An intensive modular combined aquaculture tailwater treatment system

Abstract

The present invention provides an intensive modular combined aquaculture tailwater treatment system, comprising a sewage collection tank, a physical filtration device, an electrode-suspended filler coupled biofilter treatment unit, and an air pump microporous aeration tank connected in sequence, wherein the sewage collection tank, the physical filtration device, the electrode-suspended filler coupled biofilter treatment unit, and the air pump microporous aeration tank are all connected to a sludge concentration and dehydration device; the suspended filler in the electrode-suspended filler coupled biofilter treatment unit is arranged in the biofilter, the DC positive and negative electrode array combination is arranged at the upper part of the biofilter, the electric stirring device is arranged at the lower part of the biofilter, the bottom of the biofilter is provided with a sludge hopper, the electric stirring device is arranged above the sludge hopper, and the carbon source supplement device is connected to the biofilter through a pipeline. The present invention has the advantages of high denitrification and phosphorus removal efficiency, small footprint, energy saving, low cost, no secondary pollution, and simple management.

Description

[Technical field]

[0001] The invention relates to an intensive modular combined aquaculture tail water treatment system. [Background technology]

[0002] my country is a major aquaculture country, with aquaculture output accounting for about 68% of the world's aquaculture output, of which pond aquaculture output accounts for about 45%. The total area and output of freshwater pond aquaculture exceed those of seawater pond aquaculture. At present, pond aquaculture tailwater and factory aquaculture tailwater are basically discharged directly without treatment. Since aquaculture tailwater generally contains high concentrations of ammonia nitrogen, total nitrogen, total phosphorus, permanganate index, chemical oxygen demand COD, five-day biochemical oxygen demand BOD5, fecal coliform group and suspended solids, it is easy to cause eutrophication pollution to the surrounding water environment to varying degrees. On the other hand, since the heavy metals in the aquaculture water source must meet the requirements for fishery aquaculture water, and there is basically no excessive heavy metal input during the aquaculture period, the heavy metal concentration in the aquaculture tailwater generally meets environmental protection requirements. In order to protect the ecological environment of water bodies, governments at all levels and society require that the treatment of aquaculture tailwater must be carried out so that the water quality of the discharged water can meet the relevant national environmental protection requirements, such as the Class III water quality standards in the "Freshwater Aquaculture Tailwater Discharge Requirements" (SC / T 9101) and the national "Surface Water Environmental Quality Standards" (GB3838-2002). The current pond aquaculture tailwater or factory aquaculture tailwater treatment technology mainly uses artificial wetland technology, ecological pond technology and comprehensive application of chemical assisted phosphorus removal technology, such as aluminum chloride (PAC) assisted phosphorus removal for nitrogen and phosphorus removal. Although there is a certain effect of nitrogen and phosphorus removal, there are problems such as large land area, low efficiency of nitrogen and phosphorus removal, high operating cost, poor stability of treatment effect, and long-term use of large amounts of chemical agents may cause secondary pollution. Many aquaculture farms have failed to carry out tailwater discharge treatment due to land area restrictions and high treatment costs, polluting the surrounding water environment or facing the problem of forced suspension of production due to non-compliance with environmental protection standards.

[0003] In addition, during electrolysis of existing electrodes, the surface of the anode iron is easily passivated by a dense covering layer formed by oxides, resulting in electrolysis not being able to proceed normally and requiring regular cleaning or replacement, which will cause regular interruptions in production, affecting work efficiency, while also generating new wastewater and increasing costs. [Summary of the invention]

[0004] The technical problem to be solved by the present invention is to provide an intensive modular combined aquaculture tailwater treatment system, which has the advantages of high denitrification and phosphorus removal efficiency, small footprint, energy saving, low cost, no secondary pollution, and easy management.

