Nitrogen and phosphorus removal system for eel culture tail water

Abstract

The utility model belongs to the field of environmental protection and water resource recycling, and particularly relates to a nitrogen and phosphorus removal system for eel culture tail water. The system provided by the utility model comprises a sedimentation tank, a hydrolysis acidification tank, a denitrification bed and an adsorption dephosphorization bed which are communicated in sequence, the denitrification bed comprises at least one denitrification tank, denitrification filler, a supporting plate for supporting the denitrification filler, an aeration pipe I and a cover plate I, the aeration pipe I is arranged at the bottom of the denitrification tank, and a denitrification filler area formed by the denitrification filler and the supporting plate is arranged in the denitrification tank and above the aeration pipe I; the adsorption dephosphorization bed comprises a dephosphorization tank, an adsorption dephosphorization filler, a supporting grid for supporting the adsorption dephosphorization filler, an aeration pipe II and a cover plate II, the aeration pipe II is arranged at the bottom of the dephosphorization tank, and an adsorption dephosphorization filler area formed by the adsorption dephosphorization filler and the supporting grid is arranged in the dephosphorization tank and is arranged above the aeration pipe II. By adopting the system provided by the utility model to treat the eel culture tail water, nitrogen and phosphorus can be efficiently removed, the adopted facilities are few, the structure is simple, and the purification cost and investment are low.

Description

Technical Field

[0001] The present application belongs to the field of environmental protection and water resource recycling, and specifically relates to a system for denitrification and phosphorus removal of eel farming tail water. Background Art

[0002] During the eel farming process, about 20% of the stale water in the breeding pond is discharged regularly every morning and evening, which is called breeding tail water. The concentrations of the main pollutants in the eel breeding tail water, such as ammonia nitrogen, total nitrogen, total phosphorus and COD, are related to factors such as the growth period, season, breeding mode, and drainage method of the eels. The main pollutants and concentrations are COD Cr About 20-30 mg / L, BOD5 about 5-10 mg / L, ammonia nitrogen about 0.5-7 mg / L, total nitrogen about 3-20 mg / L, total phosphorus about 1-3.5 mg / L. If the eel breeding tail water is discharged directly, it will cause COD in natural water bodies such as rivers and lakes. Cr , BOD5, nitrogen and phosphorus concentrations exceed the standard, and the water body is eutrophic. Therefore, in recent years, the country has attached great importance to the discharge management of aquaculture tailwater. According to the unified requirements of the state, various provinces have successively promulgated and implemented aquaculture tailwater discharge standards, such as Fujian Province promulgated the "Aquaculture Tailwater Discharge Standard" (DB35 / 2160-2003) in 2023 and implemented it from January 1, 2024, Guangdong Province promulgated the "Aquaculture Tailwater Discharge Standard" (DB44 / 2462-2024) in 2024, etc. These local standards respectively stipulate the discharge indicators of tailwater pH, COD, total nitrogen, total phosphorus and SS.

[0003] At present, physical, chemical and biochemical methods can be used to measure the COD in eel aquaculture tail water. Cr , BOD5, ammonia nitrogen, total nitrogen, total phosphorus and other pollutants. Among them, physical methods include nanofiltration, reverse osmosis, distillation, soil irrigation adsorption, adsorption and ion exchange and other treatment technologies; chemical methods include ammonia stripping, breakpoint chlorination, incineration, chemical precipitation, catalytic cracking, electrodialysis, chemical strong oxidation and electrochemical strong oxidation and other treatment technologies; biological methods include activated sludge method, biofilm method, algae cultivation and aquatic plant cultivation (artificial wetland) and other treatment technologies. Due to the characteristics of eel farming, the amount of tail water discharged is large and the COD Cr, BOD5 concentration is low, carbon, nitrogen, phosphorus ratio is seriously imbalanced, when using the biochemical method or artificial wetland method commonly used in wastewater treatment, it is necessary to continuously add carbon source to ensure the removal efficiency of pollutants, resulting in high treatment cost and poor operation effect; when using the combination of oxidation pond and sedimentation method to remove total phosphorus and total nitrogen, due to the need to add a large amount of coagulant, the amount of sludge is greatly increased, which not only increases the operation cost, but also has poor phosphorus removal effect. It can be seen that the treatment of eel breeding tailwater mainly focuses on improving the efficiency of denitrification and phosphorus removal. Although the prior art also uses a combination of catalytic electrolytic denitrification and adsorption dephosphorization tower to treat eel breeding tailwater, this method has a large initial investment cost and high operating costs, and is not suitable for further improvement to improve the denitrification and phosphorus removal efficiency of eel breeding tailwater. Therefore, with the promulgation and implementation of the new local standards, there is an urgent need for an economical and practical eel breeding tailwater treatment system with high denitrification and phosphorus removal efficiency. Utility Model Content

[0004] The purpose of the present application is to provide a system for denitrification and phosphorus removal of eel farming tail water with low purification cost and high denitrification and phosphorus removal efficiency in order to solve the problem that the denitrification and phosphorus removal efficiency of eel farming tail water in the prior art is low and the economic cost is high.

[0005] Specifically, the eel farming tailwater denitrification and phosphorus removal system provided in this application adopts the following technical solutions:

[0006] A denitrification and phosphorus removal system for eel breeding tail water, the system comprises a sedimentation tank, a hydrolysis acidification tank, a denitrification bed, and an adsorption dephosphorization bed which are connected in sequence; the denitrification bed comprises at least one denitrification tank, a denitrification filler, a support plate for supporting the denitrification filler, an aeration pipe I and a cover plate I, the aeration pipe I is arranged at the bottom of the denitrification tank, the denitrification filler area formed by the denitrification filler and the support plate is arranged in the denitrification tank and above the aeration pipe I, and the cover plate I is arranged above the denitrification tank; the adsorption dephosphorization bed comprises at least one dephosphorization tank, an adsorption dephosphorization filler, a support grid for supporting the adsorption dephosphorization filler, an aeration pipe II and a cover plate II, the aeration pipe II is arranged at the bottom of the dephosphorization tank, the adsorption dephosphorization filler area formed by the adsorption dephosphorization filler and the support grid is arranged in the dephosphorization tank and above the aeration pipe II, and the cover plate II is arranged above the dephosphorization tank.

