Method and system for synchronously removing nitrogen and phosphorus from agricultural ditch water with low carbon nitrogen ratio

Abstract

The invention provides a low-carbon-nitrogen-ratio agricultural ditch water synchronous nitrogen and phosphorus removal system and method, and the system comprises a plurality of fixed rods 10 fixed on a farmland ditch side slope, and elastic fillers 20 are arranged on the fixed rods; the elastic filler 20 sequentially comprises an upper-layer aerobic zone 201, a middle-layer facultative anaerobic zone 202 and a lower-layer anaerobic zone 203 from top to bottom; the surface of the filler of the upper-layer aerobic zone 201 is loaded with chlorella, botryococcus braunii and nitrifying bacteria; denitrifying bacteria are loaded on the surface of the filler of the middle-layer facultative zone 202; and denitrifying phosphorus removal bacteria are loaded on the surface of the filler of the lower anaerobic zone 203. According to the application, a chlorella-botryococcus braunii-nitrifying bacteria phycomycetic membrane is formed in the upper-layer aerobic zone, and an organic source can be provided for denitrification of the middle-layer facultative zone and denitrification phosphorus removal of the lower-layer anaerobic zone, so that the denitrification and phosphorus removal efficiency is improved, and the nitrogen and phosphorus removal rate is finally improved.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a method and system for synchronous denitrification and dephosphorization of low-carbon-nitrogen ratio agricultural ditch water. Background Art

[0002] Agricultural ditch water treatment is a key component of agricultural non-point source pollution control. Agricultural ditch water pollution primarily comes from fertilizer and pesticide residues (nitrogen, phosphorus, etc.), which enter the ditches with rainwater or irrigation drainage. Ditch water quality fluctuates seasonally. During the rainy season, runoff leads to high pollutant concentrations, and high nitrogen and phosphorus content can easily cause eutrophication of surrounding water bodies. Furthermore, in areas where fertilizers are frequently applied, such as intensive farmland, nitrogen and phosphorus content are high, and organic carbon is relatively insufficient. Furthermore, organic matter decomposes rapidly due to water movement, resulting in agricultural ditch water having a typical low carbon-nitrogen ratio.

[0003] At present, ecological treatment technology is mainly used to form ecological ditches for agricultural ditch water, that is, aquatic plants (such as reeds and cattails) are planted at the bottom and slopes of the ditch to absorb and adsorb suspended matter, and the organic matter and nitrogen and phosphorus in the ditch water are removed in combination with the microbial system, and the water quality is purified through the synergistic effect of plants and microorganisms. Here, the denitrification and phosphorus removal in ditch water mainly rely on the transformation process of microorganisms. For example, nitrification, denitrification, biological phosphorus removal and other denitrification and phosphorus removal pathways require sufficient organic carbon sources. However, for the currently common low carbon-nitrogen ratio ditch water (C / N < 5), the efficiency of traditional microbial denitrification and phosphorus removal is low, resulting in problems with the denitrification and phosphorus removal of agricultural ditch water, which can easily cause eutrophication of surrounding water bodies. Therefore, it is urgent to develop a new type of synchronous denitrification and phosphorus removal system to address the problem of low carbon-nitrogen ratio of agricultural ditch water. Summary of the Invention

[0004] In view of this, the technical problem to be solved by this application is to provide a method and system for synchronous denitrification and phosphorus removal of agricultural ditch water with a low carbon-nitrogen ratio. The method and system provided in this application are highly efficient when used for synchronous denitrification and phosphorus removal of agricultural ditch water with a low carbon-nitrogen ratio.

[0005] The present application provides a low carbon-nitrogen ratio agricultural ditch water synchronous denitrification and phosphorus removal system, comprising:

[0006] A plurality of fixing rods 10 fixed to the slope of the farmland ditch, wherein the fixing rods are provided with elastic fillers 20;

[0007] The elastic filler 20 comprises, from top to bottom, an upper aerobic zone 201, a middle facultative oxic zone 202, and a lower anaerobic zone 203; the filler surface of the upper aerobic zone 201 is loaded with Chlorella vulgaris, Botrytis cinerea, and nitrifying bacteria; the filler surface of the middle facultative oxic zone 202 is loaded with denitrifying bacteria; and the filler surface of the lower anaerobic zone 203 is loaded with denitrifying and phosphorus-removing bacteria.