[0005] The present invention is achieved in that:

[0006] An intensive modular combined aquaculture tailwater treatment system, the tailwater treatment system comprising a sewage collection tank, a physical filtration device, an electrode-suspended filler coupled biofilter treatment unit, an air pump microporous aeration tank and a sludge concentration and dehydration device; the sewage collection tank is connected to the physical filtration device, the physical filtration device is connected to the electrode-suspended filler coupled biofilter treatment unit, the electrode-suspended filler coupled biofilter treatment unit is adjacent to the air pump microporous aeration tank, and the sewage collection tank, the physical filtration device, the electrode-suspended filler coupled biofilter treatment unit, and the air pump microporous aeration tank are all connected to the sludge concentration and dehydration device;

[0007] The electrode-suspended filler coupled biofilter treatment unit comprises a biofilter, a suspended filler, a DC positive and negative electrode array combination, an electric stirring device and a carbon source supplement device, wherein the suspended filler is arranged in the biofilter, the DC positive and negative electrode array combination is arranged at the upper part of the biofilter, the electric stirring device is arranged at the lower part of the biofilter, a sludge hopper is arranged at the bottom of the biofilter, the electric stirring device is arranged above the sludge hopper, and the carbon source supplement device is connected to the biofilter through a pipeline;

[0008] The volume ratio of the suspended filler to the water in the biofilter is 20% to 50%, and the density of the suspended filler is 0.92 to 0.98 g / cm 3 ; The anode in the DC positive and negative electrode array combination is iron, and the cathode is iron, carbon or copper; the speed of the electric stirring device is 100 to 300 r / min.

[0009] Furthermore, the suspended filler is made of high-density polyethylene with a specific surface area greater than 500m 2 / m 3 .

[0010] Furthermore, the spacing between adjacent electrodes of the DC positive and negative electrode array combination is 2-30 cm, and the operating voltage and current are: DC voltage is 12-36 V, and micro-current density is 0.1-1.0 mA / cm 2 .

[0011] Furthermore, the biofilter is a combination of more than two tank bodies connected in series, and a DC positive and negative electrode array combination can be set in part or all of the tank bodies.

[0012] Furthermore, the physical filtering device is an automatic backwashing screen filter, a microfilter or a curved screen.

[0013] Furthermore, an oxygenation microporous aeration pipe is provided at the bottom of the air pump microporous oxygenation tank.

[0014] The present invention has the following advantages:

[0015] The present invention mainly achieves continuous, stable and efficient phosphorus and nitrogen removal, organic matter degradation and suspended solids concentration reduction effects through a series of physical, chemical and microbial effects generated in the biofilter, integrated iron cation phosphate precipitation reaction, iron cation hydrate and its polymer flocculation and precipitation of phosphorus and other particulate matter, nitrification reaction and denitrification reaction. It has the advantages of simple device structure, small amount of sludge production and no secondary pollution. After the aquaculture tail water is treated by the system of the present invention, the nitrogen, phosphorus, permanganate index, chemical oxygen demand COD, five-day biochemical oxygen demand BOD5, pH, dissolved oxygen, fecal coliform group, suspended solids, sulfide and volatile phenol in the discharged water can meet the Class III water quality standards in the "Freshwater Aquaculture Tail Water Discharge Requirements" (SC / T9101) or the national "Surface Water Environmental Quality Standard" (GB3838-2002).

Brief Description of the Drawings

[0016] The present invention will be further described below in conjunction with embodiments with reference to the accompanying drawings.

[0017] Figure 1 It is a schematic diagram of the structure of the present invention.

[0018] Figure 2 It is a schematic diagram of the coordinated structure of the electrode-suspended filler coupling biofilter processing unit and the air pump microporous aeration tank in the present invention. [Specific implementation method]

[0019] See also Figure 1-2 The present invention relates to an intensive modular combined aquaculture tailwater treatment system, the tailwater treatment system comprising a sewage collecting tank 1, a physical filtration device 2, an electrode-suspended filler coupled biological filter treatment unit 3, an air pump microporous aeration tank 4 and a sludge concentration and dehydration device 5; the sewage collecting tank 1 is connected to the physical filtration device 2, the physical filtration device 2 is connected to the electrode-suspended filler coupled biological filter treatment unit 3, the electrode-suspended filler coupled biological filter treatment unit 3 is adjacent to the air pump microporous aeration tank 4, the sewage collecting tank 1, the physical filtration device 2, the electrode-suspended filler coupled biological filter treatment unit 3, the air pump microporous aeration tank 4 are all connected to the sludge concentration and dehydration device 5;