[0007] In some specific embodiments, the denitrification filler is a porous expanded denitrification filler with an average particle size of 5 to 80 mm and a specific surface area of ​​8 to 10 m 2 / g, bulk density is 430~820kg / m 3 , dry density ≤820kg / m 3 , cylinder pressure strength ≥4.5MPa, porosity ≥70%, water absorption ≥35%.

[0008] In some specific embodiments, the adsorption and phosphorus removal filler is a porous expanded adsorption and phosphorus removal filler with an average particle size of 3 to 50 mm and a specific surface area of ​​8 to 10 m 2 / g, bulk density is 410~600kg / m 3 , dry density ≤750kg / m 3 , cylinder pressure strength ≥3.5MPa, porosity ≥73%, water absorption ≥65%.

[0009] In some specific embodiments, the sedimentation tank and the hydrolysis acidification tank are further provided with a filter, the water inlet of the filter is connected to the water outlet of the sedimentation tank, and the water outlet of the filter is connected to the water inlet of the hydrolysis acidification tank.

[0010] In some specific embodiments, the filter is a rotary filter or a fiber disc filter.

[0011] In some specific embodiments, the pore size of the filter cloth of the filter is 10 to 70 μm.

[0012] In addition, when the eel farming tail water denitrification and phosphorus removal system provided in the present application is used to treat eel farming tail water, the treatment method includes the following steps:

[0013] S1. Sedimentation treatment: The eel breeding tail water is discharged into the sedimentation tank, and the solid particles in the water are removed by sedimentation. The resulting supernatant enters the hydrolysis acidification tank;

[0014] S2. Hydrolysis and acidification treatment: In the hydrolysis and acidification tank, the ammonia nitrogen in the supernatant is nitrified into nitrate nitrogen, the organic phosphorus is converted into inorganic phosphate, and the COD in the supernatant is removed;

[0015] S3. Denitrification treatment: The tail water after hydrolysis and acidification enters the denitrification bed, and the nitrifying bacteria in the denitrification filler oxidize the ammonia nitrogen in the water into nitrate nitrogen, and the denitrifying bacteria in the denitrification filler reduce the nitrate nitrogen in the water into nitrogen gas, removing the ammonia nitrogen and total nitrogen in the water, so that the ammonia nitrogen in the effluent is ≤1mg / L and the total nitrogen is ≤3mg / L;

[0016] S4. Adsorption phosphorus removal treatment: The tail water after denitrification treatment enters the adsorption phosphorus removal bed, and the phosphate ions in the water are removed by the adsorption phosphorus removal filler, and the total phosphorus in the water is removed, so that the ammonia nitrogen in the effluent is ≤1mg / L, the total nitrogen is ≤3mg / L, and the total phosphorus is ≤0.2mg / L.

[0017] In some specific embodiments, the denitrification filler in the denitrification bed is obtained by mixing diatomaceous earth powder, gypsum powder, zeolite powder, cement and cement foaming agent and performing foaming, pulping, solidification, crushing and screening.

[0018] In some specific embodiments, the average particle size of the diatomaceous earth powder is 20 to 50 μm.

[0019] In some specific embodiments, the average particle size of the denitrification filler is 5 to 80 mm, and the specific surface area is 8 to 10 m 2 / g, bulk density is 430~820kg / m 3 , dry density ≤820kg / m 3 , cylinder pressure strength ≥4.5MPa, porosity ≥70%, water absorption ≥35%.

[0020] In some specific embodiments, the adsorption dephosphorization filler in the adsorption dephosphorization bed is obtained by mixing gypsum powder, calcium hydroxide powder, iron oxyhydroxide powder, cement and cement foaming agent and performing foaming, pulping, curing, crushing and screening.

[0021] In some specific embodiments, the average particle size of the iron oxyhydroxide powder is 20 to 50 μm.

[0022] In some specific embodiments, the average particle size of the adsorption and phosphorus removal filler is 3 to 50 mm, and the specific surface area is 8 to 10 m 2 / g, bulk density is 410~600kg / m 3 , dry density ≤750kg / m 3 , cylinder pressure strength ≥3.5MPa, porosity ≥73%, water absorption ≥65%.

[0023] Beneficial effects:

[0024] (1) All tail water discharges meet the standards: In the system provided in the present application, the tail water of eel farming first enters the sedimentation tank, where solid particles in the water are removed by sedimentation, and the resulting supernatant enters the hydrolysis and acidification tank, where the ammonia nitrogen in the supernatant is nitrified into nitrate nitrogen, organic phosphorus is converted into inorganic phosphate, and part of the COD in the supernatant is removed; the tail water after hydrolysis and acidification enters the denitrification bed, where the nitrifying bacteria in the denitrification filler oxidize the ammonia nitrogen in the water into nitrate nitrogen, and the denitrifying bacteria in the denitrification filler reduce the nitrate nitrogen in the water to nitrogen gas, thereby removing ammonia nitrogen and total nitrogen from the water; the tail water after denitrification treatment enters the adsorption and phosphorus removal bed, where the phosphate radicals in the water are removed by the action of the adsorption and phosphorus removal filler, and the total phosphorus in the water is removed; through the sedimentation, hydrolysis and acidification of the tail water and the denitrification and adsorption and phosphorus removal, the pH of the effluent is 6-9, and the COD Cr ≤10mg / L, ammonia nitrogen ≤1.0mg / L, total nitrogen ≤3mg / L, total phosphorus ≤0.2mg / L, suspended solids less than 45mg / L, meeting the emission standards;

