Eel breeding tail water purifying and recycling system

Abstract

The utility model belongs to the field of environmental protection and water resource recycling, and particularly relates to an eel breeding tail water purifying and recycling system. The eel breeding tail water purification and cyclic utilization system comprises a pretreatment device, a clear water purification and circulation device and a concentrated water treatment device, the pretreatment device comprises an anaerobic sedimentation tank and a filter I which are communicated in sequence, and the clear water purification and circulation device comprises a hydrolysis acidification tank, a denitrification bed I, an adsorption phosphorus removal bed I and a biological activation tank group which are communicated in sequence; the concentrated water treatment device comprises an air floatation tank, a filter II, a denitrification bed II and an adsorption dephosphorization bed II which are communicated in sequence, a clear water outlet of the filter I is communicated with a water inlet of the hydrolysis acidification tank, and a concentrated water outlet of the filter I is communicated with a water inlet of the air floatation tank. By the adoption of the system, accumulation of nitrogen, phosphorus and nitrite during cyclic utilization of the eel tail water can be reduced, the investment and operation cost is low, and actual application and popularization are facilitated.

Description

Technical Field

[0001] The present application belongs to the field of environmental protection and water resource recycling, and specifically relates to an eel farming tail water purification and recycling system. Background Art

[0002] During the eel farming process, about 20% of the stale water in the breeding pond will be discharged regularly every morning and evening, and then 10-20% of new water will be added. The 20% stale water discharged is called breeding tail water. The concentration of the main pollutants in the eel farming tail water is related to the growth period of the eels. Different species of eels have different growth rates and eat different amounts of bait, so the concentrations of the main pollutants in the tail water, such as ammonia nitrogen, total nitrogen, total phosphorus and COD, are also quite different. In addition, the concentration of the main pollutants in the eel farming tail water is also related to the season, breeding mode, and drainage method. If the eel farming tail water is discharged directly, its main pollutants and concentrations include COD Cr About 20-30 mg / L, BOD5 about 5-10 mg / L, ammonia nitrogen about 0.5-7 mg / L, nitrite 1.5-5 mg / L, total nitrogen about 3-20 mg / L, and total phosphorus about 1-3.5 mg / L. If eel aquaculture tailwater is finely filtered to separate it into clean water and concentrated water, and the clean water is biologically activated and then recycled to the aquaculture pond for fish farming, water resources can be saved and tailwater discharge can be reduced. However, since clean water contains not only ammonia nitrogen, total nitrogen, and total phosphorus, it also contains large amounts of nitrite, at concentrations of 1.5-5 mg / L. Nitrite is highly toxic to fish and shrimp. When the nitrite concentration in the water exceeds 0.2 mg / L, fish will lose their appetite, and excessively high nitrite concentrations can cause mass mortality. Therefore, to achieve the recycling of eel aquaculture tailwater, in addition to removing ammonia nitrogen, total nitrogen, and total phosphorus from the water, the efficient removal of nitrite is crucial.

[0003] Since eel farming requires a lot of water and requires frequent water changes, a clean water circulation method is currently often used (e.g., clean water is aerated and activated by bacteria and algae culture in a biological pool before being recycled into the farming pond) to save water. However, the lack of effective treatment of pollutants in the clean water recycling process leads to the accumulation of nitrogen, phosphorus, organic matter, and nitrite. The nitrogen and phosphorus concentrations in the circulating farming pond are too high, causing eel growth and metabolism disorders, slowing growth, and a significant decrease in production. It also causes farmed eel products to have an odor, affecting the quality of the eels. The main pollutants and concentrations in the water are COD, which accumulate in the circulation. Cr About 120-350mg / L, BOD5 about 40-150mg / L, ammonia nitrogen about 5-20mg / L, total nitrogen about 20-120mg / L, nitrite about 1.5-5mg / L, total phosphorus about 9-35mg / L. If they are discharged directly into the environment without treatment, it will cause COD in natural water bodies such as rivers and lakes. Cr, BOD5, nitrogen, and phosphorus concentrations exceed standards, leading to eutrophication of the water body. To address the problem of declining eel production and quality due to the accumulation of nitrogen, phosphorus, and nitrite in tail water recycling, and to meet the new local standards for aquaculture tail water, it is urgent to find an economical and practical device that can meet the new requirements for eel aquaculture tail water purification, recycling, and tail water discharge. Utility Model Content

[0004] The purpose of this application is to solve the problem of reduced eel production and quality due to the accumulation of nitrogen, phosphorus and nitrite in tail water recycling, and to provide an eel farming tail water purification and recycling system with low purification cost, simple operation and the ability to meet the requirements of eel farming tail water purification and recycling and tail water discharge standards.

[0005] Specifically, the eel breeding tail water purification and recycling system provided by the present application includes a pretreatment device, a clean water purification circulation device and a concentrated water treatment device. The pretreatment device includes a sedimentation tank and a filter I connected in sequence. The clean water purification circulation device includes a hydrolysis acidification tank, a denitrification bed I, an adsorption dephosphorization bed I and a biological activation tank group connected in sequence. The concentrated water treatment device includes a flotation tank, a filter II, a denitrification bed II and an adsorption dephosphorization bed II connected in sequence; the clean water outlet of the filter I is connected to the water inlet of the hydrolysis acidification tank, the concentrated water outlet of the filter I is connected to the water inlet of the flotation tank, the outlet of the biological activation tank group is connected to the eel breeding tank, and the outlet of the adsorption dephosphorization bed II is connected to the drain; the denitrification bed I and the denitrification bed II are used to remove nitrite, ammonia nitrogen and Nitrate, the denitrification bed I and the denitrification bed II each independently include a denitrification tank, a denitrification filler area, 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 includes a denitrification filler and a filler support I for supporting the denitrification filler, the denitrification filler area is arranged in the denitrification tank and above the aeration pipe I, and the cover plate I is located above the denitrification filler; the adsorption dephosphorization bed I and the adsorption dephosphorization bed II each independently include an adsorption dephosphorization tank, an adsorption dephosphorization filler area, an aeration pipe II and a cover plate II, the aeration pipe II is arranged at the bottom of the adsorption dephosphorization tank, the adsorption dephosphorization filler area includes an adsorption dephosphorization filler and a filler support II for supporting the adsorption dephosphorization filler, the adsorption dephosphorization filler area is arranged in the adsorption dephosphorization tank and above the aeration pipe II, and the cover plate II is located above the adsorption dephosphorization filler.

[0006] In some specific embodiments, the filter mesh of the filter I has a pore size of 5 to 20 μm.

[0007] In some specific embodiments, the filter screen of the filter II has an aperture of 200 to 600 meshes.

[0008] In some specific embodiments, the denitrification filler is a denitrification filler having a honeycomb porous structure and rich in nitrifying bacteria on the surface and denitrifying bacteria in the pores, 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%, adsorption capacity 60~65kg / m 3 .

[0009] In some specific embodiments, the adsorption phosphorus removal filler has a honeycomb porous structure, 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%, adsorption capacity 24~28kg / m 3 .

[0010] In some specific embodiments, the adsorption phosphorus removal filler is obtained by foaming, expanding, molding, crushing and screening gypsum powder, calcium hydroxide powder, iron oxyhydroxide powder, cement and cement foaming agent, and has a honeycomb porous structure.

[0011] In some specific embodiments, the biological activation pool group includes a biological activation pool and a photosynthetic bacteria proliferation pool, a chlorella proliferation pool, a diatom proliferation pool, a spirulina proliferation pool, and a Bacillus subtilis proliferation pool. The water inlet of the biological activation pool is connected to the water outlet of the adsorption and phosphorus removal bed 1, the outlet of the photosynthetic bacteria proliferation pool, the outlet of the chlorella proliferation pool, the outlet of the diatom proliferation pool, the outlet of the spirulina proliferation pool, and the outlet of the Bacillus subtilis proliferation pool, and the water outlet of the biological activation pool is connected to the eel breeding pond.

