CN111484132A - Composite artificial wetland system for advanced treatment of tail water and sewage treatment method - Google Patents
Composite artificial wetland system for advanced treatment of tail water and sewage treatment method Download PDFInfo
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Abstract
The invention discloses a composite artificial wetland system for advanced treatment of tail water and a sewage treatment method. The composite artificial wetland system for advanced treatment of tail water comprises a denitrification filter, a vertical subsurface flow artificial wetland and a surface flow artificial wetland which are connected in sequence; a drainage layer, a transition layer, a filter material layer and a covering layer are sequentially paved on the vertical subsurface flow constructed wetland from bottom to top; the filter material layer consists of a first filter material layer, a second filter material layer and a third filter material layer; the covering layer is formed by paving gravels with the particle size of 8-16 mm. The invention solves the problem of difficult denitrification of the artificial wetland in the tail water treatment process by combining the denitrification filter tank, the vertical subsurface flow artificial wetland and the surface flow artificial wetland, enhances the total nitrogen removal effect, and makes up the problems of poor impact load resistance and the like of the denitrification filter tank in the independent use.
Description
Technical Field
The invention relates to the technical field of water treatment, in particular to a composite artificial wetland system for advanced treatment of tail water.
Background
The tail water has the characteristics of low content of biodegradable organic matters, large water fluctuation, low carbon-nitrogen ratio and the like, the tail water after secondary treatment still contains a large amount of pollutants such as nitrogen and phosphorus, and nitrogen in the tail water of a sewage treatment plant in China is mainly nitrate nitrogen. The concentration of ammonia nitrogen in the tail water of a plurality of sewage treatment plants can meet the discharge standard, but the total nitrogen concentration in most of the tail water of the sewage is higher than the discharge standard due to higher concentration of nitrate nitrogen, and the tail water can cause the eutrophication of rivers if being directly discharged into the rivers. Therefore, the existing process needs to be upgraded or an advanced treatment unit needs to be added to carry out advanced treatment on pollutants such as nitrogen so as to meet the discharge standard, reduce the influence of tail water on the received water body and improve the water environment, however, the tail water advanced purification is different from the standard upgrading and upgrading of the conventional sewage treatment plant, the effluent index is stricter, and the surface water standard is usually executed. The concentration of pollutants in tail water of a sewage treatment plant is generally higher in winter, and each index in the surface water standard is strict and has no season difference, so that the difference between the indexes is larger, and the treatment difficulty of the tail water is increased.
The conventional tail water deep treatment methods comprise an activated carbon adsorption method, a membrane separation method, an advanced oxidation method and an artificial wetland method. From the aspect of treatment effect, the effluent quality of the methods can meet the requirements. However, the activated carbon adsorption method and the membrane separation method have short service life, poor pollution resistance, high cost of the advanced oxidation method and unrealistic large-scale popularization. Compared with the prior art, the constructed wetland method has low capital construction investment and operation cost, is simple and convenient to operate, and is more suitable for advanced treatment of secondary effluent of a sewage plant.
The artificial wetland mainly depends on the synergistic effect of wetland fillers, microorganisms and plants, and realizes the removal of water pollutants through interception, precipitation adsorption, oxidation reduction, degradation, absorption and other modes. The main types of the artificial wetland include a surface flow artificial wetland, a vertical subsurface flow artificial wetland and a horizontal subsurface flow artificial wetland. Different types of artificial wetlands have different advantages and disadvantages, wherein the surface flow is simple and convenient to operate, but the hydraulic load is low, the dirt-removing capacity is limited, and compared with the vertical subsurface flow wetland, although the manufacturing cost is higher, the hydraulic load is large, the pollutant removing effect is good, and the sanitary condition is also good. However, because the removal of pollutants by the artificial wetland depends on the degradation of wetland microorganisms to a great extent, the removal of pollutants, particularly total nitrogen, by the artificial wetland system is limited to a certain extent when tail water containing a large amount of humus, surfactants and other trace refractory organic matters is treated. In addition, in a low-temperature environment, the growth and reproduction rate and activity of microorganisms are also inhibited, and the pollutant purification capacity is obviously reduced. With the increase of sewage treatment demand, a single wetland unit sometimes cannot meet the relevant treatment demand. The combination of various types of artificial wetlands can complement the advantages and the disadvantages of a single artificial wetland, the improvement on the sewage quality is higher than the application of a single wetland system, but the artificial wetland system is easily influenced by the temperature and is difficult to fully play a role in treating tail water with poor biodegradability, low carbon-nitrogen ratio and difficult denitrification.