[0025] (2) Simple facilities and low investment: The eel tail water denitrification and phosphorus removal purification system adopted in this application only has a sedimentation tank, a hydrolysis acidification tank, a denitrification bed, and an adsorption dephosphorization bed, and the facilities are simple;

[0026] (3) Low purification cost: The system and method of the present application are used to purify eel aquaculture tail water, with a treatment cost of ≤0.20 yuan / ton, which is low;

[0027] (4) Low investment: This application requires few facilities, simple structure, and uses low-cost raw materials. Compared with other methods, it can significantly save investment costs, and can even reduce investment by half;

[0028] (5) Simple operation: The treatment facilities in this application all use natural gravity flow, do not require special personnel to supervise, and are simple to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a process flow chart of a system for denitrification and phosphorus removal from eel farming tail water according to an embodiment of the present application.

[0030] Figure 2 It is a cross-sectional schematic diagram of a denitrification bed according to an embodiment of the present application.

[0031] Figure 3 It is a cross-sectional schematic diagram of an adsorption phosphorus removal bed according to an embodiment of the present application.

[0032] Figure numerals: 10, sedimentation tank; 20, filter; 30, hydrolysis acidification tank; 40, denitrification bed; 41, denitrification tank; 42, denitrification filler; 43, support plate; 44, aeration pipe I; 45, cover plate I; 46, water inlet distributor I; 47, air pipe I; 50, adsorption phosphorus removal bed; 51, dephosphorization tank; 52, adsorption phosphorus removal filler; 53, support grid; 54, aeration pipe II; 55, cover plate II; 56, water inlet distributor II; 57, air pipe II. DETAILED DESCRIPTION

[0033] The specific implementation of the present application is described in detail below. It should be understood that the specific implementation described here is only used to illustrate and explain the present application, and is not used to limit the present application.

[0034] See also Figures 1 to 3 The eel breeding tailwater denitrification and phosphorus removal system provided in the present application comprises a sedimentation tank 10, a hydrolysis acidification tank 30, a denitrification bed 40, and an adsorption dephosphorization bed 50 which are connected in sequence. The water outlet of the sedimentation tank 10 is connected to the water inlet of the hydrolysis acidification tank 30, the water outlet of the hydrolysis acidification tank 30 is connected to the water inlet of the denitrification bed 40, the water outlet of the denitrification bed 40 is connected to the water inlet of the adsorption dephosphorization bed 50, and the water outlet of the adsorption dephosphorization bed 50 meets the discharge standards.

[0035] The denitrification bed 40 includes at least one denitrification tank 41, a denitrification filler 42, a support plate 43 for supporting the denitrification filler 42, an aeration pipe I 44 and a cover plate I 45. The aeration pipe I 44 is arranged at the bottom of the denitrification tank 41. The denitrification filler 42 area formed by the denitrification filler 42 and the support plate 43 is arranged in the denitrification tank 41 and above the aeration pipe I 44. The cover plate I 45 is arranged above the denitrification tank 41. The adsorption dephosphorization bed 50 includes at least one dephosphorization tank 51, an adsorption dephosphorization filler 52, a support grid 53 for supporting the adsorption dephosphorization filler 52, an aeration pipe II 54 and a cover plate II 55. The aeration pipe II 54 is arranged at the bottom of the dephosphorization tank 51. The adsorption dephosphorization filler 52 area formed by the adsorption dephosphorization filler 52 and the support grid 53 is arranged in the dephosphorization tank 51 and above the aeration pipe II 54. The cover plate II 55 is arranged above the dephosphorization tank 51.

[0036] In this embodiment, there are three denitrification tanks 41. The water inlet is arranged at the top of the first denitrification tank 41 and connected to the water inlet distributor Ⅰ46. An air pipe Ⅰ47 is also provided in the denitrification tank 41, and the air pipe Ⅰ47 connects the aeration pipe Ⅰ44 with the external air.

[0037] In some specific embodiments, the denitrification filler 42 is a porous expanded denitrification filler, and the average particle size is preferably 5 to 80 mm, such as 5 mm, 10 mm, 20 mm, 50 mm, 60 mm, 80 mm or any value therebetween; the specific surface area is preferably 8 to 10 m 2 / g, such as 8m 2 / g, 8.5m 2 / g, 9m 2 / g, 9.5m 2 / g, 10m 2 / g or any value therebetween; the bulk density is preferably 430 to 820 kg / m 3 , such as 430kg / m 3 , 480kg / m 3 , 500kg / m 3 、600kg / m 3 , 700kg / m 3 , 800kg / m 3 、820kg / m 3 Or any value between them; dry density ≤820kg / m 3, cylinder pressure strength ≥4.5MPa, porosity ≥70%, water absorption ≥35%. The above-mentioned porous expanded denitrification filler is selected, which has a rich honeycomb porous structure. These honeycomb pores are more conducive to the proliferation of a large number of nitrifying bacteria and denitrifying bacteria. Its porous structure is conducive to the simultaneous adsorption of nitrifying bacteria and denitrifying bacteria as well as ammonia nitrogen, nitrate nitrogen and organic nutrients in the water body on its surface to form a local concentration, so that ammonia nitrogen and nitrate nitrogen in the water body can be quickly and efficiently removed, and the concentration of ammonia nitrogen and total nitrogen in the water can be reduced.