[0020] The electrode-suspended filler coupled biofilter treatment unit 3 comprises a biofilter 31, a suspended filler 32, a DC positive and negative electrode array combination 33, an electric stirring device 34 and a carbon source supplement device 35, wherein the suspended filler 32 is arranged in the biofilter 31, the DC positive and negative electrode array combination 33 is arranged at the upper part of the biofilter 31, the electric stirring device 34 is arranged at the lower part of the biofilter 31, a sludge hopper 36 is arranged at the bottom of the biofilter 31, the electric stirring device 34 is arranged above the sludge hopper 36, and the carbon source supplement device 35 is connected to the biofilter 31 through a pipeline;

[0021] The volume ratio of the suspended filler 32 to the water in the biofilter 31 is 20% to 50%, and the density of the suspended filler 32 is 0.92 to 0.98 g / cm 3 The anode of the DC positive and negative electrode array combination 33 is iron, and the cathode is iron, carbon or copper; the rotation speed of the electric stirring device 34 is 100 to 300 r / min.

[0022] The suspended filler 32 is made of high-density polyethylene with a specific surface area greater than 500m 2 / m 3 .

[0023] The spacing between adjacent electrodes of the DC positive and negative electrode array combination 33 is 2-30 cm, and the operating voltage and current are: DC voltage is 12-36 V, and micro-current density is 0.1-1.0 mA / cm 2 .

[0024] The biofilter 31 is a combination of two or more tank bodies connected in series, and a DC positive and negative electrode array combination 33 can be set on part or all of the tank bodies.

[0025] The physical filtering device 2 is an automatic backwashing screen filter, a microfilter or a curved screen.

[0026] An oxygenation microporous aeration pipe 41 is arranged at the bottom of the air pump microporous aeration tank 4 .

[0027] The working process of the present invention is as follows: after the aquaculture tail water enters the sewage collection tank 1, it is pumped into the physical filtering device 2 by a water pump, and the filtered water enters the electrode-suspended filler coupled biological filter processing unit 3, and the backwash water (≤1.5%) containing large particle materials such as residual bait and feces enters the sludge concentration and dehydration device 5; in the sludge concentration and dehydration device 5, the concentrated and dehydrated sludge is formed into mud cake organic fertilizer and transported out of the system, and the concentrated and filtered water is returned to the sewage collection tank 1; in the electrode-suspended filler coupled biological filter processing unit 3, a sludge hopper 36 is provided at the bottom of the biological filter 31, which can discharge sewage regularly, and the sludge water (≤3%) is discharged into the sludge concentration and dehydration device 5; the anoxic water treated by the electrode-suspended filler coupled biological filter processing unit 3 flows into the air pump microporous aeration tank 4 for moderate aeration, and then the discharged water that meets the environmental protection standards is discharged from the system, and the air pump microporous aeration tank 4 is also provided with a sludge hopper, which can discharge sewage regularly, and the sludge water (≤0.5%) is discharged into the sludge concentration and dehydration device 5.

[0028] The working principle of each device is as follows:

[0029] 1. The sewage collection pool 1 is mainly used to collect the tail water discharged from the breeding pool. More than two submersible pumps (one of which is a spare) are installed in the pool to pump the pool water to the physical filtration device 2.

[0030] 2. The physical filtration device 2 is a physical filtration device such as an automatic backwashing screen filter, a microfilter or an arc screen, which separates large particles in the water and automatically sends backwash water (≤1.5%) containing large particles such as leftover bait and feces into the sludge dewatering and concentration device 5, while the water after being filtered by the screen enters the electrode-suspended filler coupled biological filter treatment unit 3.

[0031] 3. The sludge concentration and dehydration device 5 adopts a sludge filter press or sets up a filter layer drying tank facility to form a mud cake (organic fertilizer) from the concentrated and dehydrated sludge and transport it out of the system, and the filtered water returns to the sewage collection tank 1.

