Method and device for purifying water for circulating aquaculture of fishpond

Abstract

The invention relates to the technical field of sewage treatment, and provides a method and a device for purifying water for circulating aquaculture of a fishpond, which adopt an aerobic and anaerobic combined biological filter bed-ceramic membrane combined technology, have the functions of filtration, biological adsorption and the like, improve the removal efficiency of harmful substances in aquaculture tail water, maintain organic matters in effluent and improve the quality of the aquaculture tail water. The pollution to the environment is reduced, and the requirements of fish culture are met; the combined biological filter bed is provided with the trickling filter layer, the aerobic layer and the anaerobic layer from top to bottom, and the gap is formed between the trickling filter layer and the aerobic layer, so that additional aeration devices such as an air blower are reduced in a natural aeration manner, and the equipment cost and the operation cost are further reduced. And the dissolved oxygen concentration of the effluent is higher than 7mg / L and meets the growth standard of fishes, and further reoxygenation treatment is not needed during recycling, so that the aeration cost is greatly saved.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and in particular to a method and a device for purifying water for circulating aquaculture in fish ponds. Background Art

[0002] The high-density aquaculture method in fish ponds causes a large amount of leftover bait and excrement to enter the water body, leading to an increasingly serious problem of aquaculture tailwater pollution. The management and recycling of aquaculture tailwater has become a key issue restricting the sustainable development of aquaculture in China.

[0003] The organic matter in the water is conducive to the growth of beneficial algae in the fish pond. On the one hand, sufficient algae can provide sufficient dissolved oxygen for the water body, and on the other hand, sufficient algae can produce sufficient zooplankton, which are all natural baits for fish. The digestion and metabolism of fish feed must rely on dissolved oxygen in the water. Insufficient dissolved oxygen will lead to a decrease in fish feed intake, and nitrates and sulfates will be reduced to toxic nitrites, ammonium ions, and sulfur ions, which are not conducive to the growth of fish. Ammonia nitrogen, nitrite nitrogen, and bacteria in the water will affect the growth of fish. Therefore, the treated water quality should maintain a certain organic matter concentration and dissolved oxygen, and at the same time, the removal effect of ammonia nitrogen, nitrite nitrogen, and bacteria should be strengthened, which is conducive to the reuse of aquaculture water.

[0004] The research on ceramic membrane bioreactors mainly focuses on the treatment effects of campus domestic sewage, hospital wastewater containing drugs, industrial wastewater, etc., but there are still few reports on the treatment of aquaculture tailwater. However, unlike industrial and domestic sewage, the pollutant composition of aquaculture sewage is simple and the concentration is low, and the requirements for recycled water quality are high. The existing purification devices for treating domestic sewage and industrial sewage are not suitable for the deep purification of aquaculture sewage. Therefore, it is urgent to develop a treatment system that targets the water quality characteristics and purification requirements of aquaculture. Summary of the invention

[0005] The present invention aims to solve at least one of the above technical problems and provide a method and device for purifying circulating water for aquaculture in fish ponds. The treated water can maintain a certain organic matter concentration and dissolved oxygen, and has a good removal effect on ammonia nitrogen, nitrite nitrogen and bacteria. The principle and operation are simple, and the reuse of aquaculture water is realized. The purpose of the present invention is achieved based on the following technical solutions.

[0006] One aspect of the present invention provides a method for purifying water for circulating aquaculture in fish ponds, comprising the following steps:

[0007] S1. Pump the fish pond sewage into the fully automatic backwash filter to filter and remove insoluble impurities;

[0008] S2. Sending the filtered sewage into a biofilter by spraying, wherein the biofilter is provided with a trickling layer, an aerobic layer and an anaerobic layer from top to bottom, wherein the trickling layer is used to further remove insoluble impurities in the sewage, and the aerobic layer and the anaerobic layer are built with porous biological fillers inoculated with microorganisms for further removing ammonia nitrogen, nitrite nitrogen and insoluble impurities in the sewage, and a gap is provided between the trickling layer and the aerobic layer for aeration of the sewage; the filtered sewage is treated in turn by the trickling layer, the aerobic layer and the anaerobic layer, and the treated water flows out from the outlet of the anaerobic layer;

[0009] S3, the treated water enters the intermediate water tank for storage;

[0010] S4. When the water in the intermediate pool reaches a certain amount, the water is sent to the ceramic membrane unit for fine filtration and finally enters the fish pond for reuse.