The denitrification filter tank is used as a novel sewage treatment technology, is essentially characterized in that sewage flows through a biological membrane on a filter material, pollutants are decomposed by utilizing the microbial action metabolism of the biological membrane, so that the sewage is purified, and has the characteristics of small floor area, good effluent quality, good denitrification effect, small sludge production amount, modular structure and the like, in view of controlling the total nitrogen of the effluent to be the key for realizing the standard IV, the total nitrogen of the effluent of the existing sewage plant is mainly nitrate nitrogen, and the main way for reducing the total nitrogen is biological denitrification, so the deep denitrification treatment of the sewage by utilizing the denitrification filter tank is an effective way, the denitrification filter tank in the form of integrated equipment does not need aeration as a sewage deep treatment process, has high operation hydraulic load, small floor area, small operation influence by natural environment, obvious total nitrogen removal capacity, can synchronously remove SS and total phosphorus, the construction cost and the case operation cost are low, the denitrification filter tank in the form of integrated equipment has high degree of equipment integration automatic control, is convenient to install, has good adaptability, the advantages of short period, is used as an ideal for strengthening the effect, the overall operation of the denitrification filter tank, the total nitrogen removal efficiency is relatively low, the total nitrogen removal efficiency of the integrated equipment is relatively poor, the total nitrogen removal of the integrated equipment, the filtration tank is relatively high, the total nitrogen removal efficiency of the integral denitrification filter tank is relatively poor, the total sewage treatment of the integral denitrification filter tank is relatively low, the total sewage treatment of the integral denitrification filter tank is relatively high integral equipment, the integral denitrification filter tank is relatively difficult to meet the requirement of the integral.
Disclosure of Invention
The purpose of the invention is as follows: the invention provides a composite artificial wetland system for advanced treatment of tail water, wherein a denitrification filter tank is combined with an artificial wetland treatment process, so that the impact resistance of the denitrification filter tank can be improved. The invention also provides a treatment method, which gives full play to the advantages in the aspect of removing the total nitrogen and can make up the deficiency of the denitrification filter tank in the effect of removing the total phosphorus.
The technical scheme is as follows: the invention relates to a composite artificial wetland system for advanced treatment of tail water, which is characterized by comprising a denitrification filter tank, a vertical subsurface flow artificial wetland and a surface flow artificial wetland which are sequentially connected; a drainage layer, a transition layer, a filter material layer and a covering layer are sequentially paved on the vertical subsurface flow constructed wetland from bottom to top; the drainage layer consists of a first drainage layer and a second drainage layer positioned above the first drainage layer, the first drainage layer is formed by paving gravels with the grain diameter of 50-60 mm, and the second drainage layer is formed by paving gravels with the grain diameter of 16-32 mm; the transition layer is formed by paving gravels with the particle size of 8-16 mm; the filter material layer consists of a first filter material layer, a second filter material layer and a third filter material layer, wherein the first filter material layer is formed by laying iron matrix and biochar with the particle size of 5-15 mm, the second filter material layer is formed by laying limestone and zeolite with the particle size of 5-15 mm, and the third filter material layer is formed by laying biochar with the particle size of 5-15 mm; the covering layer is formed by paving gravels with the particle size of 8-16 mm.
The thickness ratio of the first drainage layer, the second drainage layer, the first filter material layer, the second filter material layer, the third filter material layer and the covering layer is 0.9-1.1:1.9-2.1:3.9-4.1:7.9-8.1:5.9-6.1: 1.9-2.1.
The thickness of the first drainage layer is 45-55mm, the thickness of the second drainage layer is 95-105mm, the thickness of the transition layer is 95-105mm, the thickness of the first filter material layer is 195-plus-material 205mm, the thickness of the second filter material layer is 395-plus-material 405mm, the thickness of the third filter material layer is 295-plus-material 305mm, and the thickness of the covering layer is 95-105 mm.
