A method for strengthening nitrogen and phosphorus removal performance of artificial wetland based on sulfide alleviation

Abstract

The present application relates to the technical field of wastewater treatment, and particularly relates to a method for strengthening nitrogen and phosphorus removal performance of artificial wetland by alleviating clogging based on sulfide. The method adds sulfide to wastewater before the wastewater enters an artificial wetland treatment unit, and controls the concentration of the sulfide in the water entering the artificial wetland treatment unit. The artificial wetland treatment unit adopts an intermittent aeration operation mode, and the intermittent aeration operation mode includes a non-aeration stage and an aeration stage which are alternately operated. By adding sulfide to the influent and coupling the intermittent aeration operation mode, the network structure of extracellular polymeric substances is destroyed by the sulfide, and the hydrolysis and fermentation thereof is promoted in the non-aeration stage, so that the clogging is effectively delayed. Through the synergistic effect of sulfide-mediated short-cut nitrification, sulfur autotrophic denitrification and denitrifying phosphorus removal, efficient nitrogen and phosphorus removal is realized under the condition of low carbon-nitrogen ratio, the dependence on additional carbon source is reduced, the operation cycle of the wetland is prolonged, and the method is suitable for rural sewage and low carbon-nitrogen ratio wastewater treatment.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a method for enhancing nitrogen and phosphorus removal performance by alleviating blockage in constructed wetlands using sulfides. Background Technology

[0002] Constructed wetlands, as an ecological wastewater treatment technology, are increasingly widely used in decentralized wastewater treatment (such as aquaculture wastewater, rural domestic sewage, and small town sewage) due to their advantages of simple operation and maintenance, low energy consumption, and good landscape harmony. Their purification mechanism relies on the synergistic effect of packing materials, plants, and attached biofilms to remove pollutants through physical interception, chemical precipitation, and microbial metabolism. However, with prolonged operation, constructed wetlands generally face a bottleneck problem that restricts their long-term stable operation—biological blockage.

[0003] The causes of bioclogging are complex, but the core mechanism lies in the rapid proliferation of microorganisms attached to the surface of the packing material under nutrient-rich conditions, resulting in the secretion of large amounts of extracellular polymeric substances (EPS). EPS is mainly composed of macromolecular organic matter such as polysaccharides, proteins, and humic substances, and its network structure can bridge metal cations in the water (such as Ca). 2+ Mg 2+ Suspended particles and inorganic sediments gradually form a dense biofilm and organic-inorganic composite sediment layer on the surface and pores of the packing particles. This process leads to a significant decrease in the effective porosity of the packing material, a reduction in the hydraulic conductivity, and an exacerbation of short-circuiting or stagnant flow phenomena. Ultimately, this manifests as a decrease in the system's treated water volume, a shortened operating cycle, and in severe cases, even complete wetland failure. Numerous engineering practices have shown that bioclogging has become the primary factor limiting the long-term stable operation of constructed wetlands. The resulting high costs of packing material replacement or system reconstruction weaken the economic viability of this technology.

[0004] To address the clogging problem, current engineering practices primarily employ two strategies. The first is physical backwashing, which involves flushing the packing layer with reverse water or airflow to remove excessively thick biofilm and unclog pores. For example, patents CN223458186U and CN223316522U disclose related backwashing devices or methods. However, backwashing often only temporarily restores some hydraulic performance, and the high-intensity hydraulic shearing simultaneously washes away active functional microorganisms, leading to a significant decrease in nitrification, denitrification, and phosphorus removal capabilities after flushing, resulting in a long system recovery period. The second strategy is packing replacement. While this method can completely resolve clogging, it involves a large amount of construction work, requires system shutdown, and the new packing lacks a mature biofilm, making it difficult to guarantee effluent quality during re-establishment. In addition, some researchers have attempted to add chemical agents (such as surfactants or oxidants) to decompose EPS, but such measures are prone to introducing secondary pollution and cause non-selective inhibition of the microbial community, limiting their application prospects.