[0038] In this embodiment, the number of adsorption dephosphorization tanks 51 is 3, the water inlet is arranged at the top of the first adsorption dephosphorization tank 51 and connected to the water inlet distributor Ⅱ56, and an air pipe Ⅱ57 is also provided in the dephosphorization tank 51, and the air pipe Ⅱ57 connects the aeration pipe Ⅱ54 with the external air.

[0039] In some specific embodiments, the adsorption and dephosphorization filler 52 is a porous expanded adsorption and dephosphorization filler, and the average particle size is preferably 3 to 50 mm, such as 3 mm, 5 mm, 10 mm, 20 mm, 30 mm, 40 mm, 50 mm or any value therebetween; the specific surface area is preferably 8 to 10 m 2 / g, such as 8m 2 / g, 8.5m 2 / g, 9m 2 / g, 9.5m 2 / g, 10m 2 / g or any value therebetween; bulk density is 410~600kg / m 3 , such as 410kg / m 3 , 450kg / m 3 , 480kg / m 3 , 500kg / m 3 , 520kg / m 3 , 550kg / m 3 、580kg / m 3 、600kg / m 3 Or any value between them; dry density ≤750kg / m 3 , cylinder pressure strength ≥3.5MPa, porosity ≥73%, water absorption ≥65%. The porous expansion adsorption phosphorus removal has a honeycomb porous structure, which is conducive to adsorbing phosphate in water on the surface of the filler, thereby reducing the total phosphorus concentration in the water.

[0040] In addition, the adsorption dephosphorization filler 52 can be replaced with a new filler after being saturated with adsorption, or it can be regenerated to desorb the adsorbed phosphorus and then continue to be used. The regeneration method of the adsorption dephosphorization filler 52 can be alkaline washing regeneration and / or acid washing regeneration.

[0041] In some specific embodiments, the sedimentation tank 10 can be, but is not limited to, a circular or polygonal concrete casting tank body with a depth of 4 to 6 meters, which is used to collect and precipitate the tail water discharged from eel farming. On the one hand, solid particles such as eel feces and residual feed in the tail water can be removed by sedimentation, and on the other hand, anaerobic microorganisms in the sedimentation tank 10 can be used to remove COD in the sewage. Cr , BOD5 is oxidized into CO2 and organic nitrogen is hydrolyzed into ammonia nitrogen, nitrate ions are denitrified into nitrogen gas, and phosphorus-containing organic matter is oxidized and decomposed into inorganic phosphates. In addition, the water outlet of the sedimentation tank 10 can be set as an overflow port, and the effluent flows out through the overflow port and enters the hydrolysis acidification tank 30.

[0042] In some specific embodiments, the hydrolysis acidification tank 30 can be, but is not limited to, a circular or polygonal concrete cast tank body with a depth of 4 to 6 meters. In the hydrolysis acidification tank 30, organic nitrogen in the water is converted into ammonia nitrogen, organic phosphorus is converted into inorganic phosphate, and part of the organic matter is oxidized and decomposed and removed.

[0043] In some specific embodiments, the sedimentation tank 10 and the hydrolysis acidification tank 30 are further provided with a filter 20, the water inlet of the filter 20 is connected to the water outlet of the sedimentation tank 10, and the water outlet of the filter 20 is connected to the water inlet of the hydrolysis acidification tank 30. In this embodiment, the filter 20 may be provided with a mud discharge port, which is connected to the sedimentation tank 10. Further, the filter 20 may be a rotary filter or a fiber rotary filter. The filter cloth pore size of the filter 20 is preferably 10 to 70 μm, such as 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm or any value therebetween.

[0044] In addition, when the eel farming tail water denitrification and phosphorus removal system provided in the present application is used to treat eel farming tail water, the treatment method may include the following steps:

[0045] S1. Sedimentation treatment: The eel breeding tail water is discharged into the sedimentation tank 10, and the solid particles in the water are removed by sedimentation, and the COD Cr , BOD is oxidized into CO2 and organic phosphorus is converted into inorganic phosphate, and the resulting supernatant enters the hydrolysis acidification tank 30;

[0046] S2. Hydrolysis and acidification treatment: In the hydrolysis and acidification tank 30, the ammonia nitrogen in the supernatant is nitrified into nitrate nitrogen, the organic phosphorus is converted into inorganic phosphate, and the COD in the supernatant is removed;

[0047] S3. Denitrification treatment: the tail water after hydrolysis and acidification enters the denitrification bed 40, and the nitrifying bacteria in the denitrification filler 42 oxidize the ammonia nitrogen in the water into nitrate nitrogen, and the denitrifying bacteria in the denitrification filler 42 reduce the nitrate nitrogen in the water into nitrogen gas, thereby removing the ammonia nitrogen and total nitrogen in the water, so that the ammonia nitrogen in the effluent is ≤1mg / L and the total nitrogen is ≤3mg / L;

[0048] S4. Adsorption phosphorus removal treatment: The tail water after denitrification treatment enters the adsorption phosphorus removal bed 50, and the phosphate radicals in the water are removed by the adsorption phosphorus removal filler 52, and the total phosphorus in the water is removed, so that the ammonia nitrogen in the effluent is ≤1mg / L, the total nitrogen is ≤3mg / L, and the total phosphorus is ≤0.2mg / L.