Preferably, the thickness of the first drainage layer is 50mm, the thickness of the second drainage layer is 100mm, the thickness of the transition layer is 100mm, the thickness of the first filter material layer is 200mm, the thickness of the second filter material layer is 400mm, the thickness of the third filter material layer is 300mm, and the thickness of the covering layer is 100 mm.
In the first filter material layer, the volume ratio of the iron matrix to the biochar is 1: 9.
In the second filter material layer, the volume ratio of the limestone to the zeolite is 1:1.
The upper layer of the covering layer is provided with a plant layer, the planting density of the plant layer is 16-18 plants per square meter, and the planted plants are cyperus alternifolius, iris tectorum and allium fistulosum.
Preferably, the planting density of the planting plant layer in the covering layer is 16 plants per square meter, the planting area of the windmill grass accounts for 37.5 percent of the total area, the iris accounts for 31.25 percent, and the allium mongolicum regel accounts for 31.25 percent.
The density of the plants planted in the surface flow constructed wetland is 9-10 plants per square meter.
Preferably, the planting density in the surface flow artificial wetland is 9 plants per square meter, and the planted plants are canna and dwarf cold-resistant tape grass.
And a back flushing pipeline is arranged in the vertical subsurface flow artificial wetland and is provided with a first branch pipe and a second branch pipe which is vertically arranged with the first branch pipe and is laid on the drainage layer of the vertical subsurface flow artificial wetland.
A water collecting system and a water distribution system are arranged in the vertical subsurface flow constructed wetland, the water distribution system is distributed on the top layer of the covering layer, and the water distribution system is communicated with a water outlet of the denitrification filter tank; the water collecting system is positioned on the drainage layer of the vertical subsurface flow constructed wetland and consists of a plurality of water collecting pipes which are distributed in parallel.
The sewage treatment method using the composite artificial wetland system for advanced tail water treatment comprises the following steps:
(a) introducing sewage to be treated into a denitrification filter, and enabling the sewage treated by the denitrification filter to flow through the vertical subsurface flow constructed wetland through a water distribution system arranged on the upper layer of the vertical subsurface flow constructed wetland;
(b) the sewage treated by the vertical subsurface flow artificial wetland flows into the surface flow artificial wetland for further treatment through a water collecting system arranged on a drainage layer of the vertical subsurface flow artificial wetland;
(c) when the vertical subsurface flow constructed wetland is blocked, the flushing water flow is introduced from the back flushing pipeline to clean the vertical subsurface flow constructed wetland.
Has the advantages that: (1) according to the invention, by combining the denitrification filter tank, the vertical subsurface flow constructed wetland and the surface flow constructed wetland, on one hand, anaerobic, anoxic and aerobic environments beneficial to removal of nitrogen and phosphorus pollutants are provided, on the other hand, the combination of the constructed wetland and the denitrification filter tank can realize advantage complementation of each treatment unit, so that the problem of difficulty in nitrogen removal of the constructed wetland in the tail water treatment process is solved, the removal effect of total nitrogen is enhanced, the problems of poor impact load resistance and the like of the denitrification filter tank in separate use are solved, the advantages in the aspect of total nitrogen removal are fully exerted, and the defect of the denitrification filter tank in the total phosphorus removal effect can be overcome; (2) the vertical subsurface flow constructed wetland of the invention is a novel and efficient wetland filler combination, can maintain the activity of microorganisms in a low-temperature state, and overcomes the defects of low adsorption performance to pollutants and poor microbial adhesion of the traditional constructed wetland taking soil, gravel, broken stone and the like as filler components, each filler of the invention can also strengthen the removal effect to the pollutants through interaction while giving full play to the unique advantages of the filler, the iron matrix micro-electrolysis layer of the invention generates a large amount of active reductive hydrogen and ferrous ions in the iron matrix during the electrolysis process, so that the complex organic matters in tail water are subjected to the actions of ring opening, chain breaking and the like, the macromolecule degradation-resistant organic matters in the tail water are promoted to be converted into micromolecule organic