[0005] Besides clogging issues, constructed wetlands also commonly face the challenge of insufficient nitrogen and phosphorus removal efficiency under low C / N ratios. Many decentralized wastewater treatments (such as aquaculture effluent) are relatively lacking in organic carbon sources, while traditional biological nitrogen removal relies on heterotrophic denitrification, requiring sufficient readily biodegradable organic matter as electron donors. The shortage of carbon sources directly limits the removal efficiency of total nitrogen. To compensate for the lack of carbon sources, commercial carbon sources such as glucose and sodium acetate are often added during operation. This not only increases operating costs but may also lead to excessive proliferation of heterotrophic bacteria, exacerbating the risk of biological clogging. Therefore, a vicious cycle exists between increased clogging and insufficient carbon sources, becoming a deep-seated contradiction restricting the widespread adoption of constructed wetland technology.

[0006] In summary, existing methods for alleviating clogging either treat the symptoms but not the root cause, or negatively impact nitrogen and phosphorus removal performance, failing to simultaneously maintain hydraulic performance and enhance purification capabilities. Therefore, there is an urgent need to develop a novel constructed wetland operation strategy. This strategy should be able to regulate biofilm structure at the source to delay clogging, while simultaneously enhancing nitrogen and phosphorus removal under low-carbon conditions, without relying on complex external equipment. This would provide a practical and feasible technical solution for the long-term, low-consumption operation of constructed wetlands. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a method for alleviating clogging in constructed wetlands and enhancing nitrogen and phosphorus removal performance based on sulfides.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A method for alleviating blockage and enhancing nitrogen and phosphorus removal performance of constructed wetlands based on sulfides involves adding sulfides to the wastewater before it enters the constructed wetland treatment unit to control the influent sulfide concentration entering the unit. The constructed wetland treatment unit adopts an intermittent aeration operation mode, which includes alternating non-aeration and aeration phases.

[0009] Specifically, by alternating between anaerobic and aerobic environments, the blockage of the packing layer is alleviated and nitrogen and phosphorus in wastewater are removed in a coordinated manner.

[0010] Based on the above technical solutions, preferably, the sulfide is generated by the anaerobic reduction reaction of sulfate contained in the wastewater itself or by external addition.

[0011] Specifically, the sulfides interact with the polysaccharide components and calcium and magnesium bridging cations in the extracellular polymeric material, thereby weakening the stability of the extracellular polymeric network structure, reducing the densification of the biofilm, forming a loose and porous structure, increasing the porosity of the filler layer, and delaying the clogging of the constructed wetland.

[0012] Furthermore, the sulfide is used to promote the hydrolysis of extracellular polymers and the release of soluble microbial metabolites, and to promote the in-situ fermentation of complex organic matter by fermenting bacteria to generate volatile fatty acids, providing a supplementary carbon source for denitrification and biological phosphorus removal processes.

[0013] In this invention, the sulfide is used to selectively inhibit the activity of nitrite-oxidizing bacteria, promote short-cut nitrification, achieve nitrite nitrogen accumulation, reduce the carbon source requirement for denitrification, and improve nitrogen removal efficiency. The sulfide acts as an electron donor to drive the sulfur autotrophic denitrification process, promoting sulfur-oxidizing bacteria to utilize sulfides and intracellular sulfur-containing substances to complete denitrification. The sulfur-oxidizing bacteria have the ability to accumulate phosphorus through denitrification and can absorb phosphates in water under anoxic and aerobic environments to achieve phosphorus removal.

[0014] Specifically, during the oxidation of sulfides, sulfur-oxidizing bacteria generate and accumulate various sulfur-containing intermediates within their cells, including elemental sulfur, polysulfides, and thiosulfates. These intracellular sulfur-containing substances can serve as electron donors and are re-oxidized under anaerobic conditions to provide electrons for the denitrification process.

[0015] Based on the above technical solutions, preferably, the constructed wetland treatment unit is a vertical flow constructed wetland, a combined flow constructed wetland, or a multi-stage A / O constructed wetland.

