Reed-charcoal vertical subsurface flow constructed wetland system and operation method thereof

Abstract

The invention belongs to the technical field of constructed wetlands, and particularly relates to a reed-charcoal vertical subsurface flow constructed wetland system which comprises a constructed wetland and an aeration device, the constructed wetland sequentially comprises a plain soil layer, waterproof geotechnical cloth, an air stone layer, a large-particle rubble layer, a medium-particle rubble layer, a small rubble and charcoal mixed layer, a coarse river sand layer and a water body layer from bottom to top; and planting reeds in the coarse river sand layer. The reed-biochar vertical subsurface flow constructed wetland system has the beneficial effects that in the reed-biochar vertical subsurface flow constructed wetland system, the small broken stone and biochar mixed layer and the reed root system are used, the ratio of small broken stone to biochar is controlled, biological adsorption and degradation effects are utilized, and aeration time and conditions are controlled, so that effective switching between an aerobic environment and an anaerobic environment in the wetland system is ensured; therefore, COD, NH4 < + >-N, NO3 <->-N, TN and TP can be effectively removed.

Description

Technical Field

[0001] The invention belongs to the technical field of artificial wetlands, and in particular relates to a reed-biochar vertical subsurface flow artificial wetland system and an operation method thereof. Background Art

[0002] With the continuous development of the global economy and society, the population has grown rapidly, and the demand for livestock and poultry products such as meat, eggs and milk has also increased, leading to the rapid expansion of the livestock and poultry farming industry. However, with the expansion of the scale of the farming industry, environmental pressure has also increased, especially the large amount of farming wastewater discharge, which has become an urgent problem to be solved.

[0003] At present, a variety of wastewater treatment technologies have been applied to the treatment of livestock and poultry wastewater, such as the traditional activated sludge process (SBR), membrane reactor (MBR), new microbial electrolysis cell (MEC), microalgae technology, etc. However, these technologies are often plagued by high costs and scale limitations in practical applications, making them difficult to promote and apply on a large scale. Constructed wetland technology is a wastewater treatment technology with large treatment capacity, low cost and environmental friendliness. It simulates the water purification function of natural wetlands, combines the joint action of plants, substrates and microorganisms, and uses physical, chemical and biological processes to remove pollutants in wastewater. Although artificial wetlands have achieved certain results in treating livestock and poultry wastewater, facing the huge total amount of aquaculture wastewater in the world, the existing artificial wetland treatment efficiency is still insufficient, and the removal rate of organic matter in wastewater is low. Summary of the invention

[0004] In view of the above problems, the present invention provides a reed-biochar vertical subsurface flow artificial wetland system and an operation method thereof.

[0005] The present invention relates to a reed-biochar vertical subsurface flow artificial wetland system, comprising an artificial wetland and an aeration device; The artificial wetland is composed of a plain soil layer, a waterproof geotextile, an air stone layer, a large-grained gravel layer, a medium-grained gravel layer, a small-grained gravel-biochar mixed layer, a coarse river sand layer and a water layer from bottom to top; reeds are planted in the coarse river sand layer.

[0006] Preferably, the compaction coefficient of the bare soil layer is ≥0.95; the thickness of the waterproof geotextile is 2 mm; and the thickness of the air stone layer is 10 mm.

[0007] Preferably, the thickness of the large-particle gravel layer is 100 m, and the particle size range of the large-particle gravel is 40 mm to 70 mm.

[0008] Preferably, the thickness of the medium-grained gravel layer is 250 mm, and the particle size range of the medium-grained gravel is 20 mm to 40 mm.

[0009] Preferably, the thickness of the small gravel-biochar mixed layer is 150 mm, the small gravel and biochar are mixed in a volume ratio of 1:1, and the particle size range of the small gravel is 5 mm to 20 mm.

[0010] Preferably, the thickness of the coarse river sand layer is 150 mm, and the particle size of the coarse river sand is less than 5 mm; the water depth in the water body layer is less than 700 mm.

[0011] Preferably, the aeration device comprises a rubber hose sheathed with a PVC tube and an aeration pump, the rubber hose sheathed with the PVC tube is connected to the aeration pump, and one end of the rubber hose sheathed with the PVC tube away from the aeration pump is connected to the air stone layer.