matters, and then are degraded by the microorganisms, and meanwhile, secondary and trivalent iron ions can be generated in the electrolysis process in the iron matrix, and can form an electron transfer system participating in the life activities of the microorganisms, the electron transfer rate of microbial cells is accelerated, the activity of microbes is improved, meanwhile, enough electrons can be provided for reducing nitrate nitrogen by microbial communities, and the organic matters dissolved by the biochar in the filler can promote the enrichment of denitrifying microbes, so that the problem of low carbon nitrogen content is solved, and the denitrification effect is enhanced; (3) the water collecting system with the functions of water collecting, ventilating and backwashing is adopted, so that a dead water area can be reduced, the oxygen content in the wetland is increased while effluent of the wetland is effectively collected, the microbial activity of the wetland is enhanced, and in addition, when the wetland is blocked, the wetland can be aerated through the backwashing pipe, so that the hydraulic condition of the wetland is improved, and the blocking problem is relieved; (4) the invention optimizes wetland plant configuration, and selects plant collocation of the pinwheel, the iris and the allium fistulosum in the vertical subsurface flow artificial wetland, wherein the pinwheel has higher removal rate of COD. The allium mongolicum regel has higher removal rate on organic matters, ammonia nitrogen, phosphate and heavy metals in sewage. The iris has good carbon fixing and oxygen releasing capacity, and simultaneously has good effect on removing total nitrogen and total phosphorus, the three plants complement each other in removal of COD, total nitrogen and total phosphorus, the effluent quality can be effectively stabilized, and in addition, the aerobics herbs, the iris and the allium fistulosum have good cold resistance and keep good growth situation in winter; (5) canna and tape grass are planted in the surface flow constructed wetland, wherein the canna has low requirement on the environment, the environment can be beautified, the removal effect on nitrate nitrogen is good, the stress resistance is good, the effects of purifying water quality, repairing the environment and the like are achieved, the tape grass can absorb excessive nutritive salt and has strong pollutant adsorption capacity, the removal effect of pollutants in water can be effectively enhanced by combining and matching two plants, and the tape grass has a good landscape effect, in the surface flow constructed wetland, sewage slowly flows through the surface of a bed body, the pollutants are removed mainly by means of plant stems, rods and biomembranes growing on the surface of the bed body under water, and the quality of effluent water is further improved; (6) the composite artificial wetland system integrates the filtering function and the biological denitrification function, and can effectively control the eutrophication problem of the water body and improve the water quality when being applied to the deep denitrification of the sewage; the sewage treatment process is simple, and the operation is convenient and the management is easy in the operation process. Except that the water inlet of the denitrification filter tank is pressurized and lifted by a peristaltic pump, the water flow passes through liquid level differences in the process of passing through different reaction units and is carried out by gravity water distribution, so that the energy consumption is low; (7) according to the invention, the iron-carbon matrix layer is additionally arranged in the wetland filler to further strengthen the function of removing nitrogen and phosphorus of the wetland, and the composite artificial wetland system suitable for advanced treatment of tail water is formed by combining all process advantages.
Drawings
FIG. 1 is a schematic structural diagram of a composite artificial wetland system for advanced treatment of tail water according to the invention;
FIG. 2 is a schematic structural diagram of a water distribution system in the vertical subsurface flow constructed wetland of the invention;
FIG. 3 is a schematic view of the structure of water distribution holes in the water distribution branch pipes according to the present invention;
FIG. 4 is a schematic structural diagram of a water collecting system in the vertical subsurface flow constructed wetland of the invention;
FIG. 5 is a schematic view of the distribution of water collection holes on the water collection pipe of the present invention;
fig. 6 is a schematic structural diagram of a back flushing pipeline in the vertical subsurface flow constructed wetland.
Detailed Description
Example 1: as shown in fig. 1, the composite artificial wetland system for deep treatment of tail water in the invention comprises a denitrification filter tank 1, a vertical subsurface flow artificial wetland 2 and a surface flow artificial wetland 3 which are connected in sequence.