[0016] Based on the above technical solutions, preferably, the influent sulfide concentration of the constructed wetland treatment unit is 10-80 mg S / L.

[0017] Based on the above technical solutions, preferably, the time ratio of the non-aeration stage to the aeration stage is 3:1.

[0018] Based on the above technical solutions, preferably, the non-aeration stage runs for 90 minutes and the aeration stage runs for 30 minutes.

[0019] Specifically, the non-aeration stage is used to promote the hydrolysis and fermentation of extracellular polymers, while the aeration stage is used to promote short-cut nitrification, autotrophic denitrification, and denitrification for phosphorus removal.

[0020] Based on the above technical solutions, preferably, the dissolved oxygen concentration in the aeration stage is 3 mg / L.

[0021] Based on the above technical solutions, preferably, the vertical flow constructed wetland includes, from bottom to top, a water distribution layer, a support layer, a filler layer and a surface water distribution layer.

[0022] Based on the above technical solutions, preferably, the functional microbial community enriched during the operation of the intermittent aeration mode includes sulfur autotrophic denitrifying bacteria and extracellular polymeric fermentation and degradation bacteria.

[0023] Based on the above technical solutions, preferably, the sulfur autotrophic denitrifying bacteria are selected from at least one of Thiobacillus and Thiothrix, and the extracellular polymeric fermentation and degradation bacteria are Propionivibrio.

[0024] Specifically, Thiobacillus and Thiothrix are both typical sulfur-autotrophic denitrifying bacteria, capable of using sulfides or intracellular sulfur-containing substances as electron donors for denitrification. They share essentially the same metabolic pathways and functional effects in this respect. Propionivibrio is a typical extracellular polymeric substance (EPS) fermentation and degradation bacterium, capable of participating in the hydrolysis and fermentation of EPS and generating volatile fatty acids, providing a supplementary carbon source for denitrification and biological phosphorus removal processes. In addition, Defluviicoccus can be enriched during system operation. This bacterium participates in part of the denitrification process, which helps to provide nitrite substrates for subsequent autotrophic denitrification.

[0025] Compared with the prior art, the present invention has the following beneficial effects: (1) By adding sulfide to the influent and coupling it with the intermittent aeration mode, the sulfide interacts with the polysaccharide components and bridging cations such as calcium and magnesium in the extracellular polymer to weaken the stability of the extracellular polymer network structure. At the same time, the non-aeration stage promotes the hydrolysis and fermentation degradation of the extracellular polymer, effectively reducing the densification of the biofilm and significantly slowing down the rate of porosity decay of the packing layer, thus delaying the biological blockage process from the source.

[0026] (2) Through multiple mechanisms mediated by sulfides, short-cut nitrification, sulfur autotrophic denitrification and denitrification phosphorus removal are synergistically enhanced, and high nitrogen and phosphorus removal efficiency is maintained even under low carbon-to-nitrogen ratio conditions. In the non-aeration stage, extracellular polymers are promoted to generate volatile fatty acids through in-situ fermentation. Sulfides act as inorganic electron donors to drive autotrophic denitrification. The dual pathways synergistically reduce the amount of traditional organic carbon source added, effectively reducing operating costs.

[0027] (3) By using sulfides to alleviate biological blockage inside the wetland, combined with the pretreatment function of the anaerobic reactor, some suspended solids and organic loads can be removed in advance, providing double protection to extend the operation cycle of the constructed wetland. At the same time, this invention does not require complex external equipment and can be easily coupled with the existing anaerobic reactor-constructed wetland combination process. It is applicable to the treatment of rural sewage, decentralized domestic sewage and low carbon-nitrogen ratio wastewater, and has good prospects for engineering promotion and application. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1 This embodiment constructs an anaerobic reactor-constructed wetland coupled treatment system, through which the anaerobic reactor generates sufficient sulfides to alleviate blockage in the constructed wetland.

[0030] (1) System Construction Construct a combined treatment system consisting of anaerobic reaction units and vertical flow constructed wetlands.