[0011] The tail water of fish pond aquaculture is first filtered by a fully automatic backwash filter to remove insoluble impurities. The fully automatic backwash can prevent the filter from clogging. The filtered sewage is sent to the trickling filter layer by spraying. The purpose of spraying is to evenly distribute water and relieve the clogging of the trickling filter layer. The trickling filter layer can further remove insoluble impurities in the sewage. A gap is set between the trickling filter layer and the aerobic layer, and the sewage is aerated and oxygenated by natural aeration. There is no need to set up additional aeration devices such as blowers, thereby reducing equipment costs and operating costs. The sewage passes through the aerobic layer and the anaerobic layer under the action of gravity flow, and ammonia nitrogen and nitrite nitrogen in the sewage are removed to further remove insoluble impurities. The water treated by the combined biological filter bed is further finely filtered by a ceramic membrane unit to remove bacteria in the sewage. The present invention adopts aerobic anaerobic combined biological filter bed-ceramic membrane combined technology, which has functions such as filtration and biological adsorption, improves the removal efficiency of harmful substances in aquaculture tail water and maintains organic matter in the effluent, which is conducive to reducing pollution to the environment and meeting the needs of fish farming.

[0012] As a preferred embodiment of the present invention, the self-priming pump in step S1 is controlled by a first liquid level controller. When the water level in the biofilter is at a set low level, the self-priming pump is started, and when the water level in the biofilter is at a set high level, the self-priming pump is shut down.

[0013] As a preferred embodiment of the present invention, the porous biological filler is inoculated with microorganisms in step S2 as follows: filter materials are provided on the aerobic layer and the anaerobic layer, and microorganisms are inoculated on the filter materials of the aerobic layer and the anaerobic layer by spraying.

[0014] As a preferred embodiment of the present invention, after the aerobic layer and the anaerobic layer are inoculated with microorganisms, fish pond water that has passed through the filter is introduced every day for 20-45 days to ensure that more microorganisms are adsorbed and fixed on the filter material, and then the filtered sewage is sent to the biological filter tank for treatment by spraying.

[0015] As a preferred embodiment of the present invention, the gap between the trickling filter layer and the aerobic layer in step S2 is 5-20 cm high, preferably 10-15 cm high, and the natural aeration is more effective in oxygenating the sewage, and the equipment cost and operation cost are further reduced; and / or

[0016] The water outlet of the anaerobic layer is arranged at a position higher than the top of the anaerobic layer, so that the anaerobic layer is always kept flooded by overflow, thereby improving the removal effect of anaerobic microorganisms on harmful substances such as ammonia nitrogen and nitrite nitrogen in water; and / or

[0017] The sewage flow rate in the biofilter in step S2 is 1-5m 3 / h. If the inlet flow rate is too large, it will impact the biofilm formed after the aerobic layer and anaerobic layer are inoculated with microorganisms. If the inlet flow rate is too small, insufficient nutrition will cause the biofilm to fall off.

[0018] As a preferred embodiment of the present invention, the water inlet of the biological filter described in step S2 is provided with an inlet electric valve, the water outlet is provided with an outlet electric valve, the aerobic layer is provided with a second liquid level controller, and the full-automatic backwash filter is provided with a lift pump, and the operation of the lift pump, the inlet electric valve and the outlet electric valve is controlled by the second liquid level controller; when the water level of the aerobic layer in the biological filter is at a set low level, the outlet electric valve is closed, the inlet electric valve is opened, and the lift pump sends the filtered sewage into the biological filter; when the water level of the aerobic layer is at a set high level, the lift pump stops sending sewage, and at the same time the inlet electric valve is closed, the outlet electric valve is opened, and the treated water is sent to the intermediate water tank.

[0019] As a preferred embodiment of the present invention, the biofilter is provided with two sets, which are operated alternately. The combined biofilter beds are connected in parallel and operated alternately and intermittently, which can improve the activity of nitrifying bacteria and denitrifying bacteria in the biofilter beds.

[0020] As a preferred embodiment of the present invention, the intermediate water tank in step S3 is provided with a submersible pump and a third liquid level controller, the ceramic membrane unit in step S4 is provided with a fourth liquid level controller, the submersible pump is controlled jointly by the third liquid level controller and the fourth liquid level controller, the submersible pump runs when the liquid level of the intermediate water tank is at a set high level and the liquid level of the ceramic membrane unit is at a set low level, and the submersible pump is shut down when the liquid level of the ceramic membrane unit is at a set high level.

[0021] As a preferred embodiment of the present invention, a plate-type ceramic membrane is provided in the ceramic membrane unit in step S4, and the plate-type ceramic membrane is a nano-ceramic membrane.

[0022] As a preferred embodiment of the present invention, the ceramic membrane unit in step S4 can be backwashed to prevent clogging. The backwashing cycle is 5-30 minutes, and the backwashing flow rate is 5-30m 3 / h, backwash time is 10-45s.