[0049] In some specific embodiments, the denitrification filler 42 in the denitrification bed 40 can be various existing denitrification fillers, or can be a denitrification filler obtained by mixing diatomite powder, gypsum powder, zeolite powder, cement and cement foaming agent, and then foaming, slurrying, curing, crushing and screening. The average particle size of the diatomite powder is preferably 20 to 50 μm, such as 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm or any value therebetween. The denitrifying filler 42 prepared by the above method not only has a rich honeycomb porous structure, which is beneficial to the proliferation of nitrifying bacteria and denitrifying bacteria, but also contains gypsum (calcium sulfate dihydrate) that provides a sulfur source for sulfur autotrophic bacteria (denitrifying bacteria), which is more conducive to their rapid reproduction. At the same time, since diatomaceous earth has a strong adsorption capacity, it can adsorb nitrifying bacteria and denitrifying bacteria as well as ammonia nitrogen, nitrate nitrogen and organic nutrients in the water body on the surface of the filler to form a local concentration, which is suitable for the rapid reproduction of nitrifying bacteria and denitrification, thereby being more conducive to the rapid and efficient removal of ammonia nitrogen, nitrate nitrogen and total nitrogen in the water.

[0050] Furthermore, the average particle size of the denitrification filler 42 is preferably 5 to 80 mm, and the specific surface area is preferably 8 to 10 m 2 / g, and the bulk density is preferably 430 to 820 kg / m 3 , dry density ≤820kg / m 3 , cylinder pressure strength ≥4.5MPa, porosity ≥70%, water absorption ≥35%.

[0051] In some specific embodiments, the adsorption dephosphorization filler 52 in the adsorption dephosphorization bed 50 can be various existing adsorption dephosphorization fillers, or it can be an adsorption dephosphorization filler obtained by mixing oxyhydroxide iron powder, gypsum powder, calcium hydroxide powder, cement and cement foaming agent, and then foaming, pulping, curing, crushing and screening. Among them, the average particle size of the oxyhydroxide iron powder is preferably 20 to 50 μm, such as 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm or any value therebetween. The adsorption dephosphorization filler 52 prepared by the above method not only has a honeycomb porous structure, but also the calcium sulfate on the surface of the filler is slightly soluble in water (solubility 0.2g) to form a local high-concentration calcium ion layer (multiple electric layers), which reacts with phosphate in the water to form calcium phosphate and adsorbs on the surface of the filler. The reaction formula is shown below, which is more conducive to quickly and efficiently reducing the total phosphorus concentration in the water.

[0052] CaSO4·2H2O→Ca 2+ +SO4 2- +2H2O

[0053] 3Ca 2+ +2PO4 3- →Ca3(PO4)2

[0054] Furthermore, the average particle size of the adsorption and dephosphorization filler 52 is preferably 3 to 50 mm, and the specific surface area is preferably 8 to 10 m 2 / g, and the bulk density is preferably 410 to 600 kg / m 3 , dry density ≤750kg / m 3 , cylinder pressure strength

[0055] ≥3.5MPa, porosity ≥73%, water absorption ≥65%.

[0056] The present application will be described in detail below through specific embodiments.

[0057] Example 1 Eel breeding tail water denitrification and phosphorus removal system and method, with a daily processing capacity of 3000 tons / day

[0058] (1) See Figures 1 to 3 The eel breeding tailwater denitrification and phosphorus removal system provided in this embodiment includes a sedimentation tank 10, a hydrolysis acidification tank 30, a denitrification bed 40, and an adsorption dephosphorization bed 50 which are connected in sequence. The water outlet of the sedimentation tank 10 is connected to the water inlet of the hydrolysis acidification tank 30, the water outlet of the hydrolysis acidification tank 30 is connected to the water inlet of the denitrification bed 40, the water outlet of the denitrification bed 40 is connected to the water inlet of the adsorption dephosphorization bed 50, and the water outlet of the adsorption dephosphorization bed 50 meets the discharge standards.

[0059] The sedimentation tank 10 is a circular concrete casting tank with a diameter of 10m, a depth of 5m, and a designed retention time of 4h. It is used to collect and precipitate wastewater discharged from eel farming, and to precipitate and remove eel feces and residual feed in the wastewater. At the same time, the anaerobic microorganisms in the sedimentation tank are used to reduce the COD in the sewage. Cr , BOD5 is oxidized into carbon dioxide, organic nitrogen is hydrolyzed into ammonia nitrogen, nitrate ions are denitrified into nitrogen gas, and at the same time, a large amount of phosphorus-containing organic matter in the sewage is oxidized and decomposed into inorganic phosphates.

[0060] The hydrolysis acidification tank 30 is a rectangular water tank with a length, width and height of 10×10×5 m and a retention time of 4 hours. In the hydrolysis acidification tank 30, organic nitrogen is converted into ammonia nitrogen, organic phosphorus is converted into inorganic phosphate, and part of the organic matter is oxidized and decomposed to be removed.

[0061] The denitrification bed 40 is a rectangular water tank body with a length, width and height of 10×10×3m. The filling thickness of the denitrification filler 42 is 2.5m, and the designed residence time is 2h. In the denitrification bed 40, ammonia nitrogen and nitrate nitrogen are converted into nitrogen and discharged into the air. The denitrification bed 40 includes a denitrification tank 41, a denitrification filler 42, a support plate 43 for supporting the denitrification filler 42, an aeration pipe Ⅰ44, a cover plate Ⅰ45, a water inlet distributor Ⅰ46, and an air pipe Ⅰ47. The aeration pipe Ⅰ44 is arranged at the bottom of the denitrification tank 41. The denitrification filler area formed by the denitrification filler 42 and the support plate 43 is arranged in the denitrification tank 41 and arranged above the aeration pipe Ⅰ44. The cover plate Ⅰ45 is arranged above the denitrification tank 41. The water inlet is arranged at the top of the first denitrification tank 41 and connected to the water inlet distributor Ⅰ46. The air pipe Ⅰ47 connects the aeration pipe Ⅰ44 with the external air. The denitrification filler 42 is obtained by mixing 38wt% diatomaceous earth powder (average particle size of 30μm), 30wt% gypsum powder, 7wt% zeolite powder, 24wt% cement and 1wt% cement foaming agent, and then foaming, pulping, curing, crushing and screening. The average particle size is 30mm and the specific surface area is 8.5m 2 / g, bulk density 500kg / m 3 , adsorption capacity 63kg / m 3 , dry density 820kg / m 3 , cylinder pressure strength 4.5MPa, porosity 70%, water absorption 35%.