[0032] 4. The air pump microporous aeration tank 4 is adjacent to the biofilter 31 of the electrode-suspended filler coupled biofilter treatment unit 3. The anoxic water treated by the electrode-suspended filler coupled biofilter treatment unit 3 flows into the air pump microporous aeration tank 4. An oxygenation microporous aeration pipe 41 is arranged at the bottom of the water body of the air pump microporous aeration tank 4. The oxygenation microporous aeration pipe 41 is connected to the air pump outside the pool through a pipeline, and air is input into the oxygenation microporous aeration pipe to oxygenate the pool water.

[0033] 5. The working principle of the electrode-suspended filler coupled biofilter treatment unit 3 is as follows:

[0034] (1) Due to the DC electric field of the DC anode and cathode electrode array combination 33, the iron (anode) generates a large amount of iron cations, and a large amount of Fe 2+ and Fe 3+ It reacts with the phosphate in the aquaculture tail water to form granular, insoluble substances that settle in the bottom sludge hopper 36 of the biological filter 31; at the same time, the iron cation undergoes a series of hydrolysis and polymerization reactions, Fe 2+ and Fe 3+ and their hydrates such as ferric hydroxide have strong flocculation and precipitation effects on phosphorus, and can also generate polymers with adsorption and condensation effects, such as some Fe 3+ Hydrolysis produces [Fe2(OH)2] 4+ 、[Fe3(OH)4] 5+ 、[Fe5(OH)9] 6+ The polynuclear hydroxyl complexes can act as flocculants and can aggregate with some suspended matter (including suspended phosphorus, including biological phosphorus and insoluble phosphate particles), particulate matter and electrolytes in the aquaculture tail water, and settle in the sludge hopper 36 at the bottom of the biological filter 31.

[0035] (2) The dissolved oxygen contained in the aquaculture tail water and the oxygen generated by the electrolysis of water by the iron anode can provide the dissolved oxygen required for the nitrification reaction for a large number of nitrite and nitrifying bacteria in the biofilm attached to the suspended filler 32, so that ammonia nitrogen is converted into nitrite nitrogen and nitrate nitrogen. Therefore, there is no need to set up an air pump for oxygenation; at the same time, due to the rapid consumption of dissolved oxygen, the water in the pool, especially the lower layer of the pool water, quickly forms an anoxic or anaerobic water environment, which promotes the denitrification reaction.

[0036] (3) The heterotrophic denitrifying bacteria in the pool use the organic carbon source in the aquaculture water as an electron donor to cause a denitrification reaction, so that the nitrate nitrogen is eventually converted into nitrogen gas through the denitrification reaction and overflows the system to be removed.

[0037] (4) The hydrogen produced by cathode electrolysis of water can serve as an electron donor for hydrogen autotrophic denitrifying bacteria, while the CO2 in the tail water can provide an inorganic carbon source for these autotrophic bacteria, leading to autotrophic denitrification, causing nitrate nitrogen to generate nitrogen through denitrification and overflow the system to be removed.

[0038] In addition, the hydrogen generated by the electrolysis of water can stimulate the growth and metabolism of the autotrophic denitrifying bacteria attached to the surface of the suspended filler 32. At the same time, the redox substances generated by the electrolysis provide a suitable environment for the growth and reproduction of microorganisms, and provide inorganic carbon sources and electron donors for the denitrification process of the autotrophic denitrifying bacteria, further promoting the autotrophic denitrification process, thereby improving the removal of total nitrogen.

[0039] (5) Using the density of the suspended filler 32 (0.92 to 0.98 g / cm 3 ) is close to fresh water, and is easy to form a uniform suspension state in the water body of the biological filter. At the same time, under the continuous slow stirring of the electric stirring device 34 and the flow of water, a fluidized state can be formed, so that the biofilm attached to the suspended filler 32 is easy to continuously flow and contact with the pollutants in the aquaculture wastewater, which not only helps to increase the rate of nitrification and denitrification reactions, but also facilitates the continuous friction between the suspended filler 32 and the water flow and the flow through the electrode surface. The density is 0.92-0.98 g / cm at the same volume. 3 The suspended filler has greater friction and can better remove the oxides on the surface of the (anode) iron, preventing the surface of the (anode) iron from being passivated by the formation of a dense covering layer of oxides, which affects the normal progress of the electrode electrolysis reaction, and effectively solves the passivation problem of the (anode) iron.

