structure system, which is composed of aquatic plant layer, loach soil layer, gravel layer, sand and gravel layer and fine sand layer from top to bottom; aquatic plants and loach are used in this system to improve the decomposition of organic matter in the soil, and the sand and gravel matrix layer with a special structure can effectively prevent the artificial wetland matrix from being blocked. At the same time, the special sand and gravel matrix layer can improve the filtration efficiency. The system can also produce economic efficiency and reduce costs. However, the artificial wetland matrix requires aquatic plants with high absorption capacity for nitrogen and phosphorus pollutants to achieve the removal of pollutants such as nitrogen and phosphorus in sewage. Chinese patent CN110078203B provides an artificial wetland matrix material and a preparation method thereof. The artificial wetland matrix material is prepared by a roasting process from the following components by mass percentage: oily sludge thermal analysis residue: 60%-65%, fly ash: 25%-30%, and waste glass powder: 5%-10%. The artificial wetland matrix material is made of oily sludge thermal analysis residue, fly ash and waste glass powder as raw materials, and is prepared by a roasting process. During the roasting process, the raw materials cooperate with each other, so that the artificial wetland matrix material has a higher porosity, extremely low oil content, and stronger ammonia nitrogen and phosphorus adsorption performance. Among them, the oil content of the artificial wetland matrix material is less than 0.1%, and its 24h phosphorus adsorption rate is more than 80%, and the 24h ammonia nitrogen adsorption rate is 75%, thereby greatly shortening the operation cycle of the artificial wetland matrix material of the present invention, and then expanding the promotion and application scope of the artificial wetland matrix material of the present invention. However, the preparation process of the artificial wetland matrix material of the above scheme is complicated, and the energy consumption is high, which is not suitable for further application and promotion.

[0004] In summary, it is urgent to develop a wetland matrix that can effectively remove nitrogen and phosphorus, with a simple preparation method suitable for application and promotion, and an offline wetland pollution control method to meet the needs of practical applications. The new wetland matrix needs to have the effect of effectively reducing rainfall runoff flow and removing pollutants, providing candidate matrix materials for urban rainfall runoff pollution control ecological engineering technology. Summary of the invention

[0005] The present invention is intended to provide a wetland matrix to solve the technical problems in the prior art that the nitrogen and phosphorus removal effect of wetland matrix materials is limited and the preparation cost is high.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme:

[0007] A wetland matrix comprises a first filler layer, a second filler layer and a third filler layer arranged in sequence from top to bottom; the filler of the first filler layer is a mixture of purple soil and river sand; the filler of the second filler layer is a mixture of purple soil, river sand and pyrite powder; the filler of the third filler layer is pyrite powder.

[0008] This scheme also provides an application of a wetland matrix in off-line wetland water pollution control.

[0009] The beneficial effects of this technical solution are:

[0010] With the rapid development of social economy and the acceleration of urbanization, urban river water has been seriously polluted and damaged. On the one hand, the construction of urban sewage collection and treatment facilities lags behind the pace of urban construction; on the other hand, rainwater runoff pollution has led to increasing non-point source pollution in urban rivers. Organic matter, ammonia nitrogen and phosphorus are the main pollutants in urban rivers. Off-line wetland treatment of polluted river water (also known as bypass wetland treatment) is a new idea worthy of attention at present. It is a bypass treatment method that builds a treatment system on the river bank and diverts river water for treatment.

[0011] Purple soil and river sand are cheap and can be obtained locally, so they are good materials for the matrix of ecological engineering technology. River sand has good permeability and has a significant effect on reducing rainfall runoff flow, but river sand has weak biological activity and poor effect on removing pollutants. Purple soil has high fertilizer efficiency and strong biological activity, but poor permeability. Mixing purple soil and river sand can simultaneously ensure the effect of reducing rainfall runoff flow and removing pollutants, and has a certain nitrogen and phosphorus removal effect. In order to further remove phosphorus from urban river water, this technical solution also introduces iron ore to further enhance the treatment effect of urban river water.

[0012] Furthermore, the thickness of the wetland matrix is ​​400-600 mm.