The peristaltic pump is arranged at the front end of the denitrification filter tank 1, a water outlet at the top of the denitrification filter tank 1 is connected with a water distribution system of a vertical flow constructed wetland 2 through a UPVC plastic pipe, the denitrification filter tank 1 adopted in the embodiment is an upflow denitrification filter tank (Shanghai Qingchuan environmental engineering technology limited company) with the height of 2 meters and the diameter of 1.2 meters, the denitrification filter tank 1 is arranged at the front end of the constructed wetland, sewage can be filtered and biologically denitrified in advance, and when the denitrification filter tank is used for deep denitrification of the sewage, the eutrophication problem of a water body can be effectively controlled, and the water quality is improved. In the embodiment, a treatment system integrating biological denitrification and filtration functions is adopted, which mainly comprises a tank body, a water inlet and outlet system, a filter material in the tank and a filter material backwashing system, wherein a filler is used as a carrier, and the denitrification mechanism of the denitrification filter tank is to convert nitrate nitrogen into gaseous nitrogen (mainly nitrogen) through denitrification action by using denitrifying bacteria attached to the surface of the filler under the anaerobic condition to complete the denitrification reaction process. Nitrogen generated in the denitrification process can cause sewage to flow between the media in a winding way, so that the contact between microorganisms and water flow is enhanced, and the filtering efficiency is improved.
As shown in fig. 2, in the present invention, a "rich" shaped water distribution system 4 is disposed on the top layer of the vertical subsurface flow constructed wetland 2, and the placement direction of the "rich" shaped water distribution system 4 can be arbitrarily selected, in this embodiment, the main water distribution pipe 41 of the water distribution system 4 is disposed perpendicular to the water feeding direction of the denitrification filter 1 (disposed perpendicular to the length of the vertical subsurface flow constructed wetland), the branch water distribution pipes 42 communicated with the main water distribution pipe 41 are disposed perpendicular to the main water distribution pipe 41 at intervals in parallel, and fig. 3 is a schematic structural diagram of the water distribution holes on the branch water distribution pipes 42, so that the sewage treated by the denitrification filter 1 can be uniformly distributed on the vertical subsurface flow constructed wetland 2. Specifically, the water distribution system 4 is composed of a main water distribution pipe 41 and branch water distribution pipes 42, the pipe diameter of which is 20mm, the main water distribution pipe 41 is provided with a gate to adjust the inflow rate of the vertical subsurface flow constructed wetland, each branch water distribution pipe 42 is provided with a water outlet hole under the cross section, and a gate is arranged at the same length position to control the water outlet amount of each branch pipe.
A drainage layer 21, a transition layer 22, a filter material layer 23 and a covering layer 24 are sequentially paved on the vertical subsurface flow constructed wetland 2 from bottom to top;
the drainage layer 21 consists of a first drainage layer and a second drainage layer positioned above the first drainage layer, wherein the first drainage layer is formed by paving gravels with the grain diameter of 50-60 mm, and the thickness of the first drainage layer is 50 mm; the second drainage layer is formed by paving gravels with the particle size of 16-32 mm, and the thickness of the second drainage layer is 100 mm. The transition layer is formed by paving gravels with the particle size of 8-16 mm, and the thickness of the transition layer is 100 mm.
The filter material layer 23 consists of a first filter material layer 231, a second filter material layer 232 and a third filter material layer 233, wherein the first filter material layer 231 is formed by laying an iron matrix and biochar with the particle size of 5-15 mm, the iron matrix is purchased from nine environmental science and technology companies in Hunan, the biochar is purchased from a firm water purification material factory with Hongchang mouth in North mountain of China, the volume ratio of the iron matrix to the biochar is 1:9, and the thickness is 200 mm; the second filter material layer 232 is formed by paving limestone and zeolite with the particle size of 5-15 mm, the volume ratio of the limestone to the zeolite is 1:1, and the thickness is 400 mm; the third filter material layer 233 is a charcoal layer formed by laying a charcoal layer with a particle size of 5-15 mm, and the thickness is 100 mm.
The covering layer is formed by paving gravels with the particle size of 8-16 mm, a plant layer is arranged on the upper layer of the covering layer, the planting density of the plant layer is 16 plants/square meter, the planted plants are windmill grass, iris and allium mongolicum regel, the planting area of the windmill grass accounts for 37.5% of the total area, the iris occupies 31.25%, and the allium mongolicum regel accounts for 31.25%.