[0040] (6) Microcurrent can strengthen the bacteria and other microorganisms in the biofilm on the suspended filler 32, change the permeability of the bacterial cell membrane, and help the enzymes in the bacterial cell membrane to pass through the cell membrane into the wastewater to carry out a series of enzymatic reactions, thereby increasing the contact between the enzymes in the cell membrane and the reaction substrates in the water, thereby enhancing the effect of degrading nitrogen and phosphorus in the aquaculture wastewater to a certain extent; in addition, microcurrent can also directly stimulate and strengthen the activity of extracellular enzymes secreted by certain bacteria, promoting the degradation of nitrogen, phosphorus and other pollutants in the water.

[0041] (7) Since the organic carbon concentration in the aquaculture tail water is generally low and will be consumed soon, in order to promote the heterotrophic denitrification reaction in the pool, a carbon source such as brown sugar is added through the carbon source supplement device 35. An automatic dosing device can be configured to regularly add a certain amount of brown sugar to the solution barrel, start the agitator to dissolve it, and then automatically add a certain amount of brown sugar to the pool through the metering pump through the pipeline to continuously and quickly promote the heterotrophic denitrification reaction.

[0042] Since the reaction rate of heterotrophic denitrification is several times (about 7 times) faster than that of autotrophic denitrification, and the population growth and expansion rate of heterotrophic denitrifying bacteria are higher than that of autotrophic denitrifying bacteria, adding organic carbon sources such as brown sugar can significantly accelerate denitrification.

[0043] The removal rate of TP has a certain positive correlation with the removal rate of TN, that is, when the TN removal effect is good, the TP removal effect is also good. In the present invention, the iron electrode can provide the electrons required for the denitrification reaction, has a certain strengthening effect on denitrification, and promotes NO3 - The decrease in the mass concentration of -N and TN is conducive to promoting the biological phosphorus removal of polyphosphate bacteria in the filler biofilm and in the water body, and synergistically promoting the removal of TP. In addition, the supplementary carbon source efficient denitrification device used in the present invention greatly promotes the continuous progress of denitrification and promotes NO3 - -N and TN mass concentrations decreased. The continuous deep removal of TP concentration was promoted synergistically. Therefore, the electrode-suspended filler coupling technology of the present invention is integrated with the carbon source supplementation technology to efficiently promote denitrification, and they work together to improve the efficiency and removal rate of nitrogen and phosphorus removal.

[0044] The present invention is further described below in conjunction with specific embodiments.

[0045] Applying the above method and device, an intensive modular combined aquaculture tailwater discharge treatment system was constructed to treat the tailwater from eel ponds and factory aquaculture. The treated effluent water quality meets the standards. The monitoring results are as follows:

[0046]

[0047]

[0048] Note: Influent refers to aquaculture tail water, and effluent refers to the discharged water after being treated by the treatment system.

[0049] In summary, the present invention mainly achieves continuous, stable and efficient phosphorus and nitrogen removal, organic matter degradation and reduction of suspended solids concentration through a series of physical, chemical and microbial effects generated in the biofilter, integrated iron cation phosphate precipitation reaction, iron cation hydrate and its polymer flocculation precipitation effect on phosphorus and other particulate matter, nitrification reaction and denitrification reaction. It can also prevent the passivation of the anode iron surface due to the attachment of oxides, ensure the normal progress of the electrode electrolysis reaction, and improve the efficiency of aquaculture wastewater treatment. It has the advantages of simple device structure, small amount of sludge production and no secondary pollution. The small amount of precipitated sludge produced can be removed from the system by regular sewage discharge.