[0013] Furthermore, the thicknesses of the first filler layer, the second filler layer and the third filler layer are 100-200 mm, 200-300 mm and 50-100 mm respectively.

[0014] Further, in the first filler layer, the mass ratio of purple soil to river sand is 2:6-3:5.

[0015] Furthermore, in the second filler layer, the mass percentages of purple soil, river sand and pyrite powder are 20-30%, 50-60% and 20% respectively.

[0016] Furthermore, above the wetland matrix is ​​a water layer, the height of which is 200-400 mm; the water layer is wastewater to be treated.

[0017] Furthermore, the flow rate of the wastewater to be treated in the wetland matrix is ​​10-50 mL / min.

[0018] Furthermore, the purple soil and the river sand are obtained by screening through a sieve with an aperture of 2 mm and then drying; the pyrite is obtained by crushing the raw materials and then passing through a 10-mesh sieve.

[0019] Further, the wetland matrix is ​​used to reduce the levels of total nitrogen, total phosphorus and chemical oxygen demand in the water body.

[0020] In summary, the present technical solution adopts a three-layer wetland matrix, which is arranged from top to bottom in sequence as follows: a first packing layer composed of purple soil and river sand, a second packing layer composed of purple soil, river sand and pyrite powder, and a third packing layer composed of pyrite powder. Compared with the technical solution with only a mixed layer of purple soil, river sand and pyrite powder or only two of them, the present technical solution can more comprehensively and effectively remove ammonium nitrogen, nitrate nitrogen, total phosphorus and COD. In addition, the arrangement order of each layer in the three-layer wetland matrix also has a great influence on the removal effect of organic matter. Moreover, the mass fraction of purple soil, river sand and pyrite powder in the mixed matrix needs to be maintained at a certain level in order to effectively improve the treatment effect of ammonium nitrogen, nitrate nitrogen, total phosphorus and COD of the wetland matrix. Purple soil, river sand and pyrite powder have a synergistic effect on the removal effect of pollutants under specific combinations and arrangements.

[0021] Based on the above research results, the wetland matrix of this scheme can be applied to artificial wetlands, retention ponds, infiltration ponds, etc., and hydraulic separation technology can be used to input the initial high-concentration surface runoff into the above-mentioned wetlands for treatment, further solving the problem of urban rainfall runoff pollution. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the technical means used in the following examples and experimental examples are conventional means well known to those skilled in the art, and the materials, reagents, etc. used can be obtained from commercial sources.

[0023] The main filler materials used in this technical solution include: purple soil, river sand and pyrite. Purple soil and river sand are conventional materials in the prior art. The purple soil (density: 1.3g / cm3 ) was taken from Chongqing, which is a common soil type in Chongqing. River sand (density: 1.4g / cm 3 ) is taken from the Jialing River. The above materials are all screened with a sieve with an aperture of 2mm and then dried before use. Purplish soil is a special type of soil in my country. It is the primary soil on purple-red sandstone and shale rich in calcium carbonate in the subtropical region. River sand refers to the building material formed by the natural force of natural stones in river water, the impact and erosion of river water. Pyrite was purchased from Taobao, crushed and sieved through a 10-mesh sieve for use. This scheme uses pure pyrite (theoretically containing 46.67% iron and 53.33% sulfur). Pyrite is an iron disulfide and is a conventional substance in the prior art. Before use, place the pyrite in a reactor and rinse with clean water until the pH value of the effluent is about 6. Then take out the pyrite, drain it and set it aside.