[0012] In some specific embodiments, the system includes a sludge treatment device, which includes a sludge thickening tank and a sludge dewatering machine that are interconnected. The sludge thickening tank is used to treat sludge from a sedimentation tank and / or a flotation tank.

[0013] In addition, when the eel farming tail water purification and recycling system provided by the present application is used to treat eel farming tail water, the treatment method includes the following steps:

[0014] S1 pre-treatment: First, the eel aquaculture tail water was collected in a sedimentation tank, precipitated in the sedimentation tank and separated into a supernatant and the bottom of the sewage containing solid particles, the supernatant enters the filter I filter diversion to obtain clean water and concentrated water;

[0015] S2. Clean water purification and recycling: The clean water obtained in step S1 is hydrolyzed and acidified and then enters denitrification bed I. The denitrification filler utilizes the adsorption effect to adsorb nitrite, ammonia nitrogen, and total nitrogen in the water onto the denitrification filler. The denitrification filler converts these nitrogen-containing substances into nitrogen gas, thereby removing ammonia nitrogen, nitrite, and total nitrogen from the water. The water treated in denitrification bed I enters adsorption dephosphorization bed I. Adsorption treatment with the adsorption dephosphorization filler reduces the total phosphorus concentration in the water. The clean water after denitrification and dephosphorization enters the bioactivation tank, where bacterial and algae culture fluid is added for bioactivation treatment. This produces recyclable effluent with a nitrite content of less than 0.1 mg / L and the removal of ammonia nitrogen, total nitrogen, and total phosphorus. The effluent is then circulated to the aquaculture pond for eel farming.

[0016] S3. Brine treatment: The brine obtained in step S1 is sequentially subjected to flotation treatment, microfiltration treatment, denitrification treatment in denitrification bed II, and dephosphorization treatment in adsorption dephosphorization bed II to obtain effluent that meets discharge standards.

[0017] In some specific implementations, in step S1 , the volume proportion of the clean water is 80-90%, and the volume proportion of the concentrated water is 10-20%.

[0018] In some specific embodiments, in step S2, the amount of the bacteria and algae culture solution added is 1 to 5‰ (v / v);

[0019] In some specific embodiments, in step S2, the bacteria and algae culture solution contains at least one of photosynthetic bacteria, Chlorella, diatoms, Spirulina and Bacillus.

[0020] In some specific embodiments, in step S2, the bioactivation treatment conditions include a time period of 18 to 36 hours.

[0021] In some specific embodiments, the denitrification filler in the denitrification bed is obtained by foaming and expanding diatomaceous earth powder, gypsum powder, zeolite powder, cement and cement foaming agent, followed by slurrying, coating, crushing, drying and screening.

[0022] In some specific embodiments, the average particle size of the diatomaceous earth powder is 20 to 50 μm.

[0023] In some specific embodiments, the adsorption dephosphorization filler in the adsorption dephosphorization bed is obtained by foaming and expanding gypsum powder, calcium hydroxide powder, iron oxyhydroxide powder, cement and cement foaming agent, slurrying, coating, crushing, drying and screening.

[0024] In some specific embodiments, the average particle size of the iron oxyhydroxide powder is 20 to 50 μm.

[0025] In some specific embodiments, the method further comprises step S4 of sludge treatment: subjecting the sludge from the sedimentation anaerobic treatment and the flotation treatment to gravity and filter press treatment to obtain dewatered sludge.

[0026] Compared with the prior art, this application has the following beneficial effects:

[0027] (1) In the system provided by this application, the eel farming tail water first enters the sedimentation tank, and solid particles such as feces and residual feed in the tail water are removed by sedimentation, and COD is reduced by the action of anaerobic organisms. Cr , BOD is oxidized into CO2, organic nitrogen is converted into ammonia nitrogen, and organic phosphorus is converted into inorganic phosphorus. The resulting supernatant enters the filter I, and is filtered and diverted to obtain clean water and concentrated water. Among them, the clean water enters the hydrolysis and acidification tank, the denitrification bed I, the adsorption and phosphorus removal bed I and the biological activation tank group in sequence. After hydrolysis and acidification and denitrification and phosphorus removal, nitrite ≤ 0.1 mg / L, ammonia nitrogen ≤ 1.0 mg / L, total nitrogen ≤ 3.0 mg / L, and total phosphorus ≤ 0.2 mg / L, which solves the problem of high nitrite during recycling aquaculture and the problem of high nitrogen and phosphorus concentrations caused by circulation, and can meet the water requirements for eel farming. After the water body is restored to activity through biological activation treatment in the biological activation pool, it is continued to be put into the eel farming pond for recycling; the concentrated water is subjected to flotation treatment, filtration treatment, denitrification treatment in the denitrification bed and phosphorus removal treatment in the adsorption and phosphorus removal bed, and can meet the effluent discharge standard. Therefore, the eel farming tail water purification and recycling system provided in this application can not only realize the recycling of tail water and reduce the accumulation of pollutants such as nitrogen, phosphorus, and nitrite during the circulation process, but also achieve the standard discharge of tail water, which has good application prospects and adaptability.

[0028] (2) When the present application is used to purify and recycle eel aquaculture tail water, the cost of treating clean water is ≤0.11 yuan / ton, and the cost of treating concentrated water is ≤0.35 yuan / ton. The treatment cost is low, and the investment cost of the denitrification and phosphorus removal method adopted in the present application is also relatively low, which is more conducive to practical promotion and application.

[0029] (3) When the present application is used to purify and recycle eel tail water, the entire process is controlled by PLC and artificial intelligence, which does not require special personnel to operate and manage, and the operation is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a process flow chart of an eel farming tail water purification and recycling system according to an embodiment of the present application.

[0031] Figure 2 It is a cross-sectional schematic diagram of a denitrification bed according to an embodiment of the present application.

[0032] Figure 3 It is a cross-sectional schematic diagram of an adsorption phosphorus removal bed according to an embodiment of the present application.

[0033] Reference numerals: 100, pre-treatment device; 110, sedimentation tank; 120, filter I; 200, clean water purification circulation device; 210, hydrolysis acidification tank; 220, denitrification bed I; 221, denitrification tank; 222, denitrification filler; 223, filler support I; 224, aeration pipe I; 225, cover plate I; 226, water distributor I; 227, air pipe I; 230, adsorption dephosphorization bed I; 2 31. Adsorption phosphorus removal tank; 232. Adsorption phosphorus removal filler; 233. Filler support II; 234. Aeration pipe II; 235. Cover plate II; 236. Inlet distributor II; 237. Air pipe II; 240. Biological activation tank group; 300. Brine treatment device; 310. Flotation tank; 320. Filter II; 330. Denitrification bed II; 340. Adsorption phosphorus removal bed II; 400. Sludge treatment device. DETAILED DESCRIPTION

[0034] The following is a detailed description of the specific embodiments of the present application. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present application and are not intended to limit the present application.

[0035] See also Figures 1 to 3 The eel breeding tail water purification and recycling system provided in the present application includes a pretreatment device 100, a clean water purification circulation device 200 and a concentrated water treatment device 300, wherein the pretreatment device 100 includes a sedimentation tank 110 and a filter I 120 connected in sequence, the clean water purification circulation device 200 includes a hydrolysis acidification tank 210, a denitrification bed I 220, an adsorption phosphorus removal bed I 230 and a biological activation tank group 240 connected in sequence, and the concentrated water treatment device 300 includes a flotation tank 310, a filter II 320, a denitrification bed II 330, and an adsorption phosphorus removal bed II 340 connected in sequence; the clean water outlet of the filter I 120 is connected to the water inlet of the hydrolysis acidification tank 210, the concentrated water outlet of the filter I 120 is connected to the water inlet of the flotation tank 310, the water outlet of the biological activation tank group 240 is connected to the eel breeding tank, and the adsorption phosphorus removal bed II 320 is connected to the water inlet of the flotation tank 310. The water outlet 340 is connected to the drain outlet.