As shown in fig. 4, the water collecting system 5 in this embodiment is located at the lower layer of the drainage layer of the vertical subsurface flow constructed wetland and is used for collecting the treated water flowing out of the drainage layer, the water collecting system 5 is composed of a plurality of water collecting pipes 51 distributed in parallel, and a plurality of water collecting holes 52 are distributed on the water collecting pipes 51, in this embodiment, each water collecting pipe 51 has the same flow direction as the flow direction of the water from the denitrification filter 1, specifically, is composed of a water collecting pipe with a pipe diameter of 50mm, a connecting pipe between the water collecting pipes, a tee joint and a 90-degree elbow, and is horizontally laid along the bottom of the filter.
As shown in fig. 5, in order to improve the efficiency of the water collecting system 5 for collecting the water flow, the water collecting holes 52 of the water collecting pipe 51 are radially distributed and surround the circumferential surface of the upper half of the water collecting pipe 51.
As shown in figure 6, a back washing pipeline 6 is arranged in the vertical subsurface flow constructed wetland 2, the back washing pipeline 6 is provided with a first branch pipe 61, in the invention, in order to prevent the water collecting pipe 51 from cracking, a thickened UPVC pipe is adopted, and supporting square steel is arranged below each water collecting pipe 51 along the length direction of the tank body. One ends of a plurality of water collecting pipes 51 are communicated through a connecting pipe 53, the other ends of the water collecting pipes are connected with a vertical backwashing pipe 61 through a 90-degree elbow, the water collecting pipes can be connected into a device for backwashing when the substrate is blocked, and can be used as ventilation vertical pipes in a normal operation state, so that the content of dissolved oxygen in the wetland is improved. In addition, the bottom of the tank body is provided with a drainage port with the diameter of 50mm, and the water dropping reoxygenation can be carried out under necessary conditions.
The water outlet pipe of the vertical subsurface flow constructed wetland water collection system 2 is connected with the water inlet pipe of the surface constructed wetland 3, the sewage treated by the vertical subsurface flow wetland falls into the surface flow constructed wetland by utilizing the liquid level difference through the connecting pipe, and finally flows out of the wetland system through the opening on the water outlet side of the surface flow wetland. The density of the plants planted in the surface flow artificial wetland 3 is 9 plants/square meter, and the planted plants are canna and dwarf cold-resistant tape grass which are uniformly planted.
In the embodiment, the length, width and height of the vertical undercurrent artificial wetland pool body are 2.5 meters, 2 meters and 1.5 meters, and the designed water depth is 1.25 meters; the length of the surface flow artificial wetland tank body is 2.5 meters, the width is 1 meter, the height is 1 meter, the designed water depth is 0.3 meter, and small-particle-size gravels with the particle size of 3-5mm are paved inside the tank body.
The sewage treatment method using the composite artificial wetland system in the embodiment comprises the following steps:
(a) introducing sewage to be treated into a denitrification filter, and enabling the sewage treated by the denitrification filter to flow through the vertical subsurface flow constructed wetland through a water distribution system arranged on the upper layer of the vertical subsurface flow constructed wetland;
(b) the sewage treated by the vertical subsurface flow artificial wetland flows into the surface flow artificial wetland for further treatment through a water collecting system arranged on a drainage layer of the vertical subsurface flow artificial wetland;
(c) when the vertical subsurface flow constructed wetland is blocked, the flushing water flow is introduced from the back flushing pipeline to clean the vertical subsurface flow constructed wetland.