[0062] The adsorption dephosphorization bed 50 is a rectangular water tank body with a length, width and height of 10×10×4m. The filling thickness of the adsorption dephosphorization filler 52 is 3.5m, and the designed residence time is 3h. The adsorption dephosphorization bed 50 includes a dephosphorization tank 51, an adsorption dephosphorization filler 52, a support grid 53 for supporting the adsorption dephosphorization filler 52, an aeration pipe Ⅱ 54, a cover plate Ⅱ 55, a water inlet distributor Ⅱ 56 and an air pipe Ⅱ 57. The aeration pipe Ⅱ 54 is arranged at the bottom of the dephosphorization tank 51. The adsorption dephosphorization filler area formed by the adsorption dephosphorization filler 52 and the support grid 53 is arranged in the dephosphorization tank 51 and arranged above the aeration pipe Ⅱ 54. The cover plate Ⅱ 55 is arranged above the dephosphorization tank 51. The water inlet is arranged at the top of the first adsorption dephosphorization tank 51 and connected to the water inlet distributor Ⅱ 56. The air pipe Ⅱ 57 connects the aeration pipe Ⅱ 54 with the external air. The adsorption phosphorus removal filler 52 is obtained by mixing 22.0wt% gypsum powder, 32.0wt% calcium hydroxide powder, 30.0wt% ferric oxyhydroxide powder (average particle size is 30μm), 14.8wt% cement and 1.2wt% cement foaming agent, and then foaming, pulping, curing, crushing and screening. The average particle size is 20mm and the specific surface area is 8.5m 2 / g, bulk density 450kg / m 3 , adsorption capacity 25kg / m 3 , dry density 750kg / m 3 , cylinder pressure strength 3.5MPa, porosity 73%, water absorption 65%.

[0063] The inlet and outlet water indicators of eel farming tail water after denitrification and phosphorus removal by the above system are shown in Table 1:

[0064] Table 1 (Unit: mg / L)

[0065]

[0066]

[0067] (2) The eel farming tail water purification circulation method adopted in this embodiment is carried out in the above-mentioned eel farming tail water purification circulation system, and the treatment is carried out according to the following steps:

[0068] S1. Tailwater sedimentation: 3,000 tons / day of eel aquaculture wastewater is discharged into sedimentation tank 10. After passing through the sedimentation tank, solid particles such as feces and residual feed in the sewage are removed by sedimentation. On the other hand, the COD in the sewage is reduced by the action of anaerobic organisms in the sedimentation tank 10. Cr , BOD is oxidized into CO2, and organic phosphorus is converted into inorganic acid radicals;

[0069] S2. Hydrolysis and acidification: The supernatant (clean water) obtained from the sedimentation tank 10 flows into the hydrolysis and acidification tank 30, where the organic nitrogen in the tail water is converted into ammonia nitrogen and the organic phosphorus is converted into inorganic phosphate. The residence time of the hydrolysis and acidification is 4 hours;

[0070] S3. Denitrification in a denitrification bed: The tail water after hydrolysis and acidification flows into the denitrification bed 40, with a residence time of 2 hours, and the high concentration of nitrifying bacteria in the denitrification filler 42 oxidizes the ammonia nitrogen into nitrate nitrogen, and the high concentration of denitrifying bacteria (sulfur autotrophic bacteria) in the denitrification filler 42 reduces the nitrate nitrogen into nitrogen gas;

[0071] The inlet and outlet water indicators of eel farming tail water treated by denitrification bed 40 are shown in Table 2:

[0072] Table 2 (Unit: mg / L)

[0073] Serial number project Denitrification bed water inlet index Denitrification bed effluent index Removal rate (%) 1 SS 180.00 10.00 94.44 2 <![CDATA[COD Cr ]]> 15.00 12.00 20.00 3 Ammonia nitrogen (as N) 5.00 1.00 80.00 4 Total Nitrogen 10.00 3.00 70.00 5 Total Phosphorus 3.00 2.70 10.00

[0074] S4. Adsorption phosphorus removal: The tail water after denitrification in the denitrification bed 40 flows into the adsorption phosphorus removal bed 50 for a residence time of 3 hours. The phosphate in the tail water is adsorbed and removed by the adsorption phosphorus removal filler 52, thereby removing the total phosphorus in the water body and achieving the effluent standard.

[0075] The inlet and outlet indicators of eel breeding tail water treated by adsorption phosphorus removal bed 50 are shown in Table 3. The total phosphorus, total nitrogen, ammonia nitrogen and COD of the tail water are 0.10 mg / L, 2.50 mg / L and 0.80 mg / L, respectively. Cr The concentration of CO2 is 9.00mg / L, the SS is 8.00mg / L, and the pH is 7.8, which meet the discharge standards.