[0036] See also Figure 2 and Figure 3The denitrification bed I 220 and the denitrification bed II 330 each independently include a denitrification tank 221, a denitrification filler area, an aeration pipe I 224 and a cover plate I 225, and are mainly used to remove nitrite, ammonia nitrogen and total nitrogen in the water; the adsorption dephosphorization bed I 230 and the adsorption dephosphorization bed II 340 each independently include an adsorption dephosphorization tank 231, an adsorption dephosphorization filler area, an aeration pipe II 234 and a cover plate II 235, and are mainly used to remove phosphorus in the water. The denitrification bed I 220 and the denitrification bed II 330 each independently include at least one denitrification tank 221. In this embodiment, the number of denitrification tanks 221 is 3. The water inlet is set at the top of the first denitrification tank 221 and is connected to the water inlet distributor I 226. The ammonia nitrogen and total nitrogen in the water are removed through the denitrification filler area, and then enter the subsequent phosphorus removal treatment through the water outlet at the bottom of the last denitrification tank 221. The effluent of the denitrification bed I 220 enters the adsorption phosphorus removal bed I, and the effluent of the denitrification bed II 330 enters the adsorption phosphorus removal bed II 340. The adsorption phosphorus removal bed I 230 and the adsorption phosphorus removal bed II 340 each independently include at least one adsorption phosphorus removal pool 231. In this embodiment, the number of adsorption phosphorus removal pools 231 is 3. The water inlet is arranged at the top of the first adsorption phosphorus removal pool 231 and is connected to the water inlet distributor II 236. Phosphorus in the water is removed through the adsorption phosphorus removal filler area, and then enters the subsequent treatment through the water outlet at the bottom of the last adsorption phosphorus removal pool 231. The effluent of the adsorption phosphorus removal bed I 230 enters the biological activation pool group 240, and the effluent of the adsorption phosphorus removal bed II 340 meets the discharge standards.

[0037] In some specific embodiments, the sedimentation tank 110 can be a circular or polygonal concrete casting tank 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 can be used to remove COD in the sewage. Cr , BOD5 is oxidized into CO2, organic nitrogen is hydrolyzed into ammonia nitrogen, and organic phosphorus is converted into inorganic phosphate. In addition, the outlet of the sedimentation tank 110 can be set as an overflow port, and the effluent flows out through the overflow port and enters the filter 1 120.

[0038] In some specific embodiments, the filter cloth of the filter 120 preferably has a pore size of 5 to 20 μm. The filtration function of the filter 120 can remove major fish pests such as Dactylorhiza and their eggs, Trichodina and their eggs, and Ichthyophthirius and their eggs, thereby preventing the occurrence of pests and diseases.

[0039] In some specific embodiments, the pore size of the filter screen of the filter II 320 is preferably 200-600 meshes. The filtering effect of the filter II 320 can further remove tiny solid particles in the concentrated water.

[0040] In some specific embodiments, the hydrolysis acidification tank 210 can be a circular or polygonal concrete tank with a depth of 4 to 6 meters, which is used to hydrolyze organic nitrogen in clean water into ammonia nitrogen, convert organic phosphorus into inorganic phosphate, and remove part of the COD in the clean water.

[0041] See also Figure 2 The aeration pipe I 224 is provided at the bottom of the denitrification tank 221. The denitrification filler area includes a denitrification filler 222 and a filler support I 223 for supporting the denitrification filler 222. The denitrification filler area is provided in the denitrification tank 221 and above the aeration pipe I 224. The cover plate I 225 is located above the denitrification filler 222. The denitrification filler 222 is a denitrification filler having a honeycomb porous structure and rich in nitrifying bacteria and denitrifying bacteria. It is preferably a denitrification filler having a honeycomb porous structure and rich in nitrifying bacteria on the surface and rich in denitrifying bacteria in the pores. The average particle size 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 430-820 kg / m 3 , dry density ≤820kg / m 3 , cylinder pressure strength ≥4.5MPa, porosity ≥70%, water absorption ≥35%, adsorption capacity is preferably 60~65kg / m 3 , ammonia nitrogen removal rate ≥ 95%, total nitrogen removal rate ≥ 90%. The above-mentioned denitrifying filler 222 is selected, which has a large number of honeycomb pores and is rich in nitrifying and denitrifying bacteria. Its porous structure is conducive to the simultaneous adsorption of nitrifying and denitrifying bacteria as well as ammonia nitrogen, nitrate nitrogen, nitrite and organic nutrients in the water body on the denitrifying filler 222, forming a local concentration, thereby quickly and efficiently removing ammonia nitrogen, nitrate nitrogen and nitrite from the water body, and reducing the concentrations of nitrite, ammonia nitrogen and total nitrogen in the water.

[0042] Preferably, when the surface of the denitrifying filler 222 is rich in nitrifying bacteria and the honeycomb pores are rich in denitrifying bacteria, it is more conducive to realizing the effects of nitrifying bacteria and denitrifying bacteria in different regions, that is, nitrifying bacteria are used on the surface of the denitrifying filler 222 to oxidize ammonia nitrogen into nitrite and / or nitrate nitrogen, and denitrifying bacteria are used in the pores of the denitrifying filler 222 to reduce nitrite and nitrate nitrogen in the water to nitrogen gas, which is more conducive to achieving efficient removal of ammonia nitrogen, nitrate nitrogen and nitrite.

[0043] Furthermore, an air pipe I 227 is provided in the denitrification tank 221 , and the air pipe I 227 connects the aeration pipe I 224 to the external air.

[0044] See also Figure 3The aeration pipe II 234 is provided at the bottom of the adsorption dephosphorization tank 231. The adsorption dephosphorization filler area includes an adsorption dephosphorization filler 232 and a filler support II 233 for supporting the adsorption dephosphorization filler 232. The adsorption dephosphorization filler area is provided in the adsorption dephosphorization tank 231 and above the aeration pipe II 234. The cover plate II 235 is located above the adsorption dephosphorization filler 232. The adsorption dephosphorization filler 232 has a honeycomb porous structure, an average particle size of preferably 3 to 50 mm, and a specific surface area of ​​preferably 8 to 10 m 2 / g, and the bulk density is preferably 410-600 kg / m 3 , dry density ≤750kg / m 3 , cylinder pressure strength ≥3.5MPa, porosity ≥73%, water absorption ≥65%, adsorption capacity is preferably 24-28kg / m 3 The phosphorus removal rate is ≥96%. The above-mentioned adsorption phosphorus removal filler 232 is selected, which has a honeycomb porous structure, which is conducive to adsorbing phosphate in water on the filler surface, thereby reducing the total phosphorus concentration in the water.

[0045] Furthermore, an air pipe II 237 is provided in the adsorption dephosphorization tank 231 , and the air pipe II 237 connects the aeration pipe II 234 to the external air.

[0046] In addition, the adsorption dephosphorization filler 232 can be replaced with a new filler after being saturated with adsorption, or it can be regenerated to desorb the adsorbed phosphorus and then continued to be used. The regeneration method of the adsorption dephosphorization filler 232 can be alkaline washing regeneration and / or acid washing regeneration.