[0031] The anaerobic reaction unit adopts an upflow anaerobic sludge blanket reactor (UASB) with an effective volume of 20L and a hydraulic retention time (HRT) of 12h.

[0032] The constructed wetland utilizes a vertical flow reactor column made of plexiglass, 80 cm high, with an inner diameter of 15 cm and a total effective volume of 12 L. From bottom to top, the constructed wetland comprises: a water distribution layer, a support layer, a filler layer, and a surface distribution layer. The support layer is filled with gravel with an average particle size of 9 mm and a height of 10 cm; the filler layer is filled with quartz sand with an average particle size of 4 mm and a height of 50 cm; and the surface layer is planted with cattails (Typha orientalis). The constructed wetland is equipped with a bottom aeration device and operates using an intermittent aeration mode.

[0033] (2) Vaccination and initiation Anaerobic sludge was inoculated into the UASB, and the sludge concentration was controlled at 12 g VSS / L. The system was started up using artificial water distribution, and the main components of the influent were as follows: glucose (120 mg COD / L), ammonium chloride (40 mg N / L), potassium dihydrogen phosphate (6 mg P / L), and sodium sulfate (80 mg S / L).

[0034] After the system ran continuously for 30 days, the COD and NH4 in the influent and effluent were... + -N removal rate fluctuated less than 5% for 7 consecutive days, and a stable biofilm was formed in the constructed wetland.

[0035] (3) System operation During the anaerobic reaction, sulfate in the wastewater is converted into sulfides by sulfate-reducing bacteria. The sulfide-containing effluent from the UASB enters the constructed wetland treatment unit. During operation, the sulfide concentration in the constructed wetland influent is periodically monitored and regulated by supplementing with sodium sulfide solution to ensure the influent sulfide concentration is maintained at 40 mg S / L. The constructed wetland operates in an intermittent aeration mode: a 90-minute non-aeration phase followed by a 30-minute aeration phase, in a continuous cycle. During the aeration phase, the aeration intensity is controlled by a gas flow meter and an online dissolved oxygen monitor, maintaining the dissolved oxygen concentration at 3 mg / L. The total hydraulic retention time of the system is 24 hours.

[0036] (4) Results of the operation Measurements showed that the porosity of the packing layer was 42.5% at the beginning of operation, and decreased to 34.1% after 90 days of continuous operation, with a porosity decrease rate of 0.093% / day. During the operation, the cattails grew well, without obvious yellowing or wilting; the average removal rate of total nitrogen was 78.19%, and the average removal rate of total phosphorus was 84.23%.

[0037] After 90 days of operation, high-throughput sequencing analysis of the microbial community attached to the biofilm in the constructed wetland filler layer was performed. The results showed that under the selective pressure of sulfide addition and intermittent aeration, the system naturally enriched sulfur autotrophic denitrifying bacteria, mainly Thiobacillus (relative abundance 12.47%) and Thiotris (relative abundance 5.32%), as well as extracellular polymeric fermentation and degradation bacteria, mainly Propionivibrio (relative abundance 3.18%).

[0038] Example 2 This embodiment constructs an anaerobic reactor-constructed wetland coupled treatment system, through which the anaerobic reactor generates sufficient sulfides to alleviate blockage in the constructed wetland.

[0039] (1) System Construction Construct a combined treatment system consisting of anaerobic reaction units and vertical flow constructed wetlands.

[0040] The anaerobic reaction unit adopts an upflow anaerobic sludge blanket reactor (UASB) with an effective volume of 20L and a hydraulic retention time (HRT) of 12h.

[0041] The constructed wetland utilizes a vertical flow reactor column made of plexiglass, 80 cm high, with an inner diameter of 15 cm and a total effective volume of 12 L. From bottom to top, the constructed wetland comprises: a water distribution layer, a support layer, a filler layer, and a surface distribution layer. The support layer is filled with gravel with an average particle size of 9 mm and a height of 10 cm; the filler layer is filled with quartz sand with an average particle size of 4 mm and a height of 50 cm; and the surface layer is planted with cattails (Typha orientalis). The constructed wetland is equipped with a bottom aeration device and operates using an intermittent aeration mode.