[0076] Table 3 (Unit: mg / L)

[0077] Serial number project Phosphorus removal bed water inlet index Phosphorus removal bed effluent index Removal rate (%) 1 SS 10.00 8.00 20.00 2 <![CDATA[COD Cr ]]> 12.00 9.00 25.00 3 Ammonia nitrogen (as N) 1.00 0.80 20.00 4 Total Nitrogen 3.00 2.50 16.67 5 Total Phosphorus 2.70 0.10 96.30

[0078] Example 2 Eel farming tail water denitrification and phosphorus removal system and method, with a daily processing capacity of 10,000 tons / day

[0079] (1) See Figures 1 to 3 The eel breeding tailwater denitrification and phosphorus removal system provided in this embodiment includes a sedimentation tank 10, a hydrolysis acidification tank 30, a denitrification bed 40, and an adsorption dephosphorization bed 50 which are connected in sequence. The water outlet of the sedimentation tank 10 is connected to the water inlet of the hydrolysis acidification tank 30, the water outlet of the hydrolysis acidification tank 30 is connected to the water inlet of the denitrification bed 40, the water outlet of the denitrification bed 40 is connected to the water inlet of the adsorption dephosphorization bed 50, and the water outlet of the adsorption dephosphorization bed 50 meets the discharge standards.

[0080] The sedimentation tank 10 is a two-round concrete casting tank body with a diameter of 13m, a depth of 6m, an effective water depth of 5m, and a designed retention time of 10h. It is used to collect and precipitate wastewater discharged from eel farming, and to precipitate and remove eel feces and residual feed in the wastewater; at the same time, the anaerobic microorganisms in the sedimentation tank are used to reduce the COD in the sewage. Cr , BOD5 is oxidized into carbon dioxide, organic nitrogen is hydrolyzed into ammonia nitrogen, nitrate ions are denitrified into nitrogen gas, and at the same time, a large amount of phosphorus-containing organic matter in the sewage is oxidized and decomposed into inorganic phosphates.

[0081] The hydrolysis acidification tank 30 is a rectangular water tank with a length, width and height of 20×18×5m and a retention time of 4h. In the hydrolysis acidification tank 30, organic nitrogen is converted into ammonia nitrogen, organic phosphorus is converted into inorganic phosphate, and part of the organic matter is oxidized and decomposed to be removed.

[0082] The denitrification bed 40 is a rectangular water tank body with a length, width and height of 25×21×3m. The filling thickness of the denitrification filler 42 is 2.5m, and the designed residence time is 2h. In the denitrification bed 40, ammonia nitrogen and nitrate nitrogen are converted into nitrogen and discharged into the air. The denitrification bed 40 includes a denitrification tank 41, a denitrification filler 42, a support plate 43 for supporting the denitrification filler 42, an aeration pipe Ⅰ44, a cover plate Ⅰ45, a water inlet distributor Ⅰ46, and an air pipe Ⅰ47. The aeration pipe Ⅰ44 is arranged at the bottom of the denitrification tank 41. The denitrification filler area formed by the denitrification filler 42 and the support plate 43 is arranged in the denitrification tank 41 and arranged above the aeration pipe Ⅰ44. The cover plate Ⅰ45 is arranged above the denitrification tank 41. The water inlet is arranged at the top of the first denitrification tank 41 and connected to the water inlet distributor Ⅰ46. The air pipe Ⅰ47 connects the aeration pipe Ⅰ44 with the external air. The denitrification filler 42 is obtained by mixing 22% gypsum powder, 32% calcium hydroxide powder, 30% iron oxyhydroxide powder, 14.8% cement and 1.2% cement foaming agent, and then foaming, pulping, curing, crushing and screening. The average particle size is 55 mm and the specific surface area is 8.5 m 2 / g, bulk density 700kg / m 3 , adsorption capacity 63kg / m 3 , dry density 820kg / m 3 , cylinder pressure strength 4.5MPa, porosity 70%, water absorption 35%.

[0083] The adsorption dephosphorization bed 50 is a rectangular water tank body with a length, width and height of 25×21×4m. The filling thickness of the adsorption dephosphorization filler 52 is 3.5m, and the designed residence time is 3h. The adsorption dephosphorization bed 50 includes a dephosphorization tank 51, an adsorption dephosphorization filler 52, a support grid 53 for supporting the adsorption dephosphorization filler 52, an aeration pipe II 54, a cover plate II 55, a water inlet distributor II 56 and an air pipe II 57. The aeration pipe II 54 is arranged at the bottom of the dephosphorization tank 51. The adsorption dephosphorization filler area formed by the adsorption dephosphorization filler 52 and the support grid 53 is arranged in the dephosphorization tank 51 and arranged above the aeration pipe II 54. The cover plate II 55 is arranged above the dephosphorization tank 51. The water inlet is arranged at the top of the first adsorption dephosphorization tank 51 and connected to the water inlet distributor II 56. The air pipe II 57 allows the aeration pipe II 54 to communicate with the external air. The adsorption phosphorus removal filler 52 is obtained by mixing 22% gypsum powder, 32% calcium hydroxide powder, 30% ferric oxyhydroxide powder, 14.8% cement and 1.2% cement foaming agent (average particle size is 45 μm) through foaming, pulping, curing, crushing and screening. The average particle size is 45 mm and the specific surface area is 8.5 m 2 / g, bulk density 550kg / m 3 , adsorption capacity 25kg / m 3 , dry density 750kg / m 3 , cylinder pressure strength 3.5MPa, porosity 73%, water absorption 65%.