[0047] In some specific embodiments, the biological activation pool group 240 includes a biological activation pool and a photosynthetic bacteria growth pool, a chlorella growth pool, a diatom growth pool, a spirulina growth pool, and a bacillus growth pool. The water inlet of the biological activation pool is connected to the water outlet of the adsorption phosphorus removal bed 1 230, the outlet of the photosynthetic bacteria growth pool, the outlet of the chlorella growth pool, the outlet of the diatom growth pool, the outlet of the spirulina growth pool, and the outlet of the bacillus growth pool. The water outlet of the biological activation pool is connected to the eel breeding pool. After denitrification and phosphorus removal, the clean water enters the biological activation pool and is mixed and cultured with at least one of the photosynthetic bacteria, chlorella, diatom, spirulina, and bacillus, thereby restoring the water body to meet the water requirements of eel breeding and realizing the recycling of eel breeding tail water. Among them, the active substances such as subtilisin, polymyxin, nystatin, and gramicidin produced during the proliferation of Bacillus have a significant inhibitory effect on pathogenic bacteria in fish; and Bacillus can stimulate the growth and development of eel immune organs, activate T and B lymphocytes, increase immunoglobulin and antibody levels, enhance cellular immunity and humoral immunity, and improve group immunity; Bacillus subtilis can also synthesize VB1, VB2, VB6 and niacin and other B vitamins, and increase the activity of interferon and macrophages in eels; Bacillus can adsorb on the hyphae of pathogenic fungi and grow together with the hyphae. During the growth process, lytic substances will be produced, thereby dissolving the mycelium.

[0048] In some specific embodiments, the system includes a sludge treatment device 400, which includes a sludge thickening tank and a sludge dewatering machine interconnected with each other. The sludge thickening tank is used to collect and process sludge from the anaerobic sedimentation tank 110 and / or the flotation tank 310. The concentrated sludge enters the sludge dewatering machine for dewatering, and the dewatered sludge can be regularly transported. The sludge dewatering machine can be a sludge dewatering machine commonly used in wastewater treatment, including but not limited to at least one of a plate and frame sludge dewatering machine, a belt sludge dewatering machine, a sludge centrifugal dewatering machine, a pile sludge dewatering machine, and a spiral sludge dewatering machine.

[0049] In addition, when the eel farming tail water purification and recycling system provided by the present application is used to treat eel farming tail water, the treatment method preferably includes the following steps:

[0050] S1. Pre-treatment: The eel farming tailwater flows into the sedimentation tank 110, where solid particles such as feces and residual feed are removed from the tailwater through sedimentation, and COD is reduced by anaerobic microorganisms. Cr , BOD is oxidized into CO2, organic nitrogen is converted into ammonia nitrogen, and organic phosphorus is converted into inorganic phosphorus. The resulting supernatant is then filtered and split through a filter I120 to obtain 80-90% clean water and 10-20% concentrated water by volume;

[0051] S2. Clean water purification and recycling treatment:

[0052] ① Hydrolysis and acidification treatment: The clean water obtained in step S1 flows into the hydrolysis and acidification tank 210, where the organic nitrogen in the clean water is converted into ammonia nitrogen, and the organic phosphorus is converted into inorganic phosphate, while COD is removed from the clean water;

[0053] ② Denitrification treatment: The clean water after hydrolysis and acidification flows into the denitrification bed I 220. The nitrogen-containing substances such as nitrite, ammonia nitrogen, and total nitrogen in the water are adsorbed on the denitrification filler by the adsorption effect of the denitrification filler. The denitrification filler then converts the nitrogen-containing substances into nitrogen gas, thereby removing ammonia nitrogen, nitrite and total nitrogen in the water. After treatment in the denitrification bed I 220, the ammonia nitrogen in the water is reduced to below 1.0 mg / L, the nitrite in the water is reduced to below 0.1 mg / L, and the total nitrogen in the water is reduced to below 3.0 mg / L.

[0054] ③ Phosphorus removal treatment: The water body after denitrification enters the adsorption phosphorus removal bed I 230. The adsorption phosphorus removal filler 232 of the adsorption phosphorus removal bed I 230 adsorbs and removes inorganic phosphate in the water, reducing the total phosphorus in the water body to below 0.2 mg / L;

[0055] ④ Biological activation treatment: The clean water after phosphorus removal flows into the biological activation pool, where bacteria and algae culture fluid is added for biological activation treatment to obtain recyclable effluent, which is circulated to the breeding pond for eel breeding;

[0056] S3. Brine treatment:

[0057] Ⅰ Flotation treatment: The concentrated water obtained in step S1 flows into the flotation tank 310, where flocculants and coagulants are added to remove phosphorus and organic matter from the concentrated water;

[0058] II. Filtration: The concentrated water after flotation treatment flows into filter II320 to remove solid particles in the water;

[0059] III. Denitrification treatment: The filtered concentrated water flows into the denitrification bed II 330 for denitrification treatment, and after the nitrogen is discharged, it enters the adsorption dephosphorization bed II 340;

[0060] IV. Phosphorus removal: The concentrated water after denitrification treatment flows into the adsorption phosphorus removal bed II340. The total phosphorus in the water is adsorbed and removed by the special phosphorus adsorption filler, and the effluent meets the discharge standards.

[0061] In a preferred embodiment, in the denitrification treatment of step S2-②, when the denitrification filler 222 is a denitrification filler having a honeycomb porous structure and rich in nitrifying bacteria on the surface and denitrifying bacteria in the pores, the clean water after hydrolysis and acidification flows into the denitrification bed I 220, and the nitrifying bacteria on the surface of the denitrification filler 222 oxidizes the ammonia nitrogen into nitrite and / or nitrate nitrogen, and then the denitrifying bacteria in the pores of the denitrification filler 222 reduce the nitrate nitrogen and nitrite to nitrogen gas, thereby achieving the removal of ammonia nitrogen, nitrite and total nitrogen in the water body.

[0062] In some specific embodiments, in step S1, the precipitation and anaerobic treatment time is preferably 5 to 8 hours.

[0063] In some specific embodiments, in step S1, the volume proportion of the clean water is preferably 80-90%, such as 80%, 82%, 85%, 88%, 90% or any value therebetween; the volume proportion of the concentrated water is 10-20%, such as 10%, 12%, 15%, 18%, 20% or any value therebetween.

[0064] In some specific embodiments, in step S2, the amount of the bacterial and algal culture solution added is 1 to 5‰ (v / v), such as 1‰ (v / v), 2‰ (v / v), 3‰ (v / v), 4‰ (v / v), 5‰ (v / v) or any value therebetween. At this point, the bacterial concentration in the water sample is appropriate, which is conducive to subsequent cultivation and achieves an ideal bioactivation effect. The conditions for the bioactivation treatment include a time period of preferably 18 to 36 hours, such as 18 hours, 20 hours, 25 hours, 30 hours, 32 hours, 36 hours or any value therebetween.

[0065] In some specific embodiments, the denitrification filler in the denitrification bed can be various existing denitrification fillers, or it can be a denitrification filler obtained by foaming and expanding diatomaceous earth powder, gypsum powder, zeolite powder, cement and cement foaming agent, pulping, coating, crushing, drying and screening. Wherein, the average particle size of the diatomaceous earth powder is preferably 20 to 50 μm. The denitrification filler prepared by the above method not only has a honeycomb porous structure, which is conducive 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 its rapid reproduction. At the same time, because 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 filler surface, forming a local concentration, which is more conducive to the rapid and efficient removal of ammonia nitrogen, nitrate nitrogen and total nitrogen in the water.

[0066] Furthermore, the average particle size of the denitrification filler is preferably 5 to 80 mm, and the specific surface area is preferably 8 to 10 m 2 / g, and the adsorption capacity is preferably 60-65 kg / m 3 , bulk density 430~820kg / m 3 , dry density ≤820kg / m 3 , cylinder pressure strength ≥4.5MPa, porosity ≥70%, water absorption rate ≥35%, ammonia nitrogen removal rate ≥95%, total nitrogen removal rate ≥90%.