[0012] Preferably, the diameter of the PVC tube is 20 mm, and the diameter of the rubber hose is 10 mm.

[0013] The present invention also relates to an operation method of a reed-biochar vertical subsurface flow artificial wetland system, wherein the reed-biochar vertical subsurface flow artificial wetland system is used to treat wastewater, and the specific water pollutants treated include 400 mg / L COD, 80 mg / L NH4 + -N, 5mg / L NO3 - -N, 85 mg / L TN and 8 mg / L TP.

[0014] Preferably, intermittent aeration is adopted; the total daily aeration time is 6 hours, specifically: 3-4 o'clock, 7-8 o'clock, 11-12 o'clock, 15-16 o'clock, 19-20 o'clock and 23-24 o'clock every day; the aeration flow rate is 0.05L / min; the operation time is May-July every year.

[0015] Compared with the prior art, the advantages and positive effects of the present invention are: (1) The reed-biochar vertical subsurface flow constructed wetland system has high wastewater treatment efficiency and high removal rate of organic matter in wastewater, especially COD and NH4 + -N、NO3 - -N, TN and TP; (2) In the reed-biochar vertical subsurface flow artificial wetland system, a small gravel biochar mixed layer and a reed root system are used, and the ratio of small gravel to biochar is controlled. The biological adsorption and degradation effect is utilized, and the aeration time and conditions are controlled to ensure the effective switching between aerobic and anaerobic environments in the wetland system, thereby effectively removing COD and NH4 + -N、NO3 - -N, TN and TP; (3) The reed-biochar vertical subsurface flow constructed wetland system can effectively prevent pollutants from infiltrating into the soil layer by controlling the thickness of each layer and the particle size of large-grained gravel, medium-grained gravel, small gravel and coarse river sand, increase the dissolved oxygen content in the wetland system, provide good filtration and support for the water body, and stabilize and fix the water flow, further ensuring the stability of the constructed wetland, thereby efficiently removing pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the following is a brief introduction to the drawings required for describing the embodiment: Figure 1 A schematic diagram of the reed-biochar vertical subsurface flow constructed wetland provided in Example 1; Figure 2 The removal rate and post-treatment concentration diagram of COD pollutants at different stages provided in Example 2; Figure 3 NH4 provided in Example 2 + -N pollutant removal rate and post-treatment concentration diagram at different stages; Figure 4 NO3 provided in Example 2 - -N pollutant removal rate and post-treatment concentration diagram at different stages; Figure 5 The removal rate and post-treatment concentration of TN pollutants at different stages provided in Example 2; Figure 6 The removal rate and post-treatment concentration diagram of TP pollutants at different stages provided in Example 2.

[0017] Description of reference numerals: 1. Bare soil layer, 2. Waterproof geotextile, 3. Air stone layer, 4. Large-grained gravel layer, 5. Medium-grained gravel layer, 6. Small gravel-biochar mixed layer, 7. Coarse river sand layer, 8. Water layer, 9. Reed. DETAILED DESCRIPTION

[0018] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described below in conjunction with embodiments and drawings.

[0019] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways than those described herein. Therefore, the present invention is not limited to the specific embodiments of the following disclosure.

[0020] Example 1 A reed-biochar vertical subsurface flow artificial wetland system comprises an artificial wetland and an aeration device.

[0021] like Figure 1 As shown, the artificial wetland is composed of, from bottom to top, a plain soil layer 1, a waterproof geotextile 2, an air stone layer 3, a large-grained gravel layer 4, a medium-grained gravel layer 5, a small-grained gravel-biochar mixed layer 6, a coarse river sand layer 7 and a water layer 8; reeds 9 are planted in the coarse river sand layer 7.

[0022] Reed 9 absorbs nutrients from the water through its roots and provides a stable attachment environment for microorganisms, participating in the water purification process. Its roots release oxygen, which helps to oxidize organic matter in the water and improve the treatment capacity of the wetland. Reed 9 has good adaptability and purification ability. Its well-developed root system can effectively absorb nutrients from the water, especially pollutants such as nitrogen and phosphorus, and plays a significant role in environmental purification.