[0042] (2) Vaccination and initiation Anaerobic sludge was inoculated into the UASB, and the sludge concentration was controlled at 12 g VSS / L. The system was started up using artificial water distribution, and the main components of the influent were as follows: glucose (120 mg COD / L), ammonium chloride (40 mg N / L), potassium dihydrogen phosphate (6 mg P / L), and sodium sulfate (20 mg S / L).

[0043] After the system ran continuously for 30 days, the COD and NH4 in the influent and effluent were... + -N removal rate fluctuated less than 5% for 7 consecutive days, and a stable biofilm was formed in the constructed wetland.

[0044] (3) System operation During the anaerobic reaction, sulfate in the wastewater is converted into sulfides by sulfate-reducing bacteria. The sulfide-containing effluent from the UASB enters the constructed wetland treatment unit. During operation, the sulfide concentration in the constructed wetland influent is periodically monitored and regulated by supplementing with sodium sulfide solution to ensure the influent sulfide concentration is maintained at 10 mg S / L. The constructed wetland operates in an intermittent aeration mode: a 90-minute non-aeration phase followed by a 30-minute aeration phase, in a continuous cycle. During the aeration phase, the aeration intensity is controlled by a gas flow meter and an online dissolved oxygen monitor, maintaining the dissolved oxygen concentration at 3 mg / L. The total hydraulic retention time of the system is 24 hours.

[0045] (4) Results of the operation Measurements showed that the porosity of the packing layer was 42.5% at the beginning of operation, and decreased to 33.7% after 90 days of continuous operation, with a porosity decrease rate of 0.098% / day. During the operation, the cattails grew well, without any obvious yellowing or wilting; the average removal rate of total nitrogen was 77.38%, and the average removal rate of total phosphorus was 79.56%.

[0046] After 90 days of operation, high-throughput sequencing analysis of the microbial community attached to the biofilm in the constructed wetland packing layer was performed. The results showed that under the selective pressure of sulfide addition and intermittent aeration, the system naturally enriched sulfur autotrophic denitrifying bacteria, mainly Thiobacillus (relative abundance 8.93%) and Thiotris (relative abundance 3.67%), as well as extracellular polymeric fermentation and degradation bacteria, mainly Propionivibrio (relative abundance 2.41%).

[0047] Example 3 This embodiment constructs an anaerobic reactor-constructed wetland coupled treatment system, through which the anaerobic reactor generates sufficient sulfides to alleviate blockage in the constructed wetland.

[0048] (1) System Construction Construct a combined treatment system consisting of anaerobic reaction units and vertical flow constructed wetlands.

[0049] The anaerobic reaction unit adopts an upflow anaerobic sludge blanket reactor (UASB) with an effective volume of 20L and a hydraulic retention time (HRT) of 12h.

[0050] The constructed wetland utilizes a vertical flow reactor column made of plexiglass, 80 cm high, with an inner diameter of 15 cm and a total effective volume of 12 L. From bottom to top, the constructed wetland comprises: a water distribution layer, a support layer, a filler layer, and a surface distribution layer. The support layer is filled with gravel with an average particle size of 9 mm and a height of 10 cm; the filler layer is filled with quartz sand with an average particle size of 4 mm and a height of 50 cm; and the surface layer is planted with cattails (Typha orientalis). The constructed wetland is equipped with a bottom aeration device and operates using an intermittent aeration mode.

[0051] (2) Vaccination and initiation Anaerobic sludge was inoculated into the UASB, and the sludge concentration was controlled at 12 g VSS / L. The system was started up using artificial water distribution, and the main components of the influent were as follows: glucose (120 mg COD / L), ammonium chloride (40 mg N / L), potassium dihydrogen phosphate (6 mg P / L), and sodium sulfate (160 mg S / L).

[0052] After the system ran continuously for 30 days, the COD and NH4 in the influent and effluent were... + -N removal rate fluctuated less than 5% for 7 consecutive days, and a stable biofilm was formed in the constructed wetland.