[0067] In some specific embodiments, the adsorption dephosphorization filler in the adsorption dephosphorization bed can be various existing fillers, or can be an adsorption dephosphorization filler obtained by foaming and expanding gypsum powder, calcium hydroxide powder, iron oxyhydroxide powder, cement, and cement foaming agent, pulping, coating, crushing, drying, and screening. The adsorption dephosphorization filler prepared by the above method not only has a honeycomb porous structure, but also has calcium sulfate on the surface of the filler that is slightly soluble in water (solubility 0.2g) to form a locally high-concentration calcium ion layer (multiple electric layers), which reacts with phosphate in the water to form calcium phosphate and adsorbs on the filler surface. The reaction formula is shown below, which is more conducive to quickly and efficiently reducing the total phosphorus concentration in the water.

[0068] CaSO4·2H2O→Ca 2+ +SO4 2- +2H2O

[0069] 3Ca 2+ +2PO4 3- →Ca3(PO4)2

[0070] Furthermore, the average particle size of the adsorption phosphorus removal filler is 3 to 50 mm, and the specific surface area is preferably 8 to 10 m 2 / g, and the adsorption capacity is preferably 20 to 30 kg / m 3 The bulk density is preferably 410 to 600 kg / m 3 , dry density ≤750kg / m 3 , cylinder pressure strength ≥3.5MPa, porosity ≥73%, water absorption rate ≥65%, phosphorus removal rate ≥96%.

[0071] In some specific embodiments, in step S3, the flotation treatment can be to add flocculants and coagulants to the concentrated water, and remove 90-98% of phosphorus and 40-75% of COD in the concentrated water by flotation. Cr .

[0072] Furthermore, the flocculant can be a conventional choice in the art, specifically but not limited to: at least one of ferrous sulfate, ferrous chloride, basic aluminum chloride, calcium chloride, sodium polyacrylate, polyacrylamide, polystyrene sulfonate and polyethylene oxide; its addition amount can be selected according to the actual sewage treatment volume, preferably 5 to 200 mg / L, such as 5 mg / L, 20 mg / L, 50 mg / L, 80 mg / L, 100 mg / L, 120 mg / L, 150 mg / L, 200 mg / L or any value therebetween. The coagulant aid can be a conventional choice in the art, specifically but not limited to polyacrylamide; its addition amount can be selected according to the actual sewage treatment volume, preferably 0.1 to 20 mg / L, such as 0.1 mg / L, 0.5 mg / L, 1 mg / L, 5 mg / L, 10 mg / L, 15 mg / L, 20 mg / L or any value therebetween.

[0073] In some specific embodiments, the method may further include step S4 of sludge treatment: subjecting the sludge obtained from the sedimentation anaerobic treatment and the flotation treatment to gravity and filter press treatment to obtain dewatered sludge.

[0074] The following will describe in detail the eel farming tail water purification and recycling system and method provided by the present application through specific embodiments.

[0075] Example 1 3000 tons / day eel farming tail water purification and recycling system and method,

[0076] (1) See Figures 1 to 3 The eel farming tailwater purification and recycling system provided in this embodiment includes a pre-treatment device 100, a clean water purification and recycling device 200, and a concentrated water treatment device 300, wherein:

[0077] The pre-treatment device 100 includes a sedimentation tank 110 and a filter 1 120 connected in sequence. The anaerobic sedimentation tank 110 is a circular concrete tank with a diameter of 15m, a depth of 6m, and a designed retention time of 8h. It is used to collect and precipitate the tail water discharged from eel farming, remove eel feces and residual feed in the wastewater, and use the anaerobic microorganisms in the anaerobic sedimentation tank 110 to reduce the COD in the tail water. Cr , oxidizes BOD5 into CO2, hydrolyzes organic nitrogen into ammonia nitrogen, and converts large amounts of phosphorus-containing organic matter in the water into inorganic phosphates. Sedimentation tank 110 is equipped with an overflow port, and the water inlet of filter I 120 is connected to the overflow port of sedimentation tank 110. Filter I 120 is a fiber rotary disc filter with a filter cloth pore size of 5μm. While removing the main fish pests in the water—Dactylus anguilla and its eggs, Trichodina and its eggs, and Ichthyophthirius spp.—it also filters and diverts the tailwater into 80% clean water and 20% concentrated water by volume.

[0078] Clean water purification circulation device 200 includes a hydrolysis and acidification tank 210, a denitrification bed 1 220, an adsorption and phosphorus removal bed 1 230, and a biological activation tank group 240, which are connected in sequence. The water inlet of hydrolysis and acidification tank 210 is connected to the clean water outlet of filter 1 120, and the water inlet of hydrolysis and acidification tank 210 is also connected to the water inlet of denitrification bed 1 220. Hydrolysis and acidification tank 210 is a circular concrete tank with a diameter of 9 meters and a depth of 4 meters. The designed residence time is 2 hours.

[0079] The denitrification bed I 220 includes a denitrification tank 221, a denitrification filler 222, a filler support I 223, an aeration pipe I 224, a water inlet distributor I 226, a cover plate I 225, and an air pipe I 227. The outlet of the denitrification bed I 220 is connected to the water inlet of the adsorption dephosphorization bed I 230. The denitrification bed I 220 is a square concrete casting tank body with a geometric size of 10×3×4m. There are three denitrification tanks 221. The water inlet is set at the top of the first denitrification tank 221 and connected to the water inlet distributor I 226. The aeration pipe I 224 is set at the bottom of the denitrification tank 221. The denitrification filler area formed by the denitrification filler 222 and the filler support I 223 is set in the denitrification tank 221 and above the aeration pipe I 224. The cover plate I 225 is located above the denitrification filler 222. The air pipe I 2 27 makes the aeration pipe I 224 communicate with the outside air; the denitrification filler 222 is made of 38wt% diatomaceous earth powder (average particle size of 30μm), 30wt% gypsum powder, 7wt% zeolite powder, 24wt% cement and 1wt% cement foaming agent through foaming, pulping, coating, crushing, drying and screening. It has a honeycomb porous structure and is rich in nitrifying bacteria on the surface and denitrifying bacteria in the pores. The average particle size is 30mm and the specific surface area is 8.5m 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 rate 35%.

[0080] The adsorption phosphorus removal bed I 230 includes an adsorption phosphorus removal tank 231, an adsorption phosphorus removal filler 232, a filler support II 233, an aeration pipe II 234, an inlet distributor II 236, a cover II 235, and an air pipe II 237. The outlet of the adsorption phosphorus removal bed I 230 is connected to the inlet of the biological activation tank. The adsorption phosphorus removal bed I 230 is a square concrete casting tank body with geometric dimensions of 10×3×4m. There are three adsorption phosphorus removal tanks 231. The water inlet is set at the top of the first adsorption phosphorus removal tank 231 and connected to the inlet distributor II 236. The aeration pipe II 234 is set at the bottom of the adsorption phosphorus removal tank 231. The adsorption phosphorus removal filler area formed by the adsorption phosphorus removal filler 232 and the filler support II 233 is set in the adsorption phosphorus removal tank 231 and above the aeration pipe II 234. The cover II 235 is located above the adsorption dephosphorization filler 232, and the air pipe I 237 connects the aeration pipe I 234 to the outside air; the adsorption dephosphorization filler 232 is made of 22wt% gypsum powder, 32wt% calcium hydroxide powder, 30wt% ferric oxyhydroxide powder, 14.8wt% cement and 1.2wt% cement foaming agent through foaming, pulping, coating, crushing, drying and screening, with an average particle size of 20mm and a specific surface area of ​​8.5m 2 / g, bulk density 550kg / m 3 , adsorption capacity 25kg / m 3 , dry density 750kg / m 3 , cylinder pressure strength 3.5MPa, porosity 75%, water absorption rate 65%.