[0023] The compaction coefficient of the plain soil layer 1 is ≥0.95; the thickness of the waterproof geotextile 2 is 2mm; the thickness of the air stone layer 3 is 10mm.

[0024] The soil layer 1 is mainly used to support and fix the entire artificial wetland system, and plays a role in preventing water leakage. At the same time, it provides a basic structure to ensure the stability of the wetland. The compacted soil layer 1 has a high compaction coefficient, which can effectively prevent water leakage and ensure the stable operation of the wetland system. The waterproof geotextile 2 prevents further water leakage, protects the bottom structure of the wetland system, and prevents the wetland structure from being eroded by water. While maintaining the stability of the wetland system, the waterproof geotextile 2 prevents pollutants from infiltrating into the soil layer.

[0025] The air stone layer 3 is mainly used for aeration. It is connected to an external aeration pump to provide oxygen to the wetland system, promoting aerobic decomposition and treatment of organic matter in the wastewater. The air stone layer 3 helps to increase the dissolved oxygen content in the wetland system and improve the removal efficiency of pollutants in the wastewater, especially during intermittent aeration, effectively supporting the formation of an alternating aerobic and anaerobic environment.

[0026] The thickness of the large-particle crushed stone layer 4 is 100 m, and the particle size of the large-particle crushed stone ranges from 40 mm to 70 mm.

[0027] The thickness of the medium-grained gravel layer 5 is 250 mm, and the particle size of the medium-grained gravel ranges from 20 mm to 40 mm.

[0028] The large-grained gravel layer 4 provides filtering and supporting functions for the water body, effectively preventing larger solid particles and suspended matter from entering the lower structure, providing a good physical filtering environment, and the pores between the particles are conducive to the flow of water and promote the initial decomposition of organic pollutants. The medium-grained gravel layer 5 serves as a further filtering medium and also plays a role in enhancing the uniform distribution of water flow, supporting the stability and uniformity of water flow in the wetland. While increasing the physical stability of the wetland system, the medium-grained gravel layer 5 provides a good growth environment for microbial attachment, which helps further degradation of pollutants.

[0029] The thickness of the small gravel-biochar mixed layer 6 is 150 mm. The small gravel and biochar are mixed in a volume ratio of 1:1, and the particle size range of the small gravel is 5 mm to 20 mm.

[0030] The small gravel biochar mixed layer 6 is the key purification layer of the wetland system, combining the physical filtration of gravel and the adsorption capacity of biochar. Biochar has a strong adsorption capacity and can effectively remove organic matter and some difficult-to-degrade pollutants in the water, while providing an ideal surface for microorganisms to attach. Through the 1:1 mixture of small gravel and biochar, a good physical filtration effect is maintained, greatly improving the efficiency of pollutant removal.

[0031] The thickness of the coarse river sand layer 7 is 150 mm, and the particle size of the coarse river sand is less than 5 mm; the water depth in the water body layer 8 is less than 700 mm.

[0032] The coarse river sand layer 7 plays a role in stabilizing and fixing the water flow in the wetland system, while supporting the growth of plants. It can further filter the suspended matter in the water body to ensure that the water quality entering the water body layer 8 is relatively clean. The coarse river sand has a particle size of less than 5mm, has good filtering and supporting effects, and provides a stable growth environment for the roots of reeds 9.

[0033] The water layer 8 provides water for the growth of reeds 9 and forms a moist ecological environment in the entire wetland system, ensuring the smooth flow of water in the wetland system and promoting the transfer of oxygen and the decomposition of pollutants. The water depth of the water layer 8 is less than 700 mm, ensuring that the wetland system can store enough wastewater for treatment without causing excessive water accumulation to affect the function of plants and microorganisms.

[0034] The aeration device comprises a rubber hose sheathed with a PVC tube and an aeration pump. The rubber hose sheathed with the PVC tube is connected to the aeration pump, and one end of the rubber hose sheathed with the PVC tube away from the aeration pump is connected to the air stone layer 3.

[0035] The diameter of the PVC pipe is 20mm and the diameter of the rubber hose is 10mm.