[0008] In some specific implementations, the volume ratio of Chlorella vulgaris to Botrytis cinerea is 1 to 20:1;

[0009] The volume ratio of the chlorella to the nitrifying bacteria is 1-50:1-10.

[0010] In some specific implementations, the Chlorella is Chlorella C9-JN2010, and the Botrytis cinerea is B. brauni UTEX 57;

[0011] The nitrifying bacteria is at least one of the genus Nitrosomonas or Nitrobacter.

[0012] In some specific implementations, the height ratio of the upper aerobic zone 201, the middle facultative anaerobic zone 202 and the lower anaerobic zone 203 is 3-5:1:1.

[0013] In some specific implementations, the denitrifying bacteria is at least one of Pseudomonas, Alcaligenes, Paracoccus, and Bacillus;

[0014] The denitrifying and phosphorus-removing bacteria is at least one of the genera Pseudomonas and Alcaligenes.

[0015] In some specific implementations, a fixed pole is set every 0.5m to 1.0m on the slope of the farmland ditch.

[0016] In some specific implementations, the elastic filler filling ratios of the upper aerobic zone 201 , the middle facultative anaerobic zone 202 and the lower anaerobic zone 203 are independently selected from 60% to 80%.

[0017] In some specific implementations, the carbon-nitrogen ratio of the agricultural ditch water is 1-5.

[0018] The present application also provides a method for simultaneous nitrogen and phosphorus removal from agricultural ditch water with a low carbon-nitrogen ratio, comprising:

[0019] A plurality of fixing rods 10 are fixed on the slope of the farmland ditch, and elastic fillers 20 are provided on the fixing rods;

[0020] The elastic filler 20 is composed of an upper aerobic zone 201, a middle facultative aerobic zone 202, and a lower anaerobic zone 203 from top to bottom. The filler surface of the upper aerobic zone 201 is loaded with Chlorella vulgaris, Botrytis cinerea, and nitrifying bacteria; the filler surface of the middle facultative aerobic zone 202 is loaded with denitrifying bacteria; and the filler surface of the lower anaerobic zone 203 is loaded with denitrifying and phosphorus-removing bacteria.

[0021] Low carbon-nitrogen ratio agricultural ditch water is passed through elastic filler 20 for treatment.

[0022] In some specific implementations, the density ratio of Chlorella vulgaris to Botrytis cinerea is 1 to 20:1;

[0023] The volume ratio of the chlorella to the nitrifying bacteria is 1-50:1-10.