[0081] The biological activation pool group 240 includes a biological activation pool and a photosynthetic bacteria proliferation pool, a chlorella proliferation pool, a diatom proliferation pool, a spirulina proliferation pool, and a bacillus proliferation pool. The water inlet of the biological activation pool is connected to the outlet of the photosynthetic bacteria proliferation pool, the outlet of the chlorella proliferation pool, the outlet of the diatom proliferation pool, the outlet of the spirulina proliferation pool, and the outlet of the bacillus proliferation pool. The water inlet of the biological activation pool is connected to the eel breeding pool. Photosynthetic bacteria, chlorella, diatom, spirulina and Bacillus subtilis are added to the biological activation pool through a water pump to activate the clean water to meet the activity requirements of eel breeding water.

[0082] The concentrated water treatment device 300 includes an air flotation tank 310, a filter II 320, a denitrification bed II 330, and an adsorption dephosphorization bed II 340 which are connected in sequence. The water inlet of the flotation tank 310 is connected to the concentrated water outlet of the filter I1 20, and the water outlet of the flotation tank 310 is connected to the water inlet of the filter II 320. The water outlet of the filter II 320 is connected to the water inlet of the denitrification bed II 330. The filter II 320 is a microfiltration machine with a filter mesh aperture of 400 mesh. The water outlet of the denitrification bed II 330 is connected to the water inlet of the adsorption dephosphorization bed II 340. The denitrification bed II 330 is the same as the denitrification bed I 220, except that the geometric dimensions are 15×5×5m and there are four of them. The adsorption dephosphorization bed II 340 is the same as the adsorption dephosphorization bed I 230, except that the geometric dimensions are 15×5×5m and there are four of them. The effluent from the adsorption dephosphorization bed II 340 meets the discharge standards.

[0083] The sludge treatment device includes a sludge thickening tank and a sludge dewatering machine which are interconnected. The sludge thickening tank is used to treat the sludge from the anaerobic sedimentation tank and / or the flotation tank. The concentrated sludge enters the sludge dewatering machine for dehydration treatment.

[0084] (2) The eel farming tail water purification and recycling method adopted in this embodiment is carried out in the above-mentioned eel farming tail water purification and recycling system, and specifically includes the following steps:

[0085] S1. Pretreatment: 3,000 tons / day of eel aquaculture tailwater is discharged into sedimentation tank 110 for sedimentation. Sedimentation in sedimentation tank 110 separates the wastewater into a supernatant and a bottom portion containing solid fecal particles. The supernatant enters filter I 120 for filtration and diversion, yielding 80% clean water (2,400 tons / day) and 20% concentrated water (600 tons / day). The bottom portion containing solid fecal particles is collected in a sludge thickening tank.

[0086] S2. Clean water purification and recycling treatment:

[0087] ① Hydrolysis and acidification treatment: The clean water obtained in step S1 enters the hydrolysis and acidification tank 210 for hydrolysis and acidification treatment to convert organic nitrogen in the clean water into ammonia nitrogen and organic phosphorus into inorganic phosphate, while removing part of the COD in the clean water;

[0088] ② Denitrification treatment: The clean water after hydrolysis and acidification flows into the denitrification bed I 220. The nitrifying bacteria on the surface of the denitrification filler 222 oxidize the ammonia nitrogen into nitrite and / or nitrate nitrogen. The denitrifying bacteria in the pores of the denitrification filler 222 then reduce the nitrate nitrogen and nitrite to nitrogen gas, thereby removing ammonia nitrogen, nitrite and total nitrogen from the water.

[0089] ③ Phosphorus removal treatment: The water body after denitrification enters the adsorption phosphorus removal bed I 230, and the inorganic phosphate in the water is adsorbed and removed by the adsorption phosphorus removal filler 232 of the adsorption phosphorus removal bed I 230;

[0090] ④ Biological activation treatment: The clean water after phosphorus removal is mixed and cultured with photosynthetic bacteria, chlorella, diatoms, spirulina culture solution and bacillus culture solution in the biological activation pool for 24 hours to restore the water activity and obtain recyclable effluent. The water quality of the recycle water is shown in Table 1: After hydrolysis, acidification, denitrification, phosphorus removal and biological activation treatment, the ammonia nitrogen in the eel breeding tail water is reduced from ≦10mg / L to ≦1mg / L, with a removal rate of more than 90%, the nitrite in the water is reduced from ≦5mg / L to ≦0.1mg / L, with a removal rate of more than 95%, the total nitrogen in the water is reduced from ≦15mg / L to ≦3mg / L, with a removal rate of 80%, and the total phosphorus in the water is reduced from ≦3mg / L to ≦0.2mg / L;

[0091] S3. Concentrate treatment: The concentrated water obtained in step S1 enters the flotation tank 310, where flocculants and coagulants are added to remove 90-98% of phosphorus and 40-75% of COD in the concentrated water by flotation and slag removal. Cr The concentrated water after flotation enters filter II, where it further removes tiny solid particles in the wastewater and then enters denitrification bed II 330 for denitrification. The denitrified concentrated water enters adsorption phosphorus removal bed II 340, where the total phosphorus in the water is adsorbed by a special phosphorus adsorption filler. The water quality of the discharged water is shown in Table 2, with the total phosphorus concentration of the effluent being ≤0.5 mg / L, total nitrogen ≤5 mg / L, ammonia nitrogen ≤1 mg / L, pH 6-9, COD ≤40 mg / L, and suspended solids ≤45 mg / L.

[0092] S4. Sludge treatment: The sludge from the sedimentation anaerobic treatment and flotation treatment is subjected to gravity and filter press treatment to obtain dewatered sludge.

[0093] In this embodiment, the inlet index, the outlet index of the circulating water and the outlet index of the discharged water of the eel farming tail water to be treated are shown in Table 1 and Table 2.

[0094] Table 1 Inlet and outlet indicators of circulating water for eel aquaculture tail water (unit: mg / L)

[0095] Serial number project Water inlet index Circulating water indicators Removal rate (%) 1 SS 200.0 10.0 95.00 2 nitrite 5.0 0.1 98.00 3 <![CDATA[COD Cr ]]> 40.0 10.0 64.28 4 Ammonia nitrogen (as N) 9.9 0.8 91.92 5 Total nitrogen (as N) 15.0 3.0 80.00 6 Total phosphorus (P) 3.0 0.2 93.33 7 Insects and eggs (pieces) 150 0 100.00 8 pH 6～9 6～9 -

[0096] Table 2 Inlet and outlet indicators of eel aquaculture tail water (unit: mg / L)

[0097] Serial number project Water inlet index Discharge water indicators Removal rate (%) 1 SS 200.0 10.0 95.00 2 <![CDATA[COD Cr ]]> 40.0 10.0 75.00 3 Ammonia nitrogen (as N) 9.9 0.8 91.92 4 Total nitrogen (as N) 15.0 3.0 80.00 5 Total phosphorus (P) 3.0 0.5 83.33 6 Insects and eggs (pieces) 1300 0 100.00 7 pH 6～9 6～9 -

[0098] Example 2 10,000 tons / day eel aquaculture tail water purification and recycling system and method

[0099] (1) The eel aquaculture tail water purification and recycling system provided in this embodiment includes a pre-treatment device 100, a clean water purification and circulation device 200, and a concentrated water treatment device 300, wherein:

[0100] The pre-treatment device 100 includes an anaerobic sedimentation tank 110 and a filter 1120 connected in sequence. The anaerobic sedimentation tank 110 includes two circular concrete casting tanks with a diameter of 23m, a depth of 6.5m, an effective water depth of 6m, and a designed retention time of 6h. It is used to collect and precipitate the tail water discharged from eel farming, precipitate and remove eel feces and residual feed in the wastewater, and use the anaerobic microorganisms in the sedimentation tank 110 to reduce the COD in the tail water. Cr , oxidizes BOD5 into CO2, hydrolyzes organic nitrogen into ammonia nitrogen, and converts large amounts of phosphorus-containing organic matter in the water into inorganic phosphates. Sedimentation tank 110 is equipped with an overflow port, and the water inlet of filter 1120 is connected to the overflow port of sedimentation tank 110. Filter 1120 is a fiber rotary disc filter with a filter cloth pore size of 10μm. While removing the main fish pests in the water—Dactylus anguilla and its eggs, Trichodina and its eggs, and Ichthyophthirius spp.—it also filters and diverts the tailwater into 90% clean water and 10% concentrated water by volume.