[0024] This scheme simulates an offline wetland to study the wetland matrix. The experimental equipment includes an adsorption column, a water tank and a water pump. The simulated wastewater is pumped from the water tank by a water pump to ensure that the water level of the simulated wastewater remains at the specified water level and is not too low. An overflow pipe is also provided on the adsorption column to discharge excess simulated wastewater at any time to ensure that the water level of the simulated wastewater is not higher than the specified water level. The adsorption column is cylindrical with an inner diameter of 100mm. The adsorption column is filled with fillers, and the height of the fillers is 500mm (when the wetland matrix of this scheme is actually used and water quality treatment is performed, the height of the fillers can be controlled between 400-600mm), and the water level of the simulated wastewater is 300mm above the fillers (the optional range is 200-400mm). During the experiment, the simulated wastewater after passing through the column was continuously collected from the bottom of the adsorption column (the opening below the adsorption column), and the water pump was gradually adjusted to a suitable flow rate for the simulated wastewater to keep the filtration rate in the adsorption column stable. The flow rate of the simulated wastewater in the column was 10-50mL / min. In subsequent experiments, the flow rate was controlled within the range of 25-30mL / min.

[0025] The simulated wastewater was prepared by the following method: NH4CL was used to simulate ammonium nitrogen, KNO3 was used to simulate nitrate nitrogen, KH2PO4 was used to simulate total phosphorus, and C6H 12 O6 Chemical oxygen demand (COD) in simulated wastewater. The simulated wastewater composition is: NH4CL provides NH4 + The mass concentration is 3.5mg / L, KNO3 provides NO3 - The mass concentration is 2.5mg / L, KH2PO4 provides PO4 3- The mass concentration of C6H 12 The mass concentration of O6 is 55 mg / L.

[0026] Place the filler into the adsorption column, start the water pump, and after the filtration rate in the adsorption column stabilizes, take samples from the water outlet of the adsorption column when the adsorption column has been running for 8 hours. Repeat each test 3 times.

[0027] The composition of the filler is as follows:

[0028] Test 1: 500mm filler is mixed with purple soil, river sand and pyrite powder, the mass ratio of the three is 4:4:2, that is, the mass fractions of purple soil, river sand and pyrite powder are 40%, 40% and 20% respectively. Among them, the mass of pyrite powder is calculated by the weight of dry powder before washing with clean water and adjusting pH. The weight of purple soil and river sand is calculated by the weight after drying.

[0029] Test 2: 500mm filler was mixed with purple soil, river sand and pyrite powder, the mass ratio of the three was 5:3:2, that is, the mass fractions of purple soil, river sand and pyrite powder were 50%, 30% and 20% respectively.

[0030] Test 3: The 500mm filler was mixed with purple soil, river sand and pyrite powder in a mass ratio of 3:5:2, i.e. the mass fractions of purple soil, river sand and pyrite powder were 30%, 50% and 20% respectively.

[0031] Test 4: 500mm filler was mixed with purple soil, river sand and pyrite powder, the mass ratio of the three was 2:6:2, that is, the mass fractions of purple soil, river sand and pyrite powder were 20%, 60% and 20% respectively.

[0032] Test 5: The 500mm filler was mixed with purple soil, river sand and pyrite powder, and the mass ratio of the three was 2.5:5.5:2, that is, the mass fractions of purple soil, river sand and pyrite powder were 25%, 55% and 20% respectively.

[0033] Test 6: The 500mm filler is composed of the first filler layer, the second filler layer and the third filler layer from top to bottom. The thickness of the first filler layer, the second filler layer and the third filler layer are 100mm, 300mm and 100mm respectively. The first filler layer is a mixture of purple soil and river sand, and the mass ratio of the two is 2.5:5.5. The second filler layer is a mixture of purple soil, river sand and pyrite powder, and the mass ratio of the three is: 2.5:5.5:2. The third filler layer is pyrite powder.

[0034] Test 7: The 500mm filler is composed of the first filler layer, the second filler layer and the third filler layer from top to bottom. The thickness of the first filler layer, the second filler layer and the third filler layer are 200mm, 200mm and 100mm respectively. The first filler layer is a mixture of purple soil and river sand, and the mass ratio of the two is 2.5:5.5. The second filler layer is a mixture of purple soil, river sand and pyrite powder, and the mass ratio of the three is: 2.5:5.5:2. The third filler layer is pyrite powder.