[0023] Another aspect of the present invention provides a fish pond circulating water aquaculture water purification device, including a fully automatic backwash filter, a biological filter, an intermediate water tank and a ceramic membrane unit;

[0024] The fish pond is provided with a self-priming pump for sending the fish pond sewage into the fully automatic backwashing filter, and the fully automatic backwashing filter is provided with a lifting pump for sending the filtered sewage into the biological filter tank;

[0025] The biofilter tank includes a spray head, a trickling filter layer, an aerobic layer and an anaerobic layer from top to bottom, wherein the spray head is used to deliver the filtered sewage to the trickling filter layer by spraying, the trickling filter layer is used to evenly distribute the sewage to the aerobic layer, the aerobic layer and the anaerobic layer are built with porous biological fillers inoculated with microorganisms, a gap is set between the trickling filter layer and the aerobic layer, and the anaerobic layer is provided with a water outlet;

[0026] A submersible pump is provided in the intermediate water tank for delivering water into the ceramic membrane unit;

[0027] The ceramic membrane unit is used to finely filter the water and then send it to the fish pond for reuse.

[0028] The present invention can achieve at least one of the following beneficial effects:

[0029] The present invention adopts aerobic anaerobic combined biofilter bed-ceramic membrane technology, which has the functions of filtration and biosorption, improves the removal efficiency of harmful substances in aquaculture tail water and maintains organic matter in the effluent, which is beneficial to reduce pollution to the environment and meet the needs of fish farming. The dissolved oxygen concentration of the effluent is higher than 7mg / L, which meets the fish growth standard. No further reoxygenation treatment is required when it is reused, which greatly saves aeration costs.

[0030] A gap is set between the trickling filter layer and the aerobic layer, and natural aeration is used to reduce the need for additional aeration devices such as blowers, thereby reducing equipment costs and operating costs. In addition, the combined biological filter beds are used in parallel for intermittent operation to increase the activity of nitrifying bacteria and denitrifying bacteria, which is beneficial to the degradation of harmful substances such as ammonia nitrogen and nitrite nitrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The process flow chart of the preferred embodiment of the present invention is as follows;

[0032] Figure 2 A schematic diagram of a device according to a preferred embodiment of the present invention;

[0033] Description of the drawings: 1 fully automatic backwash filter, 11 lifting pump, 2 biological filter, 21 spray head, 22 trickling layer, 23 aerobic layer, 24 anaerobic layer, 25 gap, 26 water outlet electric valve, 27 second liquid level controller, 28 water inlet electric valve, 231 first porous biological filler, 241 second porous biological filler, 242 water outlet, 3 intermediate water tank, 31 submersible pump, 32 third liquid level controller, 4 ceramic membrane unit, 41 fourth liquid level controller, 42 plate ceramic membrane, 5 fish pond, 51 self-priming pump, 52 first liquid level controller. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Example 1

[0036] like Figure 2 As shown, a preferred embodiment of the present invention provides a fish pond circulating water aquaculture water purification device, including a full-automatic backwash filter 1, a biological filter 2, an intermediate water tank 3 and a ceramic membrane unit 4, wherein:

[0037] A self-priming pump 51 is provided in the fish pond 5 for sending the fish pond sewage into the fully automatic backwashing filter 1, and the fully automatic backwashing filter is provided with a lifting pump 11 for sending the filtered sewage into the biological filter 2;

[0038] The biological filter 2 includes a spray head 21, a trickling filter layer 22, an aerobic layer 23 and an anaerobic layer 24 from top to bottom. The spray head 21 is used to send the filtered sewage to the trickling filter layer 22 by spraying to evenly distribute water. The trickling filter layer 22 is used to further remove insoluble impurities in the sewage. The aerobic layer 23 is built with a first porous biological filler 231 inoculated with microorganisms, and the anaerobic layer 24 is built with a second porous biological filler 241 inoculated with microorganisms. A gap 25 is set between the trickling filter layer 22 and the aerobic layer 23, and the anaerobic layer 24 is provided with a water outlet 242.

[0039] A submersible pump 31 is provided in the intermediate water tank 3 for delivering water into the ceramic membrane unit 4;

[0040] The ceramic membrane unit 4 is used to finely filter the water and then send it to the fish pond for reuse.

[0041] In this embodiment, a first liquid level controller 52 is provided in the fish pond 5, and the self-priming pump 51 is controlled by the first liquid level controller 52. When the water level of the biological filter is at a set low level, the self-priming pump 51 is started, and when the water level of the biological filter is at a set high level, the self-priming pump 51 is shut down.