[0101] Clean water purification circulation device 200 includes a hydrolysis and acidification tank 210, a denitrification bed 1 220, an adsorption and phosphorus removal bed 1 230, and a biological activation tank group 240, which are connected in sequence. The water inlet of hydrolysis and acidification tank 210 is connected to the clean water outlet of filter 1 120, and the water inlet of hydrolysis and acidification tank 210 is also connected to the water inlet of denitrification bed 1 220. Hydrolysis and acidification tank 210 is a circular concrete tank with a diameter of 13 meters, a depth of 5.5 meters, an effective water depth of 5 meters, and a designed treatment time of 1.5 hours.

[0102] The denitrification bed I 220 includes a denitrification tank 221, a denitrification filler 222, a filler support I 223, an aeration pipe I 224, a water inlet distributor I 226, a cover plate I 225, and an air pipe I 227. The outlet of the denitrification bed I 220 is connected to the water inlet of the adsorption dephosphorization bed I 230. The denitrification bed I 220 is a square concrete casting tank body with geometric dimensions of 15×5×4m. There are four denitrification tanks 221. The water inlet is set at the top of the first denitrification tank 221 and connected to the water inlet distributor I 226. The aeration pipe I 224 is set at the bottom of the denitrification tank 221. The denitrification filler area formed by the denitrification filler 222 and the filler support I 223 is set in the denitrification tank 221 and above the aeration pipe I 224. The cover plate I 225 is located above the denitrification filler 222. The air pipe I 227 makes the aeration pipe I 224 communicate with the outside air; the denitrification filler 222 is obtained by foaming, pulping, coating, crushing, drying and screening 38wt% diatomaceous earth powder (average particle size of 50μm), 30wt% gypsum powder, 7wt% zeolite powder, 24wt% cement and 1wt% cement foaming agent, and has a honeycomb porous structure and is rich in nitrifying bacteria on the surface and denitrifying bacteria in the pores. The average particle size is 55mm and the specific surface area is 8.5m 2 / g, bulk density is 500kg / m 3 , adsorption capacity is 63kg / m 3 , dry density 820kg / m 3 , cylinder pressure strength 4.5MPa, porosity 70%, water absorption rate 35%.

[0103] The adsorption phosphorus removal bed I 230 includes an adsorption phosphorus removal tank 231, an adsorption phosphorus removal filler 232, a filler support II 233, an aeration pipe II 234, an inlet distributor II 236, a cover II 235, and an air pipe II 237. The outlet of the adsorption phosphorus removal bed I 230 is connected to the inlet of the biological activation tank. The adsorption phosphorus removal bed I 230 is a square concrete casting tank body with geometric dimensions of 15×5×4m. There are four adsorption phosphorus removal tanks 231. The water inlet is set at the top of the first adsorption phosphorus removal tank 231 and connected to the inlet distributor II 236. The aeration pipe II 234 is set at the bottom of the adsorption phosphorus removal tank 231. The adsorption phosphorus removal filler area formed by the adsorption phosphorus removal filler 232 and the filler support II 233 is set in the adsorption phosphorus removal tank 231 and above the aeration pipe II 234. The cover II 235 is located above the adsorption dephosphorization filler 232, and the air pipe I 237 connects the aeration pipe I 234 to the outside air; the adsorption dephosphorization filler 232 is made of 22.0wt% gypsum powder, 32.0wt% calcium hydroxide powder, 30.0wt% ferric oxyhydroxide powder, 14.8wt% cement and 1.2wt% cement foaming agent through foaming, pulping, coating, crushing, drying and screening, with an average particle size of 45μm and a specific surface area of ​​8.5m 2 / g, bulk density is 450kg / m 3 , adsorption capacity is 25kg / m 3 , dry density 750kg / m 3 , cylinder pressure strength 3.5MPa, porosity 75%, water absorption rate 65%.

[0104] The biological activation pool group 240 includes a biological activation pool and a photosynthetic bacteria proliferation pool, a chlorella proliferation pool, a diatom proliferation pool, a spirulina proliferation pool, and a bacillus proliferation pool. The water inlet of the biological activation pool is connected to the outlet of the photosynthetic bacteria proliferation pool, the outlet of the chlorella proliferation pool, the outlet of the diatom proliferation pool, the outlet of the spirulina proliferation pool, and the outlet of the bacillus proliferation pool. The water inlet of the biological activation pool is connected to the eel breeding pool. Photosynthetic bacteria, chlorella, diatom, spirulina and Bacillus subtilis are added to the biological activation pool through a water pump to activate the clean water to meet the activity requirements of eel breeding water.

[0105] The concentrated water treatment device 300 includes an air flotation tank 310, a filter II 320, a denitrification bed II 330, and an adsorption dephosphorization bed II 340 which are connected in sequence. The water inlet of the flotation tank 310 is connected to the concentrated water outlet of the filter I 120. The water outlet of the flotation tank 310 is connected to the water inlet of the filter II 320. The water outlet of the filter II 320 is connected to the water inlet of the denitrification bed II 330. The filter II 320 is a microfiltration machine with a filter mesh aperture of 400 mesh. The water outlet of the denitrification bed II 330 is connected to the water inlet of the adsorption dephosphorization bed II 340. The denitrification bed II 330 is identical to the denitrification bed I 220, except that the geometric dimensions are 18×6×5m and there are five of them. The adsorption dephosphorization bed II 340 is identical to the adsorption dephosphorization bed I 230, except that the geometric dimensions are 18×6×5m and there are five of them. The effluent from the adsorption dephosphorization bed II 340 meets discharge standards.

[0106] The sludge treatment device includes a sludge thickening tank and a sludge dewatering machine which are interconnected. The sludge thickening tank is used to treat the sludge from the anaerobic sedimentation tank and / or the flotation tank. The concentrated sludge enters the sludge dewatering machine for dehydration treatment.

[0107] (2) The eel farming tail water purification and recycling method adopted in this embodiment is carried out in the above-mentioned eel farming tail water purification and recycling system, and specifically includes the following steps:

[0108] S1. Pretreatment: 10,000 tons / day of eel aquaculture tailwater is discharged into sedimentation tank 110 for sedimentation. In sedimentation tank 110, the sedimentation is separated into a supernatant and a bottom portion of sewage containing solid particles of feces. The supernatant enters filter I 120 to obtain 90% clean water (9,000 tons / day) and 10% sewage (1,000 tons / day). The bottom portion of sewage containing solid particles of feces is collected in a sludge thickening tank;

[0109] S2. Clean water purification and recycling treatment:

[0110] ① Hydrolysis and acidification treatment: The 9,000 tons of clean water obtained in step S1 enters the hydrolysis and acidification tank 210 for hydrolysis and acidification treatment to convert organic nitrogen in the clean water into ammonia nitrogen and organic phosphorus into inorganic phosphate, while removing part of the COD in the clean water;

[0111] ② Denitrification treatment: The clean water after hydrolysis and acidification flows into the denitrification bed I 220. The nitrifying bacteria on the surface of the denitrification filler 222 oxidize the ammonia nitrogen into nitrite and / or nitrate nitrogen. The denitrifying bacteria in the pores of the denitrification filler 222 then reduce the nitrate nitrogen and nitrite to nitrogen gas, thereby removing ammonia nitrogen, nitrite and total nitrogen from the water body.