[0035] Test 8: The 500mm filler is composed of the first filler layer, the second filler layer and the third filler layer from top to bottom. The thicknesses of the first filler layer, the second filler layer and the third filler layer are 100mm, 350mm and 50mm respectively. The first filler layer is a mixture of purple soil and river sand, with a mass ratio of 2.5:5.5. The second filler layer is a mixture of purple soil, river sand and pyrite powder, with a mass ratio of 2.5:5.5:2. The third filler layer is pyrite powder.

[0036] Test 9: The 500mm filler consists of the first filler layer and the second filler layer from top to bottom. The thickness of the first filler layer and the second filler layer are 100mm and 400mm respectively. The first filler layer is a mixture of purple soil and river sand, and the mass ratio of the two is 2.5:5.5. The second filler layer is a mixture of purple soil, river sand and pyrite powder, and the mass ratio of the three is: 2.5:5.5:2.

[0037] Test 10: The 500mm filler consists of a first filler layer and a second filler layer from top to bottom. The thickness of the first filler layer and the second filler layer are 400mm and 100mm respectively. The first filler layer is a mixture of purple soil, river sand and pyrite powder, and the mass ratio of the three is: 2.5:5.5:2. The second filler layer is pyrite powder.

[0038] Test 11: The 500 mm filler consists of a first filler layer and a second filler layer from top to bottom. The thickness of the first filler layer and the second filler layer are 300 mm and 200 mm respectively. The first filler layer is a mixture of purple soil and river sand, and the mass ratio of the two is 2.5:5.5. The second filler layer is pyrite powder.

[0039] Test 12: The 500mm filler is composed of the first filler layer, the second filler layer and the third filler layer from top to bottom. The thickness of the first filler layer, the second filler layer and the third filler layer are 100mm, 300mm and 100mm respectively. The first filler layer is pyrite powder. The second filler layer is a mixture of purple soil, river sand and pyrite powder, and the mass ratio of the three is: 2.5:5.5:2. The third filler layer is a mixture of purple soil and river sand, and the mass ratio of the two is 2.5:5.5.

[0040] Test 13: The 500mm filler was mixed with purple soil, river sand and pyrite powder, and the mass ratio of the three was 2:5:3, that is, the mass fractions of purple soil, river sand and pyrite powder were 20%, 50% and 30% respectively.

[0041] Test 14: 500mm filler was mixed with purple soil, river sand and pyrite powder, the mass ratio of the three was 3:6:1, that is, the mass fractions of purple soil, river sand and pyrite powder were 30%, 60% and 10% respectively.

[0042] The test results are detailed in Tables 1-7. The removal rate (%) was calculated using the average value of each type of pollutant at 8 hours: (the content of pollutants in the initial simulated wastewater - the content of pollutants in the simulated wastewater at 8 hours) / the content of pollutants in the initial simulated wastewater × 100%.

[0043] Tests 3, 4 and 5 all use a mixed matrix composed of purple soil, river sand and pyrite powder to remove pollutants. Using the above mixed matrix, the removal effect of ammonium nitrogen, nitrate nitrogen, total phosphorus and COD is acceptable, among which test 5 is the best, and the removal rates of ammonium nitrogen, nitrate nitrogen, total phosphorus and COD are relatively ideal. In test 1 and test 2, the mass percentage of purple soil is high and the mass percentage of river sand is low, which will not only cause the permeability of the matrix to be unsatisfactory, but also affect the removal effect of pollutants. Although the inventor's previous experiments found that the removal effect of ammonium nitrogen in the mixture of purple soil and river sand is better, and the removal effect of nitrate nitrogen and total phosphorus in pyrite is better. However, after the mixture of purple soil and river sand is mixed according to the ratio of test 1 and test 2, it not only affects the removal effect of ammonium nitrogen, but also affects the performance of pyrite. Therefore, maintaining the mass percentages of purple soil and river sand at 20-30% and 50-60% respectively is most beneficial to the performance of pollutant removal. In the 13th and 14th experiments, the content of pyrite powder was increased and decreased respectively, and it was found that the removal effect of ammonium nitrogen did not change significantly (compared with the 3rd, 4th and 5th experiments), but the removal effect of nitrate nitrogen became worse, and the removal effect of total phosphorus increased with the increase of the content of pyrite powder. Based on the above test results, the subsequent test was carried out using a mixed mode (experiment 5) of purple soil, river sand and pyrite powder = 2.5:5.5:2.