[0042] In this embodiment, the water inlet of the biofilter 2 is provided with an inlet electric valve 28, the water outlet is provided with an outlet electric valve 26, and the aerobic layer is provided with a second liquid level controller 27. When the water level of the aerobic layer 23 in the biofilter 2 is at a set low level, the outlet electric valve 26 is closed, the inlet electric valve 28 is opened, and the lifting pump 11 sends the filtered sewage into the biofilter 2; when the water level of the aerobic layer 23 in the biofilter is at a set high level, the lifting pump 11 stops sending sewage, and the inlet electric valve 28 is closed, the outlet electric valve 26 is opened, and the treated water is sent from the outlet 242 to the intermediate water tank 3. Preferably, the biofilter 2 is provided with two sets, and the two are operated alternately; the combined biofilter bed is used in parallel to alternately operate intermittently, which can improve the activity of nitrifying bacteria and denitrifying bacteria in the biofilter bed. Take the case where the No. 1 biofilter is running and the No. 2 biofilter is closed as an example: when the No. 1 biofilter water inlet electric valve 28 is opened, sewage enters the No. 1 biofilter, and at this time, the No. 2 biofilter water inlet electric valve 28 is closed and no water enters. The gap between the trickling layer 22 and the aerobic layer 23 is 5-20 cm high, preferably 10-15 cm. Natural aeration has a better effect of oxygenating sewage and reduces equipment cost and operation cost. It is more preferably 10-12 cm. The outlet 242 of the anaerobic layer 24 is set at a position higher than the top of the anaerobic layer 24. The anaerobic layer 24 is always kept flooded by overflow, thereby improving the removal effect of anaerobic microorganisms on harmful substances such as ammonia nitrogen and nitrite nitrogen in water.

[0043] In this embodiment, the intermediate water tank 3 is arranged below the ground, and a submersible pump 31 and a third liquid level controller 32 are arranged therein, and the ceramic membrane unit 4 is provided with a fourth liquid level controller 41. The submersible pump 31 is controlled by the third liquid level controller 32 and the fourth liquid level controller 41. When the liquid level of the intermediate water tank 3 is at a set high level and the liquid level of the ceramic membrane unit 4 is at a set low level, the submersible pump 31 is operated, and when the liquid level of the ceramic membrane unit 4 is at a set high level, the submersible pump 31 is shut down. A plate-type ceramic membrane 42 is arranged in the ceramic membrane unit 4, and the plate-type ceramic membrane 42 is preferably a nano-ceramic membrane. The ceramic membrane unit 4 can be backwashed to prevent clogging.

[0044] Before the device is officially put into operation, the biofilm stage must be carried out first: the porous biological filler 231 of the aerobic layer 23 and the porous biological filler 241 of the anaerobic layer 24 are inoculated with microorganisms in the following manner: filter materials are provided on the aerobic layer 23 and the anaerobic layer 24, and microorganisms are inoculated on the filter materials of the aerobic layer 23 and the anaerobic layer 24 by spraying. After the aerobic layer 23 and the anaerobic layer 24 are inoculated with microorganisms, fish pond water that has passed through the filter is introduced daily for 30 days to allow the microorganisms to be adsorbed and fixed on the filter materials. The following examples are based on the device provided in Example 1.

[0045] Example 2

[0046] like Figure 1 As shown, this embodiment provides a method for purifying water for circulating aquaculture in fish ponds, comprising the following steps:

[0047] When the water level in the biofilter is at the set low level, the self-priming pump 51 is started, and the fish pond sewage enters the fully automatic backwash filter 1 through the self-priming pump 51 for filtration. The water inlet flow rate is 1.5m 3 / h. The filtered sewage enters one of the two sets of biological filters 2 for treatment through the action of the lifting pump 11. When the water level of the biological filter is at a set high level, the self-priming pump 51 is shut down.

[0048] When the water level in the biofilter 2 is at a set low level, the outlet electric valve 26 is closed, and the inlet electric valve 28 is opened. The filtered sewage enters one of the two biofilters 2 through the lift pump 11, and passes through the trickling layer 22, the gap 25 (10 cm high), the aerobic layer 23, and the anaerobic layer 24 from top to bottom through the sprinkler head 21 in a spraying manner, and undergoes biochemical reactions in the first porous biological filler 231 and the second porous biological filler 241. When the water level in the biofilter is at a set high level, the lift pump 11 stops sending sewage, and the inlet electric valve 28 is closed, and the outlet electric valve 26 is opened, and the treated water is sent from the outlet 242 to the intermediate water tank 3 for storage. The two biofilters 2 are controlled by the inlet electric valve 28 and run alternately in a cycle of 12 hours.