[0036] A method for operating a reed-biochar vertical subsurface flow constructed wetland system, using the reed-biochar vertical subsurface flow constructed wetland system to treat wastewater, and treating specific water pollutants including 400 mg / L COD, 80 mg / L NH4 + -N, 5mg / L NO3 - -N, 85 mg / L TN and 8 mg / L TP.

[0037] COD is chemical oxygen demand, which reflects the content of organic matter in water. COD is an important indicator for evaluating the degree of water pollution. +-N stands for ammonia nitrogen, which indicates the concentration of ammonia nitrogen in water. High concentrations of ammonia nitrogen are toxic to aquatic organisms, so they need to be effectively removed. - -N stands for nitrate nitrogen, which indicates the nitrate content in the water. Excessive nitrate will lead to eutrophication of the water body. TN stands for total nitrogen, which refers to all forms of nitrogen in the water, including ammonia nitrogen, nitrate nitrogen and organic nitrogen. Monitoring total nitrogen helps to assess the overall water quality. TP stands for total phosphorus, which refers to all forms of phosphorus in the water. Excessive phosphorus will promote eutrophication of the water body and lead to the proliferation of algae.

[0038] The operation method adopts intermittent aeration; the total daily aeration time is 6 hours, and the specific times are: 3-4 o'clock, 7-8 o'clock, 11-12 o'clock, 15-16 o'clock, 19-20 o'clock and 23-24 o'clock every day; the aeration flow rate is 0.05L / min; the operation time is from May to July every year.

[0039] Example 2 A comparative experiment was conducted using the operating method of the reed-biochar vertical subsurface flow artificial wetland system of Example 1.

[0040] In group 1 (CW1), the aeration condition was 0.05 L / min, 2 h / d in the first stage, and the aeration volume was increased in the second stage, while the aeration duration remained unchanged at 0.15 L / min, 2 h / d.

[0041] In group 2 (CW2), the aeration conditions were 0.05 L / min, 4 h / d in the first stage, and the aeration duration was increased in the second stage, with the aeration volume remaining unchanged, and the conditions were 0.05 L / min, 6 h / d.

[0042] In group three (CW3), the aeration condition was 0.1 L / min, 4 h / d in the first stage, and the aeration duration was increased in the second stage, with the aeration volume remaining unchanged, and the condition was 0.1 L / min, 6 h / d.

[0043] In group 4 (CW4), the aeration conditions in the first stage were 0.1 L / min, 2 h / d, and the aeration volume was increased in the second stage, while the aeration duration remained unchanged at 0.2 L / min, 2 h / d.

[0044] The specific operating conditions of each group are shown in Table 1. According to the set operating conditions, the concentration of each pollutant is tested every 3 days.

[0045] Table 1 Specific operation status of each group Comparing the pollutant effluent concentrations between the groups, the results are as follows Figure 2-Figure 6 The removal rates of pollutants at each stage are shown in Table 2.

[0046] Table 2 Removal rate of pollutants at each stage Note: Different lowercase letters in the column indicate significant differences among treatments (P < 0.05).

[0047] Depend on Figure 2-6 As shown in Table 1 and Table 2, the intermittent aeration condition of 0.05L / min and 6h / d has a significant effect on the chemical oxygen demand (COD), ammonia nitrogen (NH4 + -N), total nitrogen (TN), total phosphorus (TP) and nitrate nitrogen (NO3 - -N) removal rates reached 95.6%, 87.5%, 84.5%, 87.6% and 70.5% respectively. It can be seen that when the intermittent aeration condition is 6h / d (6h evenly distributed throughout the day) and the aeration flow rate is 0.05L / min, the removal of chemical oxygen demand (COD), ammonia nitrogen (NH4 + -N), total nitrogen (TN), total phosphorus (TP) and nitrate nitrogen (NO3 - -N) removal rates reached 95.6%, 87.5%, 84.5%, 87.6% and 70.5% respectively.