[0112] ③ Phosphorus removal treatment: The water body after denitrification enters the adsorption phosphorus removal bed I 230, and the inorganic phosphate in the water is adsorbed and removed by the adsorption phosphorus removal filler 232 of the adsorption phosphorus removal bed I 230;

[0113] ④ Biological activation treatment: The clean water after phosphorus removal was mixed and cultured with photosynthetic bacteria, chlorella, diatoms, spirulina culture solution and bacillus culture solution in the biological activation pool for 28 hours to restore the water activity and obtain recyclable effluent. The water quality of the recycle water is shown in Table 3: After hydrolysis, acidification, denitrification, phosphorus removal and biological activation treatment, the ammonia nitrogen in the eel breeding tail water was reduced from ≦6.9mg / L to ≦0.5mg / L, with a removal rate of more than 90%, the nitrite in the water was reduced from ≦1.2mg / L to ≦0.1mg / L, with a removal rate of 91.67%, the total nitrogen in the water was reduced from ≦17.5mg / L to ≦2mg / L, with a removal rate of 88.57%, and the total phosphorus in the water was reduced from ≦1.7mg / L to ≦0.2mg / L;

[0114] S3. Concentrate treatment: The concentrated water obtained in step S1 enters the flotation tank 310, where flocculants and coagulants are added to remove 90-98% of phosphorus and 40-75% of COD in the concentrated water by flotation and slag removal. Cr The concentrated water after flotation enters filter II, where it further removes tiny solid particles from the wastewater and then enters denitrification bed II 330 for denitrification. The denitrified concentrated water enters adsorption phosphorus removal bed II 340, where the total phosphorus in the water is adsorbed by a special phosphorus adsorption filler. The inlet and outlet water quality of the concentrated water is shown in Table 4, with the total phosphorus concentration of the effluent being ≤0.5 mg / L, total nitrogen ≤5 mg / L, ammonia nitrogen ≤1 mg / L, pH 6-9, COD ≤40 mg / L, and suspended solids ≤45 mg / L.

[0115] S4. Sludge treatment: The sludge from the sedimentation anaerobic treatment and flotation treatment is subjected to gravity and filter press treatment to obtain dewatered sludge.

[0116] In this embodiment, the inlet index of the eel farming tail water to be processed, the outlet index of the circulating water, and the inlet and outlet index of the concentrated water are shown in Table 3 and Table 4.

[0117] Table 3 Inlet and outlet indicators of circulating water for eel aquaculture tail water (unit: mg / L)

[0118] Serial number project Water inlet index Circulating water indicators Removal rate (%) 1 SS 200.0 10.0 95.00 2 nitrite 1.2 0.1 91.67 3 <![CDATA[COD Cr ]]> 45.0 10.0 77.78 4 Ammonia nitrogen (as N) 6.9 0.5 92.75 5 Total nitrogen (as N) 17.5 2.0 88.57 6 Total phosphorus (P) 1.7 0.2 88.24 7 Insects and eggs (pieces) 150 0 100.00 8 pH 6～9 6～9 -

[0119] Table 4 Inlet and outlet indicators of eel aquaculture tail water (unit: mg / L)

[0120] Serial number project Concentrated water inlet index Discharge water indicators Removal rate (%) 1 SS 280.0 10.0 96.43 2 <![CDATA[COD Cr ]]> 50.0 10.0 80.00 3 Ammonia nitrogen (as N) 7.0 1.0 85.71 4 Total nitrogen (as N) 17.7 3.2 81.92 5 Total phosphorus (P) 2.7 0.5 81.48 6 Insects and eggs (pieces) 1300 0 100.00 7 pH 6～9 6～9 -

[0121] 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 this 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 purifying and recycling eel aquaculture tail water, characterized in that: The system includes a pre-treatment device, a clean water purification circulation device and a concentrated water treatment device, wherein the pre-treatment device includes a sedimentation tank and a filter I connected in sequence, the clean water purification circulation device includes a hydrolysis acidification tank, a denitrification bed I, an adsorption dephosphorization bed I and a biological activation tank group connected in sequence, and the concentrated water treatment device includes an air flotation tank, a filter II, a denitrification bed II and an adsorption dephosphorization bed II connected in sequence; The clean water outlet of the filter I is communicated with the water inlet of the hydrolysis acidification tank, the concentrated water outlet of the filter I is communicated with the water inlet of the flotation tank, the water outlet of the biological activation pool group is communicated with the eel breeding pond, and the water outlet of the adsorption dephosphorization bed II is communicated with the drain; The denitrification bed I and denitrification bed II are used to remove nitrite, ammonia nitrogen and total nitrogen in water. The denitrification bed I and denitrification bed II each independently include a denitrification tank, a denitrification filler area, 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 includes denitrification filler and a filler support I for supporting the denitrification filler. The denitrification filler area is arranged in the denitrification tank and above the aeration pipe I. The cover plate I is located above the denitrification filler; the adsorption dephosphorization bed I and adsorption dephosphorization bed II each independently include an adsorption dephosphorization tank, an adsorption dephosphorization filler area, an aeration pipe II and a cover plate II. The aeration pipe II is arranged at the bottom of the adsorption dephosphorization tank. The adsorption dephosphorization filler area includes adsorption dephosphorization filler and a filler support II for supporting the adsorption dephosphorization filler. The adsorption dephosphorization filler area is arranged in the adsorption dephosphorization tank and above the aeration pipe II. The cover plate II is located above the adsorption dephosphorization filler.

2. The eel breeding tail water purification and recycling system according to claim 1, characterized in that: The filter mesh of the filter I has a pore size of 5 to 20 μm.

3. The eel breeding tail water purification and recycling system according to claim 1, characterized in that: The filter screen aperture of the filter II is 200 to 600 meshes.

4. The eel breeding tail water purification and recycling system according to claim 1, characterized in that: The denitrification filler has a honeycomb porous structure and is rich in nitrifying bacteria on the surface and denitrifying bacteria in the pores. The average particle size 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%, adsorption capacity 60~65kg / m 3 .

5. The eel breeding tail water purification and recycling system according to claim 1, characterized in that: The adsorption and phosphorus removal filler has a honeycomb porous structure, 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%, adsorption capacity 24~28kg / m 3 .

6. The eel farming tail water purification and recycling system according to claim 1, characterized in that: The biological activation pool group includes a biological activation pool and a photosynthetic bacteria proliferation pool, a chlorella proliferation pool, a diatom proliferation pool, a spirulina proliferation pool, and a bacillus proliferation pool. The water inlet of the biological activation pool is connected to the water outlet of the adsorption and phosphorus removal bed 1, the outlet of the photosynthetic bacteria proliferation pool, the outlet of the chlorella proliferation pool, the outlet of the diatom proliferation pool, the outlet of the spirulina proliferation pool, and the outlet of the bacillus proliferation pool. The water outlet of the biological activation pool is connected to the eel breeding pond.

7. The eel farming tail water purification and recycling system according to claim 1, characterized in that: The system comprises a sludge treatment device, which comprises a sludge thickening tank and a sludge dewatering machine which are communicated with each other. The sludge thickening tank is used to treat sludge from a sedimentation tank and a flotation tank.

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