[0049] When the liquid level of the intermediate water tank 3 is at a set high level and the liquid level of the ceramic membrane unit 4 is at a set low level, the submersible pump 31 is operated, and the water stored in the intermediate water tank 3 enters the ceramic membrane unit 4 provided with the plate-type ceramic membrane 42 through the submersible pump 31. When the liquid level of the ceramic membrane unit 4 is at a set high level, the submersible pump 31 is shut down. The backwashing cycle of the ceramic membrane unit 4 is 10 minutes, and the backwashing flow rate is 10m 3 / h, time 20s, to prevent clogging. Ceramic membrane unit 4 finely filters the water and then sends it to the fish pond for reuse.

[0050] The effluent after fine filtration is tested. The test items and methods are as follows:

[0051] Permanganate index (CODMn): "Determination of permanganate index of water quality" (GB / T11892-1989);

[0052] Ammonia nitrogen: "Water quality-Determination of ammonia nitrogen-Nessler's reagent spectrophotometric method" (HJ 535-2009);

[0053] Nitrite nitrogen: "Water quality-Determination of nitrite nitrogen-Spectrophotometric method" (GB 7493-1987);

[0054] Total nitrogen: "Water quality-Determination of total nitrogen-Alkaline potassium persulfate digestion ultraviolet spectrophotometry" (HJ 636-2012);

[0055] Total phosphorus: "Water quality-Determination of total phosphorus-Ammonium molybdate spectrophotometric method" (GB / T 11893-1989);

[0056] Suspended matter: "Water quality - Determination of suspended matter by gravimetric method" (GB / T 11901-1989);

[0057] Total bacteria count: "Determination of total bacteria count in water - Plate count method" (HJ 1000-2018);

[0058] Dissolved oxygen in effluent: “Determination of dissolved oxygen in water quality—Electrochemical probe method” (HJ 506-009).

[0059] After monitoring, the effluent COD Mn The removal rates of ammonia nitrogen, nitrite nitrogen, total nitrogen, total phosphorus, suspended solids and total bacteria reached 64.5%, 97%, 91.9%, 53.4%, 53.2%, 100% and 100% respectively, and the dissolved oxygen in the effluent can reach 7.36 mg / L.

[0060] Example 3

[0061] like Figure 1 As shown, this embodiment provides a method for purifying water for circulating aquaculture in fish ponds, comprising the following steps:

[0062] The water level in the biofilter is at the set low level, the self-priming pump 51 is started, and the fish pond sewage enters the fully automatic backwash filter 1 through the self-priming pump 51 for filtration, and the water inlet flow rate is 2.1m 3 / h. The filtered sewage enters one of the two sets of biological filters 2 for treatment through the action of the lifting pump 11. When the water level of the biological filter is at a set high level, the self-priming pump 51 is shut down.

[0063] When the water level in the biofilter 2 is at a set low level, the outlet electric valve 26 is closed, and the inlet electric valve 28 is opened. The filtered sewage enters one of the two biofilters 2 through the lift pump 11, and passes through the trickling layer 22, the gap 25 (10 cm high), the aerobic layer 23, and the anaerobic layer 24 from top to bottom through the sprinkler head 21 in a spraying manner, and undergoes biochemical reactions in the first porous biological filler 231 and the second porous biological filler 241. When the water level in the biofilter is at a set high level, the lift pump 11 stops sending sewage, and the inlet electric valve 28 is closed, and the outlet electric valve 26 is opened, and the treated water is sent from the outlet 242 to the intermediate water tank 3 for storage. The two biofilters 2 are controlled by the inlet electric valve 28 and run alternately in a cycle of 12 hours.

[0064] When the liquid level of the intermediate water tank 3 is at a set high level and the liquid level of the ceramic membrane unit 4 is at a set low level, the submersible pump 31 is operated, and the water stored in the intermediate water tank 3 enters the ceramic membrane unit 4 provided with the plate-type ceramic membrane 42 through the submersible pump 31. When the liquid level of the ceramic membrane unit 4 is at a set high level, the submersible pump 31 is shut down. The backwashing cycle of the ceramic membrane unit 4 is 10 minutes, and the backwashing flow rate is 10m 3 / h, time 20s, to prevent clogging. Ceramic membrane unit 4 finely filters the water and then sends it to the fish pond for reuse.

[0065] The effluent after fine filtration was tested, and the test items and test methods were the same as those in Example 2. After monitoring, the effluent COD Mn The removal rates of ammonia nitrogen, nitrite nitrogen, total nitrogen, total phosphorus, suspended solids and total bacteria reached 67.0%, 78.7%, 78.9%, 72.1%, 66.1%, 100% and 99.6% respectively, and the dissolved oxygen in the effluent can reach 7.08 mg / L.