[0024] The present application provides a low-carbon-nitrogen ratio agricultural ditch water synchronous denitrification and phosphorus removal system, comprising: a plurality of fixed rods 10 fixed to the slope of the farmland ditch, wherein the fixed rods are provided with elastic fillers 20; the elastic fillers 20 are sequentially arranged from top to bottom into an upper aerobic zone 201, a middle facultative oxic zone 202, and a lower anaerobic zone 203; the filler surface of the upper aerobic zone 201 is loaded with Chlorella vulgaris, Botrytis cinerea, and nitrifying bacteria; the filler surface of the middle facultative oxic zone 202 is loaded with denitrifying bacteria; and the filler surface of the lower anaerobic zone 203 is loaded with denitrifying and phosphorus-removing bacteria. The present application forms an algae-bacteria symbiotic membrane of Chlorella vulgaris, Botrytis cinerea, and nitrifying bacteria in the upper aerobic zone. Chlorella vulgaris and Botrytis cinerea provide oxygen through photosynthesis, and nitrifying bacteria use the oxygen to oxidize ammonia nitrogen into nitrate. Nitrate is then reduced to nitrogen gas by denitrifying bacteria in the middle facultative oxic zone, using sulfide as an electron donor. The lower anaerobic zone is primarily enriched with denitrifying and phosphorus-removing bacteria, which carry out denitrification under anaerobic conditions and simultaneously absorb phosphorus. The present application forms an algae-bacteria symbiotic membrane of Chlorella vulgaris, Botrytis cinerea, and nitrifying bacteria in the upper aerobic zone, providing an organic source for denitrification in the middle facultative oxic zone and denitrification and phosphorus removal in the lower anaerobic zone, thereby improving the efficiency of denitrification and phosphorus removal. The experimental results show that compared with the system inoculated with Chlorella vulgaris without inoculating Botrytis cinerea, the system inoculated with both Botrytis cinerea and Chlorella vulgaris can increase the organic matter content in the middle facultative oxic zone from 32 mg / L to 45 mg / L, and increase the organic matter content in the lower anaerobic zone from 25 mg / L to 38 mg / L, the TN removal rate increases from 85% to 95%, and the TP removal rate increases from 75% to more than 85%. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a structural diagram of the system provided in an embodiment of the present application, wherein 10 is a fixing rod and 20 is an elastic filler. DETAILED DESCRIPTION

[0026] The present invention provides a method and system for simultaneous nitrogen and phosphorus removal from low-carbon-nitrogen ratio agricultural ditch water. Those skilled in the art can refer to the present disclosure and appropriately modify the process parameters to achieve this goal. The methods and applications of the present invention have been described using preferred embodiments. It is apparent that those skilled in the art can modify, alter, and combine the methods and applications described herein to implement and apply the technology of the present invention without departing from the content, spirit, and scope of the present invention.

[0027] The present application provides a low carbon-nitrogen ratio agricultural ditch water synchronous denitrification and phosphorus removal system, comprising:

[0028] A plurality of fixing rods 10 fixed to the slope of the farmland ditch, wherein the fixing rods are provided with elastic fillers 20;

[0029] The elastic filler 20 comprises, from top to bottom, an upper aerobic zone 201, a middle facultative oxic zone 202, and a lower anaerobic zone 203; the filler surface of the upper aerobic zone 201 is loaded with Chlorella vulgaris, Botrytis cinerea, and nitrifying bacteria; the filler surface of the middle facultative oxic zone 202 is loaded with denitrifying bacteria; and the filler surface of the lower anaerobic zone 203 is loaded with denitrifying and phosphorus-removing bacteria.

[0030] See also Figure 1 , Figure 1 This is a structural diagram of the system provided in an embodiment of the present application, wherein 10 is a fixing rod and 20 is an elastic filler.

[0031] The fixing rod 10 is used to fix the system in the slope of the farmland ditch, which includes a bottom rod 101, a first side rod 102 and a second side rod 103 respectively connected to the two ends of the bottom rod 101, a first top rod 104 connected to the first side rod 102 and a second top rod 105 connected to the second side rod 103. The fixing rod 10 is vertically fixed inside the ditch, wherein the bottom rod 101 is fixed to the bottom of the ditch, the first side rod 102 and the second side rod 103 are respectively fixed on both sides of the ditch, and the first top rod 104 and the second top rod 105 are respectively fixed on both sides of the top of the ditch.

[0032] The elastic filler 20 is mounted on a fixed rod 10 and is used to treat agricultural ditch water. The filler comprises an upper aerobic zone 201, a middle facultative oxic zone 202, and a lower anaerobic zone 203. The filler surface of the upper aerobic zone 201 is loaded with Chlorella vulgaris, Botrytis cinerea, and nitrifying bacteria, forming a bacterial-algal symbiotic system. Chlorella vulgaris and Botrytis cinerea provide oxygen through photosynthesis, and the nitrifying bacteria use the oxygen to oxidize ammonia nitrogen into nitrate. The filler surface of the middle facultative oxic zone 202 is loaded with denitrifying bacteria, which reduce nitrate to nitrogen gas. The filler surface of the lower anaerobic zone 203 is loaded with denitrifying and phosphorus-removing bacteria, which perform denitrification under anaerobic conditions and absorb phosphorus simultaneously. The present application inoculates Chlorella vulgaris and Botrytis cinerea in the upper aerobic zone 201, which can increase the organic matter content in the water, provide organic matter for denitrification in the middle facultative oxic zone and denitrification and phosphorus removal in the lower anaerobic zone, and enhance the nitrogen and phosphorus removal effects.