[0044] Experiment 9 used a packing layer of purple soil and river sand combined with a packing layer of a mixture of purple soil, river sand and pyrite powder. Compared with Experiment 5, the removal effect of ammonium nitrogen was enhanced, but the removal effects of nitrate nitrogen and total phosphorus decreased, and the removal effect of COD became better. Experiment 10 used a packing layer of a mixture of purple soil, river sand and pyrite powder combined with a pyrite powder. Compared with Experiment 5, the removal effect of ammonium nitrogen became worse, but the removal effects of nitrate nitrogen and total phosphorus increased, and the removal effect of COD became better. Experiment 11 used a packing layer of a mixture of purple soil and river sand combined with a pyrite powder packing layer. The removal effects of ammonium nitrogen, nitrate nitrogen, total phosphorus and COD were all inferior to those of Experiment 5, which shows that the packing layer of a mixture of purple soil, river sand and pyrite powder is very important for the realization of technical effects.

[0045] Tests 6, 7 and 8 used a three-layer packing solution, and the removal effects of ammonium nitrogen, nitrate nitrogen, total phosphorus and COD were greatly improved compared with Tests 5, 9 and 10. Test 12 changed the order of the pyrite powder layer and the mixture layer of purple soil and river sand compared with Test 6, and the removal effects of ammonium nitrogen, nitrate nitrogen and total phosphorus became worse than that of Test 6, but the removal effect of COD did not change significantly.

[0046] The above test data show that the following technical scheme can produce the best effect for removing pollutants from water bodies: the first packing layer, the second packing layer and the third packing layer are arranged in sequence from top to bottom; the filler of the first packing layer is a mixture of purple soil and river sand; the filler of the second packing layer is a mixture of purple soil, river sand and pyrite powder; the filler of the third packing layer is pyrite powder.

[0047] Table 1:

[0048]

[0049] Table 2:

[0050]

[0051] Table 3:

[0052]

[0053] Table 4:

[0054]

[0055] Table 5:

[0056]

[0057] Table 6:

[0058]

[0059] Table 7:

[0060]

[0061] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A wetland substrate, characterized in that: It comprises a first packing layer, a second packing layer and a third packing layer which are arranged in sequence from top to bottom; the packing of the first packing layer is a mixture of purple soil and river sand; the packing of the second packing layer is a mixture of purple soil, river sand and pyrite powder; the packing of the third packing layer is pyrite powder; in the second packing layer, the mass percentages of purple soil, river sand and pyrite powder are 20-30%, 50-60% and 20% respectively.

2. A wetland substrate according to claim 1, characterized in that: Its thickness is 400-600mm.

3. A wetland substrate according to claim 2, characterized in that: The thicknesses of the first packing layer, the second packing layer and the third packing layer are 100-200 mm, 200-300 mm and 50-100 mm respectively.

4. A wetland substrate according to claim 3, characterized in that: In the first filler layer, the mass ratio of purple soil to river sand is 2:6-3:

5.

5. A wetland substrate according to claim 4, characterized in that: Above the wetland matrix is ​​a water layer, the height of which is 200-400 mm; the water layer is wastewater to be treated.

6. A wetland substrate according to claim 5, characterized in that: The flow rate of the wastewater to be treated in the wetland matrix is ​​10-50 mL / min.

7. A wetland substrate according to claim 6, characterized in that: The purple soil and the river sand are obtained by screening through a sieve with an aperture of 2 mm and then drying; the pyrite is obtained by crushing the raw materials and then passing through a 10-mesh sieve.

8. Use of a wetland substrate according to any one of claims 1 to 7 in off-line wetland water pollution control.

9. The use of a wetland substrate in off-line wetland water pollution control according to claim 8, characterized in that: The wetland substrate is used to reduce the levels of total nitrogen, total phosphorus and chemical oxygen demand in the water body.

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