[0066] Example 4

[0067] like Figure 1 As shown, this embodiment provides a method for purifying water for circulating aquaculture in fish ponds, comprising the following steps:

[0068] When the water level in the biofilter is at the set low level, the self-priming pump 51 is started, and the fish pond sewage enters the fully automatic backwash filter 1 through the self-priming pump 51 for filtration. The water inlet flow rate is 4m 3 / h. The filtered sewage enters one of the two sets of biological filters 2 for treatment through the action of the lifting pump 11. When the water level of the biological filter is at a set high level, the self-priming pump 51 is shut down.

[0069] When the water level in the biofilter 2 is at a set low level, the outlet electric valve 26 is closed, and the inlet electric valve 28 is opened. The filtered sewage enters one of the two biofilters 2 through the lift pump 11, and passes through the trickling layer 22, the gap 25 (12 cm high), the aerobic layer 23, and the anaerobic layer 24 from top to bottom through the sprinkler head 21 in a spraying manner, and undergoes biochemical reactions in the first porous biological filler 231 and the second porous biological filler 241. When the water level in the biofilter is at a set high level, the lift pump 11 stops sending sewage, and the inlet electric valve 28 is closed, and the outlet electric valve 26 is opened, and the treated water is sent from the outlet 242 to the intermediate water tank 3 for storage. The two biofilters 2 are controlled by the inlet electric valve 28 and run alternately in a cycle of 12 hours.

[0070] When the liquid level of the intermediate water tank 3 is at a set high level and the liquid level of the ceramic membrane unit 4 is at a set low level, the submersible pump 31 is operated, and the water stored in the intermediate water tank 3 enters the ceramic membrane unit 4 provided with the plate-type ceramic membrane 42 through the submersible pump 31. When the liquid level of the ceramic membrane unit 4 is at a set high level, the submersible pump 31 is shut down. The backwashing cycle of the ceramic membrane unit 4 is 10 minutes, and the backwashing flow rate is 10m 3 / h, time 20s, to prevent clogging. Ceramic membrane unit 4 finely filters the water and then sends it to the fish pond for reuse.

[0071] The effluent after fine filtration was tested, and the test items and test methods were the same as those in Example 2. After monitoring, the effluent COD Mn The removal rates of ammonia nitrogen, nitrite nitrogen, total nitrogen, total phosphorus, suspended solids and total bacteria reached 47.1%, 77.6%, 100%, 77.6%, 59.3%, 100% and 99.9% respectively, and the dissolved oxygen in the effluent can reach 8.15 mg / L.

[0072] Example 5

[0073] like Figure 1 As shown, this embodiment provides a method for purifying water for circulating aquaculture in fish ponds, comprising the following steps:

[0074] When the water level in the biofilter is at the set low level, the self-priming pump 51 is started, and the fish pond sewage enters the fully automatic backwash filter 1 through the self-priming pump 51 for filtration. The water inlet flow rate is 5m 3 / h. The filtered sewage enters one of the two sets of biological filters 2 for treatment through the action of the lifting pump 11. When the water level of the biological filter is at a set high level, the self-priming pump 51 is shut down.

[0075] When the water level in the biofilter 2 is at a set low level, the outlet electric valve 26 is closed, and the inlet electric valve 28 is opened. The filtered sewage enters one of the two biofilters 2 through the lift pump 11, and passes through the trickling filter layer 22, the gap 25 (8 cm high), the aerobic layer 23, and the anaerobic layer 24 from top to bottom through the sprinkler head 21 in a spraying manner, and undergoes biochemical reactions in the first porous biological filler 231 and the second porous biological filler 241. When the water level in the biofilter is at a set high level, the lift pump 11 stops sending sewage, and the inlet electric valve 28 is closed, and the outlet electric valve 26 is opened, and the treated water is sent from the outlet 242 to the intermediate water tank 3 for storage. The two biofilters 2 are controlled by the inlet electric valve 28 and run alternately in a cycle of 12 hours.

[0076] When the liquid level of the intermediate water tank 3 is at a set high level and the liquid level of the ceramic membrane unit 4 is at a set low level, the submersible pump 31 is operated, and the water stored in the intermediate water tank 3 enters the ceramic membrane unit 4 provided with the plate-type ceramic membrane 42 through the submersible pump 31. When the liquid level of the ceramic membrane unit 4 is at a set high level, the submersible pump 31 is shut down. The backwash cycle of the ceramic membrane unit 4 is 5 minutes, and the backwash flow rate is 15m 3 / h, time 10s, to prevent clogging. Ceramic membrane unit 4 finely filters the water and then sends it to the fish pond for reuse.