[0033] In some specific implementations, the volume ratio of Chlorella to Botrytis cinerea is 1-20:1, preferably 5-15:1, and more preferably 10:1. Chlorella grows faster than Botrytis cinerea, and its larger size facilitates oxygen production in the upper aerobic zone 201. In some specific implementations, the volume ratio of Chlorella to nitrifying bacteria is 1-50:1-10, preferably 1-30:1-10, and more preferably 1-20:1-10.

[0034] The present application has no special restrictions on Chlorella, which may be common Chlorella, such as Chlorella C9-JN2010. The present application has no special restrictions on Brown grape algae, which may be B. brauni UTEX 57 and the like. In the present application, the nitrifying bacteria are selected from at least one of the genera Nitrosomonas or Nitrobacter, the denitrifying bacteria are selected from at least one of the genera Pseudomonas, Alcaligenes, Paracoccus and Bacillus, and the denitrifying and phosphorus-removing bacteria are at least one of the genera Pseudomonas and Alcaligenes, and the present application has no special restrictions on them. The present application has no special restrictions on the elastic filler, which may be a polyolefin filler or a polyamide filler. The diameter of the elastic filler unit is preferably 80 mm to 150 mm, more preferably 90 mm to 140 mm; its specific surface area is preferably 250 m 2 / m 3 ~300m 2 / m 3 , more preferably 260m 2 / m 3 ~290m 2 / m 3 .

[0035] In some specific implementations, the height ratio of the upper aerobic zone 201, the middle facultative anaerobic zone 202, and the lower anaerobic zone 203 is 3 to 5:1:1. In some specific implementations, the elastic filler filling ratio of the upper aerobic zone 201, the middle facultative anaerobic zone 202, and the lower anaerobic zone 203 is independently selected from 60% to 80%, more preferably from 65% to 75%.

[0036] In some specific implementations, multiple denitrification and phosphorus removal systems can be set up in farmland ditches, for example, a fixed rod and elastic filler are set every 0.5m to 1.0m on the slope.

[0037] The denitrification and phosphorus removal system provided in this application can be used to treat agricultural ditch water, such as ditch water from rice fields and wheat fields. The COD in agricultural ditch water is about 30-80 mg / L, TN is about 5-20 mg / L, TP is about 1-5 mg / L, and C / N is about 1-5. In some specific implementations, the COD of agricultural ditch water is about 50-60 mg / L, TN is about 8-12 mg / L, TP is about 2 mg / L, and C / N is about 3.0-4.0.

[0038] The present application has no particular limitation on the preparation method of the monoalgae removal and phosphorus removal system. Chlorella and Botrytis cinerea, nitrifying bacteria, denitrifying bacteria and denitrifying phosphorus removal bacteria are expanded and cultured using methods well known to those skilled in the art, and then inoculated onto the elastic filler.

[0039] The present application also provides a method for simultaneous nitrogen and phosphorus removal from agricultural ditch water with a low carbon-nitrogen ratio, comprising:

[0040] A plurality of fixing rods 10 are fixed on the slope of the farmland ditch, and elastic fillers 20 are provided on the fixing rods;

[0041] The elastic filler 20 is composed of an upper aerobic zone 201, a middle facultative aerobic zone 202, and a lower anaerobic zone 203 from top to bottom. The filler surface of the upper aerobic zone 201 is loaded with Chlorella vulgaris, Botrytis cinerea, and nitrifying bacteria; the filler surface of the middle facultative aerobic zone 202 is loaded with denitrifying bacteria; and the filler surface of the lower anaerobic zone 203 is loaded with denitrifying and phosphorus-removing bacteria.