[0084] The inlet and outlet water indicators of eel farming tail water after denitrification and phosphorus removal by the above system are shown in Table 4:

[0085] Table 4 (Unit: mg / L)

[0086] Serial number project Water inlet index Water output index Removal rate (%) 1 SS 175.00 8.00 94.43 2 <![CDATA[COD Cr ]]> 25.00 9.00 64.00 3 Ammonia nitrogen (as N) 5.00 0.70 86.00 4 Total Nitrogen 9.20 2.61 71.63 5 Total Phosphorus 1.80 0.08 95.55

[0087] (2) The eel farming tail water purification circulation method adopted in this embodiment is carried out in the above-mentioned eel farming tail water purification circulation system, and the treatment is carried out according to the following steps:

[0088] S1. Tailwater sedimentation: 10,000 tons / day of eel aquaculture wastewater is discharged into sedimentation tank 10. On the one hand, solid particles such as feces and residual feed in the wastewater are removed by sedimentation. On the other hand, the COD Cr , BOD is oxidized into CO2, and organic phosphorus is converted into inorganic acid radicals;

[0089] S2. Hydrolysis and acidification: The supernatant (clean water) obtained from the sedimentation tank 10 flows into the hydrolysis and acidification tank 30, where the organic nitrogen in the tail water is converted into ammonia nitrogen and the organic phosphorus is converted into inorganic phosphate. The residence time of the hydrolysis and acidification is 4 hours;

[0090] S3. Denitrification in a denitrification bed: The tail water after hydrolysis and acidification flows into the denitrification bed 40, with a residence time of 2 hours, and the high concentration of nitrifying bacteria in the denitrification filler 42 oxidizes the ammonia nitrogen into nitrate nitrogen, and the high concentration of denitrifying bacteria (sulfur autotrophic bacteria) in the denitrification filler 42 reduces the nitrate nitrogen into nitrogen gas;

[0091] The inlet and outlet water indicators of eel farming tail water treated by denitrification bed 40 are shown in Table 5:

[0092] Table 5 (Unit: mg / L)

[0093] Serial number project Denitrification bed water inlet index Denitrification bed effluent index Removal rate (%) 1 SS 175.00 10.00 94.29 2 <![CDATA[COD Cr ]]> 25.00 12.00 52.00 3 Ammonia nitrogen (as N) 5.00 1.00 80.00 4 Total Nitrogen 9.20 3.00 67.39 5 Total Phosphorus 1.80 1.71 5.00

[0094] S4. Adsorption phosphorus removal: The tail water after denitrification in the denitrification bed 40 flows into the adsorption phosphorus removal bed 50 for a residence time of 3 hours. The phosphate in the tail water is adsorbed and removed by the adsorption phosphorus removal filler 52, thereby removing the total phosphorus in the water body and achieving the effluent standard.

[0095] The inlet and outlet indicators of eel breeding tail water treated by adsorption phosphorus removal bed 50 are shown in Table 6. The total phosphorus, total nitrogen, ammonia nitrogen and COD of the tail water are 0.08 mg / L, 2.61 mg / L, 0.70 mg / L and 0.6 mg / L, respectively. Cr The concentration of CO2 is 9.00mg / L, the SS is 8.00mg / L, and the pH is 7.8, which meet the discharge standards.

[0096] Table 6 (Unit: mg / L)

[0097] Serial number project Phosphorus removal bed water inlet index Phosphorus removal bed effluent index Removal rate (%) 1 SS 10.00 8.00 20.00 2 <![CDATA[COD Cr ]]> 12.00 9.00 25.00 3 Ammonia nitrogen (as N) 1.00 0.70 30.00 4 Total Nitrogen 3.00 2.61 13.00 5 Total Phosphorus 1.71 0.08 95.29

[0098] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in the field can change, modify, replace and modify the above embodiments within the scope of the present application without departing from the principles and purpose of the present application.

Claims

1. A system for denitrification and phosphorus removal of eel breeding tail water, characterized in that: The system includes a sedimentation tank, a hydrolysis acidification tank, a denitrification bed, and an adsorption dephosphorization bed which are connected in sequence; The denitrification bed comprises at least one denitrification tank, a denitrification filler, a support plate for supporting the denitrification filler, an aeration pipe I and a cover plate I, wherein the aeration pipe I is arranged at the bottom of the denitrification tank, the denitrification filler area formed by the denitrification filler and the support plate is arranged in the denitrification tank and above the aeration pipe I, and the cover plate I is arranged above the denitrification tank; The adsorption phosphorus removal bed includes at least one phosphorus removal tank, an adsorption phosphorus removal filler, a support grid for supporting the adsorption phosphorus removal filler, an aeration pipe II and a cover plate II. The aeration pipe II is arranged at the bottom of the phosphorus removal tank. The adsorption phosphorus removal filler area formed by the adsorption phosphorus removal filler and the support grid is arranged in the phosphorus removal tank and above the aeration pipe II. The cover plate II is arranged above the phosphorus removal tank.

2. The eel farming tail water denitrification and phosphorus removal system according to claim 1, characterized in that: The denitrification filler is a porous expanded denitrification filler with an average particle size of 5 to 80 mm and a specific surface area of ​​8 to 10 m 2 / g, bulk density is 430~820kg / m 3 , dry density ≤820kg / m 3 , cylinder pressure strength ≥4.5MPa, porosity ≥70%, water absorption ≥35%.

3. The eel farming tail water denitrification and phosphorus removal system according to claim 1, characterized in that: The adsorption and phosphorus removal filler is a porous expanded adsorption and phosphorus removal filler with an average particle size of 3 to 50 mm and a specific surface area of ​​8 to 10 m 2 / g, bulk density is 410~600kg / m 3 , dry density ≤750kg / m 3 , cylinder pressure strength ≥3.5MPa, porosity ≥73%, water absorption ≥65%.

4. The eel farming tail water denitrification and phosphorus removal system according to claim 1, characterized in that: The sedimentation tank and the hydrolysis acidification tank are also provided with a filter, the water inlet of the filter is communicated with the water outlet of the sedimentation tank, and the water outlet of the filter is communicated with the water inlet of the hydrolysis acidification tank.

5. The eel farming tail water denitrification and phosphorus removal system according to claim 4, characterized in that: The filter is a rotary filter or a fiber disc filter.

6. The eel farming tail water denitrification and phosphorus removal system according to claim 4, characterized in that: The filter cloth pore size of the filter is 10-70 μm.

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