Application example 1, taking 10g of each of an iron matrix, a mixture of the iron matrix and biochar (volume ratio is 1:1) (iron-carbon matrix) and the biochar, respectively placing the mixture in a beaker with the size of 100m L, adding tail water with the size of 50m L, stirring the mixture by using a glass rod, standing the mixture for 17 hours, taking supernatant in each beaker, and detecting to obtain the following results:
TABLE 1 treatment effect of different components on tail water quality
| Ammonia nitrogen (mg/L) | Total phosphorus (mg/L) | Total nitrogen (mg/L) | COD(mg/L) | |
| Quality of tail water | 8.9 | 0.36 | 20.7 | 64 |
| Iron matrix | 4.7 | 0.22 | 18.4 | 43 |
| Biochar | 2.2 | 0.35 | 12.8 | 43 |
| Iron carbon matrix | 2.9 | 0.21 | 10.1 | 7 |
Application example 2:
firstly, the quality of tail water introduced into the composite artificial wetland is detected, the ammonia nitrogen content is 8.9 mg/L, the total phosphorus content is 0.36 mg/L, the total nitrogen content is 18.4 mg/L, the COD content is 64 mg/L, and the wetland is 2m3The treatment capacity of the tail water is that the water entering the wetland is treated by a denitrification filter for 2 hours), after the device operates for 43 days, effluent water is sampled from three water outlets of the denitrification filter, the vertical subsurface flow artificial wetland and the surface flow artificial wetland, water quality detection is carried out immediately after sampling, and the effluent total nitrogen, ammonia nitrogen, COD and total phosphorus are detected by respectively adopting a potassium persulfate oxidation ultraviolet spectrophotometry method, a salicylic acid-hypochlorite method, a potassium dichromate method and an ammonium molybdate spectrophotometry method, and the effluent water indexes of each process are as follows:
TABLE 2 treatment effect of different treatment processes on the quality of tail water
From the results in table 2, it is seen that after the tail water is treated by the denitrification filter, the content of ammonia nitrogen and the content of total nitrogen are basically unchanged, the content of COD and total phosphorus are reduced, after the tail water treated by the self-denitrification filter is treated by the vertical subsurface flow constructed wetland, the content of ammonia nitrogen, total phosphorus and total nitrogen are significantly reduced, and after the tail water is further treated by the surface flow constructed wetland, the quality of the effluent is further improved.
Application example 3:
the structure of the embodiment 1 is utilized to treat sewage, the water quality of inlet water is that the total nitrogen content is 7.2 mg/L, the total phosphorus content is 0.46 mg/L content is 48 mg/L, and after the sewage is introduced into the denitrification filter tank 1 to be treated for 2 hours, the amount of the inlet water is 2m3The flow of/d enters a vertical subsurface flow artificial wetland water collecting system 2 and passes through a surface artificial wetland 3 at the flow speed of 0.295m/sThe water inlet pipe and the water outlet pipe finally flow out of the wetland system. And immediately detecting the water quality after taking the water in the denitrification filter tank and the water out of the surface flow artificial wetland.
The result shows that the total nitrogen reaches the national first-class A standard (within 15 mg/L) and is reduced to 2.75 mg/L0 from the inlet water of 7.2 mg/L, reaches the national quasi-four-class water standard (within 5 mg/L1), the total phosphorus reaches the national first-class A standard (within 0.5 mg/L) and is reduced to 0.17 mg/L from the inlet water of 0.46 mg/L, reaches the national quasi-four-class water standard (within 0.3 mg/L), the COD reaches 48 mg/L, reaches the national first-class A standard (within 50 mg/L) and is reduced to 13.5 mg/L from the inlet water of 30 mg/L.
After tail water is treated by the composite artificial wetland, the maximum removal rate of COD is 71.88 percent and is basically stabilized between 56.79 percent and 71.88 percent, the maximum removal rate of total nitrogen is 61.81 percent and is basically stabilized between 41.67 percent and 61.81 percent, and the maximum removal rate of total phosphorus is 63.04 percent and is basically stabilized between 41.67 percent and 63.04 percent.
Application example 4: after the process is operated for 5 days, the water inlet of the denitrification filter and the water outlet of the surface of the process are respectively sampled (the wetland is 2 m)3The treatment capacity of the tail water is that the water entering the wetland is treated by a denitrification filter for 2 hours), the COD of the effluent is detected by a potassium dichromate method immediately after sampling, the total nitrogen is detected by a potassium persulfate oxidation ultraviolet spectrophotometry method, the average value of the COD of the influent is 51.20 mg/L, the average value of the total nitrogen is 8.64 mg/L, the average value of the COD of the effluent is 17.10 mg/L, the average value of the total nitrogen is 4.37 mg/L, the corresponding removal rate is calculated by using the detection result, the obtained result is as shown in the following table, the average removal rate of the total nitrogen is 49.8 percent, the average removal rate of the COD is 65.8 percent, and the purification effect of the prior art (a biochemical and ecological combined artificial wetland system for the tail water of the urban sewage treatment plant is researched [ J]Environmental engineering, 2015, 33 (07): 46-50.) compared with the prior art, the process can effectively improve the quality of the sewage.