[0042] Low carbon-nitrogen ratio agricultural ditch water is passed through elastic filler 20 for treatment.

[0043] This application uses the denitrification and phosphorus removal system disclosed in the above technical solution to denitrify and remove phosphorus from agricultural ditch water with a low carbon-nitrogen ratio, with a high removal rate.

[0044] The present application provides a low-carbon-nitrogen ratio agricultural ditch water synchronous denitrification and phosphorus removal system, comprising: a plurality of fixed rods 10 fixed to the slope of the farmland ditch, wherein the fixed rods are provided with elastic fillers 20; the elastic fillers 20 are sequentially arranged from top to bottom into an upper aerobic zone 201, a middle facultative oxic zone 202, and a lower anaerobic zone 203; the filler surface of the upper aerobic zone 201 is loaded with Chlorella vulgaris, Botrytis cinerea, and nitrifying bacteria; the filler surface of the middle facultative oxic zone 202 is loaded with denitrifying bacteria; and the filler surface of the lower anaerobic zone 203 is loaded with denitrifying and phosphorus-removing bacteria. The present application forms an algae-bacteria symbiotic membrane of Chlorella vulgaris, Botrytis cinerea, and nitrifying bacteria in the upper aerobic zone. Chlorella vulgaris and Botrytis cinerea provide oxygen through photosynthesis, and nitrifying bacteria use the oxygen to oxidize ammonia nitrogen into nitrate. Nitrate is then reduced to nitrogen gas by denitrifying bacteria in the middle facultative oxic zone, using sulfide as an electron donor. The lower anaerobic zone is primarily enriched with denitrifying and phosphorus-removing bacteria, which carry out denitrification under anaerobic conditions and simultaneously absorb phosphorus. The present application forms an algae-bacteria symbiotic membrane of Chlorella vulgaris, Botrytis cinerea, and nitrifying bacteria in the upper aerobic zone, providing an organic source for denitrification in the middle facultative oxic zone and denitrification and phosphorus removal in the lower anaerobic zone, thereby improving the efficiency of denitrification and phosphorus removal. The experimental results show that compared with the system inoculated with Chlorella vulgaris without inoculating Botrytis cinerea, the system inoculated with both Botrytis cinerea and Chlorella vulgaris can increase the organic matter content in the middle facultative oxic zone from 32 mg / L to 45 mg / L, and increase the organic matter content in the lower anaerobic zone from 25 mg / L to 38 mg / L, the TN removal rate increases from 85% to 95%, and the TP removal rate increases from 75% to more than 85%.

[0045] The method and system for simultaneous denitrification and phosphorus removal of low carbon-nitrogen ratio agricultural ditch water provided by the present application are further described below with reference to the embodiments.

[0046] In the following examples, the chlorella was Chlorella vulgaris C9-JN2010, the brown grape algae was B. brauni UTEX 57, the nitrifying bacteria was Nitrosomonas europaea of ​​the genus Nitrosomonas, the denitrifying bacteria was Pseudomonas aeruginosa of the genus Pseudomonas, and the denitrifying and phosphorus-removing bacteria was Pseudomonas aeruginosa of the genus Pseudomonas, all of which were purchased from the market.

[0047] Example 1

[0048] Provide a number of fixing rods, each of which is provided with an elastic filler, see Figure 1 , Figure 1 This is a schematic structural diagram of the system provided in an embodiment of the present application, where 10 is a fixed rod and 20 is an elastic filler.

[0049] The fixing rod 10 includes a bottom rod 101, a first side rod 102 and a second side rod 103 respectively connected to the two ends of the bottom rod 101, a first top rod 104 connected to the first side rod 102 and a second top rod 105 connected to the second side rod 103. The fixing rod 10 is vertically fixed inside the ditch, wherein the bottom rod 101 is fixed to the bottom of the ditch, the first side rod 102 and the second side rod 103 are respectively fixed on both sides of the ditch, and the first top rod 104 and the second top rod 105 are respectively fixed on both sides of the top of the ditch.