[0053] (3) System operation During the anaerobic reaction, sulfate in the wastewater is converted into sulfides by sulfate-reducing bacteria. The sulfide-containing effluent from the UASB enters the constructed wetland treatment unit. During operation, the sulfide concentration in the constructed wetland influent is periodically monitored and regulated by supplementing with sodium sulfide solution to ensure the influent sulfide concentration is maintained at 80 mg S / L. The constructed wetland operates in an intermittent aeration mode: a 90-minute non-aeration phase followed by a 30-minute aeration phase, in a continuous cycle. During the aeration phase, the aeration intensity is controlled by a gas flow meter and an online dissolved oxygen monitor, maintaining the dissolved oxygen concentration at 3 mg / L. The total hydraulic retention time of the system is 24 hours.

[0054] (4) Results of the operation Measurements showed that the porosity of the packing layer was 42.5% at the beginning of operation, and decreased to 35.0% after 90 days of continuous operation, with a porosity decrease rate of 0.083% / day. During the operation, the cattails grew well, without obvious yellowing or wilting; the average removal rate of total nitrogen was 81.05%, and the average removal rate of total phosphorus was 86.94%.

[0055] After 90 days of operation, high-throughput sequencing analysis of the microbial community attached to the biofilm in the constructed wetland packing layer was performed. The results showed that under the selective pressure of sulfide addition and intermittent aeration, the system naturally enriched sulfur autotrophic denitrifying bacteria, mainly Thiobacillus (relative abundance 10.86%) and Thiotris (relative abundance 4.53%), as well as extracellular polymeric fermentation and degradation bacteria, mainly Propionivibrio (relative abundance 2.89%).

[0056] Comparative Example 1 The only difference between this comparative example and Example 1 is that no sulfides were added to the influent of the constructed wetland in Comparative Example 1, and the concentration of sulfides in the influent of the constructed wetland was <0.5 mg S / L.

[0057] (1) System Construction Construct a combined treatment system consisting of anaerobic reaction units and vertical flow constructed wetlands.

[0058] The anaerobic reaction unit adopts an upflow anaerobic sludge blanket reactor (UASB) with an effective volume of 20L and a hydraulic retention time (HRT) of 12h.

[0059] The constructed wetland utilizes a vertical flow reactor column made of plexiglass, 80 cm high, with an inner diameter of 15 cm and a total effective volume of 12 L. From bottom to top, the constructed wetland comprises: a water distribution layer, a support layer, a filler layer, and a surface distribution layer. The support layer is filled with gravel with an average particle size of 9 mm and a height of 10 cm; the filler layer is filled with quartz sand with an average particle size of 4 mm and a height of 50 cm; and the surface layer is planted with cattails (Typha orientalis). The constructed wetland is equipped with a bottom aeration device and operates using an intermittent aeration mode.

[0060] (2) Vaccination and initiation Anaerobic sludge was inoculated into the UASB, and the sludge concentration was controlled at 12 g VSS / L. The system was started up using artificial water distribution, and the main components of the influent were as follows: glucose (120 mg COD / L), ammonium chloride (40 mg N / L), potassium dihydrogen phosphate (6 mg P / L), and sodium sulfate (80 mg S / L).

[0061] After the system ran continuously for 30 days, the COD and NH4 in the influent and effluent were... + -N removal rate fluctuated less than 5% for 7 consecutive days, and a stable biofilm was formed in the constructed wetland.

[0062] (3) System operation During the anaerobic reaction, sulfate in the wastewater is converted into sulfides by sulfate-reducing bacteria. The sulfide-containing effluent from the UASB enters the constructed wetland treatment unit. During operation, no sulfides are added to the wastewater. Due to the system's influent COD / S ratio of 1.5, the available organic carbon source for sulfate-reducing bacteria is severely insufficient, inhibiting the sulfate reduction reaction. The sulfide concentration in the constructed wetland influent is measured to be <0.5 mg S / L. The constructed wetland operates in an intermittent aeration mode: a 90-minute non-aeration phase followed by a 30-minute aeration phase, circulating continuously. During the aeration phase, the aeration intensity is controlled via a gas flow meter and an online dissolved oxygen monitor, maintaining the dissolved oxygen concentration at 3 mg / L. The total hydraulic retention time of the system is 24 hours.