Claims (10)
1. A composite artificial wetland system for advanced treatment of tail water is characterized by comprising a denitrification filter tank, a vertical subsurface flow artificial wetland and a surface flow artificial wetland which are connected in sequence; a drainage layer, a transition layer, a filter material layer and a covering layer are sequentially paved on the vertical subsurface flow constructed wetland from bottom to top; the drainage layer consists of a first drainage layer and a second drainage layer positioned above the first drainage layer, the first drainage layer is formed by paving gravels with the grain diameter of 50-60 mm, and the second drainage layer is formed by paving gravels with the grain diameter of 16-32 mm; the transition layer is formed by paving gravels with the particle size of 8-16 mm; the filter material layer consists of a first filter material layer, a second filter material layer and a third filter material layer, wherein the first filter material layer is formed by laying iron matrix and biochar with the particle size of 5-15 mm, the second filter material layer is formed by laying limestone and zeolite with the particle size of 5-15 mm, and the third filter material layer is formed by laying biochar with the particle size of 5-15 mm; the covering layer is formed by paving gravels with the particle size of 8-16 mm.
2. The composite artificial wetland system for advanced tail water treatment according to claim 1, wherein the thickness ratio of the first drainage layer, the second drainage layer, the transition layer, the first filter material layer, the second filter material layer, the third filter material layer and the covering layer is 0.9-1.1:1.9-2.1: 1.9-2.1:3.9-4.1:7.9-8.1:5.9-6.1: 1.9-2.1.
3. The composite artificial wetland system for the advanced treatment of tail water as claimed in claim 2, wherein the thickness of the first drainage layer is 45-55mm, the thickness of the second drainage layer is 95-105mm, the thickness of the transition layer is 95-105mm, the thickness of the first filter material layer is 195-.
4. The composite artificial wetland system for advanced tail water treatment according to claim 1, wherein the volume ratio of the iron matrix to the biochar in the first filter material layer is 1: 9.
5. The composite artificial wetland system for advanced tail water treatment according to claim 1, wherein the volume ratio of limestone to zeolite in the second filter material layer is 1:1.
6. The complex constructed wetland system for advanced treatment of tail water of claim 1, wherein a plant layer is arranged on the upper layer of the covering layer, the plant layer is planted at a density of 16-18 plants per square meter, and the planted plants are windmill grass, iris and allium fistulosum.
7. The composite type artificial wetland system for advanced tail water treatment according to claim 1, wherein the plant density of the surface flow artificial wetland is 9-10 plants per square meter.
8. The composite type constructed wetland system for advanced tail water treatment according to claim 1, wherein a back flush pipeline is arranged in the vertical subsurface flow constructed wetland, and the back flush pipeline is provided with a first branch pipe and a second branch pipe which is vertically arranged with the first branch pipe and is laid on the drainage layer of the vertical subsurface flow constructed wetland.
9. The composite artificial wetland system for advanced tail water treatment according to claim 1, wherein a water collecting system and a water distributing system are arranged in the vertical subsurface flow artificial wetland, the water distributing system is distributed on the top layer of the covering layer, and the water distributing system is communicated with a water outlet of the denitrification filter; the water collecting system is positioned on the drainage layer of the vertical subsurface flow constructed wetland and consists of a plurality of water collecting pipes which are distributed in parallel.
10. The sewage treatment method of the composite type artificial wetland system for the advanced treatment of the tail water according to claim 1, which comprises the following steps:
(a) introducing sewage to be treated into a denitrification filter, and enabling the sewage treated by the denitrification filter to flow through the vertical subsurface flow constructed wetland through a water distribution system arranged on the upper layer of the vertical subsurface flow constructed wetland;
(b) the sewage treated by the vertical subsurface flow artificial wetland flows into the surface flow artificial wetland for further treatment through a water collecting system arranged on a drainage layer of the vertical subsurface flow artificial wetland;
(c) when the vertical subsurface flow constructed wetland is blocked, the flushing water flow is introduced from the back flushing pipeline to clean the vertical subsurface flow constructed wetland.
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