[0050] The elastic filler 20 includes an upper aerobic zone 201, a middle facultative aerobic zone 202, and a lower anaerobic zone 203. The height ratio of the upper aerobic zone 201, the middle facultative aerobic zone 202, and the lower anaerobic zone 203 is 3:1:1. The filler filling ratios of the upper aerobic zone 201, the middle facultative aerobic zone 202, and the lower anaerobic zone 203 are 60%, respectively. The elastic filler is mainly composed of polyolefins and polyamides, has a diameter of 80 mm, and a specific surface area of ​​250 m 2 / m 3 .

[0051] Chlorella vulgaris and Botrytis cinerea were cultured to the logarithmic growth phase and their OD values ​​were adjusted. 750 All of them are 1; after the nitrifying bacteria, denitrifying bacteria and denitrifying phosphorus removal bacteria were expanded and cultured, their OD values ​​were adjusted. 600 In the upper aerobic zone 201, the inoculation volume ratio of Chlorella vulgaris, Botrytis cinerea and nitrifying bacteria was 10:1:10, among which the inoculation volume of Chlorella vulgaris was 10mL / m 3 Filler, inoculate 10mL / m in the middle layer of the facultative oxygen zone 202 3 Denitrifying bacteria of the filler are inoculated in the lower anaerobic zone 203 at 5 mL / m 3 Denitrifying and phosphorus removal bacteria in the filler.

[0052] To provide paddy field drainage, the water quality COD is about 50-60 mg / L, TN is about 8-12 mg / L, TP is about 2 mg / L, C / N is about 3.0-4.0. The above system is used for treatment. After 24 hours of residence and stable operation of the system, the organic matter content in the upper layer is about 35 mg / L, the organic matter content in the middle layer is about 45 mg / L, and the organic matter content in the lower layer is about 38 mg / L, which provides a good organic carbon source for denitrification and denitrifying phosphorus removal. After 48 hours, the TN removal rate of the effluent is 95.5%, and the TP removal rate is 88%.

[0053] Example 2

[0054] Compared with Example 1, the difference is that the upper aerobic zone 201 is inoculated with Chlorella vulgaris, Botrytis cinerea, and nitrifying bacteria in a volume ratio of 5:1:10, and the other steps and conditions are the same. After a 24-hour residence and stable operation of the system, the organic matter content in the upper layer is detected to be approximately 38 mg / L, the organic matter content in the middle layer is approximately 46 mg / L, and the organic matter content in the lower layer is approximately 40 mg / L, providing a good organic carbon source for denitrification and denitrifying phosphorus removal. After 48 hours, the TN removal rate of the effluent is 96.5%, and the TP removal rate is 86%.

[0055] Example 3

[0056] Compared with Example 1, the difference is that the upper aerobic zone 201 is inoculated with Chlorella vulgaris, Botrytis cinerea, and nitrifying bacteria in a volume ratio of 15:1:10, and the other steps and conditions are the same. After a 24-hour residence and stable operation of the system, the organic matter content in the upper layer is detected to be approximately 32 mg / L, the organic matter content in the middle layer is approximately 45 mg / L, and the organic matter content in the lower layer is approximately 37 mg / L, providing a good organic carbon source for denitrification and denitrifying phosphorus removal. After 48 hours, the TN removal rate of the effluent is 94.6%, and the TP removal rate is 89%.

[0057] Comparative Example 1

[0058] Compared with Example 1, the difference is that the upper aerobic zone 201 is inoculated with Chlorella and nitrifying bacteria in a volume ratio of 11:10, that is, the same volume of Chlorella is used instead of Botrytis cinerea. Other steps and conditions are the same. After a 24-hour residence time and stable operation of the system, the organic matter content in the upper layer is detected to be approximately 35 mg / L, the organic matter content in the middle layer is approximately 32 mg / L, and the organic matter content in the lower layer is approximately 25 mg / L. After 48 hours, the TN removal rate of the effluent is 85%, and the TP removal rate is 75%.