[0077] The effluent after fine filtration was tested, and the test items and test methods were the same as those in Example 2. After monitoring, the effluent COD Mn The removal rates of ammonia nitrogen, nitrite nitrogen, total nitrogen, total phosphorus, suspended solids and total bacteria reached 53.3%, 74.1%, 72.0%, 67.6%, 49.3%, 100% and 99.9% respectively, and the dissolved oxygen in the effluent can reach 7.82 mg / L.

[0078] Embodiment 6:

[0079] like Figure 1 As shown, this embodiment provides a method for purifying water for circulating aquaculture in fish ponds, comprising the following steps:

[0080] When the water level in the biofilter is at the set low level, the self-priming pump 51 is started, and the fish pond sewage enters the fully automatic backwash filter 1 through the self-priming pump 51 for filtration. The water inlet flow rate is 3m 3 / h. The filtered sewage enters one of the two sets of biological filters 2 for treatment through the action of the lifting pump 11. When the water level of the biological filter is at a set high level, the self-priming pump 51 is shut down.

[0081] When the water level in the biofilter 2 is at a set low level, the outlet electric valve 26 is closed, and the inlet electric valve 28 is opened. The filtered sewage enters one of the two biofilters 2 through the lift pump 11, and passes through the trickling layer 22, the gap 25 (15 cm high), the aerobic layer 23, and the anaerobic layer 24 from top to bottom through the spray head 21 in a spraying manner, and undergoes biochemical reactions in the first porous biological filler 231 and the second porous biological filler 241. When the water level in the biofilter is at a set high level, the lift pump 11 stops sending sewage, and the inlet electric valve 28 is closed, and the outlet electric valve 26 is opened, and the treated water is sent from the outlet 242 to the intermediate water tank 3 for storage. The two biofilters 2 are controlled by the inlet electric valve 28 and run alternately in a cycle of 12 hours.

[0082] When the liquid level of the intermediate water tank 3 is at a set high level and the liquid level of the ceramic membrane unit 4 is at a set low level, the submersible pump 31 is operated, and the water stored in the intermediate water tank 3 enters the ceramic membrane unit 4 provided with the plate-type ceramic membrane 42 through the submersible pump 31. When the liquid level of the ceramic membrane unit 4 is at a set high level, the submersible pump 31 is shut down. The backwashing cycle of the ceramic membrane unit 4 is 20 minutes, and the backwashing flow rate is 5m 3 / h, time 45s, to prevent clogging. Ceramic membrane unit 4 finely filters the water and then sends it to the fish pond for reuse.

[0083] The effluent after fine filtration was tested, and the test items and test methods were the same as those in Example 2. After monitoring, the effluent COD Mn The removal rates of ammonia nitrogen, nitrite nitrogen, total nitrogen, total phosphorus, suspended solids and total bacteria reached 58.1%, 74.5%, 90.7%, 72.3%, 56.4%, 100% and 100% respectively, and the dissolved oxygen in the effluent water could reach 7.21 mg / L.

[0084] The present invention adopts aerobic anaerobic combined biofilter bed-nano ceramic membrane combined technology, which has the functions of filtration and biological adsorption; a gap is set between the trickling layer and the aerobic layer, and the additional aeration device such as the blower is reduced by natural aeration, thereby reducing equipment cost and operation cost. In addition, the combined biofilter bed is intermittently operated in parallel to improve the activity of nitrifying bacteria and denitrifying bacteria, which is beneficial to the degradation of harmful substances such as ammonia nitrogen and nitrite nitrogen. The present invention improves the removal efficiency of harmful substances in aquaculture tail water and maintains organic matter in the effluent, which is beneficial to reducing pollution to the environment and meeting the needs of fish farming. The effluent dissolved oxygen concentration is higher than 7 mg / L, which meets the fish growth standard. No further reoxygenation treatment is required during reuse, which greatly saves aeration costs.

[0085] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for purifying water for circulating water aquaculture in fish ponds, characterized in that: The following steps are involved: S1. Send the fish pond sewage into the fully automatic backwash filter through a self-priming pump to filter and remove insoluble impurities; S2. Sending the filtered sewage into a biofilter by spraying, wherein the biofilter is provided with a trickling layer, an aerobic layer and an anaerobic layer from top to bottom, wherein the trickling layer is used to further remove insoluble impurities in the sewage, and the aerobic layer and the anaerobic layer are built with porous biological fillers inoculated with microorganisms for further removing ammonia nitrogen, nitrite nitrogen and insoluble impurities in the sewage, and a gap is provided between the trickling layer and the aerobic layer for aeration and oxygenation of the sewage by natural aeration; the filtered sewage is treated in turn by the trickling layer, the aerobic layer and the anaerobic layer, and the treated water flows out from the outlet of the anaerobic layer; S3, the treated water enters the intermediate water tank for storage; S4. When the water in the intermediate pool reaches a certain amount, the water is sent to the ceramic membrane unit for fine filtration and finally enters the fish pond for reuse.