[0048] Therefore, the intermittent aeration operation mode is set to 6h / d, and the aeration flow rate is 0.05L / min. The specific time is 3-4, 7-8, 11-12, 15-16, 19-20 and 23-24 every day. The operation time is concentrated in May-July every year. Aeration operations are performed at several fixed time periods every day, which helps to maintain a good oxygen supply in the wetland system, promote the alternation of aerobic and anaerobic conditions, and thus improve the efficiency and stability of wastewater treatment. It can effectively support the microbial community in the wetland and help it more effectively decompose and remove organic pollutants and nutrients such as nitrogen and phosphorus in the water.

[0049] The temperature is high between May and July each year, which is conducive to the activity and growth of microorganisms in the wetland, thereby enhancing the efficiency of wastewater treatment. The appropriate temperature helps promote the biodegradation process and accelerate the decomposition rate of organic matter. Moreover, this period is the peak season for plant growth. Wetland plants such as reeds can grow rapidly, and their roots can better absorb nutrients and organic matter, which is conducive to water purification.

[0050] Generally speaking, the concentration of organic pollutants and nutrients in water bodies is higher in spring and summer, so choosing to perform aeration operations during this period can more effectively cope with the treatment needs of high-concentration pollutants. Avoiding the low temperature period in winter can achieve better treatment results.

[0051] The above description is only a preferred embodiment of the present invention and does not limit the present invention in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes for application in other fields. However, any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A reed-biochar vertical subsurface flow artificial wetland system, characterized in that: Includes constructed wetlands and aeration devices; The artificial wetland is composed of a plain soil layer, a waterproof geotextile, an air stone layer, a large-grained gravel layer, a medium-grained gravel layer, a small-grained gravel-biochar mixed layer, a coarse river sand layer and a water layer from bottom to top; reeds are planted in the coarse river sand layer.

2. The reed-biochar vertical subsurface flow artificial wetland system according to claim 1, characterized in that: The compaction coefficient of the bare soil layer is ≥0.95; the thickness of the waterproof geotextile is 2 mm; and the thickness of the air stone layer is 10 mm.

3. The reed-biochar vertical subsurface flow artificial wetland system according to claim 1, characterized in that: The thickness of the large-particle crushed stone layer is 100m, and the particle size range of the large-particle crushed stone is 40mm to 70mm.

4. The reed-biochar vertical subsurface flow artificial wetland system according to claim 1, characterized in that: The thickness of the medium-grained gravel layer is 250 mm, and the particle size range of the medium-grained gravel is 20 mm to 40 mm.

5. The reed-biochar vertical subsurface flow artificial wetland system according to claim 1, characterized in that: The thickness of the small gravel-biochar mixed layer is 150 mm, the small gravel and biochar are mixed in a volume ratio of 1:1, and the particle size range of the small gravel is 5 mm to 20 mm.

6. The reed-biochar vertical subsurface flow artificial wetland system according to claim 1, characterized in that: The thickness of the coarse river sand layer is 150 mm, and the particle size of the coarse river sand is less than 5 mm; the water depth in the water body layer is less than 700 mm.

7. The reed-biochar vertical subsurface flow artificial wetland system according to claim 1, characterized in that: The aeration device comprises a rubber hose sheathed with a PVC tube and an aeration pump. The rubber hose sheathed with the PVC tube is connected to the aeration pump, and one end of the rubber hose sheathed with the PVC tube away from the aeration pump is connected to the air stone layer.

8. The reed-biochar vertical subsurface flow artificial wetland system according to claim 7, characterized in that: The diameter of the PVC tube is 20 mm, and the diameter of the rubber hose is 10 mm.

9. An operating method of a reed-biochar vertical subsurface flow artificial wetland system, characterized in that: The reed-biochar vertical subsurface flow artificial wetland system described in claims 1-8 is used for wastewater treatment, and the specific water pollutants treated include 400 mg / L COD, 80 mg / L NH4 + -N, 5mg / L NO3 - -N, 85 mg / L TN and 8 mg / L TP.

10. The operation method of the reed-biochar vertical subsurface flow artificial wetland system according to claim 9, characterized in that: Intermittent aeration is adopted; the total daily aeration time is 6 hours, and the specific times are: 3-4 o'clock, 7-8 o'clock, 11-12 o'clock, 15-16 o'clock, 19-20 o'clock and 23-24 o'clock every day; the aeration flow rate is 0.05L / min; the operation time is from May to July every year.

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