[0050] The aquaculture tail water discharged after being treated by the treatment system constructed by the present invention has ammonia nitrogen, total nitrogen, total phosphorus, permanganate index, chemical oxygen demand COD, five-day biochemical oxygen demand BOD5, pH, dissolved oxygen, fecal coliform group, suspended solids, sulfide and volatile phenol, etc., which all meet the Class III water quality standards in the national "Surface Water Environmental Quality Standard" (GB3838-2002), and some even meet the Class II water quality standards. It also meets the first-level discharge standards specified in the "Freshwater Aquaculture Tail Water Discharge Requirements" (SC / T 9101).

[0051] Although the specific implementation modes of the present invention are described above, those skilled in the art should understand that the specific implementation modes described are only illustrative and are not intended to limit the scope of the present invention. Equivalent modifications and changes made by those skilled in the art in accordance with the spirit of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. An intensive modular combined aquaculture tailwater treatment system, characterized by: The tailwater treatment system comprises a sewage collecting tank, a physical filtration device, an electrode-suspended filler coupled biofilter processing unit, an air pump microporous aeration tank and a sludge concentration and dehydration device; the sewage collecting tank is connected to the physical filtration device, the physical filtration device is connected to the electrode-suspended filler coupled biofilter processing unit, the electrode-suspended filler coupled biofilter processing unit is adjacent to the air pump microporous aeration tank, and the sewage collecting tank, the physical filtration device, the electrode-suspended filler coupled biofilter processing unit, and the air pump microporous aeration tank are all connected to the sludge concentration and dehydration device; The electrode-suspended filler coupled biofilter treatment unit comprises a biofilter, a suspended filler, a DC positive and negative electrode array combination, an electric stirring device and a carbon source supplement device, wherein the suspended filler is arranged in the biofilter, the DC positive and negative electrode array combination is arranged at the upper part of the biofilter, the electric stirring device is arranged at the lower part of the biofilter, a sludge hopper is arranged at the bottom of the biofilter, the electric stirring device is arranged above the sludge hopper, and the carbon source supplement device is connected to the biofilter through a pipeline; The volume ratio of the suspended filler to the water in the biofilter is 20% to 50%, and the density of the suspended filler is 0.92 to 0.98 g / cm 3 The suspended filler forms a uniform suspension in the water of the biofilter. At the same time, under the continuous slow stirring of the electric stirring device and the flow of water, a fluidized state is formed. The suspended filler and the water flow continuously rub against and flow through the electrode surface to remove the oxide on the surface of the anode iron. The anode of the DC cathode electrode array combination is iron, and the cathode is iron, carbon or copper; the spacing between adjacent electrodes of the DC cathode electrode array combination is 2-30 cm, and the operating voltage and current are: DC voltage is 12-36 V, and micro-current density is 0.1-1.0 mA / cm 2 ; The speed of the electric stirring device is 100~300r / min; Microcurrent can strengthen the bacterial microorganisms in the biofilm on the suspended filler, change the permeability of the bacterial cell membrane, and allow the enzymes in the bacterial cell membrane to pass through the cell membrane into the wastewater for a series of enzymatic reactions, increasing the contact between the enzymes in the cell membrane and the reaction substrates in the water, thereby enhancing the effect of degrading nitrogen and phosphorus in aquaculture wastewater; in addition, microcurrent directly stimulates the activity of extracellular enzymes secreted by strengthened bacteria, promoting the degradation of nitrogen, phosphorus and other pollutants in the water.

2. The intensive modular combined aquaculture tailwater treatment system according to claim 1, characterized in that: The suspended filler is made of high-density polyethylene with a specific surface area greater than 500m 2 / m 3 .

3. The intensive modular combined aquaculture tailwater treatment system according to claim 1, characterized in that: The biological filter is a combination of more than two tank bodies connected in series, and a direct current positive and negative electrode array combination can be set in part or all of the tank bodies.

4. The intensive modular combined aquaculture tailwater treatment system according to claim 1, characterized in that: The physical filtering device is an automatic backwashing screen filter, a microfilter or a curved screen.

5. The intensive modular combined aquaculture tailwater treatment system according to claim 1, characterized in that: An oxygenation microporous aeration pipe is arranged at the bottom of the air pump microporous oxygenation tank.

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