[0063] (4) Results of the operation Measurements showed that the porosity of the packing layer was 42.5% at the initial stage of operation, decreasing to 32.0% after 90 days of continuous operation, with a porosity decrease rate of 0.117% / day. During operation, the average removal rate of total nitrogen was 55.6%, and the average removal rate of total phosphorus was 60.1%.

[0064] After 90 days of operation, high-throughput sequencing analysis of the microbial community attached to the biofilm in the constructed wetland filler layer was performed. The results showed that sulfur autotrophic denitrifying bacteria such as Thiobacillus and Thiotris, as well as extracellular polymeric fermentation and degradation bacteria such as Propionivibrio, did not become the dominant bacterial groups in the system.

[0065] A comparison of the operating results of Example 1 and Comparative Example 1 shows that the present invention can effectively delay the clogging of constructed wetlands and enhance nitrogen and phosphorus removal performance.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for alleviating clogging and enhancing nitrogen and phosphorus removal performance in constructed wetlands based on sulfides, characterized in that, Sulfides are added to the wastewater before it enters the constructed wetland treatment unit to control the concentration of sulfides in the influent. The constructed wetland treatment unit adopts an intermittent aeration operation mode, which includes alternating non-aeration and aeration phases.

2. The method for alleviating clogging and enhancing nitrogen and phosphorus removal performance of constructed wetlands based on sulfides according to claim 1, characterized in that, The sulfides are generated from the sulfates contained in the wastewater through anaerobic reduction reactions or by external addition.

3. The method for alleviating clogging and enhancing nitrogen and phosphorus removal performance of constructed wetlands based on sulfides according to claim 1, characterized in that, The constructed wetland treatment unit is a vertical flow constructed wetland, a combined flow constructed wetland, or a multi-stage A / O constructed wetland.

4. The method for alleviating clogging and enhancing nitrogen and phosphorus removal performance of constructed wetlands based on sulfides according to claim 1, characterized in that, The influent sulfide concentration of the constructed wetland treatment unit is 10-80 mg S / L.

5. The method for alleviating clogging and enhancing nitrogen and phosphorus removal performance of constructed wetlands based on sulfides according to claim 1, characterized in that, The ratio of the duration of the non-aeration phase to the aeration phase is 3:

1.

6. The method for alleviating clogging and enhancing nitrogen and phosphorus removal performance of constructed wetlands based on sulfides according to claim 5, characterized in that, The non-aeration phase lasts for 90 minutes, and the aeration phase lasts for 30 minutes.

7. The method for alleviating clogging and enhancing nitrogen and phosphorus removal performance of constructed wetlands based on sulfides according to claim 1, characterized in that, The dissolved oxygen concentration during the aeration phase is 3 mg / L.

8. The method for alleviating clogging and enhancing nitrogen and phosphorus removal performance of constructed wetlands based on sulfides according to claim 3, characterized in that, The vertical flow constructed wetland comprises, from bottom to top, a water distribution layer, a support layer, a filler layer, and a surface water distribution layer.

9. The method for alleviating clogging and enhancing nitrogen and phosphorus removal performance of constructed wetlands based on sulfides according to claim 1, characterized in that, The functional microbial community enriched during the operation of the intermittent aeration mode includes sulfur autotrophic denitrifying bacteria and extracellular polymeric fermentation and degradation bacteria.

10. The method for alleviating clogging and enhancing nitrogen and phosphorus removal performance of constructed wetlands based on sulfides according to claim 9, characterized in that, The sulfur-autotrophic denitrifying bacteria are selected from at least one of Thiobacillus and Thiothrix, and the extracellular polymeric fermentation and degradation bacteria are Propionivibrio.