2. A method for purifying water for circulating aquaculture in fish ponds according to claim 1, characterized in that: The self-priming pump in step S1 is controlled by the first liquid level controller. When the water level in the biofilter is at a set low level, the self-priming pump is started, and when the water level in the biofilter is at a set high level, the self-priming pump is shut down.

3. A method for purifying water for circulating aquaculture in fish ponds according to claim 2, characterized in that: The porous biological filler is inoculated with microorganisms in step S2 as follows: filter materials are provided on the aerobic layer and the anaerobic layer, and microorganisms are inoculated on the filter materials of the aerobic layer and the anaerobic layer by spraying.

4. A method for purifying water for circulating aquaculture in fish ponds according to claim 3, characterized in that: After the aerobic layer and the anaerobic layer are inoculated with microorganisms, fish pond water that has passed through the filter is introduced every day for 20-45 days to allow the microorganisms to be adsorbed and fixed on the filter material. The filtered sewage is then sent to the biofilter for treatment by spraying.

5. A method for purifying water for circulating aquaculture in fish ponds according to claim 1, characterized in that: The gap between the trickling filter layer and the aerobic layer in step S2 is 5-20 cm high; and / or The water outlet of the anaerobic layer is arranged at a position higher than the top of the anaerobic layer, so that the anaerobic layer is always kept in a flooded state through overflow; and / or The sewage flow rate in the biofilter is 1-5m 3 / h; and / or The water inlet of the biological filter is provided with an inlet electric valve, the water outlet is provided with an outlet electric valve, the aerobic layer is provided with a second liquid level controller, and the full-automatic backwash filter is provided with a lift pump, and the operation of the lift pump, the inlet electric valve and the outlet electric valve is controlled by the second liquid level controller; when the water level of the aerobic layer in the biological filter is at a set low level, the outlet electric valve is closed, the inlet electric valve is opened, and the lift pump sends the filtered sewage into the biological filter; when the water level of the aerobic layer is at a set high level, the lift pump stops sending sewage, and at the same time the inlet electric valve is closed, the outlet electric valve is opened, and the treated water is sent to the intermediate water tank.

6. A method for purifying water for circulating aquaculture in fish ponds according to claim 1, characterized in that: In step S2, two sets of biological filters are provided, and the two sets are operated alternately.

7. A method for purifying water for circulating aquaculture in fish ponds according to claim 1, characterized in that: The intermediate water tank in step S3 is provided with a submersible pump and a third liquid level controller, and the ceramic membrane unit in step S4 is provided with a fourth liquid level controller. The submersible pump is controlled jointly by the third liquid level controller and the fourth liquid level controller. The submersible pump runs when the liquid level of the intermediate water tank is at a set high level and the liquid level of the ceramic membrane unit is at a set low level, and the submersible pump is shut down when the liquid level of the ceramic membrane unit is at a set high level.

8. A method for purifying water for circulating aquaculture in fish ponds according to claim 1, characterized in that: In step S4, a plate-type ceramic membrane is provided in the ceramic membrane unit, and the plate-type ceramic membrane is a nano-ceramic membrane.

9. A method for purifying water for circulating aquaculture in fish ponds according to claim 1, characterized in that: The ceramic membrane unit in step S4 can be backwashed, the backwashing cycle is 5-30 minutes, and the backwashing flow rate is 5-30m 3 / h, backwash time is 10-45s.

10. A water purification device for circulating water aquaculture in fish ponds, characterized in that: It includes fully automatic backwash filter, biofilter, intermediate water tank and ceramic membrane unit; The fish pond is provided with a self-priming pump for sending the fish pond sewage into the fully automatic backwashing filter, and the fully automatic backwashing filter is provided with a lifting pump for sending the filtered sewage into the biological filter tank; The biofilter tank includes a spray head, a trickling filter layer, an aerobic layer and an anaerobic layer from top to bottom, wherein the spray head is used to deliver the filtered sewage to the trickling filter layer by spraying, the trickling filter layer is used to evenly distribute the sewage to the aerobic layer, the aerobic layer and the anaerobic layer are built with porous biological fillers inoculated with microorganisms, a gap is set between the trickling filter layer and the aerobic layer, and the anaerobic layer is provided with a water outlet; A submersible pump is provided in the intermediate water tank for delivering water into the ceramic membrane unit; The ceramic membrane unit is used to finely filter the water and then send it to the fish pond for reuse.

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