[0059] The above are only preferred embodiments of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A low carbon-nitrogen ratio agricultural ditch water simultaneous nitrogen and phosphorus removal system, comprising: A plurality of fixing rods (10) fixed to the slope of a farmland ditch, wherein elastic fillers (20) are provided on the fixing rods; The elastic filler (20) is composed of an upper aerobic zone (201), a middle facultative oxic zone (202) and a lower anaerobic zone (203) from top to bottom; the filler surface of the upper aerobic zone (201) is loaded with Chlorella vulgaris, Botrytis cinerea and nitrifying bacteria; the filler surface of the middle facultative oxic zone (202) is loaded with denitrifying bacteria; and the filler surface of the lower anaerobic zone (203) is loaded with denitrifying and phosphorus-removing bacteria.

2. The low carbon-nitrogen ratio agricultural ditch water synchronous denitrification and phosphorus removal system according to claim 1 is characterized in that: The volume ratio of the Chlorella vulgaris to the Botrytis cinerea is 1 to 20:1; The volume ratio of the chlorella to the nitrifying bacteria is 1-50:1-10.

3. The low carbon-nitrogen ratio agricultural ditch water synchronous denitrification and phosphorus removal system according to claim 2 is characterized in that: The chlorella is chlorella C9-JN2010, and the brown grape algae is B. brauni UTEX 57; The nitrifying bacteria is at least one of the genus Nitrosomonas or Nitrobacter.

4. The low carbon-nitrogen ratio agricultural ditch water synchronous denitrification and phosphorus removal system according to claim 1 is characterized in that: The height ratio of the upper aerobic zone (201), the middle facultative oxic zone (202) and the lower anaerobic zone (203) is 3-5:1:

1.

5. The low carbon-nitrogen ratio agricultural ditch water synchronous denitrification and phosphorus removal system according to claim 1 is characterized in that: The denitrifying bacteria is at least one of the genera Pseudomonas, Alcaligenes, Paracoccus and Bacillus; The denitrifying and phosphorus-removing bacteria is at least one of the genera Pseudomonas and Alcaligenes.

6. The low carbon-nitrogen ratio agricultural ditch water synchronous denitrification and phosphorus removal system according to any one of claims 1 to 5, characterized in that: A fixed pole is set every 0.5m to 1.0m on the slope of the farmland ditch.

7. The low carbon-nitrogen ratio agricultural ditch water synchronous denitrification and phosphorus removal system according to claim 6 is characterized in that: The elastic filler filling ratios of the upper aerobic zone (201), the middle facultative anaerobic zone (202) and the lower anaerobic zone (203) are independently selected from 60% to 80%.

8. The low carbon-nitrogen ratio agricultural ditch water synchronous denitrification and phosphorus removal system according to claim 7 is characterized in that: The carbon-nitrogen ratio of the agricultural ditch water is 1-5.

9. A method for simultaneous nitrogen and phosphorus removal from low carbon-nitrogen ratio agricultural ditch water, comprising: A plurality of fixing rods (10) are fixed on the slope of a farmland ditch, wherein elastic fillers (20) are provided on the fixing rods; The elastic filler (20) is composed of an upper aerobic zone (201), a middle facultative oxic zone (202), and a lower anaerobic zone (203) from top to bottom; the filler surface of the upper aerobic zone (201) is loaded with Chlorella vulgaris, Botrytis cinerea, and nitrifying bacteria; the filler surface of the middle facultative oxic zone (202) is loaded with denitrifying bacteria; and the filler surface of the lower anaerobic zone (203) is loaded with denitrifying and phosphorus-removing bacteria. Low carbon-nitrogen ratio agricultural ditch water is treated by passing it through elastic filler (20).

10. The method according to claim 9, characterized in that The density ratio of the Chlorella vulgaris to the Botrytis cinerea is 1 to 20:1; The volume ratio of the chlorella to the nitrifying bacteria is 1